src/gallium/drivers/vc4/vc4_opt_copy_propagation.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_copy_propagation.c
  26  *
  27  * This implements simple copy propagation for QIR without control flow.
  28  *
  29  * For each temp, it keeps a qreg of which source it was MOVed from, if it
  30  * was.  If we see that used later, we can just reuse the source value, since
  31  * we know we don't have control flow, and we have SSA for our values so
  32  * there's no killing to worry about.
  33  */
  34
  35 #include "vc4_qir.h"
  36
  37 bool
  38 qir_opt_copy_propagation(struct vc4_compile *c)
  39 {
  40         bool progress = false;
  41         struct simple_node *node;
  42         bool debug = false;
  43         struct qreg *movs = calloc(c->num_temps, sizeof(struct qreg));
  44         struct qinst **defs = calloc(c->num_temps, sizeof(struct qreg));
  45
  46         foreach(node, &c->instructions) {
  47                 struct qinst *inst = (struct qinst *)node;
  48
  49                 if (inst->dst.file == QFILE_TEMP)
  50                         defs[inst->dst.index] = inst;
  51
  52                 /* A single instruction can only read one uniform value.  (It
  53                  * could maybe read the same uniform value in two operands,
  54                  * but that doesn't seem important to do).
  55                  */
  56                 bool reads_a_uniform = false;
  57                 for (int i = 0; i < qir_get_op_nsrc(inst->op); i++) {
  58                         if (inst->src[i].file == QFILE_UNIF)
  59                                 reads_a_uniform = true;
  60                 }
  61
  62                 for (int i = 0; i < qir_get_op_nsrc(inst->op); i++) {
  63                         int index = inst->src[i].index;
  64                         if (inst->src[i].file == QFILE_TEMP &&
  65                             (movs[index].file == QFILE_TEMP ||
  66                              (movs[index].file == QFILE_UNIF &&
  67                               !reads_a_uniform))) {
  68                                 if (debug) {
  69                                         fprintf(stderr, "Copy propagate: ");
  70                                         qir_dump_inst(c, inst);
  71                                         fprintf(stderr, "\n");
  72                                 }
  73
  74                                 inst->src[i] = movs[index];
  75                                 if (movs[index].file == QFILE_UNIF)
  76                                         reads_a_uniform = true;
  77
  78                                 if (debug) {
  79                                         fprintf(stderr, "to: ");
  80                                         qir_dump_inst(c, inst);
  81                                         fprintf(stderr, "\n");
  82                                 }
  83
  84                                 progress = true;
  85                         }
  86                 }
  87
  88                 if (inst->op == QOP_MOV &&
  89                     inst->dst.file == QFILE_TEMP &&
  90                     (inst->src[0].file != QFILE_TEMP ||
  91                      (defs[inst->src[0].index]->op != QOP_TEX_RESULT &&
  92                       defs[inst->src[0].index]->op != QOP_TLB_COLOR_READ))) {
  93                         movs[inst->dst.index] = inst->src[0];
  94                 }
  95         }
  96
  97         free(movs);
  98         free(defs);
  99         return progress;
 100 }