[BasicAA] Teach the analysis about atomic memcpy

Summary:
A simple change to derive mod/ref info from the atomic memcpy
intrinsic in the same way as from the regular memcpy intrinsic.

llvm-svn: 333454
diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
index c7839bc..0167751 100644
--- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -888,7 +888,7 @@
   // operands, i.e., source and destination of any given memcpy must no-alias.
   // If Loc must-aliases either one of these two locations, then it necessarily
   // no-aliases the other.
-  if (auto *Inst = dyn_cast<MemCpyInst>(CS.getInstruction())) {
+  if (auto *Inst = dyn_cast<AnyMemCpyInst>(CS.getInstruction())) {
     AliasResult SrcAA, DestAA;
 
     if ((SrcAA = getBestAAResults().alias(MemoryLocation::getForSource(Inst),