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| author | David Majnemer <david.majnemer@gmail.com> | 2014-12-10 21:58:15 +0000 |
|---|---|---|
| committer | David Majnemer <david.majnemer@gmail.com> | 2014-12-10 21:58:15 +0000 |
| commit | 5a7717e498bc61246375a9df0061afa27d21e322 (patch) | |
| tree | 94f451a24757b23f737a19be9df22968c1d11f39 /llvm/lib/IR/ConstantFold.cpp | |
| parent | 89cf6d79ebc573647c562e5f2bd6c4d11a839f8b (diff) | |
| download | llvm-5a7717e498bc61246375a9df0061afa27d21e322.zip llvm-5a7717e498bc61246375a9df0061afa27d21e322.tar.gz llvm-5a7717e498bc61246375a9df0061afa27d21e322.tar.bz2 | |
ConstantFold, InstSimplify: undef >>a x can be either -1 or 0, choose 0
Zero is usually a nicer constant to have than -1.
llvm-svn: 223969
Diffstat (limited to 'llvm/lib/IR/ConstantFold.cpp')
| -rw-r--r-- | llvm/lib/IR/ConstantFold.cpp | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/llvm/lib/IR/ConstantFold.cpp b/llvm/lib/IR/ConstantFold.cpp index 49ef302..a05c594 100644 --- a/llvm/lib/IR/ConstantFold.cpp +++ b/llvm/lib/IR/ConstantFold.cpp @@ -960,8 +960,9 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, // X >>a undef -> undef if (isa<UndefValue>(C2)) return C2; - // undef >>a X -> all ones - return Constant::getAllOnesValue(C1->getType()); + // TODO: undef >>a X -> undef if the shift is exact + // undef >>a X -> 0 + return Constant::getNullValue(C1->getType()); case Instruction::Shl: // X << undef -> undef if (isa<UndefValue>(C2)) |