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         bool debug = false;
  42
  43         list_for_each_entry(struct qinst, inst, &c->instructions, link) {
  44                 int nsrc = qir_get_op_nsrc(inst->op);
  45                 for (int i = 0; i < nsrc; i++) {
  46                         if (inst->src[i].file != QFILE_TEMP)
  47                                 continue;
  48
  49                         struct qinst *mov = c->defs[inst->src[i].index];
  50                         if (!mov ||
  51                             (mov->op != QOP_MOV &&
  52                              mov->op != QOP_FMOV &&
  53                              mov->op != QOP_MMOV)) {
  54                                 continue;
  55                         }
  56
  57                         if (mov->src[0].file != QFILE_TEMP &&
  58                             mov->src[0].file != QFILE_UNIF) {
  59                                 continue;
  60                         }
  61
  62                         if (mov->dst.pack)
  63                                 continue;
  64
  65                         uint8_t unpack;
  66                         if (mov->src[0].pack) {
  67                                 /* Make sure that the meaning of the unpack
  68                                  * would be the same between the two
  69                                  * instructions.
  70                                  */
  71                                 if (qir_is_float_input(inst) !=
  72                                     qir_is_float_input(mov)) {
  73                                         continue;
  74                                 }
  75
  76                                 /* There's only one unpack field, so make sure
  77                                  * this instruction doesn't already use it.
  78                                  */
  79                                 bool already_has_unpack = false;
  80                                 for (int j = 0; j < nsrc; j++) {
  81                                         if (inst->src[j].pack)
  82                                                 already_has_unpack = true;
  83                                 }
  84                                 if (already_has_unpack)
  85                                         continue;
  86
  87                                 /* A destination pack requires the PM bit to
  88                                  * be set to a specific value already, which
  89                                  * may be different from ours.
  90                                  */
  91                                 if (inst->dst.pack)
  92                                         continue;
  93
  94                                 unpack = mov->src[0].pack;
  95                         } else {
  96                                 unpack = inst->src[i].pack;
  97                         }
  98
  99                         if (debug) {
 100                                 fprintf(stderr, "Copy propagate: ");
 101                                 qir_dump_inst(c, inst);
 102                                 fprintf(stderr, "\n");
 103                         }
 104
 105                         inst->src[i] = mov->src[0];
 106                         inst->src[i].pack = unpack;
 107
 108                         if (debug) {
 109                                 fprintf(stderr, "to: ");
 110                                 qir_dump_inst(c, inst);
 111                                 fprintf(stderr, "\n");
 112                         }
 113
 114                         progress = true;
 115                 }
 116         }
 117         return progress;
 118 }