http://benji3up2kxewkqfcq7buxk2xd6zwy3zggnurkrm3l4cvwy2iipvyyad.onion/mirrors/gmpdoc/Introduction-to-GMP.html
There is assembly code for these CPUs: ARM Cortex-A9, Cortex-A15, and generic ARM,
DEC Alpha 21064, 21164, and 21264,
AMD K8 and K10 (sold under many brands, e.g. Athlon64, Phenom, Opteron),
Bulldozer, and Bobcat,
Intel Pentium, Pentium Pro/II/III, Pentium 4, Core2, Nehalem, Sandy bridge, Haswell, generic x86,
Intel IA-64,
Motorola/IBM PowerPC 32 and 64 such as POWER970, POWER5, POWER6, and POWER7,
MIPS 32-bit and 64-bit,
SPARC 32-bit and 64-bit with special support for all UltraSPARC...