[PATCH] D53658: [DAG] Inspect more store operands for cycle before merging.

[Tim Northover via Phabricator via llvm-commits]

t.p.northover updated this revision to Diff 170929.
t.p.northover added a comment.

Fixing capitalization of variable. Oops.


Repository:
  rL LLVM

https://reviews.llvm.org/D53658

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


Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -14316,14 +14316,14 @@
     //                    in candidate selection and can be
     //                    safely ignored
     //   * Value (Op 1) -> Cycles may happen (e.g. through load chains)
-    //   * Address (Op 2) -> Merged addresses may only vary by a fixed constant
-    //                      and so no cycles are possible.
-    //   * (Op 3) -> appears to always be undef. Cannot be source of cycle.
-    //
-    // Thus we need only check predecessors of the value operands.
-    auto *Op = N->getOperand(1).getNode();
-    if (Visited.insert(Op).second)
-      Worklist.push_back(Op);
+    //   * Address (Op 2) -> Merged addresses may only vary by a fixed constant,
+    //                       but aren't necessarily fromt the same base node, so
+    //                       cycles possible (e.g. via indexed store).
+    //   * (Op 3) -> Represents the pre or post-indexing offset (or undef for
+    //               non-indexed stores). Not constant on all targets (e.g. ARM)
+    //               and so can participate in a cycle.
+    for (unsigned j = 1; j < N->getNumOperands(); ++j)
+      Worklist.push_back(N->getOperand(j).getNode());
   }
   // Search through DAG. We can stop early if we find a store node.
   for (unsigned i = 0; i < NumStores; ++i)


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