src/mesa/drivers/dri/i965/brw_vec4_cse.cpp

   1 /*
   2  * Copyright © 2012, 2013, 2014 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_vec4.h"
  25 #include "brw_vec4_live_variables.h"
  26 #include "brw_cfg.h"
  27
  28 using namespace brw;
  29
  30 /** @file brw_vec4_cse.cpp
  31  *
  32  * Support for local common subexpression elimination.
  33  *
  34  * See Muchnick's Advanced Compiler Design and Implementation, section
  35  * 13.1 (p378).
  36  */
  37
  38 namespace {
  39 struct aeb_entry : public exec_node {
  40    /** The instruction that generates the expression value. */
  41    vec4_instruction *generator;
  42
  43    /** The temporary where the value is stored. */
  44    src_reg tmp;
  45 };
  46 }
  47
  48 static bool
  49 is_expression(const vec4_instruction *const inst)
  50 {
  51    switch (inst->opcode) {
  52    case BRW_OPCODE_MOV:
  53    case BRW_OPCODE_SEL:
  54    case BRW_OPCODE_NOT:
  55    case BRW_OPCODE_AND:
  56    case BRW_OPCODE_OR:
  57    case BRW_OPCODE_XOR:
  58    case BRW_OPCODE_SHR:
  59    case BRW_OPCODE_SHL:
  60    case BRW_OPCODE_ASR:
  61    case BRW_OPCODE_CMP:
  62    case BRW_OPCODE_CMPN:
  63    case BRW_OPCODE_ADD:
  64    case BRW_OPCODE_MUL:
  65    case SHADER_OPCODE_MULH:
  66    case BRW_OPCODE_FRC:
  67    case BRW_OPCODE_RNDU:
  68    case BRW_OPCODE_RNDD:
  69    case BRW_OPCODE_RNDE:
  70    case BRW_OPCODE_RNDZ:
  71    case BRW_OPCODE_LINE:
  72    case BRW_OPCODE_PLN:
  73    case BRW_OPCODE_MAD:
  74    case BRW_OPCODE_LRP:
  75    case VEC4_OPCODE_UNPACK_UNIFORM:
  76    case SHADER_OPCODE_FIND_LIVE_CHANNEL:
  77    case SHADER_OPCODE_BROADCAST:
  78    case TCS_OPCODE_SET_INPUT_URB_OFFSETS:
  79    case TCS_OPCODE_SET_OUTPUT_URB_OFFSETS:
  80       return true;
  81    case SHADER_OPCODE_RCP:
  82    case SHADER_OPCODE_RSQ:
  83    case SHADER_OPCODE_SQRT:
  84    case SHADER_OPCODE_EXP2:
  85    case SHADER_OPCODE_LOG2:
  86    case SHADER_OPCODE_POW:
  87    case SHADER_OPCODE_INT_QUOTIENT:
  88    case SHADER_OPCODE_INT_REMAINDER:
  89    case SHADER_OPCODE_SIN:
  90    case SHADER_OPCODE_COS:
  91       return inst->mlen == 0;
  92    default:
  93       return false;
  94    }
  95 }
  96
  97 static bool
  98 operands_match(const vec4_instruction *a, const vec4_instruction *b)
  99 {
 100    const src_reg *xs = a->src;
 101    const src_reg *ys = b->src;
 102
 103    if (a->opcode == BRW_OPCODE_MAD) {
 104       return xs[0].equals(ys[0]) &&
 105              ((xs[1].equals(ys[1]) && xs[2].equals(ys[2])) ||
 106               (xs[2].equals(ys[1]) && xs[1].equals(ys[2])));
 107    } else if (!a->is_commutative()) {
 108       return xs[0].equals(ys[0]) && xs[1].equals(ys[1]) && xs[2].equals(ys[2]);
 109    } else {
 110       return (xs[0].equals(ys[0]) && xs[1].equals(ys[1])) ||
 111              (xs[1].equals(ys[0]) && xs[0].equals(ys[1]));
 112    }
 113 }
 114
 115 static bool
 116 instructions_match(vec4_instruction *a, vec4_instruction *b)
 117 {
 118    return a->opcode == b->opcode &&
 119           a->saturate == b->saturate &&
 120           a->predicate == b->predicate &&
 121           a->predicate_inverse == b->predicate_inverse &&
 122           a->conditional_mod == b->conditional_mod &&
 123           a->flag_subreg == b->flag_subreg &&
 124           a->dst.type == b->dst.type &&
 125           a->offset == b->offset &&
 126           a->mlen == b->mlen &&
 127           a->base_mrf == b->base_mrf &&
 128           a->header_size == b->header_size &&
 129           a->shadow_compare == b->shadow_compare &&
 130           a->dst.writemask == b->dst.writemask &&
 131           a->force_writemask_all == b->force_writemask_all &&
 132           a->regs_written == b->regs_written &&
 133           operands_match(a, b);
 134 }
 135
 136 bool
 137 vec4_visitor::opt_cse_local(bblock_t *block)
 138 {
 139    bool progress = false;
 140    exec_list aeb;
 141
 142    void *cse_ctx = ralloc_context(NULL);
 143
 144    int ip = block->start_ip;
 145    foreach_inst_in_block (vec4_instruction, inst, block) {
 146       /* Skip some cases. */
 147       if (is_expression(inst) && !inst->predicate && inst->mlen == 0 &&
 148           ((inst->dst.file != ARF && inst->dst.file != FIXED_GRF) ||
 149            inst->dst.is_null()))
 150       {
 151          bool found = false;
 152
 153          foreach_in_list_use_after(aeb_entry, entry, &aeb) {
 154             /* Match current instruction's expression against those in AEB. */
 155             if (!(entry->generator->dst.is_null() && !inst->dst.is_null()) &&
 156                 instructions_match(inst, entry->generator)) {
 157                found = true;
 158                progress = true;
 159                break;
 160             }
 161          }
 162
 163          if (!found) {
 164             if (inst->opcode != BRW_OPCODE_MOV ||
 165                 (inst->opcode == BRW_OPCODE_MOV &&
 166                  inst->src[0].file == IMM &&
 167                  inst->src[0].type == BRW_REGISTER_TYPE_VF)) {
 168                /* Our first sighting of this expression.  Create an entry. */
 169                aeb_entry *entry = ralloc(cse_ctx, aeb_entry);
 170                entry->tmp = src_reg(); /* file will be BAD_FILE */
 171                entry->generator = inst;
 172                aeb.push_tail(entry);
 173             }
 174          } else {
 175             /* This is at least our second sighting of this expression.
 176              * If we don't have a temporary already, make one.
 177              */
 178             bool no_existing_temp = entry->tmp.file == BAD_FILE;
 179             if (no_existing_temp && !entry->generator->dst.is_null()) {
 180                entry->tmp = retype(src_reg(VGRF, alloc.allocate(
 181                                               entry->generator->regs_written),
 182                                            NULL), inst->dst.type);
 183
 184                for (unsigned i = 0; i < entry->generator->regs_written; ++i) {
 185                   vec4_instruction *copy = MOV(offset(entry->generator->dst, i),
 186                                                offset(entry->tmp, i));
 187                   copy->force_writemask_all =
 188                      entry->generator->force_writemask_all;
 189                   entry->generator->insert_after(block, copy);
 190                }
 191
 192                entry->generator->dst = dst_reg(entry->tmp);
 193             }
 194
 195             /* dest <- temp */
 196             if (!inst->dst.is_null()) {
 197                assert(inst->dst.type == entry->tmp.type);
 198
 199                for (unsigned i = 0; i < inst->regs_written; ++i) {
 200                   vec4_instruction *copy = MOV(offset(inst->dst, i),
 201                                                offset(entry->tmp, i));
 202                   copy->force_writemask_all = inst->force_writemask_all;
 203                   inst->insert_before(block, copy);
 204                }
 205             }
 206
 207             /* Set our iterator so that next time through the loop inst->next
 208              * will get the instruction in the basic block after the one we've
 209              * removed.
 210              */
 211             vec4_instruction *prev = (vec4_instruction *)inst->prev;
 212
 213             inst->remove(block);
 214             inst = prev;
 215          }
 216       }
 217
 218       foreach_in_list_safe(aeb_entry, entry, &aeb) {
 219          /* Kill all AEB entries that write a different value to or read from
 220           * the flag register if we just wrote it.
 221           */
 222          if (inst->writes_flag()) {
 223             if (entry->generator->reads_flag() ||
 224                 (entry->generator->writes_flag() &&
 225                  !instructions_match(inst, entry->generator))) {
 226                entry->remove();
 227                ralloc_free(entry);
 228                continue;
 229             }
 230          }
 231
 232          for (int i = 0; i < 3; i++) {
 233             src_reg *src = &entry->generator->src[i];
 234
 235             /* Kill all AEB entries that use the destination we just
 236              * overwrote.
 237              */
 238             if (inst->dst.file == entry->generator->src[i].file &&
 239                 inst->dst.nr == entry->generator->src[i].nr) {
 240                entry->remove();
 241                ralloc_free(entry);
 242                break;
 243             }
 244
 245             /* Kill any AEB entries using registers that don't get reused any
 246              * more -- a sure sign they'll fail operands_match().
 247              */
 248             if (src->file == VGRF) {
 249                if (var_range_end(var_from_reg(alloc, *src), 4) < ip) {
 250                   entry->remove();
 251                   ralloc_free(entry);
 252                   break;
 253                }
 254             }
 255          }
 256       }
 257
 258       ip++;
 259    }
 260
 261    ralloc_free(cse_ctx);
 262
 263    return progress;
 264 }
 265
 266 bool
 267 vec4_visitor::opt_cse()
 268 {
 269    bool progress = false;
 270
 271    calculate_live_intervals();
 272
 273    foreach_block (block, cfg) {
 274       progress = opt_cse_local(block) || progress;
 275    }
 276
 277    if (progress)
 278       invalidate_live_intervals();
 279
 280    return progress;
 281 }