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util/cpu: Teach the Linux code about getauxval()

Browse source 
In addition to being nicer to read this is also slightly more efficient
since it doesn't need to open a file.

Reviewed-by: Marek Olšák <maraeo@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34820>
This commit is contained in:
Adam Jackson 2025-05-05 11:05:54 -04:00 • committed by Marge Bot
parent 1ef9cd3504
commit 0ffbfa1d54
1 changed files with 11 additions and 66 deletions
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77
src/util/u_cpu_detect.c
View file

@ -67,6 +67,7 @@
#endif
#if DETECT_OS_LINUX
#include <sys/auxv.h>
#include <signal.h>
#include <fcntl.h>
#include <elf.h>
@ -169,26 +170,11 @@ check_os_altivec_support(void)
}
}
#elif DETECT_OS_LINUX /* !DETECT_OS_APPLE && !DETECT_OS_NETBSD && !DETECT_OS_OPENBSD */
#if DETECT_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);
}
char *env_vsx = getenv("GALLIVM_VSX");
uint64_t hwcap = getauxval(AT_HWCAP);
util_cpu_caps.has_altivec = (hwcap >> 28) & 1;
if (!env_vsx || env_vsx[0] != '0') {
util_cpu_caps.has_vsx = (hwcap >> 7) & 1;
#else /* !DETECT_OS_APPLE && !DETECT_OS_BSD && !DETECT_OS_LINUX */
/* not on Apple/Darwin or Linux, do it the brute-force way */
/* this is borrowed from the libmpeg2 library */
@ -421,21 +407,7 @@ check_os_arm_support(void)
util_cpu_caps.has_neon = 1;
}
#elif DETECT_OS_LINUX
Elf32_auxv_t aux;
int fd;
fd = open("/proc/self/auxv", O_RDONLY | O_CLOEXEC);
if (fd >= 0) {
while (read(fd, &aux, sizeof(Elf32_auxv_t)) == sizeof(Elf32_auxv_t)) {
if (aux.a_type == AT_HWCAP) {
uint32_t hwcap = aux.a_un.a_val;
util_cpu_caps.has_neon = (hwcap >> 12) & 1;
break;
}
}
close (fd);
}
util_cpu_caps.has_neon = (getauxval(AT_HWCAP) >> 12) & 1;
#endif /* DETECT_OS_LINUX */
}
@ -452,21 +424,7 @@ static void
check_os_mips64_support(void)
{
#if DETECT_OS_LINUX
Elf64_auxv_t aux;
int fd;
fd = open("/proc/self/auxv", O_RDONLY | O_CLOEXEC);
if (fd >= 0) {
while (read(fd, &aux, sizeof(Elf64_auxv_t)) == sizeof(Elf64_auxv_t)) {
if (aux.a_type == AT_HWCAP) {
uint64_t hwcap = aux.a_un.a_val;
util_cpu_caps.has_msa = (hwcap >> 1) & 1;
break;
}
}
close (fd);
}
util_cpu_caps.has_msa = (getauxval(AT_HWCAP) >> 1) & 1;
#endif /* DETECT_OS_LINUX */
}
#endif /* DETECT_ARCH_MIPS64 */
@ -476,22 +434,9 @@ static void
check_os_loongarch64_support(void)
{
#if DETECT_OS_LINUX
Elf64_auxv_t aux;
int fd;
fd = open("/proc/self/auxv", O_RDONLY | O_CLOEXEC);
if (fd >= 0) {
while (read(fd, &aux, sizeof(Elf64_auxv_t)) == sizeof(Elf64_auxv_t)) {
if (aux.a_type == AT_HWCAP) {
uint64_t hwcap = aux.a_un.a_val;
util_cpu_caps.has_lsx = (hwcap >> 4) & 1;
util_cpu_caps.has_lasx = (hwcap >> 5) & 1;
break;
}
}
close (fd);
}
uint64_t hwcap = getauxval(AT_HWCAP);
util_cpu_caps.has_lsx = (hwcap >> 4) & 1;
util_cpu_caps.has_lasx = (hwcap >> 5) & 1;
#endif /* DETECT_OS_LINUX */
}
#endif /* DETECT_ARCH_LOONGARCH64 */