src/glsl/nir/nir_opt_dce.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  *    Connor Abbott (cwabbott0@gmail.com)
  25  *
  26  */
  27
  28 #include "nir.h"
  29
  30 /* SSA-based mark-and-sweep dead code elimination */
  31
  32 typedef struct {
  33    struct exec_node node;
  34    nir_instr *instr;
  35 } worklist_elem;
  36
  37 static void
  38 worklist_push(struct exec_list *worklist, nir_instr *instr)
  39 {
  40    worklist_elem *elem = ralloc(worklist, worklist_elem);
  41    elem->instr = instr;
  42    instr->live = true;
  43    exec_list_push_tail(worklist, &elem->node);
  44 }
  45
  46 static nir_instr *
  47 worklist_pop(struct exec_list *worklist)
  48 {
  49    struct exec_node *node = exec_list_pop_head(worklist);
  50    worklist_elem *elem = exec_node_data(worklist_elem, node, node);
  51    return elem->instr;
  52 }
  53
  54 static bool
  55 mark_live_cb(nir_src *src, void *_state)
  56 {
  57    struct exec_list *worklist = (struct exec_list *) _state;
  58
  59    if (src->is_ssa && !src->ssa->parent_instr->live) {
  60       worklist_push(worklist, src->ssa->parent_instr);
  61    }
  62
  63    return true;
  64 }
  65
  66 static void
  67 init_instr(nir_instr *instr, struct exec_list *worklist)
  68 {
  69    nir_alu_instr *alu_instr;
  70    nir_intrinsic_instr *intrin_instr;
  71    nir_tex_instr *tex_instr;
  72
  73    instr->live = false;
  74
  75    switch (instr->type) {
  76    case nir_instr_type_call:
  77    case nir_instr_type_jump:
  78       worklist_push(worklist, instr);
  79       break;
  80
  81    case nir_instr_type_alu:
  82       alu_instr = nir_instr_as_alu(instr);
  83       if (!alu_instr->dest.dest.is_ssa)
  84          worklist_push(worklist, instr);
  85       break;
  86
  87    case nir_instr_type_intrinsic:
  88       intrin_instr = nir_instr_as_intrinsic(instr);
  89       if (nir_intrinsic_infos[intrin_instr->intrinsic].flags &
  90           NIR_INTRINSIC_CAN_ELIMINATE) {
  91          if (nir_intrinsic_infos[intrin_instr->intrinsic].has_dest &&
  92              !intrin_instr->dest.is_ssa) {
  93             worklist_push(worklist, instr);
  94          }
  95       } else {
  96          worklist_push(worklist, instr);
  97       }
  98       break;
  99
 100    case nir_instr_type_tex:
 101       tex_instr = nir_instr_as_tex(instr);
 102       if (!tex_instr->dest.is_ssa)
 103          worklist_push(worklist, instr);
 104       break;
 105
 106    default:
 107       break;
 108    }
 109 }
 110
 111 static bool
 112 init_block_cb(nir_block *block, void *_state)
 113 {
 114    struct exec_list *worklist = (struct exec_list *) _state;
 115
 116    nir_foreach_instr(block, instr)
 117       init_instr(instr, worklist);
 118
 119    nir_if *following_if = nir_block_following_if(block);
 120    if (following_if) {
 121       if (following_if->condition.is_ssa &&
 122           !following_if->condition.ssa->parent_instr->live)
 123          worklist_push(worklist, following_if->condition.ssa->parent_instr);
 124    }
 125
 126    return true;
 127 }
 128
 129 static bool
 130 delete_block_cb(nir_block *block, void *_state)
 131 {
 132    bool *progress = (bool *) _state;
 133
 134    nir_foreach_instr_safe(block, instr) {
 135       if (!instr->live) {
 136          nir_instr_remove(instr);
 137          *progress = true;
 138       }
 139    }
 140
 141    return true;
 142 }
 143
 144 bool
 145 nir_opt_dce_impl(nir_function_impl *impl)
 146 {
 147    struct exec_list *worklist = ralloc(NULL, struct exec_list);
 148    exec_list_make_empty(worklist);
 149
 150    nir_foreach_block(impl, init_block_cb, worklist);
 151
 152    while (!exec_list_is_empty(worklist)) {
 153       nir_instr *instr = worklist_pop(worklist);
 154       nir_foreach_src(instr, mark_live_cb, worklist);
 155    }
 156
 157    ralloc_free(worklist);
 158
 159    bool progress = false;
 160    nir_foreach_block(impl, delete_block_cb, &progress);
 161
 162    if (progress)
 163       nir_metadata_preserve(impl, nir_metadata_block_index |
 164                                   nir_metadata_dominance);
 165
 166    return progress;
 167 }
 168
 169 bool
 170 nir_opt_dce(nir_shader *shader)
 171 {
 172    bool progress = false;
 173    nir_foreach_overload(shader, overload) {
 174       if (overload->impl && nir_opt_dce_impl(overload->impl))
 175          progress = true;
 176    }
 177
 178    return progress;
 179 }