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util: add auxv based PowerPC AltiVec/VSX detection

Browse source 
At least on Linux, we can use the ELF auxiliary vector to
detect the presence of AltiVec, VSX and other CPU features
without having to go through handling SIGILL, which has
various problems of its own.

A similar thing is already being done for ARM to detect NEON.

Reviewed-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Daniel Kolesa <daniel@octaforge.org>
This commit is contained in:
Daniel Kolesa 2019-08-27 21:47:48 +02:00 • committed by Matt Turner
parent 23f42f8dcf
commit 1b9fce56c4
1 changed files with 25 additions and 4 deletions
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29
src/util/u_cpu_detect.c
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@ -92,7 +92,7 @@ static int has_cpuid(void);
#endif
#if defined(PIPE_ARCH_PPC) && !defined(PIPE_OS_APPLE)
#if defined(PIPE_ARCH_PPC) && !defined(PIPE_OS_APPLE) && !defined(PIPE_OS_LINUX)
static jmp_buf __lv_powerpc_jmpbuf;
static volatile sig_atomic_t __lv_powerpc_canjump = 0;
@ -126,8 +126,29 @@ check_os_altivec_support(void)
util_cpu_caps.has_altivec = 1;
}
}
#else /* !PIPE_OS_APPLE */
/* not on Apple/Darwin, do it the brute-force way */
#elif defined(PIPE_OS_LINUX) /* !PIPE_OS_APPLE */
#if defined(PIPE_ARCH_PPC_64)
Elf64_auxv_t aux;
#else
Elf32_auxv_t aux;
#endif
int fd = open("/proc/self/auxv", O_RDONLY | O_CLOEXEC);
if (fd >= 0) {
while (read(fd, &aux, sizeof(aux)) == sizeof(aux)) {
if (aux.a_type == AT_HWCAP) {
char *env_vsx = getenv("GALLIVM_VSX");
uint64_t hwcap = aux.a_un.a_val;
util_cpu_caps.has_altivec = (hwcap >> 28) & 1;
if (!env_vsx || env_vsx[0] != '0') {
util_cpu_caps.has_vsx = (hwcap >> 7) & 1;
}
break;
}
}
close(fd);
}
#else /* !PIPE_OS_APPLE && !PIPE_OS_LINUX */
/* not on Apple/Darwin or Linux, do it the brute-force way */
/* this is borrowed from the libmpeg2 library */
signal(SIGILL, sigill_handler);
if (setjmp(__lv_powerpc_jmpbuf)) {
@ -171,7 +192,7 @@ check_os_altivec_support(void)
util_cpu_caps.has_altivec = 0;
}
}
#endif /* !PIPE_OS_APPLE */
#endif /* !PIPE_OS_APPLE && !PIPE_OS_LINUX */
}
#endif /* PIPE_ARCH_PPC */