How to detect Altivec availability on linux/ppc at runtime

It is easy to find information on how to detect the availability of the different SSE instructions sets on the x86 platform.. but this get trickier when you’re looking after AltiVec.

This page provide some code and a link explaining why methods based on try and catch exception are bad:

I did few modifications to this code, that I consider enhancements:

#include #include

// from
static inline bool altivecAvailable(void)
bool result = false;
unsigned long buf[64];
ssize_t count;
int fd, i;

fd = open(“/proc/self/auxv”, O_RDONLY);
if (fd < 0) { return false; } // loop on reading do { count = read(fd, buf, sizeof(buf)); if (count < 0){ break; for (i=0; i < (count / sizeof(unsigned long)); i += 2) { if (buf[i] == AT_HWCAP) { result = !!(buf[i+1] & PPC_FEATURE_HAS_ALTIVEC); goto out_close; } else if (buf[i] == AT_NULL) goto out_close; } } while (count == sizeof(buf)); out_close: close(fd); return result; } [/cpp]

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