[Mesa-dev] [PATCH] mesa: debug facility to replace shaders when running apps

[Eero Tamminen]

Hi,

MESA_GLSL environment variable has few options which also dump shaders, 
but they're not useful for this because:

* "dump": outputs "mangled" (per-processed) GLSL, to stdout

* "log": outputs GLSL to file, but it goes to current directory (which 
app can change), adds comment to beginning of shader and doesn't provide 
hash that would match one used by GLSL reading


Main usage for the patch on my part will be investigating effect of each 
individual shader to the applications' performance (e.g. by replacing 
each shader by a dummy one, one at the time, and measuring the impact).


	- Eero

On 08/21/2015 11:17 AM, Tapani Pälli wrote:
> Patch adds shader source and replace functionality in to the compiler.
> This can be used to debug individual (failing) shaders and measure
> performance impact of each shader.
>
> Functionality is controlled via 2 environment variables:
>
> MESA_SHADER_DUMP - path where shader sources are dumped
> MESA_SHADER_READ - path where replacement shaders are read
>
> Signed-off-by: Tapani Pälli <tapani.palli at intel.com>
> Suggested-by: Eero Tamminen <eero.t.tamminen at intel.com>
> ---
>   src/glsl/glsl_parser_extras.cpp | 76 +++++++++++++++++++++++++++++++++++++++++
>   src/mesa/main/mtypes.h          |  2 +-
>   2 files changed, 77 insertions(+), 1 deletion(-)
>
> diff --git a/src/glsl/glsl_parser_extras.cpp b/src/glsl/glsl_parser_extras.cpp
> index 46896d7..17b79b0 100644
> --- a/src/glsl/glsl_parser_extras.cpp
> +++ b/src/glsl/glsl_parser_extras.cpp
> @@ -1570,10 +1570,86 @@ set_shader_inout_layout(struct gl_shader *shader,
>
>   extern "C" {
>
> +#include <sys/stat.h>
> +#include "util/mesa-sha1.h"
> +
> +static void
> +generate_sha1(struct gl_shader *shader, char sha_str[64])
> +{
> +   unsigned char sha[20];
> +   _mesa_sha1_compute(shader->Source, strlen(shader->Source), sha);
> +   _mesa_sha1_format(sha_str, sha);
> +}
> +
> +static void
> +construct_name(struct gl_shader *shader, const char *path,
> +               char *name, unsigned length)
> +{
> +   char sha[64];
> +   static const char *types[] = {
> +      "VS", "TC", "TE", "GS", "FS", "CS",
> +   };
> +
> +   generate_sha1(shader, sha);
> +   _mesa_snprintf(name, length, "%s/%s_%s.glsl", path, types[shader->Stage],
> +                  sha);
> +}
> +
> +static void
> +read_shader(struct gl_shader *shader)
> +{
> +   char name[PATH_MAX];
> +   static char *read_path = getenv("MESA_SHADER_READ");
> +
> +   if (!read_path)
> +      return;
> +
> +   construct_name(shader, read_path, name, PATH_MAX);
> +
> +   FILE *in = fopen(name, "r");
> +   if (in) {
> +      fseek(in, 0, SEEK_END);
> +      long size = ftell(in);
> +      rewind(in);
> +      char *source = (char *) malloc(size + 1);
> +      fread(source, size, 1, in);
> +      source[size] = '\0';
> +      free(shader->Source);
> +      shader->Source = source;
> +      fclose(in);
> +   }
> +}
> +
> +static void
> +dump_shader(struct gl_shader *shader)
> +{
> +   char name[PATH_MAX];
> +   static char *dump_path = getenv("MESA_SHADER_DUMP");
> +
> +   if (!dump_path)
> +      return;
> +
> +   construct_name(shader, dump_path, name, PATH_MAX);
> +
> +   FILE *out = fopen(name, "w");
> +   if (out) {
> +      fprintf(out, "%s", shader->Source);
> +      fclose(out);
> +   } else {
> +      fprintf(stderr, "could not open %s for dumping shader\n", name);
> +   }
> +}
> +
>   void
>   _mesa_glsl_compile_shader(struct gl_context *ctx, struct gl_shader *shader,
>                             bool dump_ast, bool dump_hir)
>   {
> +   /* Dump original shader source to MESA_SHADER_DUMP and replace
> +    * if corresponding entry found from MESA_SHADER_READ path.
> +    */
> +   dump_shader(shader);
> +   read_shader(shader);
> +
>      struct _mesa_glsl_parse_state *state =
>         new(shader) _mesa_glsl_parse_state(ctx, shader->Stage, shader);
>      const char *source = shader->Source;
> diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
> index f61a245..fb47a22 100644
> --- a/src/mesa/main/mtypes.h
> +++ b/src/mesa/main/mtypes.h
> @@ -2346,7 +2346,7 @@ struct gl_shader
>      bool IsES;              /**< True if this shader uses GLSL ES */
>
>      GLuint SourceChecksum;       /**< for debug/logging purposes */
> -   const GLchar *Source;  /**< Source code string */
> +   GLchar *Source;  /**< Source code string */
>
>      struct gl_program *Program;  /**< Post-compile assembly code */
>      GLchar *InfoLog;
>