If statement vs if-else statement, which is faster? [closed]

Answer 1

Ok, since assembly is one of the tags, I will just assume your code is pseudo code (and not necessarily c) and translate it by human into 6502 assembly.

1st Option (without else)

        ldy #$00
        lda #$05
        dey
        bmi false
        lda #$06
false   brk

2nd Option (with else)

        ldy #$00
        dey
        bmi else
        lda #$06
        sec
        bcs end
else    lda #$05
end     brk

Assumptions: Condition is in Y register set this to 0 or 1 on the first line of either option, result will be in accumulator.

So, after counting cycles for both possibilities of each case, we see that the 1st construct is generally faster; 9 cycles when condition is 0 and 10 cycles when condition is 1, whereas option two is also 9 cycles when condition is 0, but 13 cycles when condition is 1. (cycle counts do not include the BRK at the end).

Conclusion: If only is faster than If-Else construct.

And for completeness, here is an optimized value = condition + 5 solution:

ldy #$00
lda #$00
tya
adc #$05
brk

This cuts our time down to 8 cycles (again not including the BRK at the end).