maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[PowerPC][AIX] Packed zero-width bitfields do not affect alignment. 

Zero-width bitfields on AIX pad out to the natral alignment boundary but
do not change the containing records alignment.

Differential Revision: https://reviews.llvm.org/D106900
This commit is contained in:
Sean Fertile 2021-08-04 11:01:00 -04:00
parent ba5c4ac600
commit b8f612e780
2 changed files with 54 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
clang/lib/AST/RecordLayoutBuilder.cpp
View File

@ -1775,11 +1775,18 @@ void ItaniumRecordLayoutBuilder::LayoutBitField(const FieldDecl *D) {
!D->getIdentifier())
FieldAlign = UnpackedFieldAlign = 1;
// On AIX, zero-width bitfields pad out to the alignment boundary, but then
// do not affect overall record alignment if there is a pragma pack or
// pragma align(packed).
if (isAIXLayout(Context) && !MaxFieldAlignment.isZero() && !FieldSize)
FieldAlign = std::min(FieldAlign, MaxFieldAlignmentInBits);
// On AIX, zero-width bitfields pad out to the natural alignment boundary,
// but do not increase the alignment greater than the MaxFieldAlignment, or 1
// if packed.
if (isAIXLayout(Context) && !FieldSize) {
if (FieldPacked)
FieldAlign = 1;
if (!MaxFieldAlignment.isZero()) {
UnpackedFieldAlign =
std::min(UnpackedFieldAlign, MaxFieldAlignmentInBits);
FieldAlign = std::min(FieldAlign, MaxFieldAlignmentInBits);
}
}
// Diagnose differences in layout due to padding or packing.
if (!UseExternalLayout)

48
clang/test/Layout/aix-packed-bitfields.c
View File

@ -1,14 +1,18 @@
// RUN: %clang_cc1 -triple powerpc-ibm-aix-xcoff -fdump-record-layouts \
// RUN: -fsyntax-only -fxl-pragma-pack -x c %s | FileCheck %s
// RUN: -fsyntax-only -fxl-pragma-pack -x c %s | \
// RUN: FileCheck --check-prefixes=CHECK,32BIT %s
// RUN: %clang_cc1 -triple powerpc-ibm-aix-xcoff -fdump-record-layouts \
// RUN: -fsyntax-only -fxl-pragma-pack -x c++ %s | FileCheck %s
//
// RUN: -fsyntax-only -fxl-pragma-pack -x c++ %s | \
// RUN: FileCheck --check-prefixes=CHECK,32BIT %s
// RUN: %clang_cc1 -triple powerpc64-ibm-aix-xcoff -fdump-record-layouts \
// RUN: -fsyntax-only -fxl-pragma-pack -x c %s | FileCheck %s
//
// RUN: -fsyntax-only -fxl-pragma-pack -x c %s | \
// RUN: FileCheck --check-prefixes=CHECK,64BIT %s
// RUN: %clang_cc1 -triple powerpc64-ibm-aix-xcoff -fdump-record-layouts \
// RUN: -fsyntax-only -fxl-pragma-pack -x c++ %s | FileCheck %s
// RUN: -fsyntax-only -fxl-pragma-pack -x c++ %s | \
// RUN: FileCheck --check-prefixes=CHECK,64BIT %s
struct A {
int a1 : 30;
@ -75,3 +79,35 @@ int d = sizeof(struct Pack2);
// CHECK-NEXT: 3:6-35 | int a2
// CHECK-NEXT: 7:4-7 | int a3
// CHECK-NEXT: sizeof=8, {{(dsize=8, )?}}align=2, preferredalign=2
//
struct __attribute__((packed)) PackedAttr {
char f1;
int : 0;
short : 3;
char f4 : 2;
};
int e = sizeof(struct PackedAttr);
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct PackedAttr
// CHECK-NEXT: 0 | char f1
// CHECK-NEXT: 4:- | int
// CHECK-NEXT: 4:0-2 | short
// CHECK-NEXT: 4:3-4 | char f4
// CHECK-NEXT: sizeof=5, {{(dsize=5, )?}}align=1, preferredalign=1
#pragma pack(2)
struct __attribute__((packed)) PackedAttrAndPragma {
char f1;
long long : 0;
};
#pragma pack(pop)
int f = sizeof(struct PackedAttrAndPragma);
// CHECK: *** Dumping AST Record Layout
// CHECK-NEXT: 0 | struct PackedAttrAndPragma
// CHECK-NEXT: 0 | char f1
// 32BIT-NEXT: 4:- | long long
// 32BIT-NEXT: sizeof=4, {{(dsize=4, )?}}align=1, preferredalign=1
// 64BIT-NEXT: 8:- | long long
// 64BIT-NEXT: sizeof=8, {{(dsize=8, )?}}align=1, preferredalign=1