When we can't prove that the target of an aggregate copy is
a complete object, the memcpy needs to use the data size of
the structure instead of its sizeof() value.  Fixes PR12204.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@153613 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGStmt.cpp b/lib/CodeGen/CGStmt.cpp
index 670167b..489386d 100644
--- a/lib/CodeGen/CGStmt.cpp
+++ b/lib/CodeGen/CGStmt.cpp
@@ -722,7 +722,8 @@
   if (RV.isScalar()) {
     Builder.CreateStore(RV.getScalarVal(), ReturnValue);
   } else if (RV.isAggregate()) {
-    EmitAggregateCopy(ReturnValue, RV.getAggregateAddr(), Ty);
+    EmitAggregateCopy(ReturnValue, RV.getAggregateAddr(), Ty,
+                      /*volatile*/ false, 0, /*destIsCompleteObject*/ true);
   } else {
     StoreComplexToAddr(RV.getComplexVal(), ReturnValue, false);
   }
@@ -769,7 +770,8 @@
     EmitAggExpr(RV, AggValueSlot::forAddr(ReturnValue, Alignment, Qualifiers(),
                                           AggValueSlot::IsDestructed,
                                           AggValueSlot::DoesNotNeedGCBarriers,
-                                          AggValueSlot::IsNotAliased));
+                                          AggValueSlot::IsNotAliased,
+                                          AggValueSlot::IsCompleteObject));
   }
 
   EmitBranchThroughCleanup(ReturnBlock);