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[InstCombine] use local variables to reduce code in foldICmpShlConstant; NFC 

llvm-svn: 279282
This commit is contained in:
Sanjay Patel 2016-08-19 17:34:05 +00:00
parent 5a7bef9c14
commit e38e79c3e6
1 changed files with 15 additions and 21 deletions
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36
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
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@ -2006,13 +2006,15 @@ Instruction *InstCombiner::foldICmpShlConstant(ICmpInst &Cmp, Instruction *Shl,
if (ShAmt->uge(TypeBits))
return nullptr;
ICmpInst::Predicate Pred = Cmp.getPredicate();
Value *X = Shl->getOperand(0);
if (Cmp.isEquality()) {
// If we are comparing against bits always shifted out, the comparison
// cannot succeed.
Constant *Comp =
ConstantExpr::getShl(ConstantExpr::getLShr(RHS, ShAmt), ShAmt);
if (Comp != RHS) { // Comparing against a bit that we know is zero.
bool IsICMP_NE = Cmp.getPredicate() == ICmpInst::ICMP_NE;
bool IsICMP_NE = Pred == ICmpInst::ICMP_NE;
Constant *Cst = Builder->getInt1(IsICMP_NE);
return replaceInstUsesWith(Cmp, Cst);
}
@ -2020,14 +2022,12 @@ Instruction *InstCombiner::foldICmpShlConstant(ICmpInst &Cmp, Instruction *Shl,
// If the shift is NUW, then it is just shifting out zeros, no need for an
// AND.
if (cast<BinaryOperator>(Shl)->hasNoUnsignedWrap())
return new ICmpInst(Cmp.getPredicate(), Shl->getOperand(0),
ConstantExpr::getLShr(RHS, ShAmt));
return new ICmpInst(Pred, X, ConstantExpr::getLShr(RHS, ShAmt));
// If the shift is NSW and we compare to 0, then it is just shifting out
// sign bits, no need for an AND either.
if (cast<BinaryOperator>(Shl)->hasNoSignedWrap() && *C == 0)
return new ICmpInst(Cmp.getPredicate(), Shl->getOperand(0),
ConstantExpr::getLShr(RHS, ShAmt));
return new ICmpInst(Pred, X, ConstantExpr::getLShr(RHS, ShAmt));
if (Shl->hasOneUse()) {
// Otherwise strength reduce the shift into an and.
@ -2035,30 +2035,25 @@ Instruction *InstCombiner::foldICmpShlConstant(ICmpInst &Cmp, Instruction *Shl,
Constant *Mask =
Builder->getInt(APInt::getLowBitsSet(TypeBits, TypeBits - ShAmtVal));
Value *And = Builder->CreateAnd(Shl->getOperand(0), Mask,
Shl->getName() + ".mask");
return new ICmpInst(Cmp.getPredicate(), And,
ConstantExpr::getLShr(RHS, ShAmt));
Value *And = Builder->CreateAnd(X, Mask, Shl->getName() + ".mask");
return new ICmpInst(Pred, And, ConstantExpr::getLShr(RHS, ShAmt));
}
}
// If this is a signed comparison to 0 and the shift is sign preserving,
// use the shift LHS operand instead.
ICmpInst::Predicate Pred = Cmp.getPredicate();
if (isSignTest(Pred, *C) && cast<BinaryOperator>(Shl)->hasNoSignedWrap())
return new ICmpInst(Pred, Shl->getOperand(0),
Constant::getNullValue(RHS->getType()));
// use the shift LHS operand instead; isSignTest may change 'Pred', so only
// do that if we're sure to not continue on in this function.
if (cast<BinaryOperator>(Shl)->hasNoSignedWrap() && isSignTest(Pred, *C))
return new ICmpInst(Pred, X, Constant::getNullValue(RHS->getType()));
// Otherwise, if this is a comparison of the sign bit, simplify to and/test.
bool TrueIfSigned = false;
if (Shl->hasOneUse() &&
isSignBitCheck(Cmp.getPredicate(), RHS, TrueIfSigned)) {
if (Shl->hasOneUse() && isSignBitCheck(Pred, RHS, TrueIfSigned)) {
// (X << 31) <s 0 --> (X&1) != 0
Constant *Mask = ConstantInt::get(
Shl->getOperand(0)->getType(),
X->getType(),
APInt::getOneBitSet(TypeBits, TypeBits - ShAmt->getZExtValue() - 1));
Value *And = Builder->CreateAnd(Shl->getOperand(0), Mask,
Shl->getName() + ".mask");
Value *And = Builder->CreateAnd(X, Mask, Shl->getName() + ".mask");
return new ICmpInst(TrueIfSigned ? ICmpInst::ICMP_NE : ICmpInst::ICMP_EQ,
And, Constant::getNullValue(And->getType()));
}
@ -2074,8 +2069,7 @@ Instruction *InstCombiner::foldICmpShlConstant(ICmpInst &Cmp, Instruction *Shl,
Type *NTy = IntegerType::get(Cmp.getContext(), TypeBits - Amt);
Constant *NCI = ConstantExpr::getTrunc(
ConstantExpr::getAShr(RHS, ConstantInt::get(RHS->getType(), Amt)), NTy);
return new ICmpInst(Cmp.getPredicate(),
Builder->CreateTrunc(Shl->getOperand(0), NTy), NCI);
return new ICmpInst(Pred, Builder->CreateTrunc(X, NTy), NCI);
}
return nullptr;