How do you recognize a conditional move (cmov) and when does it replace an if-else?

cmovCC copies its source to its destination only when the condition holds — a branchless replacement for short if-else that avoids branch-misprediction stalls.

* cmovCC replaces a short if-else with a branchless copy-if-condition, avoiding branch-misprediction stalls. *

cmp  %esi, %edi
cmovl %esi, %edi

Means: "if %edi < %esi, then %edi = %esi" — i.e. whenever %edi is the smaller, replace it with %esi, so %edi ends up holding max(edi, esi).

Common uses:

Why branchless? The CPU executes cmov without a branch, avoiding branch misprediction penalties. Compilers use it for simple, short if-else where both paths are cheap.

All variants: cmove, cmovne, cmovl, cmovg, cmovle, cmovge, cmova, cmovb, etc. — same conditions as jCC jumps.

Go deeper:

• Wikipedia — Predication (computer architecture): conditional moves as a branchless alternative to conditional jumps.
• Intel SDM (felixcloutier): CMOVcc loads the source unconditionally into a temp, then copies to the destination only if the condition holds.