[Bug 92760] Add FP64 support to the i965 shader backends

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=92760

--- Comment #33 from Connor Abbott <cwabbott0 at gmail.com> ---
(In reply to Samuel Iglesias from comment #32)
> I found an issue related to the opt_algebraic passes after we lowered lrp
> instruction when it has double-based types as arguments (lrp instruction
> does not support doubles in BDW).
> 
> Currently, the lowering of double ops run as part the optimization loop in
> nir_optimize(). In that lowering function, I converted the lrp to its
> equivalent mathematical function when we have doubles as arguments... which
> is reverted by opt_algebraic() in next iteration of the optimization loop :-)
> 
> My idea is: remove my lrp's lowering pass, add a new flag in
> nir_shader_compiler_options called 'lower_lrp_doubles' and modify
> nir_opt_algebraic.py to run its lrp's lowering when the arguments are
> doubles, if that flag is enabled. Any driver that does not support lrp with
> double arguments, just enable that nir option in its configuration.
> 
> I would like to know your opinion about this solution before implementing
> it. Do you have other solutions in mind?
> 
> Thanks!

That seems like a fine solution -- we already do similar things in a number of
different places in opt_algebraic. Just keep in mind that you'll have to
disable the lrp optimization in opt_algebraic for doubles when that option is
enabled to avoid running into the same problem.

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