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eafb369a5a
llvm-mirror/lib/Analysis/ValueTracking.cpp
Philip Reames eafb369a5a Plumb TLI through isSafeToExecuteUnconditionally [NFC] 
Split from D95815 to reduce patch size.  Isn't (yet) used for anything, only the client side is wired up.
2021-03-24 17:52:04 -07:00

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//===- ValueTracking.cpp - Walk computations to compute properties --------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains routines that help analyze properties that chains of
// computations have.
//
//===----------------------------------------------------------------------===//
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumeBundleQueries.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/GuardUtils.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/Loads.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/IR/Argument.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GetElementPtrTypeIterator.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/IntrinsicsAArch64.h"
#include "llvm/IR/IntrinsicsX86.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/User.h"
#include "llvm/IR/Value.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/KnownBits.h"
#include "llvm/Support/MathExtras.h"
#include <algorithm>
#include <array>
#include <cassert>
#include <cstdint>
#include <iterator>
#include <utility>
using namespace llvm;
using namespace llvm::PatternMatch;
// Controls the number of uses of the value searched for possible
// dominating comparisons.
static cl::opt<unsigned> DomConditionsMaxUses("dom-conditions-max-uses",
cl::Hidden, cl::init(20));
/// Returns the bitwidth of the given scalar or pointer type. For vector types,
/// returns the element type's bitwidth.
static unsigned getBitWidth(Type *Ty, const DataLayout &DL) {
if (unsigned BitWidth = Ty->getScalarSizeInBits())
return BitWidth;
return DL.getPointerTypeSizeInBits(Ty);
}
namespace {
// Simplifying using an assume can only be done in a particular control-flow
// context (the context instruction provides that context). If an assume and
// the context instruction are not in the same block then the DT helps in
// figuring out if we can use it.
struct Query {
const DataLayout &DL;
AssumptionCache *AC;
const Instruction *CxtI;
const DominatorTree *DT;
// Unlike the other analyses, this may be a nullptr because not all clients
// provide it currently.
OptimizationRemarkEmitter *ORE;
/// Set of assumptions that should be excluded from further queries.
/// This is because of the potential for mutual recursion to cause
/// computeKnownBits to repeatedly visit the same assume intrinsic. The
/// classic case of this is assume(x = y), which will attempt to determine
/// bits in x from bits in y, which will attempt to determine bits in y from
/// bits in x, etc. Regarding the mutual recursion, computeKnownBits can call
/// isKnownNonZero, which calls computeKnownBits and isKnownToBeAPowerOfTwo
/// (all of which can call computeKnownBits), and so on.
std::array<const Value *, MaxAnalysisRecursionDepth> Excluded;
/// If true, it is safe to use metadata during simplification.
InstrInfoQuery IIQ;
unsigned NumExcluded = 0;
Query(const DataLayout &DL, AssumptionCache *AC, const Instruction *CxtI,
const DominatorTree *DT, bool UseInstrInfo,
OptimizationRemarkEmitter *ORE = nullptr)
: DL(DL), AC(AC), CxtI(CxtI), DT(DT), ORE(ORE), IIQ(UseInstrInfo) {}
Query(const Query &Q, const Value *NewExcl)
: DL(Q.DL), AC(Q.AC), CxtI(Q.CxtI), DT(Q.DT), ORE(Q.ORE), IIQ(Q.IIQ),
NumExcluded(Q.NumExcluded) {
Excluded = Q.Excluded;
Excluded[NumExcluded++] = NewExcl;
assert(NumExcluded <= Excluded.size());
}
bool isExcluded(const Value *Value) const {
if (NumExcluded == 0)
return false;
auto End = Excluded.begin() + NumExcluded;
return std::find(Excluded.begin(), End, Value) != End;
}
};
} // end anonymous namespace
// Given the provided Value and, potentially, a context instruction, return
// the preferred context instruction (if any).
static const Instruction *safeCxtI(const Value *V, const Instruction *CxtI) {
// If we've been provided with a context instruction, then use that (provided
// it has been inserted).
if (CxtI && CxtI->getParent())
return CxtI;
// If the value is really an already-inserted instruction, then use that.
CxtI = dyn_cast<Instruction>(V);
if (CxtI && CxtI->getParent())
return CxtI;
return nullptr;
}
static const Instruction *safeCxtI(const Value *V1, const Value *V2, const Instruction *CxtI) {
// If we've been provided with a context instruction, then use that (provided
// it has been inserted).
if (CxtI && CxtI->getParent())
return CxtI;
// If the value is really an already-inserted instruction, then use that.
CxtI = dyn_cast<Instruction>(V1);
if (CxtI && CxtI->getParent())
return CxtI;
CxtI = dyn_cast<Instruction>(V2);
if (CxtI && CxtI->getParent())
return CxtI;
return nullptr;
}
static bool getShuffleDemandedElts(const ShuffleVectorInst *Shuf,
const APInt &DemandedElts,
APInt &DemandedLHS, APInt &DemandedRHS) {
// The length of scalable vectors is unknown at compile time, thus we
// cannot check their values
if (isa<ScalableVectorType>(Shuf->getType()))
return false;
int NumElts =
cast<FixedVectorType>(Shuf->getOperand(0)->getType())->getNumElements();
int NumMaskElts = cast<FixedVectorType>(Shuf->getType())->getNumElements();
DemandedLHS = DemandedRHS = APInt::getNullValue(NumElts);
if (DemandedElts.isNullValue())
return true;
// Simple case of a shuffle with zeroinitializer.
if (all_of(Shuf->getShuffleMask(), [](int Elt) { return Elt == 0; })) {
DemandedLHS.setBit(0);
return true;
}
for (int i = 0; i != NumMaskElts; ++i) {
if (!DemandedElts[i])
continue;
int M = Shuf->getMaskValue(i);
assert(M < (NumElts * 2) && "Invalid shuffle mask constant");
// For undef elements, we don't know anything about the common state of
// the shuffle result.
if (M == -1)
return false;
if (M < NumElts)
DemandedLHS.setBit(M % NumElts);
else
DemandedRHS.setBit(M % NumElts);
}
return true;
}
static void computeKnownBits(const Value *V, const APInt &DemandedElts,
KnownBits &Known, unsigned Depth, const Query &Q);
static void computeKnownBits(const Value *V, KnownBits &Known, unsigned Depth,
const Query &Q) {
// FIXME: We currently have no way to represent the DemandedElts of a scalable
// vector
if (isa<ScalableVectorType>(V->getType())) {
Known.resetAll();
return;
}
auto *FVTy = dyn_cast<FixedVectorType>(V->getType());
APInt DemandedElts =
FVTy ? APInt::getAllOnesValue(FVTy->getNumElements()) : APInt(1, 1);
computeKnownBits(V, DemandedElts, Known, Depth, Q);
}
void llvm::computeKnownBits(const Value *V, KnownBits &Known,
const DataLayout &DL, unsigned Depth,
AssumptionCache *AC, const Instruction *CxtI,
const DominatorTree *DT,
OptimizationRemarkEmitter *ORE, bool UseInstrInfo) {
::computeKnownBits(V, Known, Depth,
Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo, ORE));
}
void llvm::computeKnownBits(const Value *V, const APInt &DemandedElts,
KnownBits &Known, const DataLayout &DL,
unsigned Depth, AssumptionCache *AC,
const Instruction *CxtI, const DominatorTree *DT,
OptimizationRemarkEmitter *ORE, bool UseInstrInfo) {
::computeKnownBits(V, DemandedElts, Known, Depth,
Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo, ORE));
}
static KnownBits computeKnownBits(const Value *V, const APInt &DemandedElts,
unsigned Depth, const Query &Q);
static KnownBits computeKnownBits(const Value *V, unsigned Depth,
const Query &Q);
KnownBits llvm::computeKnownBits(const Value *V, const DataLayout &DL,
unsigned Depth, AssumptionCache *AC,
const Instruction *CxtI,
const DominatorTree *DT,
OptimizationRemarkEmitter *ORE,
bool UseInstrInfo) {
return ::computeKnownBits(
V, Depth, Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo, ORE));
}
KnownBits llvm::computeKnownBits(const Value *V, const APInt &DemandedElts,
const DataLayout &DL, unsigned Depth,
AssumptionCache *AC, const Instruction *CxtI,
const DominatorTree *DT,
OptimizationRemarkEmitter *ORE,
bool UseInstrInfo) {
return ::computeKnownBits(
V, DemandedElts, Depth,
Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo, ORE));
}
bool llvm::haveNoCommonBitsSet(const Value *LHS, const Value *RHS,
const DataLayout &DL, AssumptionCache *AC,
const Instruction *CxtI, const DominatorTree *DT,
bool UseInstrInfo) {
assert(LHS->getType() == RHS->getType() &&
"LHS and RHS should have the same type");
assert(LHS->getType()->isIntOrIntVectorTy() &&
"LHS and RHS should be integers");
// Look for an inverted mask: (X & ~M) op (Y & M).
Value *M;
if (match(LHS, m_c_And(m_Not(m_Value(M)), m_Value())) &&
match(RHS, m_c_And(m_Specific(M), m_Value())))
return true;
if (match(RHS, m_c_And(m_Not(m_Value(M)), m_Value())) &&
match(LHS, m_c_And(m_Specific(M), m_Value())))
return true;
IntegerType *IT = cast<IntegerType>(LHS->getType()->getScalarType());
KnownBits LHSKnown(IT->getBitWidth());
KnownBits RHSKnown(IT->getBitWidth());
computeKnownBits(LHS, LHSKnown, DL, 0, AC, CxtI, DT, nullptr, UseInstrInfo);
computeKnownBits(RHS, RHSKnown, DL, 0, AC, CxtI, DT, nullptr, UseInstrInfo);
return (LHSKnown.Zero | RHSKnown.Zero).isAllOnesValue();
}
bool llvm::isOnlyUsedInZeroEqualityComparison(const Instruction *CxtI) {
for (const User *U : CxtI->users()) {
if (const ICmpInst *IC = dyn_cast<ICmpInst>(U))
if (IC->isEquality())
if (Constant *C = dyn_cast<Constant>(IC->getOperand(1)))
if (C->isNullValue())
continue;
return false;
}
return true;
}
static bool isKnownToBeAPowerOfTwo(const Value *V, bool OrZero, unsigned Depth,
const Query &Q);
bool llvm::isKnownToBeAPowerOfTwo(const Value *V, const DataLayout &DL,
bool OrZero, unsigned Depth,
AssumptionCache *AC, const Instruction *CxtI,
const DominatorTree *DT, bool UseInstrInfo) {
return ::isKnownToBeAPowerOfTwo(
V, OrZero, Depth, Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo));
}
static bool isKnownNonZero(const Value *V, const APInt &DemandedElts,
unsigned Depth, const Query &Q);
static bool isKnownNonZero(const Value *V, unsigned Depth, const Query &Q);
bool llvm::isKnownNonZero(const Value *V, const DataLayout &DL, unsigned Depth,
AssumptionCache *AC, const Instruction *CxtI,
const DominatorTree *DT, bool UseInstrInfo) {
return ::isKnownNonZero(V, Depth,
Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo));
}
bool llvm::isKnownNonNegative(const Value *V, const DataLayout &DL,
unsigned Depth, AssumptionCache *AC,
const Instruction *CxtI, const DominatorTree *DT,
bool UseInstrInfo) {
KnownBits Known =
computeKnownBits(V, DL, Depth, AC, CxtI, DT, nullptr, UseInstrInfo);
return Known.isNonNegative();
}
bool llvm::isKnownPositive(const Value *V, const DataLayout &DL, unsigned Depth,
AssumptionCache *AC, const Instruction *CxtI,
const DominatorTree *DT, bool UseInstrInfo) {
if (auto *CI = dyn_cast<ConstantInt>(V))
return CI->getValue().isStrictlyPositive();
// TODO: We'd doing two recursive queries here. We should factor this such
// that only a single query is needed.
return isKnownNonNegative(V, DL, Depth, AC, CxtI, DT, UseInstrInfo) &&
isKnownNonZero(V, DL, Depth, AC, CxtI, DT, UseInstrInfo);
}
bool llvm::isKnownNegative(const Value *V, const DataLayout &DL, unsigned Depth,
AssumptionCache *AC, const Instruction *CxtI,
const DominatorTree *DT, bool UseInstrInfo) {
KnownBits Known =
computeKnownBits(V, DL, Depth, AC, CxtI, DT, nullptr, UseInstrInfo);
return Known.isNegative();
}
static bool isKnownNonEqual(const Value *V1, const Value *V2, unsigned Depth,
const Query &Q);
bool llvm::isKnownNonEqual(const Value *V1, const Value *V2,
const DataLayout &DL, AssumptionCache *AC,
const Instruction *CxtI, const DominatorTree *DT,
bool UseInstrInfo) {
return ::isKnownNonEqual(V1, V2, 0,
Query(DL, AC, safeCxtI(V2, V1, CxtI), DT,
UseInstrInfo, /*ORE=*/nullptr));
}
static bool MaskedValueIsZero(const Value *V, const APInt &Mask, unsigned Depth,
const Query &Q);
bool llvm::MaskedValueIsZero(const Value *V, const APInt &Mask,
const DataLayout &DL, unsigned Depth,
AssumptionCache *AC, const Instruction *CxtI,
const DominatorTree *DT, bool UseInstrInfo) {
return ::MaskedValueIsZero(
V, Mask, Depth, Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo));
}
static unsigned ComputeNumSignBits(const Value *V, const APInt &DemandedElts,
unsigned Depth, const Query &Q);
static unsigned ComputeNumSignBits(const Value *V, unsigned Depth,
const Query &Q) {
// FIXME: We currently have no way to represent the DemandedElts of a scalable
// vector
if (isa<ScalableVectorType>(V->getType()))
return 1;
auto *FVTy = dyn_cast<FixedVectorType>(V->getType());
APInt DemandedElts =
FVTy ? APInt::getAllOnesValue(FVTy->getNumElements()) : APInt(1, 1);
return ComputeNumSignBits(V, DemandedElts, Depth, Q);
}
unsigned llvm::ComputeNumSignBits(const Value *V, const DataLayout &DL,
unsigned Depth, AssumptionCache *AC,
const Instruction *CxtI,
const DominatorTree *DT, bool UseInstrInfo) {
return ::ComputeNumSignBits(
V, Depth, Query(DL, AC, safeCxtI(V, CxtI), DT, UseInstrInfo));
}
static void computeKnownBitsAddSub(bool Add, const Value *Op0, const Value *Op1,
bool NSW, const APInt &DemandedElts,
KnownBits &KnownOut, KnownBits &Known2,
unsigned Depth, const Query &Q) {
computeKnownBits(Op1, DemandedElts, KnownOut, Depth + 1, Q);
// If one operand is unknown and we have no nowrap information,
// the result will be unknown independently of the second operand.
if (KnownOut.isUnknown() && !NSW)
return;
computeKnownBits(Op0, DemandedElts, Known2, Depth + 1, Q);
KnownOut = KnownBits::computeForAddSub(Add, NSW, Known2, KnownOut);
}
static void computeKnownBitsMul(const Value *Op0, const Value *Op1, bool NSW,
const APInt &DemandedElts, KnownBits &Known,
KnownBits &Known2, unsigned Depth,
const Query &Q) {
computeKnownBits(Op1, DemandedElts, Known, Depth + 1, Q);
computeKnownBits(Op0, DemandedElts, Known2, Depth + 1, Q);
bool isKnownNegative = false;
bool isKnownNonNegative = false;
// If the multiplication is known not to overflow, compute the sign bit.
if (NSW) {
if (Op0 == Op1) {
// The product of a number with itself is non-negative.
isKnownNonNegative = true;
} else {
bool isKnownNonNegativeOp1 = Known.isNonNegative();
bool isKnownNonNegativeOp0 = Known2.isNonNegative();
bool isKnownNegativeOp1 = Known.isNegative();
bool isKnownNegativeOp0 = Known2.isNegative();
// The product of two numbers with the same sign is non-negative.
isKnownNonNegative = (isKnownNegativeOp1 && isKnownNegativeOp0) ||
(isKnownNonNegativeOp1 && isKnownNonNegativeOp0);
// The product of a negative number and a non-negative number is either
// negative or zero.
if (!isKnownNonNegative)
isKnownNegative =
(isKnownNegativeOp1 && isKnownNonNegativeOp0 &&
Known2.isNonZero()) ||
(isKnownNegativeOp0 && isKnownNonNegativeOp1 && Known.isNonZero());
}
}
Known = KnownBits::computeForMul(Known, Known2);
// Only make use of no-wrap flags if we failed to compute the sign bit
// directly. This matters if the multiplication always overflows, in
// which case we prefer to follow the result of the direct computation,
// though as the program is invoking undefined behaviour we can choose
// whatever we like here.
if (isKnownNonNegative && !Known.isNegative())
Known.makeNonNegative();
else if (isKnownNegative && !Known.isNonNegative())
Known.makeNegative();
}
void llvm::computeKnownBitsFromRangeMetadata(const MDNode &Ranges,
KnownBits &Known) {
unsigned BitWidth = Known.getBitWidth();
unsigned NumRanges = Ranges.getNumOperands() / 2;
assert(NumRanges >= 1);
Known.Zero.setAllBits();
Known.One.setAllBits();
for (unsigned i = 0; i < NumRanges; ++i) {
ConstantInt *Lower =
mdconst::extract<ConstantInt>(Ranges.getOperand(2 * i + 0));
ConstantInt *Upper =
mdconst::extract<ConstantInt>(Ranges.getOperand(2 * i + 1));
ConstantRange Range(Lower->getValue(), Upper->getValue());
// The first CommonPrefixBits of all values in Range are equal.
unsigned CommonPrefixBits =
(Range.getUnsignedMax() ^ Range.getUnsignedMin()).countLeadingZeros();
APInt Mask = APInt::getHighBitsSet(BitWidth, CommonPrefixBits);
APInt UnsignedMax = Range.getUnsignedMax().zextOrTrunc(BitWidth);
Known.One &= UnsignedMax & Mask;
Known.Zero &= ~UnsignedMax & Mask;
}
}
static bool isEphemeralValueOf(const Instruction *I, const Value *E) {
SmallVector<const Value *, 16> WorkSet(1, I);
SmallPtrSet<const Value *, 32> Visited;
SmallPtrSet<const Value *, 16> EphValues;
// The instruction defining an assumption's condition itself is always
// considered ephemeral to that assumption (even if it has other
// non-ephemeral users). See r246696's test case for an example.
if (is_contained(I->operands(), E))
return true;
while (!WorkSet.empty()) {
const Value *V = WorkSet.pop_back_val();
if (!Visited.insert(V).second)
continue;
// If all uses of this value are ephemeral, then so is this value.
if (llvm::all_of(V->users(), [&](const User *U) {
return EphValues.count(U);
})) {
if (V == E)
return true;
if (V == I || isSafeToSpeculativelyExecute(V)) {
EphValues.insert(V);
if (const User *U = dyn_cast<User>(V))
append_range(WorkSet, U->operands());
}
}
}
return false;
}
// Is this an intrinsic that cannot be speculated but also cannot trap?
bool llvm::isAssumeLikeIntrinsic(const Instruction *I) {
if (const IntrinsicInst *CI = dyn_cast<IntrinsicInst>(I))
return CI->isAssumeLikeIntrinsic();
return false;
}
bool llvm::isValidAssumeForContext(const Instruction *Inv,
const Instruction *CxtI,
const DominatorTree *DT) {
// There are two restrictions on the use of an assume:
// 1. The assume must dominate the context (or the control flow must
// reach the assume whenever it reaches the context).
// 2. The context must not be in the assume's set of ephemeral values
// (otherwise we will use the assume to prove that the condition
// feeding the assume is trivially true, thus causing the removal of
// the assume).
if (Inv->getParent() == CxtI->getParent()) {
// If Inv and CtxI are in the same block, check if the assume (Inv) is first
// in the BB.
if (Inv->comesBefore(CxtI))
return true;
// Don't let an assume affect itself - this would cause the problems
// `isEphemeralValueOf` is trying to prevent, and it would also make
// the loop below go out of bounds.
if (Inv == CxtI)
return false;
// The context comes first, but they're both in the same block.
// Make sure there is nothing in between that might interrupt
// the control flow, not even CxtI itself.
// We limit the scan distance between the assume and its context instruction
// to avoid a compile-time explosion. This limit is chosen arbitrarily, so
// it can be adjusted if needed (could be turned into a cl::opt).
unsigned ScanLimit = 15;
for (BasicBlock::const_iterator I(CxtI), IE(Inv); I != IE; ++I)
if (!isGuaranteedToTransferExecutionToSuccessor(&*I) || --ScanLimit == 0)
return false;
return !isEphemeralValueOf(Inv, CxtI);
}
// Inv and CxtI are in different blocks.
if (DT) {
if (DT->dominates(Inv, CxtI))
return true;
} else if (Inv->getParent() == CxtI->getParent()->getSinglePredecessor()) {
// We don't have a DT, but this trivially dominates.
return true;
}
return false;
}
static bool cmpExcludesZero(CmpInst::Predicate Pred, const Value *RHS) {
// v u> y implies v != 0.
if (Pred == ICmpInst::ICMP_UGT)
return true;
// Special-case v != 0 to also handle v != null.
if (Pred == ICmpInst::ICMP_NE)
return match(RHS, m_Zero());
// All other predicates - rely on generic ConstantRange handling.
const APInt *C;
if (!match(RHS, m_APInt(C)))
return false;
ConstantRange TrueValues = ConstantRange::makeExactICmpRegion(Pred, *C);
return !TrueValues.contains(APInt::getNullValue(C->getBitWidth()));
}
static bool isKnownNonZeroFromAssume(const Value *V, const Query &Q) {
// Use of assumptions is context-sensitive. If we don't have a context, we
// cannot use them!
if (!Q.AC || !Q.CxtI)
return false;
if (Q.CxtI && V->getType()->isPointerTy()) {
SmallVector<Attribute::AttrKind, 2> AttrKinds{Attribute::NonNull};
if (!NullPointerIsDefined(Q.CxtI->getFunction(),
V->getType()->getPointerAddressSpace()))
AttrKinds.push_back(Attribute::Dereferenceable);
if (getKnowledgeValidInContext(V, AttrKinds, Q.CxtI, Q.DT, Q.AC))
return true;
}
for (auto &AssumeVH : Q.AC->assumptionsFor(V)) {
if (!AssumeVH)
continue;
CallInst *I = cast<CallInst>(AssumeVH);
assert(I->getFunction() == Q.CxtI->getFunction() &&
"Got assumption for the wrong function!");
if (Q.isExcluded(I))
continue;
// Warning: This loop can end up being somewhat performance sensitive.
// We're running this loop for once for each value queried resulting in a
// runtime of ~O(#assumes * #values).
assert(I->getCalledFunction()->getIntrinsicID() == Intrinsic::assume &&
"must be an assume intrinsic");
Value *RHS;
CmpInst::Predicate Pred;
auto m_V = m_CombineOr(m_Specific(V), m_PtrToInt(m_Specific(V)));
if (!match(I->getArgOperand(0), m_c_ICmp(Pred, m_V, m_Value(RHS))))
return false;
if (cmpExcludesZero(Pred, RHS) && isValidAssumeForContext(I, Q.CxtI, Q.DT))
return true;
}
return false;
}
static void computeKnownBitsFromAssume(const Value *V, KnownBits &Known,
unsigned Depth, const Query &Q) {
// Use of assumptions is context-sensitive. If we don't have a context, we
// cannot use them!
if (!Q.AC || !Q.CxtI)
return;
unsigned BitWidth = Known.getBitWidth();
// Refine Known set if the pointer alignment is set by assume bundles.
if (V->getType()->isPointerTy()) {
if (RetainedKnowledge RK = getKnowledgeValidInContext(
V, {Attribute::Alignment}, Q.CxtI, Q.DT, Q.AC)) {
Known.Zero.setLowBits(Log2_32(RK.ArgValue));
}
}
// Note that the patterns below need to be kept in sync with the code
// in AssumptionCache::updateAffectedValues.
for (auto &AssumeVH : Q.AC->assumptionsFor(V)) {
if (!AssumeVH)
continue;
CallInst *I = cast<CallInst>(AssumeVH);
assert(I->getParent()->getParent() == Q.CxtI->getParent()->getParent() &&
"Got assumption for the wrong function!");
if (Q.isExcluded(I))
continue;
// Warning: This loop can end up being somewhat performance sensitive.
// We're running this loop for once for each value queried resulting in a
// runtime of ~O(#assumes * #values).
assert(I->getCalledFunction()->getIntrinsicID() == Intrinsic::assume &&
"must be an assume intrinsic");
Value *Arg = I->getArgOperand(0);
if (Arg == V && isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
assert(BitWidth == 1 && "assume operand is not i1?");
Known.setAllOnes();
return;
}
if (match(Arg, m_Not(m_Specific(V))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
assert(BitWidth == 1 && "assume operand is not i1?");
Known.setAllZero();
return;
}
// The remaining tests are all recursive, so bail out if we hit the limit.
if (Depth == MaxAnalysisRecursionDepth)
continue;
ICmpInst *Cmp = dyn_cast<ICmpInst>(Arg);
if (!Cmp)
continue;
// Note that ptrtoint may change the bitwidth.
Value *A, *B;
auto m_V = m_CombineOr(m_Specific(V), m_PtrToInt(m_Specific(V)));
CmpInst::Predicate Pred;
uint64_t C;
switch (Cmp->getPredicate()) {
default:
break;
case ICmpInst::ICMP_EQ:
// assume(v = a)
if (match(Cmp, m_c_ICmp(Pred, m_V, m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
KnownBits RHSKnown =
computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
Known.Zero |= RHSKnown.Zero;
Known.One |= RHSKnown.One;
// assume(v & b = a)
} else if (match(Cmp,
m_c_ICmp(Pred, m_c_And(m_V, m_Value(B)), m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
KnownBits RHSKnown =
computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
KnownBits MaskKnown =
computeKnownBits(B, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
// For those bits in the mask that are known to be one, we can propagate
// known bits from the RHS to V.
Known.Zero |= RHSKnown.Zero & MaskKnown.One;
Known.One |= RHSKnown.One & MaskKnown.One;
// assume(~(v & b) = a)
} else if (match(Cmp, m_c_ICmp(Pred, m_Not(m_c_And(m_V, m_Value(B))),
m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
KnownBits RHSKnown =
computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
KnownBits MaskKnown =
computeKnownBits(B, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
// For those bits in the mask that are known to be one, we can propagate
// inverted known bits from the RHS to V.
Known.Zero |= RHSKnown.One & MaskKnown.One;
Known.One |= RHSKnown.Zero & MaskKnown.One;
// assume(v | b = a)
} else if (match(Cmp,
m_c_ICmp(Pred, m_c_Or(m_V, m_Value(B)), m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
KnownBits RHSKnown =
computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
KnownBits BKnown =
computeKnownBits(B, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
// For those bits in B that are known to be zero, we can propagate known
// bits from the RHS to V.
Known.Zero |= RHSKnown.Zero & BKnown.Zero;
Known.One |= RHSKnown.One & BKnown.Zero;
// assume(~(v | b) = a)
} else if (match(Cmp, m_c_ICmp(Pred, m_Not(m_c_Or(m_V, m_Value(B))),
m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
KnownBits RHSKnown =
computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
KnownBits BKnown =
computeKnownBits(B, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
// For those bits in B that are known to be zero, we can propagate
// inverted known bits from the RHS to V.
Known.Zero |= RHSKnown.One & BKnown.Zero;
Known.One |= RHSKnown.Zero & BKnown.Zero;
// assume(v ^ b = a)
} else if (match(Cmp,
m_c_ICmp(Pred, m_c_Xor(m_V, m_Value(B)), m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
KnownBits RHSKnown =
computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
KnownBits BKnown =
computeKnownBits(B, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
// For those bits in B that are known to be zero, we can propagate known
// bits from the RHS to V. For those bits in B that are known to be one,
// we can propagate inverted known bits from the RHS to V.
Known.Zero |= RHSKnown.Zero & BKnown.Zero;
Known.One |= RHSKnown.One & BKnown.Zero;
Known.Zero |= RHSKnown.One & BKnown.One;
Known.One |= RHSKnown.Zero & BKnown.One;
// assume(~(v ^ b) = a)
} else if (match(Cmp, m_c_ICmp(Pred, m_Not(m_c_Xor(m_V, m_Value(B))),
m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
KnownBits RHSKnown =
computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
KnownBits BKnown =
computeKnownBits(B, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
// For those bits in B that are known to be zero, we can propagate
// inverted known bits from the RHS to V. For those bits in B that are
// known to be one, we can propagate known bits from the RHS to V.
Known.Zero |= RHSKnown.One & BKnown.Zero;
Known.One |= RHSKnown.Zero & BKnown.Zero;
Known.Zero |= RHSKnown.Zero & BKnown.One;
Known.One |= RHSKnown.One & BKnown.One;
// assume(v << c = a)
} else if (match(Cmp, m_c_ICmp(Pred, m_Shl(m_V, m_ConstantInt(C)),
m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT) && C < BitWidth) {
KnownBits RHSKnown =
computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
// For those bits in RHS that are known, we can propagate them to known
// bits in V shifted to the right by C.
RHSKnown.Zero.lshrInPlace(C);
Known.Zero |= RHSKnown.Zero;
RHSKnown.One.lshrInPlace(C);
Known.One |= RHSKnown.One;
// assume(~(v << c) = a)
} else if (match(Cmp, m_c_ICmp(Pred, m_Not(m_Shl(m_V, m_ConstantInt(C))),
m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT) && C < BitWidth) {
KnownBits RHSKnown =
computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
// For those bits in RHS that are known, we can propagate them inverted
// to known bits in V shifted to the right by C.
RHSKnown.One.lshrInPlace(C);
Known.Zero |= RHSKnown.One;
RHSKnown.Zero.lshrInPlace(C);
Known.One |= RHSKnown.Zero;
// assume(v >> c = a)
} else if (match(Cmp, m_c_ICmp(Pred, m_Shr(m_V, m_ConstantInt(C)),
m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT) && C < BitWidth) {
KnownBits RHSKnown =
computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
// For those bits in RHS that are known, we can propagate them to known
// bits in V shifted to the right by C.
Known.Zero |= RHSKnown.Zero << C;
Known.One |= RHSKnown.One << C;
// assume(~(v >> c) = a)
} else if (match(Cmp, m_c_ICmp(Pred, m_Not(m_Shr(m_V, m_ConstantInt(C))),
m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT) && C < BitWidth) {
KnownBits RHSKnown =
computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
// For those bits in RHS that are known, we can propagate them inverted
// to known bits in V shifted to the right by C.
Known.Zero |= RHSKnown.One << C;
Known.One |= RHSKnown.Zero << C;
}
break;
case ICmpInst::ICMP_SGE:
// assume(v >=_s c) where c is non-negative
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
KnownBits RHSKnown =
computeKnownBits(A, Depth + 1, Query(Q, I)).anyextOrTrunc(BitWidth);
if (RHSKnown.isNonNegative()) {
// We know that the sign bit is zero.
Known.makeNonNegative();
}
}
break;
case ICmpInst::ICMP_SGT:
// assume(v >_s c) where c is at least -1.
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
KnownBits RHSKnown =
computeKnownBits(A, Depth + 1, Query(Q, I)).anyextOrTrunc(BitWidth);
if (RHSKnown.isAllOnes() || RHSKnown.isNonNegative()) {
// We know that the sign bit is zero.
Known.makeNonNegative();
}
}
break;
case ICmpInst::ICMP_SLE:
// assume(v <=_s c) where c is negative
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
KnownBits RHSKnown =
computeKnownBits(A, Depth + 1, Query(Q, I)).anyextOrTrunc(BitWidth);
if (RHSKnown.isNegative()) {
// We know that the sign bit is one.
Known.makeNegative();
}
}
break;
case ICmpInst::ICMP_SLT:
// assume(v <_s c) where c is non-positive
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
KnownBits RHSKnown =
computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
if (RHSKnown.isZero() || RHSKnown.isNegative()) {
// We know that the sign bit is one.
Known.makeNegative();
}
}
break;
case ICmpInst::ICMP_ULE:
// assume(v <=_u c)
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
KnownBits RHSKnown =
computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
// Whatever high bits in c are zero are known to be zero.
Known.Zero.setHighBits(RHSKnown.countMinLeadingZeros());
}
break;
case ICmpInst::ICMP_ULT:
// assume(v <_u c)
if (match(Cmp, m_ICmp(Pred, m_V, m_Value(A))) &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
KnownBits RHSKnown =
computeKnownBits(A, Depth+1, Query(Q, I)).anyextOrTrunc(BitWidth);
// If the RHS is known zero, then this assumption must be wrong (nothing
// is unsigned less than zero). Signal a conflict and get out of here.
if (RHSKnown.isZero()) {
Known.Zero.setAllBits();
Known.One.setAllBits();
break;
}
// Whatever high bits in c are zero are known to be zero (if c is a power
// of 2, then one more).
if (isKnownToBeAPowerOfTwo(A, false, Depth + 1, Query(Q, I)))
Known.Zero.setHighBits(RHSKnown.countMinLeadingZeros() + 1);
else
Known.Zero.setHighBits(RHSKnown.countMinLeadingZeros());
}
break;
}
}
// If assumptions conflict with each other or previous known bits, then we
// have a logical fallacy. It's possible that the assumption is not reachable,
// so this isn't a real bug. On the other hand, the program may have undefined
// behavior, or we might have a bug in the compiler. We can't assert/crash, so
// clear out the known bits, try to warn the user, and hope for the best.
if (Known.Zero.intersects(Known.One)) {
Known.resetAll();
if (Q.ORE)
Q.ORE->emit([&]() {
auto *CxtI = const_cast<Instruction *>(Q.CxtI);
return OptimizationRemarkAnalysis("value-tracking", "BadAssumption",
CxtI)
<< "Detected conflicting code assumptions. Program may "
"have undefined behavior, or compiler may have "
"internal error.";
});
}
}
/// Compute known bits from a shift operator, including those with a
/// non-constant shift amount. Known is the output of this function. Known2 is a
/// pre-allocated temporary with the same bit width as Known and on return
/// contains the known bit of the shift value source. KF is an
/// operator-specific function that, given the known-bits and a shift amount,
/// compute the implied known-bits of the shift operator's result respectively
/// for that shift amount. The results from calling KF are conservatively
/// combined for all permitted shift amounts.
static void computeKnownBitsFromShiftOperator(
const Operator *I, const APInt &DemandedElts, KnownBits &Known,
KnownBits &Known2, unsigned Depth, const Query &Q,
function_ref<KnownBits(const KnownBits &, const KnownBits &)> KF) {
unsigned BitWidth = Known.getBitWidth();
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
// Note: We cannot use Known.Zero.getLimitedValue() here, because if
// BitWidth > 64 and any upper bits are known, we'll end up returning the
// limit value (which implies all bits are known).
uint64_t ShiftAmtKZ = Known.Zero.zextOrTrunc(64).getZExtValue();
uint64_t ShiftAmtKO = Known.One.zextOrTrunc(64).getZExtValue();
bool ShiftAmtIsConstant = Known.isConstant();
bool MaxShiftAmtIsOutOfRange = Known.getMaxValue().uge(BitWidth);
if (ShiftAmtIsConstant) {
Known = KF(Known2, Known);
// If the known bits conflict, this must be an overflowing left shift, so
// the shift result is poison. We can return anything we want. Choose 0 for
// the best folding opportunity.
if (Known.hasConflict())
Known.setAllZero();
return;
}
// If the shift amount could be greater than or equal to the bit-width of the
// LHS, the value could be poison, but bail out because the check below is
// expensive.
// TODO: Should we just carry on?
if (MaxShiftAmtIsOutOfRange) {
Known.resetAll();
return;
}
// It would be more-clearly correct to use the two temporaries for this
// calculation. Reusing the APInts here to prevent unnecessary allocations.
Known.resetAll();
// If we know the shifter operand is nonzero, we can sometimes infer more
// known bits. However this is expensive to compute, so be lazy about it and
// only compute it when absolutely necessary.
Optional<bool> ShifterOperandIsNonZero;
// Early exit if we can't constrain any well-defined shift amount.
if (!(ShiftAmtKZ & (PowerOf2Ceil(BitWidth) - 1)) &&
!(ShiftAmtKO & (PowerOf2Ceil(BitWidth) - 1))) {
ShifterOperandIsNonZero =
isKnownNonZero(I->getOperand(1), DemandedElts, Depth + 1, Q);
if (!*ShifterOperandIsNonZero)
return;
}
Known.Zero.setAllBits();
Known.One.setAllBits();
for (unsigned ShiftAmt = 0; ShiftAmt < BitWidth; ++ShiftAmt) {
// Combine the shifted known input bits only for those shift amounts
// compatible with its known constraints.
if ((ShiftAmt & ~ShiftAmtKZ) != ShiftAmt)
continue;
if ((ShiftAmt | ShiftAmtKO) != ShiftAmt)
continue;
// If we know the shifter is nonzero, we may be able to infer more known
// bits. This check is sunk down as far as possible to avoid the expensive
// call to isKnownNonZero if the cheaper checks above fail.
if (ShiftAmt == 0) {
if (!ShifterOperandIsNonZero.hasValue())
ShifterOperandIsNonZero =
isKnownNonZero(I->getOperand(1), DemandedElts, Depth + 1, Q);
if (*ShifterOperandIsNonZero)
continue;
}
Known = KnownBits::commonBits(
Known, KF(Known2, KnownBits::makeConstant(APInt(32, ShiftAmt))));
}
// If the known bits conflict, the result is poison. Return a 0 and hope the
// caller can further optimize that.
if (Known.hasConflict())
Known.setAllZero();
}
static void computeKnownBitsFromOperator(const Operator *I,
const APInt &DemandedElts,
KnownBits &Known, unsigned Depth,
const Query &Q) {
unsigned BitWidth = Known.getBitWidth();
KnownBits Known2(BitWidth);
switch (I->getOpcode()) {
default: break;
case Instruction::Load:
if (MDNode *MD =
Q.IIQ.getMetadata(cast<LoadInst>(I), LLVMContext::MD_range))
computeKnownBitsFromRangeMetadata(*MD, Known);
break;
case Instruction::And: {
// If either the LHS or the RHS are Zero, the result is zero.
computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
Known &= Known2;
// and(x, add (x, -1)) is a common idiom that always clears the low bit;
// here we handle the more general case of adding any odd number by
// matching the form add(x, add(x, y)) where y is odd.
// TODO: This could be generalized to clearing any bit set in y where the
// following bit is known to be unset in y.
Value *X = nullptr, *Y = nullptr;
if (!Known.Zero[0] && !Known.One[0] &&
match(I, m_c_BinOp(m_Value(X), m_Add(m_Deferred(X), m_Value(Y))))) {
Known2.resetAll();
computeKnownBits(Y, DemandedElts, Known2, Depth + 1, Q);
if (Known2.countMinTrailingOnes() > 0)
Known.Zero.setBit(0);
}
break;
}
case Instruction::Or:
computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
Known |= Known2;
break;
case Instruction::Xor:
computeKnownBits(I->getOperand(1), DemandedElts, Known, Depth + 1, Q);
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
Known ^= Known2;
break;
case Instruction::Mul: {
bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
computeKnownBitsMul(I->getOperand(0), I->getOperand(1), NSW, DemandedElts,
Known, Known2, Depth, Q);
break;
}
case Instruction::UDiv: {
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known = KnownBits::udiv(Known, Known2);
break;
}
case Instruction::Select: {
const Value *LHS = nullptr, *RHS = nullptr;
SelectPatternFlavor SPF = matchSelectPattern(I, LHS, RHS).Flavor;
if (SelectPatternResult::isMinOrMax(SPF)) {
computeKnownBits(RHS, Known, Depth + 1, Q);
computeKnownBits(LHS, Known2, Depth + 1, Q);
switch (SPF) {
default:
llvm_unreachable("Unhandled select pattern flavor!");
case SPF_SMAX:
Known = KnownBits::smax(Known, Known2);
break;
case SPF_SMIN:
Known = KnownBits::smin(Known, Known2);
break;
case SPF_UMAX:
Known = KnownBits::umax(Known, Known2);
break;
case SPF_UMIN:
Known = KnownBits::umin(Known, Known2);
break;
}
break;
}
computeKnownBits(I->getOperand(2), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
// Only known if known in both the LHS and RHS.
Known = KnownBits::commonBits(Known, Known2);
if (SPF == SPF_ABS) {
// RHS from matchSelectPattern returns the negation part of abs pattern.
// If the negate has an NSW flag we can assume the sign bit of the result
// will be 0 because that makes abs(INT_MIN) undefined.
if (match(RHS, m_Neg(m_Specific(LHS))) &&
Q.IIQ.hasNoSignedWrap(cast<Instruction>(RHS)))
Known.Zero.setSignBit();
}
break;
}
case Instruction::FPTrunc:
case Instruction::FPExt:
case Instruction::FPToUI:
case Instruction::FPToSI:
case Instruction::SIToFP:
case Instruction::UIToFP:
break; // Can't work with floating point.
case Instruction::PtrToInt:
case Instruction::IntToPtr:
// Fall through and handle them the same as zext/trunc.
LLVM_FALLTHROUGH;
case Instruction::ZExt:
case Instruction::Trunc: {
Type *SrcTy = I->getOperand(0)->getType();
unsigned SrcBitWidth;
// Note that we handle pointer operands here because of inttoptr/ptrtoint
// which fall through here.
Type *ScalarTy = SrcTy->getScalarType();
SrcBitWidth = ScalarTy->isPointerTy() ?
Q.DL.getPointerTypeSizeInBits(ScalarTy) :
Q.DL.getTypeSizeInBits(ScalarTy);
assert(SrcBitWidth && "SrcBitWidth can't be zero");
Known = Known.anyextOrTrunc(SrcBitWidth);
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
Known = Known.zextOrTrunc(BitWidth);
break;
}
case Instruction::BitCast: {
Type *SrcTy = I->getOperand(0)->getType();
if (SrcTy->isIntOrPtrTy() &&
// TODO: For now, not handling conversions like:
// (bitcast i64 %x to <2 x i32>)
!I->getType()->isVectorTy()) {
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
break;
}
break;
}
case Instruction::SExt: {
// Compute the bits in the result that are not present in the input.
unsigned SrcBitWidth = I->getOperand(0)->getType()->getScalarSizeInBits();
Known = Known.trunc(SrcBitWidth);
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
// If the sign bit of the input is known set or clear, then we know the
// top bits of the result.
Known = Known.sext(BitWidth);
break;
}
case Instruction::Shl: {
bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
auto KF = [NSW](const KnownBits &KnownVal, const KnownBits &KnownAmt) {
KnownBits Result = KnownBits::shl(KnownVal, KnownAmt);
// If this shift has "nsw" keyword, then the result is either a poison
// value or has the same sign bit as the first operand.
if (NSW) {
if (KnownVal.Zero.isSignBitSet())
Result.Zero.setSignBit();
if (KnownVal.One.isSignBitSet())
Result.One.setSignBit();
}
return Result;
};
computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
KF);
// Trailing zeros of a right-shifted constant never decrease.
const APInt *C;
if (match(I->getOperand(0), m_APInt(C)))
Known.Zero.setLowBits(C->countTrailingZeros());
break;
}
case Instruction::LShr: {
auto KF = [](const KnownBits &KnownVal, const KnownBits &KnownAmt) {
return KnownBits::lshr(KnownVal, KnownAmt);
};
computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
KF);
// Leading zeros of a left-shifted constant never decrease.
const APInt *C;
if (match(I->getOperand(0), m_APInt(C)))
Known.Zero.setHighBits(C->countLeadingZeros());
break;
}
case Instruction::AShr: {
auto KF = [](const KnownBits &KnownVal, const KnownBits &KnownAmt) {
return KnownBits::ashr(KnownVal, KnownAmt);
};
computeKnownBitsFromShiftOperator(I, DemandedElts, Known, Known2, Depth, Q,
KF);
break;
}
case Instruction::Sub: {
bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
computeKnownBitsAddSub(false, I->getOperand(0), I->getOperand(1), NSW,
DemandedElts, Known, Known2, Depth, Q);
break;
}
case Instruction::Add: {
bool NSW = Q.IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(I));
computeKnownBitsAddSub(true, I->getOperand(0), I->getOperand(1), NSW,
DemandedElts, Known, Known2, Depth, Q);
break;
}
case Instruction::SRem:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known = KnownBits::srem(Known, Known2);
break;
case Instruction::URem:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known = KnownBits::urem(Known, Known2);
break;
case Instruction::Alloca:
Known.Zero.setLowBits(Log2(cast<AllocaInst>(I)->getAlign()));
break;
case Instruction::GetElementPtr: {
// Analyze all of the subscripts of this getelementptr instruction
// to determine if we can prove known low zero bits.
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
// Accumulate the constant indices in a separate variable
// to minimize the number of calls to computeForAddSub.
APInt AccConstIndices(BitWidth, 0, /*IsSigned*/ true);
gep_type_iterator GTI = gep_type_begin(I);
for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i, ++GTI) {
// TrailZ can only become smaller, short-circuit if we hit zero.
if (Known.isUnknown())
break;
Value *Index = I->getOperand(i);
// Handle case when index is zero.
Constant *CIndex = dyn_cast<Constant>(Index);
if (CIndex && CIndex->isZeroValue())
continue;
if (StructType *STy = GTI.getStructTypeOrNull()) {
// Handle struct member offset arithmetic.
assert(CIndex &&
"Access to structure field must be known at compile time");
if (CIndex->getType()->isVectorTy())
Index = CIndex->getSplatValue();
unsigned Idx = cast<ConstantInt>(Index)->getZExtValue();
const StructLayout *SL = Q.DL.getStructLayout(STy);
uint64_t Offset = SL->getElementOffset(Idx);
AccConstIndices += Offset;
continue;
}
// Handle array index arithmetic.
Type *IndexedTy = GTI.getIndexedType();
if (!IndexedTy->isSized()) {
Known.resetAll();
break;
}
unsigned IndexBitWidth = Index->getType()->getScalarSizeInBits();
KnownBits IndexBits(IndexBitWidth);
computeKnownBits(Index, IndexBits, Depth + 1, Q);
TypeSize IndexTypeSize = Q.DL.getTypeAllocSize(IndexedTy);
uint64_t TypeSizeInBytes = IndexTypeSize.getKnownMinSize();
KnownBits ScalingFactor(IndexBitWidth);
// Multiply by current sizeof type.
// &A[i] == A + i * sizeof(*A[i]).
if (IndexTypeSize.isScalable()) {
// For scalable types the only thing we know about sizeof is
// that this is a multiple of the minimum size.
ScalingFactor.Zero.setLowBits(countTrailingZeros(TypeSizeInBytes));
} else if (IndexBits.isConstant()) {
APInt IndexConst = IndexBits.getConstant();
APInt ScalingFactor(IndexBitWidth, TypeSizeInBytes);
IndexConst *= ScalingFactor;
AccConstIndices += IndexConst.sextOrTrunc(BitWidth);
continue;
} else {
ScalingFactor =
KnownBits::makeConstant(APInt(IndexBitWidth, TypeSizeInBytes));
}
IndexBits = KnownBits::computeForMul(IndexBits, ScalingFactor);
// If the offsets have a different width from the pointer, according
// to the language reference we need to sign-extend or truncate them
// to the width of the pointer.
IndexBits = IndexBits.sextOrTrunc(BitWidth);
// Note that inbounds does *not* guarantee nsw for the addition, as only
// the offset is signed, while the base address is unsigned.
Known = KnownBits::computeForAddSub(
/*Add=*/true, /*NSW=*/false, Known, IndexBits);
}
if (!Known.isUnknown() && !AccConstIndices.isNullValue()) {
KnownBits Index = KnownBits::makeConstant(AccConstIndices);
Known = KnownBits::computeForAddSub(
/*Add=*/true, /*NSW=*/false, Known, Index);
}
break;
}
case Instruction::PHI: {
const PHINode *P = cast<PHINode>(I);
BinaryOperator *BO = nullptr;
Value *R = nullptr, *L = nullptr;
if (matchSimpleRecurrence(P, BO, R, L)) {
// Handle the case of a simple two-predecessor recurrence PHI.
// There's a lot more that could theoretically be done here, but
// this is sufficient to catch some interesting cases.
unsigned Opcode = BO->getOpcode();
// If this is a shift recurrence, we know the bits being shifted in.
// We can combine that with information about the start value of the
// recurrence to conclude facts about the result.
if ((Opcode == Instruction::LShr || Opcode == Instruction::AShr ||
Opcode == Instruction::Shl) &&
BO->getOperand(0) == I) {
// We have matched a recurrence of the form:
// %iv = [R, %entry], [%iv.next, %backedge]
// %iv.next = shift_op %iv, L
// Recurse with the phi context to avoid concern about whether facts
// inferred hold at original context instruction. TODO: It may be
// correct to use the original context. IF warranted, explore and
// add sufficient tests to cover.
Query RecQ = Q;
RecQ.CxtI = P;
computeKnownBits(R, DemandedElts, Known2, Depth + 1, RecQ);
switch (Opcode) {
case Instruction::Shl:
// A shl recurrence will only increase the tailing zeros
Known.Zero.setLowBits(Known2.countMinTrailingZeros());
break;
case Instruction::LShr:
// A lshr recurrence will preserve the leading zeros of the
// start value
Known.Zero.setHighBits(Known2.countMinLeadingZeros());
break;
case Instruction::AShr:
// An ashr recurrence will extend the initial sign bit
Known.Zero.setHighBits(Known2.countMinLeadingZeros());
Known.One.setHighBits(Known2.countMinLeadingOnes());
break;
};
}
// Check for operations that have the property that if
// both their operands have low zero bits, the result
// will have low zero bits.
if (Opcode == Instruction::Add ||
Opcode == Instruction::Sub ||
Opcode == Instruction::And ||
Opcode == Instruction::Or ||
Opcode == Instruction::Mul) {
// Change the context instruction to the "edge" that flows into the
// phi. This is important because that is where the value is actually
// "evaluated" even though it is used later somewhere else. (see also
// D69571).
Query RecQ = Q;
unsigned OpNum = P->getOperand(0) == R ? 0 : 1;
Instruction *RInst = P->getIncomingBlock(OpNum)->getTerminator();
Instruction *LInst = P->getIncomingBlock(1-OpNum)->getTerminator();
// Ok, we have a PHI of the form L op= R. Check for low
// zero bits.
RecQ.CxtI = RInst;
computeKnownBits(R, Known2, Depth + 1, RecQ);
// We need to take the minimum number of known bits
KnownBits Known3(BitWidth);
RecQ.CxtI = LInst;
computeKnownBits(L, Known3, Depth + 1, RecQ);
Known.Zero.setLowBits(std::min(Known2.countMinTrailingZeros(),
Known3.countMinTrailingZeros()));
auto *OverflowOp = dyn_cast<OverflowingBinaryOperator>(BO);
if (OverflowOp && Q.IIQ.hasNoSignedWrap(OverflowOp)) {
// If initial value of recurrence is nonnegative, and we are adding
// a nonnegative number with nsw, the result can only be nonnegative
// or poison value regardless of the number of times we execute the
// add in phi recurrence. If initial value is negative and we are
// adding a negative number with nsw, the result can only be
// negative or poison value. Similar arguments apply to sub and mul.
//
// (add non-negative, non-negative) --> non-negative
// (add negative, negative) --> negative
if (Opcode == Instruction::Add) {
if (Known2.isNonNegative() && Known3.isNonNegative())
Known.makeNonNegative();
else if (Known2.isNegative() && Known3.isNegative())
Known.makeNegative();
}
// (sub nsw non-negative, negative) --> non-negative
// (sub nsw negative, non-negative) --> negative
else if (Opcode == Instruction::Sub && BO->getOperand(0) == I) {
if (Known2.isNonNegative() && Known3.isNegative())
Known.makeNonNegative();
else if (Known2.isNegative() && Known3.isNonNegative())
Known.makeNegative();
}
// (mul nsw non-negative, non-negative) --> non-negative
else if (Opcode == Instruction::Mul && Known2.isNonNegative() &&
Known3.isNonNegative())
Known.makeNonNegative();
}
break;
}
}
// Unreachable blocks may have zero-operand PHI nodes.
if (P->getNumIncomingValues() == 0)
break;
// Otherwise take the unions of the known bit sets of the operands,
// taking conservative care to avoid excessive recursion.
if (Depth < MaxAnalysisRecursionDepth - 1 && !Known.Zero && !Known.One) {
// Skip if every incoming value references to ourself.
if (dyn_cast_or_null<UndefValue>(P->hasConstantValue()))
break;
Known.Zero.setAllBits();
Known.One.setAllBits();
for (unsigned u = 0, e = P->getNumIncomingValues(); u < e; ++u) {
Value *IncValue = P->getIncomingValue(u);
// Skip direct self references.
if (IncValue == P) continue;
// Change the context instruction to the "edge" that flows into the
// phi. This is important because that is where the value is actually
// "evaluated" even though it is used later somewhere else. (see also
// D69571).
Query RecQ = Q;
RecQ.CxtI = P->getIncomingBlock(u)->getTerminator();
Known2 = KnownBits(BitWidth);
// Recurse, but cap the recursion to one level, because we don't
// want to waste time spinning around in loops.
computeKnownBits(IncValue, Known2, MaxAnalysisRecursionDepth - 1, RecQ);
Known = KnownBits::commonBits(Known, Known2);
// If all bits have been ruled out, there's no need to check
// more operands.
if (Known.isUnknown())
break;
}
}
break;
}
case Instruction::Call:
case Instruction::Invoke:
// If range metadata is attached to this call, set known bits from that,
// and then intersect with known bits based on other properties of the
// function.
if (MDNode *MD =
Q.IIQ.getMetadata(cast<Instruction>(I), LLVMContext::MD_range))
computeKnownBitsFromRangeMetadata(*MD, Known);
if (const Value *RV = cast<CallBase>(I)->getReturnedArgOperand()) {
computeKnownBits(RV, Known2, Depth + 1, Q);
Known.Zero |= Known2.Zero;
Known.One |= Known2.One;
}
if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::abs: {
computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
bool IntMinIsPoison = match(II->getArgOperand(1), m_One());
Known = Known2.abs(IntMinIsPoison);
break;
}
case Intrinsic::bitreverse:
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
Known.Zero |= Known2.Zero.reverseBits();
Known.One |= Known2.One.reverseBits();
break;
case Intrinsic::bswap:
computeKnownBits(I->getOperand(0), DemandedElts, Known2, Depth + 1, Q);
Known.Zero |= Known2.Zero.byteSwap();
Known.One |= Known2.One.byteSwap();
break;
case Intrinsic::ctlz: {
computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
// If we have a known 1, its position is our upper bound.
unsigned PossibleLZ = Known2.countMaxLeadingZeros();
// If this call is undefined for 0, the result will be less than 2^n.
if (II->getArgOperand(1) == ConstantInt::getTrue(II->getContext()))
PossibleLZ = std::min(PossibleLZ, BitWidth - 1);
unsigned LowBits = Log2_32(PossibleLZ)+1;
Known.Zero.setBitsFrom(LowBits);
break;
}
case Intrinsic::cttz: {
computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
// If we have a known 1, its position is our upper bound.
unsigned PossibleTZ = Known2.countMaxTrailingZeros();
// If this call is undefined for 0, the result will be less than 2^n.
if (II->getArgOperand(1) == ConstantInt::getTrue(II->getContext()))
PossibleTZ = std::min(PossibleTZ, BitWidth - 1);
unsigned LowBits = Log2_32(PossibleTZ)+1;
Known.Zero.setBitsFrom(LowBits);
break;
}
case Intrinsic::ctpop: {
computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
// We can bound the space the count needs. Also, bits known to be zero
// can't contribute to the population.
unsigned BitsPossiblySet = Known2.countMaxPopulation();
unsigned LowBits = Log2_32(BitsPossiblySet)+1;
Known.Zero.setBitsFrom(LowBits);
// TODO: we could bound KnownOne using the lower bound on the number
// of bits which might be set provided by popcnt KnownOne2.
break;
}
case Intrinsic::fshr:
case Intrinsic::fshl: {
const APInt *SA;
if (!match(I->getOperand(2), m_APInt(SA)))
break;
// Normalize to funnel shift left.
uint64_t ShiftAmt = SA->urem(BitWidth);
if (II->getIntrinsicID() == Intrinsic::fshr)
ShiftAmt = BitWidth - ShiftAmt;
KnownBits Known3(BitWidth);
computeKnownBits(I->getOperand(0), Known2, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known3, Depth + 1, Q);
Known.Zero =
Known2.Zero.shl(ShiftAmt) | Known3.Zero.lshr(BitWidth - ShiftAmt);
Known.One =
Known2.One.shl(ShiftAmt) | Known3.One.lshr(BitWidth - ShiftAmt);
break;
}
case Intrinsic::uadd_sat:
case Intrinsic::usub_sat: {
bool IsAdd = II->getIntrinsicID() == Intrinsic::uadd_sat;
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
// Add: Leading ones of either operand are preserved.
// Sub: Leading zeros of LHS and leading ones of RHS are preserved
// as leading zeros in the result.
unsigned LeadingKnown;
if (IsAdd)
LeadingKnown = std::max(Known.countMinLeadingOnes(),
Known2.countMinLeadingOnes());
else
LeadingKnown = std::max(Known.countMinLeadingZeros(),
Known2.countMinLeadingOnes());
Known = KnownBits::computeForAddSub(
IsAdd, /* NSW */ false, Known, Known2);
// We select between the operation result and all-ones/zero
// respectively, so we can preserve known ones/zeros.
if (IsAdd) {
Known.One.setHighBits(LeadingKnown);
Known.Zero.clearAllBits();
} else {
Known.Zero.setHighBits(LeadingKnown);
Known.One.clearAllBits();
}
break;
}
case Intrinsic::umin:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known = KnownBits::umin(Known, Known2);
break;
case Intrinsic::umax:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known = KnownBits::umax(Known, Known2);
break;
case Intrinsic::smin:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known = KnownBits::smin(Known, Known2);
break;
case Intrinsic::smax:
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
computeKnownBits(I->getOperand(1), Known2, Depth + 1, Q);
Known = KnownBits::smax(Known, Known2);
break;
case Intrinsic::x86_sse42_crc32_64_64:
Known.Zero.setBitsFrom(32);
break;
}
}
break;
case Instruction::ShuffleVector: {
auto *Shuf = dyn_cast<ShuffleVectorInst>(I);
// FIXME: Do we need to handle ConstantExpr involving shufflevectors?
if (!Shuf) {
Known.resetAll();
return;
}
// For undef elements, we don't know anything about the common state of
// the shuffle result.
APInt DemandedLHS, DemandedRHS;
if (!getShuffleDemandedElts(Shuf, DemandedElts, DemandedLHS, DemandedRHS)) {
Known.resetAll();
return;
}
Known.One.setAllBits();
Known.Zero.setAllBits();
if (!!DemandedLHS) {
const Value *LHS = Shuf->getOperand(0);
computeKnownBits(LHS, DemandedLHS, Known, Depth + 1, Q);
// If we don't know any bits, early out.
if (Known.isUnknown())
break;
}
if (!!DemandedRHS) {
const Value *RHS = Shuf->getOperand(1);
computeKnownBits(RHS, DemandedRHS, Known2, Depth + 1, Q);
Known = KnownBits::commonBits(Known, Known2);
}
break;
}
case Instruction::InsertElement: {
const Value *Vec = I->getOperand(0);
const Value *Elt = I->getOperand(1);
auto *CIdx = dyn_cast<ConstantInt>(I->getOperand(2));
// Early out if the index is non-constant or out-of-range.
unsigned NumElts = DemandedElts.getBitWidth();
if (!CIdx || CIdx->getValue().uge(NumElts)) {
Known.resetAll();
return;
}
Known.One.setAllBits();
Known.Zero.setAllBits();
unsigned EltIdx = CIdx->getZExtValue();
// Do we demand the inserted element?
if (DemandedElts[EltIdx]) {
computeKnownBits(Elt, Known, Depth + 1, Q);
// If we don't know any bits, early out.
if (Known.isUnknown())
break;
}
// We don't need the base vector element that has been inserted.
APInt DemandedVecElts = DemandedElts;
DemandedVecElts.clearBit(EltIdx);
if (!!DemandedVecElts) {
computeKnownBits(Vec, DemandedVecElts, Known2, Depth + 1, Q);
Known = KnownBits::commonBits(Known, Known2);
}
break;
}
case Instruction::ExtractElement: {
// Look through extract element. If the index is non-constant or
// out-of-range demand all elements, otherwise just the extracted element.
const Value *Vec = I->getOperand(0);
const Value *Idx = I->getOperand(1);
auto *CIdx = dyn_cast<ConstantInt>(Idx);
if (isa<ScalableVectorType>(Vec->getType())) {
// FIXME: there's probably *something* we can do with scalable vectors
Known.resetAll();
break;
}
unsigned NumElts = cast<FixedVectorType>(Vec->getType())->getNumElements();
APInt DemandedVecElts = APInt::getAllOnesValue(NumElts);
if (CIdx && CIdx->getValue().ult(NumElts))
DemandedVecElts = APInt::getOneBitSet(NumElts, CIdx->getZExtValue());
computeKnownBits(Vec, DemandedVecElts, Known, Depth + 1, Q);
break;
}
case Instruction::ExtractValue:
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I->getOperand(0))) {
const ExtractValueInst *EVI = cast<ExtractValueInst>(I);
if (EVI->getNumIndices() != 1) break;
if (EVI->getIndices()[0] == 0) {
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::uadd_with_overflow:
case Intrinsic::sadd_with_overflow:
computeKnownBitsAddSub(true, II->getArgOperand(0),
II->getArgOperand(1), false, DemandedElts,
Known, Known2, Depth, Q);
break;
case Intrinsic::usub_with_overflow:
case Intrinsic::ssub_with_overflow:
computeKnownBitsAddSub(false, II->getArgOperand(0),
II->getArgOperand(1), false, DemandedElts,
Known, Known2, Depth, Q);
break;
case Intrinsic::umul_with_overflow:
case Intrinsic::smul_with_overflow:
computeKnownBitsMul(II->getArgOperand(0), II->getArgOperand(1), false,
DemandedElts, Known, Known2, Depth, Q);
break;
}
}
}
break;
case Instruction::Freeze:
if (isGuaranteedNotToBePoison(I->getOperand(0), Q.AC, Q.CxtI, Q.DT,
Depth + 1))
computeKnownBits(I->getOperand(0), Known, Depth + 1, Q);
break;
}
}
/// Determine which bits of V are known to be either zero or one and return
/// them.
KnownBits computeKnownBits(const Value *V, const APInt &DemandedElts,
unsigned Depth, const Query &Q) {
KnownBits Known(getBitWidth(V->getType(), Q.DL));
computeKnownBits(V, DemandedElts, Known, Depth, Q);
return Known;
}
/// Determine which bits of V are known to be either zero or one and return
/// them.
KnownBits computeKnownBits(const Value *V, unsigned Depth, const Query &Q) {
KnownBits Known(getBitWidth(V->getType(), Q.DL));
computeKnownBits(V, Known, Depth, Q);
return Known;
}
/// Determine which bits of V are known to be either zero or one and return
/// them in the Known bit set.
///
/// NOTE: we cannot consider 'undef' to be "IsZero" here. The problem is that
/// we cannot optimize based on the assumption that it is zero without changing
/// it to be an explicit zero. If we don't change it to zero, other code could
/// optimized based on the contradictory assumption that it is non-zero.
/// Because instcombine aggressively folds operations with undef args anyway,
/// this won't lose us code quality.
///
/// This function is defined on values with integer type, values with pointer
/// type, and vectors of integers. In the case
/// where V is a vector, known zero, and known one values are the
/// same width as the vector element, and the bit is set only if it is true
/// for all of the demanded elements in the vector specified by DemandedElts.
void computeKnownBits(const Value *V, const APInt &DemandedElts,
KnownBits &Known, unsigned Depth, const Query &Q) {
if (!DemandedElts || isa<ScalableVectorType>(V->getType())) {
// No demanded elts or V is a scalable vector, better to assume we don't
// know anything.
Known.resetAll();
return;
}
assert(V && "No Value?");
assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
#ifndef NDEBUG
Type *Ty = V->getType();
unsigned BitWidth = Known.getBitWidth();
assert((Ty->isIntOrIntVectorTy(BitWidth) || Ty->isPtrOrPtrVectorTy()) &&
"Not integer or pointer type!");
if (auto *FVTy = dyn_cast<FixedVectorType>(Ty)) {
assert(
FVTy->getNumElements() == DemandedElts.getBitWidth() &&
"DemandedElt width should equal the fixed vector number of elements");
} else {
assert(DemandedElts == APInt(1, 1) &&
"DemandedElt width should be 1 for scalars");
}
Type *ScalarTy = Ty->getScalarType();
if (ScalarTy->isPointerTy()) {
assert(BitWidth == Q.DL.getPointerTypeSizeInBits(ScalarTy) &&
"V and Known should have same BitWidth");
} else {
assert(BitWidth == Q.DL.getTypeSizeInBits(ScalarTy) &&
"V and Known should have same BitWidth");
}
#endif
const APInt *C;
if (match(V, m_APInt(C))) {
// We know all of the bits for a scalar constant or a splat vector constant!
Known = KnownBits::makeConstant(*C);
return;
}
// Null and aggregate-zero are all-zeros.
if (isa<ConstantPointerNull>(V) || isa<ConstantAggregateZero>(V)) {
Known.setAllZero();
return;
}
// Handle a constant vector by taking the intersection of the known bits of
// each element.
if (const ConstantDataVector *CDV = dyn_cast<ConstantDataVector>(V)) {
// We know that CDV must be a vector of integers. Take the intersection of
// each element.
Known.Zero.setAllBits(); Known.One.setAllBits();
for (unsigned i = 0, e = CDV->getNumElements(); i != e; ++i) {
if (!DemandedElts[i])
continue;
APInt Elt = CDV->getElementAsAPInt(i);
Known.Zero &= ~Elt;
Known.One &= Elt;
}
return;
}
if (const auto *CV = dyn_cast<ConstantVector>(V)) {
// We know that CV must be a vector of integers. Take the intersection of
// each element.
Known.Zero.setAllBits(); Known.One.setAllBits();
for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) {
if (!DemandedElts[i])
continue;
Constant *Element = CV->getAggregateElement(i);
auto *ElementCI = dyn_cast_or_null<ConstantInt>(Element);
if (!ElementCI) {
Known.resetAll();
return;
}
const APInt &Elt = ElementCI->getValue();
Known.Zero &= ~Elt;
Known.One &= Elt;
}
return;
}
// Start out not knowing anything.
Known.resetAll();
// We can't imply anything about undefs.
if (isa<UndefValue>(V))
return;
// There's no point in looking through other users of ConstantData for
// assumptions. Confirm that we've handled them all.
assert(!isa<ConstantData>(V) && "Unhandled constant data!");
// All recursive calls that increase depth must come after this.
if (Depth == MaxAnalysisRecursionDepth)
return;
// A weak GlobalAlias is totally unknown. A non-weak GlobalAlias has
// the bits of its aliasee.
if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
if (!GA->isInterposable())
computeKnownBits(GA->getAliasee(), Known, Depth + 1, Q);
return;
}
if (const Operator *I = dyn_cast<Operator>(V))
computeKnownBitsFromOperator(I, DemandedElts, Known, Depth, Q);
// Aligned pointers have trailing zeros - refine Known.Zero set
if (isa<PointerType>(V->getType())) {
Align Alignment = V->getPointerAlignment(Q.DL);
Known.Zero.setLowBits(Log2(Alignment));
}
// computeKnownBitsFromAssume strictly refines Known.
// Therefore, we run them after computeKnownBitsFromOperator.
// Check whether a nearby assume intrinsic can determine some known bits.
computeKnownBitsFromAssume(V, Known, Depth, Q);
assert((Known.Zero & Known.One) == 0 && "Bits known to be one AND zero?");
}
/// Return true if the given value is known to have exactly one
/// bit set when defined. For vectors return true if every element is known to
/// be a power of two when defined. Supports values with integer or pointer
/// types and vectors of integers.
bool isKnownToBeAPowerOfTwo(const Value *V, bool OrZero, unsigned Depth,
const Query &Q) {
assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
// Attempt to match against constants.
if (OrZero && match(V, m_Power2OrZero()))
return true;
if (match(V, m_Power2()))
return true;
// 1 << X is clearly a power of two if the one is not shifted off the end. If
// it is shifted off the end then the result is undefined.
if (match(V, m_Shl(m_One(), m_Value())))
return true;
// (signmask) >>l X is clearly a power of two if the one is not shifted off
// the bottom. If it is shifted off the bottom then the result is undefined.
if (match(V, m_LShr(m_SignMask(), m_Value())))
return true;
// The remaining tests are all recursive, so bail out if we hit the limit.
if (Depth++ == MaxAnalysisRecursionDepth)
return false;
Value *X = nullptr, *Y = nullptr;
// A shift left or a logical shift right of a power of two is a power of two
// or zero.
if (OrZero && (match(V, m_Shl(m_Value(X), m_Value())) ||
match(V, m_LShr(m_Value(X), m_Value()))))
return isKnownToBeAPowerOfTwo(X, /*OrZero*/ true, Depth, Q);
if (const ZExtInst *ZI = dyn_cast<ZExtInst>(V))
return isKnownToBeAPowerOfTwo(ZI->getOperand(0), OrZero, Depth, Q);
if (const SelectInst *SI = dyn_cast<SelectInst>(V))
return isKnownToBeAPowerOfTwo(SI->getTrueValue(), OrZero, Depth, Q) &&
isKnownToBeAPowerOfTwo(SI->getFalseValue(), OrZero, Depth, Q);
// Peek through min/max.
if (match(V, m_MaxOrMin(m_Value(X), m_Value(Y)))) {
return isKnownToBeAPowerOfTwo(X, OrZero, Depth, Q) &&
isKnownToBeAPowerOfTwo(Y, OrZero, Depth, Q);
}
if (OrZero && match(V, m_And(m_Value(X), m_Value(Y)))) {
// A power of two and'd with anything is a power of two or zero.
if (isKnownToBeAPowerOfTwo(X, /*OrZero*/ true, Depth, Q) ||
isKnownToBeAPowerOfTwo(Y, /*OrZero*/ true, Depth, Q))
return true;
// X & (-X) is always a power of two or zero.
if (match(X, m_Neg(m_Specific(Y))) || match(Y, m_Neg(m_Specific(X))))
return true;
return false;
}
// Adding a power-of-two or zero to the same power-of-two or zero yields
// either the original power-of-two, a larger power-of-two or zero.
if (match(V, m_Add(m_Value(X), m_Value(Y)))) {
const OverflowingBinaryOperator *VOBO = cast<OverflowingBinaryOperator>(V);
if (OrZero || Q.IIQ.hasNoUnsignedWrap(VOBO) ||
Q.IIQ.hasNoSignedWrap(VOBO)) {
if (match(X, m_And(m_Specific(Y), m_Value())) ||
match(X, m_And(m_Value(), m_Specific(Y))))
if (isKnownToBeAPowerOfTwo(Y, OrZero, Depth, Q))
return true;
if (match(Y, m_And(m_Specific(X), m_Value())) ||
match(Y, m_And(m_Value(), m_Specific(X))))
if (isKnownToBeAPowerOfTwo(X, OrZero, Depth, Q))
return true;
unsigned BitWidth = V->getType()->getScalarSizeInBits();
KnownBits LHSBits(BitWidth);
computeKnownBits(X, LHSBits, Depth, Q);
KnownBits RHSBits(BitWidth);
computeKnownBits(Y, RHSBits, Depth, Q);
// If i8 V is a power of two or zero:
// ZeroBits: 1 1 1 0 1 1 1 1
// ~ZeroBits: 0 0 0 1 0 0 0 0
if ((~(LHSBits.Zero & RHSBits.Zero)).isPowerOf2())
// If OrZero isn't set, we cannot give back a zero result.
// Make sure either the LHS or RHS has a bit set.
if (OrZero || RHSBits.One.getBoolValue() || LHSBits.One.getBoolValue())
return true;
}
}
// An exact divide or right shift can only shift off zero bits, so the result
// is a power of two only if the first operand is a power of two and not
// copying a sign bit (sdiv int_min, 2).
if (match(V, m_Exact(m_LShr(m_Value(), m_Value()))) ||
match(V, m_Exact(m_UDiv(m_Value(), m_Value())))) {
return isKnownToBeAPowerOfTwo(cast<Operator>(V)->getOperand(0), OrZero,
Depth, Q);
}
return false;
}
/// Test whether a GEP's result is known to be non-null.
///
/// Uses properties inherent in a GEP to try to determine whether it is known
/// to be non-null.
///
/// Currently this routine does not support vector GEPs.
static bool isGEPKnownNonNull(const GEPOperator *GEP, unsigned Depth,
const Query &Q) {
const Function *F = nullptr;
if (const Instruction *I = dyn_cast<Instruction>(GEP))
F = I->getFunction();
if (!GEP->isInBounds() ||
NullPointerIsDefined(F, GEP->getPointerAddressSpace()))
return false;
// FIXME: Support vector-GEPs.
assert(GEP->getType()->isPointerTy() && "We only support plain pointer GEP");
// If the base pointer is non-null, we cannot walk to a null address with an
// inbounds GEP in address space zero.
if (isKnownNonZero(GEP->getPointerOperand(), Depth, Q))
return true;
// Walk the GEP operands and see if any operand introduces a non-zero offset.
// If so, then the GEP cannot produce a null pointer, as doing so would
// inherently violate the inbounds contract within address space zero.
for (gep_type_iterator GTI = gep_type_begin(GEP), GTE = gep_type_end(GEP);
GTI != GTE; ++GTI) {
// Struct types are easy -- they must always be indexed by a constant.
if (StructType *STy = GTI.getStructTypeOrNull()) {
ConstantInt *OpC = cast<ConstantInt>(GTI.getOperand());
unsigned ElementIdx = OpC->getZExtValue();
const StructLayout *SL = Q.DL.getStructLayout(STy);
uint64_t ElementOffset = SL->getElementOffset(ElementIdx);
if (ElementOffset > 0)
return true;
continue;
}
// If we have a zero-sized type, the index doesn't matter. Keep looping.
if (Q.DL.getTypeAllocSize(GTI.getIndexedType()).getKnownMinSize() == 0)
continue;
// Fast path the constant operand case both for efficiency and so we don't
// increment Depth when just zipping down an all-constant GEP.
if (ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand())) {
if (!OpC->isZero())
return true;
continue;
}
// We post-increment Depth here because while isKnownNonZero increments it
// as well, when we pop back up that increment won't persist. We don't want
// to recurse 10k times just because we have 10k GEP operands. We don't
// bail completely out because we want to handle constant GEPs regardless
// of depth.
if (Depth++ >= MaxAnalysisRecursionDepth)
continue;
if (isKnownNonZero(GTI.getOperand(), Depth, Q))
return true;
}
return false;
}
static bool isKnownNonNullFromDominatingCondition(const Value *V,
const Instruction *CtxI,
const DominatorTree *DT) {
if (isa<Constant>(V))
return false;
if (!CtxI || !DT)
return false;
unsigned NumUsesExplored = 0;
for (auto *U : V->users()) {
// Avoid massive lists
if (NumUsesExplored >= DomConditionsMaxUses)
break;
NumUsesExplored++;
// If the value is used as an argument to a call or invoke, then argument
// attributes may provide an answer about null-ness.
if (const auto *CB = dyn_cast<CallBase>(U))
if (auto *CalledFunc = CB->getCalledFunction())
for (const Argument &Arg : CalledFunc->args())
if (CB->getArgOperand(Arg.getArgNo()) == V &&
Arg.hasNonNullAttr(/* AllowUndefOrPoison */ false) &&
DT->dominates(CB, CtxI))
return true;
// If the value is used as a load/store, then the pointer must be non null.
if (V == getLoadStorePointerOperand(U)) {
const Instruction *I = cast<Instruction>(U);
if (!NullPointerIsDefined(I->getFunction(),
V->getType()->getPointerAddressSpace()) &&
DT->dominates(I, CtxI))
return true;
}
// Consider only compare instructions uniquely controlling a branch
Value *RHS;
CmpInst::Predicate Pred;
if (!match(U, m_c_ICmp(Pred, m_Specific(V), m_Value(RHS))))
continue;
bool NonNullIfTrue;
if (cmpExcludesZero(Pred, RHS))
NonNullIfTrue = true;
else if (cmpExcludesZero(CmpInst::getInversePredicate(Pred), RHS))
NonNullIfTrue = false;
else
continue;
SmallVector<const User *, 4> WorkList;
SmallPtrSet<const User *, 4> Visited;
for (auto *CmpU : U->users()) {
assert(WorkList.empty() && "Should be!");
if (Visited.insert(CmpU).second)
WorkList.push_back(CmpU);
while (!WorkList.empty()) {
auto *Curr = WorkList.pop_back_val();
// If a user is an AND, add all its users to the work list. We only
// propagate "pred != null" condition through AND because it is only
// correct to assume that all conditions of AND are met in true branch.
// TODO: Support similar logic of OR and EQ predicate?
if (NonNullIfTrue)
if (match(Curr, m_LogicalAnd(m_Value(), m_Value()))) {
for (auto *CurrU : Curr->users())
if (Visited.insert(CurrU).second)
WorkList.push_back(CurrU);
continue;
}
if (const BranchInst *BI = dyn_cast<BranchInst>(Curr)) {
assert(BI->isConditional() && "uses a comparison!");
BasicBlock *NonNullSuccessor =
BI->getSuccessor(NonNullIfTrue ? 0 : 1);
BasicBlockEdge Edge(BI->getParent(), NonNullSuccessor);
if (Edge.isSingleEdge() && DT->dominates(Edge, CtxI->getParent()))
return true;
} else if (NonNullIfTrue && isGuard(Curr) &&
DT->dominates(cast<Instruction>(Curr), CtxI)) {
return true;
}
}
}
}
return false;
}
/// Does the 'Range' metadata (which must be a valid MD_range operand list)
/// ensure that the value it's attached to is never Value? 'RangeType' is
/// is the type of the value described by the range.
static bool rangeMetadataExcludesValue(const MDNode* Ranges, const APInt& Value) {
const unsigned NumRanges = Ranges->getNumOperands() / 2;
assert(NumRanges >= 1);
for (unsigned i = 0; i < NumRanges; ++i) {
ConstantInt *Lower =
mdconst::extract<ConstantInt>(Ranges->getOperand(2 * i + 0));
ConstantInt *Upper =
mdconst::extract<ConstantInt>(Ranges->getOperand(2 * i + 1));
ConstantRange Range(Lower->getValue(), Upper->getValue());
if (Range.contains(Value))
return false;
}
return true;
}
/// Return true if the given value is known to be non-zero when defined. For
/// vectors, return true if every demanded element is known to be non-zero when
/// defined. For pointers, if the context instruction and dominator tree are
/// specified, perform context-sensitive analysis and return true if the
/// pointer couldn't possibly be null at the specified instruction.
/// Supports values with integer or pointer type and vectors of integers.
bool isKnownNonZero(const Value *V, const APInt &DemandedElts, unsigned Depth,
const Query &Q) {
// FIXME: We currently have no way to represent the DemandedElts of a scalable
// vector
if (isa<ScalableVectorType>(V->getType()))
return false;
if (auto *C = dyn_cast<Constant>(V)) {
if (C->isNullValue())
return false;
if (isa<ConstantInt>(C))
// Must be non-zero due to null test above.
return true;
if (auto *CE = dyn_cast<ConstantExpr>(C)) {
// See the comment for IntToPtr/PtrToInt instructions below.
if (CE->getOpcode() == Instruction::IntToPtr ||
CE->getOpcode() == Instruction::PtrToInt)
if (Q.DL.getTypeSizeInBits(CE->getOperand(0)->getType())
.getFixedSize() <=
Q.DL.getTypeSizeInBits(CE->getType()).getFixedSize())
return isKnownNonZero(CE->getOperand(0), Depth, Q);
}
// For constant vectors, check that all elements are undefined or known
// non-zero to determine that the whole vector is known non-zero.
if (auto *VecTy = dyn_cast<FixedVectorType>(C->getType())) {
for (unsigned i = 0, e = VecTy->getNumElements(); i != e; ++i) {
if (!DemandedElts[i])
continue;
Constant *Elt = C->getAggregateElement(i);
if (!Elt || Elt->isNullValue())
return false;
if (!isa<UndefValue>(Elt) && !isa<ConstantInt>(Elt))
return false;
}
return true;
}
// A global variable in address space 0 is non null unless extern weak
// or an absolute symbol reference. Other address spaces may have null as a
// valid address for a global, so we can't assume anything.
if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
if (!GV->isAbsoluteSymbolRef() && !GV->hasExternalWeakLinkage() &&
GV->getType()->getAddressSpace() == 0)
return true;
} else
return false;
}
if (auto *I = dyn_cast<Instruction>(V)) {
if (MDNode *Ranges = Q.IIQ.getMetadata(I, LLVMContext::MD_range)) {
// If the possible ranges don't contain zero, then the value is
// definitely non-zero.
if (auto *Ty = dyn_cast<IntegerType>(V->getType())) {
const APInt ZeroValue(Ty->getBitWidth(), 0);
if (rangeMetadataExcludesValue(Ranges, ZeroValue))
return true;
}
}
}
if (isKnownNonZeroFromAssume(V, Q))
return true;
// Some of the tests below are recursive, so bail out if we hit the limit.
if (Depth++ >= MaxAnalysisRecursionDepth)
return false;
// Check for pointer simplifications.
if (PointerType *PtrTy = dyn_cast<PointerType>(V->getType())) {
// Alloca never returns null, malloc might.
if (isa<AllocaInst>(V) && Q.DL.getAllocaAddrSpace() == 0)
return true;
// A byval, inalloca may not be null in a non-default addres space. A
// nonnull argument is assumed never 0.
if (const Argument *A = dyn_cast<Argument>(V)) {
if (((A->hasPassPointeeByValueCopyAttr() &&
!NullPointerIsDefined(A->getParent(), PtrTy->getAddressSpace())) ||
A->hasNonNullAttr()))
return true;
}
// A Load tagged with nonnull metadata is never null.
if (const LoadInst *LI = dyn_cast<LoadInst>(V))
if (Q.IIQ.getMetadata(LI, LLVMContext::MD_nonnull))
return true;
if (const auto *Call = dyn_cast<CallBase>(V)) {
if (Call->isReturnNonNull())
return true;
if (const auto *RP = getArgumentAliasingToReturnedPointer(Call, true))
return isKnownNonZero(RP, Depth, Q);
}
}
if (isKnownNonNullFromDominatingCondition(V, Q.CxtI, Q.DT))
return true;
// Check for recursive pointer simplifications.
if (V->getType()->isPointerTy()) {
// Look through bitcast operations, GEPs, and int2ptr instructions as they
// do not alter the value, or at least not the nullness property of the
// value, e.g., int2ptr is allowed to zero/sign extend the value.
//
// Note that we have to take special care to avoid looking through
// truncating casts, e.g., int2ptr/ptr2int with appropriate sizes, as well
// as casts that can alter the value, e.g., AddrSpaceCasts.
if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V))
return isGEPKnownNonNull(GEP, Depth, Q);
if (auto *BCO = dyn_cast<BitCastOperator>(V))
return isKnownNonZero(BCO->getOperand(0), Depth, Q);
if (auto *I2P = dyn_cast<IntToPtrInst>(V))
if (Q.DL.getTypeSizeInBits(I2P->getSrcTy()).getFixedSize() <=
Q.DL.getTypeSizeInBits(I2P->getDestTy()).getFixedSize())
return isKnownNonZero(I2P->getOperand(0), Depth, Q);
}
// Similar to int2ptr above, we can look through ptr2int here if the cast
// is a no-op or an extend and not a truncate.
if (auto *P2I = dyn_cast<PtrToIntInst>(V))
if (Q.DL.getTypeSizeInBits(P2I->getSrcTy()).getFixedSize() <=
Q.DL.getTypeSizeInBits(P2I->getDestTy()).getFixedSize())
return isKnownNonZero(P2I->getOperand(0), Depth, Q);
unsigned BitWidth = getBitWidth(V->getType()->getScalarType(), Q.DL);
// X | Y != 0 if X != 0 or Y != 0.
Value *X = nullptr, *Y = nullptr;
if (match(V, m_Or(m_Value(X), m_Value(Y))))
return isKnownNonZero(X, DemandedElts, Depth, Q) ||
isKnownNonZero(Y, DemandedElts, Depth, Q);
// ext X != 0 if X != 0.
if (isa<SExtInst>(V) || isa<ZExtInst>(V))
return isKnownNonZero(cast<Instruction>(V)->getOperand(0), Depth, Q);
// shl X, Y != 0 if X is odd. Note that the value of the shift is undefined
// if the lowest bit is shifted off the end.
if (match(V, m_Shl(m_Value(X), m_Value(Y)))) {
// shl nuw can't remove any non-zero bits.
const OverflowingBinaryOperator *BO = cast<OverflowingBinaryOperator>(V);
if (Q.IIQ.hasNoUnsignedWrap(BO))
return isKnownNonZero(X, Depth, Q);
KnownBits Known(BitWidth);
computeKnownBits(X, DemandedElts, Known, Depth, Q);
if (Known.One[0])
return true;
}
// shr X, Y != 0 if X is negative. Note that the value of the shift is not
// defined if the sign bit is shifted off the end.
else if (match(V, m_Shr(m_Value(X), m_Value(Y)))) {
// shr exact can only shift out zero bits.
const PossiblyExactOperator *BO = cast<PossiblyExactOperator>(V);
if (BO->isExact())
return isKnownNonZero(X, Depth, Q);
KnownBits Known = computeKnownBits(X, DemandedElts, Depth, Q);
if (Known.isNegative())
return true;
// If the shifter operand is a constant, and all of the bits shifted
// out are known to be zero, and X is known non-zero then at least one
// non-zero bit must remain.
if (ConstantInt *Shift = dyn_cast<ConstantInt>(Y)) {
auto ShiftVal = Shift->getLimitedValue(BitWidth - 1);
// Is there a known one in the portion not shifted out?
if (Known.countMaxLeadingZeros() < BitWidth - ShiftVal)
return true;
// Are all the bits to be shifted out known zero?
if (Known.countMinTrailingZeros() >= ShiftVal)
return isKnownNonZero(X, DemandedElts, Depth, Q);
}
}
// div exact can only produce a zero if the dividend is zero.
else if (match(V, m_Exact(m_IDiv(m_Value(X), m_Value())))) {
return isKnownNonZero(X, DemandedElts, Depth, Q);
}
// X + Y.
else if (match(V, m_Add(m_Value(X), m_Value(Y)))) {
KnownBits XKnown = computeKnownBits(X, DemandedElts, Depth, Q);
KnownBits YKnown = computeKnownBits(Y, DemandedElts, Depth, Q);
// If X and Y are both non-negative (as signed values) then their sum is not
// zero unless both X and Y are zero.
if (XKnown.isNonNegative() && YKnown.isNonNegative())
if (isKnownNonZero(X, DemandedElts, Depth, Q) ||
isKnownNonZero(Y, DemandedElts, Depth, Q))
return true;
// If X and Y are both negative (as signed values) then their sum is not
// zero unless both X and Y equal INT_MIN.
if (XKnown.isNegative() && YKnown.isNegative()) {
APInt Mask = APInt::getSignedMaxValue(BitWidth);
// The sign bit of X is set. If some other bit is set then X is not equal
// to INT_MIN.
if (XKnown.One.intersects(Mask))
return true;
// The sign bit of Y is set. If some other bit is set then Y is not equal
// to INT_MIN.
if (YKnown.One.intersects(Mask))
return true;
}
// The sum of a non-negative number and a power of two is not zero.
if (XKnown.isNonNegative() &&
isKnownToBeAPowerOfTwo(Y, /*OrZero*/ false, Depth, Q))
return true;
if (YKnown.isNonNegative() &&
isKnownToBeAPowerOfTwo(X, /*OrZero*/ false, Depth, Q))
return true;
}
// X * Y.
else if (match(V, m_Mul(m_Value(X), m_Value(Y)))) {
const OverflowingBinaryOperator *BO = cast<OverflowingBinaryOperator>(V);
// If X and Y are non-zero then so is X * Y as long as the multiplication
// does not overflow.
if ((Q.IIQ.hasNoSignedWrap(BO) || Q.IIQ.hasNoUnsignedWrap(BO)) &&
isKnownNonZero(X, DemandedElts, Depth, Q) &&
isKnownNonZero(Y, DemandedElts, Depth, Q))
return true;
}
// (C ? X : Y) != 0 if X != 0 and Y != 0.
else if (const SelectInst *SI = dyn_cast<SelectInst>(V)) {
if (isKnownNonZero(SI->getTrueValue(), DemandedElts, Depth, Q) &&
isKnownNonZero(SI->getFalseValue(), DemandedElts, Depth, Q))
return true;
}
// PHI
else if (const PHINode *PN = dyn_cast<PHINode>(V)) {
// Try and detect a recurrence that monotonically increases from a
// starting value, as these are common as induction variables.
BinaryOperator *BO = nullptr;
Value *Start = nullptr, *Step = nullptr;
const APInt *StartC, *StepC;
if (Q.IIQ.UseInstrInfo && matchSimpleRecurrence(PN, BO, Start, Step) &&
match(Start, m_APInt(StartC)) && match(Step, m_APInt(StepC))) {
if (BO->getOpcode() == Instruction::Add &&
(BO->hasNoUnsignedWrap() || BO->hasNoSignedWrap()) &&
StartC->isStrictlyPositive() && !StepC->isNegative())
return true;
if (BO->getOpcode() == Instruction::Mul &&
(BO->hasNoUnsignedWrap() || BO->hasNoSignedWrap()) &&
!StartC->isNullValue() && StepC->isStrictlyPositive())
return true;
}
// Check if all incoming values are non-zero using recursion.
Query RecQ = Q;
unsigned NewDepth = std::max(Depth, MaxAnalysisRecursionDepth - 1);
return llvm::all_of(PN->operands(), [&](const Use &U) {
if (U.get() == PN)
return true;
RecQ.CxtI = PN->getIncomingBlock(U)->getTerminator();
return isKnownNonZero(U.get(), DemandedElts, NewDepth, RecQ);
});
}
// ExtractElement
else if (const auto *EEI = dyn_cast<ExtractElementInst>(V)) {
const Value *Vec = EEI->getVectorOperand();
const Value *Idx = EEI->getIndexOperand();
auto *CIdx = dyn_cast<ConstantInt>(Idx);
if (auto *VecTy = dyn_cast<FixedVectorType>(Vec->getType())) {
unsigned NumElts = VecTy->getNumElements();
APInt DemandedVecElts = APInt::getAllOnesValue(NumElts);
if (CIdx && CIdx->getValue().ult(NumElts))
DemandedVecElts = APInt::getOneBitSet(NumElts, CIdx->getZExtValue());
return isKnownNonZero(Vec, DemandedVecElts, Depth, Q);
}
}
// Freeze
else if (const FreezeInst *FI = dyn_cast<FreezeInst>(V)) {
auto *Op = FI->getOperand(0);
if (isKnownNonZero(Op, Depth, Q) &&
isGuaranteedNotToBePoison(Op, Q.AC, Q.CxtI, Q.DT, Depth))
return true;
}
KnownBits Known(BitWidth);
computeKnownBits(V, DemandedElts, Known, Depth, Q);
return Known.One != 0;
}
bool isKnownNonZero(const Value* V, unsigned Depth, const Query& Q) {
// FIXME: We currently have no way to represent the DemandedElts of a scalable
// vector
if (isa<ScalableVectorType>(V->getType()))
return false;
auto *FVTy = dyn_cast<FixedVectorType>(V->getType());
APInt DemandedElts =
FVTy ? APInt::getAllOnesValue(FVTy->getNumElements()) : APInt(1, 1);
return isKnownNonZero(V, DemandedElts, Depth, Q);
}
/// Return true if V2 == V1 + X, where X is known non-zero.
static bool isAddOfNonZero(const Value *V1, const Value *V2, unsigned Depth,
const Query &Q) {
const BinaryOperator *BO = dyn_cast<BinaryOperator>(V1);
if (!BO || BO->getOpcode() != Instruction::Add)
return false;
Value *Op = nullptr;
if (V2 == BO->getOperand(0))
Op = BO->getOperand(1);
else if (V2 == BO->getOperand(1))
Op = BO->getOperand(0);
else
return false;
return isKnownNonZero(Op, Depth + 1, Q);
}
/// Return true if V2 == V1 * C, where V1 is known non-zero, C is not 0/1 and
/// the multiplication is nuw or nsw.
static bool isNonEqualMul(const Value *V1, const Value *V2, unsigned Depth,
const Query &Q) {
if (auto *OBO = dyn_cast<OverflowingBinaryOperator>(V2)) {
const APInt *C;
return match(OBO, m_Mul(m_Specific(V1), m_APInt(C))) &&
(OBO->hasNoUnsignedWrap() || OBO->hasNoSignedWrap()) &&
!C->isNullValue() && !C->isOneValue() &&
isKnownNonZero(V1, Depth + 1, Q);
}
return false;
}
/// Return true if it is known that V1 != V2.
static bool isKnownNonEqual(const Value *V1, const Value *V2, unsigned Depth,
const Query &Q) {
if (V1 == V2)
return false;
if (V1->getType() != V2->getType())
// We can't look through casts yet.
return false;
if (Depth >= MaxAnalysisRecursionDepth)
return false;
// See if we can recurse through (exactly one of) our operands. This
// requires our operation be 1-to-1 and map every input value to exactly
// one output value. Such an operation is invertible.
auto *O1 = dyn_cast<Operator>(V1);
auto *O2 = dyn_cast<Operator>(V2);
if (O1 && O2 && O1->getOpcode() == O2->getOpcode()) {
switch (O1->getOpcode()) {
default: break;
case Instruction::Add:
case Instruction::Sub:
// Assume operand order has been canonicalized
if (O1->getOperand(0) == O2->getOperand(0))
return isKnownNonEqual(O1->getOperand(1), O2->getOperand(1),
Depth + 1, Q);
if (O1->getOperand(1) == O2->getOperand(1))
return isKnownNonEqual(O1->getOperand(0), O2->getOperand(0),
Depth + 1, Q);
break;
case Instruction::Mul: {
// invertible if A * B == (A * B) mod 2^N where A, and B are integers
// and N is the bitwdith. The nsw case is non-obvious, but proven by
// alive2: https://alive2.llvm.org/ce/z/Z6D5qK
auto *OBO1 = cast<OverflowingBinaryOperator>(O1);
auto *OBO2 = cast<OverflowingBinaryOperator>(O2);
if ((!OBO1->hasNoUnsignedWrap() || !OBO2->hasNoUnsignedWrap()) &&
(!OBO1->hasNoSignedWrap() || !OBO2->hasNoSignedWrap()))
break;
// Assume operand order has been canonicalized
if (O1->getOperand(1) == O2->getOperand(1) &&
isa<ConstantInt>(O1->getOperand(1)) &&
!cast<ConstantInt>(O1->getOperand(1))->isZero())
return isKnownNonEqual(O1->getOperand(0), O2->getOperand(0),
Depth + 1, Q);
break;
}
case Instruction::SExt:
case Instruction::ZExt:
if (O1->getOperand(0)->getType() == O2->getOperand(0)->getType())
return isKnownNonEqual(O1->getOperand(0), O2->getOperand(0),
Depth + 1, Q);
break;
};
}
if (isAddOfNonZero(V1, V2, Depth, Q) || isAddOfNonZero(V2, V1, Depth, Q))
return true;
if (isNonEqualMul(V1, V2, Depth, Q) || isNonEqualMul(V2, V1, Depth, Q))
return true;
if (V1->getType()->isIntOrIntVectorTy()) {
// Are any known bits in V1 contradictory to known bits in V2? If V1
// has a known zero where V2 has a known one, they must not be equal.
KnownBits Known1 = computeKnownBits(V1, Depth, Q);
KnownBits Known2 = computeKnownBits(V2, Depth, Q);
if (Known1.Zero.intersects(Known2.One) ||
Known2.Zero.intersects(Known1.One))
return true;
}
return false;
}
/// Return true if 'V & Mask' is known to be zero. We use this predicate to
/// simplify operations downstream. Mask is known to be zero for bits that V
/// cannot have.
///
/// This function is defined on values with integer type, values with pointer
/// type, and vectors of integers. In the case
/// where V is a vector, the mask, known zero, and known one values are the
/// same width as the vector element, and the bit is set only if it is true
/// for all of the elements in the vector.
bool MaskedValueIsZero(const Value *V, const APInt &Mask, unsigned Depth,
const Query &Q) {
KnownBits Known(Mask.getBitWidth());
computeKnownBits(V, Known, Depth, Q);
return Mask.isSubsetOf(Known.Zero);
}
// Match a signed min+max clamp pattern like smax(smin(In, CHigh), CLow).
// Returns the input and lower/upper bounds.
static bool isSignedMinMaxClamp(const Value *Select, const Value *&In,
const APInt *&CLow, const APInt *&CHigh) {
assert(isa<Operator>(Select) &&
cast<Operator>(Select)->getOpcode() == Instruction::Select &&
"Input should be a Select!");
const Value *LHS = nullptr, *RHS = nullptr;
SelectPatternFlavor SPF = matchSelectPattern(Select, LHS, RHS).Flavor;
if (SPF != SPF_SMAX && SPF != SPF_SMIN)
return false;
if (!match(RHS, m_APInt(CLow)))
return false;
const Value *LHS2 = nullptr, *RHS2 = nullptr;
SelectPatternFlavor SPF2 = matchSelectPattern(LHS, LHS2, RHS2).Flavor;
if (getInverseMinMaxFlavor(SPF) != SPF2)
return false;
if (!match(RHS2, m_APInt(CHigh)))
return false;
if (SPF == SPF_SMIN)
std::swap(CLow, CHigh);
In = LHS2;
return CLow->sle(*CHigh);
}
/// For vector constants, loop over the elements and find the constant with the
/// minimum number of sign bits. Return 0 if the value is not a vector constant
/// or if any element was not analyzed; otherwise, return the count for the
/// element with the minimum number of sign bits.
static unsigned computeNumSignBitsVectorConstant(const Value *V,
const APInt &DemandedElts,
unsigned TyBits) {
const auto *CV = dyn_cast<Constant>(V);
if (!CV || !isa<FixedVectorType>(CV->getType()))
return 0;
unsigned MinSignBits = TyBits;
unsigned NumElts = cast<FixedVectorType>(CV->getType())->getNumElements();
for (unsigned i = 0; i != NumElts; ++i) {
if (!DemandedElts[i])
continue;
// If we find a non-ConstantInt, bail out.
auto *Elt = dyn_cast_or_null<ConstantInt>(CV->getAggregateElement(i));
if (!Elt)
return 0;
MinSignBits = std::min(MinSignBits, Elt->getValue().getNumSignBits());
}
return MinSignBits;
}
static unsigned ComputeNumSignBitsImpl(const Value *V,
const APInt &DemandedElts,
unsigned Depth, const Query &Q);
static unsigned ComputeNumSignBits(const Value *V, const APInt &DemandedElts,
unsigned Depth, const Query &Q) {
unsigned Result = ComputeNumSignBitsImpl(V, DemandedElts, Depth, Q);
assert(Result > 0 && "At least one sign bit needs to be present!");
return Result;
}
/// Return the number of times the sign bit of the register is replicated into
/// the other bits. We know that at least 1 bit is always equal to the sign bit
/// (itself), but other cases can give us information. For example, immediately
/// after an "ashr X, 2", we know that the top 3 bits are all equal to each
/// other, so we return 3. For vectors, return the number of sign bits for the
/// vector element with the minimum number of known sign bits of the demanded
/// elements in the vector specified by DemandedElts.
static unsigned ComputeNumSignBitsImpl(const Value *V,
const APInt &DemandedElts,
unsigned Depth, const Query &Q) {
Type *Ty = V->getType();
// FIXME: We currently have no way to represent the DemandedElts of a scalable
// vector
if (isa<ScalableVectorType>(Ty))
return 1;
#ifndef NDEBUG
assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
if (auto *FVTy = dyn_cast<FixedVectorType>(Ty)) {
assert(
FVTy->getNumElements() == DemandedElts.getBitWidth() &&
"DemandedElt width should equal the fixed vector number of elements");
} else {
assert(DemandedElts == APInt(1, 1) &&
"DemandedElt width should be 1 for scalars");
}
#endif
// We return the minimum number of sign bits that are guaranteed to be present
// in V, so for undef we have to conservatively return 1. We don't have the
// same behavior for poison though -- that's a FIXME today.
Type *ScalarTy = Ty->getScalarType();
unsigned TyBits = ScalarTy->isPointerTy() ?
Q.DL.getPointerTypeSizeInBits(ScalarTy) :
Q.DL.getTypeSizeInBits(ScalarTy);
unsigned Tmp, Tmp2;
unsigned FirstAnswer = 1;
// Note that ConstantInt is handled by the general computeKnownBits case
// below.
if (Depth == MaxAnalysisRecursionDepth)
return 1;
if (auto *U = dyn_cast<Operator>(V)) {
switch (Operator::getOpcode(V)) {
default: break;
case Instruction::SExt:
Tmp = TyBits - U->getOperand(0)->getType()->getScalarSizeInBits();
return ComputeNumSignBits(U->getOperand(0), Depth + 1, Q) + Tmp;
case Instruction::SDiv: {
const APInt *Denominator;
// sdiv X, C -> adds log(C) sign bits.
if (match(U->getOperand(1), m_APInt(Denominator))) {
// Ignore non-positive denominator.
if (!Denominator->isStrictlyPositive())
break;
// Calculate the incoming numerator bits.
unsigned NumBits = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
// Add floor(log(C)) bits to the numerator bits.
return std::min(TyBits, NumBits + Denominator->logBase2());
}
break;
}
case Instruction::SRem: {
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
const APInt *Denominator;
// srem X, C -> we know that the result is within [-C+1,C) when C is a
// positive constant. This let us put a lower bound on the number of sign
// bits.
if (match(U->getOperand(1), m_APInt(Denominator))) {
// Ignore non-positive denominator.
if (Denominator->isStrictlyPositive()) {
// Calculate the leading sign bit constraints by examining the
// denominator. Given that the denominator is positive, there are two
// cases:
//
// 1. The numerator is positive. The result range is [0,C) and
// [0,C) u< (1 << ceilLogBase2(C)).
//
// 2. The numerator is negative. Then the result range is (-C,0] and
// integers in (-C,0] are either 0 or >u (-1 << ceilLogBase2(C)).
//
// Thus a lower bound on the number of sign bits is `TyBits -
// ceilLogBase2(C)`.
unsigned ResBits = TyBits - Denominator->ceilLogBase2();
Tmp = std::max(Tmp, ResBits);
}
}
return Tmp;
}
case Instruction::AShr: {
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
// ashr X, C -> adds C sign bits. Vectors too.
const APInt *ShAmt;
if (match(U->getOperand(1), m_APInt(ShAmt))) {
if (ShAmt->uge(TyBits))
break; // Bad shift.
unsigned ShAmtLimited = ShAmt->getZExtValue();
Tmp += ShAmtLimited;
if (Tmp > TyBits) Tmp = TyBits;
}
return Tmp;
}
case Instruction::Shl: {
const APInt *ShAmt;
if (match(U->getOperand(1), m_APInt(ShAmt))) {
// shl destroys sign bits.
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
if (ShAmt->uge(TyBits) || // Bad shift.
ShAmt->uge(Tmp)) break; // Shifted all sign bits out.
Tmp2 = ShAmt->getZExtValue();
return Tmp - Tmp2;
}
break;
}
case Instruction::And:
case Instruction::Or:
case Instruction::Xor: // NOT is handled here.
// Logical binary ops preserve the number of sign bits at the worst.
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
if (Tmp != 1) {
Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
FirstAnswer = std::min(Tmp, Tmp2);
// We computed what we know about the sign bits as our first
// answer. Now proceed to the generic code that uses
// computeKnownBits, and pick whichever answer is better.
}
break;
case Instruction::Select: {
// If we have a clamp pattern, we know that the number of sign bits will
// be the minimum of the clamp min/max range.
const Value *X;
const APInt *CLow, *CHigh;
if (isSignedMinMaxClamp(U, X, CLow, CHigh))
return std::min(CLow->getNumSignBits(), CHigh->getNumSignBits());
Tmp = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
if (Tmp == 1) break;
Tmp2 = ComputeNumSignBits(U->getOperand(2), Depth + 1, Q);
return std::min(Tmp, Tmp2);
}
case Instruction::Add:
// Add can have at most one carry bit. Thus we know that the output
// is, at worst, one more bit than the inputs.
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
if (Tmp == 1) break;
// Special case decrementing a value (ADD X, -1):
if (const auto *CRHS = dyn_cast<Constant>(U->getOperand(1)))
if (CRHS->isAllOnesValue()) {
KnownBits Known(TyBits);
computeKnownBits(U->getOperand(0), Known, Depth + 1, Q);
// If the input is known to be 0 or 1, the output is 0/-1, which is
// all sign bits set.
if ((Known.Zero | 1).isAllOnesValue())
return TyBits;
// If we are subtracting one from a positive number, there is no carry
// out of the result.
if (Known.isNonNegative())
return Tmp;
}
Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
if (Tmp2 == 1) break;
return std::min(Tmp, Tmp2) - 1;
case Instruction::Sub:
Tmp2 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
if (Tmp2 == 1) break;
// Handle NEG.
if (const auto *CLHS = dyn_cast<Constant>(U->getOperand(0)))
if (CLHS->isNullValue()) {
KnownBits Known(TyBits);
computeKnownBits(U->getOperand(1), Known, Depth + 1, Q);
// If the input is known to be 0 or 1, the output is 0/-1, which is
// all sign bits set.
if ((Known.Zero | 1).isAllOnesValue())
return TyBits;
// If the input is known to be positive (the sign bit is known clear),
// the output of the NEG has the same number of sign bits as the
// input.
if (Known.isNonNegative())
return Tmp2;
// Otherwise, we treat this like a SUB.
}
// Sub can have at most one carry bit. Thus we know that the output
// is, at worst, one more bit than the inputs.
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
if (Tmp == 1) break;
return std::min(Tmp, Tmp2) - 1;
case Instruction::Mul: {
// The output of the Mul can be at most twice the valid bits in the
// inputs.
unsigned SignBitsOp0 = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
if (SignBitsOp0 == 1) break;
unsigned SignBitsOp1 = ComputeNumSignBits(U->getOperand(1), Depth + 1, Q);
if (SignBitsOp1 == 1) break;
unsigned OutValidBits =
(TyBits - SignBitsOp0 + 1) + (TyBits - SignBitsOp1 + 1);
return OutValidBits > TyBits ? 1 : TyBits - OutValidBits + 1;
}
case Instruction::PHI: {
const PHINode *PN = cast<PHINode>(U);
unsigned NumIncomingValues = PN->getNumIncomingValues();
// Don't analyze large in-degree PHIs.
if (NumIncomingValues > 4) break;
// Unreachable blocks may have zero-operand PHI nodes.
if (NumIncomingValues == 0) break;
// Take the minimum of all incoming values. This can't infinitely loop
// because of our depth threshold.
Query RecQ = Q;
Tmp = TyBits;
for (unsigned i = 0, e = NumIncomingValues; i != e; ++i) {
if (Tmp == 1) return Tmp;
RecQ.CxtI = PN->getIncomingBlock(i)->getTerminator();
Tmp = std::min(
Tmp, ComputeNumSignBits(PN->getIncomingValue(i), Depth + 1, RecQ));
}
return Tmp;
}
case Instruction::Trunc:
// FIXME: it's tricky to do anything useful for this, but it is an
// important case for targets like X86.
break;
case Instruction::ExtractElement:
// Look through extract element. At the moment we keep this simple and
// skip tracking the specific element. But at least we might find
// information valid for all elements of the vector (for example if vector
// is sign extended, shifted, etc).
return ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
case Instruction::ShuffleVector: {
// Collect the minimum number of sign bits that are shared by every vector
// element referenced by the shuffle.
auto *Shuf = dyn_cast<ShuffleVectorInst>(U);
if (!Shuf) {
// FIXME: Add support for shufflevector constant expressions.
return 1;
}
APInt DemandedLHS, DemandedRHS;
// For undef elements, we don't know anything about the common state of
// the shuffle result.
if (!getShuffleDemandedElts(Shuf, DemandedElts, DemandedLHS, DemandedRHS))
return 1;
Tmp = std::numeric_limits<unsigned>::max();
if (!!DemandedLHS) {
const Value *LHS = Shuf->getOperand(0);
Tmp = ComputeNumSignBits(LHS, DemandedLHS, Depth + 1, Q);
}
// If we don't know anything, early out and try computeKnownBits
// fall-back.
if (Tmp == 1)
break;
if (!!DemandedRHS) {
const Value *RHS = Shuf->getOperand(1);
Tmp2 = ComputeNumSignBits(RHS, DemandedRHS, Depth + 1, Q);
Tmp = std::min(Tmp, Tmp2);
}
// If we don't know anything, early out and try computeKnownBits
// fall-back.
if (Tmp == 1)
break;
assert(Tmp <= TyBits && "Failed to determine minimum sign bits");
return Tmp;
}
case Instruction::Call: {
if (const auto *II = dyn_cast<IntrinsicInst>(U)) {
switch (II->getIntrinsicID()) {
default: break;
case Intrinsic::abs:
Tmp = ComputeNumSignBits(U->getOperand(0), Depth + 1, Q);
if (Tmp == 1) break;
// Absolute value reduces number of sign bits by at most 1.
return Tmp - 1;
}
}
}
}
}
// Finally, if we can prove that the top bits of the result are 0's or 1's,
// use this information.
// If we can examine all elements of a vector constant successfully, we're
// done (we can't do any better than that). If not, keep trying.
if (unsigned VecSignBits =
computeNumSignBitsVectorConstant(V, DemandedElts, TyBits))
return VecSignBits;
KnownBits Known(TyBits);
computeKnownBits(V, DemandedElts, Known, Depth, Q);
// If we know that the sign bit is either zero or one, determine the number of
// identical bits in the top of the input value.
return std::max(FirstAnswer, Known.countMinSignBits());
}
/// This function computes the integer multiple of Base that equals V.
/// If successful, it returns true and returns the multiple in
/// Multiple. If unsuccessful, it returns false. It looks
/// through SExt instructions only if LookThroughSExt is true.
bool llvm::ComputeMultiple(Value *V, unsigned Base, Value *&Multiple,
bool LookThroughSExt, unsigned Depth) {
assert(V && "No Value?");
assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
assert(V->getType()->isIntegerTy() && "Not integer or pointer type!");
Type *T = V->getType();
ConstantInt *CI = dyn_cast<ConstantInt>(V);
if (Base == 0)
return false;
if (Base == 1) {
Multiple = V;
return true;
}
ConstantExpr *CO = dyn_cast<ConstantExpr>(V);
Constant *BaseVal = ConstantInt::get(T, Base);
if (CO && CO == BaseVal) {
// Multiple is 1.
Multiple = ConstantInt::get(T, 1);
return true;
}
if (CI && CI->getZExtValue() % Base == 0) {
Multiple = ConstantInt::get(T, CI->getZExtValue() / Base);
return true;
}
if (Depth == MaxAnalysisRecursionDepth) return false;
Operator *I = dyn_cast<Operator>(V);
if (!I) return false;
switch (I->getOpcode()) {
default: break;
case Instruction::SExt:
if (!LookThroughSExt) return false;
// otherwise fall through to ZExt
LLVM_FALLTHROUGH;
case Instruction::ZExt:
return ComputeMultiple(I->getOperand(0), Base, Multiple,
LookThroughSExt, Depth+1);
case Instruction::Shl:
case Instruction::Mul: {
Value *Op0 = I->getOperand(0);
Value *Op1 = I->getOperand(1);
if (I->getOpcode() == Instruction::Shl) {
ConstantInt *Op1CI = dyn_cast<ConstantInt>(Op1);
if (!Op1CI) return false;
// Turn Op0 << Op1 into Op0 * 2^Op1
APInt Op1Int = Op1CI->getValue();
uint64_t BitToSet = Op1Int.getLimitedValue(Op1Int.getBitWidth() - 1);
APInt API(Op1Int.getBitWidth(), 0);
API.setBit(BitToSet);
Op1 = ConstantInt::get(V->getContext(), API);
}
Value *Mul0 = nullptr;
if (ComputeMultiple(Op0, Base, Mul0, LookThroughSExt, Depth+1)) {
if (Constant *Op1C = dyn_cast<Constant>(Op1))
if (Constant *MulC = dyn_cast<Constant>(Mul0)) {
if (Op1C->getType()->getPrimitiveSizeInBits().getFixedSize() <
MulC->getType()->getPrimitiveSizeInBits().getFixedSize())
Op1C = ConstantExpr::getZExt(Op1C, MulC->getType());
if (Op1C->getType()->getPrimitiveSizeInBits().getFixedSize() >
MulC->getType()->getPrimitiveSizeInBits().getFixedSize())
MulC = ConstantExpr::getZExt(MulC, Op1C->getType());
// V == Base * (Mul0 * Op1), so return (Mul0 * Op1)
Multiple = ConstantExpr::getMul(MulC, Op1C);
return true;
}
if (ConstantInt *Mul0CI = dyn_cast<ConstantInt>(Mul0))
if (Mul0CI->getValue() == 1) {
// V == Base * Op1, so return Op1
Multiple = Op1;
return true;
}
}
Value *Mul1 = nullptr;
if (ComputeMultiple(Op1, Base, Mul1, LookThroughSExt, Depth+1)) {
if (Constant *Op0C = dyn_cast<Constant>(Op0))
if (Constant *MulC = dyn_cast<Constant>(Mul1)) {
if (Op0C->getType()->getPrimitiveSizeInBits().getFixedSize() <
MulC->getType()->getPrimitiveSizeInBits().getFixedSize())
Op0C = ConstantExpr::getZExt(Op0C, MulC->getType());
if (Op0C->getType()->getPrimitiveSizeInBits().getFixedSize() >
MulC->getType()->getPrimitiveSizeInBits().getFixedSize())
MulC = ConstantExpr::getZExt(MulC, Op0C->getType());
// V == Base * (Mul1 * Op0), so return (Mul1 * Op0)
Multiple = ConstantExpr::getMul(MulC, Op0C);
return true;
}
if (ConstantInt *Mul1CI = dyn_cast<ConstantInt>(Mul1))
if (Mul1CI->getValue() == 1) {
// V == Base * Op0, so return Op0
Multiple = Op0;
return true;
}
}
}
}
// We could not determine if V is a multiple of Base.
return false;
}
Intrinsic::ID llvm::getIntrinsicForCallSite(const CallBase &CB,
const TargetLibraryInfo *TLI) {
const Function *F = CB.getCalledFunction();
if (!F)
return Intrinsic::not_intrinsic;
if (F->isIntrinsic())
return F->getIntrinsicID();
// We are going to infer semantics of a library function based on mapping it
// to an LLVM intrinsic. Check that the library function is available from
// this callbase and in this environment.
LibFunc Func;
if (F->hasLocalLinkage() || !TLI || !TLI->getLibFunc(CB, Func) ||
!CB.onlyReadsMemory())
return Intrinsic::not_intrinsic;
switch (Func) {
default:
break;
case LibFunc_sin:
case LibFunc_sinf:
case LibFunc_sinl:
return Intrinsic::sin;
case LibFunc_cos:
case LibFunc_cosf:
case LibFunc_cosl:
return Intrinsic::cos;
case LibFunc_exp:
case LibFunc_expf:
case LibFunc_expl:
return Intrinsic::exp;
case LibFunc_exp2:
case LibFunc_exp2f:
case LibFunc_exp2l:
return Intrinsic::exp2;
case LibFunc_log:
case LibFunc_logf:
case LibFunc_logl:
return Intrinsic::log;
case LibFunc_log10:
case LibFunc_log10f:
case LibFunc_log10l:
return Intrinsic::log10;
case LibFunc_log2:
case LibFunc_log2f:
case LibFunc_log2l:
return Intrinsic::log2;
case LibFunc_fabs:
case LibFunc_fabsf:
case LibFunc_fabsl:
return Intrinsic::fabs;
case LibFunc_fmin:
case LibFunc_fminf:
case LibFunc_fminl:
return Intrinsic::minnum;
case LibFunc_fmax:
case LibFunc_fmaxf:
case LibFunc_fmaxl:
return Intrinsic::maxnum;
case LibFunc_copysign:
case LibFunc_copysignf:
case LibFunc_copysignl:
return Intrinsic::copysign;
case LibFunc_floor:
case LibFunc_floorf:
case LibFunc_floorl:
return Intrinsic::floor;
case LibFunc_ceil:
case LibFunc_ceilf:
case LibFunc_ceill:
return Intrinsic::ceil;
case LibFunc_trunc:
case LibFunc_truncf:
case LibFunc_truncl:
return Intrinsic::trunc;
case LibFunc_rint:
case LibFunc_rintf:
case LibFunc_rintl:
return Intrinsic::rint;
case LibFunc_nearbyint:
case LibFunc_nearbyintf:
case LibFunc_nearbyintl:
return Intrinsic::nearbyint;
case LibFunc_round:
case LibFunc_roundf:
case LibFunc_roundl:
return Intrinsic::round;
case LibFunc_roundeven:
case LibFunc_roundevenf:
case LibFunc_roundevenl:
return Intrinsic::roundeven;
case LibFunc_pow:
case LibFunc_powf:
case LibFunc_powl:
return Intrinsic::pow;
case LibFunc_sqrt:
case LibFunc_sqrtf:
case LibFunc_sqrtl:
return Intrinsic::sqrt;
}
return Intrinsic::not_intrinsic;
}
/// Return true if we can prove that the specified FP value is never equal to
/// -0.0.
/// NOTE: Do not check 'nsz' here because that fast-math-flag does not guarantee
/// that a value is not -0.0. It only guarantees that -0.0 may be treated
/// the same as +0.0 in floating-point ops.
///
/// NOTE: this function will need to be revisited when we support non-default
/// rounding modes!
bool llvm::CannotBeNegativeZero(const Value *V, const TargetLibraryInfo *TLI,
unsigned Depth) {
if (auto *CFP = dyn_cast<ConstantFP>(V))
return !CFP->getValueAPF().isNegZero();
if (Depth == MaxAnalysisRecursionDepth)
return false;
auto *Op = dyn_cast<Operator>(V);
if (!Op)
return false;
// (fadd x, 0.0) is guaranteed to return +0.0, not -0.0.
if (match(Op, m_FAdd(m_Value(), m_PosZeroFP())))
return true;
// sitofp and uitofp turn into +0.0 for zero.
if (isa<SIToFPInst>(Op) || isa<UIToFPInst>(Op))
return true;
if (auto *Call = dyn_cast<CallInst>(Op)) {
Intrinsic::ID IID = getIntrinsicForCallSite(*Call, TLI);
switch (IID) {
default:
break;
// sqrt(-0.0) = -0.0, no other negative results are possible.
case Intrinsic::sqrt:
case Intrinsic::canonicalize:
return CannotBeNegativeZero(Call->getArgOperand(0), TLI, Depth + 1);
// fabs(x) != -0.0
case Intrinsic::fabs:
return true;
}
}
return false;
}
/// If \p SignBitOnly is true, test for a known 0 sign bit rather than a
/// standard ordered compare. e.g. make -0.0 olt 0.0 be true because of the sign
/// bit despite comparing equal.
static bool cannotBeOrderedLessThanZeroImpl(const Value *V,
const TargetLibraryInfo *TLI,
bool SignBitOnly,
unsigned Depth) {
// TODO: This function does not do the right thing when SignBitOnly is true
// and we're lowering to a hypothetical IEEE 754-compliant-but-evil platform
// which flips the sign bits of NaNs. See
// https://llvm.org/bugs/show_bug.cgi?id=31702.
if (const ConstantFP *CFP = dyn_cast<ConstantFP>(V)) {
return !CFP->getValueAPF().isNegative() ||
(!SignBitOnly && CFP->getValueAPF().isZero());
}
// Handle vector of constants.
if (auto *CV = dyn_cast<Constant>(V)) {
if (auto *CVFVTy = dyn_cast<FixedVectorType>(CV->getType())) {
unsigned NumElts = CVFVTy->getNumElements();
for (unsigned i = 0; i != NumElts; ++i) {
auto *CFP = dyn_cast_or_null<ConstantFP>(CV->getAggregateElement(i));
if (!CFP)
return false;
if (CFP->getValueAPF().isNegative() &&
(SignBitOnly || !CFP->getValueAPF().isZero()))
return false;
}
// All non-negative ConstantFPs.
return true;
}
}
if (Depth == MaxAnalysisRecursionDepth)
return false;
const Operator *I = dyn_cast<Operator>(V);
if (!I)
return false;
switch (I->getOpcode()) {
default:
break;
// Unsigned integers are always nonnegative.
case Instruction::UIToFP:
return true;
case Instruction::FMul:
case Instruction::FDiv:
// X * X is always non-negative or a NaN.
// X / X is always exactly 1.0 or a NaN.
if (I->getOperand(0) == I->getOperand(1) &&
(!SignBitOnly || cast<FPMathOperator>(I)->hasNoNaNs()))
return true;
LLVM_FALLTHROUGH;
case Instruction::FAdd:
case Instruction::FRem:
return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
Depth + 1) &&
cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
Depth + 1);
case Instruction::Select:
return cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
Depth + 1) &&
cannotBeOrderedLessThanZeroImpl(I->getOperand(2), TLI, SignBitOnly,
Depth + 1);
case Instruction::FPExt:
case Instruction::FPTrunc:
// Widening/narrowing never change sign.
return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
Depth + 1);
case Instruction::ExtractElement:
// Look through extract element. At the moment we keep this simple and skip
// tracking the specific element. But at least we might find information
// valid for all elements of the vector.
return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
Depth + 1);
case Instruction::Call:
const auto *CI = cast<CallInst>(I);
Intrinsic::ID IID = getIntrinsicForCallSite(*CI, TLI);
switch (IID) {
default:
break;
case Intrinsic::maxnum: {
Value *V0 = I->getOperand(0), *V1 = I->getOperand(1);
auto isPositiveNum = [&](Value *V) {
if (SignBitOnly) {
// With SignBitOnly, this is tricky because the result of
// maxnum(+0.0, -0.0) is unspecified. Just check if the operand is
// a constant strictly greater than 0.0.
const APFloat *C;
return match(V, m_APFloat(C)) &&
*C > APFloat::getZero(C->getSemantics());
}
// -0.0 compares equal to 0.0, so if this operand is at least -0.0,
// maxnum can't be ordered-less-than-zero.
return isKnownNeverNaN(V, TLI) &&
cannotBeOrderedLessThanZeroImpl(V, TLI, false, Depth + 1);
};
// TODO: This could be improved. We could also check that neither operand
// has its sign bit set (and at least 1 is not-NAN?).
return isPositiveNum(V0) || isPositiveNum(V1);
}
case Intrinsic::maximum:
return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
Depth + 1) ||
cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
Depth + 1);
case Intrinsic::minnum:
case Intrinsic::minimum:
return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
Depth + 1) &&
cannotBeOrderedLessThanZeroImpl(I->getOperand(1), TLI, SignBitOnly,
Depth + 1);
case Intrinsic::exp:
case Intrinsic::exp2:
case Intrinsic::fabs:
return true;
case Intrinsic::sqrt:
// sqrt(x) is always >= -0 or NaN. Moreover, sqrt(x) == -0 iff x == -0.
if (!SignBitOnly)
return true;
return CI->hasNoNaNs() && (CI->hasNoSignedZeros() ||
CannotBeNegativeZero(CI->getOperand(0), TLI));
case Intrinsic::powi:
if (ConstantInt *Exponent = dyn_cast<ConstantInt>(I->getOperand(1))) {
// powi(x,n) is non-negative if n is even.
if (Exponent->getBitWidth() <= 64 && Exponent->getSExtValue() % 2u == 0)
return true;
}
// TODO: This is not correct. Given that exp is an integer, here are the
// ways that pow can return a negative value:
//
// pow(x, exp) --> negative if exp is odd and x is negative.
// pow(-0, exp) --> -inf if exp is negative odd.
// pow(-0, exp) --> -0 if exp is positive odd.
// pow(-inf, exp) --> -0 if exp is negative odd.
// pow(-inf, exp) --> -inf if exp is positive odd.
//
// Therefore, if !SignBitOnly, we can return true if x >= +0 or x is NaN,
// but we must return false if x == -0. Unfortunately we do not currently
// have a way of expressing this constraint. See details in
// https://llvm.org/bugs/show_bug.cgi?id=31702.
return cannotBeOrderedLessThanZeroImpl(I->getOperand(0), TLI, SignBitOnly,
Depth + 1);
case Intrinsic::fma:
case Intrinsic::fmuladd:
// x*x+y is non-negative if y is non-negative.
return I->getOperand(0) == I->getOperand(1) &&
(!SignBitOnly || cast<FPMathOperator>(I)->hasNoNaNs()) &&
cannotBeOrderedLessThanZeroImpl(I->getOperand(2), TLI, SignBitOnly,
Depth + 1);
}
break;
}
return false;
}
bool llvm::CannotBeOrderedLessThanZero(const Value *V,
const TargetLibraryInfo *TLI) {
return cannotBeOrderedLessThanZeroImpl(V, TLI, false, 0);
}
bool llvm::SignBitMustBeZero(const Value *V, const TargetLibraryInfo *TLI) {
return cannotBeOrderedLessThanZeroImpl(V, TLI, true, 0);
}
bool llvm::isKnownNeverInfinity(const Value *V, const TargetLibraryInfo *TLI,
unsigned Depth) {
assert(V->getType()->isFPOrFPVectorTy() && "Querying for Inf on non-FP type");
// If we're told that infinities won't happen, assume they won't.
if (auto *FPMathOp = dyn_cast<FPMathOperator>(V))
if (FPMathOp->hasNoInfs())
return true;
// Handle scalar constants.
if (auto *CFP = dyn_cast<ConstantFP>(V))
return !CFP->isInfinity();
if (Depth == MaxAnalysisRecursionDepth)
return false;
if (auto *Inst = dyn_cast<Instruction>(V)) {
switch (Inst->getOpcode()) {
case Instruction::Select: {
return isKnownNeverInfinity(Inst->getOperand(1), TLI, Depth + 1) &&
isKnownNeverInfinity(Inst->getOperand(2), TLI, Depth + 1);
}
case Instruction::SIToFP:
case Instruction::UIToFP: {
// Get width of largest magnitude integer (remove a bit if signed).
// This still works for a signed minimum value because the largest FP
// value is scaled by some fraction close to 2.0 (1.0 + 0.xxxx).
int IntSize = Inst->getOperand(0)->getType()->getScalarSizeInBits();
if (Inst->getOpcode() == Instruction::SIToFP)
--IntSize;
// If the exponent of the largest finite FP value can hold the largest
// integer, the result of the cast must be finite.
Type *FPTy = Inst->getType()->getScalarType();
return ilogb(APFloat::getLargest(FPTy->getFltSemantics())) >= IntSize;
}
default:
break;
}
}
// try to handle fixed width vector constants
auto *VFVTy = dyn_cast<FixedVectorType>(V->getType());
if (VFVTy && isa<Constant>(V)) {
// For vectors, verify that each element is not infinity.
unsigned NumElts = VFVTy->getNumElements();
for (unsigned i = 0; i != NumElts; ++i) {
Constant *Elt = cast<Constant>(V)->getAggregateElement(i);
if (!Elt)
return false;
if (isa<UndefValue>(Elt))
continue;
auto *CElt = dyn_cast<ConstantFP>(Elt);
if (!CElt || CElt->isInfinity())
return false;
}
// All elements were confirmed non-infinity or undefined.
return true;
}
// was not able to prove that V never contains infinity
return false;
}
bool llvm::isKnownNeverNaN(const Value *V, const TargetLibraryInfo *TLI,
unsigned Depth) {
assert(V->getType()->isFPOrFPVectorTy() && "Querying for NaN on non-FP type");
// If we're told that NaNs won't happen, assume they won't.
if (auto *FPMathOp = dyn_cast<FPMathOperator>(V))
if (FPMathOp->hasNoNaNs())
return true;
// Handle scalar constants.
if (auto *CFP = dyn_cast<ConstantFP>(V))
return !CFP->isNaN();
if (Depth == MaxAnalysisRecursionDepth)
return false;
if (auto *Inst = dyn_cast<Instruction>(V)) {
switch (Inst->getOpcode()) {
case Instruction::FAdd:
case Instruction::FSub:
// Adding positive and negative infinity produces NaN.
return isKnownNeverNaN(Inst->getOperand(0), TLI, Depth + 1) &&
isKnownNeverNaN(Inst->getOperand(1), TLI, Depth + 1) &&
(isKnownNeverInfinity(Inst->getOperand(0), TLI, Depth + 1) ||
isKnownNeverInfinity(Inst->getOperand(1), TLI, Depth + 1));
case Instruction::FMul:
// Zero multiplied with infinity produces NaN.
// FIXME: If neither side can be zero fmul never produces NaN.
return isKnownNeverNaN(Inst->getOperand(0), TLI, Depth + 1) &&
isKnownNeverInfinity(Inst->getOperand(0), TLI, Depth + 1) &&
isKnownNeverNaN(Inst->getOperand(1), TLI, Depth + 1) &&
isKnownNeverInfinity(Inst->getOperand(1), TLI, Depth + 1);
case Instruction::FDiv:
case Instruction::FRem:
// FIXME: Only 0/0, Inf/Inf, Inf REM x and x REM 0 produce NaN.
return false;
case Instruction::Select: {
return isKnownNeverNaN(Inst->getOperand(1), TLI, Depth + 1) &&
isKnownNeverNaN(Inst->getOperand(2), TLI, Depth + 1);
}
case Instruction::SIToFP:
case Instruction::UIToFP:
return true;
case Instruction::FPTrunc:
case Instruction::FPExt:
return isKnownNeverNaN(Inst->getOperand(0), TLI, Depth + 1);
default:
break;
}
}
if (const auto *II = dyn_cast<IntrinsicInst>(V)) {
switch (II->getIntrinsicID()) {
case Intrinsic::canonicalize:
case Intrinsic::fabs:
case Intrinsic::copysign:
case Intrinsic::exp:
case Intrinsic::exp2:
case Intrinsic::floor:
case Intrinsic::ceil:
case Intrinsic::trunc:
case Intrinsic::rint:
case Intrinsic::nearbyint:
case Intrinsic::round:
case Intrinsic::roundeven:
return isKnownNeverNaN(II->getArgOperand(0), TLI, Depth + 1);
case Intrinsic::sqrt:
return isKnownNeverNaN(II->getArgOperand(0), TLI, Depth + 1) &&
CannotBeOrderedLessThanZero(II->getArgOperand(0), TLI);
case Intrinsic::minnum:
case Intrinsic::maxnum:
// If either operand is not NaN, the result is not NaN.
return isKnownNeverNaN(II->getArgOperand(0), TLI, Depth + 1) ||
isKnownNeverNaN(II->getArgOperand(1), TLI, Depth + 1);
default:
return false;
}
}
// Try to handle fixed width vector constants
auto *VFVTy = dyn_cast<FixedVectorType>(V->getType());
if (VFVTy && isa<Constant>(V)) {
// For vectors, verify that each element is not NaN.
unsigned NumElts = VFVTy->getNumElements();
for (unsigned i = 0; i != NumElts; ++i) {
Constant *Elt = cast<Constant>(V)->getAggregateElement(i);
if (!Elt)
return false;
if (isa<UndefValue>(Elt))
continue;
auto *CElt = dyn_cast<ConstantFP>(Elt);
if (!CElt || CElt->isNaN())
return false;
}
// All elements were confirmed not-NaN or undefined.
return true;
}
// Was not able to prove that V never contains NaN
return false;
}
Value *llvm::isBytewiseValue(Value *V, const DataLayout &DL) {
// All byte-wide stores are splatable, even of arbitrary variables.
if (V->getType()->isIntegerTy(8))
return V;
LLVMContext &Ctx = V->getContext();
// Undef don't care.
auto *UndefInt8 = UndefValue::get(Type::getInt8Ty(Ctx));
if (isa<UndefValue>(V))
return UndefInt8;
// Return Undef for zero-sized type.
if (!DL.getTypeStoreSize(V->getType()).isNonZero())
return UndefInt8;
Constant *C = dyn_cast<Constant>(V);
if (!C) {
// Conceptually, we could handle things like:
// %a = zext i8 %X to i16
// %b = shl i16 %a, 8
// %c = or i16 %a, %b
// but until there is an example that actually needs this, it doesn't seem
// worth worrying about.
return nullptr;
}
// Handle 'null' ConstantArrayZero etc.
if (C->isNullValue())
return Constant::getNullValue(Type::getInt8Ty(Ctx));
// Constant floating-point values can be handled as integer values if the
// corresponding integer value is "byteable". An important case is 0.0.
if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) {
Type *Ty = nullptr;
if (CFP->getType()->isHalfTy())
Ty = Type::getInt16Ty(Ctx);
else if (CFP->getType()->isFloatTy())
Ty = Type::getInt32Ty(Ctx);
else if (CFP->getType()->isDoubleTy())
Ty = Type::getInt64Ty(Ctx);
// Don't handle long double formats, which have strange constraints.
return Ty ? isBytewiseValue(ConstantExpr::getBitCast(CFP, Ty), DL)
: nullptr;
}
// We can handle constant integers that are multiple of 8 bits.
if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
if (CI->getBitWidth() % 8 == 0) {
assert(CI->getBitWidth() > 8 && "8 bits should be handled above!");
if (!CI->getValue().isSplat(8))
return nullptr;
return ConstantInt::get(Ctx, CI->getValue().trunc(8));
}
}
if (auto *CE = dyn_cast<ConstantExpr>(C)) {
if (CE->getOpcode() == Instruction::IntToPtr) {
if (auto *PtrTy = dyn_cast<PointerType>(CE->getType())) {
unsigned BitWidth = DL.getPointerSizeInBits(PtrTy->getAddressSpace());
return isBytewiseValue(
ConstantExpr::getIntegerCast(CE->getOperand(0),
Type::getIntNTy(Ctx, BitWidth), false),
DL);
}
}
}
auto Merge = [&](Value *LHS, Value *RHS) -> Value * {
if (LHS == RHS)
return LHS;
if (!LHS || !RHS)
return nullptr;
if (LHS == UndefInt8)
return RHS;
if (RHS == UndefInt8)
return LHS;
return nullptr;
};
if (ConstantDataSequential *CA = dyn_cast<ConstantDataSequential>(C)) {
Value *Val = UndefInt8;
for (unsigned I = 0, E = CA->getNumElements(); I != E; ++I)
if (!(Val = Merge(Val, isBytewiseValue(CA->getElementAsConstant(I), DL))))
return nullptr;
return Val;
}
if (isa<ConstantAggregate>(C)) {
Value *Val = UndefInt8;
for (unsigned I = 0, E = C->getNumOperands(); I != E; ++I)
if (!(Val = Merge(Val, isBytewiseValue(C->getOperand(I), DL))))
return nullptr;
return Val;
}
// Don't try to handle the handful of other constants.
return nullptr;
}
// This is the recursive version of BuildSubAggregate. It takes a few different
// arguments. Idxs is the index within the nested struct From that we are
// looking at now (which is of type IndexedType). IdxSkip is the number of
// indices from Idxs that should be left out when inserting into the resulting
// struct. To is the result struct built so far, new insertvalue instructions
// build on that.
static Value *BuildSubAggregate(Value *From, Value* To, Type *IndexedType,
SmallVectorImpl<unsigned> &Idxs,
unsigned IdxSkip,
Instruction *InsertBefore) {
StructType *STy = dyn_cast<StructType>(IndexedType);
if (STy) {
// Save the original To argument so we can modify it
Value *OrigTo = To;
// General case, the type indexed by Idxs is a struct
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
// Process each struct element recursively
Idxs.push_back(i);
Value *PrevTo = To;
To = BuildSubAggregate(From, To, STy->getElementType(i), Idxs, IdxSkip,
InsertBefore);
Idxs.pop_back();
if (!To) {
// Couldn't find any inserted value for this index? Cleanup
while (PrevTo != OrigTo) {
InsertValueInst* Del = cast<InsertValueInst>(PrevTo);
PrevTo = Del->getAggregateOperand();
Del->eraseFromParent();
}
// Stop processing elements
break;
}
}
// If we successfully found a value for each of our subaggregates
if (To)
return To;
}
// Base case, the type indexed by SourceIdxs is not a struct, or not all of
// the struct's elements had a value that was inserted directly. In the latter
// case, perhaps we can't determine each of the subelements individually, but
// we might be able to find the complete struct somewhere.
// Find the value that is at that particular spot
Value *V = FindInsertedValue(From, Idxs);
if (!V)
return nullptr;
// Insert the value in the new (sub) aggregate
return InsertValueInst::Create(To, V, makeArrayRef(Idxs).slice(IdxSkip),
"tmp", InsertBefore);
}
// This helper takes a nested struct and extracts a part of it (which is again a
// struct) into a new value. For example, given the struct:
// { a, { b, { c, d }, e } }
// and the indices "1, 1" this returns
// { c, d }.
//
// It does this by inserting an insertvalue for each element in the resulting
// struct, as opposed to just inserting a single struct. This will only work if
// each of the elements of the substruct are known (ie, inserted into From by an
// insertvalue instruction somewhere).
//
// All inserted insertvalue instructions are inserted before InsertBefore
static Value *BuildSubAggregate(Value *From, ArrayRef<unsigned> idx_range,
Instruction *InsertBefore) {
assert(InsertBefore && "Must have someplace to insert!");
Type *IndexedType = ExtractValueInst::getIndexedType(From->getType(),
idx_range);
Value *To = UndefValue::get(IndexedType);
SmallVector<unsigned, 10> Idxs(idx_range.begin(), idx_range.end());
unsigned IdxSkip = Idxs.size();
return BuildSubAggregate(From, To, IndexedType, Idxs, IdxSkip, InsertBefore);
}
/// Given an aggregate and a sequence of indices, see if the scalar value
/// indexed is already around as a register, for example if it was inserted
/// directly into the aggregate.
///
/// If InsertBefore is not null, this function will duplicate (modified)
/// insertvalues when a part of a nested struct is extracted.
Value *llvm::FindInsertedValue(Value *V, ArrayRef<unsigned> idx_range,
Instruction *InsertBefore) {
// Nothing to index? Just return V then (this is useful at the end of our
// recursion).
if (idx_range.empty())
return V;
// We have indices, so V should have an indexable type.
assert((V->getType()->isStructTy() || V->getType()->isArrayTy()) &&
"Not looking at a struct or array?");
assert(ExtractValueInst::getIndexedType(V->getType(), idx_range) &&
"Invalid indices for type?");
if (Constant *C = dyn_cast<Constant>(V)) {
C = C->getAggregateElement(idx_range[0]);
if (!C) return nullptr;
return FindInsertedValue(C, idx_range.slice(1), InsertBefore);
}
if (InsertValueInst *I = dyn_cast<InsertValueInst>(V)) {
// Loop the indices for the insertvalue instruction in parallel with the
// requested indices
const unsigned *req_idx = idx_range.begin();
for (const unsigned *i = I->idx_begin(), *e = I->idx_end();
i != e; ++i, ++req_idx) {
if (req_idx == idx_range.end()) {
// We can't handle this without inserting insertvalues
if (!InsertBefore)
return nullptr;
// The requested index identifies a part of a nested aggregate. Handle
// this specially. For example,
// %A = insertvalue { i32, {i32, i32 } } undef, i32 10, 1, 0
// %B = insertvalue { i32, {i32, i32 } } %A, i32 11, 1, 1
// %C = extractvalue {i32, { i32, i32 } } %B, 1
// This can be changed into
// %A = insertvalue {i32, i32 } undef, i32 10, 0
// %C = insertvalue {i32, i32 } %A, i32 11, 1
// which allows the unused 0,0 element from the nested struct to be
// removed.
return BuildSubAggregate(V, makeArrayRef(idx_range.begin(), req_idx),
InsertBefore);
}
// This insert value inserts something else than what we are looking for.
// See if the (aggregate) value inserted into has the value we are
// looking for, then.
if (*req_idx != *i)
return FindInsertedValue(I->getAggregateOperand(), idx_range,
InsertBefore);
}
// If we end up here, the indices of the insertvalue match with those
// requested (though possibly only partially). Now we recursively look at
// the inserted value, passing any remaining indices.
return FindInsertedValue(I->getInsertedValueOperand(),
makeArrayRef(req_idx, idx_range.end()),
InsertBefore);
}
if (ExtractValueInst *I = dyn_cast<ExtractValueInst>(V)) {
// If we're extracting a value from an aggregate that was extracted from
// something else, we can extract from that something else directly instead.
// However, we will need to chain I's indices with the requested indices.
// Calculate the number of indices required
unsigned size = I->getNumIndices() + idx_range.size();
// Allocate some space to put the new indices in
SmallVector<unsigned, 5> Idxs;
Idxs.reserve(size);
// Add indices from the extract value instruction
Idxs.append(I->idx_begin(), I->idx_end());
// Add requested indices
Idxs.append(idx_range.begin(), idx_range.end());
assert(Idxs.size() == size
&& "Number of indices added not correct?");
return FindInsertedValue(I->getAggregateOperand(), Idxs, InsertBefore);
}
// Otherwise, we don't know (such as, extracting from a function return value
// or load instruction)
return nullptr;
}
bool llvm::isGEPBasedOnPointerToString(const GEPOperator *GEP,
unsigned CharSize) {
// Make sure the GEP has exactly three arguments.
if (GEP->getNumOperands() != 3)
return false;
// Make sure the index-ee is a pointer to array of \p CharSize integers.
// CharSize.
ArrayType *AT = dyn_cast<ArrayType>(GEP->getSourceElementType());
if (!AT || !AT->getElementType()->isIntegerTy(CharSize))
return false;
// Check to make sure that the first operand of the GEP is an integer and
// has value 0 so that we are sure we're indexing into the initializer.
const ConstantInt *FirstIdx = dyn_cast<ConstantInt>(GEP->getOperand(1));
if (!FirstIdx || !FirstIdx->isZero())
return false;
return true;
}
bool llvm::getConstantDataArrayInfo(const Value *V,
ConstantDataArraySlice &Slice,
unsigned ElementSize, uint64_t Offset) {
assert(V);
// Look through bitcast instructions and geps.
V = V->stripPointerCasts();
// If the value is a GEP instruction or constant expression, treat it as an
// offset.
if (const GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
// The GEP operator should be based on a pointer to string constant, and is
// indexing into the string constant.
if (!isGEPBasedOnPointerToString(GEP, ElementSize))
return false;
// If the second index isn't a ConstantInt, then this is a variable index
// into the array. If this occurs, we can't say anything meaningful about
// the string.
uint64_t StartIdx = 0;
if (const ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(2)))
StartIdx = CI->getZExtValue();
else
return false;
return getConstantDataArrayInfo(GEP->getOperand(0), Slice, ElementSize,
StartIdx + Offset);
}
// The GEP instruction, constant or instruction, must reference a global
// variable that is a constant and is initialized. The referenced constant
// initializer is the array that we'll use for optimization.
const GlobalVariable *GV = dyn_cast<GlobalVariable>(V);
if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer())
return false;
const ConstantDataArray *Array;
ArrayType *ArrayTy;
if (GV->getInitializer()->isNullValue()) {
Type *GVTy = GV->getValueType();
if ( (ArrayTy = dyn_cast<ArrayType>(GVTy)) ) {
// A zeroinitializer for the array; there is no ConstantDataArray.
Array = nullptr;
} else {
const DataLayout &DL = GV->getParent()->getDataLayout();
uint64_t SizeInBytes = DL.getTypeStoreSize(GVTy).getFixedSize();
uint64_t Length = SizeInBytes / (ElementSize / 8);
if (Length <= Offset)
return false;
Slice.Array = nullptr;
Slice.Offset = 0;
Slice.Length = Length - Offset;
return true;
}
} else {
// This must be a ConstantDataArray.
Array = dyn_cast<ConstantDataArray>(GV->getInitializer());
if (!Array)
return false;
ArrayTy = Array->getType();
}
if (!ArrayTy->getElementType()->isIntegerTy(ElementSize))
return false;
uint64_t NumElts = ArrayTy->getArrayNumElements();
if (Offset > NumElts)
return false;
Slice.Array = Array;
Slice.Offset = Offset;
Slice.Length = NumElts - Offset;
return true;
}
/// This function computes the length of a null-terminated C string pointed to
/// by V. If successful, it returns true and returns the string in Str.
/// If unsuccessful, it returns false.
bool llvm::getConstantStringInfo(const Value *V, StringRef &Str,
uint64_t Offset, bool TrimAtNul) {
ConstantDataArraySlice Slice;
if (!getConstantDataArrayInfo(V, Slice, 8, Offset))
return false;
if (Slice.Array == nullptr) {
if (TrimAtNul) {
Str = StringRef();
return true;
}
if (Slice.Length == 1) {
Str = StringRef("", 1);
return true;
}
// We cannot instantiate a StringRef as we do not have an appropriate string
// of 0s at hand.
return false;
}
// Start out with the entire array in the StringRef.
Str = Slice.Array->getAsString();
// Skip over 'offset' bytes.
Str = Str.substr(Slice.Offset);
if (TrimAtNul) {
// Trim off the \0 and anything after it. If the array is not nul
// terminated, we just return the whole end of string. The client may know
// some other way that the string is length-bound.
Str = Str.substr(0, Str.find('\0'));
}
return true;
}
// These next two are very similar to the above, but also look through PHI
// nodes.
// TODO: See if we can integrate these two together.
/// If we can compute the length of the string pointed to by
/// the specified pointer, return 'len+1'. If we can't, return 0.
static uint64_t GetStringLengthH(const Value *V,
SmallPtrSetImpl<const PHINode*> &PHIs,
unsigned CharSize) {
// Look through noop bitcast instructions.
V = V->stripPointerCasts();
// If this is a PHI node, there are two cases: either we have already seen it
// or we haven't.
if (const PHINode *PN = dyn_cast<PHINode>(V)) {
if (!PHIs.insert(PN).second)
return ~0ULL; // already in the set.
// If it was new, see if all the input strings are the same length.
uint64_t LenSoFar = ~0ULL;
for (Value *IncValue : PN->incoming_values()) {
uint64_t Len = GetStringLengthH(IncValue, PHIs, CharSize);
if (Len == 0) return 0; // Unknown length -> unknown.
if (Len == ~0ULL) continue;
if (Len != LenSoFar && LenSoFar != ~0ULL)
return 0; // Disagree -> unknown.
LenSoFar = Len;
}
// Success, all agree.
return LenSoFar;
}
// strlen(select(c,x,y)) -> strlen(x) ^ strlen(y)
if (const SelectInst *SI = dyn_cast<SelectInst>(V)) {
uint64_t Len1 = GetStringLengthH(SI->getTrueValue(), PHIs, CharSize);
if (Len1 == 0) return 0;
uint64_t Len2 = GetStringLengthH(SI->getFalseValue(), PHIs, CharSize);
if (Len2 == 0) return 0;
if (Len1 == ~0ULL) return Len2;
if (Len2 == ~0ULL) return Len1;
if (Len1 != Len2) return 0;
return Len1;
}
// Otherwise, see if we can read the string.
ConstantDataArraySlice Slice;
if (!getConstantDataArrayInfo(V, Slice, CharSize))
return 0;
if (Slice.Array == nullptr)
return 1;
// Search for nul characters
unsigned NullIndex = 0;
for (unsigned E = Slice.Length; NullIndex < E; ++NullIndex) {
if (Slice.Array->getElementAsInteger(Slice.Offset + NullIndex) == 0)
break;
}
return NullIndex + 1;
}
/// If we can compute the length of the string pointed to by
/// the specified pointer, return 'len+1'. If we can't, return 0.
uint64_t llvm::GetStringLength(const Value *V, unsigned CharSize) {
if (!V->getType()->isPointerTy())
return 0;
SmallPtrSet<const PHINode*, 32> PHIs;
uint64_t Len = GetStringLengthH(V, PHIs, CharSize);
// If Len is ~0ULL, we had an infinite phi cycle: this is dead code, so return
// an empty string as a length.
return Len == ~0ULL ? 1 : Len;
}
const Value *
llvm::getArgumentAliasingToReturnedPointer(const CallBase *Call,
bool MustPreserveNullness) {
assert(Call &&
"getArgumentAliasingToReturnedPointer only works on nonnull calls");
if (const Value *RV = Call->getReturnedArgOperand())
return RV;
// This can be used only as a aliasing property.
if (isIntrinsicReturningPointerAliasingArgumentWithoutCapturing(
Call, MustPreserveNullness))
return Call->getArgOperand(0);
return nullptr;
}
bool llvm::isIntrinsicReturningPointerAliasingArgumentWithoutCapturing(
const CallBase *Call, bool MustPreserveNullness) {
switch (Call->getIntrinsicID()) {
case Intrinsic::launder_invariant_group:
case Intrinsic::strip_invariant_group:
case Intrinsic::aarch64_irg:
case Intrinsic::aarch64_tagp:
return true;
case Intrinsic::ptrmask:
return !MustPreserveNullness;
default:
return false;
}
}
/// \p PN defines a loop-variant pointer to an object. Check if the
/// previous iteration of the loop was referring to the same object as \p PN.
static bool isSameUnderlyingObjectInLoop(const PHINode *PN,
const LoopInfo *LI) {
// Find the loop-defined value.
Loop *L = LI->getLoopFor(PN->getParent());
if (PN->getNumIncomingValues() != 2)
return true;
// Find the value from previous iteration.
auto *PrevValue = dyn_cast<Instruction>(PN->getIncomingValue(0));
if (!PrevValue || LI->getLoopFor(PrevValue->getParent()) != L)
PrevValue = dyn_cast<Instruction>(PN->getIncomingValue(1));
if (!PrevValue || LI->getLoopFor(PrevValue->getParent()) != L)
return true;
// If a new pointer is loaded in the loop, the pointer references a different
// object in every iteration. E.g.:
// for (i)
// int *p = a[i];
// ...
if (auto *Load = dyn_cast<LoadInst>(PrevValue))
if (!L->isLoopInvariant(Load->getPointerOperand()))
return false;
return true;
}
const Value *llvm::getUnderlyingObject(const Value *V, unsigned MaxLookup) {
if (!V->getType()->isPointerTy())
return V;
for (unsigned Count = 0; MaxLookup == 0 || Count < MaxLookup; ++Count) {
if (auto *GEP = dyn_cast<GEPOperator>(V)) {
V = GEP->getPointerOperand();
} else if (Operator::getOpcode(V) == Instruction::BitCast ||
Operator::getOpcode(V) == Instruction::AddrSpaceCast) {
V = cast<Operator>(V)->getOperand(0);
if (!V->getType()->isPointerTy())
return V;
} else if (auto *GA = dyn_cast<GlobalAlias>(V)) {
if (GA->isInterposable())
return V;
V = GA->getAliasee();
} else {
if (auto *PHI = dyn_cast<PHINode>(V)) {
// Look through single-arg phi nodes created by LCSSA.
if (PHI->getNumIncomingValues() == 1) {
V = PHI->getIncomingValue(0);
continue;
}
} else if (auto *Call = dyn_cast<CallBase>(V)) {
// CaptureTracking can know about special capturing properties of some
// intrinsics like launder.invariant.group, that can't be expressed with
// the attributes, but have properties like returning aliasing pointer.
// Because some analysis may assume that nocaptured pointer is not
// returned from some special intrinsic (because function would have to
// be marked with returns attribute), it is crucial to use this function
// because it should be in sync with CaptureTracking. Not using it may
// cause weird miscompilations where 2 aliasing pointers are assumed to
// noalias.
if (auto *RP = getArgumentAliasingToReturnedPointer(Call, false)) {
V = RP;
continue;
}
}
return V;
}
assert(V->getType()->isPointerTy() && "Unexpected operand type!");
}
return V;
}
void llvm::getUnderlyingObjects(const Value *V,
SmallVectorImpl<const Value *> &Objects,
LoopInfo *LI, unsigned MaxLookup) {
SmallPtrSet<const Value *, 4> Visited;
SmallVector<const Value *, 4> Worklist;
Worklist.push_back(V);
do {
const Value *P = Worklist.pop_back_val();
P = getUnderlyingObject(P, MaxLookup);
if (!Visited.insert(P).second)
continue;
if (auto *SI = dyn_cast<SelectInst>(P)) {
Worklist.push_back(SI->getTrueValue());
Worklist.push_back(SI->getFalseValue());
continue;
}
if (auto *PN = dyn_cast<PHINode>(P)) {
// If this PHI changes the underlying object in every iteration of the
// loop, don't look through it. Consider:
// int **A;
// for (i) {
// Prev = Curr; // Prev = PHI (Prev_0, Curr)
// Curr = A[i];
// *Prev, *Curr;
//
// Prev is tracking Curr one iteration behind so they refer to different
// underlying objects.
if (!LI || !LI->isLoopHeader(PN->getParent()) ||
isSameUnderlyingObjectInLoop(PN, LI))
append_range(Worklist, PN->incoming_values());
continue;
}
Objects.push_back(P);
} while (!Worklist.empty());
}
/// This is the function that does the work of looking through basic
/// ptrtoint+arithmetic+inttoptr sequences.
static const Value *getUnderlyingObjectFromInt(const Value *V) {
do {
if (const Operator *U = dyn_cast<Operator>(V)) {
// If we find a ptrtoint, we can transfer control back to the
// regular getUnderlyingObjectFromInt.
if (U->getOpcode() == Instruction::PtrToInt)
return U->getOperand(0);
// If we find an add of a constant, a multiplied value, or a phi, it's
// likely that the other operand will lead us to the base
// object. We don't have to worry about the case where the
// object address is somehow being computed by the multiply,
// because our callers only care when the result is an
// identifiable object.
if (U->getOpcode() != Instruction::Add ||
(!isa<ConstantInt>(U->getOperand(1)) &&
Operator::getOpcode(U->getOperand(1)) != Instruction::Mul &&
!isa<PHINode>(U->getOperand(1))))
return V;
V = U->getOperand(0);
} else {
return V;
}
assert(V->getType()->isIntegerTy() && "Unexpected operand type!");
} while (true);
}
/// This is a wrapper around getUnderlyingObjects and adds support for basic
/// ptrtoint+arithmetic+inttoptr sequences.
/// It returns false if unidentified object is found in getUnderlyingObjects.
bool llvm::getUnderlyingObjectsForCodeGen(const Value *V,
SmallVectorImpl<Value *> &Objects) {
SmallPtrSet<const Value *, 16> Visited;
SmallVector<const Value *, 4> Working(1, V);
do {
V = Working.pop_back_val();
SmallVector<const Value *, 4> Objs;
getUnderlyingObjects(V, Objs);
for (const Value *V : Objs) {
if (!Visited.insert(V).second)
continue;
if (Operator::getOpcode(V) == Instruction::IntToPtr) {
const Value *O =
getUnderlyingObjectFromInt(cast<User>(V)->getOperand(0));
if (O->getType()->isPointerTy()) {
Working.push_back(O);
continue;
}
}
// If getUnderlyingObjects fails to find an identifiable object,
// getUnderlyingObjectsForCodeGen also fails for safety.
if (!isIdentifiedObject(V)) {
Objects.clear();
return false;
}
Objects.push_back(const_cast<Value *>(V));
}
} while (!Working.empty());
return true;
}
AllocaInst *llvm::findAllocaForValue(Value *V, bool OffsetZero) {
AllocaInst *Result = nullptr;
SmallPtrSet<Value *, 4> Visited;
SmallVector<Value *, 4> Worklist;
auto AddWork = [&](Value *V) {
if (Visited.insert(V).second)
Worklist.push_back(V);
};
AddWork(V);
do {
V = Worklist.pop_back_val();
assert(Visited.count(V));
if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
if (Result && Result != AI)
return nullptr;
Result = AI;
} else if (CastInst *CI = dyn_cast<CastInst>(V)) {
AddWork(CI->getOperand(0));
} else if (PHINode *PN = dyn_cast<PHINode>(V)) {
for (Value *IncValue : PN->incoming_values())
AddWork(IncValue);
} else if (auto *SI = dyn_cast<SelectInst>(V)) {
AddWork(SI->getTrueValue());
AddWork(SI->getFalseValue());
} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) {
if (OffsetZero && !GEP->hasAllZeroIndices())
return nullptr;
AddWork(GEP->getPointerOperand());
} else {
return nullptr;
}
} while (!Worklist.empty());
return Result;
}
static bool onlyUsedByLifetimeMarkersOrDroppableInstsHelper(
const Value *V, bool AllowLifetime, bool AllowDroppable) {
for (const User *U : V->users()) {
const IntrinsicInst *II = dyn_cast<IntrinsicInst>(U);
if (!II)
return false;
if (AllowLifetime && II->isLifetimeStartOrEnd())
continue;
if (AllowDroppable && II->isDroppable())
continue;
return false;
}
return true;
}
bool llvm::onlyUsedByLifetimeMarkers(const Value *V) {
return onlyUsedByLifetimeMarkersOrDroppableInstsHelper(
V, /* AllowLifetime */ true, /* AllowDroppable */ false);
}
bool llvm::onlyUsedByLifetimeMarkersOrDroppableInsts(const Value *V) {
return onlyUsedByLifetimeMarkersOrDroppableInstsHelper(
V, /* AllowLifetime */ true, /* AllowDroppable */ true);
}
bool llvm::mustSuppressSpeculation(const LoadInst &LI) {
if (!LI.isUnordered())
return true;
const Function &F = *LI.getFunction();
// Speculative load may create a race that did not exist in the source.
return F.hasFnAttribute(Attribute::SanitizeThread) ||
// Speculative load may load data from dirty regions.
F.hasFnAttribute(Attribute::SanitizeAddress) ||
F.hasFnAttribute(Attribute::SanitizeHWAddress);
}
bool llvm::isSafeToSpeculativelyExecute(const Value *V,
const Instruction *CtxI,
const DominatorTree *DT,
const TargetLibraryInfo *TLI) {
const Operator *Inst = dyn_cast<Operator>(V);
if (!Inst)
return false;
for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i)
if (Constant *C = dyn_cast<Constant>(Inst->getOperand(i)))
if (C->canTrap())
return false;
switch (Inst->getOpcode()) {
default:
return true;
case Instruction::UDiv:
case Instruction::URem: {
// x / y is undefined if y == 0.
const APInt *V;
if (match(Inst->getOperand(1), m_APInt(V)))
return *V != 0;
return false;
}
case Instruction::SDiv:
case Instruction::SRem: {
// x / y is undefined if y == 0 or x == INT_MIN and y == -1
const APInt *Numerator, *Denominator;
if (!match(Inst->getOperand(1), m_APInt(Denominator)))
return false;
// We cannot hoist this division if the denominator is 0.
if (*Denominator == 0)
return false;
// It's safe to hoist if the denominator is not 0 or -1.
if (!Denominator->isAllOnesValue())
return true;
// At this point we know that the denominator is -1. It is safe to hoist as
// long we know that the numerator is not INT_MIN.
if (match(Inst->getOperand(0), m_APInt(Numerator)))
return !Numerator->isMinSignedValue();
// The numerator *might* be MinSignedValue.
return false;
}
case Instruction::Load: {
const LoadInst *LI = cast<LoadInst>(Inst);
if (mustSuppressSpeculation(*LI))
return false;
const DataLayout &DL = LI->getModule()->getDataLayout();
return isDereferenceableAndAlignedPointer(
LI->getPointerOperand(), LI->getType(), MaybeAlign(LI->getAlignment()),
DL, CtxI, DT, TLI);
}
case Instruction::Call: {
auto *CI = cast<const CallInst>(Inst);
const Function *Callee = CI->getCalledFunction();
// The called function could have undefined behavior or side-effects, even
// if marked readnone nounwind.
return Callee && Callee->isSpeculatable();
}
case Instruction::VAArg:
case Instruction::Alloca:
case Instruction::Invoke:
case Instruction::CallBr:
case Instruction::PHI:
case Instruction::Store:
case Instruction::Ret:
case Instruction::Br:
case Instruction::IndirectBr:
case Instruction::Switch:
case Instruction::Unreachable:
case Instruction::Fence:
case Instruction::AtomicRMW:
case Instruction::AtomicCmpXchg:
case Instruction::LandingPad:
case Instruction::Resume:
case Instruction::CatchSwitch:
case Instruction::CatchPad:
case Instruction::CatchRet:
case Instruction::CleanupPad:
case Instruction::CleanupRet:
return false; // Misc instructions which have effects
}
}
bool llvm::mayBeMemoryDependent(const Instruction &I) {
return I.mayReadOrWriteMemory() || !isSafeToSpeculativelyExecute(&I);
}
/// Convert ConstantRange OverflowResult into ValueTracking OverflowResult.
static OverflowResult mapOverflowResult(ConstantRange::OverflowResult OR) {
switch (OR) {
case ConstantRange::OverflowResult::MayOverflow:
return OverflowResult::MayOverflow;
case ConstantRange::OverflowResult::AlwaysOverflowsLow:
return OverflowResult::AlwaysOverflowsLow;
case ConstantRange::OverflowResult::AlwaysOverflowsHigh:
return OverflowResult::AlwaysOverflowsHigh;
case ConstantRange::OverflowResult::NeverOverflows:
return OverflowResult::NeverOverflows;
}
llvm_unreachable("Unknown OverflowResult");
}
/// Combine constant ranges from computeConstantRange() and computeKnownBits().
static ConstantRange computeConstantRangeIncludingKnownBits(
const Value *V, bool ForSigned, const DataLayout &DL, unsigned Depth,
AssumptionCache *AC, const Instruction *CxtI, const DominatorTree *DT,
OptimizationRemarkEmitter *ORE = nullptr, bool UseInstrInfo = true) {
KnownBits Known = computeKnownBits(
V, DL, Depth, AC, CxtI, DT, ORE, UseInstrInfo);
ConstantRange CR1 = ConstantRange::fromKnownBits(Known, ForSigned);
ConstantRange CR2 = computeConstantRange(V, UseInstrInfo);
ConstantRange::PreferredRangeType RangeType =
ForSigned ? ConstantRange::Signed : ConstantRange::Unsigned;
return CR1.intersectWith(CR2, RangeType);
}
OverflowResult llvm::computeOverflowForUnsignedMul(
const Value *LHS, const Value *RHS, const DataLayout &DL,
AssumptionCache *AC, const Instruction *CxtI, const DominatorTree *DT,
bool UseInstrInfo) {
KnownBits LHSKnown = computeKnownBits(LHS, DL, /*Depth=*/0, AC, CxtI, DT,
nullptr, UseInstrInfo);
KnownBits RHSKnown = computeKnownBits(RHS, DL, /*Depth=*/0, AC, CxtI, DT,
nullptr, UseInstrInfo);
ConstantRange LHSRange = ConstantRange::fromKnownBits(LHSKnown, false);
ConstantRange RHSRange = ConstantRange::fromKnownBits(RHSKnown, false);
return mapOverflowResult(LHSRange.unsignedMulMayOverflow(RHSRange));
}
OverflowResult
llvm::computeOverflowForSignedMul(const Value *LHS, const Value *RHS,
const DataLayout &DL, AssumptionCache *AC,
const Instruction *CxtI,
const DominatorTree *DT, bool UseInstrInfo) {
// Multiplying n * m significant bits yields a result of n + m significant
// bits. If the total number of significant bits does not exceed the
// result bit width (minus 1), there is no overflow.
// This means if we have enough leading sign bits in the operands
// we can guarantee that the result does not overflow.
// Ref: "Hacker's Delight" by Henry Warren
unsigned BitWidth = LHS->getType()->getScalarSizeInBits();
// Note that underestimating the number of sign bits gives a more
// conservative answer.
unsigned SignBits = ComputeNumSignBits(LHS, DL, 0, AC, CxtI, DT) +
ComputeNumSignBits(RHS, DL, 0, AC, CxtI, DT);
// First handle the easy case: if we have enough sign bits there's
// definitely no overflow.
if (SignBits > BitWidth + 1)
return OverflowResult::NeverOverflows;
// There are two ambiguous cases where there can be no overflow:
// SignBits == BitWidth + 1 and
// SignBits == BitWidth
// The second case is difficult to check, therefore we only handle the
// first case.
if (SignBits == BitWidth + 1) {
// It overflows only when both arguments are negative and the true
// product is exactly the minimum negative number.
// E.g. mul i16 with 17 sign bits: 0xff00 * 0xff80 = 0x8000
// For simplicity we just check if at least one side is not negative.
KnownBits LHSKnown = computeKnownBits(LHS, DL, /*Depth=*/0, AC, CxtI, DT,
nullptr, UseInstrInfo);
KnownBits RHSKnown = computeKnownBits(RHS, DL, /*Depth=*/0, AC, CxtI, DT,
nullptr, UseInstrInfo);
if (LHSKnown.isNonNegative() || RHSKnown.isNonNegative())
return OverflowResult::NeverOverflows;
}
return OverflowResult::MayOverflow;
}
OverflowResult llvm::computeOverflowForUnsignedAdd(
const Value *LHS, const Value *RHS, const DataLayout &DL,
AssumptionCache *AC, const Instruction *CxtI, const DominatorTree *DT,
bool UseInstrInfo) {
ConstantRange LHSRange = computeConstantRangeIncludingKnownBits(
LHS, /*ForSigned=*/false, DL, /*Depth=*/0, AC, CxtI, DT,
nullptr, UseInstrInfo);
ConstantRange RHSRange = computeConstantRangeIncludingKnownBits(
RHS, /*ForSigned=*/false, DL, /*Depth=*/0, AC, CxtI, DT,
nullptr, UseInstrInfo);
return mapOverflowResult(LHSRange.unsignedAddMayOverflow(RHSRange));
}
static OverflowResult computeOverflowForSignedAdd(const Value *LHS,
const Value *RHS,
const AddOperator *Add,
const DataLayout &DL,
AssumptionCache *AC,
const Instruction *CxtI,
const DominatorTree *DT) {
if (Add && Add->hasNoSignedWrap()) {
return OverflowResult::NeverOverflows;
}
// If LHS and RHS each have at least two sign bits, the addition will look
// like
//
// XX..... +
// YY.....
//
// If the carry into the most significant position is 0, X and Y can't both
// be 1 and therefore the carry out of the addition is also 0.
//
// If the carry into the most significant position is 1, X and Y can't both
// be 0 and therefore the carry out of the addition is also 1.
//
// Since the carry into the most significant position is always equal to
// the carry out of the addition, there is no signed overflow.
if (ComputeNumSignBits(LHS, DL, 0, AC, CxtI, DT) > 1 &&
ComputeNumSignBits(RHS, DL, 0, AC, CxtI, DT) > 1)
return OverflowResult::NeverOverflows;
ConstantRange LHSRange = computeConstantRangeIncludingKnownBits(
LHS, /*ForSigned=*/true, DL, /*Depth=*/0, AC, CxtI, DT);
ConstantRange RHSRange = computeConstantRangeIncludingKnownBits(
RHS, /*ForSigned=*/true, DL, /*Depth=*/0, AC, CxtI, DT);
OverflowResult OR =
mapOverflowResult(LHSRange.signedAddMayOverflow(RHSRange));
if (OR != OverflowResult::MayOverflow)
return OR;
// The remaining code needs Add to be available. Early returns if not so.
if (!Add)
return OverflowResult::MayOverflow;
// If the sign of Add is the same as at least one of the operands, this add
// CANNOT overflow. If this can be determined from the known bits of the
// operands the above signedAddMayOverflow() check will have already done so.
// The only other way to improve on the known bits is from an assumption, so
// call computeKnownBitsFromAssume() directly.
bool LHSOrRHSKnownNonNegative =
(LHSRange.isAllNonNegative() || RHSRange.isAllNonNegative());
bool LHSOrRHSKnownNegative =
(LHSRange.isAllNegative() || RHSRange.isAllNegative());
if (LHSOrRHSKnownNonNegative || LHSOrRHSKnownNegative) {
KnownBits AddKnown(LHSRange.getBitWidth());
computeKnownBitsFromAssume(
Add, AddKnown, /*Depth=*/0, Query(DL, AC, CxtI, DT, true));
if ((AddKnown.isNonNegative() && LHSOrRHSKnownNonNegative) ||
(AddKnown.isNegative() && LHSOrRHSKnownNegative))
return OverflowResult::NeverOverflows;
}
return OverflowResult::MayOverflow;
}
OverflowResult llvm::computeOverflowForUnsignedSub(const Value *LHS,
const Value *RHS,
const DataLayout &DL,
AssumptionCache *AC,
const Instruction *CxtI,
const DominatorTree *DT) {
// Checking for conditions implied by dominating conditions may be expensive.
// Limit it to usub_with_overflow calls for now.
if (match(CxtI,
m_Intrinsic<Intrinsic::usub_with_overflow>(m_Value(), m_Value())))
if (auto C =
isImpliedByDomCondition(CmpInst::ICMP_UGE, LHS, RHS, CxtI, DL)) {
if (*C)
return OverflowResult::NeverOverflows;
return OverflowResult::AlwaysOverflowsLow;
}
ConstantRange LHSRange = computeConstantRangeIncludingKnownBits(
LHS, /*ForSigned=*/false, DL, /*Depth=*/0, AC, CxtI, DT);
ConstantRange RHSRange = computeConstantRangeIncludingKnownBits(
RHS, /*ForSigned=*/false, DL, /*Depth=*/0, AC, CxtI, DT);
return mapOverflowResult(LHSRange.unsignedSubMayOverflow(RHSRange));
}
OverflowResult llvm::computeOverflowForSignedSub(const Value *LHS,
const Value *RHS,
const DataLayout &DL,
AssumptionCache *AC,
const Instruction *CxtI,
const DominatorTree *DT) {
// If LHS and RHS each have at least two sign bits, the subtraction
// cannot overflow.
if (ComputeNumSignBits(LHS, DL, 0, AC, CxtI, DT) > 1 &&
ComputeNumSignBits(RHS, DL, 0, AC, CxtI, DT) > 1)
return OverflowResult::NeverOverflows;
ConstantRange LHSRange = computeConstantRangeIncludingKnownBits(
LHS, /*ForSigned=*/true, DL, /*Depth=*/0, AC, CxtI, DT);
ConstantRange RHSRange = computeConstantRangeIncludingKnownBits(
RHS, /*ForSigned=*/true, DL, /*Depth=*/0, AC, CxtI, DT);
return mapOverflowResult(LHSRange.signedSubMayOverflow(RHSRange));
}
bool llvm::isOverflowIntrinsicNoWrap(const WithOverflowInst *WO,
const DominatorTree &DT) {
SmallVector<const BranchInst *, 2> GuardingBranches;
SmallVector<const ExtractValueInst *, 2> Results;
for (const User *U : WO->users()) {
if (const auto *EVI = dyn_cast<ExtractValueInst>(U)) {
assert(EVI->getNumIndices() == 1 && "Obvious from CI's type");
if (EVI->getIndices()[0] == 0)
Results.push_back(EVI);
else {
assert(EVI->getIndices()[0] == 1 && "Obvious from CI's type");
for (const auto *U : EVI->users())
if (const auto *B = dyn_cast<BranchInst>(U)) {
assert(B->isConditional() && "How else is it using an i1?");
GuardingBranches.push_back(B);
}
}
} else {
// We are using the aggregate directly in a way we don't want to analyze
// here (storing it to a global, say).
return false;
}
}
auto AllUsesGuardedByBranch = [&](const BranchInst *BI) {
BasicBlockEdge NoWrapEdge(BI->getParent(), BI->getSuccessor(1));
if (!NoWrapEdge.isSingleEdge())
return false;
// Check if all users of the add are provably no-wrap.
for (const auto *Result : Results) {
// If the extractvalue itself is not executed on overflow, the we don't
// need to check each use separately, since domination is transitive.
if (DT.dominates(NoWrapEdge, Result->getParent()))
continue;
for (auto &RU : Result->uses())
if (!DT.dominates(NoWrapEdge, RU))
return false;
}
return true;
};
return llvm::any_of(GuardingBranches, AllUsesGuardedByBranch);
}
static bool canCreateUndefOrPoison(const Operator *Op, bool PoisonOnly) {
// See whether I has flags that may create poison
if (const auto *OvOp = dyn_cast<OverflowingBinaryOperator>(Op)) {
if (OvOp->hasNoSignedWrap() || OvOp->hasNoUnsignedWrap())
return true;
}
if (const auto *ExactOp = dyn_cast<PossiblyExactOperator>(Op))
if (ExactOp->isExact())
return true;
if (const auto *FP = dyn_cast<FPMathOperator>(Op)) {
auto FMF = FP->getFastMathFlags();
if (FMF.noNaNs() || FMF.noInfs())
return true;
}
unsigned Opcode = Op->getOpcode();
// Check whether opcode is a poison/undef-generating operation
switch (Opcode) {
case Instruction::Shl:
case Instruction::AShr:
case Instruction::LShr: {
// Shifts return poison if shiftwidth is larger than the bitwidth.
if (auto *C = dyn_cast<Constant>(Op->getOperand(1))) {
SmallVector<Constant *, 4> ShiftAmounts;
if (auto *FVTy = dyn_cast<FixedVectorType>(C->getType())) {
unsigned NumElts = FVTy->getNumElements();
for (unsigned i = 0; i < NumElts; ++i)
ShiftAmounts.push_back(C->getAggregateElement(i));
} else if (isa<ScalableVectorType>(C->getType()))
return true; // Can't tell, just return true to be safe
else
ShiftAmounts.push_back(C);
bool Safe = llvm::all_of(ShiftAmounts, [](Constant *C) {
auto *CI = dyn_cast_or_null<ConstantInt>(C);
return CI && CI->getValue().ult(C->getType()->getIntegerBitWidth());
});
return !Safe;
}
return true;
}
case Instruction::FPToSI:
case Instruction::FPToUI:
// fptosi/ui yields poison if the resulting value does not fit in the
// destination type.
return true;
case Instruction::Call:
if (auto *II = dyn_cast<IntrinsicInst>(Op)) {
switch (II->getIntrinsicID()) {
// TODO: Add more intrinsics.
case Intrinsic::ctpop:
return false;
}
}
LLVM_FALLTHROUGH;
case Instruction::CallBr:
case Instruction::Invoke: {
const auto *CB = cast<CallBase>(Op);
return !CB->hasRetAttr(Attribute::NoUndef);
}
case Instruction::InsertElement:
case Instruction::ExtractElement: {
// If index exceeds the length of the vector, it returns poison
auto *VTy = cast<VectorType>(Op->getOperand(0)->getType());
unsigned IdxOp = Op->getOpcode() == Instruction::InsertElement ? 2 : 1;
auto *Idx = dyn_cast<ConstantInt>(Op->getOperand(IdxOp));
if (!Idx || Idx->getValue().uge(VTy->getElementCount().getKnownMinValue()))
return true;
return false;
}
case Instruction::ShuffleVector: {
// shufflevector may return undef.
if (PoisonOnly)
return false;
ArrayRef<int> Mask = isa<ConstantExpr>(Op)
? cast<ConstantExpr>(Op)->getShuffleMask()
: cast<ShuffleVectorInst>(Op)->getShuffleMask();
return is_contained(Mask, UndefMaskElem);
}
case Instruction::FNeg:
case Instruction::PHI:
case Instruction::Select:
case Instruction::URem:
case Instruction::SRem:
case Instruction::ExtractValue:
case Instruction::InsertValue:
case Instruction::Freeze:
case Instruction::ICmp:
case Instruction::FCmp:
return false;
case Instruction::GetElementPtr: {
const auto *GEP = cast<GEPOperator>(Op);
return GEP->isInBounds();
}
default: {
const auto *CE = dyn_cast<ConstantExpr>(Op);
if (isa<CastInst>(Op) || (CE && CE->isCast()))
return false;
else if (Instruction::isBinaryOp(Opcode))
return false;
// Be conservative and return true.
return true;
}
}
}
bool llvm::canCreateUndefOrPoison(const Operator *Op) {
return ::canCreateUndefOrPoison(Op, /*PoisonOnly=*/false);
}
bool llvm::canCreatePoison(const Operator *Op) {
return ::canCreateUndefOrPoison(Op, /*PoisonOnly=*/true);
}
static bool directlyImpliesPoison(const Value *ValAssumedPoison,
const Value *V, unsigned Depth) {
if (ValAssumedPoison == V)
return true;
const unsigned MaxDepth = 2;
if (Depth >= MaxDepth)
return false;
if (const auto *I = dyn_cast<Instruction>(V)) {
if (propagatesPoison(cast<Operator>(I)))
return any_of(I->operands(), [=](const Value *Op) {
return directlyImpliesPoison(ValAssumedPoison, Op, Depth + 1);
});
// 'select ValAssumedPoison, _, _' is poison.
if (const auto *SI = dyn_cast<SelectInst>(I))
return directlyImpliesPoison(ValAssumedPoison, SI->getCondition(),
Depth + 1);
// V = extractvalue V0, idx
// V2 = extractvalue V0, idx2
// V0's elements are all poison or not. (e.g., add_with_overflow)
const WithOverflowInst *II;
if (match(I, m_ExtractValue(m_WithOverflowInst(II))) &&
match(ValAssumedPoison, m_ExtractValue(m_Specific(II))))
return true;
}
return false;
}
static bool impliesPoison(const Value *ValAssumedPoison, const Value *V,
unsigned Depth) {
if (isGuaranteedNotToBeUndefOrPoison(ValAssumedPoison))
return true;
if (directlyImpliesPoison(ValAssumedPoison, V, /* Depth */ 0))
return true;
const unsigned MaxDepth = 2;
if (Depth >= MaxDepth)
return false;
const auto *I = dyn_cast<Instruction>(ValAssumedPoison);
if (I && !canCreatePoison(cast<Operator>(I))) {
return all_of(I->operands(), [=](const Value *Op) {
return impliesPoison(Op, V, Depth + 1);
});
}
return false;
}
bool llvm::impliesPoison(const Value *ValAssumedPoison, const Value *V) {
return ::impliesPoison(ValAssumedPoison, V, /* Depth */ 0);
}
static bool programUndefinedIfUndefOrPoison(const Value *V,
bool PoisonOnly);
static bool isGuaranteedNotToBeUndefOrPoison(const Value *V,
AssumptionCache *AC,
const Instruction *CtxI,
const DominatorTree *DT,
unsigned Depth, bool PoisonOnly) {
if (Depth >= MaxAnalysisRecursionDepth)
return false;
if (isa<MetadataAsValue>(V))
return false;
if (const auto *A = dyn_cast<Argument>(V)) {
if (A->hasAttribute(Attribute::NoUndef))
return true;
}
if (auto *C = dyn_cast<Constant>(V)) {
if (isa<UndefValue>(C))
return PoisonOnly && !isa<PoisonValue>(C);
if (isa<ConstantInt>(C) || isa<GlobalVariable>(C) || isa<ConstantFP>(V) ||
isa<ConstantPointerNull>(C) || isa<Function>(C))
return true;
if (C->getType()->isVectorTy() && !isa<ConstantExpr>(C))
return (PoisonOnly ? !C->containsPoisonElement()
: !C->containsUndefOrPoisonElement()) &&
!C->containsConstantExpression();
}
// Strip cast operations from a pointer value.
// Note that stripPointerCastsSameRepresentation can strip off getelementptr
// inbounds with zero offset. To guarantee that the result isn't poison, the
// stripped pointer is checked as it has to be pointing into an allocated
// object or be null `null` to ensure `inbounds` getelement pointers with a
// zero offset could not produce poison.
// It can strip off addrspacecast that do not change bit representation as
// well. We believe that such addrspacecast is equivalent to no-op.
auto *StrippedV = V->stripPointerCastsSameRepresentation();
if (isa<AllocaInst>(StrippedV) || isa<GlobalVariable>(StrippedV) ||
isa<Function>(StrippedV) || isa<ConstantPointerNull>(StrippedV))
return true;
auto OpCheck = [&](const Value *V) {
return isGuaranteedNotToBeUndefOrPoison(V, AC, CtxI, DT, Depth + 1,
PoisonOnly);
};
if (auto *Opr = dyn_cast<Operator>(V)) {
// If the value is a freeze instruction, then it can never
// be undef or poison.
if (isa<FreezeInst>(V))
return true;
if (const auto *CB = dyn_cast<CallBase>(V)) {
if (CB->hasRetAttr(Attribute::NoUndef))
return true;
}
if (const auto *PN = dyn_cast<PHINode>(V)) {
unsigned Num = PN->getNumIncomingValues();
bool IsWellDefined = true;
for (unsigned i = 0; i < Num; ++i) {
auto *TI = PN->getIncomingBlock(i)->getTerminator();
if (!isGuaranteedNotToBeUndefOrPoison(PN->getIncomingValue(i), AC, TI,
DT, Depth + 1, PoisonOnly)) {
IsWellDefined = false;
break;
}
}
if (IsWellDefined)
return true;
} else if (!canCreateUndefOrPoison(Opr) && all_of(Opr->operands(), OpCheck))
return true;
}
if (auto *I = dyn_cast<LoadInst>(V))
if (I->getMetadata(LLVMContext::MD_noundef))
return true;
if (programUndefinedIfUndefOrPoison(V, PoisonOnly))
return true;
// CxtI may be null or a cloned instruction.
if (!CtxI || !CtxI->getParent() || !DT)
return false;
auto *DNode = DT->getNode(CtxI->getParent());
if (!DNode)
// Unreachable block
return false;
// If V is used as a branch condition before reaching CtxI, V cannot be
// undef or poison.
// br V, BB1, BB2
// BB1:
// CtxI ; V cannot be undef or poison here
auto *Dominator = DNode->getIDom();
while (Dominator) {
auto *TI = Dominator->getBlock()->getTerminator();
Value *Cond = nullptr;
if (auto BI = dyn_cast<BranchInst>(TI)) {
if (BI->isConditional())
Cond = BI->getCondition();
} else if (auto SI = dyn_cast<SwitchInst>(TI)) {
Cond = SI->getCondition();
}
if (Cond) {
if (Cond == V)
return true;
else if (PoisonOnly && isa<Operator>(Cond)) {
// For poison, we can analyze further
auto *Opr = cast<Operator>(Cond);
if (propagatesPoison(Opr) && is_contained(Opr->operand_values(), V))
return true;
}
}
Dominator = Dominator->getIDom();
}
SmallVector<Attribute::AttrKind, 2> AttrKinds{Attribute::NoUndef};
if (getKnowledgeValidInContext(V, AttrKinds, CtxI, DT, AC))
return true;
return false;
}
bool llvm::isGuaranteedNotToBeUndefOrPoison(const Value *V, AssumptionCache *AC,
const Instruction *CtxI,
const DominatorTree *DT,
unsigned Depth) {
return ::isGuaranteedNotToBeUndefOrPoison(V, AC, CtxI, DT, Depth, false);
}
bool llvm::isGuaranteedNotToBePoison(const Value *V, AssumptionCache *AC,
const Instruction *CtxI,
const DominatorTree *DT, unsigned Depth) {
return ::isGuaranteedNotToBeUndefOrPoison(V, AC, CtxI, DT, Depth, true);
}
OverflowResult llvm::computeOverflowForSignedAdd(const AddOperator *Add,
const DataLayout &DL,
AssumptionCache *AC,
const Instruction *CxtI,
const DominatorTree *DT) {
return ::computeOverflowForSignedAdd(Add->getOperand(0), Add->getOperand(1),
Add, DL, AC, CxtI, DT);
}
OverflowResult llvm::computeOverflowForSignedAdd(const Value *LHS,
const Value *RHS,
const DataLayout &DL,
AssumptionCache *AC,
const Instruction *CxtI,
const DominatorTree *DT) {
return ::computeOverflowForSignedAdd(LHS, RHS, nullptr, DL, AC, CxtI, DT);
}
bool llvm::isGuaranteedToTransferExecutionToSuccessor(const Instruction *I) {
// Note: An atomic operation isn't guaranteed to return in a reasonable amount
// of time because it's possible for another thread to interfere with it for an
// arbitrary length of time, but programs aren't allowed to rely on that.
// If there is no successor, then execution can't transfer to it.
if (isa<ReturnInst>(I))
return false;
if (isa<UnreachableInst>(I))
return false;
// An instruction that returns without throwing must transfer control flow
// to a successor.
return !I->mayThrow() && I->willReturn();
}
bool llvm::isGuaranteedToTransferExecutionToSuccessor(const BasicBlock *BB) {
// TODO: This is slightly conservative for invoke instruction since exiting
// via an exception *is* normal control for them.
for (const Instruction &I : *BB)
if (!isGuaranteedToTransferExecutionToSuccessor(&I))
return false;
return true;
}
bool llvm::isGuaranteedToExecuteForEveryIteration(const Instruction *I,
const Loop *L) {
// The loop header is guaranteed to be executed for every iteration.
//
// FIXME: Relax this constraint to cover all basic blocks that are
// guaranteed to be executed at every iteration.
if (I->getParent() != L->getHeader()) return false;
for (const Instruction &LI : *L->getHeader()) {
if (&LI == I) return true;
if (!isGuaranteedToTransferExecutionToSuccessor(&LI)) return false;
}
llvm_unreachable("Instruction not contained in its own parent basic block.");
}
bool llvm::propagatesPoison(const Operator *I) {
switch (I->getOpcode()) {
case Instruction::Freeze:
case Instruction::Select:
case Instruction::PHI:
case Instruction::Call:
case Instruction::Invoke:
return false;
case Instruction::ICmp:
case Instruction::FCmp:
case Instruction::GetElementPtr:
return true;
default:
if (isa<BinaryOperator>(I) || isa<UnaryOperator>(I) || isa<CastInst>(I))
return true;
// Be conservative and return false.
return false;
}
}
void llvm::getGuaranteedWellDefinedOps(
const Instruction *I, SmallPtrSetImpl<const Value *> &Operands) {
switch (I->getOpcode()) {
case Instruction::Store:
Operands.insert(cast<StoreInst>(I)->getPointerOperand());
break;
case Instruction::Load:
Operands.insert(cast<LoadInst>(I)->getPointerOperand());
break;
// Since dereferenceable attribute imply noundef, atomic operations
// also implicitly have noundef pointers too
case Instruction::AtomicCmpXchg:
Operands.insert(cast<AtomicCmpXchgInst>(I)->getPointerOperand());
break;
case Instruction::AtomicRMW:
Operands.insert(cast<AtomicRMWInst>(I)->getPointerOperand());
break;
case Instruction::Call:
case Instruction::Invoke: {
const CallBase *CB = cast<CallBase>(I);
if (CB->isIndirectCall())
Operands.insert(CB->getCalledOperand());
for (unsigned i = 0; i < CB->arg_size(); ++i) {
if (CB->paramHasAttr(i, Attribute::NoUndef) ||
CB->paramHasAttr(i, Attribute::Dereferenceable))
Operands.insert(CB->getArgOperand(i));
}
break;
}
default:
break;
}
}
void llvm::getGuaranteedNonPoisonOps(const Instruction *I,
SmallPtrSetImpl<const Value *> &Operands) {
getGuaranteedWellDefinedOps(I, Operands);
switch (I->getOpcode()) {
// Divisors of these operations are allowed to be partially undef.
case Instruction::UDiv:
case Instruction::SDiv:
case Instruction::URem:
case Instruction::SRem:
Operands.insert(I->getOperand(1));
break;
default:
break;
}
}
bool llvm::mustTriggerUB(const Instruction *I,
const SmallSet<const Value *, 16>& KnownPoison) {
SmallPtrSet<const Value *, 4> NonPoisonOps;
getGuaranteedNonPoisonOps(I, NonPoisonOps);
for (const auto *V : NonPoisonOps)
if (KnownPoison.count(V))
return true;
return false;
}
static bool programUndefinedIfUndefOrPoison(const Value *V,
bool PoisonOnly) {
// We currently only look for uses of values within the same basic
// block, as that makes it easier to guarantee that the uses will be
// executed given that Inst is executed.
//
// FIXME: Expand this to consider uses beyond the same basic block. To do
// this, look out for the distinction between post-dominance and strong
// post-dominance.
const BasicBlock *BB = nullptr;
BasicBlock::const_iterator Begin;
if (const auto *Inst = dyn_cast<Instruction>(V)) {
BB = Inst->getParent();
Begin = Inst->getIterator();
Begin++;
} else if (const auto *Arg = dyn_cast<Argument>(V)) {
BB = &Arg->getParent()->getEntryBlock();
Begin = BB->begin();
} else {
return false;
}
BasicBlock::const_iterator End = BB->end();
if (!PoisonOnly) {
// Since undef does not propagate eagerly, be conservative & just check
// whether a value is directly passed to an instruction that must take
// well-defined operands.
for (auto &I : make_range(Begin, End)) {
SmallPtrSet<const Value *, 4> WellDefinedOps;
getGuaranteedWellDefinedOps(&I, WellDefinedOps);
for (auto *Op : WellDefinedOps) {
if (Op == V)
return true;
}
if (!isGuaranteedToTransferExecutionToSuccessor(&I))
break;
}
return false;
}
// Set of instructions that we have proved will yield poison if Inst
// does.
SmallSet<const Value *, 16> YieldsPoison;
SmallSet<const BasicBlock *, 4> Visited;
YieldsPoison.insert(V);
auto Propagate = [&](const User *User) {
if (propagatesPoison(cast<Operator>(User)))
YieldsPoison.insert(User);
};
for_each(V->users(), Propagate);
Visited.insert(BB);
unsigned Iter = 0;
while (Iter++ < MaxAnalysisRecursionDepth) {
for (auto &I : make_range(Begin, End)) {
if (mustTriggerUB(&I, YieldsPoison))
return true;
if (!isGuaranteedToTransferExecutionToSuccessor(&I))
return false;
// Mark poison that propagates from I through uses of I.
if (YieldsPoison.count(&I))
for_each(I.users(), Propagate);
}
if (auto *NextBB = BB->getSingleSuccessor()) {
if (Visited.insert(NextBB).second) {
BB = NextBB;
Begin = BB->getFirstNonPHI()->getIterator();
End = BB->end();
continue;
}
}
break;
}
return false;
}
bool llvm::programUndefinedIfUndefOrPoison(const Instruction *Inst) {
return ::programUndefinedIfUndefOrPoison(Inst, false);
}
bool llvm::programUndefinedIfPoison(const Instruction *Inst) {
return ::programUndefinedIfUndefOrPoison(Inst, true);
}
static bool isKnownNonNaN(const Value *V, FastMathFlags FMF) {
if (FMF.noNaNs())
return true;
if (auto *C = dyn_cast<ConstantFP>(V))
return !C->isNaN();
if (auto *C = dyn_cast<ConstantDataVector>(V)) {
if (!C->getElementType()->isFloatingPointTy())
return false;
for (unsigned I = 0, E = C->getNumElements(); I < E; ++I) {
if (C->getElementAsAPFloat(I).isNaN())
return false;
}
return true;
}
if (isa<ConstantAggregateZero>(V))
return true;
return false;
}
static bool isKnownNonZero(const Value *V) {
if (auto *C = dyn_cast<ConstantFP>(V))
return !C->isZero();
if (auto *C = dyn_cast<ConstantDataVector>(V)) {
if (!C->getElementType()->isFloatingPointTy())
return false;
for (unsigned I = 0, E = C->getNumElements(); I < E; ++I) {
if (C->getElementAsAPFloat(I).isZero())
return false;
}
return true;
}
return false;
}
/// Match clamp pattern for float types without care about NaNs or signed zeros.
/// Given non-min/max outer cmp/select from the clamp pattern this
/// function recognizes if it can be substitued by a "canonical" min/max
/// pattern.
static SelectPatternResult matchFastFloatClamp(CmpInst::Predicate Pred,
Value *CmpLHS, Value *CmpRHS,
Value *TrueVal, Value *FalseVal,
Value *&LHS, Value *&RHS) {
// Try to match
// X < C1 ? C1 : Min(X, C2) --> Max(C1, Min(X, C2))
// X > C1 ? C1 : Max(X, C2) --> Min(C1, Max(X, C2))
// and return description of the outer Max/Min.
// First, check if select has inverse order:
if (CmpRHS == FalseVal) {
std::swap(TrueVal, FalseVal);
Pred = CmpInst::getInversePredicate(Pred);
}
// Assume success now. If there's no match, callers should not use these anyway.
LHS = TrueVal;
RHS = FalseVal;
const APFloat *FC1;
if (CmpRHS != TrueVal || !match(CmpRHS, m_APFloat(FC1)) || !FC1->isFinite())
return {SPF_UNKNOWN, SPNB_NA, false};
const APFloat *FC2;
switch (Pred) {
case CmpInst::FCMP_OLT:
case CmpInst::FCMP_OLE:
case CmpInst::FCMP_ULT:
case CmpInst::FCMP_ULE:
if (match(FalseVal,
m_CombineOr(m_OrdFMin(m_Specific(CmpLHS), m_APFloat(FC2)),
m_UnordFMin(m_Specific(CmpLHS), m_APFloat(FC2)))) &&
*FC1 < *FC2)
return {SPF_FMAXNUM, SPNB_RETURNS_ANY, false};
break;
case CmpInst::FCMP_OGT:
case CmpInst::FCMP_OGE:
case CmpInst::FCMP_UGT:
case CmpInst::FCMP_UGE:
if (match(FalseVal,
m_CombineOr(m_OrdFMax(m_Specific(CmpLHS), m_APFloat(FC2)),
m_UnordFMax(m_Specific(CmpLHS), m_APFloat(FC2)))) &&
*FC1 > *FC2)
return {SPF_FMINNUM, SPNB_RETURNS_ANY, false};
break;
default:
break;
}
return {SPF_UNKNOWN, SPNB_NA, false};
}
/// Recognize variations of:
/// CLAMP(v,l,h) ==> ((v) < (l) ? (l) : ((v) > (h) ? (h) : (v)))
static SelectPatternResult matchClamp(CmpInst::Predicate Pred,
Value *CmpLHS, Value *CmpRHS,
Value *TrueVal, Value *FalseVal) {
// Swap the select operands and predicate to match the patterns below.
if (CmpRHS != TrueVal) {
Pred = ICmpInst::getSwappedPredicate(Pred);
std::swap(TrueVal, FalseVal);
}
const APInt *C1;
if (CmpRHS == TrueVal && match(CmpRHS, m_APInt(C1))) {
const APInt *C2;
// (X <s C1) ? C1 : SMIN(X, C2) ==> SMAX(SMIN(X, C2), C1)
if (match(FalseVal, m_SMin(m_Specific(CmpLHS), m_APInt(C2))) &&
C1->slt(*C2) && Pred == CmpInst::ICMP_SLT)
return {SPF_SMAX, SPNB_NA, false};
// (X >s C1) ? C1 : SMAX(X, C2) ==> SMIN(SMAX(X, C2), C1)
if (match(FalseVal, m_SMax(m_Specific(CmpLHS), m_APInt(C2))) &&
C1->sgt(*C2) && Pred == CmpInst::ICMP_SGT)
return {SPF_SMIN, SPNB_NA, false};
// (X <u C1) ? C1 : UMIN(X, C2) ==> UMAX(UMIN(X, C2), C1)
if (match(FalseVal, m_UMin(m_Specific(CmpLHS), m_APInt(C2))) &&
C1->ult(*C2) && Pred == CmpInst::ICMP_ULT)
return {SPF_UMAX, SPNB_NA, false};
// (X >u C1) ? C1 : UMAX(X, C2) ==> UMIN(UMAX(X, C2), C1)
if (match(FalseVal, m_UMax(m_Specific(CmpLHS), m_APInt(C2))) &&
C1->ugt(*C2) && Pred == CmpInst::ICMP_UGT)
return {SPF_UMIN, SPNB_NA, false};
}
return {SPF_UNKNOWN, SPNB_NA, false};
}
/// Recognize variations of:
/// a < c ? min(a,b) : min(b,c) ==> min(min(a,b),min(b,c))
static SelectPatternResult matchMinMaxOfMinMax(CmpInst::Predicate Pred,
Value *CmpLHS, Value *CmpRHS,
Value *TVal, Value *FVal,
unsigned Depth) {
// TODO: Allow FP min/max with nnan/nsz.
assert(CmpInst::isIntPredicate(Pred) && "Expected integer comparison");
Value *A = nullptr, *B = nullptr;
SelectPatternResult L = matchSelectPattern(TVal, A, B, nullptr, Depth + 1);
if (!SelectPatternResult::isMinOrMax(L.Flavor))
return {SPF_UNKNOWN, SPNB_NA, false};
Value *C = nullptr, *D = nullptr;
SelectPatternResult R = matchSelectPattern(FVal, C, D, nullptr, Depth + 1);
if (L.Flavor != R.Flavor)
return {SPF_UNKNOWN, SPNB_NA, false};
// We have something like: x Pred y ? min(a, b) : min(c, d).
// Try to match the compare to the min/max operations of the select operands.
// First, make sure we have the right compare predicate.
switch (L.Flavor) {
case SPF_SMIN:
if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE) {
Pred = ICmpInst::getSwappedPredicate(Pred);
std::swap(CmpLHS, CmpRHS);
}
if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE)
break;
return {SPF_UNKNOWN, SPNB_NA, false};
case SPF_SMAX:
if (Pred == ICmpInst::ICMP_SLT || Pred == ICmpInst::ICMP_SLE) {
Pred = ICmpInst::getSwappedPredicate(Pred);
std::swap(CmpLHS, CmpRHS);
}
if (Pred == ICmpInst::ICMP_SGT || Pred == ICmpInst::ICMP_SGE)
break;
return {SPF_UNKNOWN, SPNB_NA, false};
case SPF_UMIN:
if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE) {
Pred = ICmpInst::getSwappedPredicate(Pred);
std::swap(CmpLHS, CmpRHS);
}
if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE)
break;
return {SPF_UNKNOWN, SPNB_NA, false};
case SPF_UMAX:
if (Pred == ICmpInst::ICMP_ULT || Pred == ICmpInst::ICMP_ULE) {
Pred = ICmpInst::getSwappedPredicate(Pred);
std::swap(CmpLHS, CmpRHS);
}
if (Pred == ICmpInst::ICMP_UGT || Pred == ICmpInst::ICMP_UGE)
break;
return {SPF_UNKNOWN, SPNB_NA, false};
default:
return {SPF_UNKNOWN, SPNB_NA, false};
}
// If there is a common operand in the already matched min/max and the other
// min/max operands match the compare operands (either directly or inverted),
// then this is min/max of the same flavor.
// a pred c ? m(a, b) : m(c, b) --> m(m(a, b), m(c, b))
// ~c pred ~a ? m(a, b) : m(c, b) --> m(m(a, b), m(c, b))
if (D == B) {
if ((CmpLHS == A && CmpRHS == C) || (match(C, m_Not(m_Specific(CmpLHS))) &&
match(A, m_Not(m_Specific(CmpRHS)))))
return {L.Flavor, SPNB_NA, false};
}
// a pred d ? m(a, b) : m(b, d) --> m(m(a, b), m(b, d))
// ~d pred ~a ? m(a, b) : m(b, d) --> m(m(a, b), m(b, d))
if (C == B) {
if ((CmpLHS == A && CmpRHS == D) || (match(D, m_Not(m_Specific(CmpLHS))) &&
match(A, m_Not(m_Specific(CmpRHS)))))
return {L.Flavor, SPNB_NA, false};
}
// b pred c ? m(a, b) : m(c, a) --> m(m(a, b), m(c, a))
// ~c pred ~b ? m(a, b) : m(c, a) --> m(m(a, b), m(c, a))
if (D == A) {
if ((CmpLHS == B && CmpRHS == C) || (match(C, m_Not(m_Specific(CmpLHS))) &&
match(B, m_Not(m_Specific(CmpRHS)))))
return {L.Flavor, SPNB_NA, false};
}
// b pred d ? m(a, b) : m(a, d) --> m(m(a, b), m(a, d))
// ~d pred ~b ? m(a, b) : m(a, d) --> m(m(a, b), m(a, d))
if (C == A) {
if ((CmpLHS == B && CmpRHS == D) || (match(D, m_Not(m_Specific(CmpLHS))) &&
match(B, m_Not(m_Specific(CmpRHS)))))
return {L.Flavor, SPNB_NA, false};
}
return {SPF_UNKNOWN, SPNB_NA, false};
}
/// If the input value is the result of a 'not' op, constant integer, or vector
/// splat of a constant integer, return the bitwise-not source value.
/// TODO: This could be extended to handle non-splat vector integer constants.
static Value *getNotValue(Value *V) {
Value *NotV;
if (match(V, m_Not(m_Value(NotV))))
return NotV;
const APInt *C;
if (match(V, m_APInt(C)))
return ConstantInt::get(V->getType(), ~(*C));
return nullptr;
}
/// Match non-obvious integer minimum and maximum sequences.
static SelectPatternResult matchMinMax(CmpInst::Predicate Pred,
Value *CmpLHS, Value *CmpRHS,
Value *TrueVal, Value *FalseVal,
Value *&LHS, Value *&RHS,
unsigned Depth) {
// Assume success. If there's no match, callers should not use these anyway.
LHS = TrueVal;
RHS = FalseVal;
SelectPatternResult SPR = matchClamp(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal);
if (SPR.Flavor != SelectPatternFlavor::SPF_UNKNOWN)
return SPR;
SPR = matchMinMaxOfMinMax(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal, Depth);
if (SPR.Flavor != SelectPatternFlavor::SPF_UNKNOWN)
return SPR;
// Look through 'not' ops to find disguised min/max.
// (X > Y) ? ~X : ~Y ==> (~X < ~Y) ? ~X : ~Y ==> MIN(~X, ~Y)
// (X < Y) ? ~X : ~Y ==> (~X > ~Y) ? ~X : ~Y ==> MAX(~X, ~Y)
if (CmpLHS == getNotValue(TrueVal) && CmpRHS == getNotValue(FalseVal)) {
switch (Pred) {
case CmpInst::ICMP_SGT: return {SPF_SMIN, SPNB_NA, false};
case CmpInst::ICMP_SLT: return {SPF_SMAX, SPNB_NA, false};
case CmpInst::ICMP_UGT: return {SPF_UMIN, SPNB_NA, false};
case CmpInst::ICMP_ULT: return {SPF_UMAX, SPNB_NA, false};
default: break;
}
}
// (X > Y) ? ~Y : ~X ==> (~X < ~Y) ? ~Y : ~X ==> MAX(~Y, ~X)
// (X < Y) ? ~Y : ~X ==> (~X > ~Y) ? ~Y : ~X ==> MIN(~Y, ~X)
if (CmpLHS == getNotValue(FalseVal) && CmpRHS == getNotValue(TrueVal)) {
switch (Pred) {
case CmpInst::ICMP_SGT: return {SPF_SMAX, SPNB_NA, false};
case CmpInst::ICMP_SLT: return {SPF_SMIN, SPNB_NA, false};
case CmpInst::ICMP_UGT: return {SPF_UMAX, SPNB_NA, false};
case CmpInst::ICMP_ULT: return {SPF_UMIN, SPNB_NA, false};
default: break;
}
}
if (Pred != CmpInst::ICMP_SGT && Pred != CmpInst::ICMP_SLT)
return {SPF_UNKNOWN, SPNB_NA, false};
// Z = X -nsw Y
// (X >s Y) ? 0 : Z ==> (Z >s 0) ? 0 : Z ==> SMIN(Z, 0)
// (X <s Y) ? 0 : Z ==> (Z <s 0) ? 0 : Z ==> SMAX(Z, 0)
if (match(TrueVal, m_Zero()) &&
match(FalseVal, m_NSWSub(m_Specific(CmpLHS), m_Specific(CmpRHS))))
return {Pred == CmpInst::ICMP_SGT ? SPF_SMIN : SPF_SMAX, SPNB_NA, false};
// Z = X -nsw Y
// (X >s Y) ? Z : 0 ==> (Z >s 0) ? Z : 0 ==> SMAX(Z, 0)
// (X <s Y) ? Z : 0 ==> (Z <s 0) ? Z : 0 ==> SMIN(Z, 0)
if (match(FalseVal, m_Zero()) &&
match(TrueVal, m_NSWSub(m_Specific(CmpLHS), m_Specific(CmpRHS))))
return {Pred == CmpInst::ICMP_SGT ? SPF_SMAX : SPF_SMIN, SPNB_NA, false};
const APInt *C1;
if (!match(CmpRHS, m_APInt(C1)))
return {SPF_UNKNOWN, SPNB_NA, false};
// An unsigned min/max can be written with a signed compare.
const APInt *C2;
if ((CmpLHS == TrueVal && match(FalseVal, m_APInt(C2))) ||
(CmpLHS == FalseVal && match(TrueVal, m_APInt(C2)))) {
// Is the sign bit set?
// (X <s 0) ? X : MAXVAL ==> (X >u MAXVAL) ? X : MAXVAL ==> UMAX
// (X <s 0) ? MAXVAL : X ==> (X >u MAXVAL) ? MAXVAL : X ==> UMIN
if (Pred == CmpInst::ICMP_SLT && C1->isNullValue() &&
C2->isMaxSignedValue())
return {CmpLHS == TrueVal ? SPF_UMAX : SPF_UMIN, SPNB_NA, false};
// Is the sign bit clear?
// (X >s -1) ? MINVAL : X ==> (X <u MINVAL) ? MINVAL : X ==> UMAX
// (X >s -1) ? X : MINVAL ==> (X <u MINVAL) ? X : MINVAL ==> UMIN
if (Pred == CmpInst::ICMP_SGT && C1->isAllOnesValue() &&
C2->isMinSignedValue())
return {CmpLHS == FalseVal ? SPF_UMAX : SPF_UMIN, SPNB_NA, false};
}
return {SPF_UNKNOWN, SPNB_NA, false};
}
bool llvm::isKnownNegation(const Value *X, const Value *Y, bool NeedNSW) {
assert(X && Y && "Invalid operand");
// X = sub (0, Y) || X = sub nsw (0, Y)
if ((!NeedNSW && match(X, m_Sub(m_ZeroInt(), m_Specific(Y)))) ||
(NeedNSW && match(X, m_NSWSub(m_ZeroInt(), m_Specific(Y)))))
return true;
// Y = sub (0, X) || Y = sub nsw (0, X)
if ((!NeedNSW && match(Y, m_Sub(m_ZeroInt(), m_Specific(X)))) ||
(NeedNSW && match(Y, m_NSWSub(m_ZeroInt(), m_Specific(X)))))
return true;
// X = sub (A, B), Y = sub (B, A) || X = sub nsw (A, B), Y = sub nsw (B, A)
Value *A, *B;
return (!NeedNSW && (match(X, m_Sub(m_Value(A), m_Value(B))) &&
match(Y, m_Sub(m_Specific(B), m_Specific(A))))) ||
(NeedNSW && (match(X, m_NSWSub(m_Value(A), m_Value(B))) &&
match(Y, m_NSWSub(m_Specific(B), m_Specific(A)))));
}
static SelectPatternResult matchSelectPattern(CmpInst::Predicate Pred,
FastMathFlags FMF,
Value *CmpLHS, Value *CmpRHS,
Value *TrueVal, Value *FalseVal,
Value *&LHS, Value *&RHS,
unsigned Depth) {
if (CmpInst::isFPPredicate(Pred)) {
// IEEE-754 ignores the sign of 0.0 in comparisons. So if the select has one
// 0.0 operand, set the compare's 0.0 operands to that same value for the
// purpose of identifying min/max. Disregard vector constants with undefined
// elements because those can not be back-propagated for analysis.
Value *OutputZeroVal = nullptr;
if (match(TrueVal, m_AnyZeroFP()) && !match(FalseVal, m_AnyZeroFP()) &&
!cast<Constant>(TrueVal)->containsUndefOrPoisonElement())
OutputZeroVal = TrueVal;
else if (match(FalseVal, m_AnyZeroFP()) && !match(TrueVal, m_AnyZeroFP()) &&
!cast<Constant>(FalseVal)->containsUndefOrPoisonElement())
OutputZeroVal = FalseVal;
if (OutputZeroVal) {
if (match(CmpLHS, m_AnyZeroFP()))
CmpLHS = OutputZeroVal;
if (match(CmpRHS, m_AnyZeroFP()))
CmpRHS = OutputZeroVal;
}
}
LHS = CmpLHS;
RHS = CmpRHS;
// Signed zero may return inconsistent results between implementations.
// (0.0 <= -0.0) ? 0.0 : -0.0 // Returns 0.0
// minNum(0.0, -0.0) // May return -0.0 or 0.0 (IEEE 754-2008 5.3.1)
// Therefore, we behave conservatively and only proceed if at least one of the
// operands is known to not be zero or if we don't care about signed zero.
switch (Pred) {
default: break;
// FIXME: Include OGT/OLT/UGT/ULT.
case CmpInst::FCMP_OGE: case CmpInst::FCMP_OLE:
case CmpInst::FCMP_UGE: case CmpInst::FCMP_ULE:
if (!FMF.noSignedZeros() && !isKnownNonZero(CmpLHS) &&
!isKnownNonZero(CmpRHS))
return {SPF_UNKNOWN, SPNB_NA, false};
}
SelectPatternNaNBehavior NaNBehavior = SPNB_NA;
bool Ordered = false;
// When given one NaN and one non-NaN input:
// - maxnum/minnum (C99 fmaxf()/fminf()) return the non-NaN input.
// - A simple C99 (a < b ? a : b) construction will return 'b' (as the
// ordered comparison fails), which could be NaN or non-NaN.
// so here we discover exactly what NaN behavior is required/accepted.
if (CmpInst::isFPPredicate(Pred)) {
bool LHSSafe = isKnownNonNaN(CmpLHS, FMF);
bool RHSSafe = isKnownNonNaN(CmpRHS, FMF);
if (LHSSafe && RHSSafe) {
// Both operands are known non-NaN.
NaNBehavior = SPNB_RETURNS_ANY;
} else if (CmpInst::isOrdered(Pred)) {
// An ordered comparison will return false when given a NaN, so it
// returns the RHS.
Ordered = true;
if (LHSSafe)
// LHS is non-NaN, so if RHS is NaN then NaN will be returned.
NaNBehavior = SPNB_RETURNS_NAN;
else if (RHSSafe)
NaNBehavior = SPNB_RETURNS_OTHER;
else
// Completely unsafe.
return {SPF_UNKNOWN, SPNB_NA, false};
} else {
Ordered = false;
// An unordered comparison will return true when given a NaN, so it
// returns the LHS.
if (LHSSafe)
// LHS is non-NaN, so if RHS is NaN then non-NaN will be returned.
NaNBehavior = SPNB_RETURNS_OTHER;
else if (RHSSafe)
NaNBehavior = SPNB_RETURNS_NAN;
else
// Completely unsafe.
return {SPF_UNKNOWN, SPNB_NA, false};
}
}
if (TrueVal == CmpRHS && FalseVal == CmpLHS) {
std::swap(CmpLHS, CmpRHS);
Pred = CmpInst::getSwappedPredicate(Pred);
if (NaNBehavior == SPNB_RETURNS_NAN)
NaNBehavior = SPNB_RETURNS_OTHER;
else if (NaNBehavior == SPNB_RETURNS_OTHER)
NaNBehavior = SPNB_RETURNS_NAN;
Ordered = !Ordered;
}
// ([if]cmp X, Y) ? X : Y
if (TrueVal == CmpLHS && FalseVal == CmpRHS) {
switch (Pred) {
default: return {SPF_UNKNOWN, SPNB_NA, false}; // Equality.
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_UGE: return {SPF_UMAX, SPNB_NA, false};
case ICmpInst::ICMP_SGT:
case ICmpInst::ICMP_SGE: return {SPF_SMAX, SPNB_NA, false};
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_ULE: return {SPF_UMIN, SPNB_NA, false};
case ICmpInst::ICMP_SLT:
case ICmpInst::ICMP_SLE: return {SPF_SMIN, SPNB_NA, false};
case FCmpInst::FCMP_UGT:
case FCmpInst::FCMP_UGE:
case FCmpInst::FCMP_OGT:
case FCmpInst::FCMP_OGE: return {SPF_FMAXNUM, NaNBehavior, Ordered};
case FCmpInst::FCMP_ULT:
case FCmpInst::FCMP_ULE:
case FCmpInst::FCMP_OLT:
case FCmpInst::FCMP_OLE: return {SPF_FMINNUM, NaNBehavior, Ordered};
}
}
if (isKnownNegation(TrueVal, FalseVal)) {
// Sign-extending LHS does not change its sign, so TrueVal/FalseVal can
// match against either LHS or sext(LHS).
auto MaybeSExtCmpLHS =
m_CombineOr(m_Specific(CmpLHS), m_SExt(m_Specific(CmpLHS)));
auto ZeroOrAllOnes = m_CombineOr(m_ZeroInt(), m_AllOnes());
auto ZeroOrOne = m_CombineOr(m_ZeroInt(), m_One());
if (match(TrueVal, MaybeSExtCmpLHS)) {
// Set the return values. If the compare uses the negated value (-X >s 0),
// swap the return values because the negated value is always 'RHS'.
LHS = TrueVal;
RHS = FalseVal;
if (match(CmpLHS, m_Neg(m_Specific(FalseVal))))
std::swap(LHS, RHS);
// (X >s 0) ? X : -X or (X >s -1) ? X : -X --> ABS(X)
// (-X >s 0) ? -X : X or (-X >s -1) ? -X : X --> ABS(X)
if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, ZeroOrAllOnes))
return {SPF_ABS, SPNB_NA, false};
// (X >=s 0) ? X : -X or (X >=s 1) ? X : -X --> ABS(X)
if (Pred == ICmpInst::ICMP_SGE && match(CmpRHS, ZeroOrOne))
return {SPF_ABS, SPNB_NA, false};
// (X <s 0) ? X : -X or (X <s 1) ? X : -X --> NABS(X)
// (-X <s 0) ? -X : X or (-X <s 1) ? -X : X --> NABS(X)
if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, ZeroOrOne))
return {SPF_NABS, SPNB_NA, false};
}
else if (match(FalseVal, MaybeSExtCmpLHS)) {
// Set the return values. If the compare uses the negated value (-X >s 0),
// swap the return values because the negated value is always 'RHS'.
LHS = FalseVal;
RHS = TrueVal;
if (match(CmpLHS, m_Neg(m_Specific(TrueVal))))
std::swap(LHS, RHS);
// (X >s 0) ? -X : X or (X >s -1) ? -X : X --> NABS(X)
// (-X >s 0) ? X : -X or (-X >s -1) ? X : -X --> NABS(X)
if (Pred == ICmpInst::ICMP_SGT && match(CmpRHS, ZeroOrAllOnes))
return {SPF_NABS, SPNB_NA, false};
// (X <s 0) ? -X : X or (X <s 1) ? -X : X --> ABS(X)
// (-X <s 0) ? X : -X or (-X <s 1) ? X : -X --> ABS(X)
if (Pred == ICmpInst::ICMP_SLT && match(CmpRHS, ZeroOrOne))
return {SPF_ABS, SPNB_NA, false};
}
}
if (CmpInst::isIntPredicate(Pred))
return matchMinMax(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal, LHS, RHS, Depth);
// According to (IEEE 754-2008 5.3.1), minNum(0.0, -0.0) and similar
// may return either -0.0 or 0.0, so fcmp/select pair has stricter
// semantics than minNum. Be conservative in such case.
if (NaNBehavior != SPNB_RETURNS_ANY ||
(!FMF.noSignedZeros() && !isKnownNonZero(CmpLHS) &&
!isKnownNonZero(CmpRHS)))
return {SPF_UNKNOWN, SPNB_NA, false};
return matchFastFloatClamp(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal, LHS, RHS);
}
/// Helps to match a select pattern in case of a type mismatch.
///
/// The function processes the case when type of true and false values of a
/// select instruction differs from type of the cmp instruction operands because
/// of a cast instruction. The function checks if it is legal to move the cast
/// operation after "select". If yes, it returns the new second value of
/// "select" (with the assumption that cast is moved):
/// 1. As operand of cast instruction when both values of "select" are same cast
/// instructions.
/// 2. As restored constant (by applying reverse cast operation) when the first
/// value of the "select" is a cast operation and the second value is a
/// constant.
/// NOTE: We return only the new second value because the first value could be
/// accessed as operand of cast instruction.
static Value *lookThroughCast(CmpInst *CmpI, Value *V1, Value *V2,
Instruction::CastOps *CastOp) {
auto *Cast1 = dyn_cast<CastInst>(V1);
if (!Cast1)
return nullptr;
*CastOp = Cast1->getOpcode();
Type *SrcTy = Cast1->getSrcTy();
if (auto *Cast2 = dyn_cast<CastInst>(V2)) {
// If V1 and V2 are both the same cast from the same type, look through V1.
if (*CastOp == Cast2->getOpcode() && SrcTy == Cast2->getSrcTy())
return Cast2->getOperand(0);
return nullptr;
}
auto *C = dyn_cast<Constant>(V2);
if (!C)
return nullptr;
Constant *CastedTo = nullptr;
switch (*CastOp) {
case Instruction::ZExt:
if (CmpI->isUnsigned())
CastedTo = ConstantExpr::getTrunc(C, SrcTy);
break;
case Instruction::SExt:
if (CmpI->isSigned())
CastedTo = ConstantExpr::getTrunc(C, SrcTy, true);
break;
case Instruction::Trunc:
Constant *CmpConst;
if (match(CmpI->getOperand(1), m_Constant(CmpConst)) &&
CmpConst->getType() == SrcTy) {
// Here we have the following case:
//
// %cond = cmp iN %x, CmpConst
// %tr = trunc iN %x to iK
// %narrowsel = select i1 %cond, iK %t, iK C
//
// We can always move trunc after select operation:
//
// %cond = cmp iN %x, CmpConst
// %widesel = select i1 %cond, iN %x, iN CmpConst
// %tr = trunc iN %widesel to iK
//
// Note that C could be extended in any way because we don't care about
// upper bits after truncation. It can't be abs pattern, because it would
// look like:
//
// select i1 %cond, x, -x.
//
// So only min/max pattern could be matched. Such match requires widened C
// == CmpConst. That is why set widened C = CmpConst, condition trunc
// CmpConst == C is checked below.
CastedTo = CmpConst;
} else {
CastedTo = ConstantExpr::getIntegerCast(C, SrcTy, CmpI->isSigned());
}
break;
case Instruction::FPTrunc:
CastedTo = ConstantExpr::getFPExtend(C, SrcTy, true);
break;
case Instruction::FPExt:
CastedTo = ConstantExpr::getFPTrunc(C, SrcTy, true);
break;
case Instruction::FPToUI:
CastedTo = ConstantExpr::getUIToFP(C, SrcTy, true);
break;
case Instruction::FPToSI:
CastedTo = ConstantExpr::getSIToFP(C, SrcTy, true);
break;
case Instruction::UIToFP:
CastedTo = ConstantExpr::getFPToUI(C, SrcTy, true);
break;
case Instruction::SIToFP:
CastedTo = ConstantExpr::getFPToSI(C, SrcTy, true);
break;
default:
break;
}
if (!CastedTo)
return nullptr;
// Make sure the cast doesn't lose any information.
Constant *CastedBack =
ConstantExpr::getCast(*CastOp, CastedTo, C->getType(), true);
if (CastedBack != C)
return nullptr;
return CastedTo;
}
SelectPatternResult llvm::matchSelectPattern(Value *V, Value *&LHS, Value *&RHS,
Instruction::CastOps *CastOp,
unsigned Depth) {
if (Depth >= MaxAnalysisRecursionDepth)
return {SPF_UNKNOWN, SPNB_NA, false};
SelectInst *SI = dyn_cast<SelectInst>(V);
if (!SI) return {SPF_UNKNOWN, SPNB_NA, false};
CmpInst *CmpI = dyn_cast<CmpInst>(SI->getCondition());
if (!CmpI) return {SPF_UNKNOWN, SPNB_NA, false};
Value *TrueVal = SI->getTrueValue();
Value *FalseVal = SI->getFalseValue();
return llvm::matchDecomposedSelectPattern(CmpI, TrueVal, FalseVal, LHS, RHS,
CastOp, Depth);
}
SelectPatternResult llvm::matchDecomposedSelectPattern(
CmpInst *CmpI, Value *TrueVal, Value *FalseVal, Value *&LHS, Value *&RHS,
Instruction::CastOps *CastOp, unsigned Depth) {
CmpInst::Predicate Pred = CmpI->getPredicate();
Value *CmpLHS = CmpI->getOperand(0);
Value *CmpRHS = CmpI->getOperand(1);
FastMathFlags FMF;
if (isa<FPMathOperator>(CmpI))
FMF = CmpI->getFastMathFlags();
// Bail out early.
if (CmpI->isEquality())
return {SPF_UNKNOWN, SPNB_NA, false};
// Deal with type mismatches.
if (CastOp && CmpLHS->getType() != TrueVal->getType()) {
if (Value *C = lookThroughCast(CmpI, TrueVal, FalseVal, CastOp)) {
// If this is a potential fmin/fmax with a cast to integer, then ignore
// -0.0 because there is no corresponding integer value.
if (*CastOp == Instruction::FPToSI || *CastOp == Instruction::FPToUI)
FMF.setNoSignedZeros();
return ::matchSelectPattern(Pred, FMF, CmpLHS, CmpRHS,
cast<CastInst>(TrueVal)->getOperand(0), C,
LHS, RHS, Depth);
}
if (Value *C = lookThroughCast(CmpI, FalseVal, TrueVal, CastOp)) {
// If this is a potential fmin/fmax with a cast to integer, then ignore
// -0.0 because there is no corresponding integer value.
if (*CastOp == Instruction::FPToSI || *CastOp == Instruction::FPToUI)
FMF.setNoSignedZeros();
return ::matchSelectPattern(Pred, FMF, CmpLHS, CmpRHS,
C, cast<CastInst>(FalseVal)->getOperand(0),
LHS, RHS, Depth);
}
}
return ::matchSelectPattern(Pred, FMF, CmpLHS, CmpRHS, TrueVal, FalseVal,
LHS, RHS, Depth);
}
CmpInst::Predicate llvm::getMinMaxPred(SelectPatternFlavor SPF, bool Ordered) {
if (SPF == SPF_SMIN) return ICmpInst::ICMP_SLT;
if (SPF == SPF_UMIN) return ICmpInst::ICMP_ULT;
if (SPF == SPF_SMAX) return ICmpInst::ICMP_SGT;
if (SPF == SPF_UMAX) return ICmpInst::ICMP_UGT;
if (SPF == SPF_FMINNUM)
return Ordered ? FCmpInst::FCMP_OLT : FCmpInst::FCMP_ULT;
if (SPF == SPF_FMAXNUM)
return Ordered ? FCmpInst::FCMP_OGT : FCmpInst::FCMP_UGT;
llvm_unreachable("unhandled!");
}
SelectPatternFlavor llvm::getInverseMinMaxFlavor(SelectPatternFlavor SPF) {
if (SPF == SPF_SMIN) return SPF_SMAX;
if (SPF == SPF_UMIN) return SPF_UMAX;
if (SPF == SPF_SMAX) return SPF_SMIN;
if (SPF == SPF_UMAX) return SPF_UMIN;
llvm_unreachable("unhandled!");
}
Intrinsic::ID llvm::getInverseMinMaxIntrinsic(Intrinsic::ID MinMaxID) {
switch (MinMaxID) {
case Intrinsic::smax: return Intrinsic::smin;
case Intrinsic::smin: return Intrinsic::smax;
case Intrinsic::umax: return Intrinsic::umin;
case Intrinsic::umin: return Intrinsic::umax;
default: llvm_unreachable("Unexpected intrinsic");
}
}
CmpInst::Predicate llvm::getInverseMinMaxPred(SelectPatternFlavor SPF) {
return getMinMaxPred(getInverseMinMaxFlavor(SPF));
}
std::pair<Intrinsic::ID, bool>
llvm::canConvertToMinOrMaxIntrinsic(ArrayRef<Value *> VL) {
// Check if VL contains select instructions that can be folded into a min/max
// vector intrinsic and return the intrinsic if it is possible.
// TODO: Support floating point min/max.
bool AllCmpSingleUse = true;
SelectPatternResult SelectPattern;
SelectPattern.Flavor = SPF_UNKNOWN;
if (all_of(VL, [&SelectPattern, &AllCmpSingleUse](Value *I) {
Value *LHS, *RHS;
auto CurrentPattern = matchSelectPattern(I, LHS, RHS);
if (!SelectPatternResult::isMinOrMax(CurrentPattern.Flavor) ||
CurrentPattern.Flavor == SPF_FMINNUM ||
CurrentPattern.Flavor == SPF_FMAXNUM ||
!I->getType()->isIntOrIntVectorTy())
return false;
if (SelectPattern.Flavor != SPF_UNKNOWN &&
SelectPattern.Flavor != CurrentPattern.Flavor)
return false;
SelectPattern = CurrentPattern;
AllCmpSingleUse &=
match(I, m_Select(m_OneUse(m_Value()), m_Value(), m_Value()));
return true;
})) {
switch (SelectPattern.Flavor) {
case SPF_SMIN:
return {Intrinsic::smin, AllCmpSingleUse};
case SPF_UMIN:
return {Intrinsic::umin, AllCmpSingleUse};
case SPF_SMAX:
return {Intrinsic::smax, AllCmpSingleUse};
case SPF_UMAX:
return {Intrinsic::umax, AllCmpSingleUse};
default:
llvm_unreachable("unexpected select pattern flavor");
}
}
return {Intrinsic::not_intrinsic, false};
}
bool llvm::matchSimpleRecurrence(const PHINode *P, BinaryOperator *&BO,
Value *&Start, Value *&Step) {
// Handle the case of a simple two-predecessor recurrence PHI.
// There's a lot more that could theoretically be done here, but
// this is sufficient to catch some interesting cases.
if (P->getNumIncomingValues() != 2)
return false;
for (unsigned i = 0; i != 2; ++i) {
Value *L = P->getIncomingValue(i);
Value *R = P->getIncomingValue(!i);
Operator *LU = dyn_cast<Operator>(L);
if (!LU)
continue;
unsigned Opcode = LU->getOpcode();
switch (Opcode) {
default:
continue;
// TODO: Expand list -- xor, div, gep, uaddo, etc..
case Instruction::LShr:
case Instruction::AShr:
case Instruction::Shl:
case Instruction::Add:
case Instruction::Sub:
case Instruction::And:
case Instruction::Or:
case Instruction::Mul: {
Value *LL = LU->getOperand(0);
Value *LR = LU->getOperand(1);
// Find a recurrence.
if (LL == P)
L = LR;
else if (LR == P)
L = LL;
else
continue; // Check for recurrence with L and R flipped.
break; // Match!
}
};
// We have matched a recurrence of the form:
// %iv = [R, %entry], [%iv.next, %backedge]
// %iv.next = binop %iv, L
// OR
// %iv = [R, %entry], [%iv.next, %backedge]
// %iv.next = binop L, %iv
BO = cast<BinaryOperator>(LU);
Start = R;
Step = L;
return true;
}
return false;
}
bool llvm::matchSimpleRecurrence(const BinaryOperator *I, PHINode *&P,
Value *&Start, Value *&Step) {
BinaryOperator *BO = nullptr;
P = dyn_cast<PHINode>(I->getOperand(0));
if (!P)
P = dyn_cast<PHINode>(I->getOperand(1));
return P && matchSimpleRecurrence(P, BO, Start, Step) && BO == I;
}
/// Return true if "icmp Pred LHS RHS" is always true.
static bool isTruePredicate(CmpInst::Predicate Pred, const Value *LHS,
const Value *RHS, const DataLayout &DL,
unsigned Depth) {
assert(!LHS->getType()->isVectorTy() && "TODO: extend to handle vectors!");
if (ICmpInst::isTrueWhenEqual(Pred) && LHS == RHS)
return true;
switch (Pred) {
default:
return false;
case CmpInst::ICMP_SLE: {
const APInt *C;
// LHS s<= LHS +_{nsw} C if C >= 0
if (match(RHS, m_NSWAdd(m_Specific(LHS), m_APInt(C))))
return !C->isNegative();
return false;
}
case CmpInst::ICMP_ULE: {
const APInt *C;
// LHS u<= LHS +_{nuw} C for any C
if (match(RHS, m_NUWAdd(m_Specific(LHS), m_APInt(C))))
return true;
// Match A to (X +_{nuw} CA) and B to (X +_{nuw} CB)
auto MatchNUWAddsToSameValue = [&](const Value *A, const Value *B,
const Value *&X,
const APInt *&CA, const APInt *&CB) {
if (match(A, m_NUWAdd(m_Value(X), m_APInt(CA))) &&
match(B, m_NUWAdd(m_Specific(X), m_APInt(CB))))
return true;
// If X & C == 0 then (X | C) == X +_{nuw} C
if (match(A, m_Or(m_Value(X), m_APInt(CA))) &&
match(B, m_Or(m_Specific(X), m_APInt(CB)))) {
KnownBits Known(CA->getBitWidth());
computeKnownBits(X, Known, DL, Depth + 1, /*AC*/ nullptr,
/*CxtI*/ nullptr, /*DT*/ nullptr);
if (CA->isSubsetOf(Known.Zero) && CB->isSubsetOf(Known.Zero))
return true;
}
return false;
};
const Value *X;
const APInt *CLHS, *CRHS;
if (MatchNUWAddsToSameValue(LHS, RHS, X, CLHS, CRHS))
return CLHS->ule(*CRHS);
return false;
}
}
}
/// Return true if "icmp Pred BLHS BRHS" is true whenever "icmp Pred
/// ALHS ARHS" is true. Otherwise, return None.
static Optional<bool>
isImpliedCondOperands(CmpInst::Predicate Pred, const Value *ALHS,
const Value *ARHS, const Value *BLHS, const Value *BRHS,
const DataLayout &DL, unsigned Depth) {
switch (Pred) {
default:
return None;
case CmpInst::ICMP_SLT:
case CmpInst::ICMP_SLE:
if (isTruePredicate(CmpInst::ICMP_SLE, BLHS, ALHS, DL, Depth) &&
isTruePredicate(CmpInst::ICMP_SLE, ARHS, BRHS, DL, Depth))
return true;
return None;
case CmpInst::ICMP_ULT:
case CmpInst::ICMP_ULE:
if (isTruePredicate(CmpInst::ICMP_ULE, BLHS, ALHS, DL, Depth) &&
isTruePredicate(CmpInst::ICMP_ULE, ARHS, BRHS, DL, Depth))
return true;
return None;
}
}
/// Return true if the operands of the two compares match. IsSwappedOps is true
/// when the operands match, but are swapped.
static bool isMatchingOps(const Value *ALHS, const Value *ARHS,
const Value *BLHS, const Value *BRHS,
bool &IsSwappedOps) {
bool IsMatchingOps = (ALHS == BLHS && ARHS == BRHS);
IsSwappedOps = (ALHS == BRHS && ARHS == BLHS);
return IsMatchingOps || IsSwappedOps;
}
/// Return true if "icmp1 APred X, Y" implies "icmp2 BPred X, Y" is true.
/// Return false if "icmp1 APred X, Y" implies "icmp2 BPred X, Y" is false.
/// Otherwise, return None if we can't infer anything.
static Optional<bool> isImpliedCondMatchingOperands(CmpInst::Predicate APred,
CmpInst::Predicate BPred,
bool AreSwappedOps) {
// Canonicalize the predicate as if the operands were not commuted.
if (AreSwappedOps)
BPred = ICmpInst::getSwappedPredicate(BPred);
if (CmpInst::isImpliedTrueByMatchingCmp(APred, BPred))
return true;
if (CmpInst::isImpliedFalseByMatchingCmp(APred, BPred))
return false;
return None;
}
/// Return true if "icmp APred X, C1" implies "icmp BPred X, C2" is true.
/// Return false if "icmp APred X, C1" implies "icmp BPred X, C2" is false.
/// Otherwise, return None if we can't infer anything.
static Optional<bool>
isImpliedCondMatchingImmOperands(CmpInst::Predicate APred,
const ConstantInt *C1,
CmpInst::Predicate BPred,
const ConstantInt *C2) {
ConstantRange DomCR =
ConstantRange::makeExactICmpRegion(APred, C1->getValue());
ConstantRange CR =
ConstantRange::makeAllowedICmpRegion(BPred, C2->getValue());
ConstantRange Intersection = DomCR.intersectWith(CR);
ConstantRange Difference = DomCR.difference(CR);
if (Intersection.isEmptySet())
return false;
if (Difference.isEmptySet())
return true;
return None;
}
/// Return true if LHS implies RHS is true. Return false if LHS implies RHS is
/// false. Otherwise, return None if we can't infer anything.
static Optional<bool> isImpliedCondICmps(const ICmpInst *LHS,
CmpInst::Predicate BPred,
const Value *BLHS, const Value *BRHS,
const DataLayout &DL, bool LHSIsTrue,
unsigned Depth) {
Value *ALHS = LHS->getOperand(0);
Value *ARHS = LHS->getOperand(1);
// The rest of the logic assumes the LHS condition is true. If that's not the
// case, invert the predicate to make it so.
CmpInst::Predicate APred =
LHSIsTrue ? LHS->getPredicate() : LHS->getInversePredicate();
// Can we infer anything when the two compares have matching operands?
bool AreSwappedOps;
if (isMatchingOps(ALHS, ARHS, BLHS, BRHS, AreSwappedOps)) {
if (Optional<bool> Implication = isImpliedCondMatchingOperands(
APred, BPred, AreSwappedOps))
return Implication;
// No amount of additional analysis will infer the second condition, so
// early exit.
return None;
}
// Can we infer anything when the LHS operands match and the RHS operands are
// constants (not necessarily matching)?
if (ALHS == BLHS && isa<ConstantInt>(ARHS) && isa<ConstantInt>(BRHS)) {
if (Optional<bool> Implication = isImpliedCondMatchingImmOperands(
APred, cast<ConstantInt>(ARHS), BPred, cast<ConstantInt>(BRHS)))
return Implication;
// No amount of additional analysis will infer the second condition, so
// early exit.
return None;
}
if (APred == BPred)
return isImpliedCondOperands(APred, ALHS, ARHS, BLHS, BRHS, DL, Depth);
return None;
}
/// Return true if LHS implies RHS is true. Return false if LHS implies RHS is
/// false. Otherwise, return None if we can't infer anything. We expect the
/// RHS to be an icmp and the LHS to be an 'and', 'or', or a 'select' instruction.
static Optional<bool>
isImpliedCondAndOr(const Instruction *LHS, CmpInst::Predicate RHSPred,
const Value *RHSOp0, const Value *RHSOp1,
const DataLayout &DL, bool LHSIsTrue, unsigned Depth) {
// The LHS must be an 'or', 'and', or a 'select' instruction.
assert((LHS->getOpcode() == Instruction::And ||
LHS->getOpcode() == Instruction::Or ||
LHS->getOpcode() == Instruction::Select) &&
"Expected LHS to be 'and', 'or', or 'select'.");
assert(Depth <= MaxAnalysisRecursionDepth && "Hit recursion limit");
// If the result of an 'or' is false, then we know both legs of the 'or' are
// false. Similarly, if the result of an 'and' is true, then we know both
// legs of the 'and' are true.
const Value *ALHS, *ARHS;
if ((!LHSIsTrue && match(LHS, m_LogicalOr(m_Value(ALHS), m_Value(ARHS)))) ||
(LHSIsTrue && match(LHS, m_LogicalAnd(m_Value(ALHS), m_Value(ARHS))))) {
// FIXME: Make this non-recursion.
if (Optional<bool> Implication = isImpliedCondition(
ALHS, RHSPred, RHSOp0, RHSOp1, DL, LHSIsTrue, Depth + 1))
return Implication;
if (Optional<bool> Implication = isImpliedCondition(
ARHS, RHSPred, RHSOp0, RHSOp1, DL, LHSIsTrue, Depth + 1))
return Implication;
return None;
}
return None;
}
Optional<bool>
llvm::isImpliedCondition(const Value *LHS, CmpInst::Predicate RHSPred,
const Value *RHSOp0, const Value *RHSOp1,
const DataLayout &DL, bool LHSIsTrue, unsigned Depth) {
// Bail out when we hit the limit.
if (Depth == MaxAnalysisRecursionDepth)
return None;
// A mismatch occurs when we compare a scalar cmp to a vector cmp, for
// example.
if (RHSOp0->getType()->isVectorTy() != LHS->getType()->isVectorTy())
return None;
Type *OpTy = LHS->getType();
assert(OpTy->isIntOrIntVectorTy(1) && "Expected integer type only!");
// FIXME: Extending the code below to handle vectors.
if (OpTy->isVectorTy())
return None;
assert(OpTy->isIntegerTy(1) && "implied by above");
// Both LHS and RHS are icmps.
const ICmpInst *LHSCmp = dyn_cast<ICmpInst>(LHS);
if (LHSCmp)
return isImpliedCondICmps(LHSCmp, RHSPred, RHSOp0, RHSOp1, DL, LHSIsTrue,
Depth);
/// The LHS should be an 'or', 'and', or a 'select' instruction. We expect
/// the RHS to be an icmp.
/// FIXME: Add support for and/or/select on the RHS.
if (const Instruction *LHSI = dyn_cast<Instruction>(LHS)) {
if ((LHSI->getOpcode() == Instruction::And ||
LHSI->getOpcode() == Instruction::Or ||
LHSI->getOpcode() == Instruction::Select))
return isImpliedCondAndOr(LHSI, RHSPred, RHSOp0, RHSOp1, DL, LHSIsTrue,
Depth);
}
return None;
}
Optional<bool> llvm::isImpliedCondition(const Value *LHS, const Value *RHS,
const DataLayout &DL, bool LHSIsTrue,
unsigned Depth) {
// LHS ==> RHS by definition
if (LHS == RHS)
return LHSIsTrue;
const ICmpInst *RHSCmp = dyn_cast<ICmpInst>(RHS);
if (RHSCmp)
return isImpliedCondition(LHS, RHSCmp->getPredicate(),
RHSCmp->getOperand(0), RHSCmp->getOperand(1), DL,
LHSIsTrue, Depth);
return None;
}
// Returns a pair (Condition, ConditionIsTrue), where Condition is a branch
// condition dominating ContextI or nullptr, if no condition is found.
static std::pair<Value *, bool>
getDomPredecessorCondition(const Instruction *ContextI) {
if (!ContextI || !ContextI->getParent())
return {nullptr, false};
// TODO: This is a poor/cheap way to determine dominance. Should we use a
// dominator tree (eg, from a SimplifyQuery) instead?
const BasicBlock *ContextBB = ContextI->getParent();
const BasicBlock *PredBB = ContextBB->getSinglePredecessor();
if (!PredBB)
return {nullptr, false};
// We need a conditional branch in the predecessor.
Value *PredCond;
BasicBlock *TrueBB, *FalseBB;
if (!match(PredBB->getTerminator(), m_Br(m_Value(PredCond), TrueBB, FalseBB)))
return {nullptr, false};
// The branch should get simplified. Don't bother simplifying this condition.
if (TrueBB == FalseBB)
return {nullptr, false};
assert((TrueBB == ContextBB || FalseBB == ContextBB) &&
"Predecessor block does not point to successor?");
// Is this condition implied by the predecessor condition?
return {PredCond, TrueBB == ContextBB};
}
Optional<bool> llvm::isImpliedByDomCondition(const Value *Cond,
const Instruction *ContextI,
const DataLayout &DL) {
assert(Cond->getType()->isIntOrIntVectorTy(1) && "Condition must be bool");
auto PredCond = getDomPredecessorCondition(ContextI);
if (PredCond.first)
return isImpliedCondition(PredCond.first, Cond, DL, PredCond.second);
return None;
}
Optional<bool> llvm::isImpliedByDomCondition(CmpInst::Predicate Pred,
const Value *LHS, const Value *RHS,
const Instruction *ContextI,
const DataLayout &DL) {
auto PredCond = getDomPredecessorCondition(ContextI);
if (PredCond.first)
return isImpliedCondition(PredCond.first, Pred, LHS, RHS, DL,
PredCond.second);
return None;
}
static void setLimitsForBinOp(const BinaryOperator &BO, APInt &Lower,
APInt &Upper, const InstrInfoQuery &IIQ) {
unsigned Width = Lower.getBitWidth();
const APInt *C;
switch (BO.getOpcode()) {
case Instruction::Add:
if (match(BO.getOperand(1), m_APInt(C)) && !C->isNullValue()) {
// FIXME: If we have both nuw and nsw, we should reduce the range further.
if (IIQ.hasNoUnsignedWrap(cast<OverflowingBinaryOperator>(&BO))) {
// 'add nuw x, C' produces [C, UINT_MAX].
Lower = *C;
} else if (IIQ.hasNoSignedWrap(cast<OverflowingBinaryOperator>(&BO))) {
if (C->isNegative()) {
// 'add nsw x, -C' produces [SINT_MIN, SINT_MAX - C].
Lower = APInt::getSignedMinValue(Width);
Upper = APInt::getSignedMaxValue(Width) + *C + 1;
} else {
// 'add nsw x, +C' produces [SINT_MIN + C, SINT_MAX].
Lower = APInt::getSignedMinValue(Width) + *C;
Upper = APInt::getSignedMaxValue(Width) + 1;
}
}
}
break;
case Instruction::And:
if (match(BO.getOperand(1), m_APInt(C)))
// 'and x, C' produces [0, C].
Upper = *C + 1;
break;
case Instruction::Or:
if (match(BO.getOperand(1), m_APInt(C)))
// 'or x, C' produces [C, UINT_MAX].
Lower = *C;
break;
case Instruction::AShr:
if (match(BO.getOperand(1), m_APInt(C)) && C->ult(Width)) {
// 'ashr x, C' produces [INT_MIN >> C, INT_MAX >> C].
Lower = APInt::getSignedMinValue(Width).ashr(*C);
Upper = APInt::getSignedMaxValue(Width).ashr(*C) + 1;
} else if (match(BO.getOperand(0), m_APInt(C))) {
unsigned ShiftAmount = Width - 1;
if (!C->isNullValue() && IIQ.isExact(&BO))
ShiftAmount = C->countTrailingZeros();
if (C->isNegative()) {
// 'ashr C, x' produces [C, C >> (Width-1)]
Lower = *C;
Upper = C->ashr(ShiftAmount) + 1;
} else {
// 'ashr C, x' produces [C >> (Width-1), C]
Lower = C->ashr(ShiftAmount);
Upper = *C + 1;
}
}
break;
case Instruction::LShr:
if (match(BO.getOperand(1), m_APInt(C)) && C->ult(Width)) {
// 'lshr x, C' produces [0, UINT_MAX >> C].
Upper = APInt::getAllOnesValue(Width).lshr(*C) + 1;
} else if (match(BO.getOperand(0), m_APInt(C))) {
// 'lshr C, x' produces [C >> (Width-1), C].
unsigned ShiftAmount = Width - 1;
if (!C->isNullValue() && IIQ.isExact(&BO))
ShiftAmount = C->countTrailingZeros();
Lower = C->lshr(ShiftAmount);
Upper = *C + 1;
}
break;
case Instruction::Shl:
if (match(BO.getOperand(0), m_APInt(C))) {
if (IIQ.hasNoUnsignedWrap(&BO)) {
// 'shl nuw C, x' produces [C, C << CLZ(C)]
Lower = *C;
Upper = Lower.shl(Lower.countLeadingZeros()) + 1;
} else if (BO.hasNoSignedWrap()) { // TODO: What if both nuw+nsw?
if (C->isNegative()) {
// 'shl nsw C, x' produces [C << CLO(C)-1, C]
unsigned ShiftAmount = C->countLeadingOnes() - 1;
Lower = C->shl(ShiftAmount);
Upper = *C + 1;
} else {
// 'shl nsw C, x' produces [C, C << CLZ(C)-1]
unsigned ShiftAmount = C->countLeadingZeros() - 1;
Lower = *C;
Upper = C->shl(ShiftAmount) + 1;
}
}
}
break;
case Instruction::SDiv:
if (match(BO.getOperand(1), m_APInt(C))) {
APInt IntMin = APInt::getSignedMinValue(Width);
APInt IntMax = APInt::getSignedMaxValue(Width);
if (C->isAllOnesValue()) {
// 'sdiv x, -1' produces [INT_MIN + 1, INT_MAX]
// where C != -1 and C != 0 and C != 1
Lower = IntMin + 1;
Upper = IntMax + 1;
} else if (C->countLeadingZeros() < Width - 1) {
// 'sdiv x, C' produces [INT_MIN / C, INT_MAX / C]
// where C != -1 and C != 0 and C != 1
Lower = IntMin.sdiv(*C);
Upper = IntMax.sdiv(*C);
if (Lower.sgt(Upper))
std::swap(Lower, Upper);
Upper = Upper + 1;
assert(Upper != Lower && "Upper part of range has wrapped!");
}
} else if (match(BO.getOperand(0), m_APInt(C))) {
if (C->isMinSignedValue()) {
// 'sdiv INT_MIN, x' produces [INT_MIN, INT_MIN / -2].
Lower = *C;
Upper = Lower.lshr(1) + 1;
} else {
// 'sdiv C, x' produces [-|C|, |C|].
Upper = C->abs() + 1;
Lower = (-Upper) + 1;
}
}
break;
case Instruction::UDiv:
if (match(BO.getOperand(1), m_APInt(C)) && !C->isNullValue()) {
// 'udiv x, C' produces [0, UINT_MAX / C].
Upper = APInt::getMaxValue(Width).udiv(*C) + 1;
} else if (match(BO.getOperand(0), m_APInt(C))) {
// 'udiv C, x' produces [0, C].
Upper = *C + 1;
}
break;
case Instruction::SRem:
if (match(BO.getOperand(1), m_APInt(C))) {
// 'srem x, C' produces (-|C|, |C|).
Upper = C->abs();
Lower = (-Upper) + 1;
}
break;
case Instruction::URem:
if (match(BO.getOperand(1), m_APInt(C)))
// 'urem x, C' produces [0, C).
Upper = *C;
break;
default:
break;
}
}
static void setLimitsForIntrinsic(const IntrinsicInst &II, APInt &Lower,
APInt &Upper) {
unsigned Width = Lower.getBitWidth();
const APInt *C;
switch (II.getIntrinsicID()) {
case Intrinsic::ctpop:
case Intrinsic::ctlz:
case Intrinsic::cttz:
// Maximum of set/clear bits is the bit width.
assert(Lower == 0 && "Expected lower bound to be zero");
Upper = Width + 1;
break;
case Intrinsic::uadd_sat:
// uadd.sat(x, C) produces [C, UINT_MAX].
if (match(II.getOperand(0), m_APInt(C)) ||
match(II.getOperand(1), m_APInt(C)))
Lower = *C;
break;
case Intrinsic::sadd_sat:
if (match(II.getOperand(0), m_APInt(C)) ||
match(II.getOperand(1), m_APInt(C))) {
if (C->isNegative()) {
// sadd.sat(x, -C) produces [SINT_MIN, SINT_MAX + (-C)].
Lower = APInt::getSignedMinValue(Width);
Upper = APInt::getSignedMaxValue(Width) + *C + 1;
} else {
// sadd.sat(x, +C) produces [SINT_MIN + C, SINT_MAX].
Lower = APInt::getSignedMinValue(Width) + *C;
Upper = APInt::getSignedMaxValue(Width) + 1;
}
}
break;
case Intrinsic::usub_sat:
// usub.sat(C, x) produces [0, C].
if (match(II.getOperand(0), m_APInt(C)))
Upper = *C + 1;
// usub.sat(x, C) produces [0, UINT_MAX - C].
else if (match(II.getOperand(1), m_APInt(C)))
Upper = APInt::getMaxValue(Width) - *C + 1;
break;
case Intrinsic::ssub_sat:
if (match(II.getOperand(0), m_APInt(C))) {
if (C->isNegative()) {
// ssub.sat(-C, x) produces [SINT_MIN, -SINT_MIN + (-C)].
Lower = APInt::getSignedMinValue(Width);
Upper = *C - APInt::getSignedMinValue(Width) + 1;
} else {
// ssub.sat(+C, x) produces [-SINT_MAX + C, SINT_MAX].
Lower = *C - APInt::getSignedMaxValue(Width);
Upper = APInt::getSignedMaxValue(Width) + 1;
}
} else if (match(II.getOperand(1), m_APInt(C))) {
if (C->isNegative()) {
// ssub.sat(x, -C) produces [SINT_MIN - (-C), SINT_MAX]:
Lower = APInt::getSignedMinValue(Width) - *C;
Upper = APInt::getSignedMaxValue(Width) + 1;
} else {
// ssub.sat(x, +C) produces [SINT_MIN, SINT_MAX - C].
Lower = APInt::getSignedMinValue(Width);
Upper = APInt::getSignedMaxValue(Width) - *C + 1;
}
}
break;
case Intrinsic::umin:
case Intrinsic::umax:
case Intrinsic::smin:
case Intrinsic::smax:
if (!match(II.getOperand(0), m_APInt(C)) &&
!match(II.getOperand(1), m_APInt(C)))
break;
switch (II.getIntrinsicID()) {
case Intrinsic::umin:
Upper = *C + 1;
break;
case Intrinsic::umax:
Lower = *C;
break;
case Intrinsic::smin:
Lower = APInt::getSignedMinValue(Width);
Upper = *C + 1;
break;
case Intrinsic::smax:
Lower = *C;
Upper = APInt::getSignedMaxValue(Width) + 1;
break;
default:
llvm_unreachable("Must be min/max intrinsic");
}
break;
case Intrinsic::abs:
// If abs of SIGNED_MIN is poison, then the result is [0..SIGNED_MAX],
// otherwise it is [0..SIGNED_MIN], as -SIGNED_MIN == SIGNED_MIN.
if (match(II.getOperand(1), m_One()))
Upper = APInt::getSignedMaxValue(Width) + 1;
else
Upper = APInt::getSignedMinValue(Width) + 1;
break;
default:
break;
}
}
static void setLimitsForSelectPattern(const SelectInst &SI, APInt &Lower,
APInt &Upper, const InstrInfoQuery &IIQ) {
const Value *LHS = nullptr, *RHS = nullptr;
SelectPatternResult R = matchSelectPattern(&SI, LHS, RHS);
if (R.Flavor == SPF_UNKNOWN)
return;
unsigned BitWidth = SI.getType()->getScalarSizeInBits();
if (R.Flavor == SelectPatternFlavor::SPF_ABS) {
// If the negation part of the abs (in RHS) has the NSW flag,
// then the result of abs(X) is [0..SIGNED_MAX],
// otherwise it is [0..SIGNED_MIN], as -SIGNED_MIN == SIGNED_MIN.
Lower = APInt::getNullValue(BitWidth);
if (match(RHS, m_Neg(m_Specific(LHS))) &&
IIQ.hasNoSignedWrap(cast<Instruction>(RHS)))
Upper = APInt::getSignedMaxValue(BitWidth) + 1;
else
Upper = APInt::getSignedMinValue(BitWidth) + 1;
return;
}
if (R.Flavor == SelectPatternFlavor::SPF_NABS) {
// The result of -abs(X) is <= 0.
Lower = APInt::getSignedMinValue(BitWidth);
Upper = APInt(BitWidth, 1);
return;
}
const APInt *C;
if (!match(LHS, m_APInt(C)) && !match(RHS, m_APInt(C)))
return;
switch (R.Flavor) {
case SPF_UMIN:
Upper = *C + 1;
break;
case SPF_UMAX:
Lower = *C;
break;
case SPF_SMIN:
Lower = APInt::getSignedMinValue(BitWidth);
Upper = *C + 1;
break;
case SPF_SMAX:
Lower = *C;
Upper = APInt::getSignedMaxValue(BitWidth) + 1;
break;
default:
break;
}
}
ConstantRange llvm::computeConstantRange(const Value *V, bool UseInstrInfo,
AssumptionCache *AC,
const Instruction *CtxI,
unsigned Depth) {
assert(V->getType()->isIntOrIntVectorTy() && "Expected integer instruction");
if (Depth == MaxAnalysisRecursionDepth)
return ConstantRange::getFull(V->getType()->getScalarSizeInBits());
const APInt *C;
if (match(V, m_APInt(C)))
return ConstantRange(*C);
InstrInfoQuery IIQ(UseInstrInfo);
unsigned BitWidth = V->getType()->getScalarSizeInBits();
APInt Lower = APInt(BitWidth, 0);
APInt Upper = APInt(BitWidth, 0);
if (auto *BO = dyn_cast<BinaryOperator>(V))
setLimitsForBinOp(*BO, Lower, Upper, IIQ);
else if (auto *II = dyn_cast<IntrinsicInst>(V))
setLimitsForIntrinsic(*II, Lower, Upper);
else if (auto *SI = dyn_cast<SelectInst>(V))
setLimitsForSelectPattern(*SI, Lower, Upper, IIQ);
ConstantRange CR = ConstantRange::getNonEmpty(Lower, Upper);
if (auto *I = dyn_cast<Instruction>(V))
if (auto *Range = IIQ.getMetadata(I, LLVMContext::MD_range))
CR = CR.intersectWith(getConstantRangeFromMetadata(*Range));
if (CtxI && AC) {
// Try to restrict the range based on information from assumptions.
for (auto &AssumeVH : AC->assumptionsFor(V)) {
if (!AssumeVH)
continue;
CallInst *I = cast<CallInst>(AssumeVH);
assert(I->getParent()->getParent() == CtxI->getParent()->getParent() &&
"Got assumption for the wrong function!");
assert(I->getCalledFunction()->getIntrinsicID() == Intrinsic::assume &&
"must be an assume intrinsic");
if (!isValidAssumeForContext(I, CtxI, nullptr))
continue;
Value *Arg = I->getArgOperand(0);
ICmpInst *Cmp = dyn_cast<ICmpInst>(Arg);
// Currently we just use information from comparisons.
if (!Cmp || Cmp->getOperand(0) != V)
continue;
ConstantRange RHS = computeConstantRange(Cmp->getOperand(1), UseInstrInfo,
AC, I, Depth + 1);
CR = CR.intersectWith(
ConstantRange::makeSatisfyingICmpRegion(Cmp->getPredicate(), RHS));
}
}
return CR;
}
static Optional<int64_t>
getOffsetFromIndex(const GEPOperator *GEP, unsigned Idx, const DataLayout &DL) {
// Skip over the first indices.
gep_type_iterator GTI = gep_type_begin(GEP);
for (unsigned i = 1; i != Idx; ++i, ++GTI)
/*skip along*/;
// Compute the offset implied by the rest of the indices.
int64_t Offset = 0;
for (unsigned i = Idx, e = GEP->getNumOperands(); i != e; ++i, ++GTI) {
ConstantInt *OpC = dyn_cast<ConstantInt>(GEP->getOperand(i));
if (!OpC)
return None;
if (OpC->isZero())
continue; // No offset.
// Handle struct indices, which add their field offset to the pointer.
if (StructType *STy = GTI.getStructTypeOrNull()) {
Offset += DL.getStructLayout(STy)->getElementOffset(OpC->getZExtValue());
continue;
}
// Otherwise, we have a sequential type like an array or fixed-length
// vector. Multiply the index by the ElementSize.
TypeSize Size = DL.getTypeAllocSize(GTI.getIndexedType());
if (Size.isScalable())
return None;
Offset += Size.getFixedSize() * OpC->getSExtValue();
}
return Offset;
}
Optional<int64_t> llvm::isPointerOffset(const Value *Ptr1, const Value *Ptr2,
const DataLayout &DL) {
Ptr1 = Ptr1->stripPointerCasts();
Ptr2 = Ptr2->stripPointerCasts();
// Handle the trivial case first.
if (Ptr1 == Ptr2) {
return 0;
}
const GEPOperator *GEP1 = dyn_cast<GEPOperator>(Ptr1);
const GEPOperator *GEP2 = dyn_cast<GEPOperator>(Ptr2);
// If one pointer is a GEP see if the GEP is a constant offset from the base,
// as in "P" and "gep P, 1".
// Also do this iteratively to handle the the following case:
// Ptr_t1 = GEP Ptr1, c1
// Ptr_t2 = GEP Ptr_t1, c2
// Ptr2 = GEP Ptr_t2, c3
// where we will return c1+c2+c3.
// TODO: Handle the case when both Ptr1 and Ptr2 are GEPs of some common base
// -- replace getOffsetFromBase with getOffsetAndBase, check that the bases
// are the same, and return the difference between offsets.
auto getOffsetFromBase = [&DL](const GEPOperator *GEP,
const Value *Ptr) -> Optional<int64_t> {
const GEPOperator *GEP_T = GEP;
int64_t OffsetVal = 0;
bool HasSameBase = false;
while (GEP_T) {
auto Offset = getOffsetFromIndex(GEP_T, 1, DL);
if (!Offset)
return None;
OffsetVal += *Offset;
auto Op0 = GEP_T->getOperand(0)->stripPointerCasts();
if (Op0 == Ptr) {
HasSameBase = true;
break;
}
GEP_T = dyn_cast<GEPOperator>(Op0);
}
if (!HasSameBase)
return None;
return OffsetVal;
};
if (GEP1) {
auto Offset = getOffsetFromBase(GEP1, Ptr2);
if (Offset)
return -*Offset;
}
if (GEP2) {
auto Offset = getOffsetFromBase(GEP2, Ptr1);
if (Offset)
return Offset;
}
// Right now we handle the case when Ptr1/Ptr2 are both GEPs with an identical
// base. After that base, they may have some number of common (and
// potentially variable) indices. After that they handle some constant
// offset, which determines their offset from each other. At this point, we
// handle no other case.
if (!GEP1 || !GEP2 || GEP1->getOperand(0) != GEP2->getOperand(0))
return None;
// Skip any common indices and track the GEP types.
unsigned Idx = 1;
for (; Idx != GEP1->getNumOperands() && Idx != GEP2->getNumOperands(); ++Idx)
if (GEP1->getOperand(Idx) != GEP2->getOperand(Idx))
break;
auto Offset1 = getOffsetFromIndex(GEP1, Idx, DL);
auto Offset2 = getOffsetFromIndex(GEP2, Idx, DL);
if (!Offset1 || !Offset2)
return None;
return *Offset2 - *Offset1;
}
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