Embed Notice

Finding many things that are just sort of It's Assumed You Know This but may or may not be written anywhere. Like, there's a "movb" instruction which is not in the instruction reference I'm using and is not recognized by my syntax highlighter, but gas accepts it.

Question. I do

mov %al, %esi

It says operand type mismatch. OK. I think I can simulate this with

mov $0, %rax
mov $eax, $esi

BC non-al bits of rax get cleared in instruction 1.

…But what's the "widening"/truncating version of mov?