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

[Amaury SECHET via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL310832: [DAGCombine] Do not try to deduplicate commutative operations if both operand… (authored by deadalnix).

Repository:
  rL LLVM

https://reviews.llvm.org/D33840

Files:
  llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp


Index: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1614,15 +1614,15 @@
     }
   }
 
-  // If N is a commutative binary node, try commuting it to enable more
-  // sdisel CSE.
+  // If N is a commutative binary node, try eliminate it if the commuted
+  // version is already present in the DAG.
   if (!RV.getNode() && TLI.isCommutativeBinOp(N->getOpcode()) &&
       N->getNumValues() == 1) {
     SDValue N0 = N->getOperand(0);
     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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