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