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Constant fold x == undef to undef.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107074 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2010-06-28 21:30:07 +00:00
parent e89c5e57cc
commit 0dd3549edc
2 changed files with 31 additions and 1 deletions
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9
lib/VMCore/ConstantFold.cpp
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@@ -1817,8 +1817,15 @@ Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred,
return Constant::getAllOnesValue(ResultTy);
// Handle some degenerate cases first
if (isa<UndefValue>(C1) || isa<UndefValue>(C2))
if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) {
// For EQ and NE, we can always pick a value for the undef to make the
// predicate pass or fail, so we can return undef.
if (ICmpInst::isEquality(ICmpInst::Predicate(pred)))
return UndefValue::get(ResultTy);
// Otherwise, pick the same value as the non-undef operand, and fold
// it to true or false.
return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(pred));
}
// No compile-time operations on this type yet.
if (C1->getType()->isPPC_FP128Ty())