[Libre-soc-isa] [Bug 1077] evaluate removing /vec234 from instructions, move subvl to SVSTATE

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Wed May 3 04:28:01 BST 2023


--- Comment #4 from Jacob Lifshay <programmerjake at gmail.com> ---
(In reply to Jacob Lifshay from comment #2)
> imho it is not sensible to remove subvl from the prefix because GPU code
> often has subvl different in each instruction, so setvl or similar would
> need to be constantly reran just to change subvl, this would easily be many
> times more setvl ops because otherwise setvl is usually ran once per shader
> or once per function.

as an example, take this not-unusual blur shader from supertuxkart:
it would need like 15 setvl ops, and that's without even unrolling that loop!
something like >30 for the loop-unrolled version! If we instead keep the
status-quo with support for subvl in the prefix, the entire function needs just
one setvl op.

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