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qsimd: simplify the code slightly

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Only x86 requires more than 32 different bits in the CPU feature
variable, so enforce the need for 64-bit atomics only for it. Everyone
else can stick to 32-bit atomics, which are supported everywhere.

Change-Id: I54f205f6b7314351b078fffd16cf7c7d50a84102
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
This commit is contained in:
Thiago Macieira 2022-01-31 14:47:46 -08:00
parent d9f1d2c9df
commit d08f59d083
2 changed files with 7 additions and 16 deletions
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13
src/corelib/global/qsimd.cpp
View File

@ -1,7 +1,7 @@
/**************************************************************************** /****************************************************************************
** **
** Copyright (C) 2016 The Qt Company Ltd. ** Copyright (C) 2021 The Qt Company Ltd.
** Copyright (C) 2019 Intel Corporation. ** Copyright (C) 2022 Intel Corporation.
** Contact: https://www.qt.io/licensing/ ** Contact: https://www.qt.io/licensing/
** **
** This file is part of the QtCore module of the Qt Toolkit. ** This file is part of the QtCore module of the Qt Toolkit.
@ -583,11 +583,7 @@ static const int features_count = (sizeof features_indices) / (sizeof features_i
// record what CPU features were enabled by default in this Qt build // record what CPU features were enabled by default in this Qt build
static const quint64 minFeature = qCompilerCpuFeatures; static const quint64 minFeature = qCompilerCpuFeatures;
#ifdef Q_ATOMIC_INT64_IS_SUPPORTED QBasicAtomicInteger<QCpuFeatureType> qt_cpu_features[1] = { 0 };
Q_CORE_EXPORT QBasicAtomicInteger<quint64> qt_cpu_features[1] = { Q_BASIC_ATOMIC_INITIALIZER(0) };
#else
Q_CORE_EXPORT QBasicAtomicInteger<unsigned> qt_cpu_features[2] = { Q_BASIC_ATOMIC_INITIALIZER(0), Q_BASIC_ATOMIC_INITIALIZER(0) };
#endif
quint64 qDetectCpuFeatures() quint64 qDetectCpuFeatures()
{ {
@ -626,9 +622,6 @@ quint64 qDetectCpuFeatures()
} }
qt_cpu_features[0].storeRelaxed(f | quint32(QSimdInitialized)); qt_cpu_features[0].storeRelaxed(f | quint32(QSimdInitialized));
#ifndef Q_ATOMIC_INT64_IS_SUPPORTED
qt_cpu_features[1].storeRelaxed(f >> 32);
#endif
return f; return f;
} }

10
src/corelib/global/qsimd_p.h
View File

@ -357,11 +357,12 @@ static const quint64 qCompilerCpuFeatures = 0
; ;
#endif #endif
#ifdef Q_ATOMIC_INT64_IS_SUPPORTED #ifdef Q_PROCESSOR_X86
extern Q_CORE_EXPORT QBasicAtomicInteger<quint64> qt_cpu_features[1]; using QCpuFeatureType = quint64;
#else #else
extern Q_CORE_EXPORT QBasicAtomicInteger<unsigned> qt_cpu_features[2]; using QCpuFeatureType = unsigned;
#endif #endif
extern Q_CORE_EXPORT QBasicAtomicInteger<QCpuFeatureType> qt_cpu_features[1];
Q_CORE_EXPORT quint64 qDetectCpuFeatures(); Q_CORE_EXPORT quint64 qDetectCpuFeatures();
#if defined(Q_PROCESSOR_X86) && QT_COMPILER_SUPPORTS_HERE(RDRND) && !defined(QT_BOOTSTRAPPED) #if defined(Q_PROCESSOR_X86) && QT_COMPILER_SUPPORTS_HERE(RDRND) && !defined(QT_BOOTSTRAPPED)
@ -376,9 +377,6 @@ static inline qsizetype qRandomCpu(void *, qsizetype) noexcept
static inline quint64 qCpuFeatures() static inline quint64 qCpuFeatures()
{ {
quint64 features = qt_cpu_features[0].loadRelaxed(); quint64 features = qt_cpu_features[0].loadRelaxed();
#ifndef Q_ATOMIC_INT64_IS_SUPPORTED
features |= quint64(qt_cpu_features[1].loadRelaxed()) << 32;
#endif
if (Q_UNLIKELY(features == 0)) { if (Q_UNLIKELY(features == 0)) {
features = qDetectCpuFeatures(); features = qDetectCpuFeatures();
Q_ASSUME(features != 0); Q_ASSUME(features != 0);