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- // Copyright 2020 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_YIELD_PROCESSOR_H_
- #define BASE_ALLOCATOR_PARTITION_ALLOCATOR_YIELD_PROCESSOR_H_
- #include "build/build_config.h"
- // The PA_YIELD_PROCESSOR macro wraps an architecture specific-instruction that
- // informs the processor we're in a busy wait, so it can handle the branch more
- // intelligently and e.g. reduce power to our core or give more resources to the
- // other hyper-thread on this core. See the following for context:
- // https://software.intel.com/en-us/articles/benefitting-power-and-performance-sleep-loops
- #if BUILDFLAG(IS_NACL)
- // Inline assembly not allowed.
- #define PA_YIELD_PROCESSOR ((void)0)
- #else
- #if defined(ARCH_CPU_X86_64) || defined(ARCH_CPU_X86)
- #define PA_YIELD_PROCESSOR __asm__ __volatile__("pause")
- #elif (defined(ARCH_CPU_ARMEL) && __ARM_ARCH >= 6) || defined(ARCH_CPU_ARM64)
- #define PA_YIELD_PROCESSOR __asm__ __volatile__("yield")
- #elif defined(ARCH_CPU_MIPSEL)
- // The MIPS32 docs state that the PAUSE instruction is a no-op on older
- // architectures (first added in MIPS32r2). To avoid assembler errors when
- // targeting pre-r2, we must encode the instruction manually.
- #define PA_YIELD_PROCESSOR __asm__ __volatile__(".word 0x00000140")
- #elif defined(ARCH_CPU_MIPS64EL) && __mips_isa_rev >= 2
- // Don't bother doing using .word here since r2 is the lowest supported mips64
- // that Chromium supports.
- #define PA_YIELD_PROCESSOR __asm__ __volatile__("pause")
- #elif defined(ARCH_CPU_PPC64_FAMILY)
- #define PA_YIELD_PROCESSOR __asm__ __volatile__("or 31,31,31")
- #elif defined(ARCH_CPU_S390_FAMILY)
- // just do nothing
- #define PA_YIELD_PROCESSOR ((void)0)
- #endif // ARCH
- #ifndef PA_YIELD_PROCESSOR
- #define PA_YIELD_PROCESSOR ((void)0)
- #endif
- #endif // BUILDFLAG(IS_NACL)
- #endif // BASE_ALLOCATOR_PARTITION_ALLOCATOR_YIELD_PROCESSOR_H_
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