performance - Is ADD 1 really faster than INC ? x86

Question

This question already has answers here:

Answer 1

On some micro-architectures, with some instruction streams, INC will incur a "partial flags update stall" (because it updates some of the flags while preserving the others). ADD sets the value of all of the flags, and so does not risk such a stall.

ADD is not always faster than INC, but it is almost always at least as fast (there are a few corner cases on certain older micro-architectures, but they are exceedingly rare), and sometimes significantly faster.

For more details, consult Intel's Optimization Reference Manual or Agner Fog's micro-architecture notes.