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/*
* Copyright (c) 2021 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef SYSTEM_WRAPPERS_INCLUDE_DENORMAL_DISABLER_H_
#define SYSTEM_WRAPPERS_INCLUDE_DENORMAL_DISABLER_H_
#include "rtc_base/system/arch.h"
namespace webrtc {
// Activates the hardware (HW) way to flush denormals (see [1]) to zero as they
// can very seriously impact performance. At destruction time restores the
// denormals handling state read by the ctor; hence, supports nested calls.
// Equals a no-op if the architecture is not x86 or ARM or if the compiler is
// not CLANG.
// [1] https://en.wikipedia.org/wiki/Denormal_number
//
// Example usage:
//
// void Foo() {
// DenormalDisabler d;
// ...
// }
class DenormalDisabler {
public:
// Ctor. If architecture and compiler are supported, stores the HW settings
// for denormals, disables denormals and sets `disabling_activated_` to true.
// Otherwise, only sets `disabling_activated_` to false.
DenormalDisabler();
// Ctor. Same as above, but also requires `enabled` to be true to disable
// denormals.
explicit DenormalDisabler(bool enabled);
DenormalDisabler(const DenormalDisabler&) = delete;
DenormalDisabler& operator=(const DenormalDisabler&) = delete;
// Dtor. If `disabling_activated_` is true, restores the denormals HW settings
// read by the ctor before denormals were disabled. Otherwise it's a no-op.
~DenormalDisabler();
// Returns true if architecture and compiler are supported.
static bool IsSupported();
private:
const int status_word_;
const bool disabling_activated_;
};
} // namespace webrtc
#endif // SYSTEM_WRAPPERS_INCLUDE_DENORMAL_DISABLER_H_
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