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[SimplifyIndVar] Refactor overflow check elimination code; NFC

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Extract a willNotOverflow() helper function that is shared between
eliminateOverflowIntrinsic() and strengthenOverflowingOperation().
Use WithOverflowInst for the former.

We'll be able to reuse the same code for saturating intrinsics as
well.

llvm-svn: 362305
This commit is contained in:
Nikita Popov 2019-06-01 20:21:53 +00:00
parent 7cebf0af40
commit 900578d1c1
1 changed files with 43 additions and 97 deletions
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140
llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
View File

@ -22,6 +22,7 @@
#include "llvm/IR/Dominators.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/PatternMatch.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
@ -79,7 +80,7 @@ namespace {
bool eliminateIdentitySCEV(Instruction *UseInst, Instruction *IVOperand);
bool replaceIVUserWithLoopInvariant(Instruction *UseInst);
bool eliminateOverflowIntrinsic(CallInst *CI);
bool eliminateOverflowIntrinsic(WithOverflowInst *WO);
bool eliminateTrunc(TruncInst *TI);
bool eliminateIVUser(Instruction *UseInst, Instruction *IVOperand);
bool makeIVComparisonInvariant(ICmpInst *ICmp, Value *IVOperand);
@ -400,61 +401,29 @@ void SimplifyIndvar::simplifyIVRemainder(BinaryOperator *Rem, Value *IVOperand,
replaceSRemWithURem(Rem);
}
bool SimplifyIndvar::eliminateOverflowIntrinsic(CallInst *CI) {
auto *F = CI->getCalledFunction();
if (!F)
return false;
typedef const SCEV *(ScalarEvolution::*OperationFunctionTy)(
const SCEV *, const SCEV *, SCEV::NoWrapFlags, unsigned);
typedef const SCEV *(ScalarEvolution::*ExtensionFunctionTy)(
const SCEV *, Type *, unsigned);
OperationFunctionTy Operation;
ExtensionFunctionTy Extension;
Instruction::BinaryOps RawOp;
// We always have exactly one of nsw or nuw. If NoSignedOverflow is false, we
// have nuw.
bool NoSignedOverflow;
switch (F->getIntrinsicID()) {
static bool willNotOverflow(ScalarEvolution *SE, Instruction::BinaryOps BinOp,
bool Signed, const SCEV *LHS, const SCEV *RHS) {
const SCEV *(ScalarEvolution::*Operation)(const SCEV *, const SCEV *,
SCEV::NoWrapFlags, unsigned);
switch (BinOp) {
default:
return false;
case Intrinsic::sadd_with_overflow:
llvm_unreachable("Unsupported binary op");
case Instruction::Add:
Operation = &ScalarEvolution::getAddExpr;
Extension = &ScalarEvolution::getSignExtendExpr;
RawOp = Instruction::Add;
NoSignedOverflow = true;
break;
case Intrinsic::uadd_with_overflow:
Operation = &ScalarEvolution::getAddExpr;
Extension = &ScalarEvolution::getZeroExtendExpr;
RawOp = Instruction::Add;
NoSignedOverflow = false;
break;
case Intrinsic::ssub_with_overflow:
case Instruction::Sub:
Operation = &ScalarEvolution::getMinusSCEV;
Extension = &ScalarEvolution::getSignExtendExpr;
RawOp = Instruction::Sub;
NoSignedOverflow = true;
break;
case Intrinsic::usub_with_overflow:
Operation = &ScalarEvolution::getMinusSCEV;
Extension = &ScalarEvolution::getZeroExtendExpr;
RawOp = Instruction::Sub;
NoSignedOverflow = false;
case Instruction::Mul:
Operation = &ScalarEvolution::getMulExpr;
break;
}
const SCEV *LHS = SE->getSCEV(CI->getArgOperand(0));
const SCEV *RHS = SE->getSCEV(CI->getArgOperand(1));
const SCEV *(ScalarEvolution::*Extension)(const SCEV *, Type *, unsigned) =
Signed ? &ScalarEvolution::getSignExtendExpr
: &ScalarEvolution::getZeroExtendExpr;
// Check ext(LHS op RHS) == ext(LHS) op ext(RHS)
auto *NarrowTy = cast<IntegerType>(LHS->getType());
auto *WideTy =
IntegerType::get(NarrowTy->getContext(), NarrowTy->getBitWidth() * 2);
@ -465,27 +434,32 @@ bool SimplifyIndvar::eliminateOverflowIntrinsic(CallInst *CI) {
const SCEV *B =
(SE->*Operation)((SE->*Extension)(LHS, WideTy, 0),
(SE->*Extension)(RHS, WideTy, 0), SCEV::FlagAnyWrap, 0);
return A == B;
}
if (A != B)
bool SimplifyIndvar::eliminateOverflowIntrinsic(WithOverflowInst *WO) {
const SCEV *LHS = SE->getSCEV(WO->getLHS());
const SCEV *RHS = SE->getSCEV(WO->getRHS());
if (!willNotOverflow(SE, WO->getBinaryOp(), WO->isSigned(), LHS, RHS))
return false;
// Proved no overflow, nuke the overflow check and, if possible, the overflow
// intrinsic as well.
BinaryOperator *NewResult = BinaryOperator::Create(
RawOp, CI->getArgOperand(0), CI->getArgOperand(1), "", CI);
WO->getBinaryOp(), WO->getLHS(), WO->getRHS(), "", WO);
if (NoSignedOverflow)
if (WO->isSigned())
NewResult->setHasNoSignedWrap(true);
else
NewResult->setHasNoUnsignedWrap(true);
SmallVector<ExtractValueInst *, 4> ToDelete;
for (auto *U : CI->users()) {
for (auto *U : WO->users()) {
if (auto *EVI = dyn_cast<ExtractValueInst>(U)) {
if (EVI->getIndices()[0] == 1)
EVI->replaceAllUsesWith(ConstantInt::getFalse(CI->getContext()));
EVI->replaceAllUsesWith(ConstantInt::getFalse(WO->getContext()));
else {
assert(EVI->getIndices()[0] == 0 && "Only two possibilities!");
EVI->replaceAllUsesWith(NewResult);
@ -497,8 +471,8 @@ bool SimplifyIndvar::eliminateOverflowIntrinsic(CallInst *CI) {
for (auto *EVI : ToDelete)
EVI->eraseFromParent();
if (CI->use_empty())
CI->eraseFromParent();
if (WO->use_empty())
WO->eraseFromParent();
return true;
}
@ -635,8 +609,8 @@ bool SimplifyIndvar::eliminateIVUser(Instruction *UseInst,
return eliminateSDiv(Bin);
}
if (auto *CI = dyn_cast<CallInst>(UseInst))
if (eliminateOverflowIntrinsic(CI))
if (auto *WO = dyn_cast<WithOverflowInst>(UseInst))
if (eliminateOverflowIntrinsic(WO))
return true;
if (auto *TI = dyn_cast<TruncInst>(UseInst))
@ -729,59 +703,31 @@ bool SimplifyIndvar::eliminateIdentitySCEV(Instruction *UseInst,
/// unsigned-overflow. Returns true if anything changed, false otherwise.
bool SimplifyIndvar::strengthenOverflowingOperation(BinaryOperator *BO,
Value *IVOperand) {
// Fastpath: we don't have any work to do if `BO` is `nuw` and `nsw`.
if (BO->hasNoUnsignedWrap() && BO->hasNoSignedWrap())
return false;
const SCEV *(ScalarEvolution::*GetExprForBO)(const SCEV *, const SCEV *,
SCEV::NoWrapFlags, unsigned);
switch (BO->getOpcode()) {
default:
if (BO->getOpcode() != Instruction::Add &&
BO->getOpcode() != Instruction::Sub &&
BO->getOpcode() != Instruction::Mul)
return false;
case Instruction::Add:
GetExprForBO = &ScalarEvolution::getAddExpr;
break;
case Instruction::Sub:
GetExprForBO = &ScalarEvolution::getMinusSCEV;
break;
case Instruction::Mul:
GetExprForBO = &ScalarEvolution::getMulExpr;
break;
}
unsigned BitWidth = cast<IntegerType>(BO->getType())->getBitWidth();
Type *WideTy = IntegerType::get(BO->getContext(), BitWidth * 2);
const SCEV *LHS = SE->getSCEV(BO->getOperand(0));
const SCEV *RHS = SE->getSCEV(BO->getOperand(1));
bool Changed = false;
if (!BO->hasNoUnsignedWrap()) {
const SCEV *ExtendAfterOp = SE->getZeroExtendExpr(SE->getSCEV(BO), WideTy);
const SCEV *OpAfterExtend = (SE->*GetExprForBO)(
SE->getZeroExtendExpr(LHS, WideTy), SE->getZeroExtendExpr(RHS, WideTy),
SCEV::FlagAnyWrap, 0u);
if (ExtendAfterOp == OpAfterExtend) {
BO->setHasNoUnsignedWrap();
SE->forgetValue(BO);
Changed = true;
}
if (!BO->hasNoUnsignedWrap() &&
willNotOverflow(SE, BO->getOpcode(), /* Signed */ false, LHS, RHS)) {
BO->setHasNoUnsignedWrap();
SE->forgetValue(BO);
Changed = true;
}
if (!BO->hasNoSignedWrap()) {
const SCEV *ExtendAfterOp = SE->getSignExtendExpr(SE->getSCEV(BO), WideTy);
const SCEV *OpAfterExtend = (SE->*GetExprForBO)(
SE->getSignExtendExpr(LHS, WideTy), SE->getSignExtendExpr(RHS, WideTy),
SCEV::FlagAnyWrap, 0u);
if (ExtendAfterOp == OpAfterExtend) {
BO->setHasNoSignedWrap();
SE->forgetValue(BO);
Changed = true;
}
if (!BO->hasNoSignedWrap() &&
willNotOverflow(SE, BO->getOpcode(), /* Signed */ true, LHS, RHS)) {
BO->setHasNoSignedWrap();
SE->forgetValue(BO);
Changed = true;
}
return Changed;