mesa: don't push/pop default texture attributes redundantly

Since default texture objects are bound in almost all texture units and all
texture targets, we can skip saving and restoring their attributes if we
just do that for default texture objects outside the loop saving all texture
units.

This reduces CPU time spent in glPushAttrib from 2.1% to 1.35% in one
subtest of viewperf13/catia.

Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8181>

src/mesa/main/attrib.c

@@ -262,6 +262,19 @@ _mesa_PushAttrib(GLbitfield mask)
       memcpy(&head->Texture.FixedFuncUnit, &ctx->Texture.FixedFuncUnit,
              sizeof(ctx->Texture.FixedFuncUnit));
 
+      /* Copy/save contents of default texture objects. They are almost
+       * always bound, so this can be done unconditionally.
+       *
+       * We save them separately, so that we don't have to save them in every
+       * texture unit where they are bound. This decreases CPU overhead.
+       */
+      for (tex = 0; tex < NUM_TEXTURE_TARGETS; tex++) {
+         struct gl_texture_object *dst = &head->Texture.SavedDefaultObj[tex];
+         struct gl_texture_object *src = ctx->Shared->DefaultTex[tex];
+
+         copy_texture_attribs(dst, src, tex);
+      }
+
       /* copy state/contents of the currently bound texture objects */
       for (u = 0; u < ctx->Const.MaxTextureUnits; u++) {
          head->Texture.LodBias[u] = ctx->Texture.Unit[u].LodBias;
@@ -272,7 +285,9 @@ _mesa_PushAttrib(GLbitfield mask)
 
             dst->Name = src->Name;
 
-            copy_texture_attribs(dst, src, tex);
+            /* Default texture targets are saved separately above. */
+            if (src->Name != 0)
+               copy_texture_attribs(dst, src, tex);
          }
       }
       _mesa_unlock_context_textures(ctx);
@@ -626,15 +641,27 @@ pop_texture_group(struct gl_context *ctx, struct gl_texture_attrib_node *texstat
             texObj = _mesa_get_tex_unit(ctx, u)->CurrentTex[tgt];
          }
 
+         /* Default texture object states are restored separately below. */
+         if (texObj->Name == 0)
+            continue;
+
          if (!copy_texture_attribs(texObj, savedObj, tgt))
             continue;
 
          /* GL_ALL_ATTRIB_BITS means all pnames. (internal) */
-         if (texObj->Name != 0 && ctx->Driver.TexParameter)
+         if (ctx->Driver.TexParameter)
             ctx->Driver.TexParameter(ctx, texObj, GL_ALL_ATTRIB_BITS);
       }
    }
 
+   /* Restore default texture object states. */
+   for (gl_texture_index tex = 0; tex < NUM_TEXTURE_TARGETS; tex++) {
+      struct gl_texture_object *dst = ctx->Shared->DefaultTex[tex];
+      const struct gl_texture_object *src = &texstate->SavedDefaultObj[tex];
+
+      copy_texture_attribs(dst, src, tex);
+   }
+
    if (!ctx->Driver.TexEnv && !ctx->Driver.TexGen) {
       ctx->Texture._TexGenEnabled = texstate->_TexGenEnabled;
       ctx->Texture._GenFlags = texstate->_GenFlags;

src/mesa/main/mtypes.h

@@ -5053,6 +5053,9 @@ struct gl_texture_attrib_node
    struct gl_fixedfunc_texture_unit FixedFuncUnit[MAX_TEXTURE_COORD_UNITS];
    GLfloat LodBias[MAX_TEXTURE_UNITS];
 
+   /** Saved default texture object state. */
+   struct gl_texture_object SavedDefaultObj[NUM_TEXTURE_TARGETS];
+
    /* For saving per texture object state (wrap modes, filters, etc),
     * SavedObj[][].Target is unused, so the value is invalid.
     */