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