skip.c

   1 #include "expr.h"
   2 #include "loc.h"
   3 #include "scop.h"
   4 #include "skip.h"
   5
   6 /* Do we need to construct a skip condition of the given type
   7  * on an if statement, given that the if condition is non-affine?
   8  *
   9  * pet_scop_filter_skip can only handle the case where the if condition
  10  * holds (the then branch) and the skip condition is universal.
  11  * In any other case, we need to construct a new skip condition.
  12  */
  13 static int if_need_skip_non(struct pet_scop *scop_then,
  14         struct pet_scop *scop_else, int have_else, enum pet_skip type)
  15 {
  16         if (have_else && scop_else && pet_scop_has_skip(scop_else, type))
  17                 return 1;
  18         if (scop_then && pet_scop_has_skip(scop_then, type) &&
  19             !pet_scop_has_universal_skip(scop_then, type))
  20                 return 1;
  21         return 0;
  22 }
  23
  24 /* Do we need to construct a skip condition of the given type
  25  * on an if statement, given that the if condition is affine?
  26  *
  27  * There is no need to construct a new skip condition if all
  28  * the skip conditions are affine.
  29  */
  30 static int if_need_skip_aff(struct pet_scop *scop_then,
  31         struct pet_scop *scop_else, int have_else, enum pet_skip type)
  32 {
  33         if (scop_then && pet_scop_has_var_skip(scop_then, type))
  34                 return 1;
  35         if (have_else && scop_else && pet_scop_has_var_skip(scop_else, type))
  36                 return 1;
  37         return 0;
  38 }
  39
  40 /* Do we need to construct a skip condition of the given type
  41  * on an if statement?
  42  */
  43 static int if_need_skip(struct pet_scop *scop_then, struct pet_scop *scop_else,
  44         int have_else, enum pet_skip type, int affine)
  45 {
  46         if (affine)
  47                 return if_need_skip_aff(scop_then, scop_else, have_else, type);
  48         else
  49                 return if_need_skip_non(scop_then, scop_else, have_else, type);
  50 }
  51
  52 /* Construct an affine expression pet_expr that evaluates
  53  * to the constant "val".
  54  */
  55 static __isl_give pet_expr *universally(isl_ctx *ctx, int val)
  56 {
  57         isl_local_space *ls;
  58         isl_aff *aff;
  59         isl_multi_pw_aff *mpa;
  60
  61         ls = isl_local_space_from_space(isl_space_set_alloc(ctx, 0, 0));
  62         aff = isl_aff_val_on_domain(ls, isl_val_int_from_si(ctx, val));
  63         mpa = isl_multi_pw_aff_from_pw_aff(isl_pw_aff_from_aff(aff));
  64
  65         return pet_expr_from_index(mpa);
  66 }
  67
  68 /* Construct an affine expression pet_expr that evaluates
  69  * to the constant 1.
  70  */
  71 static __isl_give pet_expr *universally_true(isl_ctx *ctx)
  72 {
  73         return universally(ctx, 1);
  74 }
  75
  76 /* Construct an affine expression pet_expr that evaluates
  77  * to the constant 0.
  78  */
  79 static __isl_give pet_expr *universally_false(isl_ctx *ctx)
  80 {
  81         return universally(ctx, 0);
  82 }
  83
  84 /* Given an index expression "test_index" for the if condition,
  85  * an index expression "skip_index" for the skip condition and
  86  * scops for the then and else branches, construct a scop for
  87  * computing "skip_index".
  88  *
  89  * The computed scop contains a single statement that essentially does
  90  *
  91  *      skip_index = test_cond ? skip_cond_then : skip_cond_else
  92  *
  93  * If the skip conditions of the then and/or else branch are not affine,
  94  * then they need to be filtered by test_index.
  95  * If they are missing, then this means the skip condition is false.
  96  *
  97  * Since we are constructing a skip condition for the if statement,
  98  * the skip conditions on the then and else branches are removed.
  99  */
 100 static struct pet_scop *extract_skip_if(__isl_take isl_multi_pw_aff *test_index,
 101         __isl_take isl_multi_pw_aff *skip_index,
 102         struct pet_scop *scop_then, struct pet_scop *scop_else, int have_else,
 103         enum pet_skip type, struct pet_state *state)
 104 {
 105         pet_expr *expr_then, *expr_else, *expr, *expr_skip;
 106         struct pet_stmt *stmt;
 107         struct pet_scop *scop;
 108         isl_ctx *ctx;
 109         isl_set *domain;
 110
 111         if (!scop_then)
 112                 goto error;
 113         if (have_else && !scop_else)
 114                 goto error;
 115
 116         ctx = isl_multi_pw_aff_get_ctx(test_index);
 117
 118         if (pet_scop_has_skip(scop_then, type)) {
 119                 expr_then = pet_scop_get_skip_expr(scop_then, type);
 120                 pet_scop_reset_skip(scop_then, type);
 121                 if (!pet_expr_is_affine(expr_then))
 122                         expr_then = pet_expr_filter(expr_then,
 123                                         isl_multi_pw_aff_copy(test_index), 1);
 124         } else
 125                 expr_then = universally_false(ctx);
 126
 127         if (have_else && pet_scop_has_skip(scop_else, type)) {
 128                 expr_else = pet_scop_get_skip_expr(scop_else, type);
 129                 pet_scop_reset_skip(scop_else, type);
 130                 if (!pet_expr_is_affine(expr_else))
 131                         expr_else = pet_expr_filter(expr_else,
 132                                         isl_multi_pw_aff_copy(test_index), 0);
 133         } else
 134                 expr_else = universally_false(ctx);
 135
 136         expr = pet_expr_from_index(test_index);
 137         expr = pet_expr_new_ternary(expr, expr_then, expr_else);
 138         expr_skip = pet_expr_from_index(isl_multi_pw_aff_copy(skip_index));
 139         expr_skip = pet_expr_access_set_write(expr_skip, 1);
 140         expr_skip = pet_expr_access_set_read(expr_skip, 0);
 141         expr = pet_expr_new_binary(1, pet_op_assign, expr_skip, expr);
 142         domain = isl_set_universe(isl_space_set_alloc(ctx, 0, 0));
 143         stmt = pet_stmt_from_pet_expr(domain, &pet_loc_dummy, NULL,
 144                                         state->n_stmt++, expr);
 145
 146         scop = pet_scop_from_pet_stmt(ctx, stmt);
 147         scop = pet_scop_add_boolean_array(scop, skip_index, state->int_size);
 148
 149         return scop;
 150 error:
 151         isl_multi_pw_aff_free(test_index);
 152         isl_multi_pw_aff_free(skip_index);
 153         return NULL;
 154 }
 155
 156 /* Is scop's skip_now condition equal to its skip_later condition?
 157  * In particular, this means that it either has no skip_now condition
 158  * or both a skip_now and a skip_later condition (that are equal to each other).
 159  */
 160 static int skip_equals_skip_later(struct pet_scop *scop)
 161 {
 162         int has_skip_now, has_skip_later;
 163         int equal;
 164         isl_multi_pw_aff *skip_now, *skip_later;
 165
 166         if (!scop)
 167                 return 0;
 168         has_skip_now = pet_scop_has_skip(scop, pet_skip_now);
 169         has_skip_later = pet_scop_has_skip(scop, pet_skip_later);
 170         if (has_skip_now != has_skip_later)
 171                 return 0;
 172         if (!has_skip_now)
 173                 return 1;
 174
 175         skip_now = pet_scop_get_skip(scop, pet_skip_now);
 176         skip_later = pet_scop_get_skip(scop, pet_skip_later);
 177         equal = isl_multi_pw_aff_is_equal(skip_now, skip_later);
 178         isl_multi_pw_aff_free(skip_now);
 179         isl_multi_pw_aff_free(skip_later);
 180
 181         return equal;
 182 }
 183
 184 /* Drop the skip conditions of type pet_skip_later from scop1 and scop2.
 185  */
 186 static void drop_skip_later(struct pet_scop *scop1, struct pet_scop *scop2)
 187 {
 188         pet_scop_reset_skip(scop1, pet_skip_later);
 189         pet_scop_reset_skip(scop2, pet_skip_later);
 190 }
 191
 192 /* Do we need to construct any skip condition?
 193  */
 194 int pet_skip_info_has_skip(struct pet_skip_info *skip)
 195 {
 196         return skip->skip[pet_skip_now] || skip->skip[pet_skip_later];
 197 }
 198
 199 /* Initialize a pet_skip_info_if structure based on the then and else branches
 200  * and based on whether the if condition is affine or not.
 201  */
 202 void pet_skip_info_if_init(struct pet_skip_info *skip, isl_ctx *ctx,
 203         struct pet_scop *scop_then, struct pet_scop *scop_else,
 204         int have_else, int affine)
 205 {
 206         skip->ctx = ctx;
 207         skip->type = have_else ? pet_skip_if_else : pet_skip_if;
 208         skip->u.i.scop_then = scop_then;
 209         skip->u.i.scop_else = scop_else;
 210
 211         skip->skip[pet_skip_now] =
 212             if_need_skip(scop_then, scop_else, have_else, pet_skip_now, affine);
 213         skip->equal = skip->skip[pet_skip_now] &&
 214                 skip_equals_skip_later(scop_then) &&
 215                 (!have_else || skip_equals_skip_later(scop_else));
 216         skip->skip[pet_skip_later] = skip->skip[pet_skip_now] &&
 217                 !skip->equal &&
 218                 if_need_skip(scop_then, scop_else, have_else,
 219                             pet_skip_later, affine);
 220 }
 221
 222 /* If we need to construct a skip condition of the given type,
 223  * then do so now.
 224  *
 225  * "mpa" represents the if condition.
 226  */
 227 static void pet_skip_info_if_extract_type(struct pet_skip_info *skip,
 228         __isl_keep isl_multi_pw_aff *mpa, enum pet_skip type,
 229         struct pet_state *state)
 230 {
 231         isl_space *space;
 232
 233         if (!skip->skip[type])
 234                 return;
 235
 236         space = isl_space_set_alloc(skip->ctx, 0, 0);
 237         skip->index[type] = pet_create_test_index(space, state->n_test++);
 238         skip->scop[type] = extract_skip_if(isl_multi_pw_aff_copy(mpa),
 239                                 isl_multi_pw_aff_copy(skip->index[type]),
 240                                 skip->u.i.scop_then, skip->u.i.scop_else,
 241                                 skip->type == pet_skip_if_else, type, state);
 242 }
 243
 244 /* Construct the required skip conditions, given the if condition "index".
 245  */
 246 void pet_skip_info_if_extract_index(struct pet_skip_info *skip,
 247         __isl_keep isl_multi_pw_aff *index, struct pet_state *state)
 248 {
 249         pet_skip_info_if_extract_type(skip, index, pet_skip_now, state);
 250         pet_skip_info_if_extract_type(skip, index, pet_skip_later, state);
 251         if (skip->equal)
 252                 drop_skip_later(skip->u.i.scop_then, skip->u.i.scop_else);
 253 }
 254
 255 /* Construct the required skip conditions, given the if condition "cond".
 256  */
 257 void pet_skip_info_if_extract_cond(struct pet_skip_info *skip,
 258         __isl_keep isl_pw_aff *cond, struct pet_state *state)
 259 {
 260         isl_multi_pw_aff *test;
 261
 262         if (!skip->skip[pet_skip_now] && !skip->skip[pet_skip_later])
 263                 return;
 264
 265         test = isl_multi_pw_aff_from_pw_aff(isl_pw_aff_copy(cond));
 266         pet_skip_info_if_extract_index(skip, test, state);
 267         isl_multi_pw_aff_free(test);
 268 }
 269
 270 /* Add the computed skip condition of the give type to "main" and
 271  * add the scop for computing the condition at the given offset.
 272  *
 273  * If equal is set, then we only computed a skip condition for pet_skip_now,
 274  * but we also need to set it as main's pet_skip_later.
 275  */
 276 struct pet_scop *pet_skip_info_if_add_type(struct pet_skip_info *skip,
 277         struct pet_scop *main, enum pet_skip type, int offset)
 278 {
 279         if (!skip->skip[type])
 280                 return main;
 281
 282         skip->scop[type] = pet_scop_prefix(skip->scop[type], offset);
 283         main = pet_scop_add_par(skip->ctx, main, skip->scop[type]);
 284         skip->scop[type] = NULL;
 285
 286         if (skip->equal)
 287                 main = pet_scop_set_skip(main, pet_skip_later,
 288                                     isl_multi_pw_aff_copy(skip->index[type]));
 289
 290         main = pet_scop_set_skip(main, type, skip->index[type]);
 291         skip->index[type] = NULL;
 292
 293         return main;
 294 }
 295
 296 /* Add the computed skip conditions to "main" and
 297  * add the scops for computing the conditions at the given offset.
 298  */
 299 struct pet_scop *pet_skip_info_if_add(struct pet_skip_info *skip,
 300         struct pet_scop *scop, int offset)
 301 {
 302         scop = pet_skip_info_if_add_type(skip, scop, pet_skip_now, offset);
 303         scop = pet_skip_info_if_add_type(skip, scop, pet_skip_later, offset);
 304
 305         return scop;
 306 }
 307
 308 /* Do we need to construct a skip condition of the given type
 309  * on a sequence of statements?
 310  *
 311  * There is no need to construct a new skip condition if only
 312  * only of the two statements has a skip condition or if both
 313  * of their skip conditions are affine.
 314  *
 315  * In principle we also don't need a new continuation variable if
 316  * the continuation of scop2 is affine, but then we would need
 317  * to allow more complicated forms of continuations.
 318  */
 319 static int seq_need_skip(struct pet_scop *scop1, struct pet_scop *scop2,
 320         enum pet_skip type)
 321 {
 322         if (!scop1 || !pet_scop_has_skip(scop1, type))
 323                 return 0;
 324         if (!scop2 || !pet_scop_has_skip(scop2, type))
 325                 return 0;
 326         if (pet_scop_has_affine_skip(scop1, type) &&
 327             pet_scop_has_affine_skip(scop2, type))
 328                 return 0;
 329         return 1;
 330 }
 331
 332 /* Construct a scop for computing the skip condition of the given type and
 333  * with index expression "skip_index" for a sequence of two scops "scop1"
 334  * and "scop2".
 335  *
 336  * The computed scop contains a single statement that essentially does
 337  *
 338  *      skip_index = skip_cond_1 ? 1 : skip_cond_2
 339  *
 340  * or, in other words, skip_cond1 || skip_cond2.
 341  * In this expression, skip_cond_2 is filtered to reflect that it is
 342  * only evaluated when skip_cond_1 is false.
 343  *
 344  * The skip condition on scop1 is not removed because it still needs
 345  * to be applied to scop2 when these two scops are combined.
 346  */
 347 static struct pet_scop *extract_skip_seq(
 348         __isl_take isl_multi_pw_aff *skip_index,
 349         struct pet_scop *scop1, struct pet_scop *scop2, enum pet_skip type,
 350         struct pet_state *state)
 351 {
 352         pet_expr *expr1, *expr2, *expr, *expr_skip;
 353         struct pet_stmt *stmt;
 354         struct pet_scop *scop;
 355         isl_ctx *ctx;
 356         isl_set *domain;
 357
 358         if (!scop1 || !scop2)
 359                 goto error;
 360
 361         ctx = isl_multi_pw_aff_get_ctx(skip_index);
 362
 363         expr1 = pet_scop_get_skip_expr(scop1, type);
 364         expr2 = pet_scop_get_skip_expr(scop2, type);
 365         pet_scop_reset_skip(scop2, type);
 366
 367         expr2 = pet_expr_filter(expr2, pet_expr_access_get_index(expr1), 0);
 368
 369         expr = universally_true(ctx);
 370         expr = pet_expr_new_ternary(expr1, expr, expr2);
 371         expr_skip = pet_expr_from_index(isl_multi_pw_aff_copy(skip_index));
 372         expr_skip = pet_expr_access_set_write(expr_skip, 1);
 373         expr_skip = pet_expr_access_set_read(expr_skip, 0);
 374         expr = pet_expr_new_binary(1, pet_op_assign, expr_skip, expr);
 375         domain = isl_set_universe(isl_space_set_alloc(ctx, 0, 0));
 376         stmt = pet_stmt_from_pet_expr(domain, &pet_loc_dummy, NULL,
 377                                         state->n_stmt++, expr);
 378
 379         scop = pet_scop_from_pet_stmt(ctx, stmt);
 380         scop = pet_scop_add_boolean_array(scop, skip_index, state->int_size);
 381
 382         return scop;
 383 error:
 384         isl_multi_pw_aff_free(skip_index);
 385         return NULL;
 386 }
 387
 388 /* Initialize a pet_skip_info_seq structure based on
 389  * on the two statements that are going to be combined.
 390  */
 391 void pet_skip_info_seq_init(struct pet_skip_info *skip, isl_ctx *ctx,
 392         struct pet_scop *scop1, struct pet_scop *scop2)
 393 {
 394         skip->ctx = ctx;
 395         skip->type = pet_skip_seq;
 396         skip->u.s.scop1 = scop1;
 397         skip->u.s.scop2 = scop2;
 398
 399         skip->skip[pet_skip_now] = seq_need_skip(scop1, scop2, pet_skip_now);
 400         skip->equal = skip->skip[pet_skip_now] &&
 401                 skip_equals_skip_later(scop1) && skip_equals_skip_later(scop2);
 402         skip->skip[pet_skip_later] = skip->skip[pet_skip_now] && !skip->equal &&
 403                         seq_need_skip(scop1, scop2, pet_skip_later);
 404 }
 405
 406 /* If we need to construct a skip condition of the given type,
 407  * then do so now.
 408  */
 409 static void pet_skip_info_seq_extract_type(struct pet_skip_info *skip,
 410         enum pet_skip type, struct pet_state *state)
 411 {
 412         isl_space *space;
 413
 414         if (!skip->skip[type])
 415                 return;
 416
 417         space = isl_space_set_alloc(skip->ctx, 0, 0);
 418         skip->index[type] = pet_create_test_index(space, state->n_test++);
 419         skip->scop[type] = extract_skip_seq(
 420                                 isl_multi_pw_aff_copy(skip->index[type]),
 421                                 skip->u.s.scop1, skip->u.s.scop2, type, state);
 422 }
 423
 424 /* Construct the required skip conditions.
 425  */
 426 void pet_skip_info_seq_extract(struct pet_skip_info *skip,
 427         struct pet_state *state)
 428 {
 429         pet_skip_info_seq_extract_type(skip, pet_skip_now, state);
 430         pet_skip_info_seq_extract_type(skip, pet_skip_later, state);
 431         if (skip->equal)
 432                 drop_skip_later(skip->u.s.scop1, skip->u.s.scop2);
 433 }
 434
 435 /* Add the computed skip condition of the given type to "main" and
 436  * add the scop for computing the condition at the given offset (the statement
 437  * number).  Within this offset, the condition is computed at position 1
 438  * to ensure that it is computed after the corresponding statement.
 439  *
 440  * If equal is set, then we only computed a skip condition for pet_skip_now,
 441  * but we also need to set it as main's pet_skip_later.
 442  */
 443 struct pet_scop *pet_skip_info_seq_add_type(struct pet_skip_info *skip,
 444         struct pet_scop *main, enum pet_skip type, int offset)
 445 {
 446         if (!skip->skip[type])
 447                 return main;
 448
 449         skip->scop[type] = pet_scop_prefix(skip->scop[type], 1);
 450         skip->scop[type] = pet_scop_prefix(skip->scop[type], offset);
 451         main = pet_scop_add_par(skip->ctx, main, skip->scop[type]);
 452         skip->scop[type] = NULL;
 453
 454         if (skip->equal)
 455                 main = pet_scop_set_skip(main, pet_skip_later,
 456                                     isl_multi_pw_aff_copy(skip->index[type]));
 457
 458         main = pet_scop_set_skip(main, type, skip->index[type]);
 459         skip->index[type] = NULL;
 460
 461         return main;
 462 }
 463
 464 /* Add the computed skip conditions to "main" and
 465  * add the scops for computing the conditions at the given offset.
 466  */
 467 struct pet_scop *pet_skip_info_seq_add(struct pet_skip_info *skip,
 468         struct pet_scop *scop, int offset)
 469 {
 470         scop = pet_skip_info_seq_add_type(skip, scop, pet_skip_now, offset);
 471         scop = pet_skip_info_seq_add_type(skip, scop, pet_skip_later, offset);
 472
 473         return scop;
 474 }