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Fix PR1253 and xor2.ll:test[01]

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35612 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2007-04-03 01:47:41 +00:00
parent 08a3fbe42e
commit 44ad43033e
1 changed files with 30 additions and 1 deletions
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31
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -4714,7 +4714,36 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
// instruction can be folded into the icmp
if (Instruction *LHSI = dyn_cast<Instruction>(Op0))
switch (LHSI->getOpcode()) {
case Instruction::And:
case Instruction::Xor: // (icmp pred (and X, XorCST), CI)
if (ConstantInt *XorCST = dyn_cast<ConstantInt>(LHSI->getOperand(1))) {
// If this is a comparison that tests the signbit (X < 0) or (x > -1),
// fold the xor.
if (I.getPredicate() == ICmpInst::ICMP_SLT && CI->isZero() ||
I.getPredicate() == ICmpInst::ICMP_SGT && CI->isAllOnesValue()) {
Value *CompareVal = LHSI->getOperand(0);
// If the sign bit of the XorCST is not set, there is no change to
// the operation, just stop using the Xor.
if (!XorCST->getValue().isNegative()) {
I.setOperand(0, CompareVal);
AddToWorkList(LHSI);
return &I;
}
// Was the old condition true if the operand is positive?
bool isTrueIfPositive = I.getPredicate() == ICmpInst::ICMP_SGT;
// If so, the new one isn't.
isTrueIfPositive ^= true;
if (isTrueIfPositive)
return new ICmpInst(ICmpInst::ICMP_SGT, CompareVal, SubOne(CI));
else
return new ICmpInst(ICmpInst::ICMP_SLT, CompareVal, AddOne(CI));
}
}
break;
case Instruction::And: // (icmp pred (and X, AndCST), CI)
if (LHSI->hasOneUse() && isa<ConstantInt>(LHSI->getOperand(1)) &&
LHSI->getOperand(0)->hasOneUse()) {
ConstantInt *AndCST = cast<ConstantInt>(LHSI->getOperand(1));