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| author | David Majnemer <david.majnemer@gmail.com> | 2014-12-18 23:54:43 +0000 |
|---|---|---|
| committer | David Majnemer <david.majnemer@gmail.com> | 2014-12-18 23:54:43 +0000 |
| commit | 824e011ad7b400ef79920ae9f84e5f55375720f2 (patch) | |
| tree | c0f10308543e35c8f479ab06df32bfe20d60637c /llvm/lib/IR/ConstantFold.cpp | |
| parent | 174476ed963beac6131c0b9c65727452689f6a0b (diff) | |
| download | llvm-824e011ad7b400ef79920ae9f84e5f55375720f2.zip llvm-824e011ad7b400ef79920ae9f84e5f55375720f2.tar.gz llvm-824e011ad7b400ef79920ae9f84e5f55375720f2.tar.bz2 | |
ConstantFold: Shifting undef by zero results in undef
llvm-svn: 224553
Diffstat (limited to 'llvm/lib/IR/ConstantFold.cpp')
| -rw-r--r-- | llvm/lib/IR/ConstantFold.cpp | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/llvm/lib/IR/ConstantFold.cpp b/llvm/lib/IR/ConstantFold.cpp index 31e962a..9176bf2 100644 --- a/llvm/lib/IR/ConstantFold.cpp +++ b/llvm/lib/IR/ConstantFold.cpp @@ -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()); } |