[clang] b8f612e - [PowerPC][AIX] Packed zero-width bitfields do not affect alignment.
Sean Fertile via cfe-commits
cfe-commits at lists.llvm.org
Wed Aug 4 08:04:42 PDT 2021
Author: Sean Fertile
Date: 2021-08-04T11:03:25-04:00
New Revision: b8f612e780e50cfb62bc0196b6367e4587949f88
URL: https://github.com/llvm/llvm-project/commit/b8f612e780e50cfb62bc0196b6367e4587949f88
DIFF: https://github.com/llvm/llvm-project/commit/b8f612e780e50cfb62bc0196b6367e4587949f88.diff
LOG: [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
Added:
Modified:
clang/lib/AST/RecordLayoutBuilder.cpp
clang/test/Layout/aix-packed-bitfields.c
Removed:
################################################################################
diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index 972690becf9ec..83045253aa512 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -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
diff erences in layout due to padding or packing.
if (!UseExternalLayout)
diff --git a/clang/test/Layout/aix-packed-bitfields.c b/clang/test/Layout/aix-packed-bitfields.c
index 9bc907af0f596..88f6b3fced80a 100644
--- a/clang/test/Layout/aix-packed-bitfields.c
+++ b/clang/test/Layout/aix-packed-bitfields.c
@@ -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
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