Fast bit doubling, how?

[tumbleweed]

Even though it looks longer, this should end up almost twice as fast...

outvar = 0
if (invar.0) then
    outvar.0 = 1
    outvar.1 = 1
endif
if (invar.1) then
    outvar.2 = 1
    outvar.3 = 1
endif
if (invar.2) then
    outvar.4 = 1
    outvar.5 = 1
endif
if (invar.3) then
    outvar.6 = 1
    outvar.7 = 1
endif
if (invar.4) then
    outvar.8 = 1
    outvar.9 = 1
endif
if (invar.5) then
    outvar.10 = 1
    outvar.11 = 1
endif
if (invar.6) then
    outvar.12 = 1
    outvar.13 = 1
endif
if (invar.7) then
    outvar.14 = 1
    outvar.15 = 1
endif

[Ioannis]

I think #2 is faster.

Ioannis

[tumbleweed]

It can depend on the device and where the variables end up, but here's a contrast of the two methods (post #2, post #6)

invar    #2    #6
$00      64    34
$01      64    36
$55      64    42
$FF      64    50

That's for an 18F26K22. Results are in instruction cycles.
Post #2 has the "advantage" of always taking 64 cycles, but #6 is always faster.

[Ioannis]

Impressive!

Thanks,
Ioannis