413 lines
14 KiB
Markdown
413 lines
14 KiB
Markdown
---
|
|
title: Arithmetic Operations
|
|
TARGET DECK: Obsidian::STEM
|
|
FILE TAGS: x86-64
|
|
tags:
|
|
- x86-64
|
|
---
|
|
|
|
### Load Effective Address
|
|
|
|
| Instruction | Operands | Effect | Description |
|
|
| ----------- | -------- | ------- | ---------------------- |
|
|
| `leaq` | S, D | D <- &S | Load effective address |
|
|
|
|
`leaq` is a variant of MOV. The first operand appears to be a memory address, but instead of reading from the designated location, the instruction copies the effective address to the designated location (a register).
|
|
|
|
%%ANKI
|
|
Basic
|
|
`leaq` is considered a variant of what other instruction class?
|
|
Back: `MOV`
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1715780601450-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Why is the `leaq` instruction named the way it is?
|
|
Back: It stands for **l**oad **e**ffective **a**ddress.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1715780601455-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Cloze
|
|
The {`leaq`} instruction is to x86-64 as the {`&`} operator is to C.
|
|
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: 1715780601458-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Which x86-64 instruction is used to generate pointers?
|
|
Back: `leaq`
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1715780601461-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Why doesn't `leaq` have any other size variants?
|
|
Back: x96-64 addresses are always 64-bit.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1715780601464-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Suppose `%rdx` contains $x$. Use `leaq` to set `%rax` to $5x + 7$.
|
|
Back: `leaq 7(%rdx, %rdx, 4), %rax`
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1715780601467-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Besides effective memory computations, how else is `leaq` used?
|
|
Back: For certain arithmetic operations.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1715780601469-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Assume `%rdx` holds $q$. What is the value of `%rax` in the following?
|
|
```asm
|
|
leaq 9(%rdx),%rax
|
|
```
|
|
Back: $9 + q$
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1715781031929-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Assume `%rbx` holds $p$ and `%rdx` holds $q$. What is the value of `%rax` in the following?
|
|
```asm
|
|
leaq (%rdx, %rbx),%rax
|
|
```
|
|
Back: $q + q$
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1715781031935-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Assume `%rbx` holds $p$. What is the value of `%rax` in the following?
|
|
```asm
|
|
leaq 2(%rbx, %rbx, 7),%rax
|
|
```
|
|
Back: $2 + 8p$
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1715781031938-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Assume `%rdx` holds $q$. What is the value of `%rax` in the following?
|
|
```asm
|
|
leaq 0xE(, %rdx, 3),%rax
|
|
```
|
|
Back: $14 + 3q$
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1715781031941-->
|
|
END%%
|
|
|
|
### Unary Operations
|
|
|
|
| Instruction | Operands | Effect | Description |
|
|
| ----------- | -------- | ---------- | ----------- |
|
|
| `inc[bwlq]` | D | D <- D + 1 | Increment |
|
|
| `dec[bwlq]` | D | D <- D - 1 | Decrement |
|
|
|
|
%%ANKI
|
|
Basic
|
|
What four variants do `INC` instructions take on in x86-64?
|
|
Back: `incb`, `incw`, `incl`, `incq`
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716125986895-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Which instruction class corresponds to effect $D \leftarrow D + 1$?
|
|
Back: `INC`
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716127743477-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
What source/destination types are permitted in unary instructions?
|
|
Back: Registers and memory addresses.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716125986904-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
What do the instructions in the `INC` instruction class do?
|
|
Back: Increments the specified destination by $1$.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716125986907-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Cloze
|
|
The {`INC`} instruction class is to x86-64 whereas the {`++`} operator is to C.
|
|
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: 1716126147793-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
What do the instructions in the `DEC` instruction class do?
|
|
Back: Decrements the specified destination by $1$.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716125986910-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Which instruction class corresponds to effect $D \leftarrow D - 1$?
|
|
Back: `DEC`
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716127743483-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Cloze
|
|
The {`DEC`} instruction class is to x86-64 whereas the {`--`} operator is to C.
|
|
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: 1716126147798-->
|
|
END%%
|
|
|
|
|
|
|
|
### Binary Operations
|
|
|
|
| Instruction | Operands | Effect | Description |
|
|
| ------------ | -------- | ----------- | -------------- |
|
|
| `add[bwlq]` | S, D | D <- D + S | Addition |
|
|
| `sub[bwlq]` | S, D | D <- D - S | Subtraction |
|
|
| `imul[bwlq]` | S, D | D <- D * S | Multiplication |
|
|
|
|
%%ANKI
|
|
Basic
|
|
What four variants do `ADD` instructions take on in x86-64?
|
|
Back: `addb`, `addw`, `addl`, `addq`
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716127743491-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
What combination of source and destination types is prohibited in `ADD` instructions?
|
|
Back: A source and destination memory address.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716127743494-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Which instruction class corresponds to effect $D \leftarrow D + S$?
|
|
Back: `ADD`
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716127743497-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Cloze
|
|
The {`ADD`} instruction class is to x86-64 as the {`+=`} operator is to C.
|
|
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: 1716128138030-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Which instruction class corresponds to effect $D \leftarrow D - S$?
|
|
Back: `SUB`
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716127743500-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Which `SUB` instruction is equivalent to `decq %rcx`?
|
|
Back:
|
|
```asm
|
|
subq $1, %rcx
|
|
```
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716127853102-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
How does Bryant et al. recommend reading `SUB` 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.
|
|
<!--ID: 1716127853106-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Cloze
|
|
The {`SUB`} instruction class is to x86-64 as the {`-=`} operator is to C.
|
|
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: 1716128138033-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Which instruction class corresponds to effect $D \leftarrow D * S$?
|
|
Back: `IMUL`
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716127743502-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Cloze
|
|
The {`IMUL`} instruction class is to x86-64 as the {`*=`} operator is to C.
|
|
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: 1716128138036-->
|
|
END%%
|
|
|
|
### Shift Operations
|
|
|
|
| Instruction | Operands | Effect | Description |
|
|
| ----------- | -------- | ------------ | ---------------------- |
|
|
| `sal[bwlq]` | k, D | D <- D << k | Left shift |
|
|
| `shl[bwlq]` | k, D | D <- D << k | Left shift |
|
|
| `sar[bwlq]` | k, D | D <- D >> k | Arithmetic right shift |
|
|
| `shr[bwlq]` | k, D | D <- D >>> k | Logical right shift |
|
|
|
|
%%ANKI
|
|
Basic
|
|
What do instructions in the `SAL` instruction class do?
|
|
Back: Performs a left shift.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716226827710-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
What do instructions in the `SHL` instruction class do?
|
|
Back: Performs a left shift.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716226827717-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Which instruction classes are related to left shifts?
|
|
Back: `SAL` and `SHL`.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716226827720-->
|
|
END%%
|
|
|
|
|
|
%%ANKI
|
|
Basic
|
|
Which instruction classes are related to right shifts?
|
|
Back: `SAR` and `SHR`.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716226827723-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
What do instructions in the `SAR` instruction class do?
|
|
Back: Performs an arithmetic right shift.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716226827725-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
What do instructions in the `SHR` instruction class do?
|
|
Back: Performs a logical right shift.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716226827729-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
What distinguishes the `SAR` and `SHR` instruction classes?
|
|
Back: The former is arithmetic whereas the latter is logical.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716226827732-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
What distinguishes the `SAL` and `SHL` instruction classes?
|
|
Back: N/A.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716226827736-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
Which register do shift operations refer to?
|
|
Back: `%cl`
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716226827740-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
How many lower-order bits of `%cl` does e.g. `salb` look at?
|
|
Back: $3$
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716226827744-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
What can the source of a shift operation be?
|
|
Back: An immediate or the `%cl` register.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716226827748-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
What can the destination of a shift operation be?
|
|
Back: A register or memory location.
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716226827752-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
How many lower-order bits of `%cl` does e.g. `salw` look at?
|
|
Back: $4$
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716226827756-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
How many lower-order bits of `%cl` does e.g. `sall` look at?
|
|
Back: $5$
|
|
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
|
|
<!--ID: 1716226827760-->
|
|
END%%
|
|
|
|
%%ANKI
|
|
Basic
|
|
How many lower-order bits of `%cl` does e.g. `salq` look at?
|
|
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: 1716226827764-->
|
|
END%%
|
|
|
|
## Bibliography
|
|
|
|
* Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016. |