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ConstantFold: Shifting undef by zero results in undef

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224553 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer
2014-12-18 23:54:43 +00:00
parent a9dd3713d0
commit 73059bd1f1
2 changed files with 30 additions and 0 deletions
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9
lib/IR/ConstantFold.cpp
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@ -956,12 +956,18 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
// X >>l undef -> undef
if (isa<UndefValue>(C2))
return C2;
// undef >>l 0 -> undef
if (match(C2, m_Zero()))
return C1;
// undef >>l X -> 0
return Constant::getNullValue(C1->getType());
case Instruction::AShr:
// X >>a undef -> undef
if (isa<UndefValue>(C2))
return C2;
// undef >>a 0 -> undef
if (match(C2, m_Zero()))
return C1;
// TODO: undef >>a X -> undef if the shift is exact
// undef >>a X -> 0
return Constant::getNullValue(C1->getType());
@ -969,6 +975,9 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode,
// X << undef -> undef
if (isa<UndefValue>(C2))
return C2;
// undef << 0 -> undef
if (match(C2, m_Zero()))
return C1;
// undef << X -> 0
return Constant::getNullValue(C1->getType());
}