hints.h

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//
// Copyright 2016 Pixar
//
// Licensed under the Apache License, Version 2.0 (the "Apache License")
// with the following modification; you may not use this file except in
// compliance with the Apache License and the following modification to it:
// Section 6. Trademarks. is deleted and replaced with:
//
// 6. Trademarks. This License does not grant permission to use the trade
//    names, trademarks, service marks, or product names of the Licensor
//    and its affiliates, except as required to comply with Section 4(c) of
//    the License and to reproduce the content of the NOTICE file.
//
// You may obtain a copy of the Apache License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the Apache License with the above modification is
// distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the Apache License for the specific
// language governing permissions and limitations under the Apache License.
//
#ifndef PXR_BASE_ARCH_HINTS_H
#define PXR_BASE_ARCH_HINTS_H

#include "pxr/base/arch/defines.h"

/// \file arch/hints.h
/// Compiler hints.
///
/// \c ARCH_LIKELY(bool-expr) and \c ARCH_UNLIKELY(bool-expr) will evaluate to
/// the value of bool-expr but will also emit compiler intrinsics providing
/// hints for branch prediction if the compiler has such intrinsics.  It is
/// advised that you only use these in cases where you empirically know the
/// outcome of bool-expr to a very high degree of certainty.  For example,
/// fatal-error cases, invariants, first-time initializations, etc.

#if defined(ARCH_COMPILER_GCC) || defined(ARCH_COMPILER_CLANG)

#define ARCH_LIKELY(x) (__builtin_expect((bool)(x), true))
#define ARCH_UNLIKELY(x) (__builtin_expect((bool)(x), false))

#else

#define ARCH_LIKELY(x) (x)
#define ARCH_UNLIKELY(x) (x)

#endif

#endif // PXR_BASE_ARCH_HINTS_H