[clang] [NFC][Clang] Refactor code to calculate flexible array member size (PR #72790)
Bill Wendling via cfe-commits
cfe-commits at lists.llvm.org
Sun Nov 19 02:30:59 PST 2023
https://github.com/bwendling created https://github.com/llvm/llvm-project/pull/72790
The code that calculates the flexible array member size is big enough to warrant its own method.
>From fcea607665cdbae3e98f08288b165c2c1af24f95 Mon Sep 17 00:00:00 2001
From: Bill Wendling <morbo at google.com>
Date: Sun, 19 Nov 2023 02:28:28 -0800
Subject: [PATCH] [NFC][Clang] Refactor code to calculate flexible array member
size
The code that calculates the flexible array member size is big enough to
warrant its own method.
---
clang/lib/CodeGen/CGBuiltin.cpp | 296 +++++++++++++++-------------
clang/lib/CodeGen/CodeGenFunction.h | 3 +
2 files changed, 159 insertions(+), 140 deletions(-)
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 09309a3937fb613..b869bca7f07b85a 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -822,6 +822,158 @@ CodeGenFunction::evaluateOrEmitBuiltinObjectSize(const Expr *E, unsigned Type,
return ConstantInt::get(ResType, ObjectSize, /*isSigned=*/true);
}
+llvm::Value *
+CodeGenFunction::emitFlexibleArrayMemberSize(const Expr *E, unsigned Type,
+ llvm::IntegerType *ResType) {
+ // The code generated here calculates the size of a struct with a flexible
+ // array member that uses the counted_by attribute. There are two instances
+ // we handle:
+ //
+ // struct s {
+ // unsigned long flags;
+ // int count;
+ // int array[] __attribute__((counted_by(count)));
+ // }
+ //
+ // 1) bdos of the flexible array itself:
+ //
+ // __builtin_dynamic_object_size(p->array, 1) ==
+ // p->count * sizeof(*p->array)
+ //
+ // 2) bdos of a pointer into the flexible array:
+ //
+ // __builtin_dynamic_object_size(&p->array[42], 1) ==
+ // (p->count - 42) * sizeof(*p->array)
+ //
+ // 2) bdos of the whole struct, including the flexible array:
+ //
+ // __builtin_dynamic_object_size(p, 1) ==
+ // max(sizeof(struct s),
+ // offsetof(struct s, array) + p->count * sizeof(*p->array))
+ //
+ const Expr *Base = E->IgnoreParenImpCasts();
+ const Expr *Idx = nullptr;
+
+ if (const auto *UO = dyn_cast<UnaryOperator>(Base);
+ UO && UO->getOpcode() == UO_AddrOf) {
+ if (const auto *ASE =
+ dyn_cast<ArraySubscriptExpr>(UO->getSubExpr()->IgnoreParens())) {
+ Base = ASE->getBase();
+ Idx = ASE->getIdx()->IgnoreParenImpCasts();
+
+ if (const auto *IL = dyn_cast<IntegerLiteral>(Idx);
+ IL && !IL->getValue().getSExtValue())
+ Idx = nullptr;
+ }
+ }
+
+ const ValueDecl *CountedByFD = FindCountedByField(Base);
+ if (!CountedByFD)
+ // Can't find the field referenced by the "counted_by" attribute.
+ return nullptr;
+
+ // Build a load of the counted_by field.
+ bool IsSigned = CountedByFD->getType()->isSignedIntegerType();
+ const RecordDecl *OuterRD =
+ CountedByFD->getDeclContext()->getOuterLexicalRecordContext();
+ ASTContext &Ctx = getContext();
+
+ // Load the counted_by field.
+ const Expr *CountedByExpr = BuildCountedByFieldExpr(Base, CountedByFD);
+ Value *CountedByInst = EmitAnyExprToTemp(CountedByExpr).getScalarVal();
+ llvm::Type *CountedByTy = CountedByInst->getType();
+
+ if (Idx) {
+ // There's an index into the array. Remove it from the count.
+ bool IdxSigned = Idx->getType()->isSignedIntegerType();
+ Value *IdxInst = EmitAnyExprToTemp(Idx).getScalarVal();
+ IdxInst = IdxSigned ? Builder.CreateSExtOrTrunc(IdxInst, CountedByTy)
+ : Builder.CreateZExtOrTrunc(IdxInst, CountedByTy);
+
+ // If the index is negative, don't subtract it from the counted_by
+ // value. The pointer is pointing to something before the FAM.
+ IdxInst = Builder.CreateNeg(IdxInst, "", !IdxSigned, IdxSigned);
+ CountedByInst =
+ Builder.CreateAdd(CountedByInst, IdxInst, "", !IsSigned, IsSigned);
+ }
+
+ // Get the size of the flexible array member's base type.
+ const ValueDecl *FAMDecl = nullptr;
+ if (const auto *ME = dyn_cast<MemberExpr>(Base)) {
+ const LangOptions::StrictFlexArraysLevelKind StrictFlexArraysLevel =
+ getLangOpts().getStrictFlexArraysLevel();
+ if (const ValueDecl *MD = ME->getMemberDecl()) {
+ if (!Decl::isFlexibleArrayMemberLike(
+ Ctx, MD, MD->getType(), StrictFlexArraysLevel,
+ /*IgnoreTemplateOrMacroSubstitution=*/true))
+ return nullptr;
+ // Base is referencing the FAM itself.
+ FAMDecl = MD;
+ }
+ }
+
+ if (!FAMDecl)
+ FAMDecl = FindFlexibleArrayMemberField(Ctx, OuterRD);
+
+ assert(FAMDecl && "Can't find the flexible array member field");
+
+ const ArrayType *ArrayTy = Ctx.getAsArrayType(FAMDecl->getType());
+ CharUnits Size = Ctx.getTypeSizeInChars(ArrayTy->getElementType());
+ llvm::Constant *ElemSize =
+ llvm::ConstantInt::get(CountedByTy, Size.getQuantity(), IsSigned);
+
+ // Calculate how large the flexible array member is in bytes.
+ Value *FAMSize =
+ Builder.CreateMul(CountedByInst, ElemSize, "", !IsSigned, IsSigned);
+ FAMSize = IsSigned ? Builder.CreateSExtOrTrunc(FAMSize, ResType)
+ : Builder.CreateZExtOrTrunc(FAMSize, ResType);
+ Value *Res = FAMSize;
+
+ if (const auto *DRE = dyn_cast<DeclRefExpr>(Base)) {
+ // The whole struct is specificed in the __bdos.
+ const ASTRecordLayout &Layout = Ctx.getASTRecordLayout(OuterRD);
+
+ // Get the offset of the FAM.
+ CharUnits Offset = Ctx.toCharUnitsFromBits(Ctx.getFieldOffset(FAMDecl));
+ llvm::Constant *FAMOffset =
+ ConstantInt::get(ResType, Offset.getQuantity(), IsSigned);
+
+ // max(sizeof(struct s),
+ // offsetof(struct s, array) + p->count * sizeof(*p->array))
+ Value *OffsetAndFAMSize =
+ Builder.CreateAdd(FAMOffset, Res, "", !IsSigned, IsSigned);
+
+ // Get the full size of the struct.
+ llvm::Constant *SizeofStruct =
+ ConstantInt::get(ResType, Layout.getSize().getQuantity(), IsSigned);
+
+ Res = IsSigned
+ ? Builder.CreateBinaryIntrinsic(
+ llvm::Intrinsic::smax, OffsetAndFAMSize, SizeofStruct)
+ : Builder.CreateBinaryIntrinsic(
+ llvm::Intrinsic::umax, OffsetAndFAMSize, SizeofStruct);
+ } else if (const auto *ME = dyn_cast<MemberExpr>(Base)) {
+ // Pointing to a place before the FAM. Add the difference to the FAM's
+ // size.
+ if (const ValueDecl *MD = ME->getMemberDecl(); MD != FAMDecl) {
+ CharUnits Offset = Ctx.toCharUnitsFromBits(Ctx.getFieldOffset(MD));
+ CharUnits FAMOffset =
+ Ctx.toCharUnitsFromBits(Ctx.getFieldOffset(FAMDecl));
+
+ Res = Builder.CreateAdd(
+ Res, ConstantInt::get(ResType, FAMOffset.getQuantity() -
+ Offset.getQuantity()));
+ }
+ }
+
+ // A negative 'FAMSize' means that the index was greater than the count,
+ // or an improperly set count field. Return -1 (for types 0 and 1) or 0
+ // (for types 2 and 3).
+ return Builder.CreateSelect(
+ Builder.CreateIsNeg(FAMSize),
+ getDefaultBuiltinObjectSizeResult(Type, ResType), Res);
+}
+
/// Returns a Value corresponding to the size of the given expression.
/// This Value may be either of the following:
/// - A llvm::Argument (if E is a param with the pass_object_size attribute on
@@ -861,146 +1013,10 @@ CodeGenFunction::emitBuiltinObjectSize(const Expr *E, unsigned Type,
return getDefaultBuiltinObjectSizeResult(Type, ResType);
if (IsDynamic) {
- // The code generated here calculates the size of a struct with a flexible
- // array member that uses the counted_by attribute. There are two instances
- // we handle:
- //
- // struct s {
- // unsigned long flags;
- // int count;
- // int array[] __attribute__((counted_by(count)));
- // }
- //
- // 1) bdos of the flexible array itself:
- //
- // __builtin_dynamic_object_size(p->array, 1) ==
- // p->count * sizeof(*p->array)
- //
- // 2) bdos of a pointer into the flexible array:
- //
- // __builtin_dynamic_object_size(&p->array[42], 1) ==
- // (p->count - 42) * sizeof(*p->array)
- //
- // 2) bdos of the whole struct, including the flexible array:
- //
- // __builtin_dynamic_object_size(p, 1) ==
- // max(sizeof(struct s),
- // offsetof(struct s, array) + p->count * sizeof(*p->array))
- //
- const Expr *Base = E->IgnoreParenImpCasts();
- const Expr *Idx = nullptr;
- if (const auto *UO = dyn_cast<UnaryOperator>(Base);
- UO && UO->getOpcode() == UO_AddrOf) {
- if (const auto *ASE =
- dyn_cast<ArraySubscriptExpr>(UO->getSubExpr()->IgnoreParens())) {
- Base = ASE->getBase();
- Idx = ASE->getIdx()->IgnoreParenImpCasts();
-
- if (const auto *IL = dyn_cast<IntegerLiteral>(Idx);
- IL && !IL->getValue().getSExtValue())
- Idx = nullptr;
- }
- }
-
- if (const ValueDecl *CountedByFD = FindCountedByField(Base)) {
- bool IsSigned = CountedByFD->getType()->isSignedIntegerType();
- const RecordDecl *OuterRD =
- CountedByFD->getDeclContext()->getOuterLexicalRecordContext();
- ASTContext &Ctx = getContext();
-
- // Load the counted_by field.
- const Expr *CountedByExpr = BuildCountedByFieldExpr(Base, CountedByFD);
- Value *CountedByInst = EmitAnyExprToTemp(CountedByExpr).getScalarVal();
- llvm::Type *CountedByTy = CountedByInst->getType();
-
- if (Idx) {
- // There's an index into the array. Remove it from the count.
- bool IdxSigned = Idx->getType()->isSignedIntegerType();
- Value *IdxInst = EmitAnyExprToTemp(Idx).getScalarVal();
- IdxInst = IdxSigned ? Builder.CreateSExtOrTrunc(IdxInst, CountedByTy)
- : Builder.CreateZExtOrTrunc(IdxInst, CountedByTy);
-
- // If the index is negative, don't subtract it from the counted_by
- // value. The pointer is pointing to something before the FAM.
- IdxInst = Builder.CreateNeg(IdxInst, "", !IdxSigned, IdxSigned);
- CountedByInst =
- Builder.CreateAdd(CountedByInst, IdxInst, "", !IsSigned, IsSigned);
- }
-
- // Get the size of the flexible array member's base type.
- const ValueDecl *FAMDecl = nullptr;
- if (const auto *ME = dyn_cast<MemberExpr>(Base)) {
- const LangOptions::StrictFlexArraysLevelKind StrictFlexArraysLevel =
- getLangOpts().getStrictFlexArraysLevel();
- if (const ValueDecl *MD = ME->getMemberDecl();
- MD && Decl::isFlexibleArrayMemberLike(
- Ctx, MD, MD->getType(), StrictFlexArraysLevel,
- /*IgnoreTemplateOrMacroSubstitution=*/true))
- // Base is referencing the FAM itself.
- FAMDecl = MD;
- }
-
- if (!FAMDecl)
- FAMDecl = FindFlexibleArrayMemberField(Ctx, OuterRD);
-
- assert(FAMDecl && "Can't find the flexible array member field");
-
- const ArrayType *ArrayTy = Ctx.getAsArrayType(FAMDecl->getType());
- CharUnits Size = Ctx.getTypeSizeInChars(ArrayTy->getElementType());
- llvm::Constant *ElemSize =
- llvm::ConstantInt::get(CountedByTy, Size.getQuantity(), IsSigned);
-
- // Calculate how large the flexible array member is in bytes.
- Value *FAMSize =
- Builder.CreateMul(CountedByInst, ElemSize, "", !IsSigned, IsSigned);
- FAMSize = IsSigned ? Builder.CreateSExtOrTrunc(FAMSize, ResType)
- : Builder.CreateZExtOrTrunc(FAMSize, ResType);
- Value *Res = FAMSize;
-
- if (const auto *DRE = dyn_cast<DeclRefExpr>(Base)) {
- // The whole struct is specificed in the __bdos.
- const ASTRecordLayout &Layout = Ctx.getASTRecordLayout(OuterRD);
-
- // Get the offset of the FAM.
- CharUnits Offset = Ctx.toCharUnitsFromBits(Ctx.getFieldOffset(FAMDecl));
- llvm::Constant *FAMOffset =
- ConstantInt::get(ResType, Offset.getQuantity(), IsSigned);
-
- // max(sizeof(struct s),
- // offsetof(struct s, array) + p->count * sizeof(*p->array))
- Value *OffsetAndFAMSize =
- Builder.CreateAdd(FAMOffset, Res, "", !IsSigned, IsSigned);
-
- // Get the full size of the struct.
- llvm::Constant *SizeofStruct =
- ConstantInt::get(ResType, Layout.getSize().getQuantity(), IsSigned);
-
- Res = IsSigned
- ? Builder.CreateBinaryIntrinsic(
- llvm::Intrinsic::smax, OffsetAndFAMSize, SizeofStruct)
- : Builder.CreateBinaryIntrinsic(
- llvm::Intrinsic::umax, OffsetAndFAMSize, SizeofStruct);
- } else if (const auto *ME = dyn_cast<MemberExpr>(Base)) {
- // Pointing to a place before the FAM. Add the difference to the FAM's
- // size.
- if (const ValueDecl *MD = ME->getMemberDecl(); MD != FAMDecl) {
- CharUnits Offset = Ctx.toCharUnitsFromBits(Ctx.getFieldOffset(MD));
- CharUnits FAMOffset =
- Ctx.toCharUnitsFromBits(Ctx.getFieldOffset(FAMDecl));
-
- Res = Builder.CreateAdd(
- Res, ConstantInt::get(ResType, FAMOffset.getQuantity() -
- Offset.getQuantity()));
- }
- }
-
- // A negative 'FAMSize' means that the index was greater than the count,
- // or an improperly set count field. Return -1 (for types 0 and 1) or 0
- // (for types 2 and 3).
- return Builder.CreateSelect(
- Builder.CreateIsNeg(FAMSize),
- getDefaultBuiltinObjectSizeResult(Type, ResType), Res);
- }
+ // Emit special code for a flexible array member with the "counted_by"
+ // attribute.
+ if (Value *V = emitFlexibleArrayMemberSize(E, Type, ResType))
+ return V;
}
Value *Ptr = EmittedE ? EmittedE : EmitScalarExpr(E);
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index b4c634dcf553728..618e78809db408b 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -4830,6 +4830,9 @@ class CodeGenFunction : public CodeGenTypeCache {
llvm::Value *EmittedE,
bool IsDynamic);
+ llvm::Value *emitFlexibleArrayMemberSize(const Expr *E, unsigned Type,
+ llvm::IntegerType *ResType);
+
void emitZeroOrPatternForAutoVarInit(QualType type, const VarDecl &D,
Address Loc);
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