[Mesa-dev] [PATCH] i965/fs: Allow SIMD16 on pre-SNB when try_replace_with_sel is successful

[Matt Turner]

On Fri, Jan 23, 2015 at 2:32 PM, Ian Romanick <idr at freedesktop.org> wrote:
> From: Ian Romanick <ian.d.romanick at intel.com>
>
> If try_replace_with_sel is able to replace the flow control with a SEL
> instruction, then there is no flow control... failing SIMD16 because
> of nonexistent flow control is wrong.
>
> No piglit regressions on any i965 platform in Jenkins.
>
> total instructions in shared programs: 4382707 -> 4382707 (0.00%)
> instructions in affected programs:     0 -> 0
> helped:                                0
> HURT:                                  0
> GAINED:                                2089
> LOST:                                  0
>
> No other platforms affected in shader-db.

We can probably do a little better by bailing in the generator when we
emit an IF instruction, since some optimizations like
opt_peephole_sel() and opt_peephole_predicated_break() remove control
flow.

But this is an improvement by itself, so

Reviewed-by: Matt Turner <mattst88 at gmail.com>