diff options
| author | Evan Cheng <evan.cheng@apple.com> | 2008-03-25 20:08:07 +0000 |
|---|---|---|
| committer | Evan Cheng <evan.cheng@apple.com> | 2008-03-25 20:08:07 +0000 |
| commit | 26471c48b3d49bdbcfcc05cb9a575b5fa123fbbf (patch) | |
| tree | cf75442b4cf9f93ed3b27eef5bd8a601353c94b9 /lib/VMCore/ConstantFold.cpp | |
| parent | d34af7875b682d519038295b04ab4e15f237ccdf (diff) | |
| download | external_llvm-26471c48b3d49bdbcfcc05cb9a575b5fa123fbbf.zip external_llvm-26471c48b3d49bdbcfcc05cb9a575b5fa123fbbf.tar.gz external_llvm-26471c48b3d49bdbcfcc05cb9a575b5fa123fbbf.tar.bz2 | |
Handle a special case xor undef, undef -> 0. Technically this should be transformed to undef. But this is such a common idiom (misuse) we are going to handle it.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48792 91177308-0d34-0410-b5e6-96231b3b80d8
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 762a24a..7b21817 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: |