Re: [hatari-devel] DSP add AGU pipeline for parallel moves

[Andreas Grabher <andreas_g86@xxxxxxxxxx>]

Thank you for fixing this bug. Btw. this did not just cause a warning, the code would have failed. 

In the old code m_reg was uint16_t. It probably makes sense to check the new code for other signed/unsigned data type errors. These errors are very hard to debug if discovered later. 

And I suggest to remove the commented lines. 

> Am 03.06.2024 um 23:02 schrieb Andreas Grabher <andreas_g86@xxxxxxxxxx>:
> 
> Hello,
> 
> thank you for the patch! I added it and have one minor issue:
> 
> For this line in dsp_update_rn() I get a warning "Result of comparison of constant 65535 with expression of type 'int16_t' (aka 'short') is always false":
> 
> if (reg_modulo == 65535) {
> 
> Obviously the value is not recognized as -1 by the compiler. So probably better use -1 instead.
> 
> Best wishes,
> Andreas
> 
>> Am 03.06.2024 um 22:30 schrieb Laurent Sallafranque <laurent.sallafranque@xxxxxxx>:
>> 
>> Hi,
>> 
>> First, I'm pleased to see that tuxfamily.org is back.
>> I've taken some days to try to figure out why underscore demo was always bugging at the same point.
>> The main explanation was the lack of pipeline emulation in the AGU.
>> 
>> For example :
>>    move #<10,r0
>>    move #<15,r0
>>    move x:(r0),a
>> 
>>   The register "a" should equal 10 and not 15, due to a 1 instruction delay.
>>   This happens for parallel moves instructions.
>> 
>> I've implemented this behavior for all Rx, Nx and Mx registers.
>> I've done a lot of non regression tests with many demos, programs, musik players, ... and didn't noticed any regression.
>> 
>> 
>> I've seen this pipeline restriction in some demos with mod player sound embedded, with EKO System, and probably some other demos.
>> The only one I know that suffered this was underscore demo.
>> 
>> _ demo now renders the arrow correctly, with the blue lightened metallic texture and runs more frames before crashing. The crash doesn't always occur at the same point : sometimes it crashs before or later.
>> 
>> The max I can now run is until this frame :
>> 
>> <S2tblOwg38Bq3wQz.png>
>> 
>> 
>> I've implemented the pipe for LUA, Parallel moves, MOVEC, TCC, MOVEP MOVE instructions.
>> The motorola DSP docs also include MOVEM, but I've done many tests and it doesn't seem to suffer the pipeline restriction.
>> 
>> 
>> This improvement in AGU emulation allows to feed the registers R, N or M just in time (also if this is not recommanded by Motorola ;)
>> 
>> Regards
>> Laurent
>> 
> 
> 
>