|
| |
Test
|
86/88 |
Y |
186 |
Y |
286 |
Y |
386 |
Y |
486 |
Y |
TEST destination, source |
|
Ovfl |
0 |
Dir |
N |
Int |
N |
Trap |
N |
Sign |
Y |
Zero |
Y |
Aux |
? |
Prty |
Y |
Carry |
0 |
TEST performs a logical AND on its two operands and updates the flags.
Neither the destination nor source is changed.
TEST is useful for examining the status of individual bits. For
example, the following section of code will transfer control to
ONE_FIVE_OFF if both bits one and five of register AL are cleared. The
status of all other bits will be ignored.
TEST AL,00100010b ;Mask out all bits except 1 and 5
JZ ONE_FIVE_OFF ;If either was set, result was not 0
NOT_BOTH: . ;One or both bits was set
ONE_FIVE_OFF: . ; Bits 1 and 5 were off
------------------------------------ Timing ----------------------------------
OpCode Instruction 386 286 86
A8 ib TEST AL, imm8 2 3 4
A9 iw TEST AX, imm16 2 3 4
A9 id TEST EAX, imm32 2
F6/0 ib TEST r/m8, imm8 2/5 3/6 5/11+EA
F7/0 iw TEST r/m16, imm16 2/5 3/6 5/11+EA
F7/0 id TEST r/m32, imm32 2/5
84/r TEST r/m8, r8 2/5 2/6 3/9+EA
85/r TEST r/m16, r16 2/5 2/6 3/9+EA
85/r TEST r/m32, r32 2/5
------------------------------------ Logic -----------------------------------
(destination AND source) ; set flags only
CF = 0
OF = 0
See Also CMP AND NOT OR XOR Flags |