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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  *    Connor Abbott (cwabbott0 (at) gmail.com)
     26  *
     27  */
     28 
     29 #include "nir_instr_set.h"
     30 
     31 /*
     32  * Implements common subexpression elimination
     33  */
     34 
     35 /*
     36  * Visits and CSE's the given block and all its descendants in the dominance
     37  * tree recursively. Note that the instr_set is guaranteed to only ever
     38  * contain instructions that dominate the current block.
     39  */
     40 
     41 static bool
     42 cse_block(nir_block *block, struct set *instr_set)
     43 {
     44    bool progress = false;
     45 
     46    nir_foreach_instr_safe(instr, block) {
     47       if (nir_instr_set_add_or_rewrite(instr_set, instr)) {
     48          progress = true;
     49          nir_instr_remove(instr);
     50       }
     51    }
     52 
     53    for (unsigned i = 0; i < block->num_dom_children; i++) {
     54       nir_block *child = block->dom_children[i];
     55       progress |= cse_block(child, instr_set);
     56    }
     57 
     58    nir_foreach_instr(instr, block)
     59      nir_instr_set_remove(instr_set, instr);
     60 
     61    return progress;
     62 }
     63 
     64 static bool
     65 nir_opt_cse_impl(nir_function_impl *impl)
     66 {
     67    struct set *instr_set = nir_instr_set_create(NULL);
     68 
     69    nir_metadata_require(impl, nir_metadata_dominance);
     70 
     71    bool progress = cse_block(nir_start_block(impl), instr_set);
     72 
     73    if (progress)
     74       nir_metadata_preserve(impl, nir_metadata_block_index |
     75                                   nir_metadata_dominance);
     76 
     77    nir_instr_set_destroy(instr_set);
     78    return progress;
     79 }
     80 
     81 bool
     82 nir_opt_cse(nir_shader *shader)
     83 {
     84    bool progress = false;
     85 
     86    nir_foreach_function(function, shader) {
     87       if (function->impl)
     88          progress |= nir_opt_cse_impl(function->impl);
     89    }
     90 
     91    return progress;
     92 }
     93 
     94