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.globl _ft_strcmp
_ft_strcmp:
mov rax, rdi # s1
mov rbx, rsi # s2
xor rcx, rcx
FT_STRCMP_LOOP:
cmp byte ptr [rax + rcx], 0
je FT_STRCMP_LOOP_END
cmp byte ptr [rbx + rcx], 0
je FT_STRCMP_LOOP_END
mov dl, byte ptr [rax + rcx]
cmp dl, byte ptr [rbx + rcx]
jne FT_STRCMP_LOOP_END
inc rcx
jmp FT_STRCMP_LOOP
FT_STRCMP_LOOP_END:
mov dl, byte ptr [rax + rcx]
cmp dl, byte ptr [rbx + rcx]
jl FT_STRCMP_S1_LOWER
# s1 >= s2
mov rdx, rax
xor rax, rax
mov al, [rdx + rcx]
sub al, [rbx + rcx]
ret
# s1 < s2
FT_STRCMP_S1_LOWER:
mov rdx, rax
xor rax, rax
mov al, [rbx + rcx]
sub al, [rdx + rcx]
not eax # two's complement
inc eax
ret
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