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loong64: Use HWCAP instead of CPUCFG to detect LSX/LASX

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Per the Software Development and Build Convention for LoongArch™
Architectures manual, on Linux we should use HWCAP instead of CPUCFG to
detect if LSX/LASX is available.  The reason is the kernel may be
configured to disable them, and CPUCFG cannot provide info about the
kernel support.

Change-Id: I3f1b23e6d4c91c7da81311fbbe294e36ff178121
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/6772567
Reviewed-by: Frank Barchard <fbarchard@chromium.org>
Reviewed-by: Wan-Teh Chang <wtc@google.com>
This commit is contained in:
Xi Ruoyao 2025-07-19 14:36:11 +08:00 committed by Frank Barchard
parent 96134e95a7
commit dd9ced1c6d
1 changed files with 9 additions and 10 deletions
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19
source/cpu_id.cc
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@ -23,7 +23,7 @@
#include <stdio.h> // For fopen()
#include <string.h>
#if defined(__linux__) && defined(__aarch64__)
#if defined(__linux__) && (defined(__aarch64__) || defined(__loongarch__))
#include <sys/auxv.h> // For getauxval()
#endif
@ -388,21 +388,20 @@ LIBYUV_API SAFEBUFFERS int MipsCpuCaps(const char* cpuinfo_name) {
return flag;
}
#define LOONGARCH_CFG2 0x2
#define LOONGARCH_CFG2_LSX (1 << 6)
#define LOONGARCH_CFG2_LASX (1 << 7)
#if defined(__loongarch__) && defined(__linux__)
// Define hwcap values ourselves: building with an old auxv header where these
// hwcap values are not defined should not prevent features from being enabled.
#define YUV_LOONGARCH_HWCAP_LSX (1 << 4)
#define YUV_LOONGARCH_HWCAP_LASX (1 << 5)
#if defined(__loongarch__)
LIBYUV_API SAFEBUFFERS int LoongarchCpuCaps(void) {
int flag = 0;
uint32_t cfg2 = 0;
unsigned long hwcap = getauxval(AT_HWCAP);
__asm__ volatile("cpucfg %0, %1 \n\t" : "+&r"(cfg2) : "r"(LOONGARCH_CFG2));
if (cfg2 & LOONGARCH_CFG2_LSX)
if (hwcap & YUV_LOONGARCH_HWCAP_LSX)
flag |= kCpuHasLSX;
if (cfg2 & LOONGARCH_CFG2_LASX)
if (hwcap & YUV_LOONGARCH_HWCAP_LASX)
flag |= kCpuHasLASX;
return flag;
}