[Mesa-dev] [PATCH] nir/opt_if: Remove unneeded phis if we make progress

[Samuel Iglesias Gonsálvez]

Thanks a lot for fixing this,

Reviewed-by: Samuel Iglesias Gonsálvez <siglesias at igalia.com>

Sam

On 26/06/18 01:47, Jason Ekstrand wrote:
> Now that SSA values can be derefs and they have special rules, we have
> to be a bit more careful about our LCSSA phis.  In particular, we need
> to clean up in case LCSSA ended up creating a phi node for a deref.
> This fixes validation issues with some Vulkan CTS tests with the new
> deref instructions.
>
> Cc: Samuel Iglesias Gonsálvez <siglesias at igalia.com>
> ---
>  src/compiler/nir/nir.h                 | 1 +
>  src/compiler/nir/nir_opt_if.c          | 7 +++++++
>  src/compiler/nir/nir_opt_remove_phis.c | 6 +++---
>  3 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> index be7b92dd7d2..c16ce547642 100644
> --- a/src/compiler/nir/nir.h
> +++ b/src/compiler/nir/nir.h
> @@ -2903,6 +2903,7 @@ bool nir_opt_move_load_ubo(nir_shader *shader);
>  
>  bool nir_opt_peephole_select(nir_shader *shader, unsigned limit);
>  
> +bool nir_opt_remove_phis_impl(nir_function_impl *impl);
>  bool nir_opt_remove_phis(nir_shader *shader);
>  
>  bool nir_opt_shrink_load(nir_shader *shader);
> diff --git a/src/compiler/nir/nir_opt_if.c b/src/compiler/nir/nir_opt_if.c
> index 863ca630fbd..ec5bf1c9027 100644
> --- a/src/compiler/nir/nir_opt_if.c
> +++ b/src/compiler/nir/nir_opt_if.c
> @@ -403,6 +403,13 @@ nir_opt_if(nir_shader *shader)
>            * that don't dominate their uses.
>            */
>           nir_lower_regs_to_ssa_impl(function->impl);
> +
> +         /* Calling nir_convert_loop_to_lcssa() in opt_peel_loop_initial_if()
> +          * adds extra phi nodes which may not be valid if they're used for
> +          * something such as a deref.  Remove any unneeded phis.
> +          */
> +         nir_opt_remove_phis_impl(function->impl);
> +
>           progress = true;
>        }
>     }
> diff --git a/src/compiler/nir/nir_opt_remove_phis.c b/src/compiler/nir/nir_opt_remove_phis.c
> index b20ff729156..e2d3994c49e 100644
> --- a/src/compiler/nir/nir_opt_remove_phis.c
> +++ b/src/compiler/nir/nir_opt_remove_phis.c
> @@ -139,8 +139,8 @@ remove_phis_block(nir_block *block, nir_builder *b)
>     return progress;
>  }
>  
> -static bool
> -remove_phis_impl(nir_function_impl *impl)
> +bool
> +nir_opt_remove_phis_impl(nir_function_impl *impl)
>  {
>     bool progress = false;
>     nir_builder bld;
> @@ -165,7 +165,7 @@ nir_opt_remove_phis(nir_shader *shader)
>  
>     nir_foreach_function(function, shader)
>        if (function->impl)
> -         progress = remove_phis_impl(function->impl) || progress;
> +         progress = nir_opt_remove_phis_impl(function->impl) || progress;
>  
>     return progress;
>  }

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