[Mesa-dev] [PATCH] glsl: Add an optimization pass to flatten simple nested if blocks.

[Matt Turner]

On Wed, Apr 3, 2013 at 11:56 PM, Kenneth Graunke <kenneth at whitecape.org>wrote:

> GLBenchmark 2.7's shaders contain conditional blocks like:
>
> if (x) {
>     if (y) {
>         ...
>     }
> }
>
> where the outer conditional's then clause contains exactly one statement
> (the nested if) and there are no else clauses.  This can easily be
> optimized into:
>
> if (x && y) {
>     ...
> }
>
> This saves a few instructions in GLBenchmark 2.7:
>
>     total instructions in shared programs: 11833 -> 11649 (-1.55%)
>     instructions in affected programs:     8234 -> 8050 (-2.23%)
>
> It also helps CS:GO slightly (-0.05%/-0.22%).  More importantly,
> however, it simplifies the control flow graph, which could enable other
> optimizations.
>
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
>

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

Any measurable performance improvement?
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