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      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 (at) 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_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    struct hash_entry *entry;
     87    hash_table_foreach(var_func_table, entry) {
     88       nir_variable *var = (void *)entry->key;
     89       nir_function_impl *impl = entry->data;
     90 
     91       assert(var->data.mode == nir_var_global);
     92 
     93       if (impl != NULL) {
     94          exec_node_remove(&var->node);
     95          var->data.mode = nir_var_local;
     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    return progress;
    107 }
    108