libc/src/__support/common.h

   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/properties/architectures.h"
  18
  19 #ifndef LLVM_LIBC_FUNCTION_ATTR
  20 #define LLVM_LIBC_FUNCTION_ATTR
  21 #endif
  22
  23 // MacOS needs to be excluded because it does not support aliasing.
  24 #if defined(LIBC_COPT_PUBLIC_PACKAGING) && (!defined(__APPLE__))
  25 #define LLVM_LIBC_FUNCTION_IMPL(type, name, arglist)                           \
  26   LLVM_LIBC_FUNCTION_ATTR decltype(LIBC_NAMESPACE::name)                       \
  27       __##name##_impl__ __asm__(#name);                                        \
  28   decltype(LIBC_NAMESPACE::name) name [[gnu::alias(#name)]];                   \
  29   type __##name##_impl__ arglist
  30 #else
  31 #define LLVM_LIBC_FUNCTION_IMPL(type, name, arglist) type name arglist
  32 #endif
  33
  34 // This extra layer of macro allows `name` to be a macro to rename a function.
  35 #define LLVM_LIBC_FUNCTION(type, name, arglist)                                \
  36   LLVM_LIBC_FUNCTION_IMPL(type, name, arglist)
  37
  38 namespace LIBC_NAMESPACE {
  39 namespace internal {
  40 LIBC_INLINE constexpr bool same_string(char const *lhs, char const *rhs) {
  41   for (; *lhs || *rhs; ++lhs, ++rhs)
  42     if (*lhs != *rhs)
  43       return false;
  44   return true;
  45 }
  46 } // namespace internal
  47 } // namespace LIBC_NAMESPACE
  48
  49 #define __LIBC_MACRO_TO_STRING(str) #str
  50 #define LIBC_MACRO_TO_STRING(str) __LIBC_MACRO_TO_STRING(str)
  51
  52 // LLVM_LIBC_IS_DEFINED checks whether a particular macro is defined.
  53 // Usage: constexpr bool kUseAvx = LLVM_LIBC_IS_DEFINED(__AVX__);
  54 //
  55 // This works by comparing the stringified version of the macro with and without
  56 // evaluation. If FOO is not undefined both stringifications yield "FOO". If FOO
  57 // is defined, one stringification yields "FOO" while the other yields its
  58 // stringified value "1".
  59 #define LLVM_LIBC_IS_DEFINED(macro)                                            \
  60   !LIBC_NAMESPACE::internal::same_string(                                      \
  61       LLVM_LIBC_IS_DEFINED__EVAL_AND_STRINGIZE(macro), #macro)
  62 #define LLVM_LIBC_IS_DEFINED__EVAL_AND_STRINGIZE(s) #s
  63
  64 #endif // LLVM_LIBC_SRC___SUPPORT_COMMON_H