[Mesa-dev] [PATCH] glsl, st/shader_cache: check the whole sha1 for zero

[Timothy Arceri]

On 27/03/17 03:30, Grazvydas Ignotas wrote:
> The checks were only looking at the first byte, while the intention
> seems to be to check if the whole sha1 is zero. This prevented all
> shaders with first byte zero in their sha1 from being saved.
>
> This shaves around a second from Deus Ex load time on a hot cache.
>
> Signed-off-by: Grazvydas Ignotas <notasas at gmail.com>
> ---
>  src/compiler/glsl/shader_cache.cpp       | 3 ++-
>  src/mesa/state_tracker/st_shader_cache.c | 3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/src/compiler/glsl/shader_cache.cpp b/src/compiler/glsl/shader_cache.cpp
> index 274bb8c..ea1bc01 100644
> --- a/src/compiler/glsl/shader_cache.cpp
> +++ b/src/compiler/glsl/shader_cache.cpp
> @@ -1219,11 +1219,12 @@ shader_cache_write_program_metadata(struct gl_context *ctx,
>      * generate a source from.
>      *
>      * TODO: In future we should use another method to generate a key for ff
>      * programs.
>      */
> -   if (*prog->data->sha1 == 0)
> +   static const char zero[sizeof(prog->data->sha1)] = {0};

I don't think this will compile on Windows. Just hard-code these to 20, 
if you are really concerned you could use CACHE_KEY_SIZE instead.

Otherwise nice catch.

Reviewed-by: Timothy Arceri <tarceri at itsqueeze.com>

> +   if (memcmp(prog->data->sha1, zero, sizeof(prog->data->sha1)) == 0)
>        return;
>
>     struct blob *metadata = blob_create();
>
>     write_uniforms(metadata, prog);
> diff --git a/src/mesa/state_tracker/st_shader_cache.c b/src/mesa/state_tracker/st_shader_cache.c
> index 061b272..e8c7289 100644
> --- a/src/mesa/state_tracker/st_shader_cache.c
> +++ b/src/mesa/state_tracker/st_shader_cache.c
> @@ -62,11 +62,12 @@ st_store_tgsi_in_disk_cache(struct st_context *st, struct gl_program *prog,
>        return;
>
>     /* Exit early when we are dealing with a ff shader with no source file to
>      * generate a source from.
>      */
> -   if (*prog->sh.data->sha1 == 0)
> +   static const char zero[sizeof(prog->sh.data->sha1)] = {0};
> +   if (memcmp(prog->sh.data->sha1, zero, sizeof(prog->sh.data->sha1)) == 0)
>        return;
>
>     unsigned char *sha1;
>     struct blob *blob = blob_create();
>
>