[MS-ABI] Update virtual base padding rules to match MSVC 10+

In version 9 (VS2010) (and prior)? versions of msvc, if the last field
in a record was a bitfield padding equal to the size of the storage
class of that bitfield was added before each vbase and vtordisp.  This
patch removes that feature from clang and updates the lit tests to
reflect it.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@206004 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/AST/RecordLayoutBuilder.cpp b/lib/AST/RecordLayoutBuilder.cpp
index 1ea2be41b3bd3a548c1fcb5846d416cf5dd02ebf..02fbcf0a4ad1ad6071c274cf9c050e5092d39291 100644 (file)
--- a/lib/AST/RecordLayoutBuilder.cpp
+++ b/lib/AST/RecordLayoutBuilder.cpp
@@ -2091,9 +2091,6 @@ static bool isMsLayout(const RecordDecl* D) {
 //   one.
 // * The last zero size virtual base may be placed at the end of the struct.
 //   and can potentially alias a zero sized type in the next struct.
-// * If the last field is a non-zero length bitfield, all virtual bases will
-//   have extra padding added before them for no obvious reason.  The padding
-//   has the same number of bits as the type of the bitfield.
 // * When laying out empty non-virtual bases, an extra byte of padding is added
 //   if the non-virtual base before the empty non-virtual base has a vbptr.
 // * The ABI attempts to avoid aliasing of zero sized bases by adding padding
@@ -2595,10 +2592,6 @@ void MicrosoftRecordLayoutBuilder::layoutVirtualBases(const CXXRecordDecl *RD) {
     const CXXRecordDecl *BaseDecl = I.getType()->getAsCXXRecordDecl();
     const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl);
     bool HasVtordisp = HasVtordispSet.count(BaseDecl);
-    // If the last field we laid out was a non-zero length bitfield then add
-    // some extra padding for no obvious reason.
-    if (LastFieldIsNonZeroWidthBitfield)
-      Size += CurrentBitfieldSize;
     // Insert padding between two bases if the left first one is zero sized or
     // contains a zero sized subobject and the right is zero sized or one leads
     // with a zero sized base.  The padding between virtual bases is 4

diff --git a/test/Layout/ms-x86-bitfields-vbases.cpp b/test/Layout/ms-x86-bitfields-vbases.cpp
index 7cffa8c8e4ac9fba5eace8f6b1231dd47c8e7a3c..5b54596bbb83c89a4b99a85fb1f971da535b75ca 100644 (file)
--- a/test/Layout/ms-x86-bitfields-vbases.cpp
+++ b/test/Layout/ms-x86-bitfields-vbases.cpp
@@ -13,17 +13,17 @@ struct A : virtual B0 { char a : 1; };
 // CHECK-NEXT:    0 | struct A
 // CHECK-NEXT:    0 |   (A vbtable pointer)
 // CHECK-NEXT:    4 |   char a
-// CHECK-NEXT:   12 |   struct B0 (virtual base)
-// CHECK-NEXT:   12 |     int a
-// CHECK-NEXT:      | [sizeof=16, align=4
+// CHECK-NEXT:    8 |   struct B0 (virtual base)
+// CHECK-NEXT:    8 |     int a
+// CHECK-NEXT:      | [sizeof=12, align=4
 // CHECK-NEXT:      |  nvsize=8, nvalign=4]
 // CHECK-X64: *** Dumping AST Record Layout
 // CHECK-X64: *** Dumping AST Record Layout
 // CHECK-X64-NEXT:    0 | struct A
 // CHECK-X64-NEXT:    0 |   (A vbtable pointer)
 // CHECK-X64-NEXT:    8 |   char a
-// CHECK-X64-NEXT:   20 |   struct B0 (virtual base)
-// CHECK-X64-NEXT:   20 |     int a
+// CHECK-X64-NEXT:   16 |   struct B0 (virtual base)
+// CHECK-X64-NEXT:   16 |     int a
 // CHECK-X64-NEXT:      | [sizeof=24, align=8
 // CHECK-X64-NEXT:      |  nvsize=16, nvalign=8]
 
@@ -33,16 +33,16 @@ struct B : virtual B0 { short a : 1; };
 // CHECK-NEXT:    0 | struct B
 // CHECK-NEXT:    0 |   (B vbtable pointer)
 // CHECK-NEXT:    4 |   short a
-// CHECK-NEXT:   12 |   struct B0 (virtual base)
-// CHECK-NEXT:   12 |     int a
-// CHECK-NEXT:      | [sizeof=16, align=4
+// CHECK-NEXT:    8 |   struct B0 (virtual base)
+// CHECK-NEXT:    8 |     int a
+// CHECK-NEXT:      | [sizeof=12, align=4
 // CHECK-NEXT:      |  nvsize=8, nvalign=4]
 // CHECK-X64: *** Dumping AST Record Layout
 // CHECK-X64-NEXT:    0 | struct B
 // CHECK-X64-NEXT:    0 |   (B vbtable pointer)
 // CHECK-X64-NEXT:    8 |   short a
-// CHECK-X64-NEXT:   20 |   struct B0 (virtual base)
-// CHECK-X64-NEXT:   20 |     int a
+// CHECK-X64-NEXT:   16 |   struct B0 (virtual base)
+// CHECK-X64-NEXT:   16 |     int a
 // CHECK-X64-NEXT:      | [sizeof=24, align=8
 // CHECK-X64-NEXT:      |  nvsize=16, nvalign=8]
 
@@ -94,22 +94,22 @@ struct E : virtual B0, virtual B1 { long long : 1; };
 // CHECK-NEXT:    0 | struct E
 // CHECK-NEXT:    0 |   (E vbtable pointer)
 // CHECK-NEXT:    8 |   long long
-// CHECK-NEXT:   24 |   struct B0 (virtual base)
-// CHECK-NEXT:   24 |     int a
-// CHECK-NEXT:   36 |   struct B1 (virtual base)
-// CHECK-NEXT:   36 |     int a
-// CHECK-NEXT:      | [sizeof=40, align=8
+// CHECK-NEXT:   16 |   struct B0 (virtual base)
+// CHECK-NEXT:   16 |     int a
+// CHECK-NEXT:   20 |   struct B1 (virtual base)
+// CHECK-NEXT:   20 |     int a
+// CHECK-NEXT:      | [sizeof=24, align=8
 // CHECK-NEXT:      |  nvsize=16, nvalign=8]
 // CHECK-X64: *** Dumping AST Record Layout
 // CHECK-X64: *** Dumping AST Record Layout
 // CHECK-X64-NEXT:    0 | struct E
 // CHECK-X64-NEXT:    0 |   (E vbtable pointer)
 // CHECK-X64-NEXT:    8 |   long long
-// CHECK-X64-NEXT:   24 |   struct B0 (virtual base)
-// CHECK-X64-NEXT:   24 |     int a
-// CHECK-X64-NEXT:   36 |   struct B1 (virtual base)
-// CHECK-X64-NEXT:   36 |     int a
-// CHECK-X64-NEXT:      | [sizeof=40, align=8
+// CHECK-X64-NEXT:   16 |   struct B0 (virtual base)
+// CHECK-X64-NEXT:   16 |     int a
+// CHECK-X64-NEXT:   20 |   struct B1 (virtual base)
+// CHECK-X64-NEXT:   20 |     int a
+// CHECK-X64-NEXT:      | [sizeof=24, align=8
 // CHECK-X64-NEXT:      |  nvsize=16, nvalign=8]
 
 int a[

diff --git a/test/Layout/ms-x86-pack-and-align.cpp b/test/Layout/ms-x86-pack-and-align.cpp
index 0843b3e0bfe409002b68e32ebdb408841311d07f..be0499c2cbbeb210db446c3d68c2f3c950d8b327 100644 (file)
--- a/test/Layout/ms-x86-pack-and-align.cpp
+++ b/test/Layout/ms-x86-pack-and-align.cpp
@@ -473,7 +473,7 @@ struct RE {
 // CHECK-NEXT:    0 | struct RB2
 // CHECK-NEXT:    0 |   (RB2 vbtable pointer)
 // CHECK-NEXT: 1024 |   int b
-// CHECK-NEXT: 1032 |   struct RA (virtual base) (empty)
+// CHECK-NEXT: 1028 |   struct RA (virtual base) (empty)
 // CHECK-NEXT:      | [sizeof=1032, align=1024
 // CHECK-NEXT:      |  nvsize=1028, nvalign=1024]
 // CHECK: *** Dumping AST Record Layout
@@ -481,7 +481,7 @@ struct RE {
 // CHECK-NEXT:    0 |   (RB3 vftable pointer)
 // CHECK-NEXT: 1024 |   (RB3 vbtable pointer)
 // CHECK-NEXT: 2048 |   int b
-// CHECK-NEXT: 2056 |   struct RA (virtual base) (empty)
+// CHECK-NEXT: 2052 |   struct RA (virtual base) (empty)
 // CHECK-NEXT:      | [sizeof=2056, align=1024
 // CHECK-NEXT:      |  nvsize=2052, nvalign=1024]
 // CHECK: *** Dumping AST Record Layout
@@ -516,7 +516,7 @@ struct RE {
 // CHECK-X64-NEXT:    0 | struct RB2
 // CHECK-X64-NEXT:    0 |   (RB2 vbtable pointer)
 // CHECK-X64-NEXT: 1024 |   int b
-// CHECK-X64-NEXT: 1032 |   struct RA (virtual base) (empty)
+// CHECK-X64-NEXT: 1028 |   struct RA (virtual base) (empty)
 // CHECK-X64-NEXT:      | [sizeof=1032, align=1024
 // CHECK-X64-NEXT:      |  nvsize=1028, nvalign=1024]
 // CHECK-X64: *** Dumping AST Record Layout
@@ -524,7 +524,7 @@ struct RE {
 // CHECK-X64-NEXT:    0 |   (RB3 vftable pointer)
 // CHECK-X64-NEXT: 1024 |   (RB3 vbtable pointer)
 // CHECK-X64-NEXT: 2048 |   int b
-// CHECK-X64-NEXT: 2056 |   struct RA (virtual base) (empty)
+// CHECK-X64-NEXT: 2052 |   struct RA (virtual base) (empty)
 // CHECK-X64-NEXT:      | [sizeof=2056, align=1024
 // CHECK-X64-NEXT:      |  nvsize=2052, nvalign=1024]
 // CHECK-X64: *** Dumping AST Record Layout