Revert "[clang][CodeGen] Zero init unspecified fields in initializers in C" #109898
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… in C (#…" This reverts commit 7a086e1.
llvmbot
added
clang
|
@llvm/pr-subscribers-clang Author: Eli Friedman (efriedma-quic) ChangesReverts llvm/llvm-project#97121 Causing failures on LNT bots; log shows a crash in ConstStructBuilder::BuildStruct. Patch is 56.41 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/109898.diff 23 Files Affected:
diff --git a/clang/docs/LanguageExtensions.rst b/clang/docs/LanguageExtensions.rst
index f4be97047422fa..0c6b9b1b8f9ce4 100644
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -5860,26 +5860,3 @@ specify the starting offset to begin embedding from. The resources is treated
as being empty if the specified offset is larger than the number of bytes in
the resource. The offset will be applied *before* any ``limit`` parameters are
applied.
-
-Union and aggregate initialization in C
-=======================================
-
-In C23 (N2900), when an object is initialized from initializer ``= {}``, all
-elements of arrays, all members of structs, and the first members of unions are
-empty-initialized recursively. In addition, all padding bits are initialized to
-zero.
-
-Clang guarantees the following behaviors:
-
-* ``1:`` Clang supports initializer ``= {}`` mentioned above in all C
- standards.
-
-* ``2:`` When unions are initialized from initializer ``= {}``, bytes outside
- of the first members of unions are also initialized to zero.
-
-* ``3:`` When unions, structures and arrays are initialized from initializer
- ``= { initializer-list }``, all members not explicitly initialized in
- the initializer list are empty-initialized recursively. In addition, all
- padding bits are initialized to zero.
-
-Currently, the above extension only applies to C source code, not C++.
diff --git a/clang/lib/CodeGen/CGExprAgg.cpp b/clang/lib/CodeGen/CGExprAgg.cpp
index 43f3bcc95fe767..bbfc6672ecc25a 100644
--- a/clang/lib/CodeGen/CGExprAgg.cpp
+++ b/clang/lib/CodeGen/CGExprAgg.cpp
@@ -1698,17 +1698,6 @@ void AggExprEmitter::VisitCXXParenListOrInitListExpr(
// Prepare a 'this' for CXXDefaultInitExprs.
CodeGenFunction::FieldConstructionScope FCS(CGF, Dest.getAddress());
- const bool ZeroInitPadding =
- CGF.CGM.shouldZeroInitPadding() && !Dest.isZeroed();
- const Address BaseLoc = Dest.getAddress().withElementType(CGF.Int8Ty);
- auto DoZeroInitPadding = [&](CharUnits Offset, CharUnits Size) {
- if (Size.isPositive()) {
- Address Loc = CGF.Builder.CreateConstGEP(BaseLoc, Offset.getQuantity());
- llvm::Constant *SizeVal = CGF.Builder.getInt64(Size.getQuantity());
- CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal, false);
- }
- };
-
if (record->isUnion()) {
// Only initialize one field of a union. The field itself is
// specified by the initializer list.
@@ -1733,37 +1722,17 @@ void AggExprEmitter::VisitCXXParenListOrInitListExpr(
if (NumInitElements) {
// Store the initializer into the field
EmitInitializationToLValue(InitExprs[0], FieldLoc);
- if (ZeroInitPadding) {
- CharUnits TotalSize =
- Dest.getPreferredSize(CGF.getContext(), DestLV.getType());
- CharUnits FieldSize =
- CGF.getContext().getTypeSizeInChars(FieldLoc.getType());
- DoZeroInitPadding(FieldSize, TotalSize - FieldSize);
- }
} else {
// Default-initialize to null.
- if (ZeroInitPadding)
- EmitNullInitializationToLValue(DestLV);
- else
- EmitNullInitializationToLValue(FieldLoc);
+ EmitNullInitializationToLValue(FieldLoc);
}
+
return;
}
// Here we iterate over the fields; this makes it simpler to both
// default-initialize fields and skip over unnamed fields.
- const ASTRecordLayout &Layout = CGF.getContext().getASTRecordLayout(record);
- CharUnits SizeSoFar = CharUnits::Zero();
for (const auto *field : record->fields()) {
- if (ZeroInitPadding) {
- unsigned FieldNo = field->getFieldIndex();
- CharUnits Offset =
- CGF.getContext().toCharUnitsFromBits(Layout.getFieldOffset(FieldNo));
- DoZeroInitPadding(SizeSoFar, Offset - SizeSoFar);
- CharUnits FieldSize =
- CGF.getContext().getTypeSizeInChars(field->getType());
- SizeSoFar = Offset + FieldSize;
- }
// We're done once we hit the flexible array member.
if (field->getType()->isIncompleteArrayType())
break;
@@ -1805,11 +1774,6 @@ void AggExprEmitter::VisitCXXParenListOrInitListExpr(
}
}
}
- if (ZeroInitPadding) {
- CharUnits TotalSize =
- Dest.getPreferredSize(CGF.getContext(), DestLV.getType());
- DoZeroInitPadding(SizeSoFar, TotalSize - SizeSoFar);
- }
}
void AggExprEmitter::VisitArrayInitLoopExpr(const ArrayInitLoopExpr *E,
diff --git a/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp
index 66bc0640b632aa..dd65080a840446 100644
--- a/clang/lib/CodeGen/CGExprConstant.cpp
+++ b/clang/lib/CodeGen/CGExprConstant.cpp
@@ -42,16 +42,6 @@ using namespace CodeGen;
namespace {
class ConstExprEmitter;
-llvm::Constant *getPadding(const CodeGenModule &CGM, CharUnits PadSize) {
- llvm::Type *Ty = CGM.CharTy;
- if (PadSize > CharUnits::One())
- Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity());
- if (CGM.shouldZeroInitPadding()) {
- return llvm::Constant::getNullValue(Ty);
- }
- return llvm::UndefValue::get(Ty);
-}
-
struct ConstantAggregateBuilderUtils {
CodeGenModule &CGM;
@@ -71,7 +61,10 @@ struct ConstantAggregateBuilderUtils {
}
llvm::Constant *getPadding(CharUnits PadSize) const {
- return ::getPadding(CGM, PadSize);
+ llvm::Type *Ty = CGM.CharTy;
+ if (PadSize > CharUnits::One())
+ Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity());
+ return llvm::UndefValue::get(Ty);
}
llvm::Constant *getZeroes(CharUnits ZeroSize) const {
@@ -598,11 +591,6 @@ class ConstStructBuilder {
bool Build(const InitListExpr *ILE, bool AllowOverwrite);
bool Build(const APValue &Val, const RecordDecl *RD, bool IsPrimaryBase,
const CXXRecordDecl *VTableClass, CharUnits BaseOffset);
- bool DoZeroInitPadding(const ASTRecordLayout &Layout, unsigned FieldNo,
- const FieldDecl &Field, bool AllowOverwrite,
- CharUnits &FieldSize, CharUnits &SizeSoFar);
- bool DoZeroInitPadding(const ASTRecordLayout &Layout, bool AllowOverwrite,
- CharUnits &SizeSoFar);
llvm::Constant *Finalize(QualType Ty);
};
@@ -727,10 +715,6 @@ bool ConstStructBuilder::Build(const InitListExpr *ILE, bool AllowOverwrite) {
if (CXXRD->getNumBases())
return false;
- const bool ZeroInitPadding = CGM.shouldZeroInitPadding();
- CharUnits FieldSize = CharUnits::Zero();
- CharUnits SizeSoFar = CharUnits::Zero();
-
for (FieldDecl *Field : RD->fields()) {
++FieldNo;
@@ -748,13 +732,8 @@ bool ConstStructBuilder::Build(const InitListExpr *ILE, bool AllowOverwrite) {
const Expr *Init = nullptr;
if (ElementNo < ILE->getNumInits())
Init = ILE->getInit(ElementNo++);
- if (isa_and_nonnull<NoInitExpr>(Init)) {
- if (ZeroInitPadding &&
- !DoZeroInitPadding(Layout, FieldNo, *Field, AllowOverwrite, FieldSize,
- SizeSoFar))
- return false;
+ if (isa_and_nonnull<NoInitExpr>(Init))
continue;
- }
// Zero-sized fields are not emitted, but their initializers may still
// prevent emission of this struct as a constant.
@@ -764,11 +743,6 @@ bool ConstStructBuilder::Build(const InitListExpr *ILE, bool AllowOverwrite) {
continue;
}
- if (ZeroInitPadding &&
- !DoZeroInitPadding(Layout, FieldNo, *Field, AllowOverwrite, FieldSize,
- SizeSoFar))
- return false;
-
// When emitting a DesignatedInitUpdateExpr, a nested InitListExpr
// represents additional overwriting of our current constant value, and not
// a new constant to emit independently.
@@ -794,10 +768,6 @@ bool ConstStructBuilder::Build(const InitListExpr *ILE, bool AllowOverwrite) {
if (!EltInit)
return false;
- if (ZeroInitPadding && FieldSize.isZero())
- SizeSoFar += CharUnits::fromQuantity(
- CGM.getDataLayout().getTypeAllocSize(EltInit->getType()));
-
if (!Field->isBitField()) {
// Handle non-bitfield members.
if (!AppendField(Field, Layout.getFieldOffset(FieldNo), EltInit,
@@ -815,9 +785,6 @@ bool ConstStructBuilder::Build(const InitListExpr *ILE, bool AllowOverwrite) {
}
}
- if (ZeroInitPadding && !DoZeroInitPadding(Layout, AllowOverwrite, SizeSoFar))
- return false;
-
return true;
}
@@ -882,9 +849,6 @@ bool ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD,
unsigned FieldNo = 0;
uint64_t OffsetBits = CGM.getContext().toBits(Offset);
- const bool ZeroInitPadding = CGM.shouldZeroInitPadding();
- CharUnits FieldSize = CharUnits::Zero();
- CharUnits SizeSoFar = CharUnits::Zero();
bool AllowOverwrite = false;
for (RecordDecl::field_iterator Field = RD->field_begin(),
@@ -906,15 +870,6 @@ bool ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD,
if (!EltInit)
return false;
- if (ZeroInitPadding) {
- if (!DoZeroInitPadding(Layout, FieldNo, **Field, AllowOverwrite,
- FieldSize, SizeSoFar))
- return false;
- if (FieldSize.isZero())
- SizeSoFar += CharUnits::fromQuantity(
- CGM.getDataLayout().getTypeAllocSize(EltInit->getType()));
- }
-
if (!Field->isBitField()) {
// Handle non-bitfield members.
if (!AppendField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits,
@@ -931,35 +886,7 @@ bool ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD,
return false;
}
}
- if (ZeroInitPadding && !DoZeroInitPadding(Layout, AllowOverwrite, SizeSoFar))
- return false;
-
- return true;
-}
-bool ConstStructBuilder::DoZeroInitPadding(
- const ASTRecordLayout &Layout, unsigned FieldNo, const FieldDecl &Field,
- bool AllowOverwrite, CharUnits &FieldSize, CharUnits &SizeSoFar) {
- CharUnits Offset =
- CGM.getContext().toCharUnitsFromBits(Layout.getFieldOffset(FieldNo));
- if (SizeSoFar < Offset)
- if (!AppendBytes(SizeSoFar, getPadding(CGM, Offset - SizeSoFar),
- AllowOverwrite))
- return false;
- FieldSize = CGM.getContext().getTypeSizeInChars(Field.getType());
- SizeSoFar = Offset + FieldSize;
- return true;
-}
-
-bool ConstStructBuilder::DoZeroInitPadding(const ASTRecordLayout &Layout,
- bool AllowOverwrite,
- CharUnits &SizeSoFar) {
- CharUnits TotalSize = Layout.getSize();
- if (SizeSoFar < TotalSize)
- if (!AppendBytes(SizeSoFar, getPadding(CGM, TotalSize - SizeSoFar),
- AllowOverwrite))
- return false;
- SizeSoFar = TotalSize;
return true;
}
@@ -1200,10 +1127,12 @@ class ConstExprEmitter
assert(CurSize <= TotalSize && "Union size mismatch!");
if (unsigned NumPadBytes = TotalSize - CurSize) {
- llvm::Constant *Padding =
- getPadding(CGM, CharUnits::fromQuantity(NumPadBytes));
- Elts.push_back(Padding);
- Types.push_back(Padding->getType());
+ llvm::Type *Ty = CGM.CharTy;
+ if (NumPadBytes > 1)
+ Ty = llvm::ArrayType::get(Ty, NumPadBytes);
+
+ Elts.push_back(llvm::UndefValue::get(Ty));
+ Types.push_back(Ty);
}
llvm::StructType *STy = llvm::StructType::get(VMContext, Types, false);
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index fcdfef03088da5..c58bb88035ca8a 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -1676,57 +1676,6 @@ class CodeGenModule : public CodeGenTypeCache {
MustTailCallUndefinedGlobals.insert(Global);
}
- bool shouldZeroInitPadding() const {
- // In C23 (N3096) $6.7.10:
- // """
- // If any object is initialized with an empty iniitializer, then it is
- // subject to default initialization:
- // - if it is an aggregate, every member is initialized (recursively)
- // according to these rules, and any padding is initialized to zero bits;
- // - if it is a union, the first named member is initialized (recursively)
- // according to these rules, and any padding is initialized to zero bits.
- //
- // If the aggregate or union contains elements or members that are
- // aggregates or unions, these rules apply recursively to the subaggregates
- // or contained unions.
- //
- // If there are fewer initializers in a brace-enclosed list than there are
- // elements or members of an aggregate, or fewer characters in a string
- // literal used to initialize an array of known size than there are elements
- // in the array, the remainder of the aggregate is subject to default
- // initialization.
- // """
- //
- // From my understanding, the standard is ambiguous in the following two
- // areas:
- // 1. For a union type with empty initializer, if the first named member is
- // not the largest member, then the bytes comes after the first named member
- // but before padding are left unspecified. An example is:
- // union U { int a; long long b;};
- // union U u = {}; // The first 4 bytes are 0, but 4-8 bytes are left
- // unspecified.
- //
- // 2. It only mentions padding for empty initializer, but doesn't mention
- // padding for a non empty initialization list. And if the aggregation or
- // union contains elements or members that are aggregates or unions, and
- // some are non empty initializers, while others are empty initiailizers,
- // the padding initialization is unclear. An example is:
- // struct S1 { int a; long long b; };
- // struct S2 { char c; struct S1 s1; };
- // // The values for paddings between s2.c and s2.s1.a, between s2.s1.a
- // and s2.s1.b are unclear.
- // struct S2 s2 = { 'c' };
- //
- // Here we choose to zero initiailize left bytes of a union type. Because
- // projects like the Linux kernel are relying on this behavior. If we don't
- // explicitly zero initialize them, the undef values can be optimized to
- // return gabage data. We also choose to zero initialize paddings for
- // aggregates and unions, no matter they are initialized by empty
- // initializers or non empty initializers. This can provide a consistent
- // behavior. So projects like the Linux kernel can rely on it.
- return !getLangOpts().CPlusPlus;
- }
-
private:
bool shouldDropDLLAttribute(const Decl *D, const llvm::GlobalValue *GV) const;
diff --git a/clang/test/CodeGen/2008-07-22-bitfield-init-after-zero-len-array.c b/clang/test/CodeGen/2008-07-22-bitfield-init-after-zero-len-array.c
index b639734ef5d4b7..b72d689659e602 100644
--- a/clang/test/CodeGen/2008-07-22-bitfield-init-after-zero-len-array.c
+++ b/clang/test/CodeGen/2008-07-22-bitfield-init-after-zero-len-array.c
@@ -8,4 +8,4 @@ struct et7 {
52,
};
-// CHECK: @yv7 ={{.*}} global { [0 x float], i8, [3 x i8] } { [0 x float] zeroinitializer, i8 52, [3 x i8] zeroinitializer }
+// CHECK: @yv7 ={{.*}} global %struct.et7 { [0 x float] zeroinitializer, i8 52 }
diff --git a/clang/test/CodeGen/2008-08-07-AlignPadding1.c b/clang/test/CodeGen/2008-08-07-AlignPadding1.c
index d69cbc22cc1dfb..17e88ce02659f0 100644
--- a/clang/test/CodeGen/2008-08-07-AlignPadding1.c
+++ b/clang/test/CodeGen/2008-08-07-AlignPadding1.c
@@ -20,9 +20,9 @@ struct gc_generation {
#define GEN_HEAD(n) (&generations[n].head)
-// The idea is that there are 6 zeroinitializers in this structure initializer to cover
+// The idea is that there are 6 undefs in this structure initializer to cover
// the padding between elements.
-// CHECK: @generations ={{.*}} global [3 x %struct.gc_generation] [%struct.gc_generation { %union._gc_head { %struct.anon { ptr @generations, ptr @generations, i64 0 }, [8 x i8] zeroinitializer }, i32 700, i32 0, [8 x i8] zeroinitializer }, %struct.gc_generation { %union._gc_head { %struct.anon { ptr getelementptr (i8, ptr @generations, i64 48), ptr getelementptr (i8, ptr @generations, i64 48), i64 0 }, [8 x i8] zeroinitializer }, i32 10, i32 0, [8 x i8] zeroinitializer }, %struct.gc_generation { %union._gc_head { %struct.anon { ptr getelementptr (i8, ptr @generations, i64 96), ptr getelementptr (i8, ptr @generations, i64 96), i64 0 }, [8 x i8] zeroinitializer }, i32 10, i32 0, [8 x i8] zeroinitializer }]
+// CHECK: @generations ={{.*}} global [3 x %struct.gc_generation] [%struct.gc_generation { %union._gc_head { %struct.anon { ptr @generations, ptr @generations, i64 0 }, [8 x i8] undef }, i32 700, i32 0, [8 x i8] undef }, %struct.gc_generation { %union._gc_head { %struct.anon { ptr getelementptr (i8, ptr @generations, i64 48), ptr getelementptr (i8, ptr @generations, i64 48), i64 0 }, [8 x i8] undef }, i32 10, i32 0, [8 x i8] undef }, %struct.gc_generation { %union._gc_head { %struct.anon { ptr getelementptr (i8, ptr @generations, i64 96), ptr getelementptr (i8, ptr @generations, i64 96), i64 0 }, [8 x i8] undef }, i32 10, i32 0, [8 x i8] undef }]
/* linked lists of container objects */
struct gc_generation generations[3] = {
/* PyGC_Head, threshold, count */
diff --git a/clang/test/CodeGen/2009-06-14-anonymous-union-init.c b/clang/test/CodeGen/2009-06-14-anonymous-union-init.c
index a4375d7868f01d..13f6357f7966d9 100644
--- a/clang/test/CodeGen/2009-06-14-anonymous-union-init.c
+++ b/clang/test/CodeGen/2009-06-14-anonymous-union-init.c
@@ -7,7 +7,7 @@ struct sysfs_dirent {
};
struct sysfs_dirent sysfs_root = { {}, 16877 };
-// CHECK: @sysfs_root = {{.*}}global { %union.anon, i16, [2 x i8] } { %union.anon zeroinitializer, i16 16877, [2 x i8] zeroinitializer }
+// CHECK: @sysfs_root = {{.*}}global %struct.sysfs_dirent { %union.anon zeroinitializer, i16 16877 }
struct Foo {
union { struct empty {} x; };
@@ -16,4 +16,4 @@ struct Foo {
struct Foo foo = { {}, 16877 };
// EMPTY: @foo = {{.*}}global %struct.Foo { i16 16877 }
-// EMPTY-MSVC: @foo = {{.*}}global %struct.Foo { [4 x i8] zeroinitializer, i16 16877 }
+// EMPTY-MSVC: @foo = {{.*}}global %struct.Foo { [4 x i8] undef, i16 16877 }
diff --git a/clang/test/CodeGen/64bit-swiftcall.c b/clang/test/CodeGen/64bit-swiftcall.c
index 7f8aa02d97ce1f..7af65ccf556a81 100644
--- a/clang/test/CodeGen/64bit-swiftcall.c
+++ b/clang/test/CodeGen/64bit-swiftcall.c
@@ -14,6 +14,8 @@
// CHECK-DAG: %struct.atomic_padded = type { { %struct.packed, [7 x i8] } }
// CHECK-DAG: %struct.packed = type <{ i64, i8 }>
+//
+// CHECK: [[STRUCT2_RESULT:@.*]] = private {{.*}} constant [[STRUCT2_TYPE:%.*]] { i32 0, i8 0, i8 undef, i8 0, i32 0, i32 0 }
/*****************************************************************************/
/****************************** PARAMETER ABIS *******************************/
@@ -160,8 +162,8 @@ typedef struct {
} struct_2;
TEST(struct_2);
// CHECK-LABEL: define{{.*}} swiftcc { i64, i64 } @return_struct_2() {{.*}}{
-// CHECK: [[RET:%.*]] = alloca [[STRUCT2:%.*]], align 4
-// CHECK: call void @llvm.memset
+// CHECK: [[RET:%.*]] = alloca [[STRUCT2_TYPE]], align 4
+// CHECK: call void @llvm.memcpy{{.*}}({{.*}}[[RET]], {{.*}}[[STRUCT2_RESULT]]
// CHECK: [[GEP0:%.*]] = getelementptr inbounds nuw { i64, i64 }, ptr [[RET]], i32 0, i32 0
// CHECK: [[T0:%.*]] = load i64, ptr [[GEP0]], align 4
// CHECK: [[GEP1:%.*]] = getelementptr inbounds nuw { i64, i64 }, ptr [[RET]], i32 0, i32 1
@@ -171,7 +173,7 @@ TEST(struct_2);
// CHECK: ret { i64, i64 } [[R1]]
// CHECK: }
// CHECK-LABEL: define{{.*}} swiftcc void @take_struct_2(i64 %0, i64 %1) {{.*}}{
-// CHECK: [[V:%.*]] = alloca [[STRUCT2]], align 4
+// CHECK: [[V:%.*]] = alloca [[STRUCT:%.*]], align 4
// CHECK: [[GEP0:%.*]] = getelementptr inbounds nuw { i64, i64 }, ptr [[V]], i32 0, i32 0
// CHECK: store i64 %0, ptr [[GEP0]], align 4
// CHECK: [[GEP1:%.*]] = getelementptr inbounds nuw { i64, i64 }, ptr [[V]], i32 0, i32 1
@@ -179,7 +181,7 @@ TEST(struct_2);
// CHECK: ret void
// CHECK: }
// CHECK-LABEL: define{{.*}} void @test_struct_2() {{.*}} {
-// CHECK: [[TMP:%.*]] = alloca [[STRUCT2]], align 4
+// CHECK: [[TMP:%.*]] = alloca [[STRUCT2_TYPE]], align 4
// CHECK: [[CALL:%.*]] = call swiftcc { i64, i64 } @return_struct_2()
// CHECK: [[GEP:%.*]] = getelementptr inbounds nuw {{.*}} [[TMP]], i32 0, i32 0
// CHECK: [[T0:%.*]] = extractvalue { i64, i64 } [[CALL]], 0
@@ -252,7 +254,7 @@ typedef union {
TEST(union_het_fp)...
[truncated]
|
|
@llvm/pr-subscribers-clang-codegen Author: Eli Friedman (efriedma-quic) ChangesReverts llvm/llvm-project#97121 Causing failures on LNT bots; log shows a crash in ConstStructBuilder::BuildStruct. Patch is 56.41 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/109898.diff 23 Files Affected:
diff --git a/clang/docs/LanguageExtensions.rst b/clang/docs/LanguageExtensions.rst
index f4be97047422fa..0c6b9b1b8f9ce4 100644
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -5860,26 +5860,3 @@ specify the starting offset to begin embedding from. The resources is treated
as being empty if the specified offset is larger than the number of bytes in
the resource. The offset will be applied *before* any ``limit`` parameters are
applied.
-
-Union and aggregate initialization in C
-=======================================
-
-In C23 (N2900), when an object is initialized from initializer ``= {}``, all
-elements of arrays, all members of structs, and the first members of unions are
-empty-initialized recursively. In addition, all padding bits are initialized to
-zero.
-
-Clang guarantees the following behaviors:
-
-* ``1:`` Clang supports initializer ``= {}`` mentioned above in all C
- standards.
-
-* ``2:`` When unions are initialized from initializer ``= {}``, bytes outside
- of the first members of unions are also initialized to zero.
-
-* ``3:`` When unions, structures and arrays are initialized from initializer
- ``= { initializer-list }``, all members not explicitly initialized in
- the initializer list are empty-initialized recursively. In addition, all
- padding bits are initialized to zero.
-
-Currently, the above extension only applies to C source code, not C++.
diff --git a/clang/lib/CodeGen/CGExprAgg.cpp b/clang/lib/CodeGen/CGExprAgg.cpp
index 43f3bcc95fe767..bbfc6672ecc25a 100644
--- a/clang/lib/CodeGen/CGExprAgg.cpp
+++ b/clang/lib/CodeGen/CGExprAgg.cpp
@@ -1698,17 +1698,6 @@ void AggExprEmitter::VisitCXXParenListOrInitListExpr(
// Prepare a 'this' for CXXDefaultInitExprs.
CodeGenFunction::FieldConstructionScope FCS(CGF, Dest.getAddress());
- const bool ZeroInitPadding =
- CGF.CGM.shouldZeroInitPadding() && !Dest.isZeroed();
- const Address BaseLoc = Dest.getAddress().withElementType(CGF.Int8Ty);
- auto DoZeroInitPadding = [&](CharUnits Offset, CharUnits Size) {
- if (Size.isPositive()) {
- Address Loc = CGF.Builder.CreateConstGEP(BaseLoc, Offset.getQuantity());
- llvm::Constant *SizeVal = CGF.Builder.getInt64(Size.getQuantity());
- CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal, false);
- }
- };
-
if (record->isUnion()) {
// Only initialize one field of a union. The field itself is
// specified by the initializer list.
@@ -1733,37 +1722,17 @@ void AggExprEmitter::VisitCXXParenListOrInitListExpr(
if (NumInitElements) {
// Store the initializer into the field
EmitInitializationToLValue(InitExprs[0], FieldLoc);
- if (ZeroInitPadding) {
- CharUnits TotalSize =
- Dest.getPreferredSize(CGF.getContext(), DestLV.getType());
- CharUnits FieldSize =
- CGF.getContext().getTypeSizeInChars(FieldLoc.getType());
- DoZeroInitPadding(FieldSize, TotalSize - FieldSize);
- }
} else {
// Default-initialize to null.
- if (ZeroInitPadding)
- EmitNullInitializationToLValue(DestLV);
- else
- EmitNullInitializationToLValue(FieldLoc);
+ EmitNullInitializationToLValue(FieldLoc);
}
+
return;
}
// Here we iterate over the fields; this makes it simpler to both
// default-initialize fields and skip over unnamed fields.
- const ASTRecordLayout &Layout = CGF.getContext().getASTRecordLayout(record);
- CharUnits SizeSoFar = CharUnits::Zero();
for (const auto *field : record->fields()) {
- if (ZeroInitPadding) {
- unsigned FieldNo = field->getFieldIndex();
- CharUnits Offset =
- CGF.getContext().toCharUnitsFromBits(Layout.getFieldOffset(FieldNo));
- DoZeroInitPadding(SizeSoFar, Offset - SizeSoFar);
- CharUnits FieldSize =
- CGF.getContext().getTypeSizeInChars(field->getType());
- SizeSoFar = Offset + FieldSize;
- }
// We're done once we hit the flexible array member.
if (field->getType()->isIncompleteArrayType())
break;
@@ -1805,11 +1774,6 @@ void AggExprEmitter::VisitCXXParenListOrInitListExpr(
}
}
}
- if (ZeroInitPadding) {
- CharUnits TotalSize =
- Dest.getPreferredSize(CGF.getContext(), DestLV.getType());
- DoZeroInitPadding(SizeSoFar, TotalSize - SizeSoFar);
- }
}
void AggExprEmitter::VisitArrayInitLoopExpr(const ArrayInitLoopExpr *E,
diff --git a/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp
index 66bc0640b632aa..dd65080a840446 100644
--- a/clang/lib/CodeGen/CGExprConstant.cpp
+++ b/clang/lib/CodeGen/CGExprConstant.cpp
@@ -42,16 +42,6 @@ using namespace CodeGen;
namespace {
class ConstExprEmitter;
-llvm::Constant *getPadding(const CodeGenModule &CGM, CharUnits PadSize) {
- llvm::Type *Ty = CGM.CharTy;
- if (PadSize > CharUnits::One())
- Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity());
- if (CGM.shouldZeroInitPadding()) {
- return llvm::Constant::getNullValue(Ty);
- }
- return llvm::UndefValue::get(Ty);
-}
-
struct ConstantAggregateBuilderUtils {
CodeGenModule &CGM;
@@ -71,7 +61,10 @@ struct ConstantAggregateBuilderUtils {
}
llvm::Constant *getPadding(CharUnits PadSize) const {
- return ::getPadding(CGM, PadSize);
+ llvm::Type *Ty = CGM.CharTy;
+ if (PadSize > CharUnits::One())
+ Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity());
+ return llvm::UndefValue::get(Ty);
}
llvm::Constant *getZeroes(CharUnits ZeroSize) const {
@@ -598,11 +591,6 @@ class ConstStructBuilder {
bool Build(const InitListExpr *ILE, bool AllowOverwrite);
bool Build(const APValue &Val, const RecordDecl *RD, bool IsPrimaryBase,
const CXXRecordDecl *VTableClass, CharUnits BaseOffset);
- bool DoZeroInitPadding(const ASTRecordLayout &Layout, unsigned FieldNo,
- const FieldDecl &Field, bool AllowOverwrite,
- CharUnits &FieldSize, CharUnits &SizeSoFar);
- bool DoZeroInitPadding(const ASTRecordLayout &Layout, bool AllowOverwrite,
- CharUnits &SizeSoFar);
llvm::Constant *Finalize(QualType Ty);
};
@@ -727,10 +715,6 @@ bool ConstStructBuilder::Build(const InitListExpr *ILE, bool AllowOverwrite) {
if (CXXRD->getNumBases())
return false;
- const bool ZeroInitPadding = CGM.shouldZeroInitPadding();
- CharUnits FieldSize = CharUnits::Zero();
- CharUnits SizeSoFar = CharUnits::Zero();
-
for (FieldDecl *Field : RD->fields()) {
++FieldNo;
@@ -748,13 +732,8 @@ bool ConstStructBuilder::Build(const InitListExpr *ILE, bool AllowOverwrite) {
const Expr *Init = nullptr;
if (ElementNo < ILE->getNumInits())
Init = ILE->getInit(ElementNo++);
- if (isa_and_nonnull<NoInitExpr>(Init)) {
- if (ZeroInitPadding &&
- !DoZeroInitPadding(Layout, FieldNo, *Field, AllowOverwrite, FieldSize,
- SizeSoFar))
- return false;
+ if (isa_and_nonnull<NoInitExpr>(Init))
continue;
- }
// Zero-sized fields are not emitted, but their initializers may still
// prevent emission of this struct as a constant.
@@ -764,11 +743,6 @@ bool ConstStructBuilder::Build(const InitListExpr *ILE, bool AllowOverwrite) {
continue;
}
- if (ZeroInitPadding &&
- !DoZeroInitPadding(Layout, FieldNo, *Field, AllowOverwrite, FieldSize,
- SizeSoFar))
- return false;
-
// When emitting a DesignatedInitUpdateExpr, a nested InitListExpr
// represents additional overwriting of our current constant value, and not
// a new constant to emit independently.
@@ -794,10 +768,6 @@ bool ConstStructBuilder::Build(const InitListExpr *ILE, bool AllowOverwrite) {
if (!EltInit)
return false;
- if (ZeroInitPadding && FieldSize.isZero())
- SizeSoFar += CharUnits::fromQuantity(
- CGM.getDataLayout().getTypeAllocSize(EltInit->getType()));
-
if (!Field->isBitField()) {
// Handle non-bitfield members.
if (!AppendField(Field, Layout.getFieldOffset(FieldNo), EltInit,
@@ -815,9 +785,6 @@ bool ConstStructBuilder::Build(const InitListExpr *ILE, bool AllowOverwrite) {
}
}
- if (ZeroInitPadding && !DoZeroInitPadding(Layout, AllowOverwrite, SizeSoFar))
- return false;
-
return true;
}
@@ -882,9 +849,6 @@ bool ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD,
unsigned FieldNo = 0;
uint64_t OffsetBits = CGM.getContext().toBits(Offset);
- const bool ZeroInitPadding = CGM.shouldZeroInitPadding();
- CharUnits FieldSize = CharUnits::Zero();
- CharUnits SizeSoFar = CharUnits::Zero();
bool AllowOverwrite = false;
for (RecordDecl::field_iterator Field = RD->field_begin(),
@@ -906,15 +870,6 @@ bool ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD,
if (!EltInit)
return false;
- if (ZeroInitPadding) {
- if (!DoZeroInitPadding(Layout, FieldNo, **Field, AllowOverwrite,
- FieldSize, SizeSoFar))
- return false;
- if (FieldSize.isZero())
- SizeSoFar += CharUnits::fromQuantity(
- CGM.getDataLayout().getTypeAllocSize(EltInit->getType()));
- }
-
if (!Field->isBitField()) {
// Handle non-bitfield members.
if (!AppendField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits,
@@ -931,35 +886,7 @@ bool ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD,
return false;
}
}
- if (ZeroInitPadding && !DoZeroInitPadding(Layout, AllowOverwrite, SizeSoFar))
- return false;
-
- return true;
-}
-bool ConstStructBuilder::DoZeroInitPadding(
- const ASTRecordLayout &Layout, unsigned FieldNo, const FieldDecl &Field,
- bool AllowOverwrite, CharUnits &FieldSize, CharUnits &SizeSoFar) {
- CharUnits Offset =
- CGM.getContext().toCharUnitsFromBits(Layout.getFieldOffset(FieldNo));
- if (SizeSoFar < Offset)
- if (!AppendBytes(SizeSoFar, getPadding(CGM, Offset - SizeSoFar),
- AllowOverwrite))
- return false;
- FieldSize = CGM.getContext().getTypeSizeInChars(Field.getType());
- SizeSoFar = Offset + FieldSize;
- return true;
-}
-
-bool ConstStructBuilder::DoZeroInitPadding(const ASTRecordLayout &Layout,
- bool AllowOverwrite,
- CharUnits &SizeSoFar) {
- CharUnits TotalSize = Layout.getSize();
- if (SizeSoFar < TotalSize)
- if (!AppendBytes(SizeSoFar, getPadding(CGM, TotalSize - SizeSoFar),
- AllowOverwrite))
- return false;
- SizeSoFar = TotalSize;
return true;
}
@@ -1200,10 +1127,12 @@ class ConstExprEmitter
assert(CurSize <= TotalSize && "Union size mismatch!");
if (unsigned NumPadBytes = TotalSize - CurSize) {
- llvm::Constant *Padding =
- getPadding(CGM, CharUnits::fromQuantity(NumPadBytes));
- Elts.push_back(Padding);
- Types.push_back(Padding->getType());
+ llvm::Type *Ty = CGM.CharTy;
+ if (NumPadBytes > 1)
+ Ty = llvm::ArrayType::get(Ty, NumPadBytes);
+
+ Elts.push_back(llvm::UndefValue::get(Ty));
+ Types.push_back(Ty);
}
llvm::StructType *STy = llvm::StructType::get(VMContext, Types, false);
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index fcdfef03088da5..c58bb88035ca8a 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -1676,57 +1676,6 @@ class CodeGenModule : public CodeGenTypeCache {
MustTailCallUndefinedGlobals.insert(Global);
}
- bool shouldZeroInitPadding() const {
- // In C23 (N3096) $6.7.10:
- // """
- // If any object is initialized with an empty iniitializer, then it is
- // subject to default initialization:
- // - if it is an aggregate, every member is initialized (recursively)
- // according to these rules, and any padding is initialized to zero bits;
- // - if it is a union, the first named member is initialized (recursively)
- // according to these rules, and any padding is initialized to zero bits.
- //
- // If the aggregate or union contains elements or members that are
- // aggregates or unions, these rules apply recursively to the subaggregates
- // or contained unions.
- //
- // If there are fewer initializers in a brace-enclosed list than there are
- // elements or members of an aggregate, or fewer characters in a string
- // literal used to initialize an array of known size than there are elements
- // in the array, the remainder of the aggregate is subject to default
- // initialization.
- // """
- //
- // From my understanding, the standard is ambiguous in the following two
- // areas:
- // 1. For a union type with empty initializer, if the first named member is
- // not the largest member, then the bytes comes after the first named member
- // but before padding are left unspecified. An example is:
- // union U { int a; long long b;};
- // union U u = {}; // The first 4 bytes are 0, but 4-8 bytes are left
- // unspecified.
- //
- // 2. It only mentions padding for empty initializer, but doesn't mention
- // padding for a non empty initialization list. And if the aggregation or
- // union contains elements or members that are aggregates or unions, and
- // some are non empty initializers, while others are empty initiailizers,
- // the padding initialization is unclear. An example is:
- // struct S1 { int a; long long b; };
- // struct S2 { char c; struct S1 s1; };
- // // The values for paddings between s2.c and s2.s1.a, between s2.s1.a
- // and s2.s1.b are unclear.
- // struct S2 s2 = { 'c' };
- //
- // Here we choose to zero initiailize left bytes of a union type. Because
- // projects like the Linux kernel are relying on this behavior. If we don't
- // explicitly zero initialize them, the undef values can be optimized to
- // return gabage data. We also choose to zero initialize paddings for
- // aggregates and unions, no matter they are initialized by empty
- // initializers or non empty initializers. This can provide a consistent
- // behavior. So projects like the Linux kernel can rely on it.
- return !getLangOpts().CPlusPlus;
- }
-
private:
bool shouldDropDLLAttribute(const Decl *D, const llvm::GlobalValue *GV) const;
diff --git a/clang/test/CodeGen/2008-07-22-bitfield-init-after-zero-len-array.c b/clang/test/CodeGen/2008-07-22-bitfield-init-after-zero-len-array.c
index b639734ef5d4b7..b72d689659e602 100644
--- a/clang/test/CodeGen/2008-07-22-bitfield-init-after-zero-len-array.c
+++ b/clang/test/CodeGen/2008-07-22-bitfield-init-after-zero-len-array.c
@@ -8,4 +8,4 @@ struct et7 {
52,
};
-// CHECK: @yv7 ={{.*}} global { [0 x float], i8, [3 x i8] } { [0 x float] zeroinitializer, i8 52, [3 x i8] zeroinitializer }
+// CHECK: @yv7 ={{.*}} global %struct.et7 { [0 x float] zeroinitializer, i8 52 }
diff --git a/clang/test/CodeGen/2008-08-07-AlignPadding1.c b/clang/test/CodeGen/2008-08-07-AlignPadding1.c
index d69cbc22cc1dfb..17e88ce02659f0 100644
--- a/clang/test/CodeGen/2008-08-07-AlignPadding1.c
+++ b/clang/test/CodeGen/2008-08-07-AlignPadding1.c
@@ -20,9 +20,9 @@ struct gc_generation {
#define GEN_HEAD(n) (&generations[n].head)
-// The idea is that there are 6 zeroinitializers in this structure initializer to cover
+// The idea is that there are 6 undefs in this structure initializer to cover
// the padding between elements.
-// CHECK: @generations ={{.*}} global [3 x %struct.gc_generation] [%struct.gc_generation { %union._gc_head { %struct.anon { ptr @generations, ptr @generations, i64 0 }, [8 x i8] zeroinitializer }, i32 700, i32 0, [8 x i8] zeroinitializer }, %struct.gc_generation { %union._gc_head { %struct.anon { ptr getelementptr (i8, ptr @generations, i64 48), ptr getelementptr (i8, ptr @generations, i64 48), i64 0 }, [8 x i8] zeroinitializer }, i32 10, i32 0, [8 x i8] zeroinitializer }, %struct.gc_generation { %union._gc_head { %struct.anon { ptr getelementptr (i8, ptr @generations, i64 96), ptr getelementptr (i8, ptr @generations, i64 96), i64 0 }, [8 x i8] zeroinitializer }, i32 10, i32 0, [8 x i8] zeroinitializer }]
+// CHECK: @generations ={{.*}} global [3 x %struct.gc_generation] [%struct.gc_generation { %union._gc_head { %struct.anon { ptr @generations, ptr @generations, i64 0 }, [8 x i8] undef }, i32 700, i32 0, [8 x i8] undef }, %struct.gc_generation { %union._gc_head { %struct.anon { ptr getelementptr (i8, ptr @generations, i64 48), ptr getelementptr (i8, ptr @generations, i64 48), i64 0 }, [8 x i8] undef }, i32 10, i32 0, [8 x i8] undef }, %struct.gc_generation { %union._gc_head { %struct.anon { ptr getelementptr (i8, ptr @generations, i64 96), ptr getelementptr (i8, ptr @generations, i64 96), i64 0 }, [8 x i8] undef }, i32 10, i32 0, [8 x i8] undef }]
/* linked lists of container objects */
struct gc_generation generations[3] = {
/* PyGC_Head, threshold, count */
diff --git a/clang/test/CodeGen/2009-06-14-anonymous-union-init.c b/clang/test/CodeGen/2009-06-14-anonymous-union-init.c
index a4375d7868f01d..13f6357f7966d9 100644
--- a/clang/test/CodeGen/2009-06-14-anonymous-union-init.c
+++ b/clang/test/CodeGen/2009-06-14-anonymous-union-init.c
@@ -7,7 +7,7 @@ struct sysfs_dirent {
};
struct sysfs_dirent sysfs_root = { {}, 16877 };
-// CHECK: @sysfs_root = {{.*}}global { %union.anon, i16, [2 x i8] } { %union.anon zeroinitializer, i16 16877, [2 x i8] zeroinitializer }
+// CHECK: @sysfs_root = {{.*}}global %struct.sysfs_dirent { %union.anon zeroinitializer, i16 16877 }
struct Foo {
union { struct empty {} x; };
@@ -16,4 +16,4 @@ struct Foo {
struct Foo foo = { {}, 16877 };
// EMPTY: @foo = {{.*}}global %struct.Foo { i16 16877 }
-// EMPTY-MSVC: @foo = {{.*}}global %struct.Foo { [4 x i8] zeroinitializer, i16 16877 }
+// EMPTY-MSVC: @foo = {{.*}}global %struct.Foo { [4 x i8] undef, i16 16877 }
diff --git a/clang/test/CodeGen/64bit-swiftcall.c b/clang/test/CodeGen/64bit-swiftcall.c
index 7f8aa02d97ce1f..7af65ccf556a81 100644
--- a/clang/test/CodeGen/64bit-swiftcall.c
+++ b/clang/test/CodeGen/64bit-swiftcall.c
@@ -14,6 +14,8 @@
// CHECK-DAG: %struct.atomic_padded = type { { %struct.packed, [7 x i8] } }
// CHECK-DAG: %struct.packed = type <{ i64, i8 }>
+//
+// CHECK: [[STRUCT2_RESULT:@.*]] = private {{.*}} constant [[STRUCT2_TYPE:%.*]] { i32 0, i8 0, i8 undef, i8 0, i32 0, i32 0 }
/*****************************************************************************/
/****************************** PARAMETER ABIS *******************************/
@@ -160,8 +162,8 @@ typedef struct {
} struct_2;
TEST(struct_2);
// CHECK-LABEL: define{{.*}} swiftcc { i64, i64 } @return_struct_2() {{.*}}{
-// CHECK: [[RET:%.*]] = alloca [[STRUCT2:%.*]], align 4
-// CHECK: call void @llvm.memset
+// CHECK: [[RET:%.*]] = alloca [[STRUCT2_TYPE]], align 4
+// CHECK: call void @llvm.memcpy{{.*}}({{.*}}[[RET]], {{.*}}[[STRUCT2_RESULT]]
// CHECK: [[GEP0:%.*]] = getelementptr inbounds nuw { i64, i64 }, ptr [[RET]], i32 0, i32 0
// CHECK: [[T0:%.*]] = load i64, ptr [[GEP0]], align 4
// CHECK: [[GEP1:%.*]] = getelementptr inbounds nuw { i64, i64 }, ptr [[RET]], i32 0, i32 1
@@ -171,7 +173,7 @@ TEST(struct_2);
// CHECK: ret { i64, i64 } [[R1]]
// CHECK: }
// CHECK-LABEL: define{{.*}} swiftcc void @take_struct_2(i64 %0, i64 %1) {{.*}}{
-// CHECK: [[V:%.*]] = alloca [[STRUCT2]], align 4
+// CHECK: [[V:%.*]] = alloca [[STRUCT:%.*]], align 4
// CHECK: [[GEP0:%.*]] = getelementptr inbounds nuw { i64, i64 }, ptr [[V]], i32 0, i32 0
// CHECK: store i64 %0, ptr [[GEP0]], align 4
// CHECK: [[GEP1:%.*]] = getelementptr inbounds nuw { i64, i64 }, ptr [[V]], i32 0, i32 1
@@ -179,7 +181,7 @@ TEST(struct_2);
// CHECK: ret void
// CHECK: }
// CHECK-LABEL: define{{.*}} void @test_struct_2() {{.*}} {
-// CHECK: [[TMP:%.*]] = alloca [[STRUCT2]], align 4
+// CHECK: [[TMP:%.*]] = alloca [[STRUCT2_TYPE]], align 4
// CHECK: [[CALL:%.*]] = call swiftcc { i64, i64 } @return_struct_2()
// CHECK: [[GEP:%.*]] = getelementptr inbounds nuw {{.*}} [[TMP]], i32 0, i32 0
// CHECK: [[T0:%.*]] = extractvalue { i64, i64 } [[CALL]], 0
@@ -252,7 +254,7 @@ typedef union {
TEST(union_het_fp)...
[truncated]
|
efriedma-quic
deleted the
revert-97121-zero-init-unspecified-fields-in-initializers-in-c
branch
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/59/builds/5542 Here is the relevant piece of the build log for the reference |
|
LGTM One problem I found is for bitfields: The last field takes byte 2-3, while the code thinks it only takes byte 2. The code didn't consider well for fields starting from (or ending with) a (% 8 != 0) bit offset. |
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…s in C" (llvm#109898) This reverts commit d50eaac. Also fixes a bug calculating offsets for bit fields in the original patch.
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… in C" (llvm#109898) Reverts llvm#97121 Causing failures on LNT bots; log shows a crash in ConstStructBuilder::BuildStruct.
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… in C" (llvm#109898) Reverts llvm#97121 Causing failures on LNT bots; log shows a crash in ConstStructBuilder::BuildStruct.
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…s in C" (llvm#109898) (llvm#110051) This reverts commit d50eaac. Also fixes a bug calculating offsets for bit fields in the original patch.
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…s in C" (llvm#109898) (llvm#110051) This reverts commit d50eaac. Also fixes a bug calculating offsets for bit fields in the original patch.
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…s in C" (llvm#109898) (llvm#110051) This reverts commit d50eaac. Also fixes a bug calculating offsets for bit fields in the original patch.
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Reverts #97121
Causing failures on LNT bots; log shows a crash in ConstStructBuilder::BuildStruct.