Why is uint_least16_t faster than uint_fast16_t for multiplication in x86_64?

Question

The C standard is quite unclear about the uint_fast*_t family of types. On a gcc-4.4.4 linux x86_64 system, the types uint_fast16_t and uint_

Answer 1

Yes, I think this is simply a mistake. Unfortunately you can't just go fixing mistakes like this without breaking the ABI, but it may not matter since virtually nobody (and certainly no library functions I know of) actually uses the *int_fast*_t types.