1 files changed, 16 insertions, 3 deletions
diff --git a/clang/lib/CodeGen/CGAtomic.cpp b/clang/lib/CodeGen/CGAtomic.cpp
index 1ef5d1035a0..4e52c3630c7 100644
--- a/clang/lib/CodeGen/CGAtomic.cpp
+++ b/clang/lib/CodeGen/CGAtomic.cpp
@@ -1295,10 +1295,23 @@ bool CodeGenFunction::LValueIsSuitableForInlineAtomic(LValue LV) {
 /// performing such an operation can be performed without a libcall.
 bool CodeGenFunction::typeIsSuitableForInlineAtomic(QualType Ty,
                                                     bool IsVolatile) const {
+  // The operation must be volatile for us to make it atomic.
+  if (!IsVolatile)
+    return false;
+  // The -fms-volatile flag must be passed for us to adopt this behavior.
+  if (!CGM.getCodeGenOpts().MSVolatile)
+    return false;
+
   // An atomic is inline if we don't need to use a libcall (e.g. it is builtin).
-  bool AtomicIsInline = getContext().getTargetInfo().hasBuiltinAtomic(
-      getContext().getTypeSize(Ty), getContext().getTypeAlign(Ty));
-  return CGM.getCodeGenOpts().MSVolatile && IsVolatile && AtomicIsInline;
+  if (!getContext().getTargetInfo().hasBuiltinAtomic(
+          getContext().getTypeSize(Ty), getContext().getTypeAlign(Ty)))
+    return false;
+
+  // MSVC doesn't seem to do this for types wider than a pointer.
+  if (getContext().getTypeSize(Ty) >
+      getContext().getTypeSize(getContext().getIntPtrType()))
+    return false;
+  return true;
 }
 
 RValue CodeGenFunction::EmitAtomicLoad(LValue LV, SourceLocation SL,