31 KiB
| title | TARGET DECK | FILE TAGS | tags | |
|---|---|---|---|---|
| Instructions | Obsidian::STEM | x86-64 |
|
Overview
x86-64 instructions are designed so that commonly used instructions and those with fewer operands are encoded in a smaller number of bytes. Instructions range in length from 1 to 15 bytes.
x86-64 assembly comes in two flavors: ATT and Intel. ATT is most common in Linux systems so I focus on that. The most important distinction between the two is operand ordering: Intel syntax lists multiple operands in reverse order compared to ATT.
%%ANKI Basic x86-64 assembly comes in what two formats? Back: ATT and Intel. 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 Which x86-64 assembly format does Linux use? Back: ATT. 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 Which x86-64 assembly format does Microsoft use? Back: Intel. 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 the "most confusing" difference between ATT and Intel assembly? Back: Multiple operands in one are listed in reverse order relative to the other. 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 term describes assembly lines with a leading .?
Back: Directives.
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 Assembly directives are important for what two programs? Back: The assembler and the linker. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
Instruction Classes
There are three types of operands:
- Immediates. These denote constant values. In ATT assembly, they are written with a
$followed by an integer using standard C notation. - Registers. These denote the contents of a register.
- Memory. These denote some memory location according to a computed address (i.e. the effective address).
| Type | Form | Operand Value | Name |
|---|---|---|---|
| Immediate | \textdollar Imm |
Imm |
Immediate |
| Register | r_a |
R[r_a] |
Register |
| Memory | Imm |
M[Imm] |
Absolute |
| Memory | (r_a) |
M[R[r_a]] |
Indirect |
| Memory | Imm(r_b) |
M[Imm + R[r_b]] |
Base + displacement |
| Memory | (r_b, r_i) |
M[R[r_b] + R[r_i]] |
Indexed |
| Memory | Imm(r_b, r_i) |
M[Imm + R[r_b] + R[r_i]] |
Indexed |
| Memory | (,r_i,s) |
M[R[r_i] \cdot s] |
Scaled indexed |
| Memory | Imm(,r_i,s) |
M[Imm + R[r_i] \cdot s] |
Scaled indexed |
| Memory | (r_b,r_i,s) |
M[R[r_b] + R[r_i] \cdot s] |
Scaled indexed |
| Memory | Imm(r_b,r_i,s) |
M[Imm + R[r_b] + R[r_i] \cdot s] |
Scaled indexed |
%%ANKI Basic What are the three types of operands instructions can act on? Back: Immediates, 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.
END%%
%%ANKI Basic What are the types of source operands instructions can specify? Back: Immediates, 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.
END%%
%%ANKI Basic What are the types of destination operands instructions can specify? 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.
END%%
%%ANKI Basic What does an immediate operand denote? Back: A constant value. 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 ATT syntax, how is an immediate written?
Back: As a $$ followed by an integer using standard C notation.
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 ATT syntax, how is a register written?
Back: As a % followed by the name of the register.
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 the operand value of form \textdollar Imm?
Back: Imm
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 the operand value of form r_a?
Back: R[r_a]
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 the operand value of form Imm?
Back: M[Imm]
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 the operand value of form (r_a)?
Back: M[R[r_a]]
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 the operand value of form Imm(r_b)?
Back: M[Imm + R[r_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 is the operand value of form (r_b, r_i)?
Back: M[R[r_b] + R[r_i]]
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 the operand value of form Imm(r_b, r_i)?
Back: M[Imm + R[r_b] + R[r_i]]
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 the operand value of form (,r_i,s)?
Back: M[R[r_i] \cdot s]
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 the operand value of form Imm(,r_i,s)?
Back: M[Imm + R[r_i] \cdot s]
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 the operand value of form (r_b,r_i,s)?
Back: M[R[r_b] + R[r_i] \cdot s]
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 the operand value of form Imm(r_b,r_i,s)?
Back: M[Imm + R[r_b] + R[r_i] \cdot s]
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 operand value r_a from (r_a)?
Back: The former denotes the register value. The latter denotes the value in memory at the address stored in r_a.
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 values can s take on in operand form Imm(r_b,r_i,s)?
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.
END%%
%%ANKI
Basic
What operand form is named "immediate"?
Back: \textdollar Imm
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 operand form is named "register"?
Back: r_a
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 operand form is named "absolute"?
Back: Imm
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 operand form is named "indirect"?
Back: (r_a)
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 operand form is named "base + displacement"?
Back: Imm(r_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 is the most general operand form named "indexed" (not "scaled indexed")?
Back: Imm(r_b, r_i)
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 the most general operand form named "scaled indexed" (not indexed)?
Back: Imm(r_b, r_i, s)
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
MOV
The MOV instruction class has four primary variants: movb, movw, movl, and movq. There also exist zero extension and sign extension variations in the forms of MOVS and MOVZ.
| Instruction | Operands | Effect | Description |
|---|---|---|---|
movb |
S, D | D <- S | Move byte |
movw |
S, D | D <- S | Move word |
movl |
S, D | D <- S | Move double word |
movq |
S, D | D <- S | Move quad word |
movabsq |
I, R | R <- I | Move quad word |
movzbw |
S, R | R <- ZE(S) | Move zero-extended byte to word |
movzbl |
S, R | R <- ZE(S) | Move zero-extended byte to double word |
movzwl |
S, R | R <- ZE(S) | Move zero-extended word to double word |
movzbq |
S, R | R <- ZE(S) | Move zero-extended byte to quad word |
movzwq |
S, R | R <- ZE(S) | Move zero-extended word to quad word |
movsbw |
S, R | R <- SE(S) | Move sign-extended byte to word |
movsbl |
S, R | R <- SE(S) | Move sign-extended byte to double word |
movswl |
S, R | R <- SE(S) | Move sign-extended word to double word |
movsbq |
S, R | R <- SE(S) | Move sign-extended byte to quad word |
movswq |
S, R | R <- SE(S) | Move sign-extended word to quad word |
movslq |
S, R | R <- SE(S) | Move sign-extended double word to quad word |
cltq |
%rax <- SE(%eax) | Sign-extend %eax to %rax |
Notice there is no movzlq instruction. movl covers this functionality since, by convention, instructions moving double words into a 64-bit register automatically zeroes out the upper 32 bits.
%%ANKI
Basic
What four variants does MOV instructions take on in x86-64?
Back: movb, movw, movl, movq
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 many bytes does a movb instruction operate on?
Back: One.
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 many bytes does a movw instruction operate on?
Back: Two.
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 many bytes does a movl instruction operate on?
Back: Four.
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 many bytes does a movq instruction operate on?
Back: Eight.
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 combination of source and destination types is prohibited in MOV 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.
END%%
%%ANKI
Basic
What is the result of %rax after instruction movl $0x4050,%eax?
Back: Upper 32-bits is 0 and lower 32-bits is 0x4050.
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 the result of %rax after instruction movq $0x4050,%rax?
Back: The 64-bit value is 0x4050.
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 the result of %rax after instruction movw $0x4050,%ax?
Back: The upper 48 bits are unchanged and the lower 16 bits are 0x4050.
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 the result of %rax after instruction movb $0x4050,%al?
Back: The upper 56 bits are unchanged and the lower 8 bits are 0x50.
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 the result of %rax after instruction movw $0x4050,%al?
Back: N/A. Invalid operand for instruction.
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 caveat is applied to the source operand of movq?
Back: Immediates are 32-bit two's-complement numbers sign extended to 64-bits.
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 mov instruction is needed when working with 64-bit immediate sources?
Back: movabsq
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 purpose does movabsq solve that movq does not?
Back: movabsq can have an arbitrary 64-bit immediate source.
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 the result of %rax after the following instructions?
movabsq $0x0011223344556677, %rax
movb $-1, %al
Back: 0x00112233445566FF
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 the result of %rax after the following instructions?
movabsq $0x0011223344556677, %rax
movw $-1, %ax
Back: 0x001122334455FFFF
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 the result of %rax after the following instructions?
movabsq $0x0011223344556677, %rax
movl $-1, %eax
Back: 0x00000000FFFFFFFF
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 the result of %rax after the following instructions?
movabsq $0x0011223344556677, %rax
movq $-1, %rax
Back: 0xFFFFFFFFFFFFFFFF
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 the MOVZ instruction class?
Back: MOV instructions that zero extend the source to fit into the destination.
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 the MOVS instruction class?
Back: MOV instructions that sign extend the source to fit into the destination.
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 does the movzbw instruction do?
Back: Moves a zero-extended byte to a 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 does the movslq instruction do?
Back: Moves a sign-extended double word to a quad 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 does the movslb instruction do?
Back: N/A. This instruction does not exist.
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 combinatorial argument explains the number of MOVS instructions?
Back: There exists an instruction for each smaller declaration to larger declaration.
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 MOVZ instruction is "missing"?
Back: movzlq
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
Why does there not exist a movzlq instruction?
Back: Because movl already zeroes out the upper bits of a destination register.
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 the result of %rax after the following instructions?
movabsq $0x0011223344556677, %rax
movb $0xAA, %dl
movb %dl,%al
Back: 0x00112233445566AA
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 the result of %rax after the following instructions?
movabsq $0x0011223344556677, %rax
movb $0xAA, %dl
movsbq %dl,%rax
Back: 0xFFFFFFFFFFFFFFAA
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 the result of %rax after the following instructions?
movabsq $0x0011223344556677, %rax
movb $0xAA, %dl
movzbq %dl,%rax
Back: 0x00000000000000AA
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 A {pointer} in C is a {memory address} in x86. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016. Tags: c17
END%%
%%ANKI Basic Dereferencing a pointer in C equates to what two operations in x86? Back: Copying the pointer into a register and then using the register in a memory reference. Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016. Tags: c17
END%%
PUSH and POP
| Instruction | Operands | Effect | Description |
|---|---|---|---|
pushq |
S | R[%rsp] <- R[%rsp] - 8 M[R[%rsp]] <- S |
Push quad word |
popq |
D | D <- M[R[%rsp]] R[%rsp] <- R[%rsp] + 8 |
Pop quad word |
In x86 processors, the stack grows downward, with the "top" of the stack corresponding to lower addresses.
%%ANKI Basic In what direction do x86-64 stacks grow? Back: Downward. 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 The x86-64 stack grows such that the top element has the {lowest} address of all stack elements. 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 is used to push elements onto the stack?
Back: pushq
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 is used to pop elements off of the stack?
Back: popq
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 is pushq %rbp equivalently written using a pair of instructions?
Back:
subq 8,%rsp
movq %rbp,(%rsp)
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 is popq %rax equivalently written using a pair of instructions?
Back:
movq (%rsp),%rax
addq 8,%rsp
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:pushq} is to {2:subq} as {2:popq} is to {1:addq}.
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
If %rsp has value 0x108, what value does it have after a pushq instruction?
Back: 0x100
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
If %rsp has value 0x108, what value does it have after a popq instruction?
Back: 0x110
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
Which register contains a pointer to the top of the stack?
Back: %rsp
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 the %rsp register typically used for?
Back: The stack pointer.
Reference: Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.
END%%
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.
END%%
%%ANKI
Basic
Why is the leaq instruction named the way it is?
Back: It stands for load effective address.
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
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
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.
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.
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.
END%%
%%ANKI
Basic
Besides effect 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.
END%%
%%ANKI
Basic
Assume %rbx holds p and %rdx holds q. What is the value of %rax in the following?
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.
END%%
%%ANKI
Basic
Assume %rbx holds p and %rdx holds q. What is the value of %rax in the following?
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.
END%%
%%ANKI
Basic
Assume %rbx holds p and %rdx holds q. What is the value of %rax in the following?
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.
END%%
%%ANKI
Basic
Assume %rbx holds p and %rdx holds q. What is the value of %rax in the following?
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.
END%%
Bibliography
- Bryant, Randal E., and David O'Hallaron. Computer Systems: A Programmer's Perspective. Third edition, Global edition. Always Learning. Pearson, 2016.