[Mesa-dev] [PATCH 09/11] nir/lower_vec_to_movs: Get rid of start_idx and swizzle compacting

[Eric Anholt]

Jason Ekstrand <jason at jlekstrand.net> writes:

> Previously, we did this thing with keeping track of a separate start_idx
> which was different from the iteration variable.  I think this was a relic
> of the way that GLSL IR implements writemasks.  In NIR, if a given bit in
> the writemask is unset then that channel is just "unused", not missing.  In
> particular, a vec4 operation with a writemask of 0xd will use sources 0, 2,
> and 3 and leave source 1 alone.  We can simplify things a good deal (and
> make them correct) by removing this "compacting" step.

Reviewed-by: Eric Anholt <eric at anholt.net>

Unrelated: looks like the instances of '4' should be
'nir_op_infos[vec->op].num_inputs' in the loops, though.
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