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| author | Chris Lattner <sabre@nondot.org> | 2006-10-12 20:23:19 +0000 |
|---|---|---|
| committer | Chris Lattner <sabre@nondot.org> | 2006-10-12 20:23:19 +0000 |
| commit | 2e33fb453bd4330285007a22ae53e8b3521aba6a (patch) | |
| tree | 3b1925225a0c698a6f149bf594e89e96e174f65f /llvm/lib/CodeGen/SelectionDAG | |
| parent | a7956d2894cedf46fd3b36e8d0301588edad11c8 (diff) | |
| download | bcm5719-llvm-2e33fb453bd4330285007a22ae53e8b3521aba6a.tar.gz bcm5719-llvm-2e33fb453bd4330285007a22ae53e8b3521aba6a.zip | |
add a minor dag combine noticed when looking at PR945
llvm-svn: 30915
Diffstat (limited to 'llvm/lib/CodeGen/SelectionDAG')
| -rw-r--r-- | llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 2c15f39db4a..70ff8371f79 100644 --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/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))) { |
