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Fix tbaa.struct metadata for bitfields using big endian. #87753

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Merged
merged 2 commits into from
Apr 5, 2024
Merged

Fix tbaa.struct metadata for bitfields using big endian. #87753

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db1ee85
Fix tbaa.struct metadata for bitfields using big endian.
juliannagele Apr 4, 2024
bdfc7dd
fixup! Fix tbaa.struct metadata for bitfields using big endian.
juliannagele Apr 5, 2024
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9 changes: 8 additions & 1 deletion clang/lib/CodeGen/CodeGenTBAA.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@
#include "clang/AST/Mangle.h"
#include "clang/AST/RecordLayout.h"
#include "clang/Basic/CodeGenOptions.h"
#include "clang/Basic/TargetInfo.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/LLVMContext.h"
Expand Down Expand Up @@ -319,7 +320,13 @@ CodeGenTBAA::CollectFields(uint64_t BaseOffset,
// base type.
if ((*i)->isBitField()) {
const CGBitFieldInfo &Info = CGRL.getBitFieldInfo(*i);
if (Info.Offset != 0)
// For big endian targets the first bitfield in the consecutive run is
// at the most-significant end; see CGRecordLowering::setBitFieldInfo
// for more information.
bool IsBE = Context.getTargetInfo().isBigEndian();
bool IsFirst = IsBE ? Info.StorageSize - (Info.Offset + Info.Size) == 0
: Info.Offset == 0;
if (!IsFirst)
continue;
unsigned CurrentBitFieldSize = Info.StorageSize;
uint64_t Size =
Expand Down
10 changes: 3 additions & 7 deletions clang/test/CodeGen/tbaa-struct-bitfield-endianness.cpp
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@@ -1,13 +1,10 @@
// RUN: %clang_cc1 -triple aarch64_be-apple-darwin -emit-llvm -o - -O1 %s | \
// RUN: FileCheck -check-prefixes=CHECK,CHECK-BE %s
// RUN: FileCheck -check-prefixes=CHECK %s
// RUN: %clang_cc1 -triple aarch64-apple-darwin -emit-llvm -o - -O1 %s | \
// RUN: FileCheck -check-prefixes=CHECK,CHECK-LE %s
// RUN: FileCheck -check-prefixes=CHECK %s
//
// Check that TBAA metadata for structs containing bitfields is
// consistent between big and little endian layouts.
//
// FIXME: The metadata below is invalid for the big endian layout: the
// start offset of 2 is incorrect.

struct NamedBitfields {
int f1 : 8;
Expand All @@ -28,8 +25,7 @@ void copy(NamedBitfields *a1, NamedBitfields *a2) {
*a1 = *a2;
}

// CHECK-BE: [[TBAA_STRUCT2]] = !{i64 2, i64 4, [[META3:![0-9]+]], i64 4, i64 4, [[META6:![0-9]+]], i64 8, i64 8, [[META8:![0-9]+]]}
// CHECK-LE: [[TBAA_STRUCT2]] = !{i64 0, i64 4, [[META3:![0-9]+]], i64 4, i64 4, [[META6:![0-9]+]], i64 8, i64 8, [[META8:![0-9]+]]}
// CHECK: [[TBAA_STRUCT2]] = !{i64 0, i64 4, [[META3:![0-9]+]], i64 4, i64 4, [[META6:![0-9]+]], i64 8, i64 8, [[META8:![0-9]+]]}
// CHECK: [[META3]] = !{[[META4:![0-9]+]], [[META4]], i64 0}
// CHECK: [[META4]] = !{!"omnipotent char", [[META5:![0-9]+]], i64 0}
// CHECK: [[META5]] = !{!"Simple C++ TBAA"}
Expand Down