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Fix demanded bits analysis with srem by negative number. Based on a patch
by Richard Osborne. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@58555 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -1274,12 +1274,12 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, APInt DemandedMask,
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break;
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break;
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case Instruction::SRem:
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case Instruction::SRem:
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if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) {
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if (ConstantInt *Rem = dyn_cast<ConstantInt>(I->getOperand(1))) {
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APInt RA = Rem->getValue();
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APInt RA = Rem->getValue().abs();
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if (RA.isPowerOf2() || (-RA).isPowerOf2()) {
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if (RA.isPowerOf2()) {
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if (DemandedMask.ule(RA)) // srem won't affect demanded bits
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if (DemandedMask.ule(RA)) // srem won't affect demanded bits
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return UpdateValueUsesWith(I, I->getOperand(0));
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return UpdateValueUsesWith(I, I->getOperand(0));
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APInt LowBits = RA.isStrictlyPositive() ? (RA - 1) : ~RA;
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APInt LowBits = RA - 1;
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APInt Mask2 = LowBits | APInt::getSignBit(BitWidth);
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APInt Mask2 = LowBits | APInt::getSignBit(BitWidth);
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if (SimplifyDemandedBits(I->getOperand(0), Mask2,
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if (SimplifyDemandedBits(I->getOperand(0), Mask2,
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LHSKnownZero, LHSKnownOne, Depth+1))
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LHSKnownZero, LHSKnownOne, Depth+1))
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@ -0,0 +1,8 @@
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; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {ret i1 true}
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; PR2993
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define i1 @foo(i32 %x) {
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%1 = srem i32 %x, -1
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%2 = icmp eq i32 %1, 0
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ret i1 %2
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}
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