src/panfrost/midgard/mir.c

   1 /*
   2  * Copyright (C) 2019 Alyssa Rosenzweig <alyssa@rosenzweig.io>
   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 FROM,
  20  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  21  * SOFTWARE.
  22  */
  23
  24 #include "compiler.h"
  25 #include "midgard_ops.h"
  26
  27 void mir_rewrite_index_src_single(midgard_instruction *ins, unsigned old, unsigned new)
  28 {
  29         for (unsigned i = 0; i < ARRAY_SIZE(ins->src); ++i) {
  30                 if (ins->src[i] == old)
  31                         ins->src[i] = new;
  32         }
  33 }
  34
  35 void mir_rewrite_index_dst_single(midgard_instruction *ins, unsigned old, unsigned new)
  36 {
  37         if (ins->dest == old)
  38                 ins->dest = new;
  39 }
  40
  41 static midgard_vector_alu_src
  42 mir_get_alu_src(midgard_instruction *ins, unsigned idx)
  43 {
  44         unsigned b = (idx == 0) ? ins->alu.src1 : ins->alu.src2;
  45         return vector_alu_from_unsigned(b);
  46 }
  47
  48 static void
  49 mir_rewrite_index_src_single_swizzle(midgard_instruction *ins, unsigned old, unsigned new, unsigned *swizzle)
  50 {
  51         for (unsigned i = 0; i < ARRAY_SIZE(ins->src); ++i) {
  52                 if (ins->src[i] != old) continue;
  53
  54                 ins->src[i] = new;
  55                 mir_compose_swizzle(ins->swizzle[i], swizzle, ins->swizzle[i]);
  56         }
  57 }
  58
  59 void
  60 mir_rewrite_index_src(compiler_context *ctx, unsigned old, unsigned new)
  61 {
  62         mir_foreach_instr_global(ctx, ins) {
  63                 mir_rewrite_index_src_single(ins, old, new);
  64         }
  65 }
  66
  67 void
  68 mir_rewrite_index_src_swizzle(compiler_context *ctx, unsigned old, unsigned new, unsigned *swizzle)
  69 {
  70         mir_foreach_instr_global(ctx, ins) {
  71                 mir_rewrite_index_src_single_swizzle(ins, old, new, swizzle);
  72         }
  73 }
  74
  75 void
  76 mir_rewrite_index_dst(compiler_context *ctx, unsigned old, unsigned new)
  77 {
  78         mir_foreach_instr_global(ctx, ins) {
  79                 mir_rewrite_index_dst_single(ins, old, new);
  80         }
  81 }
  82
  83 void
  84 mir_rewrite_index(compiler_context *ctx, unsigned old, unsigned new)
  85 {
  86         mir_rewrite_index_src(ctx, old, new);
  87         mir_rewrite_index_dst(ctx, old, new);
  88 }
  89
  90 unsigned
  91 mir_use_count(compiler_context *ctx, unsigned value)
  92 {
  93         unsigned used_count = 0;
  94
  95         mir_foreach_instr_global(ctx, ins) {
  96                 if (mir_has_arg(ins, value))
  97                         ++used_count;
  98         }
  99
 100         return used_count;
 101 }
 102
 103 /* Checks if a value is used only once (or totally dead), which is an important
 104  * heuristic to figure out if certain optimizations are Worth It (TM) */
 105
 106 bool
 107 mir_single_use(compiler_context *ctx, unsigned value)
 108 {
 109         /* We can replicate constants in places so who cares */
 110         if (value == SSA_FIXED_REGISTER(REGISTER_CONSTANT))
 111                 return true;
 112
 113         return mir_use_count(ctx, value) <= 1;
 114 }
 115
 116 static bool
 117 mir_nontrivial_raw_mod(midgard_vector_alu_src src, bool is_int)
 118 {
 119         if (is_int)
 120                 return src.mod == midgard_int_shift;
 121         else
 122                 return src.mod;
 123 }
 124
 125 static bool
 126 mir_nontrivial_mod(midgard_vector_alu_src src, bool is_int, unsigned mask, unsigned *swizzle)
 127 {
 128         if (mir_nontrivial_raw_mod(src, is_int)) return true;
 129
 130         /* size-conversion */
 131         if (src.half) return true;
 132
 133         for (unsigned c = 0; c < 16; ++c) {
 134                 if (!(mask & (1 << c))) continue;
 135                 if (swizzle[c] != c) return true;
 136         }
 137
 138         return false;
 139 }
 140
 141 bool
 142 mir_nontrivial_source2_mod(midgard_instruction *ins)
 143 {
 144         bool is_int = midgard_is_integer_op(ins->alu.op);
 145
 146         midgard_vector_alu_src src2 =
 147                 vector_alu_from_unsigned(ins->alu.src2);
 148
 149         return mir_nontrivial_mod(src2, is_int, ins->mask, ins->swizzle[1]);
 150 }
 151
 152 bool
 153 mir_nontrivial_source2_mod_simple(midgard_instruction *ins)
 154 {
 155         bool is_int = midgard_is_integer_op(ins->alu.op);
 156
 157         midgard_vector_alu_src src2 =
 158                 vector_alu_from_unsigned(ins->alu.src2);
 159
 160         return mir_nontrivial_raw_mod(src2, is_int) || src2.half;
 161 }
 162
 163 bool
 164 mir_nontrivial_outmod(midgard_instruction *ins)
 165 {
 166         bool is_int = midgard_is_integer_op(ins->alu.op);
 167         unsigned mod = ins->alu.outmod;
 168
 169         /* Pseudo-outmod */
 170         if (ins->invert)
 171                 return true;
 172
 173         /* Type conversion is a sort of outmod */
 174         if (ins->alu.dest_override != midgard_dest_override_none)
 175                 return true;
 176
 177         if (is_int)
 178                 return mod != midgard_outmod_int_wrap;
 179         else
 180                 return mod != midgard_outmod_none;
 181 }
 182
 183 /* Checks if an index will be used as a special register -- basically, if we're
 184  * used as the input to a non-ALU op */
 185
 186 bool
 187 mir_special_index(compiler_context *ctx, unsigned idx)
 188 {
 189         mir_foreach_instr_global(ctx, ins) {
 190                 bool is_ldst = ins->type == TAG_LOAD_STORE_4;
 191                 bool is_tex = ins->type == TAG_TEXTURE_4;
 192                 bool is_writeout = ins->compact_branch && ins->writeout;
 193
 194                 if (!(is_ldst || is_tex || is_writeout))
 195                         continue;
 196
 197                 if (mir_has_arg(ins, idx))
 198                         return true;
 199         }
 200
 201         return false;
 202 }
 203
 204 /* Is a node written before a given instruction? */
 205
 206 bool
 207 mir_is_written_before(compiler_context *ctx, midgard_instruction *ins, unsigned node)
 208 {
 209         if (node >= SSA_FIXED_MINIMUM)
 210                 return true;
 211
 212         mir_foreach_instr_global(ctx, q) {
 213                 if (q == ins)
 214                         break;
 215
 216                 if (q->dest == node)
 217                         return true;
 218         }
 219
 220         return false;
 221 }
 222
 223 /* Grabs the type size. */
 224
 225 midgard_reg_mode
 226 mir_typesize(midgard_instruction *ins)
 227 {
 228         if (ins->compact_branch)
 229                 return midgard_reg_mode_32;
 230
 231         /* TODO: Type sizes for texture */
 232         if (ins->type == TAG_TEXTURE_4)
 233                 return midgard_reg_mode_32;
 234
 235         if (ins->type == TAG_LOAD_STORE_4)
 236                 return GET_LDST_SIZE(load_store_opcode_props[ins->load_store.op].props);
 237
 238         if (ins->type == TAG_ALU_4) {
 239                 midgard_reg_mode mode = ins->alu.reg_mode;
 240
 241                 /* If we have an override, step down by half */
 242                 if (ins->alu.dest_override != midgard_dest_override_none) {
 243                         assert(mode > midgard_reg_mode_8);
 244                         mode--;
 245                 }
 246
 247                 return mode;
 248         }
 249
 250         unreachable("Invalid instruction type");
 251 }
 252
 253 /* Grabs the size of a source */
 254
 255 midgard_reg_mode
 256 mir_srcsize(midgard_instruction *ins, unsigned i)
 257 {
 258         /* TODO: 16-bit textures/ldst */
 259         if (ins->type == TAG_TEXTURE_4 || ins->type == TAG_LOAD_STORE_4)
 260                 return midgard_reg_mode_32;
 261
 262         /* TODO: 16-bit branches */
 263         if (ins->compact_branch)
 264                 return midgard_reg_mode_32;
 265
 266         if (i >= 2) {
 267                 /* TODO: 16-bit conditions, ffma */
 268                 return midgard_reg_mode_32;
 269         }
 270
 271         /* Default to type of the instruction */
 272
 273         midgard_reg_mode mode = ins->alu.reg_mode;
 274
 275         /* If we have a half modifier, step down by half */
 276
 277         if ((mir_get_alu_src(ins, i)).half) {
 278                 assert(mode > midgard_reg_mode_8);
 279                 mode--;
 280         }
 281
 282         return mode;
 283 }
 284
 285 midgard_reg_mode
 286 mir_mode_for_destsize(unsigned size)
 287 {
 288         switch (size) {
 289         case 8:
 290                 return midgard_reg_mode_8;
 291         case 16:
 292                 return midgard_reg_mode_16;
 293         case 32:
 294                 return midgard_reg_mode_32;
 295         case 64:
 296                 return midgard_reg_mode_64;
 297         default:
 298                 unreachable("Unknown destination size");
 299         }
 300 }
 301
 302
 303 /* Converts per-component mask to a byte mask */
 304
 305 uint16_t
 306 mir_to_bytemask(midgard_reg_mode mode, unsigned mask)
 307 {
 308         switch (mode) {
 309         case midgard_reg_mode_8:
 310                 return mask;
 311
 312         case midgard_reg_mode_16: {
 313                 unsigned space =
 314                         (mask & 0x1) |
 315                         ((mask & 0x2) << (2 - 1)) |
 316                         ((mask & 0x4) << (4 - 2)) |
 317                         ((mask & 0x8) << (6 - 3)) |
 318                         ((mask & 0x10) << (8 - 4)) |
 319                         ((mask & 0x20) << (10 - 5)) |
 320                         ((mask & 0x40) << (12 - 6)) |
 321                         ((mask & 0x80) << (14 - 7));
 322
 323                 return space | (space << 1);
 324         }
 325
 326         case midgard_reg_mode_32: {
 327                 unsigned space =
 328                         (mask & 0x1) |
 329                         ((mask & 0x2) << (4 - 1)) |
 330                         ((mask & 0x4) << (8 - 2)) |
 331                         ((mask & 0x8) << (12 - 3));
 332
 333                 return space | (space << 1) | (space << 2) | (space << 3);
 334         }
 335
 336         case midgard_reg_mode_64: {
 337                 unsigned A = (mask & 0x1) ? 0xFF : 0x00;
 338                 unsigned B = (mask & 0x2) ? 0xFF : 0x00;
 339                 return A | (B << 8);
 340         }
 341
 342         default:
 343                 unreachable("Invalid register mode");
 344         }
 345 }
 346
 347 /* ...and the inverse */
 348
 349 unsigned
 350 mir_bytes_for_mode(midgard_reg_mode mode)
 351 {
 352         switch (mode) {
 353         case midgard_reg_mode_8:
 354                 return 1;
 355         case midgard_reg_mode_16:
 356                 return 2;
 357         case midgard_reg_mode_32:
 358                 return 4;
 359         case midgard_reg_mode_64:
 360                 return 8;
 361         default:
 362                 unreachable("Invalid register mode");
 363         }
 364 }
 365
 366 uint16_t
 367 mir_from_bytemask(uint16_t bytemask, midgard_reg_mode mode)
 368 {
 369         unsigned value = 0;
 370         unsigned count = mir_bytes_for_mode(mode);
 371
 372         for (unsigned c = 0, d = 0; c < 16; c += count, ++d) {
 373                 bool a = (bytemask & (1 << c)) != 0;
 374
 375                 for (unsigned q = c; q < count; ++q)
 376                         assert(((bytemask & (1 << q)) != 0) == a);
 377
 378                 value |= (a << d);
 379         }
 380
 381         return value;
 382 }
 383
 384 /* Rounds down a bytemask to fit a given component count. Iterate each
 385  * component, and check if all bytes in the component are masked on */
 386
 387 uint16_t
 388 mir_round_bytemask_down(uint16_t mask, midgard_reg_mode mode)
 389 {
 390         unsigned bytes = mir_bytes_for_mode(mode);
 391         unsigned maxmask = mask_of(bytes);
 392         unsigned channels = 16 / bytes;
 393
 394         for (unsigned c = 0; c < channels; ++c) {
 395                 /* Get bytes in component */
 396                 unsigned submask = (mask >> (c * bytes)) & maxmask;
 397
 398                 if (submask != maxmask)
 399                         mask &= ~(maxmask << (c * bytes));
 400         }
 401
 402         return mask;
 403 }
 404
 405 /* Grabs the per-byte mask of an instruction (as opposed to per-component) */
 406
 407 uint16_t
 408 mir_bytemask(midgard_instruction *ins)
 409 {
 410         return mir_to_bytemask(mir_typesize(ins), ins->mask);
 411 }
 412
 413 void
 414 mir_set_bytemask(midgard_instruction *ins, uint16_t bytemask)
 415 {
 416         ins->mask = mir_from_bytemask(bytemask, mir_typesize(ins));
 417 }
 418
 419 /* Checks if we should use an upper destination override, rather than the lower
 420  * one in the IR. Returns zero if no, returns the bytes to shift otherwise */
 421
 422 unsigned
 423 mir_upper_override(midgard_instruction *ins)
 424 {
 425         /* If there is no override, there is no upper override, tautology */
 426         if (ins->alu.dest_override == midgard_dest_override_none)
 427                 return 0;
 428
 429         /* Make sure we didn't already lower somehow */
 430         assert(ins->alu.dest_override == midgard_dest_override_lower);
 431
 432         /* What is the mask in terms of currently? */
 433         midgard_reg_mode type = mir_typesize(ins);
 434
 435         /* There are 16 bytes per vector, so there are (16/bytes)
 436          * components per vector. So the magic half is half of
 437          * (16/bytes), which simplifies to 8/bytes */
 438
 439         unsigned threshold = 8 / mir_bytes_for_mode(type);
 440
 441         /* How many components did we shift over? */
 442         unsigned zeroes = __builtin_ctz(ins->mask);
 443
 444         /* Did we hit the threshold? */
 445         return (zeroes >= threshold) ? threshold : 0;
 446 }
 447
 448 /* Creates a mask of the components of a node read by an instruction, by
 449  * analyzing the swizzle with respect to the instruction's mask. E.g.:
 450  *
 451  *  fadd r0.xz, r1.yyyy, r2.zwyx
 452  *
 453  * will return a mask of Z/Y for r2
 454  */
 455
 456 static uint16_t
 457 mir_bytemask_of_read_components_single(unsigned *swizzle, unsigned inmask, midgard_reg_mode mode)
 458 {
 459         unsigned cmask = 0;
 460
 461         for (unsigned c = 0; c < MIR_VEC_COMPONENTS; ++c) {
 462                 if (!(inmask & (1 << c))) continue;
 463                 cmask |= (1 << swizzle[c]);
 464         }
 465
 466         return mir_to_bytemask(mode, cmask);
 467 }
 468
 469 uint16_t
 470 mir_bytemask_of_read_components(midgard_instruction *ins, unsigned node)
 471 {
 472         uint16_t mask = 0;
 473
 474         if (node == ~0)
 475                 return 0;
 476
 477         mir_foreach_src(ins, i) {
 478                 if (ins->src[i] != node) continue;
 479
 480                 /* Branch writeout uses all components */
 481                 if (ins->compact_branch && ins->writeout && (i == 0))
 482                         return 0xFFFF;
 483
 484                 /* Conditional branches read one 32-bit component = 4 bytes (TODO: multi branch??) */
 485                 if (ins->compact_branch && ins->branch.conditional && (i == 0))
 486                         return 0xF;
 487
 488                 /* ALU ops act componentwise so we need to pay attention to
 489                  * their mask. Texture/ldst does not so we don't clamp source
 490                  * readmasks based on the writemask */
 491                 unsigned qmask = (ins->type == TAG_ALU_4) ? ins->mask : ~0;
 492
 493                 /* Handle dot products and things */
 494                 if (ins->type == TAG_ALU_4 && !ins->compact_branch) {
 495                         unsigned props = alu_opcode_props[ins->alu.op].props;
 496
 497                         unsigned channel_override = GET_CHANNEL_COUNT(props);
 498
 499                         if (channel_override)
 500                                 qmask = mask_of(channel_override);
 501                 }
 502
 503                 mask |= mir_bytemask_of_read_components_single(ins->swizzle[i], qmask, mir_srcsize(ins, i));
 504         }
 505
 506         return mask;
 507 }
 508
 509 /* Register allocation occurs after instruction scheduling, which is fine until
 510  * we start needing to spill registers and therefore insert instructions into
 511  * an already-scheduled program. We don't have to be terribly efficient about
 512  * this, since spilling is already slow. So just semantically we need to insert
 513  * the instruction into a new bundle before/after the bundle of the instruction
 514  * in question */
 515
 516 static midgard_bundle
 517 mir_bundle_for_op(compiler_context *ctx, midgard_instruction ins)
 518 {
 519         midgard_instruction *u = mir_upload_ins(ctx, ins);
 520
 521         midgard_bundle bundle = {
 522                 .tag = ins.type,
 523                 .instruction_count = 1,
 524                 .instructions = { u },
 525         };
 526
 527         if (bundle.tag == TAG_ALU_4) {
 528                 assert(OP_IS_MOVE(u->alu.op));
 529                 u->unit = UNIT_VMUL;
 530
 531                 size_t bytes_emitted = sizeof(uint32_t) + sizeof(midgard_reg_info) + sizeof(midgard_vector_alu);
 532                 bundle.padding = ~(bytes_emitted - 1) & 0xF;
 533                 bundle.control = ins.type | u->unit;
 534         }
 535
 536         return bundle;
 537 }
 538
 539 static unsigned
 540 mir_bundle_idx_for_ins(midgard_instruction *tag, midgard_block *block)
 541 {
 542         midgard_bundle *bundles =
 543                 (midgard_bundle *) block->bundles.data;
 544
 545         size_t count = (block->bundles.size / sizeof(midgard_bundle));
 546
 547         for (unsigned i = 0; i < count; ++i) {
 548                 for (unsigned j = 0; j < bundles[i].instruction_count; ++j) {
 549                         if (bundles[i].instructions[j] == tag)
 550                                 return i;
 551                 }
 552         }
 553
 554         mir_print_instruction(tag);
 555         unreachable("Instruction not scheduled in block");
 556 }
 557
 558 void
 559 mir_insert_instruction_before_scheduled(
 560         compiler_context *ctx,
 561         midgard_block *block,
 562         midgard_instruction *tag,
 563         midgard_instruction ins)
 564 {
 565         unsigned before = mir_bundle_idx_for_ins(tag, block);
 566         size_t count = util_dynarray_num_elements(&block->bundles, midgard_bundle);
 567         UNUSED void *unused = util_dynarray_grow(&block->bundles, midgard_bundle, 1);
 568
 569         midgard_bundle *bundles = (midgard_bundle *) block->bundles.data;
 570         memmove(bundles + before + 1, bundles + before, (count - before) * sizeof(midgard_bundle));
 571         midgard_bundle *before_bundle = bundles + before + 1;
 572
 573         midgard_bundle new = mir_bundle_for_op(ctx, ins);
 574         memcpy(bundles + before, &new, sizeof(new));
 575
 576         list_addtail(&new.instructions[0]->link, &before_bundle->instructions[0]->link);
 577         block->quadword_count += midgard_word_size[new.tag];
 578 }
 579
 580 void
 581 mir_insert_instruction_after_scheduled(
 582         compiler_context *ctx,
 583         midgard_block *block,
 584         midgard_instruction *tag,
 585         midgard_instruction ins)
 586 {
 587         /* We need to grow the bundles array to add our new bundle */
 588         size_t count = util_dynarray_num_elements(&block->bundles, midgard_bundle);
 589         UNUSED void *unused = util_dynarray_grow(&block->bundles, midgard_bundle, 1);
 590
 591         /* Find the bundle that we want to insert after */
 592         unsigned after = mir_bundle_idx_for_ins(tag, block);
 593
 594         /* All the bundles after that one, we move ahead by one */
 595         midgard_bundle *bundles = (midgard_bundle *) block->bundles.data;
 596         memmove(bundles + after + 2, bundles + after + 1, (count - after - 1) * sizeof(midgard_bundle));
 597         midgard_bundle *after_bundle = bundles + after;
 598
 599         midgard_bundle new = mir_bundle_for_op(ctx, ins);
 600         memcpy(bundles + after + 1, &new, sizeof(new));
 601         list_add(&new.instructions[0]->link, &after_bundle->instructions[after_bundle->instruction_count - 1]->link);
 602         block->quadword_count += midgard_word_size[new.tag];
 603 }
 604
 605 /* Flip the first-two arguments of a (binary) op. Currently ALU
 606  * only, no known uses for ldst/tex */
 607
 608 void
 609 mir_flip(midgard_instruction *ins)
 610 {
 611         unsigned temp = ins->src[0];
 612         ins->src[0] = ins->src[1];
 613         ins->src[1] = temp;
 614
 615         assert(ins->type == TAG_ALU_4);
 616
 617         temp = ins->alu.src1;
 618         ins->alu.src1 = ins->alu.src2;
 619         ins->alu.src2 = temp;
 620
 621         unsigned temp_swizzle[16];
 622         memcpy(temp_swizzle, ins->swizzle[0], sizeof(ins->swizzle[0]));
 623         memcpy(ins->swizzle[0], ins->swizzle[1], sizeof(ins->swizzle[0]));
 624         memcpy(ins->swizzle[1], temp_swizzle, sizeof(ins->swizzle[0]));
 625 }
 626
 627 /* Before squashing, calculate ctx->temp_count just by observing the MIR */
 628
 629 void
 630 mir_compute_temp_count(compiler_context *ctx)
 631 {
 632         if (ctx->temp_count)
 633                 return;
 634
 635         unsigned max_dest = 0;
 636
 637         mir_foreach_instr_global(ctx, ins) {
 638                 if (ins->dest < SSA_FIXED_MINIMUM)
 639                         max_dest = MAX2(max_dest, ins->dest + 1);
 640         }
 641
 642         ctx->temp_count = max_dest;
 643 }