nir: rename nir_io_glsl_opt_varyings to nir_io_dont_optimize and deprecate it

The meaning is negated.

This NIR option is deprecated and shouldn't be used. It means any IO
optimizations can be disabled and it's a currently a workaround for zink,
which is the only driver that asks for it by default. The original option
is replaced by an environment variable for the GLSL linker.

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32173>

src/compiler/glsl/gl_nir_linker.c

@@ -1513,7 +1513,7 @@ gl_nir_lower_optimize_varyings(const struct gl_constants *consts,
    unsigned num_shaders = 0;
    unsigned max_ubos = UINT_MAX;
    unsigned max_uniform_comps = UINT_MAX;
-   bool optimize_io = true;
+   bool optimize_io = !debug_get_bool_option("MESA_GLSL_DISABLE_IO_OPT", false);
 
    for (unsigned i = 0; i < MESA_SHADER_STAGES; i++) {
       struct gl_linked_shader *shader = prog->_LinkedShaders[i];
@@ -1532,7 +1532,7 @@ gl_nir_lower_optimize_varyings(const struct gl_constants *consts,
                                consts->Program[i].MaxUniformComponents);
       max_ubos = MIN2(max_ubos, consts->Program[i].MaxUniformBlocks);
       num_shaders++;
-      optimize_io &= !!(nir->options->io_options & nir_io_glsl_opt_varyings);
+      optimize_io &= !(nir->options->io_options & nir_io_dont_optimize);
    }
 
    /* Lower IO derefs to load and store intrinsics. */

src/compiler/nir/nir.h

@@ -3859,9 +3859,12 @@ typedef enum {
    nir_io_has_intrinsics = BITFIELD_BIT(16),
 
    /**
-    * Run nir_opt_varyings in the GLSL linker.
+    * Don't run nir_opt_varyings and nir_opt_vectorize_io.
+    *
+    * This option is deprecated and is a hack. DO NOT USE.
+    * Use MESA_GLSL_DISABLE_IO_OPT=1 instead.
     */
-   nir_io_glsl_opt_varyings = BITFIELD_BIT(17),
+   nir_io_dont_optimize = BITFIELD_BIT(17),
 } nir_io_options;
 
 typedef enum {

src/gallium/drivers/radeonsi/si_get.c

@@ -1577,7 +1577,7 @@ void si_init_screen_get_functions(struct si_screen *sscreen)
     */
    options->force_f2f16_rtz = true;
    options->io_options |= (!has_mediump ? nir_io_mediump_is_32bit : 0) | nir_io_has_intrinsics |
-                          (sscreen->options.optimize_io ? nir_io_glsl_opt_varyings : 0);
+                          (sscreen->options.optimize_io ? 0 : nir_io_dont_optimize);
    options->lower_mediump_io = has_mediump ? si_lower_mediump_io : NULL;
    /* HW supports indirect indexing for: | Enabled in driver
     * -------------------------------------------------------

src/gallium/drivers/zink/zink_compiler.c

@@ -1402,8 +1402,6 @@ zink_screen_init_compiler(struct zink_screen *screen)
    }
 
    if (screen->driver_compiler_workarounds.io_opt) {
-      screen->nir_options.io_options |= nir_io_glsl_opt_varyings;
-
       switch (zink_driverid(screen)) {
       case VK_DRIVER_ID_MESA_RADV:
       case VK_DRIVER_ID_AMD_OPEN_SOURCE:
@@ -1416,6 +1414,8 @@ zink_screen_init_compiler(struct zink_screen *screen)
          screen->nir_options.varying_expression_max_cost = amd_varying_expression_max_cost;
          screen->nir_options.varying_estimate_instr_cost = amd_varying_estimate_instr_cost;
       }
+   } else {
+      screen->nir_options.io_options |= nir_io_dont_optimize;
    }
 
    /*

src/util/disk_cache_os.c

@@ -1005,7 +1005,10 @@ disk_cache_enabled()
                  "use MESA_SHADER_CACHE_DISABLE instead ***\n");
    }
 
-   if (debug_get_bool_option(envvar_name, disable_by_default))
+   if (debug_get_bool_option(envvar_name, disable_by_default) ||
+       /* MESA_GLSL_DISABLE_IO_OPT must disable the cache to get expected
+        * results because it only takes effect on a cache miss. */
+       debug_get_bool_option("MESA_GLSL_DISABLE_IO_OPT", false))
       return false;
 
    return true;