i propose some instructions as participants to the most usefull instruction post.

0: adc

1: mov

2: jmp

3: call/ret

4: push/pop

5: feel free to propose your team of most usefull instructions


i made the adc instruction the most usefull because of many reasons.
i think it is possible to emulate a lot of instructions with functions made only with adc...

lea, shr/shl, ror/rol, add/sub, inc/dec, cmp and int3 jk

That's a different topic: http://en.wikipedia.org/wiki/One_instruction_set_computer
Yes you can only use a single instruction, but looking at some statistics, http://www.strchr.com/x86_machine_code_statistics mov is the most useful in everyday computing.

Personally I love LEA and if its not the most useful it definitely is the most powerful instruction.

EDIT by DOS386 (2011-08-17) : fixed broken link

I like:

SETxx
CMOVxx

These allow for branch-less code.

CMOVxx-like instructions would be truly cool if there was a possibility to move immediate values.

I agree, CMOVxx could be very useful if it were to allow more options. Shuffling all the registers around makes my head hurt and it doesn't usually give any performance benefits.

My first thought was lea

http://board.flatassembler.net/topic.php?t=5249 "top 20"
http://board.flatassembler.net/topic.php?t=13027 "useless"

> the most usefull instruction

LOADALL286

> CMOVxx-like instructions would be truly cool if there was a
> possibility to move immediate values.

And even more if added in 80386 or even better in 8086, and if not PageFaulting if condition is false

of course the most usefull instruction is nop

garanteed to never produce unpredictable results

can sprinkle liberaly through code and replace with single byte interrupt for tracing and debuging