Which conditional expression is faster?

**mackrackit** · - 15th February 2009, 07:17

This is faster
IF A+B+C=0
The generated ASM

Code:

ADD?BBW	_A, _B, T1
ADD?WBW	T1, _C, T1
CMPNE?WCL	T1, 000h, L00001

This
IF A=0 AND B=0 AND C=0 THEN
Generates

Code:

CMPEQ?BCB	_A, 000h, T1
CMPEQ?BCB	_B, 000h, T2
LAND?BBW	T1, T2, T2
CMPEQ?BCB	_C, 000h, T3
LAND?WBW	T2, T3, T3
CMPF?WL	T3, L00003

**mister_e** · - 15th February 2009, 10:33

You will have problem with the first one one day or another (put some values in and figure a roll-over), but the second one is bullet proof.

If you want to measure it, you may use the regular suggestions

Set a pin before, and clear it after the IF-THEN or code block. Measure the delay with a scope or frequency meter
Same as above, but use an internal Timer and output the data over serail port
Use MPLAB stopwatch

http://www.picbasic.co.uk/forum/show...33&postcount=9 <-- really handy
http://www.picbasic.co.uk/forum/show...9&postcount=13