| 1 | // Copyright (C) 2023 The Qt Company Ltd. |
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| 2 | // Copyright (C) 2023 Intel Corporation. |
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| 3 | // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only |
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| 4 | |
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| 5 | #ifndef QYIELDCPU_H |
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| 6 | #define QYIELDCPU_H |
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| 7 | |
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| 8 | #include <QtCore/qcompilerdetection.h> |
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| 9 | #include <QtCore/qprocessordetection.h> |
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| 10 | #include <QtCore/qtconfigmacros.h> |
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| 11 | |
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| 12 | #ifdef Q_CC_MSVC_ONLY |
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| 13 | // MSVC defines _YIELD_PROCESSOR() in <xatomic.h>, but as that is a private |
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| 14 | // header, we include the public ones |
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| 15 | # ifdef __cplusplus |
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| 16 | # include <atomic> |
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| 17 | extern "C" |
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| 18 | # endif |
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| 19 | void _mm_pause(void); // the compiler recognizes as intrinsic |
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| 20 | #endif |
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| 21 | |
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| 22 | QT_BEGIN_NAMESPACE |
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| 23 | |
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| 24 | #ifdef Q_CC_GNU |
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| 25 | __attribute__((artificial)) |
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| 26 | #endif |
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| 27 | Q_ALWAYS_INLINE void qYieldCpu(void) Q_DECL_NOEXCEPT; |
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| 28 | |
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| 29 | void qYieldCpu(void) |
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| 30 | #ifdef __cplusplus |
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| 31 | noexcept |
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| 32 | #endif |
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| 33 | { |
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| 34 | #if __has_builtin(__yield) |
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| 35 | __yield(); // Generic |
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| 36 | #elif defined(_YIELD_PROCESSOR) && defined(Q_CC_MSVC) |
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| 37 | _YIELD_PROCESSOR(); // Generic; MSVC's <atomic> |
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| 38 | |
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| 39 | #elif __has_builtin(__builtin_ia32_pause) |
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| 40 | __builtin_ia32_pause(); |
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| 41 | #elif defined(Q_PROCESSOR_X86) && defined(Q_CC_GNU) |
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| 42 | // GCC < 10 didn't have __has_builtin() |
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| 43 | __builtin_ia32_pause(); |
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| 44 | #elif defined(Q_PROCESSOR_X86) && defined(Q_CC_MSVC) |
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| 45 | _mm_pause(); |
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| 46 | #elif defined(Q_PROCESSOR_X86) |
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| 47 | __asm__("pause" ); // hopefully asm() works in this compiler |
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| 48 | |
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| 49 | #elif __has_builtin(__builtin_arm_yield) |
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| 50 | __builtin_arm_yield(); |
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| 51 | #elif defined(Q_PROCESSOR_ARM) && Q_PROCESSOR_ARM >= 7 && defined(Q_CC_GNU) |
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| 52 | __asm__("yield" ); // this works everywhere |
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| 53 | |
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| 54 | #elif defined(Q_PROCESSOR_RISCV) |
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| 55 | __asm__(".word 0x0100000f" ); // a.k.a. "pause" |
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| 56 | |
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| 57 | #elif defined(_YIELD_PROCESSOR) && defined(Q_CC_GHS) |
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| 58 | _YIELD_PROCESSOR; // Green Hills (INTEGRITY), but only on ARM |
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| 59 | #endif |
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| 60 | } |
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| 61 | |
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| 62 | QT_END_NAMESPACE |
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| 63 | |
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| 64 | #endif // QYIELDCPU_H |
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| 65 | |
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