697 lines
23 KiB
Markdown
697 lines
23 KiB
Markdown
---
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title: Procedures
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TARGET DECK: Obsidian::STEM
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FILE TAGS: x86-64
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tags:
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- x86-64
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---
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## Overview
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The x86-64 stack grows towards lower addresses. When a procedure is invoked, more spack on the top of the stack is allocated for that procedure to make use of. This portion of the stack is called a **frame**. The general shape of the stack looks as follows:
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![[x86-64-stack.png]]
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Note parts of this diagram are omitted when possible. For instance, a stack frame may not exist at all if all arguments to a **leaf procedure** can be passed through registers. A leaf procedure is a function that does not call another function.
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%%ANKII
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Basic
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What ADT is used internally in procedure-calling mechanisms?
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Back: A stack.
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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%%
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%%ANKII
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Cloze
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The x86-64 stack grows towards {lower} addresses.
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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%%
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%%ANKI
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Basic
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What is a frame w.r.t. the x86-64 stack?
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Back: A region of the stack dedicated to a particular function call.
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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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<!--ID: 1728480337611-->
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END%%
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%%ANKI
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Basic
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What instructions are used to store and retrieve from the x86-64 stack?
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Back: `pushq` and `popq`.
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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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<!--ID: 1728480337614-->
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END%%
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%%ANKI
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Basic
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What does the "stack pointer" refer to w.r.t. the x86-64 stack?
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Back: Register `%rsp`.
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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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<!--ID: 1728480337617-->
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END%%
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%%ANKI
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Basic
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How is the stack pointer manipulated to allocate space on the x86-64 stack?
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Back: By decrementing `%rsp` by an appropriate amount.
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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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<!--ID: 1728480337621-->
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END%%
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%%ANKI
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Basic
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How is the stack pointer manipulated to deallocate space on the x86-64 stack?
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Back: By incrementing `%rsp` by an appropriate amount.
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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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<!--ID: 1728480337604-->
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END%%
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%%ANKI
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Basic
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Suppose procedure `P` calls `Q`. What data sits at the end of `P`'s frame?
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Back: A return address.
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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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<!--ID: 1728481058927-->
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END%%
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%%ANKI
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Cloze
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A {leaf} procedure is a function that {does not call another function}.
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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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<!--ID: 1728481058953-->
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END%%
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%%ANKI
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Basic
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Suppose procedure `P` calls `Q`. The return address belongs to who's frame?
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Back: `P`
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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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<!--ID: 1728481058960-->
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END%%
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%%ANKI
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Basic
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Suppose procedure `P` calls `Q`. Why is the return address considered to be in `P`'s frame?
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Back: It is state relevant to `P`.
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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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<!--ID: 1728481058966-->
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END%%
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%%ANKI
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Basic
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`Q` is about to call another procedure. What is the highlighted portion of its stack frame for?
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![[saved-registers.png]]
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Back: Callee-saved registers.
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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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<!--ID: 1730121604350-->
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END%%
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%%ANKI
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Basic
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`Q` is about to call another procedure. What is the highlighted portion of its stack frame for?
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![[local-variables.png]]
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Back: Local variables.
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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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<!--ID: 1730121604358-->
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END%%
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%%ANKI
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Basic
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`Q` is about to call another procedure. What is the highlighted portion of its stack frame for?
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![[arg-build-area.png]]
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Back: Additional integral arguments.
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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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<!--ID: 1730121604401-->
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END%%
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%%ANKI
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Basic
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What must still be added to the stack before `Q` passes control to another procedure?
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![[stack-frame.png]]
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Back: The return address.
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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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<!--ID: 1730121604407-->
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END%%
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## CALL and RET
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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.
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| Instruction | Operands | Description |
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| ----------- | ----------- | ---------------- |
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| `call` | Label | Procedure call |
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| `call` | \**Operand* | Procedure call |
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| `ret` | | Return from call |
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%%ANKI
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Cloze
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The {`call`} instruction is the counterpart to the {`ret`} instruction.
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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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<!--ID: 1728558288130-->
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END%%
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%%ANKI
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Basic
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What two things does the `call` instruction do?
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Back: It pushes the return address on the stack and updates the PC.
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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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<!--ID: 1728558288148-->
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END%%
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%%ANKI
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Basic
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What two things does the `ret` instruction do?
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Back: It pops the return address off the stack and updates the PC.
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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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<!--ID: 1728558288160-->
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END%%
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%%ANKI
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Basic
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The operand forms of `call` mirror what other instruction class?
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Back: `JMP`
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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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<!--ID: 1728558288165-->
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END%%
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%%ANKI
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Basic
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A `call` instruction pushes what address onto the stack?
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Back: That of the instruction following the `call` instruction.
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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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<!--ID: 1728558288171-->
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END%%
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%%ANKI
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Basic
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What return address is pushed onto the stack after `call` is run?
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```x86
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1: ...
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2: callq .L1
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3: ...
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```
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Back: `3`
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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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<!--ID: 1728558288177-->
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END%%
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%%ANKI
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Basic
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What address is the PC updated to after `call` is run?
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```x86
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1: ...
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2: callq .L1
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3: ...
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```
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Back: That corresponding to label `.L1`.
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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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<!--ID: 1728558288183-->
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END%%
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%%ANKI
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Basic
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Which register(s) does a `call` instruction update?
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Back: `%rsp` and `%rip`.
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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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<!--ID: 1728559336730-->
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END%%
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%%ANKI
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Basic
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Which register(s) does a `ret` instruction update?
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Back: `%rsp` and `%rip`.
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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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<!--ID: 1728559336760-->
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END%%
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## Local Storage
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### On the Stack
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x86-64 employs 6 registers for passing integral (i.e. integer and pointer) arguments between caller and callee.
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| Bits | Arg 1 | Arg2 | Arg3 | Arg4 | Arg5 | Arg6 |
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| ---- | ------ | ------ | ------ | ------ | ------ | ------ |
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| 64 | `%rdi` | `%rsi` | `%rdx` | `%rcx` | `%r8` | `%r9` |
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| 32 | `%edi` | `%esi` | `%edx` | `%ecx` | `%r8d` | `%r9d` |
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| 16 | `%di` | `%si` | `%dx` | `%cx` | `%r8w` | `%r9w` |
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| 8 | `%dil` | `%sil` | `%dl` | `%cl` | `%r8b` | `%r9b` |
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If more than 6 integral arguments are specified to a procedure, the surplus are placed onto the stack in the caller's frame. The 7th argument is placed closer to the top of the stack (i.e. with lower address) than subsequent arguments.
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%%ANKI
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Basic
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How many registers are available for passing integral arguments between procedures?
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Back: `6`
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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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<!--ID: 1728559336766-->
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END%%
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%%ANKI
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Cloze
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By convention, register {`%rdi`} is used for {the first integral argument}.
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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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<!--ID: 1728559336787-->
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END%%
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%%ANKI
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Basic
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Which register should the first integral argument of a procedure be placed in?
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Back: `%rdi`
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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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<!--ID: 1728559336817-->
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END%%
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%%ANKI
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Cloze
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By convention, register {`%rsi`} is used for {the second integral argument}.
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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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<!--ID: 1728559336847-->
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END%%
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%%ANKI
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Basic
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Which register should the second integral argument of a procedure be placed in?
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Back: `%rsi`
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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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<!--ID: 1728559336872-->
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END%%
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%%ANKI
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Basic
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From smallest to largest, list the four "second integral argument" registers.
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Back: `%sil`, `%si`, `%esi`, and `%rsi`.
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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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<!--ID: 1730120342193-->
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END%%
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%%ANKI
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Cloze
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{1:`%rdi`} is to the {2:first} integral argument whereas {2:`%rsi`} is to the {1:second} integral argument.
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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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<!--ID: 1728559336879-->
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END%%
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%%ANKI
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Cloze
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By convention, register {`%rdx`} is used for {the third integral argument}.
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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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<!--ID: 1729533668338-->
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END%%
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%%ANKI
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Basic
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Which register should the third integral argument of a procedure be placed in?
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Back: `%rdx`
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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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<!--ID: 1729533668358-->
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END%%
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%%ANKI
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Cloze
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By convention, register {`%rcx`} is used for {the fourth integral argument}.
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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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<!--ID: 1729641729193-->
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END%%
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%%ANKI
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Basic
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Which register should the fourth integral argument of a procedure be placed in?
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Back: `%rcx`
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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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<!--ID: 1729641729214-->
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END%%
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%%ANKI
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Basic
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Which register should `Q` use to access value `1`?
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```c
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void P() {
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Q(1, 2, 3, 4, 5, 6);
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}
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```
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Back: `%rdi`
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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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<!--ID: 1729810820710-->
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END%%
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%%ANKI
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Basic
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Which register should `Q` use to access value `2`?
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```c
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void P() {
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Q(1, 2, 3, 4, 5, 6);
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}
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```
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Back: `%rsi`
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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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<!--ID: 1729810820713-->
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END%%
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%%ANKI
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Basic
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Which register should `Q` use to access value `3`?
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```c
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void P() {
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Q(1, 2, 3, 4, 5, 6);
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}
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```
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Back: `%rdx`
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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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<!--ID: 1729810820715-->
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END%%
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%%ANKI
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Basic
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Which register should `Q` use to access value `4`?
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```c
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void P() {
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Q(1, 2, 3, 4, 5, 6);
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}
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```
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Back: `%rcx`
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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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<!--ID: 1729810820718-->
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END%%
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%%ANKI
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Basic
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Let $S$ denote `%rsp` before pushing parameter `int a` onto the stack. What is `%rsp` now?
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Back: $S - 8$
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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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<!--ID: 1730119064915-->
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END%%
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%%ANKI
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Basic
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Let $S$ denote `%rsp` before pushing parameter `short a` onto the stack. What is `%rsp` now?
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Back: $S - 8$
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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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<!--ID: 1730119064921-->
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END%%
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%%ANKI
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Basic
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Let $S$ denote `%rsp` before pushing parameter `bool a` onto the stack. What is `%rsp` now?
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Back: $S - 8$
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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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<!--ID: 1730119064924-->
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END%%
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%%ANKI
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Basic
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After calling `Q`, how much space do local parameters occupy in `P`'s stack frame?
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```c
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void P() {
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Q(1, 2, 3, 4, 5, 6);
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}
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```
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Back: 0 bytes.
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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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<!--ID: 1730119064928-->
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END%%
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%%ANKI
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Basic
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After calling `Q`, how much space do local parameters occupy in `P`'s stack frame?
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```c
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void P() {
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Q(1, 2, 3, 4, 5, 6, 7, 8);
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}
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```
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Back: 16 bytes.
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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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<!--ID: 1730119064931-->
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END%%
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%%ANKI
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Basic
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After calling `Q`, how much space do local parameters occupy in `P`'s stack frame?
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```c
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void P() {
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Q(1, 2, 3, 4, 5, 6, true, 8);
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}
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```
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Back: 16 bytes.
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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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<!--ID: 1730119064934-->
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END%%
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%%ANKI
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Basic
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Which frame contains the 7th argument?
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```c
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void P() {
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...
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Q(1, 2, 3, 4, 5, 6, 7);
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...
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}
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```
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Back: `P`'s frame.
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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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Tags: c17
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<!--ID: 1729810820635-->
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END%%
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%%ANKI
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Basic
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Which frame contains the return address?
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```c
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void P() {
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...
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Q(1, 2, 3);
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...
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}
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```
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Back: `P`'s frame.
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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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Tags: c17
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<!--ID: 1729811536734-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Which of the 7th or 8th argument has lower address?
|
|
```c
|
|
void P() {
|
|
...
|
|
Q(1, 2, 3, 4, 5, 6, 7, 8);
|
|
...
|
|
}
|
|
```
|
|
Back: The 7th argument.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
Tags: c17
|
|
<!--ID: 1729808568349-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Which of the 7th or 8th argument is nearer the stack's top?
|
|
```c
|
|
void P() {
|
|
...
|
|
Q(1, 2, 3, 4, 5, 6, 7, 8);
|
|
...
|
|
}
|
|
```
|
|
Back: The 7th argument.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
Tags: c17
|
|
<!--ID: 1729810820663-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Which arguments are placed onto the stack?
|
|
```c
|
|
void P() {
|
|
...
|
|
Q(1, 2, 3, 4, 5, 6, 7, 8);
|
|
...
|
|
}
|
|
```
|
|
Back: Arguments 7 and 8.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
Tags: c17
|
|
<!--ID: 1729810820678-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Which of the 6th or 7th argument is nearer the stack's top?
|
|
```c
|
|
void P() {
|
|
...
|
|
Q(1, 2, 3, 4, 5, 6, 7);
|
|
...
|
|
}
|
|
```
|
|
Back: N/A. Argument 6 isn't placed onto the stack at all.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
Tags: c17
|
|
<!--ID: 1729808568354-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Which of the 7th argument or the return address is nearer the stack's top?
|
|
```c
|
|
void P() {
|
|
...
|
|
Q(1, 2, 3, 4, 5, 6, 7);
|
|
...
|
|
}
|
|
```
|
|
Back: The return address.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
Tags: c17
|
|
<!--ID: 1729808568358-->
|
|
END%%
|
|
|
|
In some cases, integral values still need to be placed onto the stack. For example, operator `&` is applied to a local variable and hence we must be able to generate an address for it.
|
|
|
|
%%ANKI
|
|
Cloze
|
|
In the following, `P` is the {caller} and `Q` is the {callee}.
|
|
```c
|
|
int P() { Q(); }
|
|
```
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
Tags: c17
|
|
<!--ID: 1729810820682-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
*Why* doesn't `P` have to allocate any local variables on the stack?
|
|
```c
|
|
void P() {
|
|
int a = 100;
|
|
Q(a);
|
|
}
|
|
```
|
|
Back: A register can be set to immediate `$100` for `Q` to access.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
Tags: c17
|
|
<!--ID: 1729810820698-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
*Why* doesn't `P` have to allocate any local variables on the stack?
|
|
```c
|
|
void P() {
|
|
int a = 100;
|
|
Q(&a);
|
|
}
|
|
```
|
|
Back: N/A. It does since we need an address for `a` to supply to `Q`.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
Tags: c17
|
|
<!--ID: 1729810820701-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Is `P`'s local stack variables or arguments to `Q` nearer the stack's top?
|
|
```c
|
|
void P() {
|
|
...
|
|
Q(1, 2, 3, 4, 5, 6);
|
|
...
|
|
}
|
|
```
|
|
Back: N/A. `P` does not have any arguments passed to `Q` on the stack.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
Tags: c17
|
|
<!--ID: 1729811536739-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Is `P`'s local stack variables or arguments to `Q` nearer the stack's top?
|
|
```c
|
|
void P() {
|
|
...
|
|
Q(1, 2, 3, 4, 5, 6, 7);
|
|
...
|
|
}
|
|
```
|
|
Back: The arguments to `Q`.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
Tags: c17
|
|
<!--ID: 1729811536743-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Which registers are designated for argument passing?
|
|
Back: `%rdi`, `%rsi`, `%rdx`, `%rcx`, and `%r8-%r9`.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1730120207052-->
|
|
END%%
|
|
|
|
### In Registers
|
|
|
|
x86-64 employs 6 registers as callee-saved registers. If procedure `P` calls procedure `Q`, `Q` *must* preserve the values of these registers. That is, if `Q` were to modify these registers, `Q` is also responsible for restoring these values before returning back to `P`.
|
|
|
|
| Bits | | | | | | |
|
|
| ---- | ------ | ------ | ------- | ------- | ------- | ------- |
|
|
| 64 | `%rbx` | `%rbp` | `%r12` | `%r13` | `%r14` | `%r15` |
|
|
| 32 | `%ebx` | `%ebp` | `%r12d` | `%r13d` | `%r14d` | `%r15d` |
|
|
| 16 | `%bx` | `%bp` | `%r12w` | `%r13w` | `%r14w` | `%r15w` |
|
|
| 8 | `%bl` | `%bpl` | `%r12b` | `%r13b` | `%r14b` | `%15b` |
|
|
|
|
%%ANKI
|
|
Basic
|
|
Which registers are designated as callee-saved?
|
|
Back: `%rbx`, `%rbp`, and `%r12-%r15`.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1730120207058-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
How many registers are designated as callee-saved?
|
|
Back: 6.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1730121604414-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
*What* is a callee-saved register?
|
|
Back: A register whose value must be preserved by a callee on return.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1730120207062-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Cloze
|
|
By convention, register `%rbp` is used for {callee-saved values}.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1730121604421-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Suppose `P` calls `Q`. Callee-saved registers are in which stack frame?
|
|
Back: `Q`'s.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1730121604427-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Suppose `P` calls `Q` with 8 integral arguments. Which of `P`'s callee-saved values or arguments to `Q` are nearer the stack's top?
|
|
Back: `P`'s arguments to `Q`.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1730121604434-->
|
|
END%%
|
|
|
|
## Bibliography
|
|
|
|
* Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|