r323921 - [PR32482] Fix bitfield layout for -mms-bitfield and pragma pack

[Alex Lorenz via cfe-commits]

Author: arphaman
Date: Wed Jan 31 13:59:02 2018
New Revision: 323921

URL: http://llvm.org/viewvc/llvm-project?rev=323921&view=rev
Log:
[PR32482] Fix bitfield layout for -mms-bitfield and pragma pack

The patch ensures that a new storage unit is created when the new bitfield's
size is wider than the available bits.

rdar://36343145

Differential Revision: https://reviews.llvm.org/D42660

Modified:
    cfe/trunk/lib/AST/RecordLayoutBuilder.cpp
    cfe/trunk/test/CodeGen/mms-bitfields.c
    cfe/trunk/test/Sema/mms-bitfields.c

Modified: cfe/trunk/lib/AST/RecordLayoutBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/RecordLayoutBuilder.cpp?rev=323921&r1=323920&r2=323921&view=diff
==============================================================================
--- cfe/trunk/lib/AST/RecordLayoutBuilder.cpp (original)
+++ cfe/trunk/lib/AST/RecordLayoutBuilder.cpp Wed Jan 31 13:59:02 2018
@@ -1504,9 +1504,10 @@ void ItaniumRecordLayoutBuilder::LayoutB
     FieldAlign = TypeSize;
 
     // If the previous field was not a bitfield, or was a bitfield
-    // with a different storage unit size, we're done with that
-    // storage unit.
-    if (LastBitfieldTypeSize != TypeSize) {
+    // with a different storage unit size, or if this field doesn't fit into
+    // the current storage unit, we're done with that storage unit.
+    if (LastBitfieldTypeSize != TypeSize ||
+        UnfilledBitsInLastUnit < FieldSize) {
       // Also, ignore zero-length bitfields after non-bitfields.
       if (!LastBitfieldTypeSize && !FieldSize)
         FieldAlign = 1;

Modified: cfe/trunk/test/CodeGen/mms-bitfields.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/mms-bitfields.c?rev=323921&r1=323920&r2=323921&view=diff
==============================================================================
--- cfe/trunk/test/CodeGen/mms-bitfields.c (original)
+++ cfe/trunk/test/CodeGen/mms-bitfields.c Wed Jan 31 13:59:02 2018
@@ -20,3 +20,46 @@ struct s3 {
 } s3;
 
 // CHECK: %struct.s3 = type { i32, [4 x i8], %struct.s1 }
+
+// PR32482:
+
+#pragma pack (push,1)
+
+typedef unsigned int UINT32;
+
+struct Inner {
+  UINT32    A    :  1;
+  UINT32    B    :  1;
+  UINT32    C    :  1;
+  UINT32    D    : 30;
+} Inner;
+
+#pragma pack (pop)
+
+// CHECK: %struct.Inner = type { i32, i32 }
+
+// CHECK: %struct.A = type { i32, i32, i32 }
+
+#pragma pack(push, 1)
+
+union HEADER {
+  struct A {
+    int                                         :  3;  // Bits 2:0
+    int a                                       :  9;  // Bits 11:3
+    int                                         :  12;  // Bits 23:12
+    int b                                       :  17;  // Bits 40:24
+    int                                         :  7;  // Bits 47:41
+    int c                                       :  4;  // Bits 51:48
+    int                                         :  4;  // Bits 55:52
+    int d                                       :  3;  // Bits 58:56
+    int                                         :  5;  // Bits 63:59
+  } Bits;
+} HEADER;
+
+#pragma pack(pop)
+
+struct Inner variable = { 1,0,1, 21 };
+union HEADER hdr = {{1,2,3,4}};
+
+// CHECK: @variable = global { i8, [3 x i8], i8, i8, i8, i8 } { i8 5, [3 x i8] undef, i8 21, i8 0, i8 0, i8 0 }, align 1
+// CHECK: @hdr = global { { i8, i8, [2 x i8], i8, i8, i8, i8, i8, [3 x i8] } } { { i8, i8, [2 x i8], i8, i8, i8, i8, i8, [3 x i8] } { i8 8, i8 0, [2 x i8] undef, i8 2, i8 0, i8 0, i8 3, i8 4, [3 x i8] undef } }, align 1

Modified: cfe/trunk/test/Sema/mms-bitfields.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/mms-bitfields.c?rev=323921&r1=323920&r2=323921&view=diff
==============================================================================
--- cfe/trunk/test/Sema/mms-bitfields.c (original)
+++ cfe/trunk/test/Sema/mms-bitfields.c Wed Jan 31 13:59:02 2018
@@ -11,3 +11,18 @@ struct
 
 // MS pads out bitfields between different types.
 static int arr[(sizeof(t) == 8) ? 1 : -1];
+
+#pragma pack (push,1)
+
+typedef unsigned int UINT32;
+
+struct Inner {
+  UINT32    A    :  1;
+  UINT32    B    :  1;
+  UINT32    C    :  1;
+  UINT32    D    : 30;
+} Inner;
+
+#pragma pack (pop)
+
+static int arr2[(sizeof(Inner) == 8) ? 1 : -1];