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_SUPPORT_COMMON_H
  10 #define LLVM_LIBC_SUPPORT_COMMON_H
  11
  12 #include "src/__support/macros/attributes.h"
  13 #include "src/__support/macros/properties/architectures.h"
  14
  15 #ifndef LLVM_LIBC_FUNCTION_ATTR
  16 #define LLVM_LIBC_FUNCTION_ATTR
  17 #endif
  18
  19 // GPU targets do not support aliasing.
  20 #if defined(LIBC_COPT_PUBLIC_PACKAGING) && defined(LIBC_TARGET_ARCH_IS_GPU)
  21 #define LLVM_LIBC_FUNCTION_IMPL(type, name, arglist)                           \
  22   LLVM_LIBC_FUNCTION_ATTR decltype(__llvm_libc::name)                          \
  23       __##name##_impl__ __asm__(#name);                                        \
  24   type __##name##_impl__ arglist
  25 // MacOS needs to be excluded because it does not support aliasing.
  26 #elif defined(LIBC_COPT_PUBLIC_PACKAGING) && (!defined(__APPLE__))
  27 #define LLVM_LIBC_FUNCTION_IMPL(type, name, arglist)                           \
  28   LLVM_LIBC_FUNCTION_ATTR decltype(__llvm_libc::name)                          \
  29       __##name##_impl__ __asm__(#name);                                        \
  30   decltype(__llvm_libc::name) name [[gnu::alias(#name)]];                      \
  31   type __##name##_impl__ arglist
  32 #else
  33 #define LLVM_LIBC_FUNCTION_IMPL(type, name, arglist) type name arglist
  34 #endif
  35
  36 // This extra layer of macro allows `name` to be a macro to rename a function.
  37 #define LLVM_LIBC_FUNCTION(type, name, arglist)                                \
  38   LLVM_LIBC_FUNCTION_IMPL(type, name, arglist)
  39
  40 namespace __llvm_libc {
  41 namespace internal {
  42 constexpr bool same_string(char const *lhs, char const *rhs) {
  43   for (; *lhs || *rhs; ++lhs, ++rhs)
  44     if (*lhs != *rhs)
  45       return false;
  46   return true;
  47 }
  48 } // namespace internal
  49 } // namespace __llvm_libc
  50
  51 // LLVM_LIBC_IS_DEFINED checks whether a particular macro is defined.
  52 // Usage: constexpr bool kUseAvx = LLVM_LIBC_IS_DEFINED(__AVX__);
  53 //
  54 // This works by comparing the stringified version of the macro with and without
  55 // evaluation. If FOO is not undefined both stringifications yield "FOO". If FOO
  56 // is defined, one stringification yields "FOO" while the other yields its
  57 // stringified value "1".
  58 #define LLVM_LIBC_IS_DEFINED(macro)                                            \
  59   !__llvm_libc::internal::same_string(                                         \
  60       LLVM_LIBC_IS_DEFINED__EVAL_AND_STRINGIZE(macro), #macro)
  61 #define LLVM_LIBC_IS_DEFINED__EVAL_AND_STRINGIZE(s) #s
  62
  63 #endif // LLVM_LIBC_SUPPORT_COMMON_H