glsl/st: move st_nir_opts() into gl compiler common code

This will allow us to use this in future NIR linker work. It also makes
more sense to move it here as the classic drivers are gone, tgsi is
going away and we are merging more of the st into the gl common code.

Reviewed-by: Emma Anholt <emma@anholt.net>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14785>

src/compiler/glsl/gl_nir_linker.c

@@ -36,6 +36,87 @@
  * the counter-part glsl/linker.cpp
  */
 
+void
+gl_nir_opts(nir_shader *nir)
+{
+   bool progress;
+
+   do {
+      progress = false;
+
+      NIR_PASS_V(nir, nir_lower_vars_to_ssa);
+
+      /* Linking deals with unused inputs/outputs, but here we can remove
+       * things local to the shader in the hopes that we can cleanup other
+       * things. This pass will also remove variables with only stores, so we
+       * might be able to make progress after it.
+       */
+      NIR_PASS(progress, nir, nir_remove_dead_variables,
+               nir_var_function_temp | nir_var_shader_temp |
+               nir_var_mem_shared,
+               NULL);
+
+      NIR_PASS(progress, nir, nir_opt_copy_prop_vars);
+      NIR_PASS(progress, nir, nir_opt_dead_write_vars);
+
+      if (nir->options->lower_to_scalar) {
+         NIR_PASS_V(nir, nir_lower_alu_to_scalar,
+                    nir->options->lower_to_scalar_filter, NULL);
+         NIR_PASS_V(nir, nir_lower_phis_to_scalar, false);
+      }
+
+      NIR_PASS_V(nir, nir_lower_alu);
+      NIR_PASS_V(nir, nir_lower_pack);
+      NIR_PASS(progress, nir, nir_copy_prop);
+      NIR_PASS(progress, nir, nir_opt_remove_phis);
+      NIR_PASS(progress, nir, nir_opt_dce);
+      if (nir_opt_trivial_continues(nir)) {
+         progress = true;
+         NIR_PASS(progress, nir, nir_copy_prop);
+         NIR_PASS(progress, nir, nir_opt_dce);
+      }
+      NIR_PASS(progress, nir, nir_opt_if, false);
+      NIR_PASS(progress, nir, nir_opt_dead_cf);
+      NIR_PASS(progress, nir, nir_opt_cse);
+      NIR_PASS(progress, nir, nir_opt_peephole_select, 8, true, true);
+
+      NIR_PASS(progress, nir, nir_opt_phi_precision);
+      NIR_PASS(progress, nir, nir_opt_algebraic);
+      NIR_PASS(progress, nir, nir_opt_constant_folding);
+
+      if (!nir->info.flrp_lowered) {
+         unsigned lower_flrp =
+            (nir->options->lower_flrp16 ? 16 : 0) |
+            (nir->options->lower_flrp32 ? 32 : 0) |
+            (nir->options->lower_flrp64 ? 64 : 0);
+
+         if (lower_flrp) {
+            bool lower_flrp_progress = false;
+
+            NIR_PASS(lower_flrp_progress, nir, nir_lower_flrp,
+                     lower_flrp,
+                     false /* always_precise */);
+            if (lower_flrp_progress) {
+               NIR_PASS(progress, nir,
+                        nir_opt_constant_folding);
+               progress = true;
+            }
+         }
+
+         /* Nothing should rematerialize any flrps, so we only need to do this
+          * lowering once.
+          */
+         nir->info.flrp_lowered = true;
+      }
+
+      NIR_PASS(progress, nir, nir_opt_undef);
+      NIR_PASS(progress, nir, nir_opt_conditional_discard);
+      if (nir->options->max_unroll_iterations) {
+         NIR_PASS(progress, nir, nir_opt_loop_unroll);
+      }
+   } while (progress);
+}
+
 static bool
 can_remove_uniform(nir_variable *var, UNUSED void *data)
 {

src/compiler/glsl/gl_nir_linker.h

@@ -42,6 +42,8 @@ struct gl_nir_linker_options {
                                                 nir_var_mem_ssbo | \
                                                 nir_var_image)
 
+void gl_nir_opts(nir_shader *nir);
+
 bool gl_nir_link_spirv(const struct gl_constants *consts,
                        struct gl_shader_program *prog,
                        const struct gl_nir_linker_options *options);