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unix: implement cpu_relax() on ppc64

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We also tell the compiler it is not allowed to reorder the PAUSE 
instruction relative to other instructions. It is a mostly theoretical 
issue, but better safe than sorry.

PR-URL: https://github.com/libuv/libuv/pull/2590
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Jameson Nash <vtjnash@gmail.com>
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Ben Noordhuis 2021-06-19 05:47:24 +02:00 committed by GitHub
parent 9918a17438
commit 963ecc82d0
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1 changed files with 4 additions and 2 deletions
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src/unix/atomic-ops.h
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@ -52,9 +52,11 @@ UV_UNUSED(static int cmpxchgi(int* ptr, int oldval, int newval)) {
UV_UNUSED(static void cpu_relax(void)) {
#if defined(__i386__) || defined(__x86_64__)
__asm__ __volatile__ ("rep; nop"); /* a.k.a. PAUSE */
__asm__ __volatile__ ("rep; nop" ::: "memory"); /* a.k.a. PAUSE */
#elif (defined(__arm__) && __ARM_ARCH >= 7) || defined(__aarch64__)
__asm__ volatile("yield");
__asm__ __volatile__ ("yield" ::: "memory");
#elif defined(__powerpc64__) || defined(__ppc64__) || defined(__PPC64__)
__asm__ __volatile__ ("or 1,1,1; or 2,2,2" ::: "memory");
#endif
}