GNU MP 4.1.2
16.8 Assembler Coding
The assembler subroutines in GMP are the most significant source of speed at
small to moderate sizes. At larger sizes algorithm selection becomes more
important, but of course speedups in low level routines will still speed up
everything proportionally.
Carry handling and widening multiplies that are important for GMP can't be
easily expressed in C. GCC asm blocks help a lot and are provided in
`longlong.h', but hand coding low level routines invariably offers a
speedup over generic C by a factor of anything from 2 to 10.
