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| author | Dan Gohman <gohman@apple.com> | 2010-01-19 23:30:49 +0000 |
|---|---|---|
| committer | Dan Gohman <gohman@apple.com> | 2010-01-19 23:30:49 +0000 |
| commit | 954f49014dd45e806e5459d3ed67b0681d4fb63c (patch) | |
| tree | 00c12bac5df536af2c0e0ec390e9d63ce2f52669 /llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | |
| parent | e87668db2645c1be71ef8ace763eedc7137f6f5f (diff) | |
| download | bcm5719-llvm-954f49014dd45e806e5459d3ed67b0681d4fb63c.tar.gz bcm5719-llvm-954f49014dd45e806e5459d3ed67b0681d4fb63c.zip | |
Fold (add x, shl(0 - y, n)) -> sub(x, shl(y, n)), to simplify some code
that SCEVExpander can produce when running on behalf of LSR.
llvm-svn: 93949
Diffstat (limited to 'llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp')
| -rw-r--r-- | llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 7fe908c7302..8883064df99 100644 --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -1088,6 +1088,26 @@ SDValue DAGCombiner::visitADD(SDNode *N) { if (Result.getNode()) return Result; } + // fold (add x, shl(0 - y, n)) -> sub(x, shl(y, n)) + if (N1.getOpcode() == ISD::SHL && + N1.getOperand(0).getOpcode() == ISD::SUB) + if (ConstantSDNode *C = + dyn_cast<ConstantSDNode>(N1.getOperand(0).getOperand(0))) + if (C->getAPIntValue() == 0) + return DAG.getNode(ISD::SUB, N->getDebugLoc(), VT, N0, + DAG.getNode(ISD::SHL, N->getDebugLoc(), VT, + N1.getOperand(0).getOperand(1), + N1.getOperand(1))); + if (N0.getOpcode() == ISD::SHL && + N0.getOperand(0).getOpcode() == ISD::SUB) + if (ConstantSDNode *C = + dyn_cast<ConstantSDNode>(N0.getOperand(0).getOperand(0))) + if (C->getAPIntValue() == 0) + return DAG.getNode(ISD::SUB, N->getDebugLoc(), VT, N1, + DAG.getNode(ISD::SHL, N->getDebugLoc(), VT, + N0.getOperand(0).getOperand(1), + N0.getOperand(1))); + return SDValue(); } |
