[Mesa-dev] [PATCH 1/3] nir/dominance: Simplify and expose the dominance intersection function

[Connor Abbott]

I'd rather keep it the way it was, since that's how it's presented as
pseudocode in the paper and someone reading this is more likely to be
confused by a function with the exact same name as in the paper but a
different implementation.

On Fri, Feb 6, 2015 at 5:12 PM, Jason Ekstrand <jason at jlekstrand.net> wrote:
> Before the function involved three loops and three different branching
> conditions.  Now it involves one loop and one if statement.  This is a
> little simpler.
> ---
>  src/glsl/nir/nir.h           |  2 ++
>  src/glsl/nir/nir_dominance.c | 16 ++++++++++++++--
>  2 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
> index 4cb2e92..886dcd2 100644
> --- a/src/glsl/nir/nir.h
> +++ b/src/glsl/nir/nir.h
> @@ -1500,6 +1500,8 @@ static inline void nir_validate_shader(nir_shader *shader) { }
>  void nir_calc_dominance_impl(nir_function_impl *impl);
>  void nir_calc_dominance(nir_shader *shader);
>
> +nir_block *nir_dominance_lca(nir_block *b1, nir_block *b2);
> +
>  void nir_dump_dom_tree_impl(nir_function_impl *impl, FILE *fp);
>  void nir_dump_dom_tree(nir_shader *shader, FILE *fp);
>
> diff --git a/src/glsl/nir/nir_dominance.c b/src/glsl/nir/nir_dominance.c
> index 67fdcc6..1022692 100644
> --- a/src/glsl/nir/nir_dominance.c
> +++ b/src/glsl/nir/nir_dominance.c
> @@ -65,9 +65,9 @@ intersect(nir_block *b1, nir_block *b2)
>         * because we index blocks from beginning -> end (i.e. reverse
>         * post-order) instead of post-order like they assume.
>         */
> -      while (b1->index > b2->index)
> +      if (b1->index > b2->index)
>           b1 = b1->imm_dom;
> -      while (b2->index > b1->index)
> +      else
>           b2 = b2->imm_dom;
>     }
>
> @@ -212,6 +212,18 @@ nir_calc_dominance(nir_shader *shader)
>     }
>  }
>
> +nir_block *
> +nir_dominance_lca(nir_block *b1, nir_block *b2)
> +{
> +   assert(nir_cf_node_get_function(&b1->cf_node) ==
> +          nir_cf_node_get_function(&b2->cf_node));
> +
> +   assert(nir_cf_node_get_function(&b1->cf_node)->valid_metadata &
> +          nir_metadata_dominance);
> +
> +   return intersect(b1, b2);
> +}
> +
>  static bool
>  dump_block_dom(nir_block *block, void *state)
>  {
> --
> 2.2.2
>
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