tcg/optimize.c

   1 /*
   2  * Optimizations for Tiny Code Generator for QEMU
   3  *
   4  * Copyright (c) 2010 Samsung Electronics.
   5  * Contributed by Kirill Batuzov <batuzovk@ispras.ru>
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to deal
   9  * in the Software without restriction, including without limitation the rights
  10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11  * copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  23  * THE SOFTWARE.
  24  */
  25
  26 #include "config.h"
  27
  28 #include <stdlib.h>
  29 #include <stdio.h>
  30
  31 #include "qemu-common.h"
  32 #include "tcg-op.h"
  33
  34 #define CASE_OP_32_64(x)                        \
  35         glue(glue(case INDEX_op_, x), _i32):    \
  36         glue(glue(case INDEX_op_, x), _i64)
  37
  38 typedef enum {
  39     TCG_TEMP_UNDEF = 0,
  40     TCG_TEMP_CONST,
  41     TCG_TEMP_COPY,
  42     TCG_TEMP_HAS_COPY,
  43     TCG_TEMP_ANY
  44 } tcg_temp_state;
  45
  46 struct tcg_temp_info {
  47     tcg_temp_state state;
  48     uint16_t prev_copy;
  49     uint16_t next_copy;
  50     tcg_target_ulong val;
  51 };
  52
  53 static struct tcg_temp_info temps[TCG_MAX_TEMPS];
  54
  55 /* Reset TEMP's state to TCG_TEMP_ANY.  If TEMP was a representative of some
  56    class of equivalent temp's, a new representative should be chosen in this
  57    class. */
  58 static void reset_temp(TCGArg temp, int nb_temps, int nb_globals)
  59 {
  60     int i;
  61     TCGArg new_base = (TCGArg)-1;
  62     if (temps[temp].state == TCG_TEMP_HAS_COPY) {
  63         for (i = temps[temp].next_copy; i != temp; i = temps[i].next_copy) {
  64             if (i >= nb_globals) {
  65                 temps[i].state = TCG_TEMP_HAS_COPY;
  66                 new_base = i;
  67                 break;
  68             }
  69         }
  70         for (i = temps[temp].next_copy; i != temp; i = temps[i].next_copy) {
  71             if (new_base == (TCGArg)-1) {
  72                 temps[i].state = TCG_TEMP_ANY;
  73             } else {
  74                 temps[i].val = new_base;
  75             }
  76         }
  77         temps[temps[temp].next_copy].prev_copy = temps[temp].prev_copy;
  78         temps[temps[temp].prev_copy].next_copy = temps[temp].next_copy;
  79     } else if (temps[temp].state == TCG_TEMP_COPY) {
  80         temps[temps[temp].next_copy].prev_copy = temps[temp].prev_copy;
  81         temps[temps[temp].prev_copy].next_copy = temps[temp].next_copy;
  82         new_base = temps[temp].val;
  83     }
  84     temps[temp].state = TCG_TEMP_ANY;
  85     if (new_base != (TCGArg)-1 && temps[new_base].next_copy == new_base) {
  86         temps[new_base].state = TCG_TEMP_ANY;
  87     }
  88 }
  89
  90 static int op_bits(TCGOpcode op)
  91 {
  92     const TCGOpDef *def = &tcg_op_defs[op];
  93     return def->flags & TCG_OPF_64BIT ? 64 : 32;
  94 }
  95
  96 static TCGOpcode op_to_movi(TCGOpcode op)
  97 {
  98     switch (op_bits(op)) {
  99     case 32:
 100         return INDEX_op_movi_i32;
 101     case 64:
 102         return INDEX_op_movi_i64;
 103     default:
 104         fprintf(stderr, "op_to_movi: unexpected return value of "
 105                 "function op_bits.\n");
 106         tcg_abort();
 107     }
 108 }
 109
 110 static void tcg_opt_gen_mov(TCGContext *s, TCGArg *gen_args, TCGArg dst,
 111                             TCGArg src, int nb_temps, int nb_globals)
 112 {
 113         reset_temp(dst, nb_temps, nb_globals);
 114         assert(temps[src].state != TCG_TEMP_COPY);
 115         /* Don't try to copy if one of temps is a global or either one
 116            is local and another is register */
 117         if (src >= nb_globals && dst >= nb_globals &&
 118             tcg_arg_is_local(s, src) == tcg_arg_is_local(s, dst)) {
 119             assert(temps[src].state != TCG_TEMP_CONST);
 120             if (temps[src].state != TCG_TEMP_HAS_COPY) {
 121                 temps[src].state = TCG_TEMP_HAS_COPY;
 122                 temps[src].next_copy = src;
 123                 temps[src].prev_copy = src;
 124             }
 125             temps[dst].state = TCG_TEMP_COPY;
 126             temps[dst].val = src;
 127             temps[dst].next_copy = temps[src].next_copy;
 128             temps[dst].prev_copy = src;
 129             temps[temps[dst].next_copy].prev_copy = dst;
 130             temps[src].next_copy = dst;
 131         }
 132         gen_args[0] = dst;
 133         gen_args[1] = src;
 134 }
 135
 136 static void tcg_opt_gen_movi(TCGArg *gen_args, TCGArg dst, TCGArg val,
 137                              int nb_temps, int nb_globals)
 138 {
 139         reset_temp(dst, nb_temps, nb_globals);
 140         temps[dst].state = TCG_TEMP_CONST;
 141         temps[dst].val = val;
 142         gen_args[0] = dst;
 143         gen_args[1] = val;
 144 }
 145
 146 static TCGOpcode op_to_mov(TCGOpcode op)
 147 {
 148     switch (op_bits(op)) {
 149     case 32:
 150         return INDEX_op_mov_i32;
 151     case 64:
 152         return INDEX_op_mov_i64;
 153     default:
 154         fprintf(stderr, "op_to_mov: unexpected return value of "
 155                 "function op_bits.\n");
 156         tcg_abort();
 157     }
 158 }
 159
 160 static TCGArg do_constant_folding_2(TCGOpcode op, TCGArg x, TCGArg y)
 161 {
 162     switch (op) {
 163     CASE_OP_32_64(add):
 164         return x + y;
 165
 166     CASE_OP_32_64(sub):
 167         return x - y;
 168
 169     CASE_OP_32_64(mul):
 170         return x * y;
 171
 172     CASE_OP_32_64(and):
 173         return x & y;
 174
 175     CASE_OP_32_64(or):
 176         return x | y;
 177
 178     CASE_OP_32_64(xor):
 179         return x ^ y;
 180
 181     case INDEX_op_shl_i32:
 182         return (uint32_t)x << (uint32_t)y;
 183
 184     case INDEX_op_shl_i64:
 185         return (uint64_t)x << (uint64_t)y;
 186
 187     case INDEX_op_shr_i32:
 188         return (uint32_t)x >> (uint32_t)y;
 189
 190     case INDEX_op_shr_i64:
 191         return (uint64_t)x >> (uint64_t)y;
 192
 193     case INDEX_op_sar_i32:
 194         return (int32_t)x >> (int32_t)y;
 195
 196     case INDEX_op_sar_i64:
 197         return (int64_t)x >> (int64_t)y;
 198
 199     case INDEX_op_rotr_i32:
 200         x = ((uint32_t)x << (32 - y)) | ((uint32_t)x >> y);
 201         return x;
 202
 203     case INDEX_op_rotr_i64:
 204         x = ((uint64_t)x << (64 - y)) | ((uint64_t)x >> y);
 205         return x;
 206
 207     case INDEX_op_rotl_i32:
 208         x = ((uint32_t)x << y) | ((uint32_t)x >> (32 - y));
 209         return x;
 210
 211     case INDEX_op_rotl_i64:
 212         x = ((uint64_t)x << y) | ((uint64_t)x >> (64 - y));
 213         return x;
 214
 215     CASE_OP_32_64(not):
 216         return ~x;
 217
 218     CASE_OP_32_64(neg):
 219         return -x;
 220
 221     CASE_OP_32_64(andc):
 222         return x & ~y;
 223
 224     CASE_OP_32_64(orc):
 225         return x | ~y;
 226
 227     CASE_OP_32_64(eqv):
 228         return ~(x ^ y);
 229
 230     CASE_OP_32_64(nand):
 231         return ~(x & y);
 232
 233     CASE_OP_32_64(nor):
 234         return ~(x | y);
 235
 236     CASE_OP_32_64(ext8s):
 237         return (int8_t)x;
 238
 239     CASE_OP_32_64(ext16s):
 240         return (int16_t)x;
 241
 242     CASE_OP_32_64(ext8u):
 243         return (uint8_t)x;
 244
 245     CASE_OP_32_64(ext16u):
 246         return (uint16_t)x;
 247
 248     case INDEX_op_ext32s_i64:
 249         return (int32_t)x;
 250
 251     case INDEX_op_ext32u_i64:
 252         return (uint32_t)x;
 253
 254     default:
 255         fprintf(stderr,
 256                 "Unrecognized operation %d in do_constant_folding.\n", op);
 257         tcg_abort();
 258     }
 259 }
 260
 261 static TCGArg do_constant_folding(TCGOpcode op, TCGArg x, TCGArg y)
 262 {
 263     TCGArg res = do_constant_folding_2(op, x, y);
 264     if (op_bits(op) == 32) {
 265         res &= 0xffffffff;
 266     }
 267     return res;
 268 }
 269
 270 /* Propagate constants and copies, fold constant expressions. */
 271 static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,
 272                                     TCGArg *args, TCGOpDef *tcg_op_defs)
 273 {
 274     int i, nb_ops, op_index, nb_temps, nb_globals, nb_call_args;
 275     TCGOpcode op;
 276     const TCGOpDef *def;
 277     TCGArg *gen_args;
 278     TCGArg tmp;
 279     /* Array VALS has an element for each temp.
 280        If this temp holds a constant then its value is kept in VALS' element.
 281        If this temp is a copy of other ones then this equivalence class'
 282        representative is kept in VALS' element.
 283        If this temp is neither copy nor constant then corresponding VALS'
 284        element is unused. */
 285
 286     nb_temps = s->nb_temps;
 287     nb_globals = s->nb_globals;
 288     memset(temps, 0, nb_temps * sizeof(struct tcg_temp_info));
 289
 290     nb_ops = tcg_opc_ptr - gen_opc_buf;
 291     gen_args = args;
 292     for (op_index = 0; op_index < nb_ops; op_index++) {
 293         op = gen_opc_buf[op_index];
 294         def = &tcg_op_defs[op];
 295         /* Do copy propagation */
 296         if (!(def->flags & (TCG_OPF_CALL_CLOBBER | TCG_OPF_SIDE_EFFECTS))) {
 297             assert(op != INDEX_op_call);
 298             for (i = def->nb_oargs; i < def->nb_oargs + def->nb_iargs; i++) {
 299                 if (temps[args[i]].state == TCG_TEMP_COPY) {
 300                     args[i] = temps[args[i]].val;
 301                 }
 302             }
 303         }
 304
 305         /* For commutative operations make constant second argument */
 306         switch (op) {
 307         CASE_OP_32_64(add):
 308         CASE_OP_32_64(mul):
 309         CASE_OP_32_64(and):
 310         CASE_OP_32_64(or):
 311         CASE_OP_32_64(xor):
 312         CASE_OP_32_64(eqv):
 313         CASE_OP_32_64(nand):
 314         CASE_OP_32_64(nor):
 315             if (temps[args[1]].state == TCG_TEMP_CONST) {
 316                 tmp = args[1];
 317                 args[1] = args[2];
 318                 args[2] = tmp;
 319             }
 320             break;
 321         default:
 322             break;
 323         }
 324
 325         /* Simplify expression for "op r, a, 0 => mov r, a" cases */
 326         switch (op) {
 327         CASE_OP_32_64(add):
 328         CASE_OP_32_64(sub):
 329         CASE_OP_32_64(shl):
 330         CASE_OP_32_64(shr):
 331         CASE_OP_32_64(sar):
 332         CASE_OP_32_64(rotl):
 333         CASE_OP_32_64(rotr):
 334         CASE_OP_32_64(or):
 335         CASE_OP_32_64(xor):
 336             if (temps[args[1]].state == TCG_TEMP_CONST) {
 337                 /* Proceed with possible constant folding. */
 338                 break;
 339             }
 340             if (temps[args[2]].state == TCG_TEMP_CONST
 341                 && temps[args[2]].val == 0) {
 342                 if ((temps[args[0]].state == TCG_TEMP_COPY
 343                     && temps[args[0]].val == args[1])
 344                     || args[0] == args[1]) {
 345                     args += 3;
 346                     gen_opc_buf[op_index] = INDEX_op_nop;
 347                 } else {
 348                     gen_opc_buf[op_index] = op_to_mov(op);
 349                     tcg_opt_gen_mov(s, gen_args, args[0], args[1],
 350                                     nb_temps, nb_globals);
 351                     gen_args += 2;
 352                     args += 3;
 353                 }
 354                 continue;
 355             }
 356             break;
 357         default:
 358             break;
 359         }
 360
 361         /* Simplify expression for "op r, a, 0 => movi r, 0" cases */
 362         switch (op) {
 363         CASE_OP_32_64(mul):
 364             if ((temps[args[2]].state == TCG_TEMP_CONST
 365                 && temps[args[2]].val == 0)) {
 366                 gen_opc_buf[op_index] = op_to_movi(op);
 367                 tcg_opt_gen_movi(gen_args, args[0], 0, nb_temps, nb_globals);
 368                 args += 3;
 369                 gen_args += 2;
 370                 continue;
 371             }
 372             break;
 373         default:
 374             break;
 375         }
 376
 377         /* Simplify expression for "op r, a, a => mov r, a" cases */
 378         switch (op) {
 379         CASE_OP_32_64(or):
 380         CASE_OP_32_64(and):
 381             if (args[1] == args[2]) {
 382                 if (args[1] == args[0]) {
 383                     args += 3;
 384                     gen_opc_buf[op_index] = INDEX_op_nop;
 385                 } else {
 386                     gen_opc_buf[op_index] = op_to_mov(op);
 387                     tcg_opt_gen_mov(s, gen_args, args[0], args[1], nb_temps,
 388                                     nb_globals);
 389                     gen_args += 2;
 390                     args += 3;
 391                 }
 392                 continue;
 393             }
 394             break;
 395         default:
 396             break;
 397         }
 398
 399         /* Propagate constants through copy operations and do constant
 400            folding.  Constants will be substituted to arguments by register
 401            allocator where needed and possible.  Also detect copies. */
 402         switch (op) {
 403         CASE_OP_32_64(mov):
 404             if ((temps[args[1]].state == TCG_TEMP_COPY
 405                 && temps[args[1]].val == args[0])
 406                 || args[0] == args[1]) {
 407                 args += 2;
 408                 gen_opc_buf[op_index] = INDEX_op_nop;
 409                 break;
 410             }
 411             if (temps[args[1]].state != TCG_TEMP_CONST) {
 412                 tcg_opt_gen_mov(s, gen_args, args[0], args[1],
 413                                 nb_temps, nb_globals);
 414                 gen_args += 2;
 415                 args += 2;
 416                 break;
 417             }
 418             /* Source argument is constant.  Rewrite the operation and
 419                let movi case handle it. */
 420             op = op_to_movi(op);
 421             gen_opc_buf[op_index] = op;
 422             args[1] = temps[args[1]].val;
 423             /* fallthrough */
 424         CASE_OP_32_64(movi):
 425             tcg_opt_gen_movi(gen_args, args[0], args[1], nb_temps, nb_globals);
 426             gen_args += 2;
 427             args += 2;
 428             break;
 429         CASE_OP_32_64(not):
 430         CASE_OP_32_64(neg):
 431         CASE_OP_32_64(ext8s):
 432         CASE_OP_32_64(ext8u):
 433         CASE_OP_32_64(ext16s):
 434         CASE_OP_32_64(ext16u):
 435         case INDEX_op_ext32s_i64:
 436         case INDEX_op_ext32u_i64:
 437             if (temps[args[1]].state == TCG_TEMP_CONST) {
 438                 gen_opc_buf[op_index] = op_to_movi(op);
 439                 tmp = do_constant_folding(op, temps[args[1]].val, 0);
 440                 tcg_opt_gen_movi(gen_args, args[0], tmp, nb_temps, nb_globals);
 441                 gen_args += 2;
 442                 args += 2;
 443                 break;
 444             } else {
 445                 reset_temp(args[0], nb_temps, nb_globals);
 446                 gen_args[0] = args[0];
 447                 gen_args[1] = args[1];
 448                 gen_args += 2;
 449                 args += 2;
 450                 break;
 451             }
 452         CASE_OP_32_64(add):
 453         CASE_OP_32_64(sub):
 454         CASE_OP_32_64(mul):
 455         CASE_OP_32_64(or):
 456         CASE_OP_32_64(and):
 457         CASE_OP_32_64(xor):
 458         CASE_OP_32_64(shl):
 459         CASE_OP_32_64(shr):
 460         CASE_OP_32_64(sar):
 461         CASE_OP_32_64(rotl):
 462         CASE_OP_32_64(rotr):
 463         CASE_OP_32_64(andc):
 464         CASE_OP_32_64(orc):
 465         CASE_OP_32_64(eqv):
 466         CASE_OP_32_64(nand):
 467         CASE_OP_32_64(nor):
 468             if (temps[args[1]].state == TCG_TEMP_CONST
 469                 && temps[args[2]].state == TCG_TEMP_CONST) {
 470                 gen_opc_buf[op_index] = op_to_movi(op);
 471                 tmp = do_constant_folding(op, temps[args[1]].val,
 472                                           temps[args[2]].val);
 473                 tcg_opt_gen_movi(gen_args, args[0], tmp, nb_temps, nb_globals);
 474                 gen_args += 2;
 475                 args += 3;
 476                 break;
 477             } else {
 478                 reset_temp(args[0], nb_temps, nb_globals);
 479                 gen_args[0] = args[0];
 480                 gen_args[1] = args[1];
 481                 gen_args[2] = args[2];
 482                 gen_args += 3;
 483                 args += 3;
 484                 break;
 485             }
 486         case INDEX_op_call:
 487             nb_call_args = (args[0] >> 16) + (args[0] & 0xffff);
 488             if (!(args[nb_call_args + 1] & (TCG_CALL_CONST | TCG_CALL_PURE))) {
 489                 for (i = 0; i < nb_globals; i++) {
 490                     reset_temp(i, nb_temps, nb_globals);
 491                 }
 492             }
 493             for (i = 0; i < (args[0] >> 16); i++) {
 494                 reset_temp(args[i + 1], nb_temps, nb_globals);
 495             }
 496             i = nb_call_args + 3;
 497             while (i) {
 498                 *gen_args = *args;
 499                 args++;
 500                 gen_args++;
 501                 i--;
 502             }
 503             break;
 504         case INDEX_op_set_label:
 505         case INDEX_op_jmp:
 506         case INDEX_op_br:
 507         CASE_OP_32_64(brcond):
 508             memset(temps, 0, nb_temps * sizeof(struct tcg_temp_info));
 509             for (i = 0; i < def->nb_args; i++) {
 510                 *gen_args = *args;
 511                 args++;
 512                 gen_args++;
 513             }
 514             break;
 515         default:
 516             /* Default case: we do know nothing about operation so no
 517                propagation is done.  We only trash output args.  */
 518             for (i = 0; i < def->nb_oargs; i++) {
 519                 reset_temp(args[i], nb_temps, nb_globals);
 520             }
 521             for (i = 0; i < def->nb_args; i++) {
 522                 gen_args[i] = args[i];
 523             }
 524             args += def->nb_args;
 525             gen_args += def->nb_args;
 526             break;
 527         }
 528     }
 529
 530     return gen_args;
 531 }
 532
 533 TCGArg *tcg_optimize(TCGContext *s, uint16_t *tcg_opc_ptr,
 534         TCGArg *args, TCGOpDef *tcg_op_defs)
 535 {
 536     TCGArg *res;
 537     res = tcg_constant_folding(s, tcg_opc_ptr, args, tcg_op_defs);
 538     return res;
 539 }