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[InstCombine] fix variable names to match formula comments; NFC 

llvm-svn: 278855
This commit is contained in:
Sanjay Patel 2016-08-16 21:26:10 +00:00
parent 110522bc0f
commit b9aa67bfcf
1 changed files with 17 additions and 17 deletions
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34
llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
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@ -2167,35 +2167,35 @@ Instruction *InstCombiner::foldICmpDivConstant(ICmpInst &ICI, Instruction *LHSI,
return nullptr;
}
Instruction *InstCombiner::foldICmpSubConstant(ICmpInst &ICI, Instruction *LHSI,
const APInt *RHSV) {
/// Fold icmp (sub X, Y), C.
Instruction *InstCombiner::foldICmpSubConstant(ICmpInst &Cmp, Instruction *Sub,
const APInt *C) {
// FIXME: This check restricts all folds under here to scalar types.
ConstantInt *RHS = dyn_cast<ConstantInt>(ICI.getOperand(1));
ConstantInt *RHS = dyn_cast<ConstantInt>(Cmp.getOperand(1));
if (!RHS)
return nullptr;
ConstantInt *LHSC = dyn_cast<ConstantInt>(LHSI->getOperand(0));
if (!LHSC)
ConstantInt *SubC = dyn_cast<ConstantInt>(Sub->getOperand(0));
if (!SubC)
return nullptr;
const APInt &LHSV = LHSC->getValue();
const APInt &C2 = SubC->getValue();
// C1-X <u C2 -> (X|(C2-1)) == C1
// iff C1 & (C2-1) == C2-1
// C-X <u C2 -> (X|(C2-1)) == C
// iff C & (C2-1) == C2-1
// C2 is a power of 2
if (ICI.getPredicate() == ICmpInst::ICMP_ULT && LHSI->hasOneUse() &&
RHSV->isPowerOf2() && (LHSV & (*RHSV - 1)) == (*RHSV - 1))
if (Cmp.getPredicate() == ICmpInst::ICMP_ULT && Sub->hasOneUse() &&
C->isPowerOf2() && (C2 & (*C - 1)) == (*C - 1))
return new ICmpInst(ICmpInst::ICMP_EQ,
Builder->CreateOr(LHSI->getOperand(1), *RHSV - 1),
LHSC);
Builder->CreateOr(Sub->getOperand(1), *C - 1), SubC);
// C1-X >u C2 -> (X|C2) != C1
// iff C1 & C2 == C2
// C-X >u C2 -> (X|C2) != C
// iff C & C2 == C2
// C2+1 is a power of 2
if (ICI.getPredicate() == ICmpInst::ICMP_UGT && LHSI->hasOneUse() &&
(*RHSV + 1).isPowerOf2() && (LHSV & *RHSV) == *RHSV)
if (Cmp.getPredicate() == ICmpInst::ICMP_UGT && Sub->hasOneUse() &&
(*C + 1).isPowerOf2() && (C2 & *C) == *C)
return new ICmpInst(ICmpInst::ICMP_NE,
Builder->CreateOr(LHSI->getOperand(1), *RHSV), LHSC);
Builder->CreateOr(Sub->getOperand(1), *C), SubC);
return nullptr;
}