src/intel/compiler/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                                unsigned dispatch_width)
  48 {
  49    bool progress = false;
  50    int ip = block->end_ip + 1;
  51
  52    foreach_inst_in_block_reverse(fs_inst, inst, block) {
  53       ip--;
  54
  55       if (inst->opcode != BRW_OPCODE_MOV ||
  56           !inst->saturate ||
  57           inst->dst.file != VGRF ||
  58           inst->dst.type != inst->src[0].type ||
  59           inst->src[0].file != VGRF ||
  60           inst->src[0].abs)
  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 (regions_overlap(scan_inst->dst, scan_inst->size_written,
  69                              inst->src[0], inst->size_read(0))) {
  70             if (scan_inst->is_partial_var_write(dispatch_width) ||
  71                 (scan_inst->dst.type != inst->dst.type &&
  72                  !scan_inst->can_change_types()))
  73                break;
  74
  75             if (scan_inst->saturate) {
  76                inst->saturate = false;
  77                progress = true;
  78             } else if (src_end_ip == ip || inst->dst.equals(inst->src[0])) {
  79                if (scan_inst->can_do_saturate()) {
  80                   if (scan_inst->dst.type != inst->dst.type) {
  81                      scan_inst->dst.type = inst->dst.type;
  82                      for (int i = 0; i < scan_inst->sources; i++) {
  83                         scan_inst->src[i].type = inst->dst.type;
  84                      }
  85                   }
  86
  87                   if (inst->src[0].negate) {
  88                      if (scan_inst->opcode == BRW_OPCODE_MUL) {
  89                         scan_inst->src[0].negate = !scan_inst->src[0].negate;
  90                         inst->src[0].negate = false;
  91                      } else if (scan_inst->opcode == BRW_OPCODE_MAD) {
  92                         for (int i = 0; i < 2; i++) {
  93                            if (scan_inst->src[i].file == IMM) {
  94                               brw_negate_immediate(scan_inst->src[i].type,
  95                                                    &scan_inst->src[i].as_brw_reg());
  96                            } else {
  97                               scan_inst->src[i].negate = !scan_inst->src[i].negate;
  98                            }
  99                         }
 100                         inst->src[0].negate = false;
 101                      } else if (scan_inst->opcode == BRW_OPCODE_ADD) {
 102                         if (scan_inst->src[1].file == IMM) {
 103                            if (!brw_negate_immediate(scan_inst->src[1].type,
 104                                                      &scan_inst->src[1].as_brw_reg())) {
 105                               break;
 106                            }
 107                         } else {
 108                            scan_inst->src[1].negate = !scan_inst->src[1].negate;
 109                         }
 110                         scan_inst->src[0].negate = !scan_inst->src[0].negate;
 111                         inst->src[0].negate = false;
 112                      } else {
 113                         break;
 114                      }
 115                   }
 116
 117                   scan_inst->saturate = true;
 118                   inst->saturate = false;
 119                   progress = true;
 120                }
 121             }
 122             break;
 123          }
 124          for (int i = 0; i < scan_inst->sources; i++) {
 125             if (scan_inst->src[i].file == VGRF &&
 126                 scan_inst->src[i].nr == inst->src[0].nr &&
 127                 scan_inst->src[i].offset / REG_SIZE ==
 128                  inst->src[0].offset / REG_SIZE) {
 129                if (scan_inst->opcode != BRW_OPCODE_MOV ||
 130                    !scan_inst->saturate ||
 131                    scan_inst->src[0].abs ||
 132                    scan_inst->src[0].negate ||
 133                    scan_inst->src[0].abs != inst->src[0].abs ||
 134                    scan_inst->src[0].negate != inst->src[0].negate) {
 135                   interfered = true;
 136                   break;
 137                }
 138             }
 139          }
 140
 141          if (interfered)
 142             break;
 143       }
 144    }
 145
 146    return progress;
 147 }
 148
 149 bool
 150 fs_visitor::opt_saturate_propagation()
 151 {
 152    bool progress = false;
 153
 154    calculate_live_intervals();
 155
 156    foreach_block (block, cfg) {
 157       progress = opt_saturate_propagation_local(this, block, dispatch_width) || progress;
 158    }
 159
 160    /* Live intervals are still valid. */
 161
 162    return progress;
 163 }