AND faster than integer modulo operation?

Question

It is possible to re-express:

• i % m

as:

• i & (m-1)

where,

• i is an unsigned integer
• m is a po

Answer 1

You may be interested in Embedded Live: Embedded Programmers' Guide to ARM’s Cortex-M Architecture.

The ARM Cortex-M family has unsigned and singed division instructions, UDIV and SDIV, which take 2 to 12 cycles. There is no MOD instruction, but equivalent result is obtained by a {S,U}DIV followed by the multiply-and-subtract instruction MLS, which takes 2 cycles, for a total of 4-14 cycles.

The AND instruction is single cycle, therefore 4-14x faster.