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(Created page with "The ADX instruction extension contains the instructions * ADCX * ADOX They are similar to the ADC instruction by doing a add with overflow, but * ADCX uses the Carry flag as s...") |
(→Overview: Changed "an register" to "a register"; changed "effecting flags" to "affecting flags.") |
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| − | + | {{x86 title|ADX}}{{x86 isa main}} | |
| + | '''ADX''' is an {{x86|extensions|x86 instruction set extension}} that introduced [[arbitrary-precision arithmetic]] operations. | ||
| + | |||
| + | == Overview == | ||
| + | ADX introduced two new instructions: | ||
| + | |||
* ADCX | * ADCX | ||
* ADOX | * ADOX | ||
| + | |||
They are similar to the ADC instruction by doing a add with overflow, but | They are similar to the ADC instruction by doing a add with overflow, but | ||
| + | |||
* ADCX uses the Carry flag as source and destination of overflow and leaves the other flags untouched | * ADCX uses the Carry flag as source and destination of overflow and leaves the other flags untouched | ||
* ADOX uses the Overflow flag as source and destination of overflow and leaves the other flags untouched | * ADOX uses the Overflow flag as source and destination of overflow and leaves the other flags untouched | ||
| − | This | + | |
| + | This allows two parallel addition of multi-precision numbers because both have their separate carry flag. | ||
Note: | Note: | ||
| − | * To add a constant to | + | |
| − | < | + | * To add a constant to a register without affecting flags, you can use the <code>LEA reg, [reg + n]</code> instruction |
| + | |||
| + | <source lang=asm> | ||
xor rax, rax | xor rax, rax | ||
lbl: | lbl: | ||
| Line 21: | Line 31: | ||
dec r14 | dec r14 | ||
jnz lbl | jnz lbl | ||
| − | </ | + | </source> |
Latest revision as of 11:28, 10 August 2021
x86
Instruction Set Architecture
Instruction Set Architecture
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- Addressing Modes
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ADX is an x86 instruction set extension that introduced arbitrary-precision arithmetic operations.
Overview[edit]
ADX introduced two new instructions:
- ADCX
- ADOX
They are similar to the ADC instruction by doing a add with overflow, but
- ADCX uses the Carry flag as source and destination of overflow and leaves the other flags untouched
- ADOX uses the Overflow flag as source and destination of overflow and leaves the other flags untouched
This allows two parallel addition of multi-precision numbers because both have their separate carry flag.
Note:
- To add a constant to a register without affecting flags, you can use the
LEA reg, [reg + n]instruction
xor rax, rax
lbl:
mov rbx, [r8 + r15]
adcx rbx, [r9 + r15]
mov [r9 + r15], rbx
mov rbx, [r10 + r15]
adox rbx, [r11 + r15]
mov [r11 + r15], rbx
lea r15, [r15 + 8]
dec r14
jnz lbl