src/gallium/drivers/vc4/vc4_opt_dead_code.c

   1 /*
   2  * Copyright © 2014 Broadcom
   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
  24 /**
  25  * @file vc4_opt_dead_code.c
  26  *
  27  * This is a simmple dead code eliminator for QIR with no control flow.
  28  *
  29  * It walks from the bottom of the instruction list, removing instructions
  30  * with a destination that is never used, and marking the sources of non-dead
  31  * instructions as used.
  32  */
  33
  34 #include "vc4_qir.h"
  35
  36 bool
  37 qir_opt_dead_code(struct qcompile *c)
  38 {
  39         bool progress = false;
  40         bool debug = false;
  41         bool *used = calloc(c->num_temps, sizeof(bool));
  42
  43         struct simple_node *node, *t;
  44         for (node = c->instructions.prev, t = node->prev;
  45              &c->instructions != node;
  46              node = t, t = t->prev) {
  47                 struct qinst *inst = (struct qinst *)node;
  48
  49                 if (inst->dst.file == QFILE_TEMP &&
  50                     !used[inst->dst.index] &&
  51                     !qir_has_side_effects(inst)) {
  52                         if (debug) {
  53                                 fprintf(stderr, "Removing: ");
  54                                 qir_dump_inst(inst);
  55                                 fprintf(stderr, "\n");
  56                         }
  57                         remove_from_list(&inst->link);
  58                         free(inst);
  59                         progress = true;
  60                         continue;
  61                 }
  62
  63                 for (int i = 0; i < qir_get_op_nsrc(inst->op); i++) {
  64                         if (inst->src[i].file == QFILE_TEMP)
  65                                 used[inst->src[i].index] = true;
  66                 }
  67         }
  68
  69         free(used);
  70
  71         return progress;
  72 }