Em 26/10/2011 13:11, William "Chops" Westfield escreveu:
> On Oct 26, 2011, at 3:17 AM, Isaac Marino Bavaresco wrote:
>
>> What the OP wants?
>> I can see "load the bit mask" -> "load base address" -> "output the
>> value at base address+offset".
> The original complaint was against the slightly larger piece of
> source code for:
>    digitalWriteFast(3,1);
>    digitalWriteFast(3,0);
> Which produced:
>    li      v0,1
>    lui     v1,0xbf88
>    sw      v0,24808(v1)
>    lui     v1,0xbf88
>    sw      v0,24804(v1)
> Which has an obvious extra instruction.
> In a loop, two different registers are used to hold the (same)
> address "page" of two io registers.
>
> It's similar to setting the RAM page explicitly for every access
> on PIC16; not really horrible, but exactly the sort of thing that
> I would hope a compiler would NOT do.  I guess Microchip is really
> hooked on the idea!  :-)
>
> BillW


I'm pretty sure that with optimizations on, the compiler would remove
the redundant instructions.


Isaac

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