libc/src/__support/macros/optimization.h

   1 //===-- Portable optimization macros ----------------------------*- 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 // This header file defines portable macros for performance optimization.
   9
  10 #ifndef LLVM_LIBC_SRC_SUPPORT_MACROS_OPTIMIZATION_H
  11 #define LLVM_LIBC_SRC_SUPPORT_MACROS_OPTIMIZATION_H
  12
  13 #include "src/__support/macros/attributes.h"          // LIBC_INLINE
  14 #include "src/__support/macros/config.h"              // LIBC_HAS_BUILTIN
  15 #include "src/__support/macros/properties/compiler.h" // LIBC_COMPILER_IS_CLANG
  16
  17 // We use a template to implement likely/unlikely to make sure that we don't
  18 // accidentally pass an integer.
  19 namespace __llvm_libc::details {
  20 template <typename T>
  21 LIBC_INLINE constexpr bool expects_bool_condition(T value, T expected) {
  22   return __builtin_expect(value, expected);
  23 }
  24 } // namespace __llvm_libc::details
  25 #define LIBC_LIKELY(x) __llvm_libc::details::expects_bool_condition(x, true)
  26 #define LIBC_UNLIKELY(x) __llvm_libc::details::expects_bool_condition(x, false)
  27
  28 #if defined(LIBC_COMPILER_IS_CLANG)
  29 #define LIBC_LOOP_NOUNROLL _Pragma("nounroll")
  30 #elif defined(LIBC_COMPILER_IS_GCC)
  31 #define LIBC_LOOP_NOUNROLL _Pragma("GCC unroll 0")
  32 #else
  33 #error "Unhandled compiler"
  34 #endif
  35
  36 #endif /* LLVM_LIBC_SRC_SUPPORT_MACROS_OPTIMIZATION_H */