[Mesa-dev] [PATCH] Revert "st_glsl_to_tgsi: rewrite rename registers to use array fully."

[Dave Airlie]

On 1 August 2017 at 15:55, Gert Wollny <gw.fossdev at gmail.com> wrote:
> Am Dienstag, den 01.08.2017, 09:32 +1000 schrieb Dave Airlie:
>> From: Dave Airlie <airlied at redhat.com>
>>
>> This reverts commit 3008161d28e38336ba39aba4769a2deaf9732f55,
>> which caused a regression for VMWare.
>>
>> The initial code had some recursion in it, that I removed by accident
>> trying to add back the recursion broke lots of things, take the high
>> road and revert for now.
>
> Since I've prepared a patch set that improves the register merging [1]
> that is awaiting another review I'm wondering which part broke the
> recursion?

The original code has a loop over num_renames, so if two renames
were in the list in order like

8 renames to 4 and 4 renames to 2, then 8 would rename to 2.
however if
4 renamed to 2 then 8 renamed to 4 (not sure if this could happen),
it was different.

My initial patch fails because it only does one transition per slot,
so if 8 renames to 4, then nothing renames it later to 2.

I tried to workaround it quickly and restart the rename, but that broke
the world, and I didn't have time to sort it out.

Dave.