c6abf6cd3f
Some API deprecation -- ExperimentalAgc and ExperimentalNs are gone. We're continuing to carry iSAC even though it's gone upstream, but maybe we'll want to drop that soon.
112 lines
3.7 KiB
C++
112 lines
3.7 KiB
C++
/*
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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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#include "system_wrappers/include/denormal_disabler.h"
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#include "rtc_base/checks.h"
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namespace webrtc {
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namespace {
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#if defined(WEBRTC_ARCH_X86_FAMILY) && defined(__clang__)
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#define WEBRTC_DENORMAL_DISABLER_X86_SUPPORTED
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#endif
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#if defined(WEBRTC_DENORMAL_DISABLER_X86_SUPPORTED) || \
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defined(WEBRTC_ARCH_ARM_FAMILY)
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#define WEBRTC_DENORMAL_DISABLER_SUPPORTED
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#endif
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constexpr int kUnspecifiedStatusWord = -1;
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#if defined(WEBRTC_DENORMAL_DISABLER_SUPPORTED)
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// Control register bit mask to disable denormals on the hardware.
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#if defined(WEBRTC_DENORMAL_DISABLER_X86_SUPPORTED)
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// On x86 two bits are used: flush-to-zero (FTZ) and denormals-are-zero (DAZ).
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constexpr int kDenormalBitMask = 0x8040;
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#elif defined(WEBRTC_ARCH_ARM_FAMILY)
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// On ARM one bit is used: flush-to-zero (FTZ).
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constexpr int kDenormalBitMask = 1 << 24;
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#endif
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// Reads the relevant CPU control register and returns its value for supported
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// architectures and compilers. Otherwise returns `kUnspecifiedStatusWord`.
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int ReadStatusWord() {
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int result = kUnspecifiedStatusWord;
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#if defined(WEBRTC_DENORMAL_DISABLER_X86_SUPPORTED)
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asm volatile("stmxcsr %0" : "=m"(result));
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#elif defined(WEBRTC_ARCH_ARM_FAMILY) && defined(WEBRTC_ARCH_32_BITS)
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asm volatile("vmrs %[result], FPSCR" : [result] "=r"(result));
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#elif defined(WEBRTC_ARCH_ARM_FAMILY) && defined(WEBRTC_ARCH_64_BITS)
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asm volatile("mrs %x[result], FPCR" : [result] "=r"(result));
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#endif
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return result;
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}
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// Writes `status_word` in the relevant CPU control register if the architecture
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// and the compiler are supported.
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void SetStatusWord(int status_word) {
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#if defined(WEBRTC_DENORMAL_DISABLER_X86_SUPPORTED)
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asm volatile("ldmxcsr %0" : : "m"(status_word));
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#elif defined(WEBRTC_ARCH_ARM_FAMILY) && defined(WEBRTC_ARCH_32_BITS)
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asm volatile("vmsr FPSCR, %[src]" : : [src] "r"(status_word));
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#elif defined(WEBRTC_ARCH_ARM_FAMILY) && defined(WEBRTC_ARCH_64_BITS)
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asm volatile("msr FPCR, %x[src]" : : [src] "r"(status_word));
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#endif
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}
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// Returns true if the status word indicates that denormals are enabled.
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constexpr bool DenormalsEnabled(int status_word) {
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return (status_word & kDenormalBitMask) != kDenormalBitMask;
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}
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#endif // defined(WEBRTC_DENORMAL_DISABLER_SUPPORTED)
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} // namespace
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#if defined(WEBRTC_DENORMAL_DISABLER_SUPPORTED)
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DenormalDisabler::DenormalDisabler() : DenormalDisabler(/*enabled=*/true) {}
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DenormalDisabler::DenormalDisabler(bool enabled)
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: status_word_(enabled ? ReadStatusWord() : kUnspecifiedStatusWord),
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disabling_activated_(enabled && DenormalsEnabled(status_word_)) {
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if (disabling_activated_) {
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RTC_DCHECK_NE(status_word_, kUnspecifiedStatusWord);
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SetStatusWord(status_word_ | kDenormalBitMask);
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RTC_DCHECK(!DenormalsEnabled(ReadStatusWord()));
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}
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}
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bool DenormalDisabler::IsSupported() {
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return true;
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}
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DenormalDisabler::~DenormalDisabler() {
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if (disabling_activated_) {
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RTC_DCHECK_NE(status_word_, kUnspecifiedStatusWord);
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SetStatusWord(status_word_);
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}
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}
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#else
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DenormalDisabler::DenormalDisabler() : DenormalDisabler(/*enabled=*/false) {}
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DenormalDisabler::DenormalDisabler(bool enabled)
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: status_word_(kUnspecifiedStatusWord), disabling_activated_(false) {}
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bool DenormalDisabler::IsSupported() {
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return false;
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}
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DenormalDisabler::~DenormalDisabler() = default;
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#endif
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} // namespace webrtc
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