[PATCH] D33840: [DAGCombine] Do not try to deduplicate commutative operations if both operand are the same.

[Amaury SECHET via Phabricator via llvm-commits]

deadalnix created this revision.

It is creating useless work as the commuted nodes is the same as the node we are working on in that case.


https://reviews.llvm.org/D33840

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp


Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1569,7 +1569,7 @@
     SDValue N1 = N->getOperand(1);
 
     // Constant operands are canonicalized to RHS.
-    if (isa<ConstantSDNode>(N0) || !isa<ConstantSDNode>(N1)) {
+    if (N0 != N1 && (isa<ConstantSDNode>(N0) || !isa<ConstantSDNode>(N1))) {
       SDValue Ops[] = {N1, N0};
       SDNode *CSENode = DAG.getNodeIfExists(N->getOpcode(), N->getVTList(), Ops,
                                             N->getFlags());


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