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Alignment and typedefs.

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Joshua Potter 2024-11-05 11:32:35 -07:00
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"Basic": [ "Basic": [

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* Additional notes on pointers and arrays.
* First pass on "The Lost Art of Structure Packing".

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---
title: Alignment
TARGET DECK: Obsidian::STEM
FILE TAGS: c17 x86-64
tags:
- c17
---
## Overview
For a large class of modern ISAs, storage for basic C datatypes respect **self-alignmnet**. This means `char`s can start on any byte address, `short`s on any even address, 4-byte `int`s and `float`s must start on an address divisible by 4, and `double`s must start on an address divisible by 8. Likewise pointers are also self-aligned.
%%ANKI
Basic
What does self-alignment refer to?
Back: The placement of C datatypes on an address divisible by the size of the datatype.
Reference: Raymond, Eric. “The Lost Art of Structure Packing.” Accessed November 4, 2024. [http://www.catb.org/esr/structure-packing/](http://www.catb.org/esr/structure-packing/).
<!--ID: 1730831516929-->
END%%
%%ANKI
Basic
What addresses can a `char` be stored at?
Back: Any address.
Reference: Raymond, Eric. “The Lost Art of Structure Packing.” Accessed November 4, 2024. [http://www.catb.org/esr/structure-packing/](http://www.catb.org/esr/structure-packing/).
<!--ID: 1730831516932-->
END%%
%%ANKI
Basic
What addresses can a `int` be stored at?
Back: Any address divisible by 4.
Reference: Raymond, Eric. “The Lost Art of Structure Packing.” Accessed November 4, 2024. [http://www.catb.org/esr/structure-packing/](http://www.catb.org/esr/structure-packing/).
<!--ID: 1730831516934-->
END%%
%%ANKI
Basic
What addresses can a `short` be stored at?
Back: Any address divisible by 2.
Reference: Raymond, Eric. “The Lost Art of Structure Packing.” Accessed November 4, 2024. [http://www.catb.org/esr/structure-packing/](http://www.catb.org/esr/structure-packing/).
<!--ID: 1730831516936-->
END%%
%%ANKI
Basic
What addresses can a `double` be stored at?
Back: Any address divisible by 8.
Reference: Raymond, Eric. “The Lost Art of Structure Packing.” Accessed November 4, 2024. [http://www.catb.org/esr/structure-packing/](http://www.catb.org/esr/structure-packing/).
<!--ID: 1730831516938-->
END%%
%%ANKI
Basic
What addresses can a pointer be stored at?
Back: Any address divisible by 8.
Reference: Raymond, Eric. “The Lost Art of Structure Packing.” Accessed November 4, 2024. [http://www.catb.org/esr/structure-packing/](http://www.catb.org/esr/structure-packing/).
<!--ID: 1730831516941-->
END%%
%%ANKI
Basic
How does self-alignment make access faster?
Back: It enables single instruction fetches and puts.
Reference: Raymond, Eric. “The Lost Art of Structure Packing.” Accessed November 4, 2024. [http://www.catb.org/esr/structure-packing/](http://www.catb.org/esr/structure-packing/).
<!--ID: 1730831516943-->
END%%
%%ANKI
Cloze
With respect to memory alignment, {slop} is {waste space for padding datatypes to their alignment}.
Reference: Raymond, Eric. “The Lost Art of Structure Packing.” Accessed November 4, 2024. [http://www.catb.org/esr/structure-packing/](http://www.catb.org/esr/structure-packing/).
<!--ID: 1730831516944-->
END%%
%%ANKI
Basic
What value is slop initialized to?
Back: Undefined.
Reference: Raymond, Eric. “The Lost Art of Structure Packing.” Accessed November 4, 2024. [http://www.catb.org/esr/structure-packing/](http://www.catb.org/esr/structure-packing/).
<!--ID: 1730831516946-->
END%%
%%ANKI
Basic
*Why* isn't equality for `struct`s well-defined?
Back: The value of slop is undefined.
Reference: Raymond, Eric. “The Lost Art of Structure Packing.” Accessed November 4, 2024. [http://www.catb.org/esr/structure-packing/](http://www.catb.org/esr/structure-packing/).
<!--ID: 1730831516947-->
END%%
%%ANKI
Basic
*Why* isn't inequality for `struct`s well-defined?
Back: The value of slop is undefined.
Reference: Raymond, Eric. “The Lost Art of Structure Packing.” Accessed November 4, 2024. [http://www.catb.org/esr/structure-packing/](http://www.catb.org/esr/structure-packing/).
<!--ID: 1730831516948-->
END%%
## Bibliography
* Raymond, Eric. “The Lost Art of Structure Packing.” Accessed November 4, 2024. [http://www.catb.org/esr/structure-packing/](http://www.catb.org/esr/structure-packing/).

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@ -132,54 +132,6 @@ Reference: Van der Linden, Peter. _Expert C Programming: Deep C Secrets_. Progra
<!--ID: 1722786892108--> <!--ID: 1722786892108-->
END%% END%%
%%ANKI
Basic
What is the type of `x` in the following?
```c
#define int_ptr int *
int_ptr x, y;
```
Back: `int *`
Reference: Van der Linden, Peter. _Expert C Programming: Deep C Secrets_. Programming Languages / C. Mountain View, Cal.: SunSoft Pr, 1994.
<!--ID: 1722786892109-->
END%%
%%ANKI
Basic
What is the type of `y` in the following?
```c
#define int_ptr int *
int_ptr x, y;
```
Back: `int`
Reference: Van der Linden, Peter. _Expert C Programming: Deep C Secrets_. Programming Languages / C. Mountain View, Cal.: SunSoft Pr, 1994.
<!--ID: 1722786892110-->
END%%
%%ANKI
Basic
What is the type of `x` in the following?
```c
typedef int_ptr int *
int_ptr x, y;
```
Back: `int *`
Reference: Van der Linden, Peter. _Expert C Programming: Deep C Secrets_. Programming Languages / C. Mountain View, Cal.: SunSoft Pr, 1994.
<!--ID: 1722786892111-->
END%%
%%ANKI
Basic
What is the type of `y` in the following?
```c
typedef int_ptr int *
int_ptr x, y;
```
Back: `int *`
Reference: Van der Linden, Peter. _Expert C Programming: Deep C Secrets_. Programming Languages / C. Mountain View, Cal.: SunSoft Pr, 1994.
<!--ID: 1722786892112-->
END%%
Declarations can be read by complying with the precedence rules outlined below: Declarations can be read by complying with the precedence rules outlined below:
1. Find the name of the declaration. 1. Find the name of the declaration.

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@ -0,0 +1,126 @@
---
title: Typedefs
TARGET DECK: Obsidian::STEM
FILE TAGS: c17::type
tags:
- c17
---
## Overview
The `<stddef.h>` header defines a few standard `typedef`s:
* `ptrdiff_t`: the signed integer type of the result of subtracting two pointers.
* `size_t`: the unsigned integer type of the result of the `sizeof` operator.
The standard often uses `typedef`s ending with `_t`.
%%ANKI
Basic
What is the type of `x` in the following?
```c
#define int_ptr int *
int_ptr x, y;
```
Back: `int *`
Reference: Van der Linden, Peter. _Expert C Programming: Deep C Secrets_. Programming Languages / C. Mountain View, Cal.: SunSoft Pr, 1994.
<!--ID: 1722786892109-->
END%%
%%ANKI
Basic
What is the type of `y` in the following?
```c
#define int_ptr int *
int_ptr x, y;
```
Back: `int`
Reference: Van der Linden, Peter. _Expert C Programming: Deep C Secrets_. Programming Languages / C. Mountain View, Cal.: SunSoft Pr, 1994.
<!--ID: 1722786892110-->
END%%
%%ANKI
Basic
What is the type of `x` in the following?
```c
typedef int_ptr int *
int_ptr x, y;
```
Back: `int *`
Reference: Van der Linden, Peter. _Expert C Programming: Deep C Secrets_. Programming Languages / C. Mountain View, Cal.: SunSoft Pr, 1994.
<!--ID: 1722786892111-->
END%%
%%ANKI
Basic
What is the type of `y` in the following?
```c
typedef int_ptr int *
int_ptr x, y;
```
Back: `int *`
Reference: Van der Linden, Peter. _Expert C Programming: Deep C Secrets_. Programming Languages / C. Mountain View, Cal.: SunSoft Pr, 1994.
<!--ID: 1722786892112-->
END%%
%%ANKI
Basic
What header defines `size_t`?
Back: `<stddef.h>`
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1730740461658-->
END%%
%%ANKI
Basic
What header defines `ptrdiff_t`?
Back: `<stddef.h>`
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1730740461659-->
END%%
%%ANKI
Basic
`ptrdiff_t` is used as the type of what result?
Back: Subtracting two pointers.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1730740461660-->
END%%
%%ANKI
Basic
`size_t` is used as the type of what result?
Back: The `sizeof` operation.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1730740461661-->
END%%
%%ANKI
Basic
Is `ptrdiff_t` signed or unsigned?
Back: Signed.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1730740461662-->
END%%
%%ANKI
Basic
Is `size_t` signed or unsigned?
Back: Unsigned.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1730740461663-->
END%%
%%ANKI
Basic
The C standard typically suffixes `typedef`s with what?
Back: `_t`
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730758755507-->
END%%
## Bibliography
* “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
* Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
* Van der Linden, Peter. _Expert C Programming: Deep C Secrets_. Programming Languages / C. Mountain View, Cal.: SunSoft Pr, 1994.

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@ -508,6 +508,53 @@ Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70
<!--ID: 1728244147664--> <!--ID: 1728244147664-->
END%% END%%
%%ANKI
Basic
Add initializer with first element set to `1` using designated initialization.
```c
int example[3];
```
Back:
```c
int example[3] = { [0] = 1 };
```
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730757470057-->
END%%
%%ANKI
Basic
Add initializer with first element set to `1` *without* using designated initialization.
```c
int example[3];
```
Back:
```c
int example[3] = { 1 };
```
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730757470061-->
END%%
%%ANKI
Basic
What is the value of `example[1]` in the following?
```c
int example[2] = { [0] = 1 };
```
Back: `0`
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730757470063-->
END%%
%%ANKI
Basic
Are arrays passed by reference or value?
Back: Reference.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730758755493-->
END%%
### Structures ### Structures
A `struct` is a grouping of data together. It has the following general form: A `struct` is a grouping of data together. It has the following general form:
@ -560,6 +607,125 @@ Reference: Van der Linden, Peter. _Expert C Programming: Deep C Secrets_. Progra
<!--ID: 1722786892128--> <!--ID: 1722786892128-->
END%% END%%
%%ANKI
Basic
Define an object with `fieldA` set to `1` using designated initialization.
```c
struct example { int fieldA; };
```
Back:
```c
struct example test = { .fieldA = 1 };
```
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730757470065-->
END%%
%%ANKI
Basic
Define an object with `fieldA` set to `1` *without* using designated initialization.
```c
struct example { int fieldA; };
```
Back:
```c
struct example test = { 1 };
```
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730757470066-->
END%%
%%ANKI
Basic
What is the value of `test.fieldB` in the following?
```c
struct example { int fieldA; int fieldB; };
struct example test = { .fieldA = 1 };
```
Back: `0`
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730757470068-->
END%%
%%ANKI
Basic
Are `struct`s well-defined with respect to `=` (i.e. assignment)?
Back: Yes.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730758755496-->
END%%
%%ANKI
Basic
Are `struct`s well-defined with respect to `==` (i.e. equality)?
Back: No.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730758755498-->
END%%
%%ANKI
Basic
Are `struct`s well-defined with respect to `!=` (i.e. inequality)?
Back: No.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730758755499-->
END%%
%%ANKI
Basic
Generally speaking, what are valid member types of a `struct`?
Back: All object types except VLAs.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730758755500-->
END%%
%%ANKI
Basic
Generally speaking, what object type is not a valid `struct` member type?
Back: VLAs.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730758755501-->
END%%
%%ANKI
Basic
Declare a variable `var` of the nested `struct` with member `c` set to `1`.
```c
struct A {
struct B { int c; };
};
```
Back: `struct B var = { 1 };`
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730758755502-->
END%%
%%ANKI
Basic
What is the visibility of `struct B` with respect to `struct A`?
```c
struct A {
struct B { int c; };
};
```
Back: They have the same visibility.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730758755503-->
END%%
%%ANKI
Basic
What does it mean for `struct A` and `struct B` to have the same visibility?
```c
struct A {
struct B { int c; };
};
```
Back: Nesting `struct`s does not introduce any notion of scope.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730758755504-->
END%%
## Unions ## Unions
A `union` is a grouping of data together but with overlaid storage. It has the following general form: A `union` is a grouping of data together but with overlaid storage. It has the following general form:
@ -607,7 +773,7 @@ END%%
## Pointers ## Pointers
Pointers have the same size as the machine's word size since it should be able to refer to any virtual address. Pointers have the same size as the machine's word size since it should be able to refer to any virtual address. All pointers are either **valid**, **null**, or **indeterminate**.
%%ANKI %%ANKI
Basic Basic
@ -617,6 +783,257 @@ Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Program
<!--ID: 1707493017246--> <!--ID: 1707493017246-->
END%% END%%
%%ANKI
Basic
How is a pointer represented in binary?
Back: N/A. This is implementation specific.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730755551586-->
END%%
%%ANKI
Basic
What three states can a pointer be in?
Back: Valid, null, or indeterminate.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730755551590-->
END%%
%%ANKI
Basic
How is a pointer made null?
Back: By initializing or assigning the pointer to `0`.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730755551592-->
END%%
%%ANKI
Basic
When does a pointer evaluate to `false`?
Back: When it is a null pointer.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730755551594-->
END%%
%%ANKI
Basic
When does a pointer evaluate to `true`?
Back: When it is not a null pointer.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730755551596-->
END%%
%%ANKI
Basic
Suppose a pointer logically evaluates to `true`. Why can't we use it?
Back: Logical evaluation can't distinguish valid pointers from indeterminate pointers.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730755551598-->
END%%
%%ANKI
Basic
What is the result of dereferencing an indeterminate pointer?
Back: Undefined behavior.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730755551599-->
END%%
%%ANKI
Basic
What is the result of dereferencing a null pointer?
Back: Undefined behavior.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730755551601-->
END%%
%%ANKI
Basic
How is `r->field` equivalently written using `*`?
Back: `(*r).field`
Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1730757470069-->
END%%
%%ANKI
Basic
How is `(*r).field` more compactly written?
Back: `r->field`
Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1730757492874-->
END%%
%%ANKI
Basic
How many members *must* be defined in a `struct` initializer?
Back: One.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730758755505-->
END%%
%%ANKI
Basic
Are `struct`s passed by reference or value?
Back: Value.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1730758755506-->
END%%
C allows arithmetic on pointers, where the computed value is scaled according to the size of the data type referenced by the pointer.
%%ANKI
Basic
How is the following (assumed valid) expression simplified?
```c
*&E
```
Back: As just `E`.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1730740461664-->
END%%
%%ANKI
Basic
How is the following (assumed valid) expression simplified?
```c
&*E
```
Back: As just `E`.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1730740461665-->
END%%
%%ANKI
Cloze
Pointer arithmetic {`*(A + i)`} is equivalent to array reference `A[i]`.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1730740461666-->
END%%
%%ANKI
Basic
Given the following, how can we equivalent write `A[1][2]` using pointer arithmetic?
```c
int main() {
int A[3][4];
return 0;
}
```
Back: `A + 6`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1730745799783-->
END%%
%%ANKI
Basic
Given the following, how can we equivalent write `A[2][0]` using pointer arithmetic?
```c
int main() {
int A[3][4];
return 0;
}
```
Back: `A + 8`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1730745799787-->
END%%
%%ANKI
Basic
Given the following, how can we equivalent write `A[1][2]` using pointer arithmetic?
```c
int main() {
int A[4][3];
return 0;
}
```
Back: `A + 5`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1730745799789-->
END%%
%%ANKI
Basic
Given the following, how can we equivalent write `A[1][0]` using pointer arithmetic?
```c
int main() {
int A[4][3];
return 0;
}
```
Back: `A + 3`
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1730745799791-->
END%%
%%ANKI
Basic
How is the `return` statement likely translated to x86-64?
```c
int* example(int *E) {
return E;
}
```
Back:
```asm
movq %rdi,%rax
```
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
Tags: x86-64
<!--ID: 1730740461667-->
END%%
%%ANKI
Basic
How is the `return` statement likely translated to x86-64?
```c
int example(int *E) {
return E[0];
}
```
Back:
```asm
movl (%rdi),%eax
```
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
Tags: x86-64
<!--ID: 1730740461668-->
END%%
%%ANKI
Basic
How is the `return` statement likely translated to x86-64?
```c
int example(int *E, int i) {
return E[i];
}
```
Back:
```asm
movl (%rdi, %rsi, 4),%eax
```
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
Tags: x86-64
<!--ID: 1730740461669-->
END%%
%%ANKI
Basic
How is the `return` statement likely translated to x86-64?
```c
int example(int *E) {
return &E[2];
}
```
Back:
```asm
leaq 8(%rdi),%rax
```
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
Tags: x86-64
<!--ID: 1730740461670-->
END%%
## Bibliography ## Bibliography
* Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016. * Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.

24
notes/x86-64/instructions/index.md
View File

@ -282,6 +282,30 @@ Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Program
<!--ID: 1713213168894--> <!--ID: 1713213168894-->
END%% END%%
%%ANKI
Basic
Consider scaled index operand form $Imm(r_b, r_i, s)$. What values can $r_b$ take on?
Back: Any 64-bit register.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1730740461653-->
END%%
%%ANKI
Basic
Consider scaled index operand form $Imm(r_b, r_i, s)$. What values can $r_i$ take on?
Back: Any 64-bit register.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1730740461655-->
END%%
%%ANKI
Basic
Consider scaled index operand form $Imm(r_b, r_i, s)$. What values can $s$ take on?
Back: $1$, $2$, $4$, or $8$.
Reference: Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
<!--ID: 1730740461656-->
END%%
## Bibliography ## Bibliography
* Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016. * Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.