nir: Add variable debug info to instructions

Allows for annotating defs with variable names.

Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33141>

src/compiler/nir/nir.h

@@ -2752,6 +2752,11 @@ typedef struct nir_instr_debug_info {
    /* Line in the output of nir_print_shader. 0 if uninitialized. */
    uint32_t nir_line;
 
+   /* Contains the name of the variable/input/... that was lowered to this
+    * def by a pass like nir_lower_vars_to_ssa.
+    */
+   char *variable_name;
+
    /* The nir_instr has to be the last field since it has a varying size. */
    nir_instr instr;
 } nir_instr_debug_info;

src/compiler/nir/nir_clone.c

@@ -249,6 +249,7 @@ clone_debug_info(clone_state *state, nir_instr *ninstr, const nir_instr *instr)
    const nir_instr_debug_info *debug_info = nir_instr_get_debug_info((void *)instr);
 
    ndebug_info->filename = clone_string(state, debug_info->filename);
+   ndebug_info->variable_name = clone_string(state, debug_info->variable_name);
 
    ndebug_info->line = debug_info->line;
    ndebug_info->column = debug_info->column;

src/compiler/nir/nir_print.c

@@ -137,6 +137,12 @@ print_def(nir_def *def, print_state *state)
            divergence_status(state, def->divergent),
            def->bit_size, sizes[def->num_components],
            padding, "", state->def_prefix, def->index);
+
+   if (state->shader->has_debug_info) {
+      nir_instr_debug_info *debug_info = nir_instr_get_debug_info(def->parent_instr);
+      if (debug_info->variable_name)
+         fprintf(fp, ".%s", debug_info->variable_name);
+   }
 }
 
 static unsigned
@@ -400,6 +406,12 @@ print_src(const nir_src *src, print_state *state, nir_alu_type src_type)
    fprintf(fp, "%s%u", state->def_prefix, src->ssa->index);
    nir_instr *instr = src->ssa->parent_instr;
 
+   if (state->shader->has_debug_info) {
+      nir_instr_debug_info *debug_info = nir_instr_get_debug_info(instr);
+      if (debug_info->variable_name)
+         fprintf(fp, ".%s", debug_info->variable_name);
+   }
+
    if (instr->type == nir_instr_type_load_const && !NIR_DEBUG(PRINT_NO_INLINE_CONSTS)) {
       nir_load_const_instr *load_const = nir_instr_as_load_const(instr);
       fprintf(fp, " ");

src/compiler/nir/nir_serialize.c

@@ -1605,6 +1605,11 @@ read_call(read_ctx *ctx)
    return call;
 }
 
+enum nir_serialize_debug_info_flags {
+   NIR_SERIALIZE_FILENAME = 1 << 0,
+   NIR_SERIALIZE_VARIABLE_NAME = 1 << 1,
+};
+
 static void
 write_debug_info(write_ctx *ctx, const nir_instr *instr)
 {
@@ -1616,9 +1621,17 @@ write_debug_info(write_ctx *ctx, const nir_instr *instr)
 
    blob_write_uint32(ctx->blob, debug_info->nir_line);
 
-   blob_write_uint8(ctx->blob, !!debug_info->filename);
+   enum nir_serialize_debug_info_flags flags = 0;
+   if (debug_info->filename)
+      flags |= NIR_SERIALIZE_FILENAME;
+   if (debug_info->variable_name)
+      flags |= NIR_SERIALIZE_VARIABLE_NAME;
+   blob_write_uint8(ctx->blob, flags);
+
    if (debug_info->filename)
       blob_write_string(ctx->blob, debug_info->filename);
+   if (debug_info->variable_name)
+      blob_write_string(ctx->blob, debug_info->variable_name);
 }
 
 static void
@@ -1632,8 +1645,9 @@ read_debug_info(read_ctx *ctx, nir_instr_debug_info *debug_info)
 
    debug_info->nir_line = blob_read_uint32(ctx->blob);
 
-   bool has_filename = blob_read_uint8(ctx->blob);
+   enum nir_serialize_debug_info_flags flags = blob_read_uint8(ctx->blob);
-   if (has_filename) {
+
+   if (flags & NIR_SERIALIZE_FILENAME) {
       const char *filename = blob_read_string(ctx->blob);
 
       struct hash_entry *entry = _mesa_hash_table_search(ctx->strings, filename);
@@ -1644,6 +1658,18 @@ read_debug_info(read_ctx *ctx, nir_instr_debug_info *debug_info)
          _mesa_hash_table_insert(ctx->strings, filename, debug_info->filename);
       }
    }
+
+   if (flags & NIR_SERIALIZE_VARIABLE_NAME) {
+      const char *variable_name = blob_read_string(ctx->blob);
+
+      struct hash_entry *entry = _mesa_hash_table_search(ctx->strings, variable_name);
+      if (entry) {
+         debug_info->variable_name = entry->data;
+      } else {
+         debug_info->variable_name = ralloc_strdup(ctx->nir, variable_name);
+         _mesa_hash_table_insert(ctx->strings, variable_name, debug_info->variable_name);
+      }
+   }
 }
 
 static void