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On Wednesday 30 April 2003 13:14, Falk Hueffner wrote: > gcc 3.4 will have a __builtin_ctz function which can be used for this. > It will emit special instructions on CPUs that support it (i386, Alpha > EV67), and use a lookup table on others, which is very boring, but > also faster. Actually, __builtin_clz: http://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html Not having a gcc 2.4 handy, I couldn't test it, but I did notice that the built-in ffs is very fast. Perhaps all such standard functions will end up as built-ins instead of kernel library functions, some very long time in the future. If old compilers ever do finally fade away, that is. It's somewhat annoying that __builtin_clz leaves the all-ones case dangling instead of returning -1. Regards, Daniel - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||
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