src/compiler/nir/nir_lower_global_vars_to_local.c

   1 /*
   2  * Copyright © 2014 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  *
  23  * Authors:
  24  *    Jason Ekstrand (jason@jlekstrand.net)
  25  *
  26  */
  27
  28 /*
  29  * This lowering pass detects when a global variable is only being used by
  30  * one function and makes it local to that function
  31  */
  32
  33 #include "nir.h"
  34
  35 static bool
  36 mark_global_var_uses_block(nir_block *block, nir_function_impl *impl,
  37                            struct hash_table *var_func_table)
  38 {
  39    nir_foreach_instr(instr, block) {
  40       if (instr->type != nir_instr_type_intrinsic)
  41          continue;
  42
  43       nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
  44       unsigned num_vars = nir_intrinsic_infos[intrin->intrinsic].num_variables;
  45
  46       for (unsigned i = 0; i < num_vars; i++) {
  47          nir_variable *var = intrin->variables[i]->var;
  48          if (var->data.mode != nir_var_global)
  49             continue;
  50
  51          struct hash_entry *entry =
  52             _mesa_hash_table_search(var_func_table, var);
  53
  54          if (entry) {
  55             if (entry->data != impl)
  56                entry->data = NULL;
  57          } else {
  58             _mesa_hash_table_insert(var_func_table, var, impl);
  59          }
  60       }
  61    }
  62
  63    return true;
  64 }
  65
  66 bool
  67 nir_lower_global_vars_to_local(nir_shader *shader)
  68 {
  69    bool progress = false;
  70
  71    /* A hash table keyed on variable pointers that stores the unique
  72     * nir_function_impl that uses the given variable.  If a variable is
  73     * used in multiple functions, the data for the given key will be NULL.
  74     */
  75    struct hash_table *var_func_table =
  76       _mesa_hash_table_create(NULL, _mesa_hash_pointer,
  77                               _mesa_key_pointer_equal);
  78
  79    nir_assert_lowered_derefs(shader, nir_lower_load_store_derefs | nir_lower_interp_derefs |
  80          nir_lower_atomic_counter_derefs | nir_lower_atomic_derefs | nir_lower_image_derefs);
  81
  82    nir_foreach_function(function, shader) {
  83       if (function->impl) {
  84          nir_foreach_block(block, function->impl)
  85             mark_global_var_uses_block(block, function->impl, var_func_table);
  86       }
  87    }
  88
  89    struct hash_entry *entry;
  90    hash_table_foreach(var_func_table, entry) {
  91       nir_variable *var = (void *)entry->key;
  92       nir_function_impl *impl = entry->data;
  93
  94       assert(var->data.mode == nir_var_global);
  95
  96       if (impl != NULL) {
  97          exec_node_remove(&var->node);
  98          var->data.mode = nir_var_local;
  99          exec_list_push_tail(&impl->locals, &var->node);
 100          nir_metadata_preserve(impl, nir_metadata_block_index |
 101                                      nir_metadata_dominance |
 102                                      nir_metadata_live_ssa_defs);
 103          progress = true;
 104       }
 105    }
 106
 107    _mesa_hash_table_destroy(var_func_table, NULL);
 108
 109    return progress;
 110 }