baby steps toward fixing some problems with inbound GEPs that overflow, as discussed 2 months ago or so.
Make sure we do not emit index computations with NSW flags so that we dont get an undef value if the GEP overflows

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160589 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/MemoryBuiltins.cpp b/lib/Analysis/MemoryBuiltins.cpp
index 39edaaf..8d99ec3 100644
--- a/lib/Analysis/MemoryBuiltins.cpp
+++ b/lib/Analysis/MemoryBuiltins.cpp
@@ -645,7 +645,7 @@
   if (!bothKnown(PtrData))
     return unknown();
 
-  Value *Offset = EmitGEPOffset(&Builder, *TD, &GEP);
+  Value *Offset = EmitGEPOffset(&Builder, *TD, &GEP, /*NoAssumptions=*/true);
   Offset = Builder.CreateAdd(PtrData.second, Offset);
   return std::make_pair(PtrData.first, Offset);
 }