src/mesa/drivers/dri/r300/compiler/radeon_emulate_loops.c

   1 /*
   2  * Copyright 2010 Tom Stellard <tstellar@gmail.com>
   3  *
   4  * All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining
   7  * a copy of this software and associated documentation files (the
   8  * "Software"), to deal in the Software without restriction, including
   9  * without limitation the rights to use, copy, modify, merge, publish,
  10  * distribute, sublicense, and/or sell copies of the Software, and to
  11  * permit persons to whom the Software is furnished to do so, subject to
  12  * the following conditions:
  13  *
  14  * The above copyright notice and this permission notice (including the
  15  * next paragraph) shall be included in all copies or substantial
  16  * portions of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  19  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  20  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  21  * IN NO EVENT SHALL THE COPYRIGHT OWNER(S) AND/OR ITS SUPPLIERS BE
  22  * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  23  * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  24  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  *
  26  */
  27
  28 /**
  29  * \file
  30  */
  31
  32 #include "radeon_emulate_loops.h"
  33
  34 #include "radeon_compiler.h"
  35 #include "radeon_dataflow.h"
  36
  37 #define VERBOSE 0
  38
  39 #define DBG(...) do { if (VERBOSE) fprintf(stderr, __VA_ARGS__); } while(0)
  40
  41 struct const_value {
  42         struct radeon_compiler * C;
  43         struct rc_src_register * Src;
  44         float Value;
  45         int HasValue;
  46 };
  47
  48 struct count_inst {
  49         struct radeon_compiler * C;
  50         int Index;
  51         rc_swizzle Swz;
  52         float Amount;
  53         int Unknown;
  54 };
  55
  56 static float get_constant_value(struct radeon_compiler * c,
  57                                                 struct rc_src_register * src,
  58                                                 int chan)
  59 {
  60         float base = 1.0f;
  61         int swz = GET_SWZ(src->Swizzle, chan);
  62         if(swz >= 4 || src->Index >= c->Program.Constants.Count ){
  63                 rc_error(c, "get_constant_value: Can't find a value.\n");
  64                 return 0.0f;
  65         }
  66         if(GET_BIT(src->Negate, chan)){
  67                 base = -1.0f;
  68         }
  69         return base *
  70                 c->Program.Constants.Constants[src->Index].u.Immediate[swz];
  71 }
  72
  73 static int src_reg_is_immediate(struct rc_src_register * src,
  74                                                 struct radeon_compiler * c)
  75 {
  76         return src->File == RC_FILE_CONSTANT &&
  77         c->Program.Constants.Constants[src->Index].Type==RC_CONSTANT_IMMEDIATE;
  78 }
  79
  80 static unsigned int loop_max_possible_iterations(struct radeon_compiler *c,
  81                         struct loop_info * loop)
  82 {
  83         unsigned int total_i = rc_recompute_ips(c);
  84         unsigned int loop_i = (loop->EndLoop->IP - loop->BeginLoop->IP) - 1;
  85         /* +1 because the program already has one iteration of the loop. */
  86         return 1 + ((c->max_alu_insts - total_i) / loop_i);
  87 }
  88
  89 static void unroll_loop(struct radeon_compiler * c, struct loop_info * loop,
  90                                                 unsigned int iterations)
  91 {
  92         unsigned int i;
  93         struct rc_instruction * ptr;
  94         struct rc_instruction * first = loop->BeginLoop->Next;
  95         struct rc_instruction * last = loop->EndLoop->Prev;
  96         struct rc_instruction * append_to = last;
  97         rc_remove_instruction(loop->BeginLoop);
  98         rc_remove_instruction(loop->EndLoop);
  99         for( i = 1; i < iterations; i++){
 100                 for(ptr = first; ptr != last->Next; ptr = ptr->Next){
 101                         struct rc_instruction *new = rc_alloc_instruction(c);
 102                         memcpy(new, ptr, sizeof(struct rc_instruction));
 103                         rc_insert_instruction(append_to, new);
 104                         append_to = new;
 105                 }
 106         }
 107 }
 108
 109
 110 static void update_const_value(void * data, struct rc_instruction * inst,
 111                 rc_register_file file, unsigned int index, unsigned int mask)
 112 {
 113         struct const_value * value = data;
 114         if(value->Src->File != file ||
 115            value->Src->Index != index ||
 116            !(1 << GET_SWZ(value->Src->Swizzle, 0) & mask)){
 117                 return;
 118         }
 119         switch(inst->U.I.Opcode){
 120         case RC_OPCODE_MOV:
 121                 if(!src_reg_is_immediate(&inst->U.I.SrcReg[0], value->C)){
 122                         return;
 123                 }
 124                 value->HasValue = 1;
 125                 value->Value =
 126                         get_constant_value(value->C, &inst->U.I.SrcReg[0], 0);
 127                 break;
 128         }
 129 }
 130
 131 static void get_incr_amount(void * data, struct rc_instruction * inst,
 132                 rc_register_file file, unsigned int index, unsigned int mask)
 133 {
 134         struct count_inst * count_inst = data;
 135         int amnt_src_index;
 136         const struct rc_opcode_info * opcode;
 137         float amount;
 138
 139         if(file != RC_FILE_TEMPORARY ||
 140            count_inst->Index != index ||
 141            (1 << GET_SWZ(count_inst->Swz,0) != mask)){
 142                 return;
 143         }
 144         /* Find the index of the counter register. */
 145         opcode = rc_get_opcode_info(inst->U.I.Opcode);
 146         if(opcode->NumSrcRegs != 2){
 147                 count_inst->Unknown = 1;
 148                 return;
 149         }
 150         if(inst->U.I.SrcReg[0].File == RC_FILE_TEMPORARY &&
 151            inst->U.I.SrcReg[0].Index == count_inst->Index &&
 152            inst->U.I.SrcReg[0].Swizzle == count_inst->Swz){
 153                 amnt_src_index = 1;
 154         } else if( inst->U.I.SrcReg[1].File == RC_FILE_TEMPORARY &&
 155                    inst->U.I.SrcReg[1].Index == count_inst->Index &&
 156                    inst->U.I.SrcReg[1].Swizzle == count_inst->Swz){
 157                 amnt_src_index = 0;
 158         }
 159         else{
 160                 count_inst->Unknown = 1;
 161                 return;
 162         }
 163         if(src_reg_is_immediate(&inst->U.I.SrcReg[amnt_src_index],
 164                                                         count_inst->C)){
 165                 amount = get_constant_value(count_inst->C,
 166                                 &inst->U.I.SrcReg[amnt_src_index], 0);
 167         }
 168         else{
 169                 count_inst->Unknown = 1 ;
 170                 return;
 171         }
 172         switch(inst->U.I.Opcode){
 173         case RC_OPCODE_ADD:
 174                 count_inst->Amount += amount;
 175                 break;
 176         case RC_OPCODE_SUB:
 177                 if(amnt_src_index == 0){
 178                         count_inst->Unknown = 0;
 179                         return;
 180                 }
 181                 count_inst->Amount -= amount;
 182                 break;
 183         default:
 184                 count_inst->Unknown = 1;
 185                 return;
 186         }
 187 }
 188
 189 /**
 190  * If c->max_alu_inst is -1, then all eligible loops will be unrolled regardless
 191  * of how many iterations they have.
 192  */
 193 static int try_unroll_loop(struct radeon_compiler * c, struct loop_info * loop)
 194 {
 195         int end_loops;
 196         int iterations;
 197         struct count_inst count_inst;
 198         float limit_value;
 199         struct rc_src_register * counter;
 200         struct rc_src_register * limit;
 201         struct const_value counter_value;
 202         struct rc_instruction * inst;
 203
 204         /* Find the counter and the upper limit */
 205
 206         if(src_reg_is_immediate(&loop->Cond->U.I.SrcReg[0], c)){
 207                 limit = &loop->Cond->U.I.SrcReg[0];
 208                 counter = &loop->Cond->U.I.SrcReg[1];
 209         }
 210         else if(src_reg_is_immediate(&loop->Cond->U.I.SrcReg[1], c)){
 211                 limit = &loop->Cond->U.I.SrcReg[1];
 212                 counter = &loop->Cond->U.I.SrcReg[0];
 213         }
 214         else{
 215                 DBG("No constant limit.\n");
 216                 return 0;
 217         }
 218
 219         /* Find the initial value of the counter */
 220         counter_value.Src = counter;
 221         counter_value.Value = 0.0f;
 222         counter_value.HasValue = 0;
 223         counter_value.C = c;
 224         for(inst = c->Program.Instructions.Next; inst != loop->BeginLoop;
 225                                                         inst = inst->Next){
 226                 rc_for_all_writes_mask(inst, update_const_value, &counter_value);
 227         }
 228         if(!counter_value.HasValue){
 229                 DBG("Initial counter value cannot be determined.\n");
 230                 return 0;
 231         }
 232         DBG("Initial counter value is %f\n", counter_value.Value);
 233         /* Determine how the counter is modified each loop */
 234         count_inst.C = c;
 235         count_inst.Index = counter->Index;
 236         count_inst.Swz = counter->Swizzle;
 237         count_inst.Amount = 0.0f;
 238         count_inst.Unknown = 0;
 239         end_loops = 1;
 240         for(inst = loop->BeginLoop->Next; end_loops > 0; inst = inst->Next){
 241                 switch(inst->U.I.Opcode){
 242                 /* XXX In the future we might want to try to unroll nested
 243                  * loops here.*/
 244                 case RC_OPCODE_BGNLOOP:
 245                         end_loops++;
 246                         break;
 247                 case RC_OPCODE_ENDLOOP:
 248                         loop->EndLoop = inst;
 249                         end_loops--;
 250                         break;
 251                 case RC_OPCODE_BRK:
 252                         /* Don't unroll loops if it has a BRK instruction
 253                          * other one used when testing the main conditional
 254                          * of the loop. */
 255
 256                         /* Make sure we haven't entered a nested loops. */
 257                         if(inst != loop->Brk && end_loops == 1) {
 258                                 return 0;
 259                         }
 260                         break;
 261                 /* XXX Check if the counter is modified within an if statement.
 262                  */
 263                 case RC_OPCODE_IF:
 264                         break;
 265                 default:
 266                         rc_for_all_writes_mask(inst, get_incr_amount, &count_inst);
 267                         if(count_inst.Unknown){
 268                                 return 0;
 269                         }
 270                         break;
 271                 }
 272         }
 273         /* Infinite loop */
 274         if(count_inst.Amount == 0.0f){
 275                 return 0;
 276         }
 277         DBG("Counter is increased by %f each iteration.\n", count_inst.Amount);
 278         /* Calculate the number of iterations of this loop.  Keeping this
 279          * simple, since we only support increment and decrement loops.
 280          */
 281         limit_value = get_constant_value(c, limit, 0);
 282         DBG("Limit is %f.\n", limit_value);
 283         /* The iteration calculations are opposite of what you would expect.
 284          * In a normal loop, if the condition is met, then loop continues, but
 285          * with our loops, if the condition is met, the is exited. */
 286         switch(loop->Cond->U.I.Opcode){
 287         case RC_OPCODE_SGE:
 288         case RC_OPCODE_SLE:
 289                 iterations = (int) ceilf((limit_value - counter_value.Value) /
 290                                                         count_inst.Amount);
 291                 break;
 292
 293         case RC_OPCODE_SGT:
 294         case RC_OPCODE_SLT:
 295                 iterations = (int) floorf((limit_value - counter_value.Value) /
 296                                                         count_inst.Amount) + 1;
 297                 break;
 298         default:
 299                 return 0;
 300         }
 301
 302         if (c->max_alu_insts > 0
 303                 && iterations > loop_max_possible_iterations(c, loop)) {
 304                 return 0;
 305         }
 306
 307         DBG("Loop will have %d iterations.\n", iterations);
 308
 309         /* Prepare loop for unrolling */
 310         rc_remove_instruction(loop->Cond);
 311         rc_remove_instruction(loop->If);
 312         rc_remove_instruction(loop->Brk);
 313         rc_remove_instruction(loop->EndIf);
 314
 315         unroll_loop(c, loop, iterations);
 316         loop->EndLoop = NULL;
 317         return 1;
 318 }
 319
 320 /**
 321  * @param c
 322  * @param loop
 323  * @param inst A pointer to a BGNLOOP instruction.
 324  * @return 1 if all of the members of loop where set.
 325  * @return 0 if there was an error and some members of loop are still NULL.
 326  */
 327 static int build_loop_info(struct radeon_compiler * c, struct loop_info * loop,
 328                                                 struct rc_instruction * inst)
 329 {
 330         struct rc_instruction * ptr;
 331
 332         if(inst->U.I.Opcode != RC_OPCODE_BGNLOOP){
 333                 rc_error(c, "%s: expected BGNLOOP", __FUNCTION__);
 334                 return 0;
 335         }
 336
 337         memset(loop, 0, sizeof(struct loop_info));
 338
 339         loop->BeginLoop = inst;
 340
 341         for(ptr = loop->BeginLoop->Next; !loop->EndLoop; ptr = ptr->Next) {
 342
 343                 if (ptr == &c->Program.Instructions) {
 344                         rc_error(c, "%s: BGNLOOP without an ENDLOOOP.\n",
 345                                                                 __FUNCTION__);
 346                         return 0;
 347                 }
 348
 349                 switch(ptr->U.I.Opcode){
 350                 case RC_OPCODE_BGNLOOP:
 351                 {
 352                         /* Nested loop, skip ahead to the end. */
 353                         unsigned int loop_depth = 1;
 354                         for(ptr = ptr->Next; ptr != &c->Program.Instructions;
 355                                                         ptr = ptr->Next){
 356                                 if (ptr->U.I.Opcode == RC_OPCODE_BGNLOOP) {
 357                                         loop_depth++;
 358                                 } else if (ptr->U.I.Opcode == RC_OPCODE_ENDLOOP) {
 359                                         if (!--loop_depth) {
 360                                                 break;
 361                                         }
 362                                 }
 363                         }
 364                         if (ptr == &c->Program.Instructions) {
 365                                 rc_error(c, "%s: BGNLOOP without an ENDLOOOP\n",
 366                                                                 __FUNCTION__);
 367                                         return 0;
 368                         }
 369                         break;
 370                 }
 371                 case RC_OPCODE_BRK:
 372                         if(ptr->Next->U.I.Opcode != RC_OPCODE_ENDIF
 373                                         || ptr->Prev->U.I.Opcode != RC_OPCODE_IF
 374                                         || loop->Brk){
 375                                 continue;
 376                         }
 377                         loop->Brk = ptr;
 378                         loop->If = ptr->Prev;
 379                         loop->EndIf = ptr->Next;
 380                         switch(loop->If->Prev->U.I.Opcode){
 381                         case RC_OPCODE_SLT:
 382                         case RC_OPCODE_SGE:
 383                         case RC_OPCODE_SGT:
 384                         case RC_OPCODE_SLE:
 385                         case RC_OPCODE_SEQ:
 386                         case RC_OPCODE_SNE:
 387                                 break;
 388                         default:
 389                                 return 0;
 390                         }
 391                         loop->Cond = loop->If->Prev;
 392                         break;
 393
 394                 case RC_OPCODE_ENDLOOP:
 395                         loop->EndLoop = ptr;
 396                         break;
 397                 }
 398         }
 399
 400         if (loop->BeginLoop && loop->Brk && loop->If && loop->EndIf
 401                                         && loop->Cond && loop->EndLoop) {
 402                 return 1;
 403         }
 404         return 0;
 405 }
 406
 407 /**
 408  * This function prepares a loop to be unrolled by converting it into an if
 409  * statement.  Here is an outline of the conversion process:
 410  * BGNLOOP;                             -> BGNLOOP;
 411  * <Additional conditional code>        -> <Additional conditional code>
 412  * SGE/SLT temp[0], temp[1], temp[2];   -> SLT/SGE temp[0], temp[1], temp[2];
 413  * IF temp[0];                          -> IF temp[0];
 414  * BRK;                                 ->
 415  * ENDIF;                               -> <Loop Body>
 416  * <Loop Body>                          -> ENDIF;
 417  * ENDLOOP;                             -> ENDLOOP
 418  *
 419  * @param inst A pointer to a BGNLOOP instruction.
 420  * @return 1 for success, 0 for failure
 421  */
 422 static int transform_loop(struct emulate_loop_state * s,
 423                                                 struct rc_instruction * inst)
 424 {
 425         struct loop_info * loop;
 426
 427         memory_pool_array_reserve(&s->C->Pool, struct loop_info,
 428                         s->Loops, s->LoopCount, s->LoopReserved, 1);
 429
 430         loop = &s->Loops[s->LoopCount++];
 431
 432         if (!build_loop_info(s->C, loop, inst)) {
 433                 rc_error(s->C, "Failed to build loop info\n");
 434                 return 0;
 435         }
 436
 437         if(try_unroll_loop(s->C, loop)){
 438                 return 1;
 439         }
 440
 441         /* Reverse the conditional instruction */
 442         switch(loop->Cond->U.I.Opcode){
 443         case RC_OPCODE_SGE:
 444                 loop->Cond->U.I.Opcode = RC_OPCODE_SLT;
 445                 break;
 446         case RC_OPCODE_SLT:
 447                 loop->Cond->U.I.Opcode = RC_OPCODE_SGE;
 448                 break;
 449         case RC_OPCODE_SLE:
 450                 loop->Cond->U.I.Opcode = RC_OPCODE_SGT;
 451                 break;
 452         case RC_OPCODE_SGT:
 453                 loop->Cond->U.I.Opcode = RC_OPCODE_SLE;
 454                 break;
 455         case RC_OPCODE_SEQ:
 456                 loop->Cond->U.I.Opcode = RC_OPCODE_SNE;
 457                 break;
 458         case RC_OPCODE_SNE:
 459                 loop->Cond->U.I.Opcode = RC_OPCODE_SEQ;
 460                 break;
 461         default:
 462                 rc_error(s->C, "loop->Cond is not a conditional.\n");
 463                 return 0;
 464         }
 465
 466         /* Prepare the loop to be emulated */
 467         rc_remove_instruction(loop->Brk);
 468         rc_remove_instruction(loop->EndIf);
 469         rc_insert_instruction(loop->EndLoop->Prev, loop->EndIf);
 470         return 1;
 471 }
 472
 473 void rc_transform_loops(struct radeon_compiler *c, void *user)
 474 {
 475         struct emulate_loop_state * s = &c->loop_state;
 476         struct rc_instruction * ptr;
 477
 478         memset(s, 0, sizeof(struct emulate_loop_state));
 479         s->C = c;
 480         for(ptr = s->C->Program.Instructions.Next;
 481                         ptr != &s->C->Program.Instructions; ptr = ptr->Next) {
 482                 if(ptr->Type == RC_INSTRUCTION_NORMAL &&
 483                                         ptr->U.I.Opcode == RC_OPCODE_BGNLOOP){
 484                         if (!transform_loop(s, ptr))
 485                                 return;
 486                 }
 487         }
 488 }
 489
 490 void rc_unroll_loops(struct radeon_compiler *c, void *user)
 491 {
 492         struct rc_instruction * inst;
 493         struct loop_info loop;
 494
 495         for(inst = c->Program.Instructions.Next;
 496                         inst != &c->Program.Instructions; inst = inst->Next) {
 497
 498                 if (inst->U.I.Opcode == RC_OPCODE_BGNLOOP) {
 499                         if (build_loop_info(c, &loop, inst)) {
 500                                 try_unroll_loop(c, &loop);
 501                         }
 502                 }
 503         }
 504 }
 505
 506 void rc_emulate_loops(struct radeon_compiler *c, void *user)
 507 {
 508         struct emulate_loop_state * s = &c->loop_state;
 509         int i;
 510         /* Iterate backwards of the list of loops so that loops that nested
 511          * loops are unrolled first.
 512          */
 513         for( i = s->LoopCount - 1; i >= 0; i-- ){
 514                 if(!s->Loops[i].EndLoop){
 515                         continue;
 516                 }
 517                 unsigned int iterations = loop_max_possible_iterations(
 518                                         s->C, &s->Loops[i]);
 519                 unroll_loop(s->C, &s->Loops[i], iterations);
 520         }
 521 }