[llvm] r200023 - Restrict FindBetterChain DAG combines to unindexed nodes

[Hal Finkel]

Author: hfinkel
Date: Fri Jan 24 12:25:26 2014
New Revision: 200023

URL: http://llvm.org/viewvc/llvm-project?rev=200023&view=rev
Log:
Restrict FindBetterChain DAG combines to unindexed nodes

These transformations obviously won't work for indexed (pre/post-inc) loads and
stores. In practice, I'm not sure there is any benefit to enabling them for
indexed nodes because other transformations that these might enable likely also
won't handle indexed nodes.

I don't have an in-tree test case that hits this problem, but an upcoming bug
fix will make it much more likely.

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

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=200023&r1=200022&r2=200023&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Fri Jan 24 12:25:26 2014
@@ -7729,7 +7729,7 @@ SDValue DAGCombiner::visitLOAD(SDNode *N
 
   bool UseAA = CombinerAA.getNumOccurrences() > 0 ? CombinerAA :
     TLI.getTargetMachine().getSubtarget<TargetSubtargetInfo>().useAA();
-  if (UseAA) {
+  if (UseAA && LD->isUnindexed()) {
     // Walk up chain skipping non-aliasing memory nodes.
     SDValue BetterChain = FindBetterChain(N, Chain);
 
@@ -9317,7 +9317,7 @@ SDValue DAGCombiner::visitSTORE(SDNode *
 
   bool UseAA = CombinerAA.getNumOccurrences() > 0 ? CombinerAA :
     TLI.getTargetMachine().getSubtarget<TargetSubtargetInfo>().useAA();
-  if (UseAA) {
+  if (UseAA && ST->isUnindexed()) {
     // Walk up chain skipping non-aliasing memory nodes.
     SDValue BetterChain = FindBetterChain(N, Chain);