glsl: Simplify the built-in function linking code.

Previously, we stored an array of up to 16 additional shaders to link,
as well as a count of how many each shader actually needed.

Since the built-in functions rewrite, all the built-ins are stored in a
single shader.  So all we need is a boolean indicating whether a shader
needs to link against built-ins or not.

During linking, we can avoid creating the temporary array if none of the
shaders being linked need built-ins.  Otherwise, it's simply a copy of
the array that has one additional element.  This is much simpler.

This patch saves approximately 128 bytes of memory per gl_shader object.

Signed-off-by: Kenneth Graunke <[email protected]>
Reviewed-by: Ian Romanick <[email protected]>

1 files changed, 22 insertions, 20 deletions

diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
index 1366077f784..21c1bdd10f1 100644
--- a/src/glsl/linker.cpp
+++ b/src/glsl/linker.cpp
@@ -1405,36 +1405,38 @@ link_intrastage_shaders(void *mem_ctx,
 					      insertion_point, true, linked);
    }
 
-   /* Resolve initializers for global variables in the linked shader.
-    */
-   unsigned num_linking_shaders = num_shaders;
-   for (unsigned i = 0; i < num_shaders; i++)
-      num_linking_shaders += shader_list[i]->num_builtins_to_link;
+   /* Check if any shader needs built-in functions. */
+   bool need_builtins = false;
+   for (unsigned i = 0; i < num_shaders; i++) {
+      if (shader_list[i]->uses_builtin_functions) {
+         need_builtins = true;
+         break;
+      }
+   }
 
-   gl_shader **linking_shaders =
-      (gl_shader **) calloc(num_linking_shaders, sizeof(gl_shader *));
+   bool ok;
+   if (need_builtins) {
+      /* Make a temporary array one larger than shader_list, which will hold
+       * the built-in function shader as well.
+       */
+      gl_shader **linking_shaders = (gl_shader **)
+         calloc(num_shaders + 1, sizeof(gl_shader *));
+      memcpy(linking_shaders, shader_list, num_shaders * sizeof(gl_shader *));
+      linking_shaders[num_shaders] = _mesa_glsl_get_builtin_function_shader();
 
-   memcpy(linking_shaders, shader_list,
-	  sizeof(linking_shaders[0]) * num_shaders);
+      ok = link_function_calls(prog, linked, linking_shaders, num_shaders + 1);
 
-   unsigned idx = num_shaders;
-   for (unsigned i = 0; i < num_shaders; i++) {
-      memcpy(&linking_shaders[idx], shader_list[i]->builtins_to_link,
-	     sizeof(linking_shaders[0]) * shader_list[i]->num_builtins_to_link);
-      idx += shader_list[i]->num_builtins_to_link;
+      free(linking_shaders);
+   } else {
+      ok = link_function_calls(prog, linked, shader_list, num_shaders);
    }
 
-   assert(idx == num_linking_shaders);
 
-   if (!link_function_calls(prog, linked, linking_shaders,
-			    num_linking_shaders)) {
+   if (!ok) {
       ctx->Driver.DeleteShader(ctx, linked);
-      free(linking_shaders);
       return NULL;
    }
 
-   free(linking_shaders);
-
    /* At this point linked should contain all of the linked IR, so
     * validate it to make sure nothing went wrong.
     */