Teach DAG combiner to commute commutable binary nodes in order to achieve sdisel CSE.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48673 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 579870e..9feefb9 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -758,6 +758,23 @@
}
}
+ // If N is a commutative binary node, try commuting it to enable more
+ // sdisel CSE.
+ if (RV.Val == 0 &&
+ SelectionDAG::isCommutativeBinOp(N->getOpcode()) &&
+ N->getNumValues() == 1) {
+ SDOperand N0 = N->getOperand(0);
+ SDOperand N1 = N->getOperand(1);
+ // Constant operands are canonicalized to RHS.
+ if (isa<ConstantSDNode>(N0) || !isa<ConstantSDNode>(N1)) {
+ SDOperand Ops[] = { N1, N0 };
+ SDNode *CSENode = DAG.getNodeIfExists(N->getOpcode(), N->getVTList(),
+ Ops, 2);
+ if (CSENode && CSENode->use_size() <= N->use_size())
+ return SDOperand(CSENode, 0);
+ }
+ }
+
return RV;
}