MS ABI: Implement /volatile:ms

The /volatile:ms semantics turn volatile loads and stores into atomic
acquire and release operations.  This distinction is important because
volatile memory operations do not form a happens-before relationship
with non-atomic memory.  This means that a volatile store is not
sufficient for implementing a mutex unlock routine.

Differential Revision: http://reviews.llvm.org/D7580

llvm-svn: 229082

1 files changed, 5 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CGExprAgg.cpp b/clang/lib/CodeGen/CGExprAgg.cpp
index 80b16dd5ba3..dd2da23cd85 100644
--- a/clang/lib/CodeGen/CGExprAgg.cpp
+++ b/clang/lib/CodeGen/CGExprAgg.cpp
@@ -212,7 +212,7 @@ void AggExprEmitter::EmitAggLoadOfLValue(const Expr *E) {
   LValue LV = CGF.EmitLValue(E);
 
   // If the type of the l-value is atomic, then do an atomic load.
-  if (LV.getType()->isAtomicType()) {
+  if (LV.getType()->isAtomicType() || CGF.LValueIsSuitableForInlineAtomic(LV)) {
     CGF.EmitAtomicLoad(LV, E->getExprLoc(), Dest);
     return;
   }
@@ -865,7 +865,8 @@ void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
     LValue LHS = CGF.EmitCheckedLValue(E->getLHS(), CodeGenFunction::TCK_Store);
 
     // That copy is an atomic copy if the LHS is atomic.
-    if (LHS.getType()->isAtomicType()) {
+    if (LHS.getType()->isAtomicType() ||
+        CGF.LValueIsSuitableForInlineAtomic(LHS)) {
       CGF.EmitAtomicStore(Dest.asRValue(), LHS, /*isInit*/ false);
       return;
     }
@@ -882,7 +883,8 @@ void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
 
   // If we have an atomic type, evaluate into the destination and then
   // do an atomic copy.
-  if (LHS.getType()->isAtomicType()) {
+  if (LHS.getType()->isAtomicType() ||
+      CGF.LValueIsSuitableForInlineAtomic(LHS)) {
     EnsureDest(E->getRHS()->getType());
     Visit(E->getRHS());
     CGF.EmitAtomicStore(Dest.asRValue(), LHS, /*isInit*/ false);