fanbo-meng created this revision.
fanbo-meng added reviewers: abhina.sreeskantharajan, hubert.reinterpretcast,
Kai, SeanP, rsmith.
fanbo-meng requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.
Zero length bitfield alignment is not respected if they are leading members on
z/OS target.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D98890
Files:
clang/include/clang/Basic/TargetInfo.h
clang/lib/AST/RecordLayoutBuilder.cpp
clang/lib/Basic/TargetInfo.cpp
clang/lib/Basic/Targets/OSTargets.h
clang/test/CodeGen/SystemZ/zos-alignment.c
Index: clang/test/CodeGen/SystemZ/zos-alignment.c
===================================================================
--- clang/test/CodeGen/SystemZ/zos-alignment.c
+++ clang/test/CodeGen/SystemZ/zos-alignment.c
@@ -83,6 +83,35 @@
// CHECK-NEXT: 8 | char *[] b
// CHECK-NEXT: | [sizeof=8, align=8]
+struct s7 {
+ long :0;
+ short a;
+} S7;
+// CHECK: 0 | struct s7
+// CHECK-NEXT: 0:- | long
+// CHECK-NEXT: 0 | short a
+// CHECK-NEXT: | [sizeof=2, align=2]
+
+#pragma pack(2)
+struct s8 {
+ unsigned long :0;
+ long long a;
+} S8;
+#pragma pack()
+// CHECK: 0 | struct s8
+// CHECK-NEXT: 0:- | unsigned long
+// CHECK-NEXT: 0 | long long a
+// CHECK-NEXT: | [sizeof=8, align=2]
+
+struct s9 {
+ unsigned int :0;
+ unsigned short :0;
+} S9;
+// CHECK: 0 | struct s9
+// CHECK-NEXT: 0:- | unsigned int
+// CHECK-NEXT: 0:- | unsigned short
+// CHECK-NEXT: | [sizeof=0, align=1]
+
struct s10 {
unsigned int __attribute__((aligned)) a;
} S10;
Index: clang/lib/Basic/Targets/OSTargets.h
===================================================================
--- clang/lib/Basic/Targets/OSTargets.h
+++ clang/lib/Basic/Targets/OSTargets.h
@@ -790,6 +790,7 @@
this->WCharType = TargetInfo::UnsignedInt;
this->UseBitFieldTypeAlignment = false;
this->UseZeroLengthBitfieldAlignment = true;
+ this->UseLeadingZeroLengthBitfield = false;
this->ZeroLengthBitfieldBoundary = 32;
this->MinGlobalAlign = 0;
this->DefaultAlignForAttributeAligned = 128;
Index: clang/lib/Basic/TargetInfo.cpp
===================================================================
--- clang/lib/Basic/TargetInfo.cpp
+++ clang/lib/Basic/TargetInfo.cpp
@@ -104,6 +104,7 @@
UseSignedCharForObjCBool = true;
UseBitFieldTypeAlignment = true;
UseZeroLengthBitfieldAlignment = false;
+ UseLeadingZeroLengthBitfield = true;
UseExplicitBitFieldAlignment = true;
ZeroLengthBitfieldBoundary = 0;
HalfFormat = &llvm::APFloat::IEEEhalf();
Index: clang/lib/AST/RecordLayoutBuilder.cpp
===================================================================
--- clang/lib/AST/RecordLayoutBuilder.cpp
+++ clang/lib/AST/RecordLayoutBuilder.cpp
@@ -1627,12 +1627,17 @@
// Some such targets do honor it on zero-width bitfields.
if (FieldSize == 0 &&
Context.getTargetInfo().useZeroLengthBitfieldAlignment()) {
- // The alignment to round up to is the max of the field's natural
- // alignment and a target-specific fixed value (sometimes zero).
- unsigned ZeroLengthBitfieldBoundary =
- Context.getTargetInfo().getZeroLengthBitfieldBoundary();
- FieldAlign = std::max(FieldAlign, ZeroLengthBitfieldBoundary);
-
+ // Some targets don't honor leading zero-width bitfield.
+ if (!IsUnion && FieldOffset == 0 &&
+ !Context.getTargetInfo().useLeadingZeroLengthBitfield())
+ FieldAlign = 1;
+ else {
+ // The alignment to round up to is the max of the field's natural
+ // alignment and a target-specific fixed value (sometimes zero).
+ unsigned ZeroLengthBitfieldBoundary =
+ Context.getTargetInfo().getZeroLengthBitfieldBoundary();
+ FieldAlign = std::max(FieldAlign, ZeroLengthBitfieldBoundary);
+ }
// If that doesn't apply, just ignore the field alignment.
} else {
FieldAlign = 1;
Index: clang/include/clang/Basic/TargetInfo.h
===================================================================
--- clang/include/clang/Basic/TargetInfo.h
+++ clang/include/clang/Basic/TargetInfo.h
@@ -155,6 +155,10 @@
/// zero-length bitfield.
unsigned UseZeroLengthBitfieldAlignment : 1;
+ /// Whether zero length bitfield alignment is respected if they are the
+ /// leading members.
+ unsigned UseLeadingZeroLengthBitfield : 1;
+
/// Whether explicit bit field alignment attributes are honored.
unsigned UseExplicitBitFieldAlignment : 1;
@@ -768,6 +772,12 @@
return UseZeroLengthBitfieldAlignment;
}
+ /// Check whether zero length bitfield alignment is respected if they are
+ /// leading members.
+ bool useLeadingZeroLengthBitfield() const {
+ return UseLeadingZeroLengthBitfield;
+ }
+
/// Get the fixed alignment value in bits for a member that follows
/// a zero length bitfield.
unsigned getZeroLengthBitfieldBoundary() const {
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