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//===---- TargetInfo.h - Encapsulate target details -------------*- 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
//
//===----------------------------------------------------------------------===//
//
// These classes wrap the information about a call or function definition used
// to handle ABI compliancy.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CLANG_LIB_CIR_TARGETINFO_H
#define LLVM_CLANG_LIB_CIR_TARGETINFO_H
#include "ABIInfo.h"
#include "CIRGenTypes.h"
#include <memory>
#include <utility>
namespace clang::CIRGen {
/// isEmptyFieldForLayout - Return true if the field is "empty", that is,
/// either a zero-width bit-field or an isEmptyRecordForLayout.
bool isEmptyFieldForLayout(const ASTContext &context, const FieldDecl *fd);
/// isEmptyRecordForLayout - Return true if a structure contains only empty
/// base classes (per isEmptyRecordForLayout) and fields (per
/// isEmptyFieldForLayout). Note, C++ record fields are considered empty
/// if the [[no_unique_address]] attribute would have made them empty.
bool isEmptyRecordForLayout(const ASTContext &context, QualType t);
class TargetCIRGenInfo {
std::unique_ptr<ABIInfo> info;
public:
TargetCIRGenInfo(std::unique_ptr<ABIInfo> info) : info(std::move(info)) {}
virtual ~TargetCIRGenInfo() = default;
/// Returns ABI info helper for the target.
const ABIInfo &getABIInfo() const { return *info; }
/// 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 desirable to
/// call unprototyped functions using the variadic convention so
/// that unprototyped calls to varargs functions still succeed.
///
/// Relatedly, platforms which pass the fixed arguments to this:
/// A foo(B, C, D);
/// differently than they would pass them to this:
/// A foo(B, C, D, ...);
/// may need to adjust the debugger-support code in Sema to do the
/// right thing when calling a function with no know signature.
virtual bool isNoProtoCallVariadic(const FunctionNoProtoType *fnType) const;
};
std::unique_ptr<TargetCIRGenInfo> createX8664TargetCIRGenInfo(CIRGenTypes &cgt);
} // namespace clang::CIRGen
#endif // LLVM_CLANG_LIB_CIR_TARGETINFO_H
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