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If we detect that the instruction we are simplifying is unreachable, arrange for

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it to be replaced by undef rather than not replaced at all, the idea being that
this may reduce the amount of work done by whoever called InstructionSimplify.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121860 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands 2010-12-15 11:02:22 +00:00
parent 26e097ca4b
commit f8b1a5ea96
1 changed files with 3 additions and 3 deletions
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6
lib/Analysis/InstructionSimplify.cpp
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@ -441,7 +441,7 @@ static Value *SimplifyXorInst(Value *Op0, Value *Op1, const TargetData *TD,
// A ^ undef -> undef
if (isa<UndefValue>(Op1))
return UndefValue::get(Op0->getType());
return Op1;
// A ^ 0 = A
if (match(Op1, m_Zero()))
@ -868,8 +868,8 @@ Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD,
/// If called on unreachable code, the above logic may report that the
/// instruction simplified to itself. Make life easier for users by
/// detecting that case here, returning null if it occurs.
return Result == I ? 0 : Result;
/// detecting that case here, returning a safe value instead.
return Result == I ? UndefValue::get(I->getType()) : Result;
}
/// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then