---
title: Condition Operations
TARGET DECK: Obsidian::STEM
FILE TAGS: x86-64
tags:
- x86-64
---
## Overview
A number of instructions operate with respect to the [[registers#Condition Codes|condition code registers]].
## CMP and TEST
| Instruction | Operands | Based On | Description |
| ------------ | ---------- | --------------------- | ----------- |
| `cmp[bwlq]` | $S_1, S_2$ | $S_2 - S_1$ | Compare |
| `test[bwlq]` | $S_1, S_2$ | $S_1 \mathop{\&} S_2$ | Test |
%%ANKI
Basic
What four variants do `CMP` instructions take on in x86-64?
Back: `cmpb`, `cmpw`, `cmpl`, `cmpq`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What instruction class is `CMP` "based" on?
Back: `SUB`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What registers does `CMP` affect?
Back: The condition code registers.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What distinguishes `CMP` from `SUB`?
Back: `CMP` does not update any destinations.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
How does Bryant et al. recommend reading `CMP` instructions?
Back: As subtracting the first operand *from* the second.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What instruction class is `TEST` "based" on?
Back: `AND`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What distinguishes `TEST` from `AND`?
Back: `TEST` does not update any destinations.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What four variants do `TEST` instructions take on in x86-64?
Back: `testb`, `testw`, `testl`, `testq`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{1:`CMP`} is to {2:`SUB`} as {2:`TEST`} is to {1:`AND`}.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What registers does `TEST` affect?
Back: The condition code registers.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
## SET
The description of the `SET` commands apply to the case of a comparison instruction. That is, the condition codes are set according to computation `t = a - b`, where `t`, `a`, and `b` may be interpreted as signed or unsigned depending on the `SET` instruction invoked.
| Instruction | Synonym | Evaluation | Description |
| ----------- | -------- | ---------------------------- | ------------------------------ |
| `sete` | `setz` | `ZF` | Equal / zero |
| `setne` | `setnz` | `~ZF` | Not equal / not zero |
| `sets` | | `SF` | Negative |
| `setns` | | `~SF` | Nonnegative |
| `setl` | `setnge` | `SF ^ OF` | Less (signed `<`) |
| `setle` | `setng` | (SF ^ OF) \| ZF
| Less or equal (signed `<=`) |
| `setg` | `setnle` | `~(SF ^ OF) & ~ZF` | Greater (signed `>`) |
| `setge` | `setnl` | `~(SF ^ OF)` | Greater or equal (signed `<=`) |
| `setb` | `setnae` | `CF` | Below (unsigned `<`) |
| `setbe` | `setna` | CF \| ZF
| Below or equal (unsigned `<=`) |
| `seta` | `setnbe` | `~CF & ~ZF` | Above (unsigned `>`) |
| `setae` | `setnb` | `~CF` | Above or equal (unsigned `>=`) |
Note how the other condition code evaluations are easy to derive from `setl` and `setb`.
%%ANKI
Basic
What arithmetic computation is a `SET` instruction's description based on?
Back: `t = a - b`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What value does a `SET` instruction assign to a destination?
Back: $0$ or $1$
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
How large is the destination of a `SET` instruction?
Back: A single byte.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What is `q` in the `cmpq` instruction short for?
Back: **Q**uad word.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What is `e` in the `sete` instruction short for?
Back: **E**qual.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What is `z` in the `setz` instruction short for?
Back: **Z**ero.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{`sete`} is a synonym for {`setz`}.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What is `ne` in the `setne` instruction short for?
Back: **N**ot **e**qual.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What is `nz` in the `setnz` instruction short for?
Back: **N**ot **z**ero.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{`setne`} is a synonym for {`setnz`}.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What is `s` in the `sets` instruction short for?
Back: **S**igned.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What is `ns` in the `setns` instruction short for?
Back: **N**ot **s**igned.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{`set[ez]`} is to {`ZF`} whereas {`sets`} is to {`SF`}.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What condition code(s) does `sete` refer to?
Back: `ZF`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
In terms of condition codes, what value does `setz` put in its specified destination?
Back: `ZF`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What condition code(s) does `setnz` refer to?
Back: `ZF`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
In terms of condition codes, what value does `setne` put in its specified destination?
Back: `~ZF`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What condition code(s) does `sets` refer to?
Back: `SF`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
In terms of condition codes, what value does `sets` put in its specified destination?
Back: `SF`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What condition code(s) does `setns` refer to?
Back: `SF`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
In terms of condition codes, what value does `setns` put in its specified destination?
Back: `~SF`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What is `l` in the `setl` instruction short for?
Back: **L**ess.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{`setl`} is a synonym for {`setnge`}.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What is `nge` in the `setnge` instruction short for?
Back: **N**ot **g**reater or **e**qual.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What is `b` in the `setb` instruction short for?
Back: **B**elow.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{`setb`} is a synonym for {`setnae`}.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What is `nae` in the `setnae` instruction short for?
Back: **N**ot **a**bove or **e**qual.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{1:`setl`} is to {2:signed} integers whereas {2:`setb`} is to {1:unsigned} integers.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{1:`setnae`} is to {2:unsigned} integers whereas {2:`setnge`} is to {1:signed} integers.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What condition code(s) does `setl` refer to?
Back: `SF` and `OF`.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
In terms of condition codes, what value does `setl` put in its specified destination?
Back: `SF ^ OF`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What condition code(s) does `setb` refer to?
Back: `CF`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
In terms of condition codes, what value does `setb` put in its specified destination?
Back: `CF`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What is `le` in the `setle` instruction short for?
Back: **L**ess or **e**qual.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{`setle`} is a synonym for {`setng`}.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{1:`setle`} is to {2:signed} integers whereas {2:`setbe`} is to {1:unsigned} integers.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{1:`setna`} is to {2:unsigned} integers whereas {2:`setng`} is to {1:signed} integers.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What condition code(s) does `setle` refer to?
Back: `SF`, `OF`, and `ZF`.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
In terms of condition codes, what value does `setle` put in its specified destination?
Back: `(SF ^ OF) | ZF`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What is `g` in the `setg` instruction short for?
Back: **G**reater.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{`setg`} is a synonym for {`setnle`}.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{1:`setg`} is to {2:signed} integers whereas {2:`seta`} is to {1:unsigned} integers.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{1:`setnle`} is to {2:signed} integers whereas {2:`setnbe`} is to {1:unsigned} integers.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What condition code(s) does `setg` refer to?
Back: `SF`, `OF`, and `ZF`.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
In terms of condition codes, what value does `setg` put in its specified destination?
Back: `~(SF ^ OF) & ~ZF`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What is `ge` in the `setge` instruction short for?
Back: **G**reater or **e**qual.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{`setge`} is a synonym for {`setnl`}.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{1:`setge`} is to {2:signed} integers whereas {2:`setae`} is to {1:unsigned} integers.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{1:`setnb`} is to {2:unsigned} integers whereas {2:`setnl`} is to {1:signed} integers.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What condition code(s) does `setge` refer to?
Back: `SF` and `OF`.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
In terms of condition codes, what value does `setge` put in its specified destination?
Back: `~(SF ^ OF)`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What is `a` in the `seta` instruction short for?
Back: **A**bove.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{`seta`} is a synonym for {`setnbe`}.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What condition code(s) does `seta` refer to?
Back: `CF` and `ZF`.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
In terms of condition codes, what value does `seta` put in its specified destination?
Back: `~CF & ~ZF`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What is `ae` in the `setae` instruction short for?
Back: **A**bove or **e**qual.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{`setae`} is a synonym for {`setnb`}.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What condition code(s) does `setae` refer to?
Back: `CF`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
In terms of condition codes, what value does `setae` put in its specified destination?
Back: `~CF`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What is `be` in the `setbe` instruction short for?
Back: **B**elow or **e**qual.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Cloze
{`setbe`} is a synonym for {`setna`}.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
What condition code(s) does `setbe` refer to?
Back: `CF` and `ZF`.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
%%ANKI
Basic
In terms of condition codes, what value does `setbe` put in its specified destination?
Back: `CF | ZF`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
## Bibliography
* Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.