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llvm-mirror/lib/CodeGen/Analysis.cpp
Chandler Carruth ae65e281f3 Update the file headers across all of the LLVM projects in the monorepo 
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636
2019-01-19 08:50:56 +00:00

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//===-- Analysis.cpp - CodeGen LLVM IR Analysis Utilities -----------------===//
//
// 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 defines several CodeGen-specific LLVM IR analysis utilities.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/Analysis.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Transforms/Utils/GlobalStatus.h"
using namespace llvm;
/// Compute the linearized index of a member in a nested aggregate/struct/array
/// by recursing and accumulating CurIndex as long as there are indices in the
/// index list.
unsigned llvm::ComputeLinearIndex(Type *Ty,
const unsigned *Indices,
const unsigned *IndicesEnd,
unsigned CurIndex) {
// Base case: We're done.
if (Indices && Indices == IndicesEnd)
return CurIndex;
// Given a struct type, recursively traverse the elements.
if (StructType *STy = dyn_cast<StructType>(Ty)) {
for (StructType::element_iterator EB = STy->element_begin(),
EI = EB,
EE = STy->element_end();
EI != EE; ++EI) {
if (Indices && *Indices == unsigned(EI - EB))
return ComputeLinearIndex(*EI, Indices+1, IndicesEnd, CurIndex);
CurIndex = ComputeLinearIndex(*EI, nullptr, nullptr, CurIndex);
}
assert(!Indices && "Unexpected out of bound");
return CurIndex;
}
// Given an array type, recursively traverse the elements.
else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
Type *EltTy = ATy->getElementType();
unsigned NumElts = ATy->getNumElements();
// Compute the Linear offset when jumping one element of the array
unsigned EltLinearOffset = ComputeLinearIndex(EltTy, nullptr, nullptr, 0);
if (Indices) {
assert(*Indices < NumElts && "Unexpected out of bound");
// If the indice is inside the array, compute the index to the requested
// elt and recurse inside the element with the end of the indices list
CurIndex += EltLinearOffset* *Indices;
return ComputeLinearIndex(EltTy, Indices+1, IndicesEnd, CurIndex);
}
CurIndex += EltLinearOffset*NumElts;
return CurIndex;
}
// We haven't found the type we're looking for, so keep searching.
return CurIndex + 1;
}
/// ComputeValueVTs - Given an LLVM IR type, compute a sequence of
/// EVTs that represent all the individual underlying
/// non-aggregate types that comprise it.
///
/// If Offsets is non-null, it points to a vector to be filled in
/// with the in-memory offsets of each of the individual values.
///
void llvm::ComputeValueVTs(const TargetLowering &TLI, const DataLayout &DL,
Type *Ty, SmallVectorImpl<EVT> &ValueVTs,
SmallVectorImpl<uint64_t> *Offsets,
uint64_t StartingOffset) {
// Given a struct type, recursively traverse the elements.
if (StructType *STy = dyn_cast<StructType>(Ty)) {
const StructLayout *SL = DL.getStructLayout(STy);
for (StructType::element_iterator EB = STy->element_begin(),
EI = EB,
EE = STy->element_end();
EI != EE; ++EI)
ComputeValueVTs(TLI, DL, *EI, ValueVTs, Offsets,
StartingOffset + SL->getElementOffset(EI - EB));
return;
}
// Given an array type, recursively traverse the elements.
if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
Type *EltTy = ATy->getElementType();
uint64_t EltSize = DL.getTypeAllocSize(EltTy);
for (unsigned i = 0, e = ATy->getNumElements(); i != e; ++i)
ComputeValueVTs(TLI, DL, EltTy, ValueVTs, Offsets,
StartingOffset + i * EltSize);
return;
}
// Interpret void as zero return values.
if (Ty->isVoidTy())
return;
// Base case: we can get an EVT for this LLVM IR type.
ValueVTs.push_back(TLI.getValueType(DL, Ty));
if (Offsets)
Offsets->push_back(StartingOffset);
}
/// ExtractTypeInfo - Returns the type info, possibly bitcast, encoded in V.
GlobalValue *llvm::ExtractTypeInfo(Value *V) {
V = V->stripPointerCasts();
GlobalValue *GV = dyn_cast<GlobalValue>(V);
GlobalVariable *Var = dyn_cast<GlobalVariable>(V);
if (Var && Var->getName() == "llvm.eh.catch.all.value") {
assert(Var->hasInitializer() &&
"The EH catch-all value must have an initializer");
Value *Init = Var->getInitializer();
GV = dyn_cast<GlobalValue>(Init);
if (!GV) V = cast<ConstantPointerNull>(Init);
}
assert((GV || isa<ConstantPointerNull>(V)) &&
"TypeInfo must be a global variable or NULL");
return GV;
}
/// hasInlineAsmMemConstraint - Return true if the inline asm instruction being
/// processed uses a memory 'm' constraint.
bool
llvm::hasInlineAsmMemConstraint(InlineAsm::ConstraintInfoVector &CInfos,
const TargetLowering &TLI) {
for (unsigned i = 0, e = CInfos.size(); i != e; ++i) {
InlineAsm::ConstraintInfo &CI = CInfos[i];
for (unsigned j = 0, ee = CI.Codes.size(); j != ee; ++j) {
TargetLowering::ConstraintType CType = TLI.getConstraintType(CI.Codes[j]);
if (CType == TargetLowering::C_Memory)
return true;
}
// Indirect operand accesses access memory.
if (CI.isIndirect)
return true;
}
return false;
}
/// getFCmpCondCode - Return the ISD condition code corresponding to
/// the given LLVM IR floating-point condition code. This includes
/// consideration of global floating-point math flags.
///
ISD::CondCode llvm::getFCmpCondCode(FCmpInst::Predicate Pred) {
switch (Pred) {
case FCmpInst::FCMP_FALSE: return ISD::SETFALSE;
case FCmpInst::FCMP_OEQ: return ISD::SETOEQ;
case FCmpInst::FCMP_OGT: return ISD::SETOGT;
case FCmpInst::FCMP_OGE: return ISD::SETOGE;
case FCmpInst::FCMP_OLT: return ISD::SETOLT;
case FCmpInst::FCMP_OLE: return ISD::SETOLE;
case FCmpInst::FCMP_ONE: return ISD::SETONE;
case FCmpInst::FCMP_ORD: return ISD::SETO;
case FCmpInst::FCMP_UNO: return ISD::SETUO;
case FCmpInst::FCMP_UEQ: return ISD::SETUEQ;
case FCmpInst::FCMP_UGT: return ISD::SETUGT;
case FCmpInst::FCMP_UGE: return ISD::SETUGE;
case FCmpInst::FCMP_ULT: return ISD::SETULT;
case FCmpInst::FCMP_ULE: return ISD::SETULE;
case FCmpInst::FCMP_UNE: return ISD::SETUNE;
case FCmpInst::FCMP_TRUE: return ISD::SETTRUE;
default: llvm_unreachable("Invalid FCmp predicate opcode!");
}
}
ISD::CondCode llvm::getFCmpCodeWithoutNaN(ISD::CondCode CC) {
switch (CC) {
case ISD::SETOEQ: case ISD::SETUEQ: return ISD::SETEQ;
case ISD::SETONE: case ISD::SETUNE: return ISD::SETNE;
case ISD::SETOLT: case ISD::SETULT: return ISD::SETLT;
case ISD::SETOLE: case ISD::SETULE: return ISD::SETLE;
case ISD::SETOGT: case ISD::SETUGT: return ISD::SETGT;
case ISD::SETOGE: case ISD::SETUGE: return ISD::SETGE;
default: return CC;
}
}
/// getICmpCondCode - Return the ISD condition code corresponding to
/// the given LLVM IR integer condition code.
///
ISD::CondCode llvm::getICmpCondCode(ICmpInst::Predicate Pred) {
switch (Pred) {
case ICmpInst::ICMP_EQ: return ISD::SETEQ;
case ICmpInst::ICMP_NE: return ISD::SETNE;
case ICmpInst::ICMP_SLE: return ISD::SETLE;
case ICmpInst::ICMP_ULE: return ISD::SETULE;
case ICmpInst::ICMP_SGE: return ISD::SETGE;
case ICmpInst::ICMP_UGE: return ISD::SETUGE;
case ICmpInst::ICMP_SLT: return ISD::SETLT;
case ICmpInst::ICMP_ULT: return ISD::SETULT;
case ICmpInst::ICMP_SGT: return ISD::SETGT;
case ICmpInst::ICMP_UGT: return ISD::SETUGT;
default:
llvm_unreachable("Invalid ICmp predicate opcode!");
}
}
static bool isNoopBitcast(Type *T1, Type *T2,
const TargetLoweringBase& TLI) {
return T1 == T2 || (T1->isPointerTy() && T2->isPointerTy()) ||
(isa<VectorType>(T1) && isa<VectorType>(T2) &&
TLI.isTypeLegal(EVT::getEVT(T1)) && TLI.isTypeLegal(EVT::getEVT(T2)));
}
/// Look through operations that will be free to find the earliest source of
/// this value.
///
/// @param ValLoc If V has aggegate type, we will be interested in a particular
/// scalar component. This records its address; the reverse of this list gives a
/// sequence of indices appropriate for an extractvalue to locate the important
/// value. This value is updated during the function and on exit will indicate
/// similar information for the Value returned.
///
/// @param DataBits If this function looks through truncate instructions, this
/// will record the smallest size attained.
static const Value *getNoopInput(const Value *V,
SmallVectorImpl<unsigned> &ValLoc,
unsigned &DataBits,
const TargetLoweringBase &TLI,
const DataLayout &DL) {
while (true) {
// Try to look through V1; if V1 is not an instruction, it can't be looked
// through.
const Instruction *I = dyn_cast<Instruction>(V);
if (!I || I->getNumOperands() == 0) return V;
const Value *NoopInput = nullptr;
Value *Op = I->getOperand(0);
if (isa<BitCastInst>(I)) {
// Look through truly no-op bitcasts.
if (isNoopBitcast(Op->getType(), I->getType(), TLI))
NoopInput = Op;
} else if (isa<GetElementPtrInst>(I)) {
// Look through getelementptr
if (cast<GetElementPtrInst>(I)->hasAllZeroIndices())
NoopInput = Op;
} else if (isa<IntToPtrInst>(I)) {
// Look through inttoptr.
// Make sure this isn't a truncating or extending cast. We could
// support this eventually, but don't bother for now.
if (!isa<VectorType>(I->getType()) &&
DL.getPointerSizeInBits() ==
cast<IntegerType>(Op->getType())->getBitWidth())
NoopInput = Op;
} else if (isa<PtrToIntInst>(I)) {
// Look through ptrtoint.
// Make sure this isn't a truncating or extending cast. We could
// support this eventually, but don't bother for now.
if (!isa<VectorType>(I->getType()) &&
DL.getPointerSizeInBits() ==
cast<IntegerType>(I->getType())->getBitWidth())
NoopInput = Op;
} else if (isa<TruncInst>(I) &&
TLI.allowTruncateForTailCall(Op->getType(), I->getType())) {
DataBits = std::min(DataBits, I->getType()->getPrimitiveSizeInBits());
NoopInput = Op;
} else if (auto CS = ImmutableCallSite(I)) {
const Value *ReturnedOp = CS.getReturnedArgOperand();
if (ReturnedOp && isNoopBitcast(ReturnedOp->getType(), I->getType(), TLI))
NoopInput = ReturnedOp;
} else if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(V)) {
// Value may come from either the aggregate or the scalar
ArrayRef<unsigned> InsertLoc = IVI->getIndices();
if (ValLoc.size() >= InsertLoc.size() &&
std::equal(InsertLoc.begin(), InsertLoc.end(), ValLoc.rbegin())) {
// The type being inserted is a nested sub-type of the aggregate; we
// have to remove those initial indices to get the location we're
// interested in for the operand.
ValLoc.resize(ValLoc.size() - InsertLoc.size());
NoopInput = IVI->getInsertedValueOperand();
} else {
// The struct we're inserting into has the value we're interested in, no
// change of address.
NoopInput = Op;
}
} else if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(V)) {
// The part we're interested in will inevitably be some sub-section of the
// previous aggregate. Combine the two paths to obtain the true address of
// our element.
ArrayRef<unsigned> ExtractLoc = EVI->getIndices();
ValLoc.append(ExtractLoc.rbegin(), ExtractLoc.rend());
NoopInput = Op;
}
// Terminate if we couldn't find anything to look through.
if (!NoopInput)
return V;
V = NoopInput;
}
}
/// Return true if this scalar return value only has bits discarded on its path
/// from the "tail call" to the "ret". This includes the obvious noop
/// instructions handled by getNoopInput above as well as free truncations (or
/// extensions prior to the call).
static bool slotOnlyDiscardsData(const Value *RetVal, const Value *CallVal,
SmallVectorImpl<unsigned> &RetIndices,
SmallVectorImpl<unsigned> &CallIndices,
bool AllowDifferingSizes,
const TargetLoweringBase &TLI,
const DataLayout &DL) {
// Trace the sub-value needed by the return value as far back up the graph as
// possible, in the hope that it will intersect with the value produced by the
// call. In the simple case with no "returned" attribute, the hope is actually
// that we end up back at the tail call instruction itself.
unsigned BitsRequired = UINT_MAX;
RetVal = getNoopInput(RetVal, RetIndices, BitsRequired, TLI, DL);
// If this slot in the value returned is undef, it doesn't matter what the
// call puts there, it'll be fine.
if (isa<UndefValue>(RetVal))
return true;
// Now do a similar search up through the graph to find where the value
// actually returned by the "tail call" comes from. In the simple case without
// a "returned" attribute, the search will be blocked immediately and the loop
// a Noop.
unsigned BitsProvided = UINT_MAX;
CallVal = getNoopInput(CallVal, CallIndices, BitsProvided, TLI, DL);
// There's no hope if we can't actually trace them to (the same part of!) the
// same value.
if (CallVal != RetVal || CallIndices != RetIndices)
return false;
// However, intervening truncates may have made the call non-tail. Make sure
// all the bits that are needed by the "ret" have been provided by the "tail
// call". FIXME: with sufficiently cunning bit-tracking, we could look through
// extensions too.
if (BitsProvided < BitsRequired ||
(!AllowDifferingSizes && BitsProvided != BitsRequired))
return false;
return true;
}
/// For an aggregate type, determine whether a given index is within bounds or
/// not.
static bool indexReallyValid(CompositeType *T, unsigned Idx) {
if (ArrayType *AT = dyn_cast<ArrayType>(T))
return Idx < AT->getNumElements();
return Idx < cast<StructType>(T)->getNumElements();
}
/// Move the given iterators to the next leaf type in depth first traversal.
///
/// Performs a depth-first traversal of the type as specified by its arguments,
/// stopping at the next leaf node (which may be a legitimate scalar type or an
/// empty struct or array).
///
/// @param SubTypes List of the partial components making up the type from
/// outermost to innermost non-empty aggregate. The element currently
/// represented is SubTypes.back()->getTypeAtIndex(Path.back() - 1).
///
/// @param Path Set of extractvalue indices leading from the outermost type
/// (SubTypes[0]) to the leaf node currently represented.
///
/// @returns true if a new type was found, false otherwise. Calling this
/// function again on a finished iterator will repeatedly return
/// false. SubTypes.back()->getTypeAtIndex(Path.back()) is either an empty
/// aggregate or a non-aggregate
static bool advanceToNextLeafType(SmallVectorImpl<CompositeType *> &SubTypes,
SmallVectorImpl<unsigned> &Path) {
// First march back up the tree until we can successfully increment one of the
// coordinates in Path.
while (!Path.empty() && !indexReallyValid(SubTypes.back(), Path.back() + 1)) {
Path.pop_back();
SubTypes.pop_back();
}
// If we reached the top, then the iterator is done.
if (Path.empty())
return false;
// We know there's *some* valid leaf now, so march back down the tree picking
// out the left-most element at each node.
++Path.back();
Type *DeeperType = SubTypes.back()->getTypeAtIndex(Path.back());
while (DeeperType->isAggregateType()) {
CompositeType *CT = cast<CompositeType>(DeeperType);
if (!indexReallyValid(CT, 0))
return true;
SubTypes.push_back(CT);
Path.push_back(0);
DeeperType = CT->getTypeAtIndex(0U);
}
return true;
}
/// Find the first non-empty, scalar-like type in Next and setup the iterator
/// components.
///
/// Assuming Next is an aggregate of some kind, this function will traverse the
/// tree from left to right (i.e. depth-first) looking for the first
/// non-aggregate type which will play a role in function return.
///
/// For example, if Next was {[0 x i64], {{}, i32, {}}, i32} then we would setup
/// Path as [1, 1] and SubTypes as [Next, {{}, i32, {}}] to represent the first
/// i32 in that type.
static bool firstRealType(Type *Next,
SmallVectorImpl<CompositeType *> &SubTypes,
SmallVectorImpl<unsigned> &Path) {
// First initialise the iterator components to the first "leaf" node
// (i.e. node with no valid sub-type at any index, so {} does count as a leaf
// despite nominally being an aggregate).
while (Next->isAggregateType() &&
indexReallyValid(cast<CompositeType>(Next), 0)) {
SubTypes.push_back(cast<CompositeType>(Next));
Path.push_back(0);
Next = cast<CompositeType>(Next)->getTypeAtIndex(0U);
}
// If there's no Path now, Next was originally scalar already (or empty
// leaf). We're done.
if (Path.empty())
return true;
// Otherwise, use normal iteration to keep looking through the tree until we
// find a non-aggregate type.
while (SubTypes.back()->getTypeAtIndex(Path.back())->isAggregateType()) {
if (!advanceToNextLeafType(SubTypes, Path))
return false;
}
return true;
}
/// Set the iterator data-structures to the next non-empty, non-aggregate
/// subtype.
static bool nextRealType(SmallVectorImpl<CompositeType *> &SubTypes,
SmallVectorImpl<unsigned> &Path) {
do {
if (!advanceToNextLeafType(SubTypes, Path))
return false;
assert(!Path.empty() && "found a leaf but didn't set the path?");
} while (SubTypes.back()->getTypeAtIndex(Path.back())->isAggregateType());
return true;
}
/// Test if the given instruction is in a position to be optimized
/// with a tail-call. This roughly means that it's in a block with
/// a return and there's nothing that needs to be scheduled
/// between it and the return.
///
/// This function only tests target-independent requirements.
bool llvm::isInTailCallPosition(ImmutableCallSite CS, const TargetMachine &TM) {
const Instruction *I = CS.getInstruction();
const BasicBlock *ExitBB = I->getParent();
const Instruction *Term = ExitBB->getTerminator();
const ReturnInst *Ret = dyn_cast<ReturnInst>(Term);
// The block must end in a return statement or unreachable.
//
// FIXME: Decline tailcall if it's not guaranteed and if the block ends in
// an unreachable, for now. The way tailcall optimization is currently
// implemented means it will add an epilogue followed by a jump. That is
// not profitable. Also, if the callee is a special function (e.g.
// longjmp on x86), it can end up causing miscompilation that has not
// been fully understood.
if (!Ret &&
(!TM.Options.GuaranteedTailCallOpt || !isa<UnreachableInst>(Term)))
return false;
// If I will have a chain, make sure no other instruction that will have a
// chain interposes between I and the return.
if (I->mayHaveSideEffects() || I->mayReadFromMemory() ||
!isSafeToSpeculativelyExecute(I))
for (BasicBlock::const_iterator BBI = std::prev(ExitBB->end(), 2);; --BBI) {
if (&*BBI == I)
break;
// Debug info intrinsics do not get in the way of tail call optimization.
if (isa<DbgInfoIntrinsic>(BBI))
continue;
// A lifetime end intrinsic should not stop tail call optimization.
if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(BBI))
if (II->getIntrinsicID() == Intrinsic::lifetime_end)
continue;
if (BBI->mayHaveSideEffects() || BBI->mayReadFromMemory() ||
!isSafeToSpeculativelyExecute(&*BBI))
return false;
}
const Function *F = ExitBB->getParent();
return returnTypeIsEligibleForTailCall(
F, I, Ret, *TM.getSubtargetImpl(*F)->getTargetLowering());
}
bool llvm::attributesPermitTailCall(const Function *F, const Instruction *I,
const ReturnInst *Ret,
const TargetLoweringBase &TLI,
bool *AllowDifferingSizes) {
// ADS may be null, so don't write to it directly.
bool DummyADS;
bool &ADS = AllowDifferingSizes ? *AllowDifferingSizes : DummyADS;
ADS = true;
AttrBuilder CallerAttrs(F->getAttributes(), AttributeList::ReturnIndex);
AttrBuilder CalleeAttrs(cast<CallInst>(I)->getAttributes(),
AttributeList::ReturnIndex);
// NoAlias and NonNull are completely benign as far as calling convention
// goes, they shouldn't affect whether the call is a tail call.
CallerAttrs.removeAttribute(Attribute::NoAlias);
CalleeAttrs.removeAttribute(Attribute::NoAlias);
CallerAttrs.removeAttribute(Attribute::NonNull);
CalleeAttrs.removeAttribute(Attribute::NonNull);
if (CallerAttrs.contains(Attribute::ZExt)) {
if (!CalleeAttrs.contains(Attribute::ZExt))
return false;
ADS = false;
CallerAttrs.removeAttribute(Attribute::ZExt);
CalleeAttrs.removeAttribute(Attribute::ZExt);
} else if (CallerAttrs.contains(Attribute::SExt)) {
if (!CalleeAttrs.contains(Attribute::SExt))
return false;
ADS = false;
CallerAttrs.removeAttribute(Attribute::SExt);
CalleeAttrs.removeAttribute(Attribute::SExt);
}
// Drop sext and zext return attributes if the result is not used.
// This enables tail calls for code like:
//
// define void @caller() {
// entry:
// %unused_result = tail call zeroext i1 @callee()
// br label %retlabel
// retlabel:
// ret void
// }
if (I->use_empty()) {
CalleeAttrs.removeAttribute(Attribute::SExt);
CalleeAttrs.removeAttribute(Attribute::ZExt);
}
// If they're still different, there's some facet we don't understand
// (currently only "inreg", but in future who knows). It may be OK but the
// only safe option is to reject the tail call.
return CallerAttrs == CalleeAttrs;
}
bool llvm::returnTypeIsEligibleForTailCall(const Function *F,
const Instruction *I,
const ReturnInst *Ret,
const TargetLoweringBase &TLI) {
// If the block ends with a void return or unreachable, it doesn't matter
// what the call's return type is.
if (!Ret || Ret->getNumOperands() == 0) return true;
// If the return value is undef, it doesn't matter what the call's
// return type is.
if (isa<UndefValue>(Ret->getOperand(0))) return true;
// Make sure the attributes attached to each return are compatible.
bool AllowDifferingSizes;
if (!attributesPermitTailCall(F, I, Ret, TLI, &AllowDifferingSizes))
return false;
const Value *RetVal = Ret->getOperand(0), *CallVal = I;
// Intrinsic like llvm.memcpy has no return value, but the expanded
// libcall may or may not have return value. On most platforms, it
// will be expanded as memcpy in libc, which returns the first
// argument. On other platforms like arm-none-eabi, memcpy may be
// expanded as library call without return value, like __aeabi_memcpy.
const CallInst *Call = cast<CallInst>(I);
if (Function *F = Call->getCalledFunction()) {
Intrinsic::ID IID = F->getIntrinsicID();
if (((IID == Intrinsic::memcpy &&
TLI.getLibcallName(RTLIB::MEMCPY) == StringRef("memcpy")) ||
(IID == Intrinsic::memmove &&
TLI.getLibcallName(RTLIB::MEMMOVE) == StringRef("memmove")) ||
(IID == Intrinsic::memset &&
TLI.getLibcallName(RTLIB::MEMSET) == StringRef("memset"))) &&
RetVal == Call->getArgOperand(0))
return true;
}
SmallVector<unsigned, 4> RetPath, CallPath;
SmallVector<CompositeType *, 4> RetSubTypes, CallSubTypes;
bool RetEmpty = !firstRealType(RetVal->getType(), RetSubTypes, RetPath);
bool CallEmpty = !firstRealType(CallVal->getType(), CallSubTypes, CallPath);
// Nothing's actually returned, it doesn't matter what the callee put there
// it's a valid tail call.
if (RetEmpty)
return true;
// Iterate pairwise through each of the value types making up the tail call
// and the corresponding return. For each one we want to know whether it's
// essentially going directly from the tail call to the ret, via operations
// that end up not generating any code.
//
// We allow a certain amount of covariance here. For example it's permitted
// for the tail call to define more bits than the ret actually cares about
// (e.g. via a truncate).
do {
if (CallEmpty) {
// We've exhausted the values produced by the tail call instruction, the
// rest are essentially undef. The type doesn't really matter, but we need
// *something*.
Type *SlotType = RetSubTypes.back()->getTypeAtIndex(RetPath.back());
CallVal = UndefValue::get(SlotType);
}
// The manipulations performed when we're looking through an insertvalue or
// an extractvalue would happen at the front of the RetPath list, so since
// we have to copy it anyway it's more efficient to create a reversed copy.
SmallVector<unsigned, 4> TmpRetPath(RetPath.rbegin(), RetPath.rend());
SmallVector<unsigned, 4> TmpCallPath(CallPath.rbegin(), CallPath.rend());
// Finally, we can check whether the value produced by the tail call at this
// index is compatible with the value we return.
if (!slotOnlyDiscardsData(RetVal, CallVal, TmpRetPath, TmpCallPath,
AllowDifferingSizes, TLI,
F->getParent()->getDataLayout()))
return false;
CallEmpty = !nextRealType(CallSubTypes, CallPath);
} while(nextRealType(RetSubTypes, RetPath));
return true;
}
static void collectEHScopeMembers(
DenseMap<const MachineBasicBlock *, int> &EHScopeMembership, int EHScope,
const MachineBasicBlock *MBB) {
SmallVector<const MachineBasicBlock *, 16> Worklist = {MBB};
while (!Worklist.empty()) {
const MachineBasicBlock *Visiting = Worklist.pop_back_val();
// Don't follow blocks which start new scopes.
if (Visiting->isEHPad() && Visiting != MBB)
continue;
// Add this MBB to our scope.
auto P = EHScopeMembership.insert(std::make_pair(Visiting, EHScope));
// Don't revisit blocks.
if (!P.second) {
assert(P.first->second == EHScope && "MBB is part of two scopes!");
continue;
}
// Returns are boundaries where scope transfer can occur, don't follow
// successors.
if (Visiting->isEHScopeReturnBlock())
continue;
for (const MachineBasicBlock *Succ : Visiting->successors())
Worklist.push_back(Succ);
}
}
DenseMap<const MachineBasicBlock *, int>
llvm::getEHScopeMembership(const MachineFunction &MF) {
DenseMap<const MachineBasicBlock *, int> EHScopeMembership;
// We don't have anything to do if there aren't any EH pads.
if (!MF.hasEHScopes())
return EHScopeMembership;
int EntryBBNumber = MF.front().getNumber();
bool IsSEH = isAsynchronousEHPersonality(
classifyEHPersonality(MF.getFunction().getPersonalityFn()));
const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
SmallVector<const MachineBasicBlock *, 16> EHScopeBlocks;
SmallVector<const MachineBasicBlock *, 16> UnreachableBlocks;
SmallVector<const MachineBasicBlock *, 16> SEHCatchPads;
SmallVector<std::pair<const MachineBasicBlock *, int>, 16> CatchRetSuccessors;
for (const MachineBasicBlock &MBB : MF) {
if (MBB.isEHScopeEntry()) {
EHScopeBlocks.push_back(&MBB);
} else if (IsSEH && MBB.isEHPad()) {
SEHCatchPads.push_back(&MBB);
} else if (MBB.pred_empty()) {
UnreachableBlocks.push_back(&MBB);
}
MachineBasicBlock::const_iterator MBBI = MBB.getFirstTerminator();
// CatchPads are not scopes for SEH so do not consider CatchRet to
// transfer control to another scope.
if (MBBI == MBB.end() || MBBI->getOpcode() != TII->getCatchReturnOpcode())
continue;
// FIXME: SEH CatchPads are not necessarily in the parent function:
// they could be inside a finally block.
const MachineBasicBlock *Successor = MBBI->getOperand(0).getMBB();
const MachineBasicBlock *SuccessorColor = MBBI->getOperand(1).getMBB();
CatchRetSuccessors.push_back(
{Successor, IsSEH ? EntryBBNumber : SuccessorColor->getNumber()});
}
// We don't have anything to do if there aren't any EH pads.
if (EHScopeBlocks.empty())
return EHScopeMembership;
// Identify all the basic blocks reachable from the function entry.
collectEHScopeMembers(EHScopeMembership, EntryBBNumber, &MF.front());
// All blocks not part of a scope are in the parent function.
for (const MachineBasicBlock *MBB : UnreachableBlocks)
collectEHScopeMembers(EHScopeMembership, EntryBBNumber, MBB);
// Next, identify all the blocks inside the scopes.
for (const MachineBasicBlock *MBB : EHScopeBlocks)
collectEHScopeMembers(EHScopeMembership, MBB->getNumber(), MBB);
// SEH CatchPads aren't really scopes, handle them separately.
for (const MachineBasicBlock *MBB : SEHCatchPads)
collectEHScopeMembers(EHScopeMembership, EntryBBNumber, MBB);
// Finally, identify all the targets of a catchret.
for (std::pair<const MachineBasicBlock *, int> CatchRetPair :
CatchRetSuccessors)
collectEHScopeMembers(EHScopeMembership, CatchRetPair.second,
CatchRetPair.first);
return EHScopeMembership;
}
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