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| author | Chris Lattner <sabre@nondot.org> | 2005-10-09 22:12:36 +0000 |
|---|---|---|
| committer | Chris Lattner <sabre@nondot.org> | 2005-10-09 22:12:36 +0000 |
| commit | 1d3dc006744f4bb44ef913797d3a8e3b514db2ce (patch) | |
| tree | 2a61daf503f688204c39a644870913cf565e1450 /llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp | |
| parent | 03b9eb506cd03273010f78b9b03117a3fd538e7e (diff) | |
| download | bcm5719-llvm-1d3dc006744f4bb44ef913797d3a8e3b514db2ce.tar.gz bcm5719-llvm-1d3dc006744f4bb44ef913797d3a8e3b514db2ce.zip | |
(X & Y) & C == 0 if either X&C or Y&C are zero
llvm-svn: 23678
Diffstat (limited to 'llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp')
| -rw-r--r-- | llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp index 9a69fdc5fca..b0206a9dcb5 100644 --- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp @@ -608,11 +608,15 @@ static bool MaskedValueIsZero(const SDOperand &Op, uint64_t Mask, SrcBits = MVT::getSizeInBits(cast<VTSDNode>(Op.getOperand(1))->getVT()); return (Mask & ((1ULL << SrcBits)-1)) == 0; // Returning only the zext bits. case ISD::AND: + // If either of the operands has zero bits, the result will too. + if (MaskedValueIsZero(Op.getOperand(1), Mask, TLI) || + MaskedValueIsZero(Op.getOperand(0), Mask, TLI)) + return true; + // (X & C1) & C2 == 0 iff C1 & C2 == 0. if (ConstantSDNode *AndRHS = dyn_cast<ConstantSDNode>(Op.getOperand(1))) return MaskedValueIsZero(Op.getOperand(0),AndRHS->getValue() & Mask, TLI); - - // FALL THROUGH + return false; case ISD::OR: case ISD::XOR: return MaskedValueIsZero(Op.getOperand(0), Mask, TLI) && |
