src/mesa/drivers/dri/i965/brw_fs_saturate_propagation.cpp

   1 /*
   2  * Copyright © 2013 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
  24 #include "brw_fs.h"
  25 #include "brw_fs_live_variables.h"
  26 #include "brw_cfg.h"
  27
  28 /** @file brw_fs_saturate_propagation.cpp
  29  *
  30  * Implements a pass that propagates the SAT modifier from a MOV.SAT into the
  31  * instruction that produced the source of the MOV.SAT, thereby allowing the
  32  * MOV's src and dst to be coalesced and the MOV removed.
  33  *
  34  * For instance,
  35  *
  36  *    ADD     tmp, src0, src1
  37  *    MOV.SAT dst, tmp
  38  *
  39  * would be transformed into
  40  *
  41  *    ADD.SAT tmp, src0, src1
  42  *    MOV     dst, tmp
  43  */
  44
  45 static bool
  46 opt_saturate_propagation_local(fs_visitor *v, bblock_t *block)
  47 {
  48    bool progress = false;
  49    int ip = block->end_ip + 1;
  50
  51    foreach_inst_in_block_reverse(fs_inst, inst, block) {
  52       ip--;
  53
  54       if (inst->opcode != BRW_OPCODE_MOV ||
  55           !inst->saturate ||
  56           inst->dst.file != VGRF ||
  57           inst->dst.type != inst->src[0].type ||
  58           inst->src[0].file != VGRF ||
  59           inst->src[0].abs ||
  60           inst->src[0].negate)
  61          continue;
  62
  63       int src_var = v->live_intervals->var_from_reg(inst->src[0]);
  64       int src_end_ip = v->live_intervals->end[src_var];
  65
  66       bool interfered = false;
  67       foreach_inst_in_block_reverse_starting_from(fs_inst, scan_inst, inst) {
  68          if (scan_inst->overwrites_reg(inst->src[0])) {
  69             if (scan_inst->is_partial_write() ||
  70                 (scan_inst->dst.type != inst->dst.type &&
  71                  !scan_inst->can_change_types()))
  72                break;
  73
  74             if (scan_inst->saturate) {
  75                inst->saturate = false;
  76                progress = true;
  77             } else if (src_end_ip <= ip || inst->dst.equals(inst->src[0])) {
  78                if (scan_inst->can_do_saturate()) {
  79                   if (scan_inst->dst.type != inst->dst.type) {
  80                      scan_inst->dst.type = inst->dst.type;
  81                      for (int i = 0; i < scan_inst->sources; i++) {
  82                         scan_inst->src[i].type = inst->dst.type;
  83                      }
  84                   }
  85                   scan_inst->saturate = true;
  86                   inst->saturate = false;
  87                   progress = true;
  88                }
  89             }
  90             break;
  91          }
  92          for (int i = 0; i < scan_inst->sources; i++) {
  93             if (scan_inst->src[i].file == VGRF &&
  94                 scan_inst->src[i].nr == inst->src[0].nr &&
  95                 scan_inst->src[i].reg_offset == inst->src[0].reg_offset) {
  96                if (scan_inst->opcode != BRW_OPCODE_MOV ||
  97                    !scan_inst->saturate ||
  98                    scan_inst->src[0].abs ||
  99                    scan_inst->src[0].negate) {
 100                   interfered = true;
 101                   break;
 102                }
 103             }
 104          }
 105
 106          if (interfered)
 107             break;
 108       }
 109    }
 110
 111    return progress;
 112 }
 113
 114 bool
 115 fs_visitor::opt_saturate_propagation()
 116 {
 117    bool progress = false;
 118
 119    calculate_live_intervals();
 120
 121    foreach_block (block, cfg) {
 122       progress = opt_saturate_propagation_local(this, block) || progress;
 123    }
 124
 125    /* Live intervals are still valid. */
 126
 127    return progress;
 128 }