[llvm] r272436 - MemorySSA: fix memory access local dominance function for live on entry

[Sebastian Pop via llvm-commits]

Author: spop
Date: Fri Jun 10 16:36:41 2016
New Revision: 272436

URL: http://llvm.org/viewvc/llvm-project?rev=272436&view=rev
Log:
MemorySSA: fix memory access local dominance function for live on entry

A memory access defined on function entry cannot be locally dominated by another memory access.
The patch was split from http://reviews.llvm.org/D19338 which exposes the problem.

Differential Revision: http://reviews.llvm.org/D21039

Modified:
    llvm/trunk/lib/Transforms/Utils/MemorySSA.cpp

Modified: llvm/trunk/lib/Transforms/Utils/MemorySSA.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/MemorySSA.cpp?rev=272436&r1=272435&r2=272436&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/MemorySSA.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/MemorySSA.cpp Fri Jun 10 16:36:41 2016
@@ -623,6 +623,21 @@ bool MemorySSA::locallyDominates(const M
 
   assert((Dominator->getBlock() == Dominatee->getBlock()) &&
          "Asking for local domination when accesses are in different blocks!");
+
+  // A node dominates itself.
+  if (Dominatee == Dominator)
+    return true;
+
+  // When Dominatee is defined on function entry, it is not dominated by another
+  // memory access.
+  if (isLiveOnEntryDef(Dominatee))
+    return false;
+
+  // When Dominator is defined on function entry, it dominates the other memory
+  // access.
+  if (isLiveOnEntryDef(Dominator))
+    return true;
+
   // Get the access list for the block
   const AccessListType *AccessList = getBlockAccesses(Dominator->getBlock());
   AccessListType::const_reverse_iterator It(Dominator->getIterator());