[Mesa-dev] [PATCH 1/2] glsl: Don't rehash the values when copying to new table

[Vladislav Egorov]

I've looked into it recently (I'm working on series of many various 
trivial optimizations)

and it's faster to just memcpy() it. Just throwing out superfluous 
hashing still keeps slow

hash-table insertion around -- with resizing, rehashing, memory 
allocation/deallocation, internal

hash-function through integer division, collisions and so on. It 
produces a nice speed improvement

actually. It's possible to explore approaches without any copying at 
LOOP/IF entering at all,

but I am not sure it will improve performance.


30.12.2016 02:49, Thomas Helland пишет:
> Really, we should have some kind of function for copying the whole table,
> but this will work for now.
> ---
>   src/compiler/glsl/opt_copy_propagation.cpp | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/src/compiler/glsl/opt_copy_propagation.cpp b/src/compiler/glsl/opt_copy_propagation.cpp
> index 247c498..e9f82e0 100644
> --- a/src/compiler/glsl/opt_copy_propagation.cpp
> +++ b/src/compiler/glsl/opt_copy_propagation.cpp
> @@ -210,7 +210,8 @@ ir_copy_propagation_visitor::handle_if_block(exec_list *instructions)
>      /* Populate the initial acp with a copy of the original */
>      struct hash_entry *entry;
>      hash_table_foreach(orig_acp, entry) {
> -      _mesa_hash_table_insert(acp, entry->key, entry->data);
> +      _mesa_hash_table_insert_pre_hashed(acp, entry->hash,
> +                                         entry->key, entry->data);
>      }
>   
>      visit_list_elements(this, instructions);
> @@ -259,7 +260,8 @@ ir_copy_propagation_visitor::handle_loop(ir_loop *ir, bool keep_acp)
>      if (keep_acp) {
>         struct hash_entry *entry;
>         hash_table_foreach(orig_acp, entry) {
> -         _mesa_hash_table_insert(acp, entry->key, entry->data);
> +         _mesa_hash_table_insert_pre_hashed(acp, entry->hash,
> +                                            entry->key, entry->data);
>         }
>      }
>