[MS Volatile] Don't make volatile loads/stores to underaligned objects atomic

Underaligned atomic LValues require libcalls which MSVC doesn't have.
MSVC doesn't seem to consider such operations as requiring a barrier
anyway.

This fixes PR27843.

llvm-svn: 270576

1 files changed, 14 insertions, 1 deletions

diff --git a/clang/test/CodeGen/ms-volatile.c b/clang/test/CodeGen/ms-volatile.c
index 242ce067d62..a3ef35a3faa 100644
--- a/clang/test/CodeGen/ms-volatile.c
+++ b/clang/test/CodeGen/ms-volatile.c
@@ -7,6 +7,13 @@ struct bar {
 };
 typedef _Complex float __declspec(align(8)) baz;
 
+#pragma pack(push)
+#pragma pack(1)
+struct qux {
+   volatile int f;
+};
+#pragma pack(pop)
+
 void test1(struct foo *p, struct foo *q) {
   *p = *q;
   // CHECK-LABEL: @test1
@@ -58,7 +65,8 @@ void test8(volatile double *p, volatile double *q) {
 void test9(volatile baz *p, baz *q) {
   *p = *q;
   // CHECK-LABEL: @test9
-  // CHECK: store atomic volatile {{.*}}, {{.*}} release
+  // CHECK: store volatile {{.*}}, {{.*}}
+  // CHECK: store volatile {{.*}}, {{.*}}
 }
 void test10(volatile long long *p, volatile long long *q) {
   *p = *q;
@@ -72,3 +80,8 @@ void test11(volatile float *p, volatile float *q) {
   // CHECK: load atomic volatile {{.*}} acquire
   // CHECK: store atomic volatile {{.*}}, {{.*}} release
 }
+int test12(struct qux *p) {
+  return p->f;
+  // CHECK-LABEL: @test12
+  // CHECK: load volatile {{.*}}
+}