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[InstCombine] clean up foldICmpTruncConstant(); NFCI

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1. Fix variable names
2. Add local variables to reduce code


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279132 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjay Patel 2016-08-18 20:25:16 +00:00
parent 175a34b53e
commit f17a9b62af
1 changed files with 17 additions and 14 deletions
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31
lib/Transforms/InstCombine/InstCombineCompares.cpp
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@ -1534,39 +1534,42 @@ Instruction *InstCombiner::foldICmpCstShlConst(ICmpInst &I, Value *Op, Value *A,
return getConstant(false);
}
Instruction *InstCombiner::foldICmpTruncConstant(ICmpInst &ICI,
Instruction *LHSI,
const APInt *RHSV) {
/// Fold icmp (trunc X, Y), C.
Instruction *InstCombiner::foldICmpTruncConstant(ICmpInst &Cmp,
Instruction *Trunc,
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;
if (RHS->isOne() && RHSV->getBitWidth() > 1) {
ICmpInst::Predicate Pred = Cmp.getPredicate();
Value *X = Trunc->getOperand(0);
if (RHS->isOne() && C->getBitWidth() > 1) {
// icmp slt trunc(signum(V)) 1 --> icmp slt V, 1
Value *V = nullptr;
if (ICI.getPredicate() == ICmpInst::ICMP_SLT &&
match(LHSI->getOperand(0), m_Signum(m_Value(V))))
if (Pred == ICmpInst::ICMP_SLT && match(X, m_Signum(m_Value(V))))
return new ICmpInst(ICmpInst::ICMP_SLT, V,
ConstantInt::get(V->getType(), 1));
}
if (ICI.isEquality() && LHSI->hasOneUse()) {
if (Cmp.isEquality() && Trunc->hasOneUse()) {
// Simplify icmp eq (trunc x to i8), 42 -> icmp eq x, 42|highbits if all
// of the high bits truncated out of x are known.
unsigned DstBits = LHSI->getType()->getPrimitiveSizeInBits(),
SrcBits = LHSI->getOperand(0)->getType()->getPrimitiveSizeInBits();
unsigned DstBits = Trunc->getType()->getPrimitiveSizeInBits(),
SrcBits = X->getType()->getPrimitiveSizeInBits();
APInt KnownZero(SrcBits, 0), KnownOne(SrcBits, 0);
computeKnownBits(LHSI->getOperand(0), KnownZero, KnownOne, 0, &ICI);
computeKnownBits(X, KnownZero, KnownOne, 0, &Cmp);
// If all the high bits are known, we can do this xform.
if ((KnownZero | KnownOne).countLeadingOnes() >= SrcBits - DstBits) {
// Pull in the high bits from known-ones set.
APInt NewRHS = RHS->getValue().zext(SrcBits);
APInt NewRHS = C->zext(SrcBits);
NewRHS |= KnownOne & APInt::getHighBitsSet(SrcBits, SrcBits - DstBits);
return new ICmpInst(ICI.getPredicate(), LHSI->getOperand(0),
Builder->getInt(NewRHS));
return new ICmpInst(Pred, X, Builder->getInt(NewRHS));
}
}
return nullptr;
}