diff options
| author | Evan Cheng <evan.cheng@apple.com> | 2011-03-15 02:22:10 +0000 |
|---|---|---|
| committer | Evan Cheng <evan.cheng@apple.com> | 2011-03-15 02:22:10 +0000 |
| commit | bf34a5ec22389a852f25337eb767e5ad742e6142 (patch) | |
| tree | 9ac729af529c97791e7a3e82131ecdc2e52a91fb /lib/CodeGen/SelectionDAG/SelectionDAG.cpp | |
| parent | 49c69bb70f4c62d97c02e71c25fd615d67104ff4 (diff) | |
sext(undef) = 0, because the top bits will all be the same.
zext(undef) = 0, because the top bits will be zero.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127649 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen/SelectionDAG/SelectionDAG.cpp')
| -rw-r--r-- | lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp index bcb0ffe3a5..c2711c8097 100644 --- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp +++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp @@ -2483,7 +2483,8 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL, if (OpOpcode == ISD::SIGN_EXTEND || OpOpcode == ISD::ZERO_EXTEND) return getNode(OpOpcode, DL, VT, Operand.getNode()->getOperand(0)); else if (OpOpcode == ISD::UNDEF) - return getUNDEF(VT); + // sext(undef) = 0, because the top bits will all be the same. + return getConstant(0, VT); break; case ISD::ZERO_EXTEND: assert(VT.isInteger() && Operand.getValueType().isInteger() && @@ -2498,6 +2499,9 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL, if (OpOpcode == ISD::ZERO_EXTEND) // (zext (zext x)) -> (zext x) return getNode(ISD::ZERO_EXTEND, DL, VT, Operand.getNode()->getOperand(0)); + else if (OpOpcode == ISD::UNDEF) + // zext(undef) = 0, because the top bits will be zero. + return getConstant(0, VT); break; case ISD::ANY_EXTEND: assert(VT.isInteger() && Operand.getValueType().isInteger() && |