Intel 253666-024US Manuel D’Utilisation

Vol. 2A 3-115

INSTRUCTION SET REFERENCE, A-M

CMC—Complement Carry Flag

CMC—Complement Carry Flag

Description

Complements the CF flag in the EFLAGS register. CMC operation is the same in non-
64-bit modes and 64-bit mode.

Operation

EFLAGS.CF[bit 0]← NOT EFLAGS.CF[bit 0];

Flags Affected

The CF flag contains the complement of its original value. The OF, ZF, SF, AF, and PF 
flags are unaffected.

Exceptions (All Operating Modes)

#UD 

If the LOCK prefix is used.

Opcode

Instruction

64-Bit Mode Compat/

Leg Mode

Description

F5

CMC

Valid

Valid

Complement CF flag.