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llvm-mirror/lib/Transforms/Utils/PredicateInfo.cpp
Nikita Popov 067f635646 [PredicateInfo][SCCP] Remove assertion (PR46814) 
As long as RenamedOp is not guaranteed to be accurate, we cannot
assert here and should just return false. This was already done
for the other conditions in this function.

Fixes https://bugs.llvm.org/show_bug.cgi?id=46814.
2020-07-23 19:36:51 +02:00

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//===-- PredicateInfo.cpp - PredicateInfo Builder--------------------===//
//
// 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 implements the PredicateInfo class.
//
//===----------------------------------------------------------------===//
#include "llvm/Transforms/Utils/PredicateInfo.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/CFG.h"
#include "llvm/IR/AssemblyAnnotationWriter.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/InitializePasses.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/DebugCounter.h"
#include "llvm/Support/FormattedStream.h"
#include "llvm/Transforms/Utils.h"
#include <algorithm>
#define DEBUG_TYPE "predicateinfo"
using namespace llvm;
using namespace PatternMatch;
INITIALIZE_PASS_BEGIN(PredicateInfoPrinterLegacyPass, "print-predicateinfo",
"PredicateInfo Printer", false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
INITIALIZE_PASS_END(PredicateInfoPrinterLegacyPass, "print-predicateinfo",
"PredicateInfo Printer", false, false)
static cl::opt<bool> VerifyPredicateInfo(
"verify-predicateinfo", cl::init(false), cl::Hidden,
cl::desc("Verify PredicateInfo in legacy printer pass."));
DEBUG_COUNTER(RenameCounter, "predicateinfo-rename",
"Controls which variables are renamed with predicateinfo");
namespace {
// Given a predicate info that is a type of branching terminator, get the
// branching block.
const BasicBlock *getBranchBlock(const PredicateBase *PB) {
assert(isa<PredicateWithEdge>(PB) &&
"Only branches and switches should have PHIOnly defs that "
"require branch blocks.");
return cast<PredicateWithEdge>(PB)->From;
}
// Given a predicate info that is a type of branching terminator, get the
// branching terminator.
static Instruction *getBranchTerminator(const PredicateBase *PB) {
assert(isa<PredicateWithEdge>(PB) &&
"Not a predicate info type we know how to get a terminator from.");
return cast<PredicateWithEdge>(PB)->From->getTerminator();
}
// Given a predicate info that is a type of branching terminator, get the
// edge this predicate info represents
const std::pair<BasicBlock *, BasicBlock *>
getBlockEdge(const PredicateBase *PB) {
assert(isa<PredicateWithEdge>(PB) &&
"Not a predicate info type we know how to get an edge from.");
const auto *PEdge = cast<PredicateWithEdge>(PB);
return std::make_pair(PEdge->From, PEdge->To);
}
}
namespace llvm {
enum LocalNum {
// Operations that must appear first in the block.
LN_First,
// Operations that are somewhere in the middle of the block, and are sorted on
// demand.
LN_Middle,
// Operations that must appear last in a block, like successor phi node uses.
LN_Last
};
// Associate global and local DFS info with defs and uses, so we can sort them
// into a global domination ordering.
struct ValueDFS {
int DFSIn = 0;
int DFSOut = 0;
unsigned int LocalNum = LN_Middle;
// Only one of Def or Use will be set.
Value *Def = nullptr;
Use *U = nullptr;
// Neither PInfo nor EdgeOnly participate in the ordering
PredicateBase *PInfo = nullptr;
bool EdgeOnly = false;
};
// Perform a strict weak ordering on instructions and arguments.
static bool valueComesBefore(const Value *A, const Value *B) {
auto *ArgA = dyn_cast_or_null<Argument>(A);
auto *ArgB = dyn_cast_or_null<Argument>(B);
if (ArgA && !ArgB)
return true;
if (ArgB && !ArgA)
return false;
if (ArgA && ArgB)
return ArgA->getArgNo() < ArgB->getArgNo();
return cast<Instruction>(A)->comesBefore(cast<Instruction>(B));
}
// This compares ValueDFS structures. Doing so allows us to walk the minimum
// number of instructions necessary to compute our def/use ordering.
struct ValueDFS_Compare {
DominatorTree &DT;
ValueDFS_Compare(DominatorTree &DT) : DT(DT) {}
bool operator()(const ValueDFS &A, const ValueDFS &B) const {
if (&A == &B)
return false;
// The only case we can't directly compare them is when they in the same
// block, and both have localnum == middle. In that case, we have to use
// comesbefore to see what the real ordering is, because they are in the
// same basic block.
assert((A.DFSIn != B.DFSIn || A.DFSOut == B.DFSOut) &&
"Equal DFS-in numbers imply equal out numbers");
bool SameBlock = A.DFSIn == B.DFSIn;
// We want to put the def that will get used for a given set of phi uses,
// before those phi uses.
// So we sort by edge, then by def.
// Note that only phi nodes uses and defs can come last.
if (SameBlock && A.LocalNum == LN_Last && B.LocalNum == LN_Last)
return comparePHIRelated(A, B);
bool isADef = A.Def;
bool isBDef = B.Def;
if (!SameBlock || A.LocalNum != LN_Middle || B.LocalNum != LN_Middle)
return std::tie(A.DFSIn, A.LocalNum, isADef) <
std::tie(B.DFSIn, B.LocalNum, isBDef);
return localComesBefore(A, B);
}
// For a phi use, or a non-materialized def, return the edge it represents.
const std::pair<BasicBlock *, BasicBlock *>
getBlockEdge(const ValueDFS &VD) const {
if (!VD.Def && VD.U) {
auto *PHI = cast<PHINode>(VD.U->getUser());
return std::make_pair(PHI->getIncomingBlock(*VD.U), PHI->getParent());
}
// This is really a non-materialized def.
return ::getBlockEdge(VD.PInfo);
}
// For two phi related values, return the ordering.
bool comparePHIRelated(const ValueDFS &A, const ValueDFS &B) const {
BasicBlock *ASrc, *ADest, *BSrc, *BDest;
std::tie(ASrc, ADest) = getBlockEdge(A);
std::tie(BSrc, BDest) = getBlockEdge(B);
#ifndef NDEBUG
// This function should only be used for values in the same BB, check that.
DomTreeNode *DomASrc = DT.getNode(ASrc);
DomTreeNode *DomBSrc = DT.getNode(BSrc);
assert(DomASrc->getDFSNumIn() == (unsigned)A.DFSIn &&
"DFS numbers for A should match the ones of the source block");
assert(DomBSrc->getDFSNumIn() == (unsigned)B.DFSIn &&
"DFS numbers for B should match the ones of the source block");
assert(A.DFSIn == B.DFSIn && "Values must be in the same block");
#endif
(void)ASrc;
(void)BSrc;
// Use DFS numbers to compare destination blocks, to guarantee a
// deterministic order.
DomTreeNode *DomADest = DT.getNode(ADest);
DomTreeNode *DomBDest = DT.getNode(BDest);
unsigned AIn = DomADest->getDFSNumIn();
unsigned BIn = DomBDest->getDFSNumIn();
bool isADef = A.Def;
bool isBDef = B.Def;
assert((!A.Def || !A.U) && (!B.Def || !B.U) &&
"Def and U cannot be set at the same time");
// Now sort by edge destination and then defs before uses.
return std::tie(AIn, isADef) < std::tie(BIn, isBDef);
}
// Get the definition of an instruction that occurs in the middle of a block.
Value *getMiddleDef(const ValueDFS &VD) const {
if (VD.Def)
return VD.Def;
// It's possible for the defs and uses to be null. For branches, the local
// numbering will say the placed predicaeinfos should go first (IE
// LN_beginning), so we won't be in this function. For assumes, we will end
// up here, beause we need to order the def we will place relative to the
// assume. So for the purpose of ordering, we pretend the def is right
// after the assume, because that is where we will insert the info.
if (!VD.U) {
assert(VD.PInfo &&
"No def, no use, and no predicateinfo should not occur");
assert(isa<PredicateAssume>(VD.PInfo) &&
"Middle of block should only occur for assumes");
return cast<PredicateAssume>(VD.PInfo)->AssumeInst->getNextNode();
}
return nullptr;
}
// Return either the Def, if it's not null, or the user of the Use, if the def
// is null.
const Instruction *getDefOrUser(const Value *Def, const Use *U) const {
if (Def)
return cast<Instruction>(Def);
return cast<Instruction>(U->getUser());
}
// This performs the necessary local basic block ordering checks to tell
// whether A comes before B, where both are in the same basic block.
bool localComesBefore(const ValueDFS &A, const ValueDFS &B) const {
auto *ADef = getMiddleDef(A);
auto *BDef = getMiddleDef(B);
// See if we have real values or uses. If we have real values, we are
// guaranteed they are instructions or arguments. No matter what, we are
// guaranteed they are in the same block if they are instructions.
auto *ArgA = dyn_cast_or_null<Argument>(ADef);
auto *ArgB = dyn_cast_or_null<Argument>(BDef);
if (ArgA || ArgB)
return valueComesBefore(ArgA, ArgB);
auto *AInst = getDefOrUser(ADef, A.U);
auto *BInst = getDefOrUser(BDef, B.U);
return valueComesBefore(AInst, BInst);
}
};
class PredicateInfoBuilder {
// Used to store information about each value we might rename.
struct ValueInfo {
SmallVector<PredicateBase *, 4> Infos;
};
PredicateInfo &PI;
Function &F;
DominatorTree &DT;
AssumptionCache &AC;
// This stores info about each operand or comparison result we make copies
// of. The real ValueInfos start at index 1, index 0 is unused so that we
// can more easily detect invalid indexing.
SmallVector<ValueInfo, 32> ValueInfos;
// This gives the index into the ValueInfos array for a given Value. Because
// 0 is not a valid Value Info index, you can use DenseMap::lookup and tell
// whether it returned a valid result.
DenseMap<Value *, unsigned int> ValueInfoNums;
// The set of edges along which we can only handle phi uses, due to critical
// edges.
DenseSet<std::pair<BasicBlock *, BasicBlock *>> EdgeUsesOnly;
ValueInfo &getOrCreateValueInfo(Value *);
const ValueInfo &getValueInfo(Value *) const;
void processAssume(IntrinsicInst *, BasicBlock *,
SmallVectorImpl<Value *> &OpsToRename);
void processBranch(BranchInst *, BasicBlock *,
SmallVectorImpl<Value *> &OpsToRename);
void processSwitch(SwitchInst *, BasicBlock *,
SmallVectorImpl<Value *> &OpsToRename);
void renameUses(SmallVectorImpl<Value *> &OpsToRename);
void addInfoFor(SmallVectorImpl<Value *> &OpsToRename, Value *Op,
PredicateBase *PB);
typedef SmallVectorImpl<ValueDFS> ValueDFSStack;
void convertUsesToDFSOrdered(Value *, SmallVectorImpl<ValueDFS> &);
Value *materializeStack(unsigned int &, ValueDFSStack &, Value *);
bool stackIsInScope(const ValueDFSStack &, const ValueDFS &) const;
void popStackUntilDFSScope(ValueDFSStack &, const ValueDFS &);
public:
PredicateInfoBuilder(PredicateInfo &PI, Function &F, DominatorTree &DT,
AssumptionCache &AC)
: PI(PI), F(F), DT(DT), AC(AC) {
// Push an empty operand info so that we can detect 0 as not finding one
ValueInfos.resize(1);
}
void buildPredicateInfo();
};
bool PredicateInfoBuilder::stackIsInScope(const ValueDFSStack &Stack,
const ValueDFS &VDUse) const {
if (Stack.empty())
return false;
// If it's a phi only use, make sure it's for this phi node edge, and that the
// use is in a phi node. If it's anything else, and the top of the stack is
// EdgeOnly, we need to pop the stack. We deliberately sort phi uses next to
// the defs they must go with so that we can know it's time to pop the stack
// when we hit the end of the phi uses for a given def.
if (Stack.back().EdgeOnly) {
if (!VDUse.U)
return false;
auto *PHI = dyn_cast<PHINode>(VDUse.U->getUser());
if (!PHI)
return false;
// Check edge
BasicBlock *EdgePred = PHI->getIncomingBlock(*VDUse.U);
if (EdgePred != getBranchBlock(Stack.back().PInfo))
return false;
// Use dominates, which knows how to handle edge dominance.
return DT.dominates(getBlockEdge(Stack.back().PInfo), *VDUse.U);
}
return (VDUse.DFSIn >= Stack.back().DFSIn &&
VDUse.DFSOut <= Stack.back().DFSOut);
}
void PredicateInfoBuilder::popStackUntilDFSScope(ValueDFSStack &Stack,
const ValueDFS &VD) {
while (!Stack.empty() && !stackIsInScope(Stack, VD))
Stack.pop_back();
}
// Convert the uses of Op into a vector of uses, associating global and local
// DFS info with each one.
void PredicateInfoBuilder::convertUsesToDFSOrdered(
Value *Op, SmallVectorImpl<ValueDFS> &DFSOrderedSet) {
for (auto &U : Op->uses()) {
if (auto *I = dyn_cast<Instruction>(U.getUser())) {
ValueDFS VD;
// Put the phi node uses in the incoming block.
BasicBlock *IBlock;
if (auto *PN = dyn_cast<PHINode>(I)) {
IBlock = PN->getIncomingBlock(U);
// Make phi node users appear last in the incoming block
// they are from.
VD.LocalNum = LN_Last;
} else {
// If it's not a phi node use, it is somewhere in the middle of the
// block.
IBlock = I->getParent();
VD.LocalNum = LN_Middle;
}
DomTreeNode *DomNode = DT.getNode(IBlock);
// It's possible our use is in an unreachable block. Skip it if so.
if (!DomNode)
continue;
VD.DFSIn = DomNode->getDFSNumIn();
VD.DFSOut = DomNode->getDFSNumOut();
VD.U = &U;
DFSOrderedSet.push_back(VD);
}
}
}
// Collect relevant operations from Comparison that we may want to insert copies
// for.
void collectCmpOps(CmpInst *Comparison, SmallVectorImpl<Value *> &CmpOperands) {
auto *Op0 = Comparison->getOperand(0);
auto *Op1 = Comparison->getOperand(1);
if (Op0 == Op1)
return;
CmpOperands.push_back(Comparison);
// Only want real values, not constants. Additionally, operands with one use
// are only being used in the comparison, which means they will not be useful
// for us to consider for predicateinfo.
//
if ((isa<Instruction>(Op0) || isa<Argument>(Op0)) && !Op0->hasOneUse())
CmpOperands.push_back(Op0);
if ((isa<Instruction>(Op1) || isa<Argument>(Op1)) && !Op1->hasOneUse())
CmpOperands.push_back(Op1);
}
// Add Op, PB to the list of value infos for Op, and mark Op to be renamed.
void PredicateInfoBuilder::addInfoFor(SmallVectorImpl<Value *> &OpsToRename,
Value *Op, PredicateBase *PB) {
auto &OperandInfo = getOrCreateValueInfo(Op);
if (OperandInfo.Infos.empty())
OpsToRename.push_back(Op);
PI.AllInfos.push_back(PB);
OperandInfo.Infos.push_back(PB);
}
// Process an assume instruction and place relevant operations we want to rename
// into OpsToRename.
void PredicateInfoBuilder::processAssume(
IntrinsicInst *II, BasicBlock *AssumeBB,
SmallVectorImpl<Value *> &OpsToRename) {
// See if we have a comparison we support
SmallVector<Value *, 8> CmpOperands;
SmallVector<Value *, 2> ConditionsToProcess;
CmpInst::Predicate Pred;
Value *Operand = II->getOperand(0);
if (m_c_And(m_Cmp(Pred, m_Value(), m_Value()),
m_Cmp(Pred, m_Value(), m_Value()))
.match(II->getOperand(0))) {
ConditionsToProcess.push_back(cast<BinaryOperator>(Operand)->getOperand(0));
ConditionsToProcess.push_back(cast<BinaryOperator>(Operand)->getOperand(1));
ConditionsToProcess.push_back(Operand);
} else if (isa<CmpInst>(Operand)) {
ConditionsToProcess.push_back(Operand);
}
for (auto Cond : ConditionsToProcess) {
if (auto *Cmp = dyn_cast<CmpInst>(Cond)) {
collectCmpOps(Cmp, CmpOperands);
// Now add our copy infos for our operands
for (auto *Op : CmpOperands) {
auto *PA = new PredicateAssume(Op, II, Cmp);
addInfoFor(OpsToRename, Op, PA);
}
CmpOperands.clear();
} else if (auto *BinOp = dyn_cast<BinaryOperator>(Cond)) {
// Otherwise, it should be an AND.
assert(BinOp->getOpcode() == Instruction::And &&
"Should have been an AND");
auto *PA = new PredicateAssume(BinOp, II, BinOp);
addInfoFor(OpsToRename, BinOp, PA);
} else {
llvm_unreachable("Unknown type of condition");
}
}
}
// Process a block terminating branch, and place relevant operations to be
// renamed into OpsToRename.
void PredicateInfoBuilder::processBranch(
BranchInst *BI, BasicBlock *BranchBB,
SmallVectorImpl<Value *> &OpsToRename) {
BasicBlock *FirstBB = BI->getSuccessor(0);
BasicBlock *SecondBB = BI->getSuccessor(1);
SmallVector<BasicBlock *, 2> SuccsToProcess;
SuccsToProcess.push_back(FirstBB);
SuccsToProcess.push_back(SecondBB);
SmallVector<Value *, 2> ConditionsToProcess;
auto InsertHelper = [&](Value *Op, bool isAnd, bool isOr, Value *Cond) {
for (auto *Succ : SuccsToProcess) {
// Don't try to insert on a self-edge. This is mainly because we will
// eliminate during renaming anyway.
if (Succ == BranchBB)
continue;
bool TakenEdge = (Succ == FirstBB);
// For and, only insert on the true edge
// For or, only insert on the false edge
if ((isAnd && !TakenEdge) || (isOr && TakenEdge))
continue;
PredicateBase *PB =
new PredicateBranch(Op, BranchBB, Succ, Cond, TakenEdge);
addInfoFor(OpsToRename, Op, PB);
if (!Succ->getSinglePredecessor())
EdgeUsesOnly.insert({BranchBB, Succ});
}
};
// Match combinations of conditions.
CmpInst::Predicate Pred;
bool isAnd = false;
bool isOr = false;
SmallVector<Value *, 8> CmpOperands;
if (match(BI->getCondition(), m_And(m_Cmp(Pred, m_Value(), m_Value()),
m_Cmp(Pred, m_Value(), m_Value()))) ||
match(BI->getCondition(), m_Or(m_Cmp(Pred, m_Value(), m_Value()),
m_Cmp(Pred, m_Value(), m_Value())))) {
auto *BinOp = cast<BinaryOperator>(BI->getCondition());
if (BinOp->getOpcode() == Instruction::And)
isAnd = true;
else if (BinOp->getOpcode() == Instruction::Or)
isOr = true;
ConditionsToProcess.push_back(BinOp->getOperand(0));
ConditionsToProcess.push_back(BinOp->getOperand(1));
ConditionsToProcess.push_back(BI->getCondition());
} else if (isa<CmpInst>(BI->getCondition())) {
ConditionsToProcess.push_back(BI->getCondition());
}
for (auto Cond : ConditionsToProcess) {
if (auto *Cmp = dyn_cast<CmpInst>(Cond)) {
collectCmpOps(Cmp, CmpOperands);
// Now add our copy infos for our operands
for (auto *Op : CmpOperands)
InsertHelper(Op, isAnd, isOr, Cmp);
} else if (auto *BinOp = dyn_cast<BinaryOperator>(Cond)) {
// This must be an AND or an OR.
assert((BinOp->getOpcode() == Instruction::And ||
BinOp->getOpcode() == Instruction::Or) &&
"Should have been an AND or an OR");
// The actual value of the binop is not subject to the same restrictions
// as the comparison. It's either true or false on the true/false branch.
InsertHelper(BinOp, false, false, BinOp);
} else {
llvm_unreachable("Unknown type of condition");
}
CmpOperands.clear();
}
}
// Process a block terminating switch, and place relevant operations to be
// renamed into OpsToRename.
void PredicateInfoBuilder::processSwitch(
SwitchInst *SI, BasicBlock *BranchBB,
SmallVectorImpl<Value *> &OpsToRename) {
Value *Op = SI->getCondition();
if ((!isa<Instruction>(Op) && !isa<Argument>(Op)) || Op->hasOneUse())
return;
// Remember how many outgoing edges there are to every successor.
SmallDenseMap<BasicBlock *, unsigned, 16> SwitchEdges;
for (unsigned i = 0, e = SI->getNumSuccessors(); i != e; ++i) {
BasicBlock *TargetBlock = SI->getSuccessor(i);
++SwitchEdges[TargetBlock];
}
// Now propagate info for each case value
for (auto C : SI->cases()) {
BasicBlock *TargetBlock = C.getCaseSuccessor();
if (SwitchEdges.lookup(TargetBlock) == 1) {
PredicateSwitch *PS = new PredicateSwitch(
Op, SI->getParent(), TargetBlock, C.getCaseValue(), SI);
addInfoFor(OpsToRename, Op, PS);
if (!TargetBlock->getSinglePredecessor())
EdgeUsesOnly.insert({BranchBB, TargetBlock});
}
}
}
// Build predicate info for our function
void PredicateInfoBuilder::buildPredicateInfo() {
DT.updateDFSNumbers();
// Collect operands to rename from all conditional branch terminators, as well
// as assume statements.
SmallVector<Value *, 8> OpsToRename;
for (auto DTN : depth_first(DT.getRootNode())) {
BasicBlock *BranchBB = DTN->getBlock();
if (auto *BI = dyn_cast<BranchInst>(BranchBB->getTerminator())) {
if (!BI->isConditional())
continue;
// Can't insert conditional information if they all go to the same place.
if (BI->getSuccessor(0) == BI->getSuccessor(1))
continue;
processBranch(BI, BranchBB, OpsToRename);
} else if (auto *SI = dyn_cast<SwitchInst>(BranchBB->getTerminator())) {
processSwitch(SI, BranchBB, OpsToRename);
}
}
for (auto &Assume : AC.assumptions()) {
if (auto *II = dyn_cast_or_null<IntrinsicInst>(Assume))
if (DT.isReachableFromEntry(II->getParent()))
processAssume(II, II->getParent(), OpsToRename);
}
// Now rename all our operations.
renameUses(OpsToRename);
}
// Create a ssa_copy declaration with custom mangling, because
// Intrinsic::getDeclaration does not handle overloaded unnamed types properly:
// all unnamed types get mangled to the same string. We use the pointer
// to the type as name here, as it guarantees unique names for different
// types and we remove the declarations when destroying PredicateInfo.
// It is a workaround for PR38117, because solving it in a fully general way is
// tricky (FIXME).
static Function *getCopyDeclaration(Module *M, Type *Ty) {
std::string Name = "llvm.ssa.copy." + utostr((uintptr_t) Ty);
return cast<Function>(
M->getOrInsertFunction(Name,
getType(M->getContext(), Intrinsic::ssa_copy, Ty))
.getCallee());
}
// Given the renaming stack, make all the operands currently on the stack real
// by inserting them into the IR. Return the last operation's value.
Value *PredicateInfoBuilder::materializeStack(unsigned int &Counter,
ValueDFSStack &RenameStack,
Value *OrigOp) {
// Find the first thing we have to materialize
auto RevIter = RenameStack.rbegin();
for (; RevIter != RenameStack.rend(); ++RevIter)
if (RevIter->Def)
break;
size_t Start = RevIter - RenameStack.rbegin();
// The maximum number of things we should be trying to materialize at once
// right now is 4, depending on if we had an assume, a branch, and both used
// and of conditions.
for (auto RenameIter = RenameStack.end() - Start;
RenameIter != RenameStack.end(); ++RenameIter) {
auto *Op =
RenameIter == RenameStack.begin() ? OrigOp : (RenameIter - 1)->Def;
ValueDFS &Result = *RenameIter;
auto *ValInfo = Result.PInfo;
ValInfo->RenamedOp = (RenameStack.end() - Start) == RenameStack.begin()
? OrigOp
: (RenameStack.end() - Start - 1)->Def;
// For edge predicates, we can just place the operand in the block before
// the terminator. For assume, we have to place it right before the assume
// to ensure we dominate all of our uses. Always insert right before the
// relevant instruction (terminator, assume), so that we insert in proper
// order in the case of multiple predicateinfo in the same block.
if (isa<PredicateWithEdge>(ValInfo)) {
IRBuilder<> B(getBranchTerminator(ValInfo));
Function *IF = getCopyDeclaration(F.getParent(), Op->getType());
if (IF->users().empty())
PI.CreatedDeclarations.insert(IF);
CallInst *PIC =
B.CreateCall(IF, Op, Op->getName() + "." + Twine(Counter++));
PI.PredicateMap.insert({PIC, ValInfo});
Result.Def = PIC;
} else {
auto *PAssume = dyn_cast<PredicateAssume>(ValInfo);
assert(PAssume &&
"Should not have gotten here without it being an assume");
// Insert the predicate directly after the assume. While it also holds
// directly before it, assume(i1 true) is not a useful fact.
IRBuilder<> B(PAssume->AssumeInst->getNextNode());
Function *IF = getCopyDeclaration(F.getParent(), Op->getType());
if (IF->users().empty())
PI.CreatedDeclarations.insert(IF);
CallInst *PIC = B.CreateCall(IF, Op);
PI.PredicateMap.insert({PIC, ValInfo});
Result.Def = PIC;
}
}
return RenameStack.back().Def;
}
// Instead of the standard SSA renaming algorithm, which is O(Number of
// instructions), and walks the entire dominator tree, we walk only the defs +
// uses. The standard SSA renaming algorithm does not really rely on the
// dominator tree except to order the stack push/pops of the renaming stacks, so
// that defs end up getting pushed before hitting the correct uses. This does
// not require the dominator tree, only the *order* of the dominator tree. The
// complete and correct ordering of the defs and uses, in dominator tree is
// contained in the DFS numbering of the dominator tree. So we sort the defs and
// uses into the DFS ordering, and then just use the renaming stack as per
// normal, pushing when we hit a def (which is a predicateinfo instruction),
// popping when we are out of the dfs scope for that def, and replacing any uses
// with top of stack if it exists. In order to handle liveness without
// propagating liveness info, we don't actually insert the predicateinfo
// instruction def until we see a use that it would dominate. Once we see such
// a use, we materialize the predicateinfo instruction in the right place and
// use it.
//
// TODO: Use this algorithm to perform fast single-variable renaming in
// promotememtoreg and memoryssa.
void PredicateInfoBuilder::renameUses(SmallVectorImpl<Value *> &OpsToRename) {
ValueDFS_Compare Compare(DT);
// Compute liveness, and rename in O(uses) per Op.
for (auto *Op : OpsToRename) {
LLVM_DEBUG(dbgs() << "Visiting " << *Op << "\n");
unsigned Counter = 0;
SmallVector<ValueDFS, 16> OrderedUses;
const auto &ValueInfo = getValueInfo(Op);
// Insert the possible copies into the def/use list.
// They will become real copies if we find a real use for them, and never
// created otherwise.
for (auto &PossibleCopy : ValueInfo.Infos) {
ValueDFS VD;
// Determine where we are going to place the copy by the copy type.
// The predicate info for branches always come first, they will get
// materialized in the split block at the top of the block.
// The predicate info for assumes will be somewhere in the middle,
// it will get materialized in front of the assume.
if (const auto *PAssume = dyn_cast<PredicateAssume>(PossibleCopy)) {
VD.LocalNum = LN_Middle;
DomTreeNode *DomNode = DT.getNode(PAssume->AssumeInst->getParent());
if (!DomNode)
continue;
VD.DFSIn = DomNode->getDFSNumIn();
VD.DFSOut = DomNode->getDFSNumOut();
VD.PInfo = PossibleCopy;
OrderedUses.push_back(VD);
} else if (isa<PredicateWithEdge>(PossibleCopy)) {
// If we can only do phi uses, we treat it like it's in the branch
// block, and handle it specially. We know that it goes last, and only
// dominate phi uses.
auto BlockEdge = getBlockEdge(PossibleCopy);
if (EdgeUsesOnly.count(BlockEdge)) {
VD.LocalNum = LN_Last;
auto *DomNode = DT.getNode(BlockEdge.first);
if (DomNode) {
VD.DFSIn = DomNode->getDFSNumIn();
VD.DFSOut = DomNode->getDFSNumOut();
VD.PInfo = PossibleCopy;
VD.EdgeOnly = true;
OrderedUses.push_back(VD);
}
} else {
// Otherwise, we are in the split block (even though we perform
// insertion in the branch block).
// Insert a possible copy at the split block and before the branch.
VD.LocalNum = LN_First;
auto *DomNode = DT.getNode(BlockEdge.second);
if (DomNode) {
VD.DFSIn = DomNode->getDFSNumIn();
VD.DFSOut = DomNode->getDFSNumOut();
VD.PInfo = PossibleCopy;
OrderedUses.push_back(VD);
}
}
}
}
convertUsesToDFSOrdered(Op, OrderedUses);
// Here we require a stable sort because we do not bother to try to
// assign an order to the operands the uses represent. Thus, two
// uses in the same instruction do not have a strict sort order
// currently and will be considered equal. We could get rid of the
// stable sort by creating one if we wanted.
llvm::stable_sort(OrderedUses, Compare);
SmallVector<ValueDFS, 8> RenameStack;
// For each use, sorted into dfs order, push values and replaces uses with
// top of stack, which will represent the reaching def.
for (auto &VD : OrderedUses) {
// We currently do not materialize copy over copy, but we should decide if
// we want to.
bool PossibleCopy = VD.PInfo != nullptr;
if (RenameStack.empty()) {
LLVM_DEBUG(dbgs() << "Rename Stack is empty\n");
} else {
LLVM_DEBUG(dbgs() << "Rename Stack Top DFS numbers are ("
<< RenameStack.back().DFSIn << ","
<< RenameStack.back().DFSOut << ")\n");
}
LLVM_DEBUG(dbgs() << "Current DFS numbers are (" << VD.DFSIn << ","
<< VD.DFSOut << ")\n");
bool ShouldPush = (VD.Def || PossibleCopy);
bool OutOfScope = !stackIsInScope(RenameStack, VD);
if (OutOfScope || ShouldPush) {
// Sync to our current scope.
popStackUntilDFSScope(RenameStack, VD);
if (ShouldPush) {
RenameStack.push_back(VD);
}
}
// If we get to this point, and the stack is empty we must have a use
// with no renaming needed, just skip it.
if (RenameStack.empty())
continue;
// Skip values, only want to rename the uses
if (VD.Def || PossibleCopy)
continue;
if (!DebugCounter::shouldExecute(RenameCounter)) {
LLVM_DEBUG(dbgs() << "Skipping execution due to debug counter\n");
continue;
}
ValueDFS &Result = RenameStack.back();
// If the possible copy dominates something, materialize our stack up to
// this point. This ensures every comparison that affects our operation
// ends up with predicateinfo.
if (!Result.Def)
Result.Def = materializeStack(Counter, RenameStack, Op);
LLVM_DEBUG(dbgs() << "Found replacement " << *Result.Def << " for "
<< *VD.U->get() << " in " << *(VD.U->getUser())
<< "\n");
assert(DT.dominates(cast<Instruction>(Result.Def), *VD.U) &&
"Predicateinfo def should have dominated this use");
VD.U->set(Result.Def);
}
}
}
PredicateInfoBuilder::ValueInfo &
PredicateInfoBuilder::getOrCreateValueInfo(Value *Operand) {
auto OIN = ValueInfoNums.find(Operand);
if (OIN == ValueInfoNums.end()) {
// This will grow it
ValueInfos.resize(ValueInfos.size() + 1);
// This will use the new size and give us a 0 based number of the info
auto InsertResult = ValueInfoNums.insert({Operand, ValueInfos.size() - 1});
assert(InsertResult.second && "Value info number already existed?");
return ValueInfos[InsertResult.first->second];
}
return ValueInfos[OIN->second];
}
const PredicateInfoBuilder::ValueInfo &
PredicateInfoBuilder::getValueInfo(Value *Operand) const {
auto OINI = ValueInfoNums.lookup(Operand);
assert(OINI != 0 && "Operand was not really in the Value Info Numbers");
assert(OINI < ValueInfos.size() &&
"Value Info Number greater than size of Value Info Table");
return ValueInfos[OINI];
}
PredicateInfo::PredicateInfo(Function &F, DominatorTree &DT,
AssumptionCache &AC)
: F(F) {
PredicateInfoBuilder Builder(*this, F, DT, AC);
Builder.buildPredicateInfo();
}
// Remove all declarations we created . The PredicateInfo consumers are
// responsible for remove the ssa_copy calls created.
PredicateInfo::~PredicateInfo() {
// Collect function pointers in set first, as SmallSet uses a SmallVector
// internally and we have to remove the asserting value handles first.
SmallPtrSet<Function *, 20> FunctionPtrs;
for (auto &F : CreatedDeclarations)
FunctionPtrs.insert(&*F);
CreatedDeclarations.clear();
for (Function *F : FunctionPtrs) {
assert(F->user_begin() == F->user_end() &&
"PredicateInfo consumer did not remove all SSA copies.");
F->eraseFromParent();
}
}
Optional<PredicateConstraint> PredicateBase::getConstraint() const {
switch (Type) {
case PT_Assume:
case PT_Branch: {
bool TrueEdge = true;
if (auto *PBranch = dyn_cast<PredicateBranch>(this))
TrueEdge = PBranch->TrueEdge;
if (Condition == RenamedOp) {
return {{CmpInst::ICMP_EQ,
TrueEdge ? ConstantInt::getTrue(Condition->getType())
: ConstantInt::getFalse(Condition->getType())}};
}
CmpInst *Cmp = dyn_cast<CmpInst>(Condition);
if (!Cmp) {
// TODO: Make this an assertion once RenamedOp is fully accurate.
return None;
}
CmpInst::Predicate Pred;
Value *OtherOp;
if (Cmp->getOperand(0) == RenamedOp) {
Pred = Cmp->getPredicate();
OtherOp = Cmp->getOperand(1);
} else if (Cmp->getOperand(1) == RenamedOp) {
Pred = Cmp->getSwappedPredicate();
OtherOp = Cmp->getOperand(0);
} else {
// TODO: Make this an assertion once RenamedOp is fully accurate.
return None;
}
// Invert predicate along false edge.
if (!TrueEdge)
Pred = CmpInst::getInversePredicate(Pred);
return {{Pred, OtherOp}};
}
case PT_Switch:
if (Condition != RenamedOp) {
// TODO: Make this an assertion once RenamedOp is fully accurate.
return None;
}
return {{CmpInst::ICMP_EQ, cast<PredicateSwitch>(this)->CaseValue}};
}
llvm_unreachable("Unknown predicate type");
}
void PredicateInfo::verifyPredicateInfo() const {}
char PredicateInfoPrinterLegacyPass::ID = 0;
PredicateInfoPrinterLegacyPass::PredicateInfoPrinterLegacyPass()
: FunctionPass(ID) {
initializePredicateInfoPrinterLegacyPassPass(
*PassRegistry::getPassRegistry());
}
void PredicateInfoPrinterLegacyPass::getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesAll();
AU.addRequiredTransitive<DominatorTreeWrapperPass>();
AU.addRequired<AssumptionCacheTracker>();
}
// Replace ssa_copy calls created by PredicateInfo with their operand.
static void replaceCreatedSSACopys(PredicateInfo &PredInfo, Function &F) {
for (auto I = inst_begin(F), E = inst_end(F); I != E;) {
Instruction *Inst = &*I++;
const auto *PI = PredInfo.getPredicateInfoFor(Inst);
auto *II = dyn_cast<IntrinsicInst>(Inst);
if (!PI || !II || II->getIntrinsicID() != Intrinsic::ssa_copy)
continue;
Inst->replaceAllUsesWith(II->getOperand(0));
Inst->eraseFromParent();
}
}
bool PredicateInfoPrinterLegacyPass::runOnFunction(Function &F) {
auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
auto PredInfo = std::make_unique<PredicateInfo>(F, DT, AC);
PredInfo->print(dbgs());
if (VerifyPredicateInfo)
PredInfo->verifyPredicateInfo();
replaceCreatedSSACopys(*PredInfo, F);
return false;
}
PreservedAnalyses PredicateInfoPrinterPass::run(Function &F,
FunctionAnalysisManager &AM) {
auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
auto &AC = AM.getResult<AssumptionAnalysis>(F);
OS << "PredicateInfo for function: " << F.getName() << "\n";
auto PredInfo = std::make_unique<PredicateInfo>(F, DT, AC);
PredInfo->print(OS);
replaceCreatedSSACopys(*PredInfo, F);
return PreservedAnalyses::all();
}
/// An assembly annotator class to print PredicateInfo information in
/// comments.
class PredicateInfoAnnotatedWriter : public AssemblyAnnotationWriter {
friend class PredicateInfo;
const PredicateInfo *PredInfo;
public:
PredicateInfoAnnotatedWriter(const PredicateInfo *M) : PredInfo(M) {}
void emitBasicBlockStartAnnot(const BasicBlock *BB,
formatted_raw_ostream &OS) override {}
void emitInstructionAnnot(const Instruction *I,
formatted_raw_ostream &OS) override {
if (const auto *PI = PredInfo->getPredicateInfoFor(I)) {
OS << "; Has predicate info\n";
if (const auto *PB = dyn_cast<PredicateBranch>(PI)) {
OS << "; branch predicate info { TrueEdge: " << PB->TrueEdge
<< " Comparison:" << *PB->Condition << " Edge: [";
PB->From->printAsOperand(OS);
OS << ",";
PB->To->printAsOperand(OS);
OS << "]";
} else if (const auto *PS = dyn_cast<PredicateSwitch>(PI)) {
OS << "; switch predicate info { CaseValue: " << *PS->CaseValue
<< " Switch:" << *PS->Switch << " Edge: [";
PS->From->printAsOperand(OS);
OS << ",";
PS->To->printAsOperand(OS);
OS << "]";
} else if (const auto *PA = dyn_cast<PredicateAssume>(PI)) {
OS << "; assume predicate info {"
<< " Comparison:" << *PA->Condition;
}
OS << ", RenamedOp: ";
PI->RenamedOp->printAsOperand(OS, false);
OS << " }\n";
}
}
};
void PredicateInfo::print(raw_ostream &OS) const {
PredicateInfoAnnotatedWriter Writer(this);
F.print(OS, &Writer);
}
void PredicateInfo::dump() const {
PredicateInfoAnnotatedWriter Writer(this);
F.print(dbgs(), &Writer);
}
PreservedAnalyses PredicateInfoVerifierPass::run(Function &F,
FunctionAnalysisManager &AM) {
auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
auto &AC = AM.getResult<AssumptionAnalysis>(F);
std::make_unique<PredicateInfo>(F, DT, AC)->verifyPredicateInfo();
return PreservedAnalyses::all();
}
}
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