1 //===-- Common internal contructs -------------------------------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef LLVM_LIBC_SRC___SUPPORT_COMMON_H 10 #define LLVM_LIBC_SRC___SUPPORT_COMMON_H 11 12 #ifndef LIBC_NAMESPACE 13 #error "LIBC_NAMESPACE macro is not defined." 14 #endif 15 16 #include "src/__support/macros/attributes.h" 17 #include "src/__support/macros/config.h" 18 #include "src/__support/macros/properties/architectures.h" 19 20 #ifndef LLVM_LIBC_FUNCTION_ATTR 21 #define LLVM_LIBC_FUNCTION_ATTR 22 #endif 23 24 // clang-format off 25 // Allow each function `func` to have extra attributes specified by defining: 26 // `LLVM_LIBC_FUNCTION_ATTR_func` macro, which should always start with 27 // "LLVM_LIBC_EMPTY, " 28 // 29 // For examples: 30 // #define LLVM_LIBC_FUNCTION_ATTR_memcpy LLVM_LIBC_EMPTY, [[gnu::weak]] 31 // #define LLVM_LIBC_FUNCTION_ATTR_memchr LLVM_LIBC_EMPTY, [[gnu::weak]] [[gnu::visibility("default")]] 32 // clang-format on 33 #define LLVM_LIBC_EMPTY 34 35 #define GET_SECOND(first, second, ...) second 36 #define EXPAND_THEN_SECOND(name) GET_SECOND(name, LLVM_LIBC_EMPTY) 37 38 #define LLVM_LIBC_ATTR(name) EXPAND_THEN_SECOND(LLVM_LIBC_FUNCTION_ATTR_##name) 39 40 // At the moment, [[gnu::alias()]] is not supported on MacOS, and it is needed 41 // to cleanly export and alias the C++ symbol `LIBC_NAMESPACE::func` with the C 42 // symbol `func`. So for public packaging on MacOS, we will only export the C 43 // symbol. Moreover, a C symbol `func` in macOS is mangled as `_func`. 44 #if defined(LIBC_COPT_PUBLIC_PACKAGING) 45 #ifndef __APPLE__ 46 #define LLVM_LIBC_FUNCTION_IMPL(type, name, arglist) \ 47 LLVM_LIBC_ATTR(name) \ 48 LLVM_LIBC_FUNCTION_ATTR decltype(LIBC_NAMESPACE::name) \ 49 __##name##_impl__ __asm__(#name); \ 50 decltype(LIBC_NAMESPACE::name) name [[gnu::alias(#name)]]; \ 51 type __##name##_impl__ arglist 52 #else // __APPLE__ 53 #define LLVM_LIBC_FUNCTION_IMPL(type, name, arglist) \ 54 LLVM_LIBC_ATTR(name) \ 55 LLVM_LIBC_FUNCTION_ATTR decltype(LIBC_NAMESPACE::name) name asm("_" #name); \ 56 type name arglist 57 #endif // __APPLE__ 58 #else // LIBC_COPT_PUBLIC_PACKAGING 59 #define LLVM_LIBC_FUNCTION_IMPL(type, name, arglist) type name arglist 60 #endif // LIBC_COPT_PUBLIC_PACKAGING 61 62 // This extra layer of macro allows `name` to be a macro to rename a function. 63 #define LLVM_LIBC_FUNCTION(type, name, arglist) \ 64 LLVM_LIBC_FUNCTION_IMPL(type, name, arglist) 65 66 namespace LIBC_NAMESPACE_DECL { 67 namespace internal { 68 LIBC_INLINE constexpr bool same_string(char const *lhs, char const *rhs) { 69 for (; *lhs || *rhs; ++lhs, ++rhs) 70 if (*lhs != *rhs) 71 return false; 72 return true; 73 } 74 } // namespace internal 75 } // namespace LIBC_NAMESPACE_DECL 76 77 #define __LIBC_MACRO_TO_STRING(str) #str 78 #define LIBC_MACRO_TO_STRING(str) __LIBC_MACRO_TO_STRING(str) 79 80 // LLVM_LIBC_IS_DEFINED checks whether a particular macro is defined. 81 // Usage: constexpr bool kUseAvx = LLVM_LIBC_IS_DEFINED(__AVX__); 82 // 83 // This works by comparing the stringified version of the macro with and without 84 // evaluation. If FOO is not undefined both stringifications yield "FOO". If FOO 85 // is defined, one stringification yields "FOO" while the other yields its 86 // stringified value "1". 87 #define LLVM_LIBC_IS_DEFINED(macro) \ 88 !LIBC_NAMESPACE::internal::same_string( \ 89 LLVM_LIBC_IS_DEFINED__EVAL_AND_STRINGIZE(macro), #macro) 90 #define LLVM_LIBC_IS_DEFINED__EVAL_AND_STRINGIZE(s) #s 91 92 #endif // LLVM_LIBC_SRC___SUPPORT_COMMON_H 93