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 static bool debug;
  37
  38 static void
  39 dce(struct vc4_compile *c, struct qinst *inst)
  40 {
  41         if (debug) {
  42                 fprintf(stderr, "Removing: ");
  43                 qir_dump_inst(c, inst);
  44                 fprintf(stderr, "\n");
  45         }
  46         qir_remove_instruction(inst);
  47 }
  48
  49 bool
  50 qir_opt_dead_code(struct vc4_compile *c)
  51 {
  52         bool progress = false;
  53         bool *used = calloc(c->num_temps, sizeof(bool));
  54         bool sf_used = false;
  55         /* Whether we're eliminating texture setup currently. */
  56         bool dce_tex = false;
  57
  58         struct simple_node *node, *t;
  59         for (node = c->instructions.prev, t = node->prev;
  60              &c->instructions != node;
  61              node = t, t = t->prev) {
  62                 struct qinst *inst = (struct qinst *)node;
  63
  64                 if (inst->dst.file == QFILE_TEMP &&
  65                     !used[inst->dst.index] &&
  66                     (!qir_has_side_effects(c, inst) ||
  67                      inst->op == QOP_TEX_RESULT)) {
  68                         if (inst->op == QOP_TEX_RESULT) {
  69                                 dce_tex = true;
  70                                 c->num_texture_samples--;
  71                         }
  72
  73                         dce(c, inst);
  74                         progress = true;
  75                         continue;
  76                 }
  77
  78                 if (qir_depends_on_flags(inst))
  79                         sf_used = true;
  80                 if (inst->op == QOP_SF) {
  81                         if (!sf_used) {
  82                                 dce(c, inst);
  83                                 progress = true;
  84                                 continue;
  85                         }
  86                         sf_used = false;
  87                 }
  88
  89                 if (inst->op == QOP_TEX_RESULT)
  90                         dce_tex = false;
  91
  92                 if (dce_tex && (inst->op == QOP_TEX_S ||
  93                                 inst->op == QOP_TEX_T ||
  94                                 inst->op == QOP_TEX_R ||
  95                                 inst->op == QOP_TEX_B ||
  96                                 inst->op == QOP_TEX_DIRECT)) {
  97                         dce(c, inst);
  98                         progress = true;
  99                         continue;
 100                 }
 101
 102                 for (int i = 0; i < qir_get_op_nsrc(inst->op); i++) {
 103                         if (inst->src[i].file == QFILE_TEMP)
 104                                 used[inst->src[i].index] = true;
 105                 }
 106         }
 107
 108         free(used);
 109
 110         return progress;
 111 }