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

   1 /*
   2  * Copyright © 2012 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_cfg.h"
  26
  27 /** @file brw_fs_cse.cpp
  28  *
  29  * Support for local common subexpression elimination.
  30  *
  31  * See Muchnik's Advanced Compiler Design and Implementation, section
  32  * 13.1 (p378).
  33  */
  34
  35 namespace {
  36 struct aeb_entry : public exec_node {
  37    /** The instruction that generates the expression value. */
  38    fs_inst *generator;
  39
  40    /** The temporary where the value is stored. */
  41    fs_reg tmp;
  42 };
  43 }
  44
  45 static bool
  46 is_expression(const fs_inst *const inst)
  47 {
  48    switch (inst->opcode) {
  49    case BRW_OPCODE_SEL:
  50    case BRW_OPCODE_NOT:
  51    case BRW_OPCODE_AND:
  52    case BRW_OPCODE_OR:
  53    case BRW_OPCODE_XOR:
  54    case BRW_OPCODE_SHR:
  55    case BRW_OPCODE_SHL:
  56    case BRW_OPCODE_RSR:
  57    case BRW_OPCODE_RSL:
  58    case BRW_OPCODE_ASR:
  59    case BRW_OPCODE_ADD:
  60    case BRW_OPCODE_MUL:
  61    case BRW_OPCODE_FRC:
  62    case BRW_OPCODE_RNDU:
  63    case BRW_OPCODE_RNDD:
  64    case BRW_OPCODE_RNDE:
  65    case BRW_OPCODE_RNDZ:
  66    case BRW_OPCODE_LINE:
  67    case BRW_OPCODE_PLN:
  68    case BRW_OPCODE_MAD:
  69    case FS_OPCODE_CINTERP:
  70    case FS_OPCODE_LINTERP:
  71       return true;
  72    default:
  73       return false;
  74    }
  75 }
  76
  77 static bool
  78 operands_match(fs_reg *xs, fs_reg *ys)
  79 {
  80    return xs[0].equals(ys[0]) && xs[1].equals(ys[1]) && xs[2].equals(ys[2]);
  81 }
  82
  83 bool
  84 fs_visitor::opt_cse_local(fs_bblock *block, exec_list *aeb)
  85 {
  86    bool progress = false;
  87
  88    void *mem_ctx = ralloc_context(this->mem_ctx);
  89
  90    for (fs_inst *inst = block->start;
  91         inst != block->end->next;
  92         inst = (fs_inst *) inst->next) {
  93
  94       /* Skip some cases. */
  95       if (is_expression(inst) && !inst->predicated && inst->mlen == 0 &&
  96           !inst->force_uncompressed && !inst->force_sechalf &&
  97           !inst->conditional_mod)
  98       {
  99          bool found = false;
 100
 101          aeb_entry *entry;
 102          foreach_list(entry_node, aeb) {
 103             entry = (aeb_entry *) entry_node;
 104
 105             /* Match current instruction's expression against those in AEB. */
 106             if (inst->opcode == entry->generator->opcode &&
 107                 inst->saturate == entry->generator->saturate &&
 108                 operands_match(entry->generator->src, inst->src)) {
 109
 110                found = true;
 111                progress = true;
 112                break;
 113             }
 114          }
 115
 116          if (!found) {
 117             /* Our first sighting of this expression.  Create an entry. */
 118             aeb_entry *entry = ralloc(mem_ctx, aeb_entry);
 119             entry->tmp = reg_undef;
 120             entry->generator = inst;
 121             aeb->push_tail(entry);
 122          } else {
 123             /* This is at least our second sighting of this expression.
 124              * If we don't have a temporary already, make one.
 125              */
 126             bool no_existing_temp = entry->tmp.file == BAD_FILE;
 127             if (no_existing_temp) {
 128                entry->tmp = fs_reg(this, glsl_type::float_type);
 129                entry->tmp.type = inst->dst.type;
 130
 131                fs_inst *copy = new(ralloc_parent(inst))
 132                   fs_inst(BRW_OPCODE_MOV, entry->generator->dst, entry->tmp);
 133                entry->generator->insert_after(copy);
 134                entry->generator->dst = entry->tmp;
 135             }
 136
 137             /* dest <- temp */
 138             fs_inst *copy = new(ralloc_parent(inst))
 139                fs_inst(BRW_OPCODE_MOV, inst->dst, entry->tmp);
 140             inst->replace_with(copy);
 141
 142             /* Appending an instruction may have changed our bblock end. */
 143             if (inst == block->end) {
 144                block->end = copy;
 145             }
 146
 147             /* Continue iteration with copy->next */
 148             inst = copy;
 149          }
 150       }
 151
 152       /* Kill all AEB entries that use the destination. */
 153       foreach_list_safe(entry_node, aeb) {
 154          aeb_entry *entry = (aeb_entry *)entry_node;
 155
 156          for (int i = 0; i < 3; i++) {
 157             if (inst->overwrites_reg(entry->generator->src[i])) {
 158                entry->remove();
 159                ralloc_free(entry);
 160                break;
 161             }
 162          }
 163       }
 164    }
 165
 166    ralloc_free(mem_ctx);
 167
 168    if (progress)
 169       this->live_intervals_valid = false;
 170
 171    return progress;
 172 }
 173
 174 bool
 175 fs_visitor::opt_cse()
 176 {
 177    bool progress = false;
 178
 179    fs_cfg cfg(this);
 180
 181    for (int b = 0; b < cfg.num_blocks; b++) {
 182       fs_bblock *block = cfg.blocks[b];
 183       exec_list aeb;
 184
 185       progress = opt_cse_local(block, &aeb) || progress;
 186    }
 187
 188    return progress;
 189 }