[PATCH] MS ABI: Consider alignment attributes on typedefs for layout

[Reid Kleckner]

I'm skeptical that only one bit is enough information here...

================
Comment at: include/clang/AST/ASTContext.h:147
@@ +146,3 @@
+public:
+  struct TypeInfo {
+    uint64_t Width;
----------------
I'd rather just throw this in clang::.  We can use it in record layout.

================
Comment at: include/clang/AST/ASTContext.h:1658-1663
@@ -1647,8 +1657,8 @@
   /// bits.
   unsigned getTypeAlign(QualType T) const {
-    return getTypeInfo(T).second;
+    return getTypeInfo(T).Align;
   }
   unsigned getTypeAlign(const Type *T) const {
-    return getTypeInfo(T).second;
+    return getTypeInfo(T).Align;
   }
 
----------------
Grumble grumble these helpers are just asking you to do multiple hash table lookups....  Nothing to do here, though.

================
Comment at: test/Layout/ms-x86-pack-and-align.cpp:675
@@ -656,1 +674,3 @@
+// CHECK-NEXT:      | [sizeof=16, align=8
+// CHECK-NEXT:      |  nvsize=12, nvalign=8]
 
----------------
Can you also add this test, just to satisfy my curiosity?
  typedef int __declspec(align(2)) my_int_t;
  #pragma pack(push, 1)
  struct A {
    char a;
    my_int_t b;
  };
  #pragma pack(pop)
  static_assert(sizeof(A) == 6, "");

I suspect because the required alignment is actually *lower* than the natural alignment of int, we will take the max alignment between the alignment attribute and the natural alignment get sizeof(A) == 8.

http://reviews.llvm.org/D4714