[Mesa-dev] Issue with 3008161d28: st_glsl_to_tgsi: rewrite rename registers to use array fully.

[Brian Paul]

Hi Dave,

We found an issue with this change:

commit 3008161d28e38336ba39aba4769a2deaf9732f55
Author: Dave Airlie <airlied at redhat.com>
Date:   Tue May 30 15:52:13 2017 +1000

     st_glsl_to_tgsi: rewrite rename registers to use array fully.

     Instead of having to search the whole array, just use the whole
     thing and store a valid bit in there with the rename.

     Removes this from the profile on some of the fp64 tests

     Reviewed-by: Timothy Arceri <tarceri at itsqueeze.com>
     Signed-off-by: Dave Airlie <airlied at redhat.com>

After this patch landed, the number of temporary registers used by the 
TGSI code increased.  With a particular Photoshop shader, the number 
increased from 26 to 31.  With our legacy virtual GPU version, this 
causes us to run out of registers and fail translation.

Did you expect this change to increase the number of temps used?  Is it 
possible to get the old behavior back?  I don't think we can just revert 
this patch since a number of changes since then build on it.

Thanks.

-Brian