diff options
Diffstat (limited to 'lib/VMCore/ConstantFold.cpp')
| -rw-r--r-- | lib/VMCore/ConstantFold.cpp | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/lib/VMCore/ConstantFold.cpp b/lib/VMCore/ConstantFold.cpp index 762a24a263..7b21817cda 100644 --- a/lib/VMCore/ConstantFold.cpp +++ b/lib/VMCore/ConstantFold.cpp @@ -474,9 +474,14 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, // Handle UndefValue up front if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { switch (Opcode) { + case Instruction::Xor: + if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) + // Handle undef ^ undef -> 0 special case. This is a common + // idiom (misuse). + return Constant::getNullValue(C1->getType()); + // Fallthrough case Instruction::Add: case Instruction::Sub: - case Instruction::Xor: return UndefValue::get(C1->getType()); case Instruction::Mul: case Instruction::And: |