GMP 6.1.2 t-count_zeros failure on ARM with assertions

Niels Möller nisse at
Tue Jan 2 08:49:29 UTC 2018

tg at (Torbjörn Granlund) writes:

> We might define these directly, at least for arm64, to CLZ and RBIT+CLZ,
> respectively, instead of using gcc's builtin semi-defined variants?

Using inline asm instead has the drawback that it leaves a little less
opportunity for the compiler to schedule this instructions optimally. No
idea if that matters in practice. Since it seems we don't really need
count_*_zeros to support zero input, is there any advantage in using
inline asm?

(Related, I wonder what the effect would be of redefining umul_ppmm as C
expressions involving __uint128_t on compilers that support that).


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