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, int int_size, int *n_stmt)
 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
 110         if (!scop_then)
 111                 goto error;
 112         if (have_else && !scop_else)
 113                 goto error;
 114
 115         ctx = isl_multi_pw_aff_get_ctx(test_index);
 116
 117         if (pet_scop_has_skip(scop_then, type)) {
 118                 expr_then = pet_scop_get_skip_expr(scop_then, type);
 119                 pet_scop_reset_skip(scop_then, type);
 120                 if (!pet_expr_is_affine(expr_then))
 121                         expr_then = pet_expr_filter(expr_then,
 122                                         isl_multi_pw_aff_copy(test_index), 1);
 123         } else
 124                 expr_then = universally_false(ctx);
 125
 126         if (have_else && pet_scop_has_skip(scop_else, type)) {
 127                 expr_else = pet_scop_get_skip_expr(scop_else, type);
 128                 pet_scop_reset_skip(scop_else, type);
 129                 if (!pet_expr_is_affine(expr_else))
 130                         expr_else = pet_expr_filter(expr_else,
 131                                         isl_multi_pw_aff_copy(test_index), 0);
 132         } else
 133                 expr_else = universally_false(ctx);
 134
 135         expr = pet_expr_from_index(test_index);
 136         expr = pet_expr_new_ternary(expr, expr_then, expr_else);
 137         expr_skip = pet_expr_from_index(isl_multi_pw_aff_copy(skip_index));
 138         expr_skip = pet_expr_access_set_write(expr_skip, 1);
 139         expr_skip = pet_expr_access_set_read(expr_skip, 0);
 140         expr = pet_expr_new_binary(1, pet_op_assign, expr_skip, expr);
 141         stmt = pet_stmt_from_pet_expr(&pet_loc_dummy, NULL, (*n_stmt)++, expr);
 142
 143         scop = pet_scop_from_pet_stmt(ctx, stmt);
 144         scop = pet_scop_add_boolean_array(scop, skip_index, int_size);
 145
 146         return scop;
 147 error:
 148         isl_multi_pw_aff_free(test_index);
 149         isl_multi_pw_aff_free(skip_index);
 150         return NULL;
 151 }
 152
 153 /* Is scop's skip_now condition equal to its skip_later condition?
 154  * In particular, this means that it either has no skip_now condition
 155  * or both a skip_now and a skip_later condition (that are equal to each other).
 156  */
 157 static int skip_equals_skip_later(struct pet_scop *scop)
 158 {
 159         int has_skip_now, has_skip_later;
 160         int equal;
 161         isl_multi_pw_aff *skip_now, *skip_later;
 162
 163         if (!scop)
 164                 return 0;
 165         has_skip_now = pet_scop_has_skip(scop, pet_skip_now);
 166         has_skip_later = pet_scop_has_skip(scop, pet_skip_later);
 167         if (has_skip_now != has_skip_later)
 168                 return 0;
 169         if (!has_skip_now)
 170                 return 1;
 171
 172         skip_now = pet_scop_get_skip(scop, pet_skip_now);
 173         skip_later = pet_scop_get_skip(scop, pet_skip_later);
 174         equal = isl_multi_pw_aff_is_equal(skip_now, skip_later);
 175         isl_multi_pw_aff_free(skip_now);
 176         isl_multi_pw_aff_free(skip_later);
 177
 178         return equal;
 179 }
 180
 181 /* Drop the skip conditions of type pet_skip_later from scop1 and scop2.
 182  */
 183 static void drop_skip_later(struct pet_scop *scop1, struct pet_scop *scop2)
 184 {
 185         pet_scop_reset_skip(scop1, pet_skip_later);
 186         pet_scop_reset_skip(scop2, pet_skip_later);
 187 }
 188
 189 /* Do we need to construct any skip condition?
 190  */
 191 int pet_skip_info_has_skip(struct pet_skip_info *skip)
 192 {
 193         return skip->skip[pet_skip_now] || skip->skip[pet_skip_later];
 194 }
 195
 196 /* Initialize a pet_skip_info_if structure based on the then and else branches
 197  * and based on whether the if condition is affine or not.
 198  */
 199 void pet_skip_info_if_init(struct pet_skip_info *skip, isl_ctx *ctx,
 200         struct pet_scop *scop_then, struct pet_scop *scop_else,
 201         int have_else, int affine)
 202 {
 203         skip->ctx = ctx;
 204         skip->type = have_else ? pet_skip_if_else : pet_skip_if;
 205         skip->u.i.scop_then = scop_then;
 206         skip->u.i.scop_else = scop_else;
 207
 208         skip->skip[pet_skip_now] =
 209             if_need_skip(scop_then, scop_else, have_else, pet_skip_now, affine);
 210         skip->equal = skip->skip[pet_skip_now] &&
 211                 skip_equals_skip_later(scop_then) &&
 212                 (!have_else || skip_equals_skip_later(scop_else));
 213         skip->skip[pet_skip_later] = skip->skip[pet_skip_now] &&
 214                 !skip->equal &&
 215                 if_need_skip(scop_then, scop_else, have_else,
 216                             pet_skip_later, affine);
 217 }
 218
 219 /* If we need to construct a skip condition of the given type,
 220  * then do so now.
 221  *
 222  * "mpa" represents the if condition.
 223  */
 224 static void pet_skip_info_if_extract_type(struct pet_skip_info *skip,
 225         __isl_keep isl_multi_pw_aff *mpa, enum pet_skip type,
 226         int int_size, int *n_stmt, int *n_test)
 227 {
 228         if (!skip->skip[type])
 229                 return;
 230
 231         skip->index[type] = pet_create_test_index(skip->ctx, (*n_test)++);
 232         skip->scop[type] = extract_skip_if(isl_multi_pw_aff_copy(mpa),
 233                                 isl_multi_pw_aff_copy(skip->index[type]),
 234                                 skip->u.i.scop_then, skip->u.i.scop_else,
 235                                 skip->type == pet_skip_if_else, type,
 236                                 int_size, n_stmt);
 237 }
 238
 239 /* Construct the required skip conditions, given the if condition "index".
 240  */
 241 void pet_skip_info_if_extract_index(struct pet_skip_info *skip,
 242         __isl_keep isl_multi_pw_aff *index,
 243         int int_size, int *n_stmt, int *n_test)
 244 {
 245         pet_skip_info_if_extract_type(skip, index, pet_skip_now,
 246                                         int_size, n_stmt, n_test);
 247         pet_skip_info_if_extract_type(skip, index, pet_skip_later,
 248                                         int_size, n_stmt, n_test);
 249         if (skip->equal)
 250                 drop_skip_later(skip->u.i.scop_then, skip->u.i.scop_else);
 251 }
 252
 253 /* Construct the required skip conditions, given the if condition "cond".
 254  */
 255 void pet_skip_info_if_extract_cond(struct pet_skip_info *skip,
 256         __isl_keep isl_pw_aff *cond, int int_size, int *n_stmt, int *n_test)
 257 {
 258         isl_multi_pw_aff *test;
 259
 260         if (!skip->skip[pet_skip_now] && !skip->skip[pet_skip_later])
 261                 return;
 262
 263         test = isl_multi_pw_aff_from_pw_aff(isl_pw_aff_copy(cond));
 264         pet_skip_info_if_extract_index(skip, test, int_size, n_stmt, n_test);
 265         isl_multi_pw_aff_free(test);
 266 }
 267
 268 /* Add the computed skip condition of the give type to "main" and
 269  * add the scop for computing the condition at the given offset.
 270  *
 271  * If equal is set, then we only computed a skip condition for pet_skip_now,
 272  * but we also need to set it as main's pet_skip_later.
 273  */
 274 struct pet_scop *pet_skip_info_if_add_type(struct pet_skip_info *skip,
 275         struct pet_scop *main, enum pet_skip type, int offset)
 276 {
 277         if (!skip->skip[type])
 278                 return main;
 279
 280         skip->scop[type] = pet_scop_prefix(skip->scop[type], offset);
 281         main = pet_scop_add_par(skip->ctx, main, skip->scop[type]);
 282         skip->scop[type] = NULL;
 283
 284         if (skip->equal)
 285                 main = pet_scop_set_skip(main, pet_skip_later,
 286                                     isl_multi_pw_aff_copy(skip->index[type]));
 287
 288         main = pet_scop_set_skip(main, type, skip->index[type]);
 289         skip->index[type] = NULL;
 290
 291         return main;
 292 }
 293
 294 /* Add the computed skip conditions to "main" and
 295  * add the scops for computing the conditions at the given offset.
 296  */
 297 struct pet_scop *pet_skip_info_if_add(struct pet_skip_info *skip,
 298         struct pet_scop *scop, int offset)
 299 {
 300         scop = pet_skip_info_if_add_type(skip, scop, pet_skip_now, offset);
 301         scop = pet_skip_info_if_add_type(skip, scop, pet_skip_later, offset);
 302
 303         return scop;
 304 }
 305
 306 /* Do we need to construct a skip condition of the given type
 307  * on a sequence of statements?
 308  *
 309  * There is no need to construct a new skip condition if only
 310  * only of the two statements has a skip condition or if both
 311  * of their skip conditions are affine.
 312  *
 313  * In principle we also don't need a new continuation variable if
 314  * the continuation of scop2 is affine, but then we would need
 315  * to allow more complicated forms of continuations.
 316  */
 317 static int seq_need_skip(struct pet_scop *scop1, struct pet_scop *scop2,
 318         enum pet_skip type)
 319 {
 320         if (!scop1 || !pet_scop_has_skip(scop1, type))
 321                 return 0;
 322         if (!scop2 || !pet_scop_has_skip(scop2, type))
 323                 return 0;
 324         if (pet_scop_has_affine_skip(scop1, type) &&
 325             pet_scop_has_affine_skip(scop2, type))
 326                 return 0;
 327         return 1;
 328 }
 329
 330 /* Construct a scop for computing the skip condition of the given type and
 331  * with index expression "skip_index" for a sequence of two scops "scop1"
 332  * and "scop2".
 333  *
 334  * The computed scop contains a single statement that essentially does
 335  *
 336  *      skip_index = skip_cond_1 ? 1 : skip_cond_2
 337  *
 338  * or, in other words, skip_cond1 || skip_cond2.
 339  * In this expression, skip_cond_2 is filtered to reflect that it is
 340  * only evaluated when skip_cond_1 is false.
 341  *
 342  * The skip condition on scop1 is not removed because it still needs
 343  * to be applied to scop2 when these two scops are combined.
 344  */
 345 static struct pet_scop *extract_skip_seq(
 346         __isl_take isl_multi_pw_aff *skip_index,
 347         struct pet_scop *scop1, struct pet_scop *scop2, enum pet_skip type,
 348         int int_size, int *n_stmt)
 349 {
 350         pet_expr *expr1, *expr2, *expr, *expr_skip;
 351         struct pet_stmt *stmt;
 352         struct pet_scop *scop;
 353         isl_ctx *ctx;
 354
 355         if (!scop1 || !scop2)
 356                 goto error;
 357
 358         ctx = isl_multi_pw_aff_get_ctx(skip_index);
 359
 360         expr1 = pet_scop_get_skip_expr(scop1, type);
 361         expr2 = pet_scop_get_skip_expr(scop2, type);
 362         pet_scop_reset_skip(scop2, type);
 363
 364         expr2 = pet_expr_filter(expr2, pet_expr_access_get_index(expr1), 0);
 365
 366         expr = universally_true(ctx);
 367         expr = pet_expr_new_ternary(expr1, expr, expr2);
 368         expr_skip = pet_expr_from_index(isl_multi_pw_aff_copy(skip_index));
 369         expr_skip = pet_expr_access_set_write(expr_skip, 1);
 370         expr_skip = pet_expr_access_set_read(expr_skip, 0);
 371         expr = pet_expr_new_binary(1, pet_op_assign, expr_skip, expr);
 372         stmt = pet_stmt_from_pet_expr(&pet_loc_dummy, NULL, (*n_stmt)++, expr);
 373
 374         scop = pet_scop_from_pet_stmt(ctx, stmt);
 375         scop = pet_scop_add_boolean_array(scop, skip_index, int_size);
 376
 377         return scop;
 378 error:
 379         isl_multi_pw_aff_free(skip_index);
 380         return NULL;
 381 }
 382
 383 /* Initialize a pet_skip_info_seq structure based on
 384  * on the two statements that are going to be combined.
 385  */
 386 void pet_skip_info_seq_init(struct pet_skip_info *skip, isl_ctx *ctx,
 387         struct pet_scop *scop1, struct pet_scop *scop2)
 388 {
 389         skip->ctx = ctx;
 390         skip->type = pet_skip_seq;
 391         skip->u.s.scop1 = scop1;
 392         skip->u.s.scop2 = scop2;
 393
 394         skip->skip[pet_skip_now] = seq_need_skip(scop1, scop2, pet_skip_now);
 395         skip->equal = skip->skip[pet_skip_now] &&
 396                 skip_equals_skip_later(scop1) && skip_equals_skip_later(scop2);
 397         skip->skip[pet_skip_later] = skip->skip[pet_skip_now] && !skip->equal &&
 398                         seq_need_skip(scop1, scop2, pet_skip_later);
 399 }
 400
 401 /* If we need to construct a skip condition of the given type,
 402  * then do so now.
 403  */
 404 static void pet_skip_info_seq_extract_type(struct pet_skip_info *skip,
 405         enum pet_skip type, int int_size, int *n_stmt, int *n_test)
 406 {
 407         if (!skip->skip[type])
 408                 return;
 409
 410         skip->index[type] = pet_create_test_index(skip->ctx, (*n_test)++);
 411         skip->scop[type] = extract_skip_seq(
 412                                 isl_multi_pw_aff_copy(skip->index[type]),
 413                                 skip->u.s.scop1, skip->u.s.scop2, type,
 414                                 int_size, n_stmt);
 415 }
 416
 417 /* Construct the required skip conditions.
 418  */
 419 void pet_skip_info_seq_extract(struct pet_skip_info *skip,
 420         int int_size, int *n_stmt, int *n_test)
 421 {
 422         pet_skip_info_seq_extract_type(skip, pet_skip_now,
 423                                         int_size, n_stmt, n_test);
 424         pet_skip_info_seq_extract_type(skip, pet_skip_later,
 425                                         int_size, n_stmt, n_test);
 426         if (skip->equal)
 427                 drop_skip_later(skip->u.s.scop1, skip->u.s.scop2);
 428 }
 429
 430 /* Add the computed skip condition of the given type to "main" and
 431  * add the scop for computing the condition at the given offset (the statement
 432  * number).  Within this offset, the condition is computed at position 1
 433  * to ensure that it is computed after the corresponding statement.
 434  *
 435  * If equal is set, then we only computed a skip condition for pet_skip_now,
 436  * but we also need to set it as main's pet_skip_later.
 437  */
 438 struct pet_scop *pet_skip_info_seq_add_type(struct pet_skip_info *skip,
 439         struct pet_scop *main, enum pet_skip type, int offset)
 440 {
 441         if (!skip->skip[type])
 442                 return main;
 443
 444         skip->scop[type] = pet_scop_prefix(skip->scop[type], 1);
 445         skip->scop[type] = pet_scop_prefix(skip->scop[type], offset);
 446         main = pet_scop_add_par(skip->ctx, main, skip->scop[type]);
 447         skip->scop[type] = NULL;
 448
 449         if (skip->equal)
 450                 main = pet_scop_set_skip(main, pet_skip_later,
 451                                     isl_multi_pw_aff_copy(skip->index[type]));
 452
 453         main = pet_scop_set_skip(main, type, skip->index[type]);
 454         skip->index[type] = NULL;
 455
 456         return main;
 457 }
 458
 459 /* Add the computed skip conditions to "main" and
 460  * add the scops for computing the conditions at the given offset.
 461  */
 462 struct pet_scop *pet_skip_info_seq_add(struct pet_skip_info *skip,
 463         struct pet_scop *scop, int offset)
 464 {
 465         scop = pet_skip_info_seq_add_type(skip, scop, pet_skip_now, offset);
 466         scop = pet_skip_info_seq_add_type(skip, scop, pet_skip_later, offset);
 467
 468         return scop;
 469 }