gcc/tree-vect-generic.c

   1 /* Lower vector operations to scalar operations.
   2    Copyright (C) 2004, 2005, 2006 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify it
   7 under the terms of the GNU General Public License as published by the
   8 Free Software Foundation; either version 2, or (at your option) any
   9 later version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT
  12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14 for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GCC; see the file COPYING.  If not, write to the Free
  18 Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301, USA.  */
  20
  21 #include "config.h"
  22 #include "system.h"
  23 #include "coretypes.h"
  24 #include "tree.h"
  25 #include "tm.h"
  26 #include "rtl.h"
  27 #include "expr.h"
  28 #include "insn-codes.h"
  29 #include "diagnostic.h"
  30 #include "optabs.h"
  31 #include "machmode.h"
  32 #include "langhooks.h"
  33 #include "tree-flow.h"
  34 #include "tree-gimple.h"
  35 #include "tree-iterator.h"
  36 #include "tree-pass.h"
  37 #include "flags.h"
  38 #include "ggc.h"
  39
  40
  41 /* Build a constant of type TYPE, made of VALUE's bits replicated
  42    every TYPE_SIZE (INNER_TYPE) bits to fit TYPE's precision.  */
  43 static tree
  44 build_replicated_const (tree type, tree inner_type, HOST_WIDE_INT value)
  45 {
  46   int width = tree_low_cst (TYPE_SIZE (inner_type), 1);
  47   int n = HOST_BITS_PER_WIDE_INT / width;
  48   unsigned HOST_WIDE_INT low, high, mask;
  49   tree ret;
  50
  51   gcc_assert (n);
  52
  53   if (width == HOST_BITS_PER_WIDE_INT)
  54     low = value;
  55   else
  56     {
  57       mask = ((HOST_WIDE_INT)1 << width) - 1;
  58       low = (unsigned HOST_WIDE_INT) ~0 / mask * (value & mask);
  59     }
  60
  61   if (TYPE_PRECISION (type) < HOST_BITS_PER_WIDE_INT)
  62     low &= ((HOST_WIDE_INT)1 << TYPE_PRECISION (type)) - 1, high = 0;
  63   else if (TYPE_PRECISION (type) == HOST_BITS_PER_WIDE_INT)
  64     high = 0;
  65   else if (TYPE_PRECISION (type) == 2 * HOST_BITS_PER_WIDE_INT)
  66     high = low;
  67   else
  68     gcc_unreachable ();
  69
  70   ret = build_int_cst_wide (type, low, high);
  71   return ret;
  72 }
  73
  74 static GTY(()) tree vector_inner_type;
  75 static GTY(()) tree vector_last_type;
  76 static GTY(()) int vector_last_nunits;
  77
  78 /* Return a suitable vector types made of SUBPARTS units each of mode
  79    "word_mode" (the global variable).  */
  80 static tree
  81 build_word_mode_vector_type (int nunits)
  82 {
  83   if (!vector_inner_type)
  84     vector_inner_type = lang_hooks.types.type_for_mode (word_mode, 1);
  85   else if (vector_last_nunits == nunits)
  86     {
  87       gcc_assert (TREE_CODE (vector_last_type) == VECTOR_TYPE);
  88       return vector_last_type;
  89     }
  90
  91   /* We build a new type, but we canonicalize it nevertheless,
  92      because it still saves some memory.  */
  93   vector_last_nunits = nunits;
  94   vector_last_type = type_hash_canon (nunits,
  95                                       build_vector_type (vector_inner_type,
  96                                                          nunits));
  97   return vector_last_type;
  98 }
  99
 100 typedef tree (*elem_op_func) (block_stmt_iterator *,
 101                               tree, tree, tree, tree, tree, enum tree_code);
 102
 103 static inline tree
 104 tree_vec_extract (block_stmt_iterator *bsi, tree type,
 105                   tree t, tree bitsize, tree bitpos)
 106 {
 107   if (bitpos)
 108     return gimplify_build3 (bsi, BIT_FIELD_REF, type, t, bitsize, bitpos);
 109   else
 110     return gimplify_build1 (bsi, VIEW_CONVERT_EXPR, type, t);
 111 }
 112
 113 static tree
 114 do_unop (block_stmt_iterator *bsi, tree inner_type, tree a,
 115          tree b ATTRIBUTE_UNUSED, tree bitpos, tree bitsize,
 116          enum tree_code code)
 117 {
 118   a = tree_vec_extract (bsi, inner_type, a, bitsize, bitpos);
 119   return gimplify_build1 (bsi, code, inner_type, a);
 120 }
 121
 122 static tree
 123 do_binop (block_stmt_iterator *bsi, tree inner_type, tree a, tree b,
 124           tree bitpos, tree bitsize, enum tree_code code)
 125 {
 126   a = tree_vec_extract (bsi, inner_type, a, bitsize, bitpos);
 127   b = tree_vec_extract (bsi, inner_type, b, bitsize, bitpos);
 128   return gimplify_build2 (bsi, code, inner_type, a, b);
 129 }
 130
 131 /* Expand vector addition to scalars.  This does bit twiddling
 132    in order to increase parallelism:
 133
 134    a + b = (((int) a & 0x7f7f7f7f) + ((int) b & 0x7f7f7f7f)) ^
 135            (a ^ b) & 0x80808080
 136
 137    a - b =  (((int) a | 0x80808080) - ((int) b & 0x7f7f7f7f)) ^
 138             (a ^ ~b) & 0x80808080
 139
 140    -b = (0x80808080 - ((int) b & 0x7f7f7f7f)) ^ (~b & 0x80808080)
 141
 142    This optimization should be done only if 4 vector items or more
 143    fit into a word.  */
 144 static tree
 145 do_plus_minus (block_stmt_iterator *bsi, tree word_type, tree a, tree b,
 146                tree bitpos ATTRIBUTE_UNUSED, tree bitsize ATTRIBUTE_UNUSED,
 147                enum tree_code code)
 148 {
 149   tree inner_type = TREE_TYPE (TREE_TYPE (a));
 150   unsigned HOST_WIDE_INT max;
 151   tree low_bits, high_bits, a_low, b_low, result_low, signs;
 152
 153   max = GET_MODE_MASK (TYPE_MODE (inner_type));
 154   low_bits = build_replicated_const (word_type, inner_type, max >> 1);
 155   high_bits = build_replicated_const (word_type, inner_type, max & ~(max >> 1));
 156
 157   a = tree_vec_extract (bsi, word_type, a, bitsize, bitpos);
 158   b = tree_vec_extract (bsi, word_type, b, bitsize, bitpos);
 159
 160   signs = gimplify_build2 (bsi, BIT_XOR_EXPR, word_type, a, b);
 161   b_low = gimplify_build2 (bsi, BIT_AND_EXPR, word_type, b, low_bits);
 162   if (code == PLUS_EXPR)
 163     a_low = gimplify_build2 (bsi, BIT_AND_EXPR, word_type, a, low_bits);
 164   else
 165     {
 166       a_low = gimplify_build2 (bsi, BIT_IOR_EXPR, word_type, a, high_bits);
 167       signs = gimplify_build1 (bsi, BIT_NOT_EXPR, word_type, signs);
 168     }
 169
 170   signs = gimplify_build2 (bsi, BIT_AND_EXPR, word_type, signs, high_bits);
 171   result_low = gimplify_build2 (bsi, code, word_type, a_low, b_low);
 172   return gimplify_build2 (bsi, BIT_XOR_EXPR, word_type, result_low, signs);
 173 }
 174
 175 static tree
 176 do_negate (block_stmt_iterator *bsi, tree word_type, tree b,
 177            tree unused ATTRIBUTE_UNUSED, tree bitpos ATTRIBUTE_UNUSED,
 178            tree bitsize ATTRIBUTE_UNUSED,
 179            enum tree_code code ATTRIBUTE_UNUSED)
 180 {
 181   tree inner_type = TREE_TYPE (TREE_TYPE (b));
 182   HOST_WIDE_INT max;
 183   tree low_bits, high_bits, b_low, result_low, signs;
 184
 185   max = GET_MODE_MASK (TYPE_MODE (inner_type));
 186   low_bits = build_replicated_const (word_type, inner_type, max >> 1);
 187   high_bits = build_replicated_const (word_type, inner_type, max & ~(max >> 1));
 188
 189   b = tree_vec_extract (bsi, word_type, b, bitsize, bitpos);
 190
 191   b_low = gimplify_build2 (bsi, BIT_AND_EXPR, word_type, b, low_bits);
 192   signs = gimplify_build1 (bsi, BIT_NOT_EXPR, word_type, b);
 193   signs = gimplify_build2 (bsi, BIT_AND_EXPR, word_type, signs, high_bits);
 194   result_low = gimplify_build2 (bsi, MINUS_EXPR, word_type, high_bits, b_low);
 195   return gimplify_build2 (bsi, BIT_XOR_EXPR, word_type, result_low, signs);
 196 }
 197
 198 /* Expand a vector operation to scalars, by using many operations
 199    whose type is the vector type's inner type.  */
 200 static tree
 201 expand_vector_piecewise (block_stmt_iterator *bsi, elem_op_func f,
 202                          tree type, tree inner_type,
 203                          tree a, tree b, enum tree_code code)
 204 {
 205   VEC(constructor_elt,gc) *v;
 206   tree part_width = TYPE_SIZE (inner_type);
 207   tree index = bitsize_int (0);
 208   int nunits = TYPE_VECTOR_SUBPARTS (type);
 209   int delta = tree_low_cst (part_width, 1)
 210               / tree_low_cst (TYPE_SIZE (TREE_TYPE (type)), 1);
 211   int i;
 212
 213   v = VEC_alloc(constructor_elt, gc, (nunits + delta - 1) / delta);
 214   for (i = 0; i < nunits;
 215        i += delta, index = int_const_binop (PLUS_EXPR, index, part_width, 0))
 216     {
 217       tree result = f (bsi, inner_type, a, b, index, part_width, code);
 218       constructor_elt *ce = VEC_quick_push (constructor_elt, v, NULL);
 219       ce->index = NULL_TREE;
 220       ce->value = result;
 221     }
 222
 223   return build_constructor (type, v);
 224 }
 225
 226 /* Expand a vector operation to scalars with the freedom to use
 227    a scalar integer type, or to use a different size for the items
 228    in the vector type.  */
 229 static tree
 230 expand_vector_parallel (block_stmt_iterator *bsi, elem_op_func f, tree type,
 231                         tree a, tree b,
 232                         enum tree_code code)
 233 {
 234   tree result, compute_type;
 235   enum machine_mode mode;
 236   int n_words = tree_low_cst (TYPE_SIZE_UNIT (type), 1) / UNITS_PER_WORD;
 237
 238   /* We have three strategies.  If the type is already correct, just do
 239      the operation an element at a time.  Else, if the vector is wider than
 240      one word, do it a word at a time; finally, if the vector is smaller
 241      than one word, do it as a scalar.  */
 242   if (TYPE_MODE (TREE_TYPE (type)) == word_mode)
 243      return expand_vector_piecewise (bsi, f,
 244                                      type, TREE_TYPE (type),
 245                                      a, b, code);
 246   else if (n_words > 1)
 247     {
 248       tree word_type = build_word_mode_vector_type (n_words);
 249       result = expand_vector_piecewise (bsi, f,
 250                                         word_type, TREE_TYPE (word_type),
 251                                         a, b, code);
 252       result = gimplify_val (bsi, word_type, result);
 253     }
 254   else
 255     {
 256       /* Use a single scalar operation with a mode no wider than word_mode.  */
 257       mode = mode_for_size (tree_low_cst (TYPE_SIZE (type), 1), MODE_INT, 0);
 258       compute_type = lang_hooks.types.type_for_mode (mode, 1);
 259       result = f (bsi, compute_type, a, b, NULL_TREE, NULL_TREE, code);
 260     }
 261
 262   return result;
 263 }
 264
 265 /* Expand a vector operation to scalars; for integer types we can use
 266    special bit twiddling tricks to do the sums a word at a time, using
 267    function F_PARALLEL instead of F.  These tricks are done only if
 268    they can process at least four items, that is, only if the vector
 269    holds at least four items and if a word can hold four items.  */
 270 static tree
 271 expand_vector_addition (block_stmt_iterator *bsi,
 272                         elem_op_func f, elem_op_func f_parallel,
 273                         tree type, tree a, tree b, enum tree_code code)
 274 {
 275   int parts_per_word = UNITS_PER_WORD
 276                        / tree_low_cst (TYPE_SIZE_UNIT (TREE_TYPE (type)), 1);
 277
 278   if (INTEGRAL_TYPE_P (TREE_TYPE (type))
 279       && parts_per_word >= 4
 280       && TYPE_VECTOR_SUBPARTS (type) >= 4)
 281     return expand_vector_parallel (bsi, f_parallel,
 282                                    type, a, b, code);
 283   else
 284     return expand_vector_piecewise (bsi, f,
 285                                     type, TREE_TYPE (type),
 286                                     a, b, code);
 287 }
 288
 289 static tree
 290 expand_vector_operation (block_stmt_iterator *bsi, tree type, tree compute_type,
 291                          tree rhs, enum tree_code code)
 292 {
 293   enum machine_mode compute_mode = TYPE_MODE (compute_type);
 294
 295   /* If the compute mode is not a vector mode (hence we are not decomposing
 296      a BLKmode vector to smaller, hardware-supported vectors), we may want
 297      to expand the operations in parallel.  */
 298   if (GET_MODE_CLASS (compute_mode) != MODE_VECTOR_INT
 299       && GET_MODE_CLASS (compute_mode) != MODE_VECTOR_FLOAT)
 300     switch (code)
 301       {
 302       case PLUS_EXPR:
 303       case MINUS_EXPR:
 304         if (!TYPE_TRAP_SIGNED (type))
 305           return expand_vector_addition (bsi, do_binop, do_plus_minus, type,
 306                                          TREE_OPERAND (rhs, 0),
 307                                          TREE_OPERAND (rhs, 1), code);
 308         break;
 309
 310       case NEGATE_EXPR:
 311         if (!TYPE_TRAP_SIGNED (type))
 312           return expand_vector_addition (bsi, do_unop, do_negate, type,
 313                                          TREE_OPERAND (rhs, 0),
 314                                          NULL_TREE, code);
 315         break;
 316
 317       case BIT_AND_EXPR:
 318       case BIT_IOR_EXPR:
 319       case BIT_XOR_EXPR:
 320         return expand_vector_parallel (bsi, do_binop, type,
 321                                        TREE_OPERAND (rhs, 0),
 322                                        TREE_OPERAND (rhs, 1), code);
 323
 324       case BIT_NOT_EXPR:
 325         return expand_vector_parallel (bsi, do_unop, type,
 326                                        TREE_OPERAND (rhs, 0),
 327                                        NULL_TREE, code);
 328
 329       default:
 330         break;
 331       }
 332
 333   if (TREE_CODE_CLASS (code) == tcc_unary)
 334     return expand_vector_piecewise (bsi, do_unop, type, compute_type,
 335                                     TREE_OPERAND (rhs, 0),
 336                                     NULL_TREE, code);
 337   else
 338     return expand_vector_piecewise (bsi, do_binop, type, compute_type,
 339                                     TREE_OPERAND (rhs, 0),
 340                                     TREE_OPERAND (rhs, 1), code);
 341 }
 342 \f
 343 /* Return a type for the widest vector mode whose components are of mode
 344    INNER_MODE, or NULL_TREE if none is found.  */
 345 static tree
 346 type_for_widest_vector_mode (enum machine_mode inner_mode, optab op)
 347 {
 348   enum machine_mode best_mode = VOIDmode, mode;
 349   int best_nunits = 0;
 350
 351   if (SCALAR_FLOAT_MODE_P (inner_mode))
 352     mode = MIN_MODE_VECTOR_FLOAT;
 353   else
 354     mode = MIN_MODE_VECTOR_INT;
 355
 356   for (; mode != VOIDmode; mode = GET_MODE_WIDER_MODE (mode))
 357     if (GET_MODE_INNER (mode) == inner_mode
 358         && GET_MODE_NUNITS (mode) > best_nunits
 359         && op->handlers[mode].insn_code != CODE_FOR_nothing)
 360       best_mode = mode, best_nunits = GET_MODE_NUNITS (mode);
 361
 362   if (best_mode == VOIDmode)
 363     return NULL_TREE;
 364   else
 365     return lang_hooks.types.type_for_mode (best_mode, 1);
 366 }
 367
 368 /* Process one statement.  If we identify a vector operation, expand it.  */
 369
 370 static void
 371 expand_vector_operations_1 (block_stmt_iterator *bsi)
 372 {
 373   tree stmt = bsi_stmt (*bsi);
 374   tree *p_lhs, *p_rhs, lhs, rhs, type, compute_type;
 375   enum tree_code code;
 376   enum machine_mode compute_mode;
 377   optab op;
 378
 379   switch (TREE_CODE (stmt))
 380     {
 381     case RETURN_EXPR:
 382       stmt = TREE_OPERAND (stmt, 0);
 383       if (!stmt || TREE_CODE (stmt) != MODIFY_EXPR)
 384         return;
 385
 386       /* FALLTHRU */
 387
 388     case MODIFY_EXPR:
 389       p_lhs = &TREE_OPERAND (stmt, 0);
 390       p_rhs = &TREE_OPERAND (stmt, 1);
 391       lhs = *p_lhs;
 392       rhs = *p_rhs;
 393       break;
 394
 395     default:
 396       return;
 397     }
 398
 399   type = TREE_TYPE (rhs);
 400   if (TREE_CODE (type) != VECTOR_TYPE)
 401     return;
 402
 403   code = TREE_CODE (rhs);
 404   if (TREE_CODE_CLASS (code) != tcc_unary
 405       && TREE_CODE_CLASS (code) != tcc_binary)
 406     return;
 407
 408   if (code == NOP_EXPR || code == VIEW_CONVERT_EXPR)
 409     return;
 410
 411   gcc_assert (code != CONVERT_EXPR);
 412   op = optab_for_tree_code (code, type);
 413
 414   /* For widening vector operations, the relevant type is of the arguments,
 415      not the widened result.  */
 416   if (code == WIDEN_SUM_EXPR)
 417     type = TREE_TYPE (TREE_OPERAND (rhs, 0));
 418
 419   /* Optabs will try converting a negation into a subtraction, so
 420      look for it as well.  TODO: negation of floating-point vectors
 421      might be turned into an exclusive OR toggling the sign bit.  */
 422   if (op == NULL
 423       && code == NEGATE_EXPR
 424       && INTEGRAL_TYPE_P (TREE_TYPE (type)))
 425     op = optab_for_tree_code (MINUS_EXPR, type);
 426
 427   /* For very wide vectors, try using a smaller vector mode.  */
 428   compute_type = type;
 429   if (TYPE_MODE (type) == BLKmode && op)
 430     {
 431       tree vector_compute_type
 432         = type_for_widest_vector_mode (TYPE_MODE (TREE_TYPE (type)), op);
 433       if (vector_compute_type != NULL_TREE)
 434         compute_type = vector_compute_type;
 435     }
 436
 437   /* If we are breaking a BLKmode vector into smaller pieces,
 438      type_for_widest_vector_mode has already looked into the optab,
 439      so skip these checks.  */
 440   if (compute_type == type)
 441     {
 442       compute_mode = TYPE_MODE (compute_type);
 443       if ((GET_MODE_CLASS (compute_mode) == MODE_VECTOR_INT
 444            || GET_MODE_CLASS (compute_mode) == MODE_VECTOR_FLOAT)
 445           && op != NULL
 446           && op->handlers[compute_mode].insn_code != CODE_FOR_nothing)
 447         return;
 448       else
 449         /* There is no operation in hardware, so fall back to scalars.  */
 450         compute_type = TREE_TYPE (type);
 451     }
 452
 453   gcc_assert (code != VEC_LSHIFT_EXPR && code != VEC_RSHIFT_EXPR);
 454   rhs = expand_vector_operation (bsi, type, compute_type, rhs, code);
 455   if (lang_hooks.types_compatible_p (TREE_TYPE (lhs), TREE_TYPE (rhs)))
 456     *p_rhs = rhs;
 457   else
 458     *p_rhs = gimplify_build1 (bsi, VIEW_CONVERT_EXPR, TREE_TYPE (lhs), rhs);
 459
 460   mark_stmt_modified (bsi_stmt (*bsi));
 461 }
 462 \f
 463 /* Use this to lower vector operations introduced by the vectorizer,
 464    if it may need the bit-twiddling tricks implemented in this file.  */
 465
 466 static bool
 467 gate_expand_vector_operations (void)
 468 {
 469   return flag_tree_vectorize != 0;
 470 }
 471
 472 static unsigned int
 473 expand_vector_operations (void)
 474 {
 475   block_stmt_iterator bsi;
 476   basic_block bb;
 477
 478   FOR_EACH_BB (bb)
 479     {
 480       for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
 481         {
 482           expand_vector_operations_1 (&bsi);
 483           update_stmt_if_modified (bsi_stmt (bsi));
 484         }
 485     }
 486   return 0;
 487 }
 488
 489 struct tree_opt_pass pass_lower_vector =
 490 {
 491   "veclower",                           /* name */
 492   0,                                    /* gate */
 493   expand_vector_operations,             /* execute */
 494   NULL,                                 /* sub */
 495   NULL,                                 /* next */
 496   0,                                    /* static_pass_number */
 497   0,                                    /* tv_id */
 498   PROP_cfg,                             /* properties_required */
 499   0,                                    /* properties_provided */
 500   0,                                    /* properties_destroyed */
 501   0,                                    /* todo_flags_start */
 502   TODO_dump_func | TODO_ggc_collect
 503     | TODO_verify_stmts,                /* todo_flags_finish */
 504   0                                     /* letter */
 505 };
 506
 507 struct tree_opt_pass pass_lower_vector_ssa =
 508 {
 509   "veclower2",                          /* name */
 510   gate_expand_vector_operations,        /* gate */
 511   expand_vector_operations,             /* execute */
 512   NULL,                                 /* sub */
 513   NULL,                                 /* next */
 514   0,                                    /* static_pass_number */
 515   0,                                    /* tv_id */
 516   PROP_cfg,                             /* properties_required */
 517   0,                                    /* properties_provided */
 518   0,                                    /* properties_destroyed */
 519   0,                                    /* todo_flags_start */
 520   TODO_dump_func | TODO_update_ssa      /* todo_flags_finish */
 521     | TODO_verify_ssa
 522     | TODO_verify_stmts | TODO_verify_flow,
 523   0                                     /* letter */
 524 };
 525
 526 #include "gt-tree-vect-generic.h"