Merging r312022:

------------------------------------------------------------------------
r312022 | hans | 2017-08-29 11:41:00 -0700 (Tue, 29 Aug 2017) | 10 lines

[DAG] Bound loop dependence check in merge optimization.

The loop dependence check looks for dependencies between store merge
candidates not captured by the chain sub-DAG doing a check of
predecessors which may be very large. Conservatively bound number of
nodes checked for compilation time. (Resolves PR34326).

Landing on behalf of Nirav Dave to unblock the 5.0.0 release.

Differential Revision: https://reviews.llvm.org/D37220
------------------------------------------------------------------------


git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_50@312041 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 1 deletions

diff --git a/include/llvm/CodeGen/SelectionDAGNodes.h b/include/llvm/CodeGen/SelectionDAGNodes.h
index 051c93601d3f..5fb69ae232af 100644
--- a/include/llvm/CodeGen/SelectionDAGNodes.h
+++ b/include/llvm/CodeGen/SelectionDAGNodes.h
@@ -801,7 +801,8 @@ public:
   /// if DAG changes.
   static bool hasPredecessorHelper(const SDNode *N,
                                    SmallPtrSetImpl<const SDNode *> &Visited,
-                                   SmallVectorImpl<const SDNode *> &Worklist) {
+                                   SmallVectorImpl<const SDNode *> &Worklist,
+                                   unsigned int MaxSteps = 0) {
     if (Visited.count(N))
       return true;
     while (!Worklist.empty()) {
@@ -816,6 +817,8 @@ public:
       }
       if (Found)
         return true;
+      if (MaxSteps != 0 && Visited.size() >= MaxSteps)
+        return false;
     }
     return false;
   }