x86 Instructions

Conventions

The following template will be used for instructions that take no operands:

Instr

The following template will be used for instructions that take 1 operand:

Instr arg

The following template will be used for instructions that take 2 operands. Notice how the format of the instruction is different for different assemblers.

Instr src, dest GAS Syntax
Instr dest, src Intel Syntax


The following template will be used for instructions that take 3 operands. Notice how the format of the instruction is different for different assemblers.

Instr aux, src, dest GAS Syntax
Instr dest, src, aux Intel Syntax



Suffixes

Some instructions, especially when built for non-Windows platforms (i.e. Unix, Linux, etc.), require the use of suffixes to specify the size of the data which will be the subject of the operation. Some possible suffixes are:

  • b (byte) = 8 bits.
  • w (word) = 16 bits.
  • l (long) = 32 bits.
  • q (quad) = 64 bits.

An example of the usage with the mov instruction on a 32-bit architecture, GAS syntax:

movl $0x000F, %eax   # Store the value F into the eax register

On Intel Syntax you don't have to use the suffix. Based on the register name and the used immediate value the compiler knows which data size to use.

MOV EAX, 0x000F

Source: Wikibooks, https://en.wikibooks.org/wiki/X86_Assembly/X86_Instructions
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