[Mesa-dev] [PATCH 5/9] nir: Add a flag for lowering fneg/ineg.

Eric Anholt eric at anholt.net
Tue Feb 3 14:20:03 PST 2015

Connor Abbott <cwabbott0 at gmail.com> writes:

> I think this logic should be flipped around... you should have a flag
> 'lower_sub' which is false for vc4 but true for i965, and then if the
> flag is true we lower sub to add+neg and if false we try and
> reconstruct sub (and do other things like pulling neg's out of
> multiplies). That way, eventually we can turn off the lowering in GLSL
> IR and in the future pass a subtract in the GLSL source all the way
> down to the driver without lowering it and then un-lowering it.

I think given that vc4 is pretty much alone in wanting SUBs instead of
src modifiers, we should probably be the non-default flag value, but I
don't feel too strongly.
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