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[Clang][counted_by] Support casting the array to a different type #136239

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[Clang][counted_by] Support casting the array to a different type #136239

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[Clang][counted_by] Support casting the array to a different type
bwendling Apr 18, 2025
978996d
Reformat
bwendling Apr 18, 2025
58ece35
Merge branch 'llvm:main' into counted-by-with-casts
bwendling Apr 21, 2025
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88 changes: 50 additions & 38 deletions clang/lib/CodeGen/CGBuiltin.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -910,6 +910,7 @@ class StructFieldAccess

public:
const ArraySubscriptExpr *ASE = nullptr;
QualType ArrayElementTy;

const Expr *VisitMemberExpr(const MemberExpr *E) {
if (AddrOfSeen && E->getType()->isArrayType())
Expand All @@ -925,6 +926,7 @@ class StructFieldAccess

AddrOfSeen = false; // '&ptr->array[idx]' is okay.
ASE = E;
ArrayElementTy = E->getBase()->getType();
return Visit(E->getBase());
}
const Expr *VisitCastExpr(const CastExpr *E) {
Expand Down Expand Up @@ -1101,23 +1103,23 @@ CodeGenFunction::emitCountedByMemberSize(const Expr *E, llvm::Value *EmittedE,
// count = ptr->count;
//
// flexible_array_member_base_size = sizeof (*ptr->array);
// flexible_array_member_size =
// count * flexible_array_member_base_size;
// flexible_array_member_size = count * flexible_array_member_base_size;
//
// if (flexible_array_member_size < 0)
// return 0;
// return flexible_array_member_size;
//
// 2) '&ptr->array[idx]':
// 2) '&((cast) ptr->array)[idx]':
//
// count = ptr->count;
// index = idx;
//
// casted_flexible_array_member_base_size = sizeof (*((cast) ptr->array));
//
// flexible_array_member_base_size = sizeof (*ptr->array);
// flexible_array_member_size =
// count * flexible_array_member_base_size;
// flexible_array_member_size = count * flexible_array_member_base_size;
//
// index_size = index * flexible_array_member_base_size;
// index_size = index * casted_flexible_array_member_base_size;
//
// if (flexible_array_member_size < 0 || index < 0)
// return 0;
Expand All @@ -1129,8 +1131,7 @@ CodeGenFunction::emitCountedByMemberSize(const Expr *E, llvm::Value *EmittedE,
// sizeof_struct = sizeof (struct s);
//
// flexible_array_member_base_size = sizeof (*ptr->array);
// flexible_array_member_size =
// count * flexible_array_member_base_size;
// flexible_array_member_size = count * flexible_array_member_base_size;
//
// field_offset = offsetof (struct s, field);
// offset_diff = sizeof_struct - field_offset;
Expand All @@ -1139,19 +1140,19 @@ CodeGenFunction::emitCountedByMemberSize(const Expr *E, llvm::Value *EmittedE,
// return 0;
// return offset_diff + flexible_array_member_size;
//
// 4) '&ptr->field_array[idx]':
// 4) '&((cast) ptr->field_array)[idx]':
//
// count = ptr->count;
// index = idx;
// sizeof_struct = sizeof (struct s);
//
// flexible_array_member_base_size = sizeof (*ptr->array);
// flexible_array_member_size =
// count * flexible_array_member_base_size;
// flexible_array_member_size = count * flexible_array_member_base_size;
//
// casted_field_base_size = sizeof (*((cast) ptr->field_array));
//
// field_base_size = sizeof (*ptr->field_array);
// field_offset = offsetof (struct s, field)
// field_offset += index * field_base_size;
// field_offset += index * casted_field_base_size;
//
// offset_diff = sizeof_struct - field_offset;
//
Expand All @@ -1162,14 +1163,11 @@ CodeGenFunction::emitCountedByMemberSize(const Expr *E, llvm::Value *EmittedE,
QualType CountTy = CountFD->getType();
bool IsSigned = CountTy->isSignedIntegerType();

QualType FlexibleArrayMemberTy = FlexibleArrayMemberFD->getType();
QualType FieldTy = FD->getType();

// Explicit cast because otherwise the CharWidth will promote an i32's into
// u64's leading to overflows..
int64_t CharWidth = static_cast<int64_t>(CGM.getContext().getCharWidth());

// size_t field_offset = offsetof (struct s, field);
// field_offset = offsetof (struct s, field);
Value *FieldOffset = nullptr;
if (FlexibleArrayMemberFD != FD) {
std::optional<int64_t> Offset = GetFieldOffset(Ctx, RD, FD);
Expand All @@ -1179,37 +1177,49 @@ CodeGenFunction::emitCountedByMemberSize(const Expr *E, llvm::Value *EmittedE,
llvm::ConstantInt::get(ResType, *Offset / CharWidth, IsSigned);
}

// size_t count = (size_t) ptr->count;
// count = ptr->count;
Value *Count = EmitLoadOfCountedByField(ME, FlexibleArrayMemberFD, CountFD);
if (!Count)
return nullptr;
Count = Builder.CreateIntCast(Count, ResType, IsSigned, "count");

// size_t index = (size_t) ptr->index;
// index = ptr->index;
Value *Index = nullptr;
if (Idx) {
bool IdxSigned = Idx->getType()->isSignedIntegerType();
Index = EmitScalarExpr(Idx);
Index = Builder.CreateIntCast(Index, ResType, IdxSigned, "index");
}

// size_t flexible_array_member_base_size = sizeof (*ptr->array);
const ArrayType *ArrayTy = Ctx.getAsArrayType(FlexibleArrayMemberTy);
CharUnits BaseSize = Ctx.getTypeSizeInChars(ArrayTy->getElementType());
// flexible_array_member_base_size = sizeof (*ptr->array);
QualType FlexibleArrayMemberTy = FlexibleArrayMemberFD->getType();
const ArrayType *FAMTy = Ctx.getAsArrayType(FlexibleArrayMemberTy);
CharUnits BaseSize = Ctx.getTypeSizeInChars(FAMTy->getElementType());
auto *FlexibleArrayMemberBaseSize =
llvm::ConstantInt::get(ResType, BaseSize.getQuantity(), IsSigned);

// size_t flexible_array_member_size =
// count * flexible_array_member_base_size;
// flexible_array_member_size = count * flexible_array_member_base_size;
Value *FlexibleArrayMemberSize =
Builder.CreateMul(Count, FlexibleArrayMemberBaseSize,
"flexible_array_member_size", !IsSigned, IsSigned);

QualType CastedArrayElementTy = Visitor.ArrayElementTy;
llvm::ConstantInt *CastedArrayElementSize = nullptr;
if (!CastedArrayElementTy.isNull() && CastedArrayElementTy->isPointerType()) {
const PointerType *FAMTy = cast<clang::PointerType>(CastedArrayElementTy);
CharUnits BaseSize = Ctx.getTypeSizeInChars(FAMTy->getPointeeType());
CastedArrayElementSize =
llvm::ConstantInt::get(ResType, BaseSize.getQuantity(), IsSigned);
}

Value *Res = nullptr;
if (FlexibleArrayMemberFD == FD) {
if (Idx) { // Option (2) '&ptr->array[idx]'
// size_t index_size = index * flexible_array_member_base_size;
Value *IndexSize = Builder.CreateMul(FlexibleArrayMemberBaseSize, Index,
if (Idx) { // Option (2) '&((cast) ptr->array)[idx]'
if (!CastedArrayElementSize)
CastedArrayElementSize = FlexibleArrayMemberBaseSize;

// index_size = index * flexible_array_member_base_size;
Value *IndexSize = Builder.CreateMul(CastedArrayElementSize, Index,
"index_size", !IsSigned, IsSigned);

// return flexible_array_member_size - index_size;
Expand All @@ -1220,28 +1230,30 @@ CodeGenFunction::emitCountedByMemberSize(const Expr *E, llvm::Value *EmittedE,
Res = FlexibleArrayMemberSize;
}
} else {
// size_t sizeof_struct = sizeof (struct s);
// sizeof_struct = sizeof (struct s);
llvm::StructType *StructTy = getTypes().getCGRecordLayout(RD).getLLVMType();
const llvm::DataLayout &Layout = CGM.getDataLayout();
TypeSize Size = Layout.getTypeSizeInBits(StructTy);
Value *SizeofStruct =
llvm::ConstantInt::get(ResType, Size.getKnownMinValue() / CharWidth);

if (Idx) { // Option (4) '&ptr->field_array[idx]'
// size_t field_base_size = sizeof (*ptr->field_array);
const ArrayType *ArrayTy = Ctx.getAsArrayType(FieldTy);
CharUnits BaseSize = Ctx.getTypeSizeInChars(ArrayTy->getElementType());
auto *FieldBaseSize =
llvm::ConstantInt::get(ResType, BaseSize.getQuantity(), IsSigned);
if (Idx) { // Option (4) '&((cast) ptr->field_array)[idx]'
// casted_field_base_size = sizeof (*((cast) ptr->field_array));
if (!CastedArrayElementSize) {
const ArrayType *ArrayTy = Ctx.getAsArrayType(FD->getType());
CharUnits BaseSize = Ctx.getTypeSizeInChars(ArrayTy->getElementType());
CastedArrayElementSize =
llvm::ConstantInt::get(ResType, BaseSize.getQuantity(), IsSigned);
}

// field_offset += index * field_base_size;
Value *Mul = Builder.CreateMul(Index, FieldBaseSize, "field_offset",
!IsSigned, IsSigned);
// field_offset += index * casted_field_base_size;
Value *Mul = Builder.CreateMul(Index, CastedArrayElementSize,
"field_offset", !IsSigned, IsSigned);
FieldOffset = Builder.CreateAdd(FieldOffset, Mul);
}
// Option (3) '&ptr->field', and Option (4) continuation.

// size_t offset_diff = flexible_array_member_offset - field_offset;
// offset_diff = flexible_array_member_offset - field_offset;
Value *OffsetDiff = Builder.CreateSub(SizeofStruct, FieldOffset,
"offset_diff", !IsSigned, IsSigned);

Expand Down
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