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 void
  36 register_var_use(nir_variable *var, nir_function_impl *impl,
  37                  struct hash_table *var_func_table)
  38 {
  39    if (var->data.mode != nir_var_shader_temp)
  40       return;
  41
  42    struct hash_entry *entry =
  43       _mesa_hash_table_search(var_func_table, var);
  44
  45    if (entry) {
  46       if (entry->data != impl)
  47          entry->data = NULL;
  48    } else {
  49       _mesa_hash_table_insert(var_func_table, var, impl);
  50    }
  51 }
  52
  53 static bool
  54 mark_global_var_uses_block(nir_block *block, nir_function_impl *impl,
  55                            struct hash_table *var_func_table)
  56 {
  57    nir_foreach_instr(instr, block) {
  58       if (instr->type ==  nir_instr_type_deref) {
  59          nir_deref_instr *deref = nir_instr_as_deref(instr);
  60          if (deref->deref_type == nir_deref_type_var)
  61             register_var_use(deref->var, impl, var_func_table);
  62       }
  63    }
  64
  65    return true;
  66 }
  67
  68 bool
  69 nir_lower_global_vars_to_local(nir_shader *shader)
  70 {
  71    bool progress = false;
  72
  73    /* A hash table keyed on variable pointers that stores the unique
  74     * nir_function_impl that uses the given variable.  If a variable is
  75     * used in multiple functions, the data for the given key will be NULL.
  76     */
  77    struct hash_table *var_func_table = _mesa_pointer_hash_table_create(NULL);
  78
  79    nir_foreach_function(function, shader) {
  80       if (function->impl) {
  81          nir_foreach_block(block, function->impl)
  82             mark_global_var_uses_block(block, function->impl, var_func_table);
  83       }
  84    }
  85
  86    nir_foreach_variable_with_modes_safe(var, shader, nir_var_shader_temp) {
  87       struct hash_entry *entry = _mesa_hash_table_search(var_func_table, var);
  88       if (!entry)
  89          continue;
  90
  91       nir_function_impl *impl = entry->data;
  92
  93       if (impl != NULL) {
  94          exec_node_remove(&var->node);
  95          var->data.mode = nir_var_function_temp;
  96          exec_list_push_tail(&impl->locals, &var->node);
  97          nir_metadata_preserve(impl, nir_metadata_block_index |
  98                                      nir_metadata_dominance |
  99                                      nir_metadata_live_ssa_defs);
 100          progress = true;
 101       }
 102    }
 103
 104    _mesa_hash_table_destroy(var_func_table, NULL);
 105
 106    if (progress)
 107       nir_fixup_deref_modes(shader);
 108
 109    nir_foreach_function(function, shader) {
 110       if (function->impl)
 111          nir_metadata_preserve(function->impl, nir_metadata_all);
 112    }
 113
 114    return progress;
 115 }