diff options
Diffstat (limited to 'lib/CodeGen/SelectionDAG/DAGCombiner.cpp')
| -rw-r--r-- | lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 2c15f39db4..70ff8371f7 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -1664,6 +1664,13 @@ SDOperand DAGCombiner::visitSRL(SDNode *N) { return DAG.getNode(ISD::ANY_EXTEND, VT, SmallShift); } + // fold (srl (sra X, Y), 31) -> (srl X, 31). This srl only looks at the sign + // bit, which is unmodified by sra. + if (N1C && N1C->getValue()+1 == MVT::getSizeInBits(VT)) { + if (N0.getOpcode() == ISD::SRA) + return DAG.getNode(ISD::SRL, VT, N0.getOperand(0), N1); + } + // fold (srl (ctlz x), "5") -> x iff x has one bit set (the low bit). if (N1C && N0.getOpcode() == ISD::CTLZ && N1C->getValue() == Log2_32(MVT::getSizeInBits(VT))) { |