OR

Table of Contents

1. OR (or)
   1. Basic function
   2. Instruction format
   3. Behavioral characteristics
   4. Examples
   5. Common uses

OR (or)

Basic function

OR performs a bitwise logical OR operation:

1
x1 = x1 | x2

Instruction format

1
or x1, x2

The same constraints as AND apply:

• x1 can be a register or memory
• x2 can be a register or an immediate value
• Memory-to-memory is not allowed

Behavioral characteristics

• Used to set specific bits
• CF and OF are cleared
• If the result is 0 → ZF = 1, otherwise ZF = 0

Examples

1
or eax, 1
2
; 设置最低位
3

4
or rax, rbx
5
or [rbp-8], 0x80

Common uses

• Set flags or masks
• Merge flags
• Construct specific bitmaps