x86 Instruction Set Reference

# NEG

# Two's Complement Negation

Opcode Mnemonic Description
F6 /3 NEG r/m8 Two's complement negate r/m8.
F7 /3 NEG r/m16 Two's complement negate r/m16.
F7 /3 NEG r/m32 Two's complement negate r/m32.

# Description

Replaces the value of operand (the destination operand) with its two's complement. (This operation is equivalent to subtracting the operand from 0.) The destination operand is located in a general-purpose register or a memory location.

This instruction can be used with a LOCK prefix to allow the instruction to be executed atomically.

# Operation

if(Destination == 0) CF = 0;
else CF = 1;
Destination = -Destination;
1
2
3
4

# Flags affected

The CF flag set to 0 if the source operand is 0; otherwise it is set to 1. The OF, SF, ZF, AF, and PF flags are set according to the result.

# Protected Mode Exceptions
#GP(0) If the destination is located in a non-writable segment. If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit. If the DS, ES, FS, or GS register contains a null segment selector.
#GP(0) If the destination is located in a non-writable segment. If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit. If the DS, ES, FS, or GS register contains a null segment selector.
#SS(0) If a memory operand effective address is outside the SS segment limit.
#PF(fault-code) If a page fault occurs.

# Real-Address Mode Exceptions
#GP If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.
#GP If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.

# Virtual-8086 Mode Exceptions
#GP(0) If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.
#GP(0) If a memory operand effective address is outside the CS, DS, ES, FS, or GS segment limit.
#SS(0) If a memory operand effective address is outside the SS segment limit.
#PF(fault-code) If a page fault occurs.
Instruction Latency Throughput Execution Unit
CPUID 0F3n/0F2n 0F3n/0F2n 0F2n
NEG 1/0.5 0.5/0.5 ALU

← NOP →