diff options
| 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 | cd9e155755dab1913238ffc0374111a39d500adf (patch) | |
| tree | dca492914248b99ff3fd5ddff75e3edf2ad66201 /lib/CodeGen/SelectionDAG/DAGCombiner.cpp | |
| parent | cb9a6aab02f07cda005c7c078d8e4a3463017866 (diff) | |
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.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93949 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen/SelectionDAG/DAGCombiner.cpp')
| -rw-r--r-- | lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 7fe908c730..8883064df9 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/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(); } |