X86-assembly/Instructions/sahf

Description

Store AH into flags regsiter:

EFLAGS(SF:ZF:0:AF:0:PF:1:CF) = AH;

Example

If EAX = 001801C7, AH = 01, as shown below:

              EAX
|<--------- 32 bits ----------->|
+---+---+---+---+---+---+---+---+
| 0 | 0 | 1 | 8 | 0 | 1 | C | 7 |
+---+---+---+---+---+---+---+---+
                       AX
                |<-- 16 bits -->|
                +---+---+---+---+
                | 0 | 1 | C | 7 |
                +---+---+---+---+
                | 8bits | 8bits |
                   AH       AL

The sahf instruction will set EFLAGS as follows:

     +---+---+---+---+---+---+---+---+
AH = | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
     +---+---+---+---+---+---+---+---+
       |   |   |   |   |   |   |   \___ CF
       |   |   |   |   |   |    \___ reserved
       |   |   |   |   |    \___ PF
       |   |   |   |    \___ reserved
       |   |   |    \___ AF
       |   |    \___ reserved
       |    \___ ZF
        \___ SF