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//===- LowerConstantIntrinsics.cpp - Lower constant intrinsic calls -------===//
//
// 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 pass lowers all remaining 'objectsize' 'is.constant' intrinsic calls
// and provides constant propagation and basic CFG cleanup on the result.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar/LowerConstantIntrinsics.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/DomTreeUpdater.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;
using namespace llvm::PatternMatch;
#define DEBUG_TYPE "lower-is-constant-intrinsic"
STATISTIC(IsConstantIntrinsicsHandled,
"Number of 'is.constant' intrinsic calls handled");
STATISTIC(ObjectSizeIntrinsicsHandled,
"Number of 'objectsize' intrinsic calls handled");
static Value *lowerIsConstantIntrinsic(IntrinsicInst *II) {
if (auto *C = dyn_cast<Constant>(II->getOperand(0)))
if (C->isManifestConstant())
return ConstantInt::getTrue(II->getType());
return ConstantInt::getFalse(II->getType());
}
static bool replaceConditionalBranchesOnConstant(Instruction *II,
Value *NewValue,
DomTreeUpdater *DTU) {
bool HasDeadBlocks = false;
SmallSetVector<Instruction *, 8> UnsimplifiedUsers;
replaceAndRecursivelySimplify(II, NewValue, nullptr, nullptr, nullptr,
&UnsimplifiedUsers);
// UnsimplifiedUsers can contain PHI nodes that may be removed when
// replacing the branch instructions, so use a value handle worklist
// to handle those possibly removed instructions.
SmallVector<WeakVH, 8> Worklist(UnsimplifiedUsers.begin(),
UnsimplifiedUsers.end());
for (auto &VH : Worklist) {
BranchInst *BI = dyn_cast_or_null<BranchInst>(VH);
if (!BI)
continue;
if (BI->isUnconditional())
continue;
BasicBlock *Target, *Other;
if (match(BI->getOperand(0), m_Zero())) {
Target = BI->getSuccessor(1);
Other = BI->getSuccessor(0);
} else if (match(BI->getOperand(0), m_One())) {
Target = BI->getSuccessor(0);
Other = BI->getSuccessor(1);
} else {
Target = nullptr;
Other = nullptr;
}
if (Target && Target != Other) {
BasicBlock *Source = BI->getParent();
Other->removePredecessor(Source);
BI->eraseFromParent();
BranchInst::Create(Target, Source);
if (DTU)
DTU->applyUpdates({{DominatorTree::Delete, Source, Other}});
if (pred_empty(Other))
HasDeadBlocks = true;
}
}
return HasDeadBlocks;
}
static bool lowerConstantIntrinsics(Function &F, const TargetLibraryInfo *TLI,
DominatorTree *DT) {
Optional<DomTreeUpdater> DTU;
if (DT)
DTU.emplace(DT, DomTreeUpdater::UpdateStrategy::Lazy);
bool HasDeadBlocks = false;
const auto &DL = F.getParent()->getDataLayout();
SmallVector<WeakTrackingVH, 8> Worklist;
ReversePostOrderTraversal<Function *> RPOT(&F);
for (BasicBlock *BB : RPOT) {
for (Instruction &I: *BB) {
IntrinsicInst *II = dyn_cast<IntrinsicInst>(&I);
if (!II)
continue;
switch (II->getIntrinsicID()) {
default:
break;
case Intrinsic::is_constant:
case Intrinsic::objectsize:
Worklist.push_back(WeakTrackingVH(&I));
break;
}
}
}
for (WeakTrackingVH &VH: Worklist) {
// Items on the worklist can be mutated by earlier recursive replaces.
// This can remove the intrinsic as dead (VH == null), but also replace
// the intrinsic in place.
if (!VH)
continue;
IntrinsicInst *II = dyn_cast<IntrinsicInst>(&*VH);
if (!II)
continue;
Value *NewValue;
switch (II->getIntrinsicID()) {
default:
continue;
case Intrinsic::is_constant:
NewValue = lowerIsConstantIntrinsic(II);
IsConstantIntrinsicsHandled++;
break;
case Intrinsic::objectsize:
NewValue = lowerObjectSizeCall(II, DL, TLI, true);
ObjectSizeIntrinsicsHandled++;
break;
}
HasDeadBlocks |= replaceConditionalBranchesOnConstant(
II, NewValue, DTU.hasValue() ? DTU.getPointer() : nullptr);
}
if (HasDeadBlocks)
removeUnreachableBlocks(F, DTU.hasValue() ? DTU.getPointer() : nullptr);
return !Worklist.empty();
}
PreservedAnalyses
LowerConstantIntrinsicsPass::run(Function &F, FunctionAnalysisManager &AM) {
if (lowerConstantIntrinsics(F, AM.getCachedResult<TargetLibraryAnalysis>(F),
AM.getCachedResult<DominatorTreeAnalysis>(F))) {
PreservedAnalyses PA;
PA.preserve<DominatorTreeAnalysis>();
return PA;
}
return PreservedAnalyses::all();
}
namespace {
/// Legacy pass for lowering is.constant intrinsics out of the IR.
///
/// When this pass is run over a function it converts is.constant intrinsics
/// into 'true' or 'false'. This complements the normal constant folding
/// to 'true' as part of Instruction Simplify passes.
class LowerConstantIntrinsics : public FunctionPass {
public:
static char ID;
LowerConstantIntrinsics() : FunctionPass(ID) {
initializeLowerConstantIntrinsicsPass(*PassRegistry::getPassRegistry());
}
bool runOnFunction(Function &F) override {
auto *TLIP = getAnalysisIfAvailable<TargetLibraryInfoWrapperPass>();
const TargetLibraryInfo *TLI = TLIP ? &TLIP->getTLI(F) : nullptr;
DominatorTree *DT = nullptr;
if (auto *DTWP = getAnalysisIfAvailable<DominatorTreeWrapperPass>())
DT = &DTWP->getDomTree();
return lowerConstantIntrinsics(F, TLI, DT);
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addPreserved<GlobalsAAWrapperPass>();
AU.addPreserved<DominatorTreeWrapperPass>();
}
};
} // namespace
char LowerConstantIntrinsics::ID = 0;
INITIALIZE_PASS_BEGIN(LowerConstantIntrinsics, "lower-constant-intrinsics",
"Lower constant intrinsics", false, false)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_END(LowerConstantIntrinsics, "lower-constant-intrinsics",
"Lower constant intrinsics", false, false)
FunctionPass *llvm::createLowerConstantIntrinsicsPass() {
return new LowerConstantIntrinsics();
}
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