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//===---- TargetInfo.h - Encapsulate target details -------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// These classes wrap the information about a call or function
// definition used to handle ABI compliancy.
//
//===----------------------------------------------------------------------===//
#ifndef CLANG_CODEGEN_TARGETINFO_H
#define CLANG_CODEGEN_TARGETINFO_H
#include "clang/AST/Type.h"
#include "clang/Basic/LLVM.h"
#include "llvm/ADT/StringRef.h"
namespace llvm {
class GlobalValue;
class Type;
class Value;
}
namespace clang {
class ABIInfo;
class Decl;
namespace CodeGen {
class CallArgList;
class CodeGenModule;
class CodeGenFunction;
class CGFunctionInfo;
}
/// TargetCodeGenInfo - This class organizes various target-specific
/// codegeneration issues, like target-specific attributes, builtins and so
/// on.
class TargetCodeGenInfo {
ABIInfo *Info;
public:
// WARNING: Acquires the ownership of ABIInfo.
TargetCodeGenInfo(ABIInfo *info = 0):Info(info) { }
virtual ~TargetCodeGenInfo();
/// getABIInfo() - Returns ABI info helper for the target.
const ABIInfo& getABIInfo() const { return *Info; }
/// SetTargetAttributes - Provides a convenient hook to handle extra
/// target-specific attributes for the given global.
virtual void SetTargetAttributes(const Decl *D, llvm::GlobalValue *GV,
CodeGen::CodeGenModule &M) const { }
/// Determines the size of struct _Unwind_Exception on this platform,
/// in 8-bit units. The Itanium ABI defines this as:
/// struct _Unwind_Exception {
/// uint64 exception_class;
/// _Unwind_Exception_Cleanup_Fn exception_cleanup;
/// uint64 private_1;
/// uint64 private_2;
/// };
virtual unsigned getSizeOfUnwindException() const;
/// Controls whether __builtin_extend_pointer should sign-extend
/// pointers to uint64_t or zero-extend them (the default). Has
/// no effect for targets:
/// - that have 64-bit pointers, or
/// - that cannot address through registers larger than pointers, or
/// - that implicitly ignore/truncate the top bits when addressing
/// through such registers.
virtual bool extendPointerWithSExt() const { return false; }
/// Determines the DWARF register number for the stack pointer, for
/// exception-handling purposes. Implements __builtin_dwarf_sp_column.
///
/// Returns -1 if the operation is unsupported by this target.
virtual int getDwarfEHStackPointer(CodeGen::CodeGenModule &M) const {
return -1;
}
/// Initializes the given DWARF EH register-size table, a char*.
/// Implements __builtin_init_dwarf_reg_size_table.
///
/// Returns true if the operation is unsupported by this target.
virtual bool initDwarfEHRegSizeTable(CodeGen::CodeGenFunction &CGF,
llvm::Value *Address) const {
return true;
}
/// Performs the code-generation required to convert a return
/// address as stored by the system into the actual address of the
/// next instruction that will be executed.
///
/// Used by __builtin_extract_return_addr().
virtual llvm::Value *decodeReturnAddress(CodeGen::CodeGenFunction &CGF,
llvm::Value *Address) const {
return Address;
}
/// Performs the code-generation required to convert the address
/// of an instruction into a return address suitable for storage
/// by the system in a return slot.
///
/// Used by __builtin_frob_return_addr().
virtual llvm::Value *encodeReturnAddress(CodeGen::CodeGenFunction &CGF,
llvm::Value *Address) const {
return Address;
}
virtual llvm::Type* adjustInlineAsmType(CodeGen::CodeGenFunction &CGF,
StringRef Constraint,
llvm::Type* Ty) const {
return Ty;
}
/// Retrieve the address of a function to call immediately before
/// calling objc_retainAutoreleasedReturnValue. The
/// implementation of objc_autoreleaseReturnValue sniffs the
/// instruction stream following its return address to decide
/// whether it's a call to objc_retainAutoreleasedReturnValue.
/// This can be prohibitively expensive, depending on the
/// relocation model, and so on some targets it instead sniffs for
/// a particular instruction sequence. This functions returns
/// that instruction sequence in inline assembly, which will be
/// empty if none is required.
virtual StringRef getARCRetainAutoreleasedReturnValueMarker() const {
return "";
}
/// Determine whether a call to an unprototyped functions under
/// the given calling convention should use the variadic
/// convention or the non-variadic convention.
///
/// There's a good reason to make a platform's variadic calling
/// convention be different from its non-variadic calling
/// convention: the non-variadic arguments can be passed in
/// registers (better for performance), and the variadic arguments
/// can be passed on the stack (also better for performance). If
/// this is done, however, unprototyped functions *must* use the
/// non-variadic convention, because C99 states that a call
/// through an unprototyped function type must succeed if the
/// function was defined with a non-variadic prototype with
/// compatible parameters. Therefore, splitting the conventions
/// makes it impossible to call a variadic function through an
/// unprototyped type. Since function prototypes came out in the
/// late 1970s, this is probably an acceptable trade-off.
/// Nonetheless, not all platforms are willing to make it, and in
/// particularly x86-64 bends over backwards to make the
/// conventions compatible.
///
/// The default is false. This is correct whenever:
/// - the conventions are exactly the same, because it does not
/// matter and the resulting IR will be somewhat prettier in
/// certain cases; or
/// - the conventions are substantively different in how they pass
/// arguments, because in this case using the variadic convention
/// will lead to C99 violations.
///
/// However, some platforms make the conventions identical except
/// for passing additional out-of-band information to a variadic
/// function: for example, x86-64 passes the number of SSE
/// arguments in %al. On these platforms, it is desireable to
/// call unprototyped functions using the variadic convention so
/// that unprototyped calls to varargs functions still succeed.
virtual bool isNoProtoCallVariadic(const CodeGen::CallArgList &args,
const FunctionNoProtoType *fnType) const;
};
}
#endif // CLANG_CODEGEN_TARGETINFO_H
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