The details of procedures are detailed in [[x86-64/procedures|procedures]]. This file touches on the most relevant instruction classes.
## CALL and RET
Like [[conditions#JMP|JMP]] instructions, `call` allows specifying a direct or indirect operand. `call` pushes the address of the instruction following it onto the stack and updates the PC to the operand. `ret` reverts these steps.
| Instruction | Operands | Description |
| ----------- | ----------- | ---------------- |
| `call` | Label | Procedure call |
| `call` | \**Operand* | Procedure call |
| `ret` | | Return from call |
%%ANKI
Cloze
The {`call`} instruction is the counterpart to the {`ret`} instruction.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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%%ANKI
Basic
What two things does the `call` instruction do?
Back: It pushes the return address on the stack and updates the PC.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Basic
What two things does the `ret` instruction do?
Back: It pops the return address off the stack and updates the PC.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Basic
How is `ret` equivalently written using a line of assembly?
Back:
```asm
popq %rip
```
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Basic
The operand forms of `call` mirror what other instruction class?
Back: `JMP`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Basic
A `call` instruction pushes what address onto the stack?
Back: That of the instruction following the `call` instruction.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Basic
What return address is pushed onto the stack after `call` is run?
```x86
1: ...
2: callq .L1
3: ...
```
Back: `3`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Basic
What address is the PC updated to after `call` is run?
```x86
1: ...
2: callq .L1
3: ...
```
Back: That corresponding to label `.L1`.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Basic
Which register(s) does a `call` instruction update?
Back: `%rsp` and `%rip`.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Basic
Which register(s) does a `ret` instruction update?
Back: `%rsp` and `%rip`.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
## LEAVE
`leave` parallels the `ret` instruction. It is equivalent to the following two instructions:
```asm
movq %rbp, %rsp
popq %rbp
```
%%ANKI
Basic
What two things does the `leave` instruction do?
Back: Restores the stack pointer and pops off the caller-saved base pointer.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Basic
How is `leave` equivalently written using a pair of instructions?
Back:
```asm
movq %rbp, %rsp
popq %rbp
```
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Basic
Fixed-sized frames use which of `leave` and/or `ret`?
Back: Just `ret`.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Basic
Variable-sized frames use which of `leave` and/or `ret`?
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
%%ANKI
Cloze
{1:`ret`} is to {2:`%rsp`} whereas {2:`leave`} is to {1:`%rbp`}.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
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END%%
## Bibliography
* Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
