[Mesa-dev] [PATCH 2/2] glsl: don't recompile a shader on fallback unless needed

[Timothy Arceri]

Because we optimistically skip compiling shaders if we have seen them
before we may need to compile them later at link time if they haven't
yet been use in a specific combination to create a program.

Rather than always recompiling we take advantage of the
gl_compile_status enum introduced in the previous patch to only
compile when we have previously skipped compilation.

This should help with regressions in app start-up times on cold cache
runs, compared with no cache.
---
 src/compiler/glsl/glsl_parser_extras.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/compiler/glsl/glsl_parser_extras.cpp b/src/compiler/glsl/glsl_parser_extras.cpp
index 59114a7..776636c 100644
--- a/src/compiler/glsl/glsl_parser_extras.cpp
+++ b/src/compiler/glsl/glsl_parser_extras.cpp
@@ -1945,20 +1945,27 @@ _mesa_glsl_compile_shader(struct gl_context *ctx, struct gl_shader *shader,
          if (ctx->_Shader->Flags & GLSL_CACHE_INFO) {
             fprintf(stderr, "deferring compile of shader: %s\n",
                     _mesa_sha1_format(buf, shader->sha1));
          }
          shader->CompileStatus = compile_skipped;
 
          free((void *)shader->FallbackSource);
          shader->FallbackSource = NULL;
          return;
       }
+   } else {
+      /* We should only ever end up here if a re-compile has been forced by a
+       * shader cache miss. In which case we can skip the compile if its
+       * already be done by a previous fallback or the initial compile call.
+       */
+      if (shader->CompileStatus == compile_success)
+         return;
    }
 
    if (!state->error) {
      _mesa_glsl_lexer_ctor(state, source);
      _mesa_glsl_parse(state);
      _mesa_glsl_lexer_dtor(state);
      do_late_parsing_checks(state);
    }
 
    if (dump_ast) {
-- 
2.9.3