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

[Tapani Pälli]

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;
-- 
2.4.3