[llvm] [LLVMABI] The ABI Typesystem (PR #158329)

via llvm-commits llvm-commits at lists.llvm.org
Fri Sep 12 09:52:49 PDT 2025


https://github.com/vortex73 created https://github.com/llvm/llvm-project/pull/158329

This PR introduces the foundational components for a new LLVM ABI lowering library, implementing this [RFC](https://discourse.llvm.org/t/rfc-an-abi-lowering-library-for-llvm/84495)



>From 1e1e2ec14b72958e7cbc92b286cdd53d41c82d71 Mon Sep 17 00:00:00 2001
From: Narayan Sreekumar <nsreekumar6 at gmail.com>
Date: Fri, 12 Sep 2025 19:25:56 +0530
Subject: [PATCH] [LLVMABI] The ABI Typesystem

---
 llvm/include/llvm/ABI/Types.h | 453 ++++++++++++++++++++++++++++++++++
 1 file changed, 453 insertions(+)
 create mode 100644 llvm/include/llvm/ABI/Types.h

diff --git a/llvm/include/llvm/ABI/Types.h b/llvm/include/llvm/ABI/Types.h
new file mode 100644
index 0000000000000..ff9551fc6e295
--- /dev/null
+++ b/llvm/include/llvm/ABI/Types.h
@@ -0,0 +1,453 @@
+//===- ABI/Types.h ----------------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file defines the Types and related helper methods concerned to the
+/// LLVMABI library which mirrors ABI related type information from
+/// the LLVM frontend.
+///
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_ABI_TYPES_H
+#define LLVM_ABI_TYPES_H
+
+#include "llvm/ADT/APFloat.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Support/Alignment.h"
+#include "llvm/Support/Allocator.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/TypeSize.h"
+
+namespace llvm {
+namespace abi {
+
+enum class TypeKind {
+  Void,
+  MemberPointer,
+  Complex,
+  Integer,
+  Float,
+  Pointer,
+  Array,
+  Vector,
+  Record,
+};
+
+/// Represents the ABI-specific view of a type in LLVM.
+///
+/// This abstracts platform and language-specific ABI details from the
+/// frontend, providing a consistent interface for the ABI Library.
+class Type {
+private:
+  TypeSize getTypeStoreSize() const {
+    TypeSize StoreSizeInBits = getTypeStoreSizeInBits();
+    return {StoreSizeInBits.getKnownMinValue() / 8,
+            StoreSizeInBits.isScalable()};
+  }
+  TypeSize getTypeStoreSizeInBits() const {
+    TypeSize BaseSize = getSizeInBits();
+    uint64_t AlignedSizeInBits =
+        alignToPowerOf2(BaseSize.getKnownMinValue(), 8);
+    return {AlignedSizeInBits, BaseSize.isScalable()};
+  }
+
+protected:
+  TypeKind Kind;
+  TypeSize SizeInBits;
+  Align ABIAlignment;
+
+  Type(TypeKind K, TypeSize SizeInBits, Align ABIAlign)
+      : Kind(K), SizeInBits(SizeInBits), ABIAlignment(ABIAlign) {}
+
+public:
+  TypeKind getKind() const { return Kind; }
+  TypeSize getSizeInBits() const { return SizeInBits; }
+  Align getAlignment() const { return ABIAlignment; }
+
+  TypeSize getTypeAllocSize() const {
+    return alignTo(getTypeStoreSize(), getAlignment().value());
+  }
+
+  bool isVoid() const { return Kind == TypeKind::Void; }
+  bool isInteger() const { return Kind == TypeKind::Integer; }
+  bool isFloat() const { return Kind == TypeKind::Float; }
+  bool isPointer() const { return Kind == TypeKind::Pointer; }
+  bool isArray() const { return Kind == TypeKind::Array; }
+  bool isVector() const { return Kind == TypeKind::Vector; }
+  bool isRecord() const { return Kind == TypeKind::Record; }
+  bool isMemberPointer() const { return Kind == TypeKind::MemberPointer; }
+  bool isComplex() const { return Kind == TypeKind::Complex; }
+};
+
+class VoidType : public Type {
+public:
+  VoidType() : Type(TypeKind::Void, TypeSize::getFixed(0), Align(1)) {}
+
+  static bool classof(const Type *T) { return T->getKind() == TypeKind::Void; }
+};
+
+class ComplexType : public Type {
+public:
+  ComplexType(const Type *ElementType, uint64_t SizeInBits, Align Alignment)
+      : Type(TypeKind::Complex, TypeSize::getFixed(SizeInBits), Alignment),
+        ElementType(ElementType) {}
+
+  const Type *getElementType() const { return ElementType; }
+
+  static bool classof(const Type *T) {
+    return T->getKind() == TypeKind::Complex;
+  }
+
+private:
+  const Type *ElementType;
+};
+
+class IntegerType : public Type {
+private:
+  bool IsSigned;
+  bool IsBitInt;
+
+public:
+  IntegerType(uint64_t BitWidth, Align ABIAlign, bool IsSigned,
+              bool IsBitInt = false)
+      : Type(TypeKind::Integer, TypeSize::getFixed(BitWidth), ABIAlign),
+        IsSigned(IsSigned), IsBitInt(IsBitInt) {}
+
+  bool isSigned() const { return IsSigned; }
+  bool isBitInt() const { return IsBitInt; }
+  bool isBool() const {
+    return getSizeInBits().getFixedValue() == 1 && !IsBitInt;
+  }
+
+  static bool classof(const Type *T) {
+    return T->getKind() == TypeKind::Integer;
+  }
+};
+
+class FloatType : public Type {
+private:
+  const fltSemantics *Semantics;
+
+public:
+  FloatType(const fltSemantics &FloatSemantics, Align ABIAlign)
+      : Type(TypeKind::Float,
+             TypeSize::getFixed(APFloat::getSizeInBits(FloatSemantics)),
+             ABIAlign),
+        Semantics(&FloatSemantics) {}
+
+  const fltSemantics *getSemantics() const { return Semantics; }
+  static bool classof(const Type *T) { return T->getKind() == TypeKind::Float; }
+};
+
+class PointerLikeType : public Type {
+protected:
+  unsigned AddrSpace;
+  PointerLikeType(TypeKind K, TypeSize SizeInBits, Align ABIAlign, unsigned AS)
+      : Type(K, SizeInBits, ABIAlign), AddrSpace(AS) {}
+
+public:
+  unsigned getAddrSpace() const { return AddrSpace; }
+  bool isMemberPointer() const { return getKind() == TypeKind::MemberPointer; }
+
+  static bool classof(const Type *T) {
+    return T->getKind() == TypeKind::Pointer ||
+           T->getKind() == TypeKind::MemberPointer;
+  }
+};
+
+class PointerType : public PointerLikeType {
+public:
+  PointerType(uint64_t Size, Align ABIAlign, unsigned AddressSpace = 0)
+      : PointerLikeType(TypeKind::Pointer, TypeSize::getFixed(Size), ABIAlign,
+                        AddressSpace) {}
+
+  static bool classof(const Type *T) {
+    return T->getKind() == TypeKind::Pointer;
+  }
+};
+
+class MemberPointerType : public PointerLikeType {
+private:
+  bool IsFunctionPointer;
+
+public:
+  MemberPointerType(bool IsFunctionPointer, uint64_t SizeInBits, Align ABIAlign,
+                    unsigned AddressSpace = 0)
+      : PointerLikeType(TypeKind::MemberPointer, TypeSize::getFixed(SizeInBits),
+                        ABIAlign, AddressSpace),
+        IsFunctionPointer(IsFunctionPointer) {}
+  bool isFunctionPointer() const { return IsFunctionPointer; }
+
+  static bool classof(const Type *T) {
+    return T->getKind() == TypeKind::MemberPointer;
+  }
+};
+
+class ArrayType : public Type {
+private:
+  const Type *ElementType;
+  uint64_t NumElements;
+  bool IsMatrix;
+
+public:
+  ArrayType(const Type *ElementType, uint64_t NumElements, uint64_t SizeInBits,
+            bool IsMatrixType = false)
+      : Type(TypeKind::Array, TypeSize::getFixed(SizeInBits),
+             ElementType->getAlignment()),
+        ElementType(ElementType), NumElements(NumElements),
+        IsMatrix(IsMatrixType) {}
+
+  const Type *getElementType() const { return ElementType; }
+  uint64_t getNumElements() const { return NumElements; }
+  bool isMatrixType() const { return IsMatrix; }
+
+  static bool classof(const Type *T) { return T->getKind() == TypeKind::Array; }
+};
+
+class VectorType : public Type {
+private:
+  const Type *ElementType;
+  ElementCount NumElements;
+
+public:
+  VectorType(const Type *ElementType, ElementCount NumElements, Align ABIAlign)
+      : Type(TypeKind::Vector,
+             TypeSize(ElementType->getSizeInBits().getFixedValue() *
+                          NumElements.getKnownMinValue(),
+                      NumElements.isScalable()),
+             ABIAlign),
+        ElementType(ElementType), NumElements(NumElements) {}
+
+  const Type *getElementType() const { return ElementType; }
+  ElementCount getNumElements() const { return NumElements; }
+
+  static bool classof(const Type *T) {
+    return T->getKind() == TypeKind::Vector;
+  }
+};
+
+struct FieldInfo {
+  const Type *FieldType;
+  uint64_t OffsetInBits;
+  uint64_t BitFieldWidth;
+  bool IsBitField;
+  bool IsUnnamedBitfield;
+
+  FieldInfo(const Type *FieldType, uint64_t OffsetInBits = 0,
+            bool IsBitField = false, uint64_t BitFieldWidth = 0,
+            bool IsUnnamedBitField = false)
+      : FieldType(FieldType), OffsetInBits(OffsetInBits),
+        BitFieldWidth(BitFieldWidth), IsBitField(IsBitField),
+        IsUnnamedBitfield(IsUnnamedBitField) {}
+};
+
+enum class StructPacking { Default, Packed, ExplicitPacking };
+
+class RecordType : public Type {
+private:
+  ArrayRef<FieldInfo> Fields;
+  ArrayRef<FieldInfo> BaseClasses;
+  ArrayRef<FieldInfo> VirtualBaseClasses;
+  StructPacking Packing;
+  struct {
+    LLVM_PREFERRED_TYPE(bool) unsigned CanPassInRegisters : 1;
+    LLVM_PREFERRED_TYPE(bool) unsigned IsUnion : 1;
+    LLVM_PREFERRED_TYPE(bool) unsigned IsTransparent : 1;
+    LLVM_PREFERRED_TYPE(bool) unsigned IsCXXRecord : 1;
+    LLVM_PREFERRED_TYPE(bool) unsigned IsPolymorphic : 1;
+    LLVM_PREFERRED_TYPE(bool) unsigned HasFlexibleArrayMember : 1;
+  } Flags = {};
+
+public:
+  RecordType(ArrayRef<FieldInfo> StructFields, ArrayRef<FieldInfo> Bases,
+             ArrayRef<FieldInfo> VBases, TypeSize Size, Align Align,
+             StructPacking Pack = StructPacking::Default, bool Union = false,
+             bool CXXRecord = false, bool Polymorphic = false,
+             bool FlexibleArray = false, bool CanPassInRegs = false,
+             bool Transparent = false)
+      : Type(TypeKind::Record, Size, Align), Fields(StructFields),
+        BaseClasses(Bases), VirtualBaseClasses(VBases), Packing(Pack) {
+
+    Flags.CanPassInRegisters = CanPassInRegs;
+    Flags.IsUnion = Union;
+    Flags.IsTransparent = Transparent;
+    Flags.IsCXXRecord = CXXRecord;
+    Flags.IsPolymorphic = Polymorphic;
+    Flags.HasFlexibleArrayMember = FlexibleArray;
+  }
+  uint32_t getNumFields() const { return Fields.size(); }
+  StructPacking getPacking() const { return Packing; }
+
+  bool isUnion() const { return Flags.IsUnion; }
+  bool isCXXRecord() const { return Flags.IsCXXRecord; }
+  bool isPolymorphic() const { return Flags.IsPolymorphic; }
+  bool canPassInRegisters() const { return Flags.CanPassInRegisters; }
+  bool hasFlexibleArrayMember() const { return Flags.HasFlexibleArrayMember; }
+
+  uint32_t getNumBaseClasses() const { return BaseClasses.size(); }
+  uint32_t getNumVirtualBaseClasses() const {
+    return VirtualBaseClasses.size();
+  }
+  bool isTransparentUnion() const { return Flags.IsTransparent; }
+  ArrayRef<FieldInfo> getFields() const { return Fields; }
+  ArrayRef<FieldInfo> getBaseClasses() const { return BaseClasses; }
+  ArrayRef<FieldInfo> getVirtualBaseClasses() const {
+    return VirtualBaseClasses;
+  }
+
+  static bool isEmptyForABI(const llvm::abi::Type *Ty) {
+    const auto *RT = dyn_cast<RecordType>(Ty);
+    if (!RT)
+      return false;
+
+    for (const auto &Field : RT->getFields()) {
+      if (!Field.IsUnnamedBitfield)
+        return false;
+    }
+
+    if (RT->isCXXRecord()) {
+      for (const auto &Base : RT->getBaseClasses()) {
+        if (!isEmptyForABI(Base.FieldType))
+          return false;
+      }
+
+      for (const auto &VBase : RT->getVirtualBaseClasses()) {
+        if (!isEmptyForABI(VBase.FieldType))
+          return false;
+      }
+    }
+
+    return true;
+  }
+};
+
+/// TypeBuilder manages the lifecycle of ABI types using bump pointer
+/// allocation. Types created by a TypeBuilder are valid for the lifetime of the
+/// builder.
+///
+/// Example usage:
+/// \code
+///   BumpPtrAllocator Alloc;
+///   TypeBuilder Builder(Alloc);
+///   const auto *IntTy = Builder.getIntegerType(32, Align(4), true);
+/// \endcode
+class TypeBuilder {
+private:
+  BumpPtrAllocator &Allocator;
+
+public:
+  explicit TypeBuilder(BumpPtrAllocator &Alloc) : Allocator(Alloc) {}
+
+  const VoidType *getVoidType() {
+    return new (Allocator.Allocate<VoidType>()) VoidType();
+  }
+
+  const IntegerType *getIntegerType(uint64_t BitWidth, Align Align, bool Signed,
+                                    bool IsBitInt = false) {
+    return new (Allocator.Allocate<IntegerType>())
+        IntegerType(BitWidth, Align, Signed, IsBitInt);
+  }
+
+  const FloatType *getFloatType(const fltSemantics &Semantics, Align Align) {
+    return new (Allocator.Allocate<FloatType>()) FloatType(Semantics, Align);
+  }
+
+  const PointerType *getPointerType(uint64_t Size, Align Align,
+                                    unsigned Addrspace = 0) {
+    return new (Allocator.Allocate<PointerType>())
+        PointerType(Size, Align, Addrspace);
+  }
+
+  const ArrayType *getArrayType(const Type *ElementType, uint64_t NumElements,
+                                uint64_t SizeInBits,
+                                bool IsMatrixType = false) {
+    return new (Allocator.Allocate<ArrayType>())
+        ArrayType(ElementType, NumElements, SizeInBits, IsMatrixType);
+  }
+
+  const VectorType *getVectorType(const Type *ElementType,
+                                  ElementCount NumElements, Align Align) {
+    return new (Allocator.Allocate<VectorType>())
+        VectorType(ElementType, NumElements, Align);
+  }
+
+  const RecordType *
+  getRecordType(ArrayRef<FieldInfo> Fields, TypeSize Size, Align Align,
+                StructPacking Pack = StructPacking::Default,
+                ArrayRef<FieldInfo> BaseClasses = {},
+                ArrayRef<FieldInfo> VirtualBaseClasses = {},
+                bool CXXRecord = false, bool Polymorphic = false,
+                bool FlexibleArray = false, bool CanPassInRegister = false) {
+    FieldInfo *FieldArray = Allocator.Allocate<FieldInfo>(Fields.size());
+    std::copy(Fields.begin(), Fields.end(), FieldArray);
+
+    FieldInfo *BaseArray = nullptr;
+    if (!BaseClasses.empty()) {
+      BaseArray = Allocator.Allocate<FieldInfo>(BaseClasses.size());
+      std::copy(BaseClasses.begin(), BaseClasses.end(), BaseArray);
+    }
+
+    FieldInfo *VBaseArray = nullptr;
+    if (!VirtualBaseClasses.empty()) {
+      VBaseArray = Allocator.Allocate<FieldInfo>(VirtualBaseClasses.size());
+      std::copy(VirtualBaseClasses.begin(), VirtualBaseClasses.end(),
+                VBaseArray);
+    }
+
+    ArrayRef<FieldInfo> FieldsRef(FieldArray, Fields.size());
+    ArrayRef<FieldInfo> BasesRef(BaseArray, BaseClasses.size());
+    ArrayRef<FieldInfo> VBasesRef(VBaseArray, VirtualBaseClasses.size());
+
+    return new (Allocator.Allocate<RecordType>())
+        RecordType(FieldsRef, BasesRef, VBasesRef, Size, Align, Pack, false,
+                   CXXRecord, Polymorphic, FlexibleArray, CanPassInRegister);
+  }
+
+  const RecordType *getUnionType(ArrayRef<FieldInfo> Fields, TypeSize Size,
+                                 Align Align,
+                                 StructPacking Pack = StructPacking::Default,
+                                 bool IsTransparent = false,
+                                 bool CanPassInRegs = false,
+                                 bool CXXRecord = false) {
+    FieldInfo *FieldArray = Allocator.Allocate<FieldInfo>(Fields.size());
+
+    for (size_t I = 0; I < Fields.size(); ++I) {
+      const FieldInfo &Field = Fields[I];
+      new (&FieldArray[I])
+          FieldInfo(Field.FieldType, 0, Field.IsBitField, Field.BitFieldWidth,
+                    Field.IsUnnamedBitfield);
+    }
+
+    ArrayRef<FieldInfo> FieldsRef(FieldArray, Fields.size());
+
+    return new (Allocator.Allocate<RecordType>()) RecordType(
+        FieldsRef, ArrayRef<FieldInfo>(), ArrayRef<FieldInfo>(), Size, Align,
+        Pack, true, CXXRecord, false, false, CanPassInRegs, IsTransparent);
+  }
+
+  const ComplexType *getComplexType(const Type *ElementType, Align Align) {
+    // Complex types have two elements (real and imaginary parts)
+    uint64_t ElementSize = ElementType->getSizeInBits().getFixedValue();
+    uint64_t ComplexSize = ElementSize * 2;
+
+    return new (Allocator.Allocate<ComplexType>())
+        ComplexType(ElementType, ComplexSize, Align);
+  }
+
+  const MemberPointerType *getMemberPointerType(bool IsFunctionPointer,
+                                                uint64_t SizeInBits,
+                                                Align Align) {
+    return new (Allocator.Allocate<MemberPointerType>())
+        MemberPointerType(IsFunctionPointer, SizeInBits, Align);
+  }
+};
+
+} // namespace abi
+} // namespace llvm
+
+#endif



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