Support pack pragma and ms_struct attributes. // rdar://8823265

llvm-svn: 131142

clang/lib/AST/RecordLayoutBuilder.cpp

@@ -1299,6 +1299,13 @@ void RecordLayoutBuilder::LayoutFields(const RecordDecl *D) {
           uint64_t UnpaddedFieldOffset = 
             getDataSizeInBits() - UnfilledBitsInLastByte;
           FieldAlign = std::max(FieldAlign, FieldAlignLastFD);
+          // The maximum field alignment overrides the aligned attribute.
+          if (!MaxFieldAlignment.isZero()) {
+            unsigned MaxFieldAlignmentInBits = 
+              Context.toBits(MaxFieldAlignment);
+            FieldAlign = std::min(FieldAlign, MaxFieldAlignmentInBits);
+          }
+
           uint64_t NewSizeInBits = 
             llvm::RoundUpToAlignment(UnpaddedFieldOffset, FieldAlign);
           setDataSize(llvm::RoundUpToAlignment(NewSizeInBits,

clang/test/CodeGen/ms_struct-pack.c

@@ -0,0 +1,34 @@
+// RUN: %clang_cc1 -emit-llvm-only  -triple i386-apple-darwin9 %s
+// rdar://8823265
+
+#pragma pack(1)
+struct _two_ms {
+        short m:9;      // size is 2
+        int q:27;       // size is 6
+        short w:13;     // size is 8
+        short e:3;      // size is 8
+        char r:4;       // size is 9
+        char t:7;       // size is 10
+        short y:16;     // size is 12
+// clang and gcc start differing here. clang seems to follow the rules.
+        short u:1;      // size is clang: 13 gcc:14 
+        char i:2;       // size is 14
+        int a;          // size is 18
+        char o:6;       // size is 19
+        char s:2;       // size is 19
+        short d:10;     // size is 21
+        short f:4;      // size is 21
+        char b;         // size is 22
+        char g:1;       // size is 23
+        short h:13;     // size is 25
+        char j:8;       // size is 26
+        char k:5;       // size is 27
+        char c;         // size is 28
+        int l:28;       // size is 32
+        char z:7;       // size is 33
+        int x:20;       // size is clang: 36 gcc:38
+        } __attribute__((__ms_struct__));
+typedef struct _two_ms two_ms;
+
+// gcc says size is 38, but its does not seem right!
+static int a1[(sizeof(two_ms) == 36) - 1];