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Thread comparisons over udiv/sdiv/ashr/lshr exact and lshr nuw/nsw whenever

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possible. This goes into instcombine and instsimplify because instsimplify
doesn't need to check hasOneUse since it returns (almost exclusively) constants.

This fixes PR9343 #4 #5 and #8!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127064 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky
2011-03-05 05:19:11 +00:00
parent 9feda1730c
commit 58bfcdbcf6
4 changed files with 109 additions and 1 deletions
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lib/Transforms/InstCombine/InstCombineCompares.cpp
+21
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@@ -2393,6 +2393,27 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
}
}
break;
case Instruction::UDiv:
case Instruction::LShr:
if (I.isSigned())
break;
// fall-through
case Instruction::SDiv:
case Instruction::AShr:
if (!BO0->isExact() && !BO1->isExact())
break;
return new ICmpInst(I.getPredicate(), BO0->getOperand(0),
BO1->getOperand(0));
case Instruction::Shl: {
bool NUW = BO0->hasNoUnsignedWrap() && BO1->hasNoUnsignedWrap();
bool NSW = BO0->hasNoSignedWrap() && BO1->hasNoSignedWrap();
if (!NUW && !NSW)
break;
if (!NSW && I.isSigned())
break;
return new ICmpInst(I.getPredicate(), BO0->getOperand(0),
BO1->getOperand(0));
}
}
}
}