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[ms-abi] Adjusting Rules for Padding Between Bases 

The presence of a VBPtr suppresses the presence of zero sized 
sub-objects in the non-virtual portion of the object in the context of 
determining if two base objects need alias-avoidance padding placed 
between them.

Test cases included.

llvm-svn: 198975
This commit is contained in:
Warren Hunt 2014-01-10 23:32:32 +00:00
parent b8912b4f28
commit 87c2b0400d
2 changed files with 75 additions and 7 deletions
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6
clang/lib/AST/RecordLayoutBuilder.cpp
View File

@ -2477,6 +2477,9 @@ void MicrosoftRecordLayoutBuilder::injectVBPtr(const CXXRecordDecl *RD) {
i->second += Offset;
// Update the object alignment.
updateAlignment(PointerInfo.Alignment);
// The presence of a vbptr suppresses zero sized objects that are not in
// virtual bases.
HasZeroSizedSubObject = false;
}
void MicrosoftRecordLayoutBuilder::injectVFPtr(const CXXRecordDecl *RD) {
@ -2566,6 +2569,9 @@ void MicrosoftRecordLayoutBuilder::injectVPtrs(const CXXRecordDecl *RD) {
}
}
layoutFields(RD);
// The presence of a vbptr suppresses zero sized objects that are not in
// virtual bases.
HasZeroSizedSubObject = false;
}
void MicrosoftRecordLayoutBuilder::layoutVirtualBases(const CXXRecordDecl *RD) {

76
clang/test/Layout/ms-x86-alias-avoidance-padding.cpp
View File

@ -139,29 +139,29 @@ struct BT3 : BT0, BT2 {
struct T0 : AT {
T0() {
printf("T0 (this) : %d\n", (char*)this - buffer);
printf("T0 (this) : %d\n", (int)((char*)this - buffer));
}
};
struct T1 : T0 {
char a;
T1() {
printf("T1 (this) : %d\n", (char*)this - buffer);
printf("T1 (fiel) : %d\n", (char*)&a - buffer);
printf("T1 (this) : %d\n", (int)((char*)this - buffer));
printf("T1 (fiel) : %d\n", (int)((char*)&a - buffer));
}
};
struct T2 : AT {
char a;
T2() {
printf("T2 (this) : %d\n", (char*)this - buffer);
printf("T2 (fiel) : %d\n", (char*)&a - buffer);
printf("T2 (this) : %d\n", (int)((char*)this - buffer));
printf("T2 (fiel) : %d\n", (int)((char*)&a - buffer));
}
};
struct __declspec(align(1)) T3 : virtual T1, virtual T2 {
T3() {
printf("T3 (this) : %d\n", (char*)this - buffer);
printf("T3 (this) : %d\n", (int)((char*)this - buffer));
}
};
@ -196,7 +196,69 @@ struct __declspec(align(1)) T3 : virtual T1, virtual T2 {
// CHECK-X64-NEXT: | [sizeof=24, align=8
// CHECK-X64-NEXT: | nvsize=8, nvalign=8]
struct B {};
struct C { int a; };
struct D : B, virtual C { B b; };
struct E : D, B {};
// CHECK: *** Dumping AST Record Layout
// CHECK: *** Dumping AST Record Layout
// CHECK: *** Dumping AST Record Layout
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct E
// CHECK-NEXT: 0 | struct D (base)
// CHECK-NEXT: 4 | struct B (base) (empty)
// CHECK-NEXT: 0 | (D vbtable pointer)
// CHECK-NEXT: 4 | struct B b (empty)
// CHECK: 8 | struct B (base) (empty)
// CHECK-NEXT: 8 | struct C (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: *** Dumping AST Record Layout
// CHECK-X64: *** Dumping AST Record Layout
// CHECK-X64-NEXT: 0 | struct E
// CHECK-X64-NEXT: 0 | struct D (base)
// CHECK-X64-NEXT: 8 | struct B (base) (empty)
// CHECK-X64-NEXT: 0 | (D vbtable pointer)
// CHECK-X64-NEXT: 8 | struct B b (empty)
// CHECK-X64: 16 | struct B (base) (empty)
// CHECK-X64-NEXT: 16 | struct C (virtual base)
// CHECK-X64-NEXT: 16 | int a
// CHECK-X64-NEXT: | [sizeof=24, align=8
// CHECK-X64-NEXT: | nvsize=16, nvalign=8]
struct F : virtual D, virtual B {};
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct F
// CHECK-NEXT: 0 | (F vbtable pointer)
// CHECK-NEXT: 4 | struct C (virtual base)
// CHECK-NEXT: 4 | int a
// CHECK-NEXT: 8 | struct D (virtual base)
// CHECK-NEXT: 12 | struct B (base) (empty)
// CHECK-NEXT: 8 | (D vbtable pointer)
// CHECK-NEXT: 12 | struct B b (empty)
// CHECK: 16 | struct B (virtual base) (empty)
// CHECK-NEXT: | [sizeof=16, align=4
// CHECK-NEXT: | nvsize=4, nvalign=4]
// CHECK-X64: *** Dumping AST Record Layout
// CHECK-X64-NEXT: 0 | struct F
// CHECK-X64-NEXT: 0 | (F vbtable pointer)
// CHECK-X64-NEXT: 8 | struct C (virtual base)
// CHECK-X64-NEXT: 8 | int a
// CHECK-X64-NEXT: 16 | struct D (virtual base)
// CHECK-X64-NEXT: 24 | struct B (base) (empty)
// CHECK-X64-NEXT: 16 | (D vbtable pointer)
// CHECK-X64-NEXT: 24 | struct B b (empty)
// CHECK-X64: 32 | struct B (virtual base) (empty)
// CHECK-X64-NEXT: | [sizeof=32, align=8
// CHECK-X64-NEXT: | nvsize=8, nvalign=8]
int a[
sizeof(AT3) +
sizeof(BT3) +
sizeof(T3)];
sizeof(T3) +
sizeof(E) +
sizeof(F) +
0];