[PATCH] D56719: [DAGCombine] Enable more pre-indexed stores

[Eli Friedman via Phabricator via llvm-commits]

efriedma added subscribers: kparzysz, efriedma.
efriedma added inline comments.


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Comment at: lib/CodeGen/SelectionDAG/DAGCombiner.cpp:12644
+    if (BasePtr.getNode()->isPredecessorOf(Val.getNode())) {
+      // Check whether the store is in the final user of the base pointer.
+      for (auto *U : BasePtr.getNode()->uses()) {
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This needs a better comment explaining exactly what cases this is rejecting, and which cases it is accepting.  (I'm not sure I follow the logic here.  What cases need to be rejected for correctness?  Are there cases which could be transformed, but shouldn't be transformed to avoid register copies?)

I'm a bit concerned about performance here. isPredecessorOf is expensive.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D56719/new/

https://reviews.llvm.org/D56719