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cpuinfo: Use auxv for AltiVec on Linux if possible 

The SIGILL handler is not very reliable and can cause crashes.

Linux provides the CPU's AltiVec support status in getauxval.

(cherry picked from commit 7490471796)
This commit is contained in:
A. Wilcox 2025-05-04 15:01:25 -05:00 committed by Sam Lantinga
parent 50d02ad732
commit 434836c480
1 changed files with 3 additions and 1 deletions
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4
src/cpuinfo/SDL_cpuinfo.c
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@ -115,7 +115,7 @@
#define CPU_CFG2_LSX (1 << 6)
#define CPU_CFG2_LASX (1 << 7)
#if defined(SDL_ALTIVEC_BLITTERS) && defined(HAVE_SETJMP) && !defined(SDL_PLATFORM_MACOS) && !defined(SDL_PLATFORM_OPENBSD) && !defined(SDL_PLATFORM_FREEBSD)
#if defined(SDL_ALTIVEC_BLITTERS) && defined(HAVE_SETJMP) && !defined(SDL_PLATFORM_MACOS) && !defined(SDL_PLATFORM_OPENBSD) && !defined(SDL_PLATFORM_FREEBSD) && (defined(SDL_PLATFORM_LINUX) && !defined(HAVE_GETAUXVAL))
/* This is the brute force way of detecting instruction sets...
the idea is borrowed from the libmpeg2 library - thanks!
*/
@ -344,6 +344,8 @@ static int CPU_haveAltiVec(void)
elf_aux_info(AT_HWCAP, &cpufeatures, sizeof(cpufeatures));
altivec = cpufeatures & PPC_FEATURE_HAS_ALTIVEC;
return altivec;
#elif defined(SDL_PLATFORM_LINUX) && defined(__powerpc__) && defined(HAVE_GETAUXVAL)
altivec = getauxval(AT_HWCAP) & PPC_FEATURE_HAS_ALTIVEC;
#elif defined(SDL_ALTIVEC_BLITTERS) && defined(HAVE_SETJMP)
void (*handler)(int sig);
handler = signal(SIGILL, illegal_instruction);