mesa: add force_explicit_uniform_loc_zero workaround

Allows a uniform name to be passed to force_explicit_uniform_loc_zero
allowing us to set that uniform to an explicit location of zero.

Cc: mesa-stable
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
(cherry picked from commit 87ae5cab94)

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/40752>

.pick_status.json

@@ -6294,7 +6294,7 @@
         "description": "mesa: add force_explicit_uniform_loc_zero workaround",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": null,
         "notes": null

src/compiler/glsl/ast_to_hir.cpp

@@ -3379,19 +3379,21 @@ static void
 apply_explicit_location(const struct ast_type_qualifier *qual,
                         ir_variable *var,
                         struct _mesa_glsl_parse_state *state,
-                        YYLTYPE *loc)
+                        YYLTYPE *loc, bool force_explict_uniform_loc_zero)
 {
    bool fail = false;
 
-   unsigned qual_location;
+   unsigned qual_location = 0;
    if (!process_qualifier_constant(state, loc, "location", qual->location,
-                                   &qual_location)) {
+                                   &qual_location) &&
+       !force_explict_uniform_loc_zero) {
       return;
    }
 
    /* Checks for GL_ARB_explicit_uniform_location. */
    if (qual->flags.q.uniform) {
-      if (!state->check_explicit_uniform_location_allowed(loc, var))
+      if (!force_explict_uniform_loc_zero &&
+          !state->check_explicit_uniform_location_allowed(loc, var))
          return;
 
       const struct gl_constants *consts = state->consts;
@@ -3919,8 +3921,13 @@ apply_layout_qualifier_to_variable(const struct ast_type_qualifier *qual,
                        qual_string);
    }
 
-   if (qual->flags.q.explicit_location) {
-      apply_explicit_location(qual, var, state, loc);
+   bool force_explict_uniform_loc_zero =
+      state->ctx->Const.ForceExplicitUniformLocZero && qual->flags.q.uniform &&
+      strcmp(state->ctx->Const.ForceExplicitUniformLocZero, var->name) == 0;
+
+   if (qual->flags.q.explicit_location || force_explict_uniform_loc_zero) {
+      apply_explicit_location(qual, var, state, loc,
+                              force_explict_uniform_loc_zero);
 
       if (qual->flags.q.explicit_component) {
          unsigned qual_component;

src/gallium/auxiliary/pipe-loader/driinfo_gallium.h

@@ -47,6 +47,7 @@ DRI_CONF_SECTION_DEBUG
    DRI_CONF_TRANSCODE_ETC(false)
    DRI_CONF_TRANSCODE_ASTC(false)
    DRI_CONF_ALLOW_COMPRESSED_FALLBACK(true)
+   DRI_CONF_FORCE_EXPLICIT_UNIFORM_LOC_ZERO()
    DRI_CONF_FORCE_GL_VENDOR()
    DRI_CONF_FORCE_GL_RENDERER()
    DRI_CONF_OVERRIDE_VRAM_SIZE()

src/gallium/auxiliary/util/u_driconf.c

@@ -73,6 +73,7 @@ u_driconf_fill_st_options(struct st_config_options *options,
    query_bool_option(transcode_etc);
    query_bool_option(transcode_astc);
    query_bool_option(allow_compressed_fallback);
+   query_string_option(force_explicit_uniform_loc_zero);
    query_string_option(force_gl_vendor);
    query_string_option(force_gl_renderer);
    query_string_option(mesa_extension_override);

src/gallium/frontends/dri/dri_screen.c

@@ -588,6 +588,7 @@ dri_destroy_screen(struct dri_screen *screen)
 {
    dri_release_screen(screen);
 
+   free(screen->options.force_explicit_uniform_loc_zero);
    free(screen->options.force_gl_vendor);
    free(screen->options.force_gl_renderer);
    free(screen->options.mesa_extension_override);

src/gallium/frontends/wgl/stw_device.c

@@ -242,6 +242,7 @@ stw_cleanup(void)
       return;
    }
 
+   free(stw_dev->st_options.force_explicit_uniform_loc_zero);
    free(stw_dev->st_options.force_gl_vendor);
    free(stw_dev->st_options.force_gl_renderer);
    free(stw_dev->st_options.mesa_extension_override);

src/gallium/include/frontend/api.h

@@ -203,6 +203,7 @@ struct st_config_options
    bool transcode_etc;
    bool transcode_astc;
    bool allow_compressed_fallback;
+   char *force_explicit_uniform_loc_zero;
    char *force_gl_vendor;
    char *force_gl_renderer;
    char *mesa_extension_override;

src/mesa/main/consts_exts.h

@@ -931,6 +931,7 @@ struct gl_constants
    /** GL_ARB_spirv_extensions */
    struct spirv_supported_extensions *SpirVExtensions;
 
+   char *ForceExplicitUniformLocZero;
    char *VendorOverride;
    char *RendererOverride;
 

src/mesa/state_tracker/st_extensions.c

@@ -1341,6 +1341,7 @@ void st_init_extensions(struct pipe_screen *screen,
 
    consts->ForceIntegerTexNearest = options->force_integer_tex_nearest;
 
+   consts->ForceExplicitUniformLocZero = options->force_explicit_uniform_loc_zero;
    consts->VendorOverride = options->force_gl_vendor;
    consts->RendererOverride = options->force_gl_renderer;
 

src/util/driconf.h

@@ -259,6 +259,9 @@
    DRI_CONF_OPT_B(glthread_nop_check_framebuffer_status, def, \
                   "glthread always returns GL_FRAMEBUFFER_COMPLETE to prevent synchronization.")
 
+#define DRI_CONF_FORCE_EXPLICIT_UNIFORM_LOC_ZERO() \
+   DRI_CONF_OPT_S_NODEF(force_explicit_uniform_loc_zero, "Forces an explicit uniform location of zero for the uniform.")
+
 #define DRI_CONF_FORCE_GL_VENDOR() \
    DRI_CONF_OPT_S_NODEF(force_gl_vendor, "Override GPU vendor string.")