clang/lib/CodeGen/ABIInfo.h

//===----- ABIInfo.h - ABI information access & encapsulation ---*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef CLANG_CODEGEN_ABIINFO_H
#define CLANG_CODEGEN_ABIINFO_H

#include "clang/AST/Type.h"
#include "llvm/Type.h"

namespace llvm {
  class Value;
  class LLVMContext;
}

namespace clang {
  class ASTContext;

  // FIXME: This is a layering issue if we want to move ABIInfo
  // down. Fortunately CGFunctionInfo has no real tie to CodeGen.
  namespace CodeGen {
    class CGFunctionInfo;
    class CodeGenFunction;
  }

  // FIXME: All of this stuff should be part of the target interface
  // somehow. It is currently here because it is not clear how to factor
  // the targets to support this, since the Targets currently live in a
  // layer below types n'stuff.

  /// ABIArgInfo - Helper class to encapsulate information about how a
  /// specific C type should be passed to or returned from a function.
  class ABIArgInfo {
  public:
    enum Kind {
      Direct,    /// Pass the argument directly using the normal
                 /// converted LLVM type. Complex and structure types
                 /// are passed using first class aggregates.

      Extend,    /// Valid only for integer argument types. Same as 'direct'
                 /// but also emit a zero/sign extension attribute.

      Indirect,  /// Pass the argument indirectly via a hidden pointer
                 /// with the specified alignment (0 indicates default
                 /// alignment).

      Ignore,    /// Ignore the argument (treat as void). Useful for
                 /// void and empty structs.

      Coerce,    /// Only valid for aggregate return types, the argument
                 /// should be accessed by coercion to a provided type.

      Expand,    /// Only valid for aggregate argument types. The
                 /// structure should be expanded into consecutive
                 /// arguments for its constituent fields. Currently
                 /// expand is only allowed on structures whose fields
                 /// are all scalar types or are themselves expandable
                 /// types.

      KindFirst=Direct, KindLast=Expand
    };

  private:
    Kind TheKind;
    llvm::PATypeHolder TypeData;
    unsigned UIntData;
    bool BoolData;

    ABIArgInfo(Kind K, const llvm::Type *TD=0,
               unsigned UI=0, bool B = false) 
      : TheKind(K), TypeData(TD), UIntData(UI), BoolData(B) {}

  public:
    ABIArgInfo() : TheKind(Direct), TypeData(0), UIntData(0) {}

    static ABIArgInfo getDirect() {
      return ABIArgInfo(Direct);
    }
    static ABIArgInfo getExtend() {
      return ABIArgInfo(Extend);
    }
    static ABIArgInfo getIgnore() {
      return ABIArgInfo(Ignore);
    }
    static ABIArgInfo getCoerce(const llvm::Type *T) {
      return ABIArgInfo(Coerce, T);
    }
    static ABIArgInfo getIndirect(unsigned Alignment, bool ByVal = true) {
      return ABIArgInfo(Indirect, 0, Alignment, ByVal);
    }
    static ABIArgInfo getExpand() {
      return ABIArgInfo(Expand);
    }

    Kind getKind() const { return TheKind; }
    bool isDirect() const { return TheKind == Direct; }
    bool isExtend() const { return TheKind == Extend; }
    bool isIgnore() const { return TheKind == Ignore; }
    bool isCoerce() const { return TheKind == Coerce; }
    bool isIndirect() const { return TheKind == Indirect; }
    bool isExpand() const { return TheKind == Expand; }

    // Coerce accessors
    const llvm::Type *getCoerceToType() const {
      assert(TheKind == Coerce && "Invalid kind!");
      return TypeData;
    }

    // Indirect accessors
    unsigned getIndirectAlign() const {
      assert(TheKind == Indirect && "Invalid kind!");
      return UIntData;
    }

    bool getIndirectByVal() const {
      assert(TheKind == Indirect && "Invalid kind!");
      return BoolData;
    }
    
    void dump() const;
  };

  /// ABIInfo - Target specific hooks for defining how a type should be
  /// passed or returned from functions.
  class ABIInfo {
  public:
    virtual ~ABIInfo();

    virtual void computeInfo(CodeGen::CGFunctionInfo &FI,
                             ASTContext &Ctx,
                             llvm::LLVMContext &VMContext,
                             // This is the preferred type for argument lowering
                             // which can be used to generate better IR.
                             const llvm::Type *const *PrefTypes = 0,
                             unsigned NumPrefTypes = 0) const = 0;

    /// EmitVAArg - Emit the target dependent code to load a value of
    /// \arg Ty from the va_list pointed to by \arg VAListAddr.

    // FIXME: This is a gaping layering violation if we wanted to drop
    // the ABI information any lower than CodeGen. Of course, for
    // VAArg handling it has to be at this level; there is no way to
    // abstract this out.
    virtual llvm::Value *EmitVAArg(llvm::Value *VAListAddr, QualType Ty,
                                   CodeGen::CodeGenFunction &CGF) const = 0;
  };
}  // end namespace clang

#endif