src/compiler/nir/nir_opt_cse.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  *    Connor Abbott (cwabbott0@gmail.com)
  26  *
  27  */
  28
  29 #include "nir_instr_set.h"
  30
  31 /*
  32  * Implements common subexpression elimination
  33  */
  34
  35 /*
  36  * Visits and CSEs 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 *dominance_set)
  43 {
  44    bool progress = false;
  45    struct set *instr_set = _mesa_set_clone(dominance_set, NULL);
  46
  47    nir_foreach_instr_safe(instr, block) {
  48       if (nir_instr_set_add_or_rewrite(instr_set, instr)) {
  49          progress = true;
  50          nir_instr_remove(instr);
  51       }
  52    }
  53
  54    for (unsigned i = 0; i < block->num_dom_children; i++) {
  55       nir_block *child = block->dom_children[i];
  56       progress |= cse_block(child, instr_set);
  57    }
  58
  59    _mesa_set_destroy(instr_set, NULL);
  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    } else {
  77       nir_metadata_preserve(impl, nir_metadata_all);
  78    }
  79
  80    nir_instr_set_destroy(instr_set);
  81    return progress;
  82 }
  83
  84 bool
  85 nir_opt_cse(nir_shader *shader)
  86 {
  87    bool progress = false;
  88
  89    nir_foreach_function(function, shader) {
  90       if (function->impl)
  91          progress |= nir_opt_cse_impl(function->impl);
  92    }
  93
  94    return progress;
  95 }
  96