Low-level programming language: Difference between revisions

Revision as of 12:34, 3 February 2025

Revision as of 16:40, 5 February 2025

Line 48:

<syntaxhighlight lang="asm">

fib:

mov rax, rdi ; put theThe argument is stored in rdi, put it into rax

test rdi, rdi ; isIs itthe argument zero?

je .return_from_fib ; yesYes - return 0, which is already in rax

cmp rdi, 2 ; isCompare 2the greater than or equalargument to it?2

jbe .return_1_from_fib ; yes (i.e.,If it's 1is less than or 2)equal -to 2, return 1

mov rcx, rdi ; no -Otherwise, put it in rcx, for use as a counter

mov rdx, 1 ; theThe first previous number in the sequence, which starts out as 1, put it in rds

mov rsi, 1 ; theThe numbersecond beforeprevious that, whichnumber also starts out as 1, put it in rsi

.fib_loop:

lea rax, [rsi + rdx] ; putPut the sum of the previous two numbers into rax

cmp rcx, 2 ; isIs the counter 2?

je .return_from_fib ; yesYes - rax contains the result

mov rsi, rdx ; Otherwise, make the first previous number the number before thesecond previous onenumber

dec rcx ; decrementDecrement the counter

mov rdx, rax ; makeMake the current number the first previous number

jmp .fib_loop ; keepKeep going

.return_1_from_fib:

mov rax, 1 ; setSet the return value to 1

.return_from_fib:

ret ; returnReturn

</syntaxhighlight>