src/glsl/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 struct global_to_local_state {
  36    nir_function_impl *impl;
  37    /* A hash table keyed on variable pointers that stores the unique
  38     * nir_function_impl that uses the given variable.  If a variable is
  39     * used in multiple functions, the data for the given key will be NULL.
  40     */
  41    struct hash_table *var_func_table;
  42 };
  43
  44 static bool
  45 mark_global_var_uses_block(nir_block *block, void *void_state)
  46 {
  47    struct global_to_local_state *state = void_state;
  48
  49    nir_foreach_instr(block, instr) {
  50       if (instr->type != nir_instr_type_intrinsic)
  51          continue;
  52
  53       nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
  54       unsigned num_vars = nir_intrinsic_infos[intrin->intrinsic].num_variables;
  55
  56       for (unsigned i = 0; i < num_vars; i++) {
  57          nir_variable *var = intrin->variables[i]->var;
  58          if (var->data.mode != nir_var_global)
  59             continue;
  60
  61          struct hash_entry *entry =
  62             _mesa_hash_table_search(state->var_func_table, var);
  63
  64          if (entry) {
  65             if (entry->data != state->impl)
  66                entry->data = NULL;
  67          } else {
  68             _mesa_hash_table_insert(state->var_func_table, var, state->impl);
  69          }
  70       }
  71    }
  72
  73    return true;
  74 }
  75
  76 void
  77 nir_lower_global_vars_to_local(nir_shader *shader)
  78 {
  79    struct global_to_local_state state;
  80
  81    state.var_func_table = _mesa_hash_table_create(NULL, _mesa_hash_pointer,
  82                                                   _mesa_key_pointer_equal);
  83
  84    nir_foreach_overload(shader, overload) {
  85       if (overload->impl) {
  86          state.impl = overload->impl;
  87          nir_foreach_block(overload->impl, mark_global_var_uses_block, &state);
  88       }
  89    }
  90
  91    struct hash_entry *entry;
  92    hash_table_foreach(state.var_func_table, entry) {
  93       nir_variable *var = (void *)entry->key;
  94       nir_function_impl *impl = entry->data;
  95
  96       assert(var->data.mode == nir_var_global);
  97
  98       if (impl != NULL) {
  99          exec_node_remove(&var->node);
 100          var->data.mode = nir_var_local;
 101          exec_list_push_tail(&impl->locals, &var->node);
 102       }
 103    }
 104
 105    _mesa_hash_table_destroy(state.var_func_table, NULL);
 106 }