nir: store variable names to io instrs during io lowering

this creates a reference between variables and their access instrs
before the variables are deleted, which improves debugging

Acked-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28814>

src/compiler/nir/nir.h

@@ -1909,6 +1909,9 @@ typedef struct {
 
    int const_index[NIR_INTRINSIC_MAX_CONST_INDEX];
 
+   /* a variable name associated with this instr; cannot be modified or freed */
+   const char *name;
+
    nir_src src[];
 } nir_intrinsic_instr;
 

src/compiler/nir/nir_lower_io.c

@@ -39,8 +39,22 @@ struct lower_io_state {
    int (*type_size)(const struct glsl_type *type, bool);
    nir_variable_mode modes;
    nir_lower_io_options options;
+   struct set variable_names;
 };
 
+static const char *
+add_variable_name(struct lower_io_state *state, const char *name)
+{
+   if (!name)
+      return NULL;
+
+   bool found = false;
+   struct set_entry *entry = _mesa_set_search_or_add(&state->variable_names, name, &found);
+   if (!found)
+      entry->key = (void*)ralloc_strdup(state->builder.shader, name);
+   return entry->key;
+}
+
 static nir_intrinsic_op
 ssbo_atomic_for_deref(nir_intrinsic_op deref_op)
 {
@@ -313,6 +327,7 @@ emit_load(struct lower_io_state *state,
    nir_intrinsic_instr *load =
       nir_intrinsic_instr_create(state->builder.shader, op);
    load->num_components = num_components;
+   load->name = add_variable_name(state, var->name);
 
    nir_intrinsic_set_base(load, var->data.driver_location);
    if (nir_intrinsic_has_range(load)) {
@@ -448,6 +463,7 @@ emit_store(struct lower_io_state *state, nir_def *data,
    nir_intrinsic_instr *store =
       nir_intrinsic_instr_create(state->builder.shader, op);
    store->num_components = num_components;
+   store->name = add_variable_name(state, var->name);
 
    store->src[0] = nir_src_for_ssa(data);
 
@@ -769,6 +785,8 @@ nir_lower_io_impl(nir_function_impl *impl,
    state.modes = modes;
    state.type_size = type_size;
    state.options = options;
+   _mesa_set_init(&state.variable_names, state.dead_ctx,
+                  _mesa_hash_string, _mesa_key_string_equal);
 
    ASSERTED nir_variable_mode supported_modes =
       nir_var_shader_in | nir_var_shader_out | nir_var_uniform;

src/compiler/nir/nir_sweep.c

@@ -67,6 +67,9 @@ sweep_block(nir_shader *nir, nir_block *block)
          nir_foreach_phi_src(src, nir_instr_as_phi(instr))
             gc_mark_live(nir->gctx, src);
          break;
+      case nir_instr_type_intrinsic:
+         ralloc_steal(nir, (void*)nir_instr_as_intrinsic(instr)->name);
+         break;
       default:
          break;
       }