1 /* Alias analysis for GNU C 2 Copyright (C) 1997-2019 Free Software Foundation, Inc. 3 Contributed by John Carr (jfc@mit.edu). 4 5 This file is part of GCC. 6 7 GCC is free software; you can redistribute it and/or modify it under 8 the terms of the GNU General Public License as published by the Free 9 Software Foundation; either version 3, or (at your option) any later 10 version. 11 12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY 13 WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 for more details. 16 17 You should have received a copy of the GNU General Public License 18 along with GCC; see the file COPYING3. If not see 19 <http://www.gnu.org/licenses/>. */ 20 21 #include "config.h" 22 #include "system.h" 23 #include "coretypes.h" 24 #include "backend.h" 25 #include "target.h" 26 #include "rtl.h" 27 #include "tree.h" 28 #include "gimple.h" 29 #include "df.h" 30 #include "memmodel.h" 31 #include "tm_p.h" 32 #include "gimple-ssa.h" 33 #include "emit-rtl.h" 34 #include "alias.h" 35 #include "fold-const.h" 36 #include "varasm.h" 37 #include "cselib.h" 38 #include "langhooks.h" 39 #include "cfganal.h" 40 #include "rtl-iter.h" 41 #include "cgraph.h" 42 43 /* The aliasing API provided here solves related but different problems: 44 45 Say there exists (in c) 46 47 struct X { 48 struct Y y1; 49 struct Z z2; 50 } x1, *px1, *px2; 51 52 struct Y y2, *py; 53 struct Z z2, *pz; 54 55 56 py = &x1.y1; 57 px2 = &x1; 58 59 Consider the four questions: 60 61 Can a store to x1 interfere with px2->y1? 62 Can a store to x1 interfere with px2->z2? 63 Can a store to x1 change the value pointed to by with py? 64 Can a store to x1 change the value pointed to by with pz? 65 66 The answer to these questions can be yes, yes, yes, and maybe. 67 68 The first two questions can be answered with a simple examination 69 of the type system. If structure X contains a field of type Y then 70 a store through a pointer to an X can overwrite any field that is 71 contained (recursively) in an X (unless we know that px1 != px2). 72 73 The last two questions can be solved in the same way as the first 74 two questions but this is too conservative. The observation is 75 that in some cases we can know which (if any) fields are addressed 76 and if those addresses are used in bad ways. This analysis may be 77 language specific. In C, arbitrary operations may be applied to 78 pointers. However, there is some indication that this may be too 79 conservative for some C++ types. 80 81 The pass ipa-type-escape does this analysis for the types whose 82 instances do not escape across the compilation boundary. 83 84 Historically in GCC, these two problems were combined and a single 85 data structure that was used to represent the solution to these 86 problems. We now have two similar but different data structures, 87 The data structure to solve the last two questions is similar to 88 the first, but does not contain the fields whose address are never 89 taken. For types that do escape the compilation unit, the data 90 structures will have identical information. 91 */ 92 93 /* The alias sets assigned to MEMs assist the back-end in determining 94 which MEMs can alias which other MEMs. In general, two MEMs in 95 different alias sets cannot alias each other, with one important 96 exception. Consider something like: 97 98 struct S { int i; double d; }; 99 100 a store to an `S' can alias something of either type `int' or type 101 `double'. (However, a store to an `int' cannot alias a `double' 102 and vice versa.) We indicate this via a tree structure that looks 103 like: 104 struct S 105 / \ 106 / \ 107 |/_ _\| 108 int double 109 110 (The arrows are directed and point downwards.) 111 In this situation we say the alias set for `struct S' is the 112 `superset' and that those for `int' and `double' are `subsets'. 113 114 To see whether two alias sets can point to the same memory, we must 115 see if either alias set is a subset of the other. We need not trace 116 past immediate descendants, however, since we propagate all 117 grandchildren up one level. 118 119 Alias set zero is implicitly a superset of all other alias sets. 120 However, this is no actual entry for alias set zero. It is an 121 error to attempt to explicitly construct a subset of zero. */ 122 123 struct alias_set_hash : int_hash <int, INT_MIN, INT_MIN + 1> {}; 124 125 struct GTY(()) alias_set_entry { 126 /* The alias set number, as stored in MEM_ALIAS_SET. */ 127 alias_set_type alias_set; 128 129 /* Nonzero if would have a child of zero: this effectively makes this 130 alias set the same as alias set zero. */ 131 bool has_zero_child; 132 /* Nonzero if alias set corresponds to pointer type itself (i.e. not to 133 aggregate contaiing pointer. 134 This is used for a special case where we need an universal pointer type 135 compatible with all other pointer types. */ 136 bool is_pointer; 137 /* Nonzero if is_pointer or if one of childs have has_pointer set. */ 138 bool has_pointer; 139 140 /* The children of the alias set. These are not just the immediate 141 children, but, in fact, all descendants. So, if we have: 142 143 struct T { struct S s; float f; } 144 145 continuing our example above, the children here will be all of 146 `int', `double', `float', and `struct S'. */ 147 hash_map<alias_set_hash, int> *children; 148 }; 149 150 static int rtx_equal_for_memref_p (const_rtx, const_rtx); 151 static void record_set (rtx, const_rtx, void *); 152 static int base_alias_check (rtx, rtx, rtx, rtx, machine_mode, 153 machine_mode); 154 static rtx find_base_value (rtx); 155 static int mems_in_disjoint_alias_sets_p (const_rtx, const_rtx); 156 static alias_set_entry *get_alias_set_entry (alias_set_type); 157 static tree decl_for_component_ref (tree); 158 static int write_dependence_p (const_rtx, 159 const_rtx, machine_mode, rtx, 160 bool, bool, bool); 161 static int compare_base_symbol_refs (const_rtx, const_rtx); 162 163 static void memory_modified_1 (rtx, const_rtx, void *); 164 165 /* Query statistics for the different low-level disambiguators. 166 A high-level query may trigger multiple of them. */ 167 168 static struct { 169 unsigned long long num_alias_zero; 170 unsigned long long num_same_alias_set; 171 unsigned long long num_same_objects; 172 unsigned long long num_volatile; 173 unsigned long long num_dag; 174 unsigned long long num_universal; 175 unsigned long long num_disambiguated; 176 } alias_stats; 177 178 179 /* Set up all info needed to perform alias analysis on memory references. */ 180 181 /* Returns the size in bytes of the mode of X. */ 182 #define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X))) 183 184 /* Cap the number of passes we make over the insns propagating alias 185 information through set chains. 186 ??? 10 is a completely arbitrary choice. This should be based on the 187 maximum loop depth in the CFG, but we do not have this information 188 available (even if current_loops _is_ available). */ 189 #define MAX_ALIAS_LOOP_PASSES 10 190 191 /* reg_base_value[N] gives an address to which register N is related. 192 If all sets after the first add or subtract to the current value 193 or otherwise modify it so it does not point to a different top level 194 object, reg_base_value[N] is equal to the address part of the source 195 of the first set. 196 197 A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF. ADDRESS 198 expressions represent three types of base: 199 200 1. incoming arguments. There is just one ADDRESS to represent all 201 arguments, since we do not know at this level whether accesses 202 based on different arguments can alias. The ADDRESS has id 0. 203 204 2. stack_pointer_rtx, frame_pointer_rtx, hard_frame_pointer_rtx 205 (if distinct from frame_pointer_rtx) and arg_pointer_rtx. 206 Each of these rtxes has a separate ADDRESS associated with it, 207 each with a negative id. 208 209 GCC is (and is required to be) precise in which register it 210 chooses to access a particular region of stack. We can therefore 211 assume that accesses based on one of these rtxes do not alias 212 accesses based on another of these rtxes. 213 214 3. bases that are derived from malloc()ed memory (REG_NOALIAS). 215 Each such piece of memory has a separate ADDRESS associated 216 with it, each with an id greater than 0. 217 218 Accesses based on one ADDRESS do not alias accesses based on other 219 ADDRESSes. Accesses based on ADDRESSes in groups (2) and (3) do not 220 alias globals either; the ADDRESSes have Pmode to indicate this. 221 The ADDRESS in group (1) _may_ alias globals; it has VOIDmode to 222 indicate this. */ 223 224 static GTY(()) vec<rtx, va_gc> *reg_base_value; 225 static rtx *new_reg_base_value; 226 227 /* The single VOIDmode ADDRESS that represents all argument bases. 228 It has id 0. */ 229 static GTY(()) rtx arg_base_value; 230 231 /* Used to allocate unique ids to each REG_NOALIAS ADDRESS. */ 232 static int unique_id; 233 234 /* We preserve the copy of old array around to avoid amount of garbage 235 produced. About 8% of garbage produced were attributed to this 236 array. */ 237 static GTY((deletable)) vec<rtx, va_gc> *old_reg_base_value; 238 239 /* Values of XINT (address, 0) of Pmode ADDRESS rtxes for special 240 registers. */ 241 #define UNIQUE_BASE_VALUE_SP -1 242 #define UNIQUE_BASE_VALUE_ARGP -2 243 #define UNIQUE_BASE_VALUE_FP -3 244 #define UNIQUE_BASE_VALUE_HFP -4 245 246 #define static_reg_base_value \ 247 (this_target_rtl->x_static_reg_base_value) 248 249 #define REG_BASE_VALUE(X) \ 250 (REGNO (X) < vec_safe_length (reg_base_value) \ 251 ? (*reg_base_value)[REGNO (X)] : 0) 252 253 /* Vector indexed by N giving the initial (unchanging) value known for 254 pseudo-register N. This vector is initialized in init_alias_analysis, 255 and does not change until end_alias_analysis is called. */ 256 static GTY(()) vec<rtx, va_gc> *reg_known_value; 257 258 /* Vector recording for each reg_known_value whether it is due to a 259 REG_EQUIV note. Future passes (viz., reload) may replace the 260 pseudo with the equivalent expression and so we account for the 261 dependences that would be introduced if that happens. 262 263 The REG_EQUIV notes created in assign_parms may mention the arg 264 pointer, and there are explicit insns in the RTL that modify the 265 arg pointer. Thus we must ensure that such insns don't get 266 scheduled across each other because that would invalidate the 267 REG_EQUIV notes. One could argue that the REG_EQUIV notes are 268 wrong, but solving the problem in the scheduler will likely give 269 better code, so we do it here. */ 270 static sbitmap reg_known_equiv_p; 271 272 /* True when scanning insns from the start of the rtl to the 273 NOTE_INSN_FUNCTION_BEG note. */ 274 static bool copying_arguments; 275 276 277 /* The splay-tree used to store the various alias set entries. */ 278 static GTY (()) vec<alias_set_entry *, va_gc> *alias_sets; 279 280 /* Build a decomposed reference object for querying the alias-oracle 281 from the MEM rtx and store it in *REF. 282 Returns false if MEM is not suitable for the alias-oracle. */ 283 284 static bool 285 ao_ref_from_mem (ao_ref *ref, const_rtx mem) 286 { 287 tree expr = MEM_EXPR (mem); 288 tree base; 289 290 if (!expr) 291 return false; 292 293 ao_ref_init (ref, expr); 294 295 /* Get the base of the reference and see if we have to reject or 296 adjust it. */ 297 base = ao_ref_base (ref); 298 if (base == NULL_TREE) 299 return false; 300 301 /* The tree oracle doesn't like bases that are neither decls 302 nor indirect references of SSA names. */ 303 if (!(DECL_P (base) 304 || (TREE_CODE (base) == MEM_REF 305 && TREE_CODE (TREE_OPERAND (base, 0)) == SSA_NAME) 306 || (TREE_CODE (base) == TARGET_MEM_REF 307 && TREE_CODE (TMR_BASE (base)) == SSA_NAME))) 308 return false; 309 310 /* If this is a reference based on a partitioned decl replace the 311 base with a MEM_REF of the pointer representative we 312 created during stack slot partitioning. */ 313 if (VAR_P (base) 314 && ! is_global_var (base) 315 && cfun->gimple_df->decls_to_pointers != NULL) 316 { 317 tree *namep = cfun->gimple_df->decls_to_pointers->get (base); 318 if (namep) 319 ref->base = build_simple_mem_ref (*namep); 320 } 321 322 ref->ref_alias_set = MEM_ALIAS_SET (mem); 323 324 /* If MEM_OFFSET or MEM_SIZE are unknown what we got from MEM_EXPR 325 is conservative, so trust it. */ 326 if (!MEM_OFFSET_KNOWN_P (mem) 327 || !MEM_SIZE_KNOWN_P (mem)) 328 return true; 329 330 /* If MEM_OFFSET/MEM_SIZE get us outside of ref->offset/ref->max_size 331 drop ref->ref. */ 332 if (maybe_lt (MEM_OFFSET (mem), 0) 333 || (ref->max_size_known_p () 334 && maybe_gt ((MEM_OFFSET (mem) + MEM_SIZE (mem)) * BITS_PER_UNIT, 335 ref->max_size))) 336 ref->ref = NULL_TREE; 337 338 /* Refine size and offset we got from analyzing MEM_EXPR by using 339 MEM_SIZE and MEM_OFFSET. */ 340 341 ref->offset += MEM_OFFSET (mem) * BITS_PER_UNIT; 342 ref->size = MEM_SIZE (mem) * BITS_PER_UNIT; 343 344 /* The MEM may extend into adjacent fields, so adjust max_size if 345 necessary. */ 346 if (ref->max_size_known_p ()) 347 ref->max_size = upper_bound (ref->max_size, ref->size); 348 349 /* If MEM_OFFSET and MEM_SIZE might get us outside of the base object of 350 the MEM_EXPR punt. This happens for STRICT_ALIGNMENT targets a lot. */ 351 if (MEM_EXPR (mem) != get_spill_slot_decl (false) 352 && (maybe_lt (ref->offset, 0) 353 || (DECL_P (ref->base) 354 && (DECL_SIZE (ref->base) == NULL_TREE 355 || !poly_int_tree_p (DECL_SIZE (ref->base)) 356 || maybe_lt (wi::to_poly_offset (DECL_SIZE (ref->base)), 357 ref->offset + ref->size))))) 358 return false; 359 360 return true; 361 } 362 363 /* Query the alias-oracle on whether the two memory rtx X and MEM may 364 alias. If TBAA_P is set also apply TBAA. Returns true if the 365 two rtxen may alias, false otherwise. */ 366 367 static bool 368 rtx_refs_may_alias_p (const_rtx x, const_rtx mem, bool tbaa_p) 369 { 370 ao_ref ref1, ref2; 371 372 if (!ao_ref_from_mem (&ref1, x) 373 || !ao_ref_from_mem (&ref2, mem)) 374 return true; 375 376 return refs_may_alias_p_1 (&ref1, &ref2, 377 tbaa_p 378 && MEM_ALIAS_SET (x) != 0 379 && MEM_ALIAS_SET (mem) != 0); 380 } 381 382 /* Returns a pointer to the alias set entry for ALIAS_SET, if there is 383 such an entry, or NULL otherwise. */ 384 385 static inline alias_set_entry * 386 get_alias_set_entry (alias_set_type alias_set) 387 { 388 return (*alias_sets)[alias_set]; 389 } 390 391 /* Returns nonzero if the alias sets for MEM1 and MEM2 are such that 392 the two MEMs cannot alias each other. */ 393 394 static inline int 395 mems_in_disjoint_alias_sets_p (const_rtx mem1, const_rtx mem2) 396 { 397 return (flag_strict_aliasing 398 && ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1), 399 MEM_ALIAS_SET (mem2))); 400 } 401 402 /* Return true if the first alias set is a subset of the second. */ 403 404 bool 405 alias_set_subset_of (alias_set_type set1, alias_set_type set2) 406 { 407 alias_set_entry *ase2; 408 409 /* Disable TBAA oracle with !flag_strict_aliasing. */ 410 if (!flag_strict_aliasing) 411 return true; 412 413 /* Everything is a subset of the "aliases everything" set. */ 414 if (set2 == 0) 415 return true; 416 417 /* Check if set1 is a subset of set2. */ 418 ase2 = get_alias_set_entry (set2); 419 if (ase2 != 0 420 && (ase2->has_zero_child 421 || (ase2->children && ase2->children->get (set1)))) 422 return true; 423 424 /* As a special case we consider alias set of "void *" to be both subset 425 and superset of every alias set of a pointer. This extra symmetry does 426 not matter for alias_sets_conflict_p but it makes aliasing_component_refs_p 427 to return true on the following testcase: 428 429 void *ptr; 430 char **ptr2=(char **)&ptr; 431 *ptr2 = ... 432 433 Additionally if a set contains universal pointer, we consider every pointer 434 to be a subset of it, but we do not represent this explicitely - doing so 435 would require us to update transitive closure each time we introduce new 436 pointer type. This makes aliasing_component_refs_p to return true 437 on the following testcase: 438 439 struct a {void *ptr;} 440 char **ptr = (char **)&a.ptr; 441 ptr = ... 442 443 This makes void * truly universal pointer type. See pointer handling in 444 get_alias_set for more details. */ 445 if (ase2 && ase2->has_pointer) 446 { 447 alias_set_entry *ase1 = get_alias_set_entry (set1); 448 449 if (ase1 && ase1->is_pointer) 450 { 451 alias_set_type voidptr_set = TYPE_ALIAS_SET (ptr_type_node); 452 /* If one is ptr_type_node and other is pointer, then we consider 453 them subset of each other. */ 454 if (set1 == voidptr_set || set2 == voidptr_set) 455 return true; 456 /* If SET2 contains universal pointer's alias set, then we consdier 457 every (non-universal) pointer. */ 458 if (ase2->children && set1 != voidptr_set 459 && ase2->children->get (voidptr_set)) 460 return true; 461 } 462 } 463 return false; 464 } 465 466 /* Return 1 if the two specified alias sets may conflict. */ 467 468 int 469 alias_sets_conflict_p (alias_set_type set1, alias_set_type set2) 470 { 471 alias_set_entry *ase1; 472 alias_set_entry *ase2; 473 474 /* The easy case. */ 475 if (alias_sets_must_conflict_p (set1, set2)) 476 return 1; 477 478 /* See if the first alias set is a subset of the second. */ 479 ase1 = get_alias_set_entry (set1); 480 if (ase1 != 0 481 && ase1->children && ase1->children->get (set2)) 482 { 483 ++alias_stats.num_dag; 484 return 1; 485 } 486 487 /* Now do the same, but with the alias sets reversed. */ 488 ase2 = get_alias_set_entry (set2); 489 if (ase2 != 0 490 && ase2->children && ase2->children->get (set1)) 491 { 492 ++alias_stats.num_dag; 493 return 1; 494 } 495 496 /* We want void * to be compatible with any other pointer without 497 really dropping it to alias set 0. Doing so would make it 498 compatible with all non-pointer types too. 499 500 This is not strictly necessary by the C/C++ language 501 standards, but avoids common type punning mistakes. In 502 addition to that, we need the existence of such universal 503 pointer to implement Fortran's C_PTR type (which is defined as 504 type compatible with all C pointers). */ 505 if (ase1 && ase2 && ase1->has_pointer && ase2->has_pointer) 506 { 507 alias_set_type voidptr_set = TYPE_ALIAS_SET (ptr_type_node); 508 509 /* If one of the sets corresponds to universal pointer, 510 we consider it to conflict with anything that is 511 or contains pointer. */ 512 if (set1 == voidptr_set || set2 == voidptr_set) 513 { 514 ++alias_stats.num_universal; 515 return true; 516 } 517 /* If one of sets is (non-universal) pointer and the other 518 contains universal pointer, we also get conflict. */ 519 if (ase1->is_pointer && set2 != voidptr_set 520 && ase2->children && ase2->children->get (voidptr_set)) 521 { 522 ++alias_stats.num_universal; 523 return true; 524 } 525 if (ase2->is_pointer && set1 != voidptr_set 526 && ase1->children && ase1->children->get (voidptr_set)) 527 { 528 ++alias_stats.num_universal; 529 return true; 530 } 531 } 532 533 ++alias_stats.num_disambiguated; 534 535 /* The two alias sets are distinct and neither one is the 536 child of the other. Therefore, they cannot conflict. */ 537 return 0; 538 } 539 540 /* Return 1 if the two specified alias sets will always conflict. */ 541 542 int 543 alias_sets_must_conflict_p (alias_set_type set1, alias_set_type set2) 544 { 545 /* Disable TBAA oracle with !flag_strict_aliasing. */ 546 if (!flag_strict_aliasing) 547 return 1; 548 if (set1 == 0 || set2 == 0) 549 { 550 ++alias_stats.num_alias_zero; 551 return 1; 552 } 553 if (set1 == set2) 554 { 555 ++alias_stats.num_same_alias_set; 556 return 1; 557 } 558 559 return 0; 560 } 561 562 /* Return 1 if any MEM object of type T1 will always conflict (using the 563 dependency routines in this file) with any MEM object of type T2. 564 This is used when allocating temporary storage. If T1 and/or T2 are 565 NULL_TREE, it means we know nothing about the storage. */ 566 567 int 568 objects_must_conflict_p (tree t1, tree t2) 569 { 570 alias_set_type set1, set2; 571 572 /* If neither has a type specified, we don't know if they'll conflict 573 because we may be using them to store objects of various types, for 574 example the argument and local variables areas of inlined functions. */ 575 if (t1 == 0 && t2 == 0) 576 return 0; 577 578 /* If they are the same type, they must conflict. */ 579 if (t1 == t2) 580 { 581 ++alias_stats.num_same_objects; 582 return 1; 583 } 584 /* Likewise if both are volatile. */ 585 if (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2)) 586 { 587 ++alias_stats.num_volatile; 588 return 1; 589 } 590 591 set1 = t1 ? get_alias_set (t1) : 0; 592 set2 = t2 ? get_alias_set (t2) : 0; 593 594 /* We can't use alias_sets_conflict_p because we must make sure 595 that every subtype of t1 will conflict with every subtype of 596 t2 for which a pair of subobjects of these respective subtypes 597 overlaps on the stack. */ 598 return alias_sets_must_conflict_p (set1, set2); 599 } 600 601 /* Return the outermost parent of component present in the chain of 602 component references handled by get_inner_reference in T with the 603 following property: 604 - the component is non-addressable 605 or NULL_TREE if no such parent exists. In the former cases, the alias 606 set of this parent is the alias set that must be used for T itself. */ 607 608 tree 609 component_uses_parent_alias_set_from (const_tree t) 610 { 611 const_tree found = NULL_TREE; 612 613 while (handled_component_p (t)) 614 { 615 switch (TREE_CODE (t)) 616 { 617 case COMPONENT_REF: 618 if (DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1))) 619 found = t; 620 /* Permit type-punning when accessing a union, provided the access 621 is directly through the union. For example, this code does not 622 permit taking the address of a union member and then storing 623 through it. Even the type-punning allowed here is a GCC 624 extension, albeit a common and useful one; the C standard says 625 that such accesses have implementation-defined behavior. */ 626 else if (TREE_CODE (TREE_TYPE (TREE_OPERAND (t, 0))) == UNION_TYPE) 627 found = t; 628 break; 629 630 case ARRAY_REF: 631 case ARRAY_RANGE_REF: 632 if (TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0)))) 633 found = t; 634 break; 635 636 case REALPART_EXPR: 637 case IMAGPART_EXPR: 638 break; 639 640 case BIT_FIELD_REF: 641 case VIEW_CONVERT_EXPR: 642 /* Bitfields and casts are never addressable. */ 643 found = t; 644 break; 645 646 default: 647 gcc_unreachable (); 648 } 649 650 t = TREE_OPERAND (t, 0); 651 } 652 653 if (found) 654 return TREE_OPERAND (found, 0); 655 656 return NULL_TREE; 657 } 658 659 660 /* Return whether the pointer-type T effective for aliasing may 661 access everything and thus the reference has to be assigned 662 alias-set zero. */ 663 664 static bool 665 ref_all_alias_ptr_type_p (const_tree t) 666 { 667 return (TREE_CODE (TREE_TYPE (t)) == VOID_TYPE 668 || TYPE_REF_CAN_ALIAS_ALL (t)); 669 } 670 671 /* Return the alias set for the memory pointed to by T, which may be 672 either a type or an expression. Return -1 if there is nothing 673 special about dereferencing T. */ 674 675 static alias_set_type 676 get_deref_alias_set_1 (tree t) 677 { 678 /* All we care about is the type. */ 679 if (! TYPE_P (t)) 680 t = TREE_TYPE (t); 681 682 /* If we have an INDIRECT_REF via a void pointer, we don't 683 know anything about what that might alias. Likewise if the 684 pointer is marked that way. */ 685 if (ref_all_alias_ptr_type_p (t)) 686 return 0; 687 688 return -1; 689 } 690 691 /* Return the alias set for the memory pointed to by T, which may be 692 either a type or an expression. */ 693 694 alias_set_type 695 get_deref_alias_set (tree t) 696 { 697 /* If we're not doing any alias analysis, just assume everything 698 aliases everything else. */ 699 if (!flag_strict_aliasing) 700 return 0; 701 702 alias_set_type set = get_deref_alias_set_1 (t); 703 704 /* Fall back to the alias-set of the pointed-to type. */ 705 if (set == -1) 706 { 707 if (! TYPE_P (t)) 708 t = TREE_TYPE (t); 709 set = get_alias_set (TREE_TYPE (t)); 710 } 711 712 return set; 713 } 714 715 /* Return the pointer-type relevant for TBAA purposes from the 716 memory reference tree *T or NULL_TREE in which case *T is 717 adjusted to point to the outermost component reference that 718 can be used for assigning an alias set. */ 719 720 static tree 721 reference_alias_ptr_type_1 (tree *t) 722 { 723 tree inner; 724 725 /* Get the base object of the reference. */ 726 inner = *t; 727 while (handled_component_p (inner)) 728 { 729 /* If there is a VIEW_CONVERT_EXPR in the chain we cannot use 730 the type of any component references that wrap it to 731 determine the alias-set. */ 732 if (TREE_CODE (inner) == VIEW_CONVERT_EXPR) 733 *t = TREE_OPERAND (inner, 0); 734 inner = TREE_OPERAND (inner, 0); 735 } 736 737 /* Handle pointer dereferences here, they can override the 738 alias-set. */ 739 if (INDIRECT_REF_P (inner) 740 && ref_all_alias_ptr_type_p (TREE_TYPE (TREE_OPERAND (inner, 0)))) 741 return TREE_TYPE (TREE_OPERAND (inner, 0)); 742 else if (TREE_CODE (inner) == TARGET_MEM_REF) 743 return TREE_TYPE (TMR_OFFSET (inner)); 744 else if (TREE_CODE (inner) == MEM_REF 745 && ref_all_alias_ptr_type_p (TREE_TYPE (TREE_OPERAND (inner, 1)))) 746 return TREE_TYPE (TREE_OPERAND (inner, 1)); 747 748 /* If the innermost reference is a MEM_REF that has a 749 conversion embedded treat it like a VIEW_CONVERT_EXPR above, 750 using the memory access type for determining the alias-set. */ 751 if (TREE_CODE (inner) == MEM_REF 752 && (TYPE_MAIN_VARIANT (TREE_TYPE (inner)) 753 != TYPE_MAIN_VARIANT 754 (TREE_TYPE (TREE_TYPE (TREE_OPERAND (inner, 1)))))) 755 return TREE_TYPE (TREE_OPERAND (inner, 1)); 756 757 /* Otherwise, pick up the outermost object that we could have 758 a pointer to. */ 759 tree tem = component_uses_parent_alias_set_from (*t); 760 if (tem) 761 *t = tem; 762 763 return NULL_TREE; 764 } 765 766 /* Return the pointer-type relevant for TBAA purposes from the 767 gimple memory reference tree T. This is the type to be used for 768 the offset operand of MEM_REF or TARGET_MEM_REF replacements of T 769 and guarantees that get_alias_set will return the same alias 770 set for T and the replacement. */ 771 772 tree 773 reference_alias_ptr_type (tree t) 774 { 775 /* If the frontend assigns this alias-set zero, preserve that. */ 776 if (lang_hooks.get_alias_set (t) == 0) 777 return ptr_type_node; 778 779 tree ptype = reference_alias_ptr_type_1 (&t); 780 /* If there is a given pointer type for aliasing purposes, return it. */ 781 if (ptype != NULL_TREE) 782 return ptype; 783 784 /* Otherwise build one from the outermost component reference we 785 may use. */ 786 if (TREE_CODE (t) == MEM_REF 787 || TREE_CODE (t) == TARGET_MEM_REF) 788 return TREE_TYPE (TREE_OPERAND (t, 1)); 789 else 790 return build_pointer_type (TYPE_MAIN_VARIANT (TREE_TYPE (t))); 791 } 792 793 /* Return whether the pointer-types T1 and T2 used to determine 794 two alias sets of two references will yield the same answer 795 from get_deref_alias_set. */ 796 797 bool 798 alias_ptr_types_compatible_p (tree t1, tree t2) 799 { 800 if (TYPE_MAIN_VARIANT (t1) == TYPE_MAIN_VARIANT (t2)) 801 return true; 802 803 if (ref_all_alias_ptr_type_p (t1) 804 || ref_all_alias_ptr_type_p (t2)) 805 return false; 806 807 return (TYPE_MAIN_VARIANT (TREE_TYPE (t1)) 808 == TYPE_MAIN_VARIANT (TREE_TYPE (t2))); 809 } 810 811 /* Create emptry alias set entry. */ 812 813 alias_set_entry * 814 init_alias_set_entry (alias_set_type set) 815 { 816 alias_set_entry *ase = ggc_alloc<alias_set_entry> (); 817 ase->alias_set = set; 818 ase->children = NULL; 819 ase->has_zero_child = false; 820 ase->is_pointer = false; 821 ase->has_pointer = false; 822 gcc_checking_assert (!get_alias_set_entry (set)); 823 (*alias_sets)[set] = ase; 824 return ase; 825 } 826 827 /* Return the alias set for T, which may be either a type or an 828 expression. Call language-specific routine for help, if needed. */ 829 830 alias_set_type 831 get_alias_set (tree t) 832 { 833 alias_set_type set; 834 835 /* We cannot give up with -fno-strict-aliasing because we need to build 836 proper type representation for possible functions which are build with 837 -fstrict-aliasing. */ 838 839 /* return 0 if this or its type is an error. */ 840 if (t == error_mark_node 841 || (! TYPE_P (t) 842 && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node))) 843 return 0; 844 845 /* We can be passed either an expression or a type. This and the 846 language-specific routine may make mutually-recursive calls to each other 847 to figure out what to do. At each juncture, we see if this is a tree 848 that the language may need to handle specially. First handle things that 849 aren't types. */ 850 if (! TYPE_P (t)) 851 { 852 /* Give the language a chance to do something with this tree 853 before we look at it. */ 854 STRIP_NOPS (t); 855 set = lang_hooks.get_alias_set (t); 856 if (set != -1) 857 return set; 858 859 /* Get the alias pointer-type to use or the outermost object 860 that we could have a pointer to. */ 861 tree ptype = reference_alias_ptr_type_1 (&t); 862 if (ptype != NULL) 863 return get_deref_alias_set (ptype); 864 865 /* If we've already determined the alias set for a decl, just return 866 it. This is necessary for C++ anonymous unions, whose component 867 variables don't look like union members (boo!). */ 868 if (VAR_P (t) 869 && DECL_RTL_SET_P (t) && MEM_P (DECL_RTL (t))) 870 return MEM_ALIAS_SET (DECL_RTL (t)); 871 872 /* Now all we care about is the type. */ 873 t = TREE_TYPE (t); 874 } 875 876 /* Variant qualifiers don't affect the alias set, so get the main 877 variant. */ 878 t = TYPE_MAIN_VARIANT (t); 879 880 if (AGGREGATE_TYPE_P (t) 881 && TYPE_TYPELESS_STORAGE (t)) 882 return 0; 883 884 /* Always use the canonical type as well. If this is a type that 885 requires structural comparisons to identify compatible types 886 use alias set zero. */ 887 if (TYPE_STRUCTURAL_EQUALITY_P (t)) 888 { 889 /* Allow the language to specify another alias set for this 890 type. */ 891 set = lang_hooks.get_alias_set (t); 892 if (set != -1) 893 return set; 894 /* Handle structure type equality for pointer types, arrays and vectors. 895 This is easy to do, because the code bellow ignore canonical types on 896 these anyway. This is important for LTO, where TYPE_CANONICAL for 897 pointers cannot be meaningfuly computed by the frotnend. */ 898 if (canonical_type_used_p (t)) 899 { 900 /* In LTO we set canonical types for all types where it makes 901 sense to do so. Double check we did not miss some type. */ 902 gcc_checking_assert (!in_lto_p || !type_with_alias_set_p (t)); 903 return 0; 904 } 905 } 906 else 907 { 908 t = TYPE_CANONICAL (t); 909 gcc_checking_assert (!TYPE_STRUCTURAL_EQUALITY_P (t)); 910 } 911 912 /* If this is a type with a known alias set, return it. */ 913 gcc_checking_assert (t == TYPE_MAIN_VARIANT (t)); 914 if (TYPE_ALIAS_SET_KNOWN_P (t)) 915 return TYPE_ALIAS_SET (t); 916 917 /* We don't want to set TYPE_ALIAS_SET for incomplete types. */ 918 if (!COMPLETE_TYPE_P (t)) 919 { 920 /* For arrays with unknown size the conservative answer is the 921 alias set of the element type. */ 922 if (TREE_CODE (t) == ARRAY_TYPE) 923 return get_alias_set (TREE_TYPE (t)); 924 925 /* But return zero as a conservative answer for incomplete types. */ 926 return 0; 927 } 928 929 /* See if the language has special handling for this type. */ 930 set = lang_hooks.get_alias_set (t); 931 if (set != -1) 932 return set; 933 934 /* There are no objects of FUNCTION_TYPE, so there's no point in 935 using up an alias set for them. (There are, of course, pointers 936 and references to functions, but that's different.) */ 937 else if (TREE_CODE (t) == FUNCTION_TYPE || TREE_CODE (t) == METHOD_TYPE) 938 set = 0; 939 940 /* Unless the language specifies otherwise, let vector types alias 941 their components. This avoids some nasty type punning issues in 942 normal usage. And indeed lets vectors be treated more like an 943 array slice. */ 944 else if (TREE_CODE (t) == VECTOR_TYPE) 945 set = get_alias_set (TREE_TYPE (t)); 946 947 /* Unless the language specifies otherwise, treat array types the 948 same as their components. This avoids the asymmetry we get 949 through recording the components. Consider accessing a 950 character(kind=1) through a reference to a character(kind=1)[1:1]. 951 Or consider if we want to assign integer(kind=4)[0:D.1387] and 952 integer(kind=4)[4] the same alias set or not. 953 Just be pragmatic here and make sure the array and its element 954 type get the same alias set assigned. */ 955 else if (TREE_CODE (t) == ARRAY_TYPE 956 && (!TYPE_NONALIASED_COMPONENT (t) 957 || TYPE_STRUCTURAL_EQUALITY_P (t))) 958 set = get_alias_set (TREE_TYPE (t)); 959 960 /* From the former common C and C++ langhook implementation: 961 962 Unfortunately, there is no canonical form of a pointer type. 963 In particular, if we have `typedef int I', then `int *', and 964 `I *' are different types. So, we have to pick a canonical 965 representative. We do this below. 966 967 Technically, this approach is actually more conservative that 968 it needs to be. In particular, `const int *' and `int *' 969 should be in different alias sets, according to the C and C++ 970 standard, since their types are not the same, and so, 971 technically, an `int **' and `const int **' cannot point at 972 the same thing. 973 974 But, the standard is wrong. In particular, this code is 975 legal C++: 976 977 int *ip; 978 int **ipp = &ip; 979 const int* const* cipp = ipp; 980 And, it doesn't make sense for that to be legal unless you 981 can dereference IPP and CIPP. So, we ignore cv-qualifiers on 982 the pointed-to types. This issue has been reported to the 983 C++ committee. 984 985 For this reason go to canonical type of the unqalified pointer type. 986 Until GCC 6 this code set all pointers sets to have alias set of 987 ptr_type_node but that is a bad idea, because it prevents disabiguations 988 in between pointers. For Firefox this accounts about 20% of all 989 disambiguations in the program. */ 990 else if (POINTER_TYPE_P (t) && t != ptr_type_node) 991 { 992 tree p; 993 auto_vec <bool, 8> reference; 994 995 /* Unnest all pointers and references. 996 We also want to make pointer to array/vector equivalent to pointer to 997 its element (see the reasoning above). Skip all those types, too. */ 998 for (p = t; POINTER_TYPE_P (p) 999 || (TREE_CODE (p) == ARRAY_TYPE 1000 && (!TYPE_NONALIASED_COMPONENT (p) 1001 || !COMPLETE_TYPE_P (p) 1002 || TYPE_STRUCTURAL_EQUALITY_P (p))) 1003 || TREE_CODE (p) == VECTOR_TYPE; 1004 p = TREE_TYPE (p)) 1005 { 1006 /* Ada supports recusive pointers. Instead of doing recrusion check 1007 just give up once the preallocated space of 8 elements is up. 1008 In this case just punt to void * alias set. */ 1009 if (reference.length () == 8) 1010 { 1011 p = ptr_type_node; 1012 break; 1013 } 1014 if (TREE_CODE (p) == REFERENCE_TYPE) 1015 /* In LTO we want languages that use references to be compatible 1016 with languages that use pointers. */ 1017 reference.safe_push (true && !in_lto_p); 1018 if (TREE_CODE (p) == POINTER_TYPE) 1019 reference.safe_push (false); 1020 } 1021 p = TYPE_MAIN_VARIANT (p); 1022 1023 /* Make void * compatible with char * and also void **. 1024 Programs are commonly violating TBAA by this. 1025 1026 We also make void * to conflict with every pointer 1027 (see record_component_aliases) and thus it is safe it to use it for 1028 pointers to types with TYPE_STRUCTURAL_EQUALITY_P. */ 1029 if (TREE_CODE (p) == VOID_TYPE || TYPE_STRUCTURAL_EQUALITY_P (p)) 1030 set = get_alias_set (ptr_type_node); 1031 else 1032 { 1033 /* Rebuild pointer type starting from canonical types using 1034 unqualified pointers and references only. This way all such 1035 pointers will have the same alias set and will conflict with 1036 each other. 1037 1038 Most of time we already have pointers or references of a given type. 1039 If not we build new one just to be sure that if someone later 1040 (probably only middle-end can, as we should assign all alias 1041 classes only after finishing translation unit) builds the pointer 1042 type, the canonical type will match. */ 1043 p = TYPE_CANONICAL (p); 1044 while (!reference.is_empty ()) 1045 { 1046 if (reference.pop ()) 1047 p = build_reference_type (p); 1048 else 1049 p = build_pointer_type (p); 1050 gcc_checking_assert (p == TYPE_MAIN_VARIANT (p)); 1051 /* build_pointer_type should always return the canonical type. 1052 For LTO TYPE_CANOINCAL may be NULL, because we do not compute 1053 them. Be sure that frontends do not glob canonical types of 1054 pointers in unexpected way and that p == TYPE_CANONICAL (p) 1055 in all other cases. */ 1056 gcc_checking_assert (!TYPE_CANONICAL (p) 1057 || p == TYPE_CANONICAL (p)); 1058 } 1059 1060 /* Assign the alias set to both p and t. 1061 We cannot call get_alias_set (p) here as that would trigger 1062 infinite recursion when p == t. In other cases it would just 1063 trigger unnecesary legwork of rebuilding the pointer again. */ 1064 gcc_checking_assert (p == TYPE_MAIN_VARIANT (p)); 1065 if (TYPE_ALIAS_SET_KNOWN_P (p)) 1066 set = TYPE_ALIAS_SET (p); 1067 else 1068 { 1069 set = new_alias_set (); 1070 TYPE_ALIAS_SET (p) = set; 1071 } 1072 } 1073 } 1074 /* Alias set of ptr_type_node is special and serve as universal pointer which 1075 is TBAA compatible with every other pointer type. Be sure we have the 1076 alias set built even for LTO which otherwise keeps all TYPE_CANONICAL 1077 of pointer types NULL. */ 1078 else if (t == ptr_type_node) 1079 set = new_alias_set (); 1080 1081 /* Otherwise make a new alias set for this type. */ 1082 else 1083 { 1084 /* Each canonical type gets its own alias set, so canonical types 1085 shouldn't form a tree. It doesn't really matter for types 1086 we handle specially above, so only check it where it possibly 1087 would result in a bogus alias set. */ 1088 gcc_checking_assert (TYPE_CANONICAL (t) == t); 1089 1090 set = new_alias_set (); 1091 } 1092 1093 TYPE_ALIAS_SET (t) = set; 1094 1095 /* If this is an aggregate type or a complex type, we must record any 1096 component aliasing information. */ 1097 if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE) 1098 record_component_aliases (t); 1099 1100 /* We treat pointer types specially in alias_set_subset_of. */ 1101 if (POINTER_TYPE_P (t) && set) 1102 { 1103 alias_set_entry *ase = get_alias_set_entry (set); 1104 if (!ase) 1105 ase = init_alias_set_entry (set); 1106 ase->is_pointer = true; 1107 ase->has_pointer = true; 1108 } 1109 1110 return set; 1111 } 1112 1113 /* Return a brand-new alias set. */ 1114 1115 alias_set_type 1116 new_alias_set (void) 1117 { 1118 if (alias_sets == 0) 1119 vec_safe_push (alias_sets, (alias_set_entry *) NULL); 1120 vec_safe_push (alias_sets, (alias_set_entry *) NULL); 1121 return alias_sets->length () - 1; 1122 } 1123 1124 /* Indicate that things in SUBSET can alias things in SUPERSET, but that 1125 not everything that aliases SUPERSET also aliases SUBSET. For example, 1126 in C, a store to an `int' can alias a load of a structure containing an 1127 `int', and vice versa. But it can't alias a load of a 'double' member 1128 of the same structure. Here, the structure would be the SUPERSET and 1129 `int' the SUBSET. This relationship is also described in the comment at 1130 the beginning of this file. 1131 1132 This function should be called only once per SUPERSET/SUBSET pair. 1133 1134 It is illegal for SUPERSET to be zero; everything is implicitly a 1135 subset of alias set zero. */ 1136 1137 void 1138 record_alias_subset (alias_set_type superset, alias_set_type subset) 1139 { 1140 alias_set_entry *superset_entry; 1141 alias_set_entry *subset_entry; 1142 1143 /* It is possible in complex type situations for both sets to be the same, 1144 in which case we can ignore this operation. */ 1145 if (superset == subset) 1146 return; 1147 1148 gcc_assert (superset); 1149 1150 superset_entry = get_alias_set_entry (superset); 1151 if (superset_entry == 0) 1152 { 1153 /* Create an entry for the SUPERSET, so that we have a place to 1154 attach the SUBSET. */ 1155 superset_entry = init_alias_set_entry (superset); 1156 } 1157 1158 if (subset == 0) 1159 superset_entry->has_zero_child = 1; 1160 else 1161 { 1162 subset_entry = get_alias_set_entry (subset); 1163 if (!superset_entry->children) 1164 superset_entry->children 1165 = hash_map<alias_set_hash, int>::create_ggc (64); 1166 /* If there is an entry for the subset, enter all of its children 1167 (if they are not already present) as children of the SUPERSET. */ 1168 if (subset_entry) 1169 { 1170 if (subset_entry->has_zero_child) 1171 superset_entry->has_zero_child = true; 1172 if (subset_entry->has_pointer) 1173 superset_entry->has_pointer = true; 1174 1175 if (subset_entry->children) 1176 { 1177 hash_map<alias_set_hash, int>::iterator iter 1178 = subset_entry->children->begin (); 1179 for (; iter != subset_entry->children->end (); ++iter) 1180 superset_entry->children->put ((*iter).first, (*iter).second); 1181 } 1182 } 1183 1184 /* Enter the SUBSET itself as a child of the SUPERSET. */ 1185 superset_entry->children->put (subset, 0); 1186 } 1187 } 1188 1189 /* Record that component types of TYPE, if any, are part of SUPERSET for 1190 aliasing purposes. For record types, we only record component types 1191 for fields that are not marked non-addressable. For array types, we 1192 only record the component type if it is not marked non-aliased. */ 1193 1194 void 1195 record_component_aliases (tree type, alias_set_type superset) 1196 { 1197 tree field; 1198 1199 if (superset == 0) 1200 return; 1201 1202 switch (TREE_CODE (type)) 1203 { 1204 case RECORD_TYPE: 1205 case UNION_TYPE: 1206 case QUAL_UNION_TYPE: 1207 for (field = TYPE_FIELDS (type); field != 0; field = DECL_CHAIN (field)) 1208 if (TREE_CODE (field) == FIELD_DECL && !DECL_NONADDRESSABLE_P (field)) 1209 { 1210 /* LTO type merging does not make any difference between 1211 component pointer types. We may have 1212 1213 struct foo {int *a;}; 1214 1215 as TYPE_CANONICAL of 1216 1217 struct bar {float *a;}; 1218 1219 Because accesses to int * and float * do not alias, we would get 1220 false negative when accessing the same memory location by 1221 float ** and bar *. We thus record the canonical type as: 1222 1223 struct {void *a;}; 1224 1225 void * is special cased and works as a universal pointer type. 1226 Accesses to it conflicts with accesses to any other pointer 1227 type. */ 1228 tree t = TREE_TYPE (field); 1229 if (in_lto_p) 1230 { 1231 /* VECTOR_TYPE and ARRAY_TYPE share the alias set with their 1232 element type and that type has to be normalized to void *, 1233 too, in the case it is a pointer. */ 1234 while (!canonical_type_used_p (t) && !POINTER_TYPE_P (t)) 1235 { 1236 gcc_checking_assert (TYPE_STRUCTURAL_EQUALITY_P (t)); 1237 t = TREE_TYPE (t); 1238 } 1239 if (POINTER_TYPE_P (t)) 1240 t = ptr_type_node; 1241 else if (flag_checking) 1242 gcc_checking_assert (get_alias_set (t) 1243 == get_alias_set (TREE_TYPE (field))); 1244 } 1245 1246 alias_set_type set = get_alias_set (t); 1247 record_alias_subset (superset, set); 1248 /* If the field has alias-set zero make sure to still record 1249 any componets of it. This makes sure that for 1250 struct A { 1251 struct B { 1252 int i; 1253 char c[4]; 1254 } b; 1255 }; 1256 in C++ even though 'B' has alias-set zero because 1257 TYPE_TYPELESS_STORAGE is set, 'A' has the alias-set of 1258 'int' as subset. */ 1259 if (set == 0) 1260 record_component_aliases (t, superset); 1261 } 1262 break; 1263 1264 case COMPLEX_TYPE: 1265 record_alias_subset (superset, get_alias_set (TREE_TYPE (type))); 1266 break; 1267 1268 /* VECTOR_TYPE and ARRAY_TYPE share the alias set with their 1269 element type. */ 1270 1271 default: 1272 break; 1273 } 1274 } 1275 1276 /* Record that component types of TYPE, if any, are part of that type for 1277 aliasing purposes. For record types, we only record component types 1278 for fields that are not marked non-addressable. For array types, we 1279 only record the component type if it is not marked non-aliased. */ 1280 1281 void 1282 record_component_aliases (tree type) 1283 { 1284 alias_set_type superset = get_alias_set (type); 1285 record_component_aliases (type, superset); 1286 } 1287 1288 1289 /* Allocate an alias set for use in storing and reading from the varargs 1290 spill area. */ 1291 1292 static GTY(()) alias_set_type varargs_set = -1; 1293 1294 alias_set_type 1295 get_varargs_alias_set (void) 1296 { 1297 #if 1 1298 /* We now lower VA_ARG_EXPR, and there's currently no way to attach the 1299 varargs alias set to an INDIRECT_REF (FIXME!), so we can't 1300 consistently use the varargs alias set for loads from the varargs 1301 area. So don't use it anywhere. */ 1302 return 0; 1303 #else 1304 if (varargs_set == -1) 1305 varargs_set = new_alias_set (); 1306 1307 return varargs_set; 1308 #endif 1309 } 1310 1311 /* Likewise, but used for the fixed portions of the frame, e.g., register 1312 save areas. */ 1313 1314 static GTY(()) alias_set_type frame_set = -1; 1315 1316 alias_set_type 1317 get_frame_alias_set (void) 1318 { 1319 if (frame_set == -1) 1320 frame_set = new_alias_set (); 1321 1322 return frame_set; 1323 } 1324 1325 /* Create a new, unique base with id ID. */ 1326 1327 static rtx 1328 unique_base_value (HOST_WIDE_INT id) 1329 { 1330 return gen_rtx_ADDRESS (Pmode, id); 1331 } 1332 1333 /* Return true if accesses based on any other base value cannot alias 1334 those based on X. */ 1335 1336 static bool 1337 unique_base_value_p (rtx x) 1338 { 1339 return GET_CODE (x) == ADDRESS && GET_MODE (x) == Pmode; 1340 } 1341 1342 /* Return true if X is known to be a base value. */ 1343 1344 static bool 1345 known_base_value_p (rtx x) 1346 { 1347 switch (GET_CODE (x)) 1348 { 1349 case LABEL_REF: 1350 case SYMBOL_REF: 1351 return true; 1352 1353 case ADDRESS: 1354 /* Arguments may or may not be bases; we don't know for sure. */ 1355 return GET_MODE (x) != VOIDmode; 1356 1357 default: 1358 return false; 1359 } 1360 } 1361 1362 /* Inside SRC, the source of a SET, find a base address. */ 1363 1364 static rtx 1365 find_base_value (rtx src) 1366 { 1367 unsigned int regno; 1368 scalar_int_mode int_mode; 1369 1370 #if defined (FIND_BASE_TERM) 1371 /* Try machine-dependent ways to find the base term. */ 1372 src = FIND_BASE_TERM (src); 1373 #endif 1374 1375 switch (GET_CODE (src)) 1376 { 1377 case SYMBOL_REF: 1378 case LABEL_REF: 1379 return src; 1380 1381 case REG: 1382 regno = REGNO (src); 1383 /* At the start of a function, argument registers have known base 1384 values which may be lost later. Returning an ADDRESS 1385 expression here allows optimization based on argument values 1386 even when the argument registers are used for other purposes. */ 1387 if (regno < FIRST_PSEUDO_REGISTER && copying_arguments) 1388 return new_reg_base_value[regno]; 1389 1390 /* If a pseudo has a known base value, return it. Do not do this 1391 for non-fixed hard regs since it can result in a circular 1392 dependency chain for registers which have values at function entry. 1393 1394 The test above is not sufficient because the scheduler may move 1395 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN. */ 1396 if ((regno >= FIRST_PSEUDO_REGISTER || fixed_regs[regno]) 1397 && regno < vec_safe_length (reg_base_value)) 1398 { 1399 /* If we're inside init_alias_analysis, use new_reg_base_value 1400 to reduce the number of relaxation iterations. */ 1401 if (new_reg_base_value && new_reg_base_value[regno] 1402 && DF_REG_DEF_COUNT (regno) == 1) 1403 return new_reg_base_value[regno]; 1404 1405 if ((*reg_base_value)[regno]) 1406 return (*reg_base_value)[regno]; 1407 } 1408 1409 return 0; 1410 1411 case MEM: 1412 /* Check for an argument passed in memory. Only record in the 1413 copying-arguments block; it is too hard to track changes 1414 otherwise. */ 1415 if (copying_arguments 1416 && (XEXP (src, 0) == arg_pointer_rtx 1417 || (GET_CODE (XEXP (src, 0)) == PLUS 1418 && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx))) 1419 return arg_base_value; 1420 return 0; 1421 1422 case CONST: 1423 src = XEXP (src, 0); 1424 if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS) 1425 break; 1426 1427 /* fall through */ 1428 1429 case PLUS: 1430 case MINUS: 1431 { 1432 rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1); 1433 1434 /* If either operand is a REG that is a known pointer, then it 1435 is the base. */ 1436 if (REG_P (src_0) && REG_POINTER (src_0)) 1437 return find_base_value (src_0); 1438 if (REG_P (src_1) && REG_POINTER (src_1)) 1439 return find_base_value (src_1); 1440 1441 /* If either operand is a REG, then see if we already have 1442 a known value for it. */ 1443 if (REG_P (src_0)) 1444 { 1445 temp = find_base_value (src_0); 1446 if (temp != 0) 1447 src_0 = temp; 1448 } 1449 1450 if (REG_P (src_1)) 1451 { 1452 temp = find_base_value (src_1); 1453 if (temp!= 0) 1454 src_1 = temp; 1455 } 1456 1457 /* If either base is named object or a special address 1458 (like an argument or stack reference), then use it for the 1459 base term. */ 1460 if (src_0 != 0 && known_base_value_p (src_0)) 1461 return src_0; 1462 1463 if (src_1 != 0 && known_base_value_p (src_1)) 1464 return src_1; 1465 1466 /* Guess which operand is the base address: 1467 If either operand is a symbol, then it is the base. If 1468 either operand is a CONST_INT, then the other is the base. */ 1469 if (CONST_INT_P (src_1) || CONSTANT_P (src_0)) 1470 return find_base_value (src_0); 1471 else if (CONST_INT_P (src_0) || CONSTANT_P (src_1)) 1472 return find_base_value (src_1); 1473 1474 return 0; 1475 } 1476 1477 case LO_SUM: 1478 /* The standard form is (lo_sum reg sym) so look only at the 1479 second operand. */ 1480 return find_base_value (XEXP (src, 1)); 1481 1482 case AND: 1483 /* If the second operand is constant set the base 1484 address to the first operand. */ 1485 if (CONST_INT_P (XEXP (src, 1)) && INTVAL (XEXP (src, 1)) != 0) 1486 return find_base_value (XEXP (src, 0)); 1487 return 0; 1488 1489 case TRUNCATE: 1490 /* As we do not know which address space the pointer is referring to, we can 1491 handle this only if the target does not support different pointer or 1492 address modes depending on the address space. */ 1493 if (!target_default_pointer_address_modes_p ()) 1494 break; 1495 if (!is_a <scalar_int_mode> (GET_MODE (src), &int_mode) 1496 || GET_MODE_PRECISION (int_mode) < GET_MODE_PRECISION (Pmode)) 1497 break; 1498 /* Fall through. */ 1499 case HIGH: 1500 case PRE_INC: 1501 case PRE_DEC: 1502 case POST_INC: 1503 case POST_DEC: 1504 case PRE_MODIFY: 1505 case POST_MODIFY: 1506 return find_base_value (XEXP (src, 0)); 1507 1508 case ZERO_EXTEND: 1509 case SIGN_EXTEND: /* used for NT/Alpha pointers */ 1510 /* As we do not know which address space the pointer is referring to, we can 1511 handle this only if the target does not support different pointer or 1512 address modes depending on the address space. */ 1513 if (!target_default_pointer_address_modes_p ()) 1514 break; 1515 1516 { 1517 rtx temp = find_base_value (XEXP (src, 0)); 1518 1519 if (temp != 0 && CONSTANT_P (temp)) 1520 temp = convert_memory_address (Pmode, temp); 1521 1522 return temp; 1523 } 1524 1525 default: 1526 break; 1527 } 1528 1529 return 0; 1530 } 1531 1532 /* Called from init_alias_analysis indirectly through note_stores, 1533 or directly if DEST is a register with a REG_NOALIAS note attached. 1534 SET is null in the latter case. */ 1535 1536 /* While scanning insns to find base values, reg_seen[N] is nonzero if 1537 register N has been set in this function. */ 1538 static sbitmap reg_seen; 1539 1540 static void 1541 record_set (rtx dest, const_rtx set, void *data ATTRIBUTE_UNUSED) 1542 { 1543 unsigned regno; 1544 rtx src; 1545 int n; 1546 1547 if (!REG_P (dest)) 1548 return; 1549 1550 regno = REGNO (dest); 1551 1552 gcc_checking_assert (regno < reg_base_value->length ()); 1553 1554 n = REG_NREGS (dest); 1555 if (n != 1) 1556 { 1557 while (--n >= 0) 1558 { 1559 bitmap_set_bit (reg_seen, regno + n); 1560 new_reg_base_value[regno + n] = 0; 1561 } 1562 return; 1563 } 1564 1565 if (set) 1566 { 1567 /* A CLOBBER wipes out any old value but does not prevent a previously 1568 unset register from acquiring a base address (i.e. reg_seen is not 1569 set). */ 1570 if (GET_CODE (set) == CLOBBER) 1571 { 1572 new_reg_base_value[regno] = 0; 1573 return; 1574 } 1575 /* A CLOBBER_HIGH only wipes out the old value if the mode of the old 1576 value is greater than that of the clobber. */ 1577 else if (GET_CODE (set) == CLOBBER_HIGH) 1578 { 1579 if (new_reg_base_value[regno] != 0 1580 && reg_is_clobbered_by_clobber_high ( 1581 regno, GET_MODE (new_reg_base_value[regno]), XEXP (set, 0))) 1582 new_reg_base_value[regno] = 0; 1583 return; 1584 } 1585 1586 src = SET_SRC (set); 1587 } 1588 else 1589 { 1590 /* There's a REG_NOALIAS note against DEST. */ 1591 if (bitmap_bit_p (reg_seen, regno)) 1592 { 1593 new_reg_base_value[regno] = 0; 1594 return; 1595 } 1596 bitmap_set_bit (reg_seen, regno); 1597 new_reg_base_value[regno] = unique_base_value (unique_id++); 1598 return; 1599 } 1600 1601 /* If this is not the first set of REGNO, see whether the new value 1602 is related to the old one. There are two cases of interest: 1603 1604 (1) The register might be assigned an entirely new value 1605 that has the same base term as the original set. 1606 1607 (2) The set might be a simple self-modification that 1608 cannot change REGNO's base value. 1609 1610 If neither case holds, reject the original base value as invalid. 1611 Note that the following situation is not detected: 1612 1613 extern int x, y; int *p = &x; p += (&y-&x); 1614 1615 ANSI C does not allow computing the difference of addresses 1616 of distinct top level objects. */ 1617 if (new_reg_base_value[regno] != 0 1618 && find_base_value (src) != new_reg_base_value[regno]) 1619 switch (GET_CODE (src)) 1620 { 1621 case LO_SUM: 1622 case MINUS: 1623 if (XEXP (src, 0) != dest && XEXP (src, 1) != dest) 1624 new_reg_base_value[regno] = 0; 1625 break; 1626 case PLUS: 1627 /* If the value we add in the PLUS is also a valid base value, 1628 this might be the actual base value, and the original value 1629 an index. */ 1630 { 1631 rtx other = NULL_RTX; 1632 1633 if (XEXP (src, 0) == dest) 1634 other = XEXP (src, 1); 1635 else if (XEXP (src, 1) == dest) 1636 other = XEXP (src, 0); 1637 1638 if (! other || find_base_value (other)) 1639 new_reg_base_value[regno] = 0; 1640 break; 1641 } 1642 case AND: 1643 if (XEXP (src, 0) != dest || !CONST_INT_P (XEXP (src, 1))) 1644 new_reg_base_value[regno] = 0; 1645 break; 1646 default: 1647 new_reg_base_value[regno] = 0; 1648 break; 1649 } 1650 /* If this is the first set of a register, record the value. */ 1651 else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno]) 1652 && ! bitmap_bit_p (reg_seen, regno) && new_reg_base_value[regno] == 0) 1653 new_reg_base_value[regno] = find_base_value (src); 1654 1655 bitmap_set_bit (reg_seen, regno); 1656 } 1657 1658 /* Return REG_BASE_VALUE for REGNO. Selective scheduler uses this to avoid 1659 using hard registers with non-null REG_BASE_VALUE for renaming. */ 1660 rtx 1661 get_reg_base_value (unsigned int regno) 1662 { 1663 return (*reg_base_value)[regno]; 1664 } 1665 1666 /* If a value is known for REGNO, return it. */ 1667 1668 rtx 1669 get_reg_known_value (unsigned int regno) 1670 { 1671 if (regno >= FIRST_PSEUDO_REGISTER) 1672 { 1673 regno -= FIRST_PSEUDO_REGISTER; 1674 if (regno < vec_safe_length (reg_known_value)) 1675 return (*reg_known_value)[regno]; 1676 } 1677 return NULL; 1678 } 1679 1680 /* Set it. */ 1681 1682 static void 1683 set_reg_known_value (unsigned int regno, rtx val) 1684 { 1685 if (regno >= FIRST_PSEUDO_REGISTER) 1686 { 1687 regno -= FIRST_PSEUDO_REGISTER; 1688 if (regno < vec_safe_length (reg_known_value)) 1689 (*reg_known_value)[regno] = val; 1690 } 1691 } 1692 1693 /* Similarly for reg_known_equiv_p. */ 1694 1695 bool 1696 get_reg_known_equiv_p (unsigned int regno) 1697 { 1698 if (regno >= FIRST_PSEUDO_REGISTER) 1699 { 1700 regno -= FIRST_PSEUDO_REGISTER; 1701 if (regno < vec_safe_length (reg_known_value)) 1702 return bitmap_bit_p (reg_known_equiv_p, regno); 1703 } 1704 return false; 1705 } 1706 1707 static void 1708 set_reg_known_equiv_p (unsigned int regno, bool val) 1709 { 1710 if (regno >= FIRST_PSEUDO_REGISTER) 1711 { 1712 regno -= FIRST_PSEUDO_REGISTER; 1713 if (regno < vec_safe_length (reg_known_value)) 1714 { 1715 if (val) 1716 bitmap_set_bit (reg_known_equiv_p, regno); 1717 else 1718 bitmap_clear_bit (reg_known_equiv_p, regno); 1719 } 1720 } 1721 } 1722 1723 1724 /* Returns a canonical version of X, from the point of view alias 1725 analysis. (For example, if X is a MEM whose address is a register, 1726 and the register has a known value (say a SYMBOL_REF), then a MEM 1727 whose address is the SYMBOL_REF is returned.) */ 1728 1729 rtx 1730 canon_rtx (rtx x) 1731 { 1732 /* Recursively look for equivalences. */ 1733 if (REG_P (x) && REGNO (x) >= FIRST_PSEUDO_REGISTER) 1734 { 1735 rtx t = get_reg_known_value (REGNO (x)); 1736 if (t == x) 1737 return x; 1738 if (t) 1739 return canon_rtx (t); 1740 } 1741 1742 if (GET_CODE (x) == PLUS) 1743 { 1744 rtx x0 = canon_rtx (XEXP (x, 0)); 1745 rtx x1 = canon_rtx (XEXP (x, 1)); 1746 1747 if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1)) 1748 return simplify_gen_binary (PLUS, GET_MODE (x), x0, x1); 1749 } 1750 1751 /* This gives us much better alias analysis when called from 1752 the loop optimizer. Note we want to leave the original 1753 MEM alone, but need to return the canonicalized MEM with 1754 all the flags with their original values. */ 1755 else if (MEM_P (x)) 1756 x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0))); 1757 1758 return x; 1759 } 1760 1761 /* Return 1 if X and Y are identical-looking rtx's. 1762 Expect that X and Y has been already canonicalized. 1763 1764 We use the data in reg_known_value above to see if two registers with 1765 different numbers are, in fact, equivalent. */ 1766 1767 static int 1768 rtx_equal_for_memref_p (const_rtx x, const_rtx y) 1769 { 1770 int i; 1771 int j; 1772 enum rtx_code code; 1773 const char *fmt; 1774 1775 if (x == 0 && y == 0) 1776 return 1; 1777 if (x == 0 || y == 0) 1778 return 0; 1779 1780 if (x == y) 1781 return 1; 1782 1783 code = GET_CODE (x); 1784 /* Rtx's of different codes cannot be equal. */ 1785 if (code != GET_CODE (y)) 1786 return 0; 1787 1788 /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. 1789 (REG:SI x) and (REG:HI x) are NOT equivalent. */ 1790 1791 if (GET_MODE (x) != GET_MODE (y)) 1792 return 0; 1793 1794 /* Some RTL can be compared without a recursive examination. */ 1795 switch (code) 1796 { 1797 case REG: 1798 return REGNO (x) == REGNO (y); 1799 1800 case LABEL_REF: 1801 return label_ref_label (x) == label_ref_label (y); 1802 1803 case SYMBOL_REF: 1804 return compare_base_symbol_refs (x, y) == 1; 1805 1806 case ENTRY_VALUE: 1807 /* This is magic, don't go through canonicalization et al. */ 1808 return rtx_equal_p (ENTRY_VALUE_EXP (x), ENTRY_VALUE_EXP (y)); 1809 1810 case VALUE: 1811 CASE_CONST_UNIQUE: 1812 /* Pointer equality guarantees equality for these nodes. */ 1813 return 0; 1814 1815 default: 1816 break; 1817 } 1818 1819 /* canon_rtx knows how to handle plus. No need to canonicalize. */ 1820 if (code == PLUS) 1821 return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0)) 1822 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1))) 1823 || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1)) 1824 && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0)))); 1825 /* For commutative operations, the RTX match if the operand match in any 1826 order. Also handle the simple binary and unary cases without a loop. */ 1827 if (COMMUTATIVE_P (x)) 1828 { 1829 rtx xop0 = canon_rtx (XEXP (x, 0)); 1830 rtx yop0 = canon_rtx (XEXP (y, 0)); 1831 rtx yop1 = canon_rtx (XEXP (y, 1)); 1832 1833 return ((rtx_equal_for_memref_p (xop0, yop0) 1834 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop1)) 1835 || (rtx_equal_for_memref_p (xop0, yop1) 1836 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop0))); 1837 } 1838 else if (NON_COMMUTATIVE_P (x)) 1839 { 1840 return (rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)), 1841 canon_rtx (XEXP (y, 0))) 1842 && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), 1843 canon_rtx (XEXP (y, 1)))); 1844 } 1845 else if (UNARY_P (x)) 1846 return rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)), 1847 canon_rtx (XEXP (y, 0))); 1848 1849 /* Compare the elements. If any pair of corresponding elements 1850 fail to match, return 0 for the whole things. 1851 1852 Limit cases to types which actually appear in addresses. */ 1853 1854 fmt = GET_RTX_FORMAT (code); 1855 for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--) 1856 { 1857 switch (fmt[i]) 1858 { 1859 case 'i': 1860 if (XINT (x, i) != XINT (y, i)) 1861 return 0; 1862 break; 1863 1864 case 'p': 1865 if (maybe_ne (SUBREG_BYTE (x), SUBREG_BYTE (y))) 1866 return 0; 1867 break; 1868 1869 case 'E': 1870 /* Two vectors must have the same length. */ 1871 if (XVECLEN (x, i) != XVECLEN (y, i)) 1872 return 0; 1873 1874 /* And the corresponding elements must match. */ 1875 for (j = 0; j < XVECLEN (x, i); j++) 1876 if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x, i, j)), 1877 canon_rtx (XVECEXP (y, i, j))) == 0) 1878 return 0; 1879 break; 1880 1881 case 'e': 1882 if (rtx_equal_for_memref_p (canon_rtx (XEXP (x, i)), 1883 canon_rtx (XEXP (y, i))) == 0) 1884 return 0; 1885 break; 1886 1887 /* This can happen for asm operands. */ 1888 case 's': 1889 if (strcmp (XSTR (x, i), XSTR (y, i))) 1890 return 0; 1891 break; 1892 1893 /* This can happen for an asm which clobbers memory. */ 1894 case '0': 1895 break; 1896 1897 /* It is believed that rtx's at this level will never 1898 contain anything but integers and other rtx's, 1899 except for within LABEL_REFs and SYMBOL_REFs. */ 1900 default: 1901 gcc_unreachable (); 1902 } 1903 } 1904 return 1; 1905 } 1906 1907 static rtx 1908 find_base_term (rtx x, vec<std::pair<cselib_val *, 1909 struct elt_loc_list *> > &visited_vals) 1910 { 1911 cselib_val *val; 1912 struct elt_loc_list *l, *f; 1913 rtx ret; 1914 scalar_int_mode int_mode; 1915 1916 #if defined (FIND_BASE_TERM) 1917 /* Try machine-dependent ways to find the base term. */ 1918 x = FIND_BASE_TERM (x); 1919 #endif 1920 1921 switch (GET_CODE (x)) 1922 { 1923 case REG: 1924 return REG_BASE_VALUE (x); 1925 1926 case TRUNCATE: 1927 /* As we do not know which address space the pointer is referring to, we can 1928 handle this only if the target does not support different pointer or 1929 address modes depending on the address space. */ 1930 if (!target_default_pointer_address_modes_p ()) 1931 return 0; 1932 if (!is_a <scalar_int_mode> (GET_MODE (x), &int_mode) 1933 || GET_MODE_PRECISION (int_mode) < GET_MODE_PRECISION (Pmode)) 1934 return 0; 1935 /* Fall through. */ 1936 case HIGH: 1937 case PRE_INC: 1938 case PRE_DEC: 1939 case POST_INC: 1940 case POST_DEC: 1941 case PRE_MODIFY: 1942 case POST_MODIFY: 1943 return find_base_term (XEXP (x, 0), visited_vals); 1944 1945 case ZERO_EXTEND: 1946 case SIGN_EXTEND: /* Used for Alpha/NT pointers */ 1947 /* As we do not know which address space the pointer is referring to, we can 1948 handle this only if the target does not support different pointer or 1949 address modes depending on the address space. */ 1950 if (!target_default_pointer_address_modes_p ()) 1951 return 0; 1952 1953 { 1954 rtx temp = find_base_term (XEXP (x, 0), visited_vals); 1955 1956 if (temp != 0 && CONSTANT_P (temp)) 1957 temp = convert_memory_address (Pmode, temp); 1958 1959 return temp; 1960 } 1961 1962 case VALUE: 1963 val = CSELIB_VAL_PTR (x); 1964 ret = NULL_RTX; 1965 1966 if (!val) 1967 return ret; 1968 1969 if (cselib_sp_based_value_p (val)) 1970 return static_reg_base_value[STACK_POINTER_REGNUM]; 1971 1972 f = val->locs; 1973 /* Reset val->locs to avoid infinite recursion. */ 1974 if (f) 1975 visited_vals.safe_push (std::make_pair (val, f)); 1976 val->locs = NULL; 1977 1978 for (l = f; l; l = l->next) 1979 if (GET_CODE (l->loc) == VALUE 1980 && CSELIB_VAL_PTR (l->loc)->locs 1981 && !CSELIB_VAL_PTR (l->loc)->locs->next 1982 && CSELIB_VAL_PTR (l->loc)->locs->loc == x) 1983 continue; 1984 else if ((ret = find_base_term (l->loc, visited_vals)) != 0) 1985 break; 1986 1987 return ret; 1988 1989 case LO_SUM: 1990 /* The standard form is (lo_sum reg sym) so look only at the 1991 second operand. */ 1992 return find_base_term (XEXP (x, 1), visited_vals); 1993 1994 case CONST: 1995 x = XEXP (x, 0); 1996 if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS) 1997 return 0; 1998 /* Fall through. */ 1999 case PLUS: 2000 case MINUS: 2001 { 2002 rtx tmp1 = XEXP (x, 0); 2003 rtx tmp2 = XEXP (x, 1); 2004 2005 /* This is a little bit tricky since we have to determine which of 2006 the two operands represents the real base address. Otherwise this 2007 routine may return the index register instead of the base register. 2008 2009 That may cause us to believe no aliasing was possible, when in 2010 fact aliasing is possible. 2011 2012 We use a few simple tests to guess the base register. Additional 2013 tests can certainly be added. For example, if one of the operands 2014 is a shift or multiply, then it must be the index register and the 2015 other operand is the base register. */ 2016 2017 if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2)) 2018 return find_base_term (tmp2, visited_vals); 2019 2020 /* If either operand is known to be a pointer, then prefer it 2021 to determine the base term. */ 2022 if (REG_P (tmp1) && REG_POINTER (tmp1)) 2023 ; 2024 else if (REG_P (tmp2) && REG_POINTER (tmp2)) 2025 std::swap (tmp1, tmp2); 2026 /* If second argument is constant which has base term, prefer it 2027 over variable tmp1. See PR64025. */ 2028 else if (CONSTANT_P (tmp2) && !CONST_INT_P (tmp2)) 2029 std::swap (tmp1, tmp2); 2030 2031 /* Go ahead and find the base term for both operands. If either base 2032 term is from a pointer or is a named object or a special address 2033 (like an argument or stack reference), then use it for the 2034 base term. */ 2035 rtx base = find_base_term (tmp1, visited_vals); 2036 if (base != NULL_RTX 2037 && ((REG_P (tmp1) && REG_POINTER (tmp1)) 2038 || known_base_value_p (base))) 2039 return base; 2040 base = find_base_term (tmp2, visited_vals); 2041 if (base != NULL_RTX 2042 && ((REG_P (tmp2) && REG_POINTER (tmp2)) 2043 || known_base_value_p (base))) 2044 return base; 2045 2046 /* We could not determine which of the two operands was the 2047 base register and which was the index. So we can determine 2048 nothing from the base alias check. */ 2049 return 0; 2050 } 2051 2052 case AND: 2053 if (CONST_INT_P (XEXP (x, 1)) && INTVAL (XEXP (x, 1)) != 0) 2054 return find_base_term (XEXP (x, 0), visited_vals); 2055 return 0; 2056 2057 case SYMBOL_REF: 2058 case LABEL_REF: 2059 return x; 2060 2061 default: 2062 return 0; 2063 } 2064 } 2065 2066 /* Wrapper around the worker above which removes locs from visited VALUEs 2067 to avoid visiting them multiple times. We unwind that changes here. */ 2068 2069 static rtx 2070 find_base_term (rtx x) 2071 { 2072 auto_vec<std::pair<cselib_val *, struct elt_loc_list *>, 32> visited_vals; 2073 rtx res = find_base_term (x, visited_vals); 2074 for (unsigned i = 0; i < visited_vals.length (); ++i) 2075 visited_vals[i].first->locs = visited_vals[i].second; 2076 return res; 2077 } 2078 2079 /* Return true if accesses to address X may alias accesses based 2080 on the stack pointer. */ 2081 2082 bool 2083 may_be_sp_based_p (rtx x) 2084 { 2085 rtx base = find_base_term (x); 2086 return !base || base == static_reg_base_value[STACK_POINTER_REGNUM]; 2087 } 2088 2089 /* BASE1 and BASE2 are decls. Return 1 if they refer to same object, 0 2090 if they refer to different objects and -1 if we cannot decide. */ 2091 2092 int 2093 compare_base_decls (tree base1, tree base2) 2094 { 2095 int ret; 2096 gcc_checking_assert (DECL_P (base1) && DECL_P (base2)); 2097 if (base1 == base2) 2098 return 1; 2099 2100 /* If we have two register decls with register specification we 2101 cannot decide unless their assembler names are the same. */ 2102 if (DECL_REGISTER (base1) 2103 && DECL_REGISTER (base2) 2104 && HAS_DECL_ASSEMBLER_NAME_P (base1) 2105 && HAS_DECL_ASSEMBLER_NAME_P (base2) 2106 && DECL_ASSEMBLER_NAME_SET_P (base1) 2107 && DECL_ASSEMBLER_NAME_SET_P (base2)) 2108 { 2109 if (DECL_ASSEMBLER_NAME_RAW (base1) == DECL_ASSEMBLER_NAME_RAW (base2)) 2110 return 1; 2111 return -1; 2112 } 2113 2114 /* Declarations of non-automatic variables may have aliases. All other 2115 decls are unique. */ 2116 if (!decl_in_symtab_p (base1) 2117 || !decl_in_symtab_p (base2)) 2118 return 0; 2119 2120 /* Don't cause symbols to be inserted by the act of checking. */ 2121 symtab_node *node1 = symtab_node::get (base1); 2122 if (!node1) 2123 return 0; 2124 symtab_node *node2 = symtab_node::get (base2); 2125 if (!node2) 2126 return 0; 2127 2128 ret = node1->equal_address_to (node2, true); 2129 return ret; 2130 } 2131 2132 /* Same as compare_base_decls but for SYMBOL_REF. */ 2133 2134 static int 2135 compare_base_symbol_refs (const_rtx x_base, const_rtx y_base) 2136 { 2137 tree x_decl = SYMBOL_REF_DECL (x_base); 2138 tree y_decl = SYMBOL_REF_DECL (y_base); 2139 bool binds_def = true; 2140 2141 if (XSTR (x_base, 0) == XSTR (y_base, 0)) 2142 return 1; 2143 if (x_decl && y_decl) 2144 return compare_base_decls (x_decl, y_decl); 2145 if (x_decl || y_decl) 2146 { 2147 if (!x_decl) 2148 { 2149 std::swap (x_decl, y_decl); 2150 std::swap (x_base, y_base); 2151 } 2152 /* We handle specially only section anchors and assume that other 2153 labels may overlap with user variables in an arbitrary way. */ 2154 if (!SYMBOL_REF_HAS_BLOCK_INFO_P (y_base)) 2155 return -1; 2156 /* Anchors contains static VAR_DECLs and CONST_DECLs. We are safe 2157 to ignore CONST_DECLs because they are readonly. */ 2158 if (!VAR_P (x_decl) 2159 || (!TREE_STATIC (x_decl) && !TREE_PUBLIC (x_decl))) 2160 return 0; 2161 2162 symtab_node *x_node = symtab_node::get_create (x_decl) 2163 ->ultimate_alias_target (); 2164 /* External variable cannot be in section anchor. */ 2165 if (!x_node->definition) 2166 return 0; 2167 x_base = XEXP (DECL_RTL (x_node->decl), 0); 2168 /* If not in anchor, we can disambiguate. */ 2169 if (!SYMBOL_REF_HAS_BLOCK_INFO_P (x_base)) 2170 return 0; 2171 2172 /* We have an alias of anchored variable. If it can be interposed; 2173 we must assume it may or may not alias its anchor. */ 2174 binds_def = decl_binds_to_current_def_p (x_decl); 2175 } 2176 /* If we have variable in section anchor, we can compare by offset. */ 2177 if (SYMBOL_REF_HAS_BLOCK_INFO_P (x_base) 2178 && SYMBOL_REF_HAS_BLOCK_INFO_P (y_base)) 2179 { 2180 if (SYMBOL_REF_BLOCK (x_base) != SYMBOL_REF_BLOCK (y_base)) 2181 return 0; 2182 if (SYMBOL_REF_BLOCK_OFFSET (x_base) == SYMBOL_REF_BLOCK_OFFSET (y_base)) 2183 return binds_def ? 1 : -1; 2184 if (SYMBOL_REF_ANCHOR_P (x_base) != SYMBOL_REF_ANCHOR_P (y_base)) 2185 return -1; 2186 return 0; 2187 } 2188 /* In general we assume that memory locations pointed to by different labels 2189 may overlap in undefined ways. */ 2190 return -1; 2191 } 2192 2193 /* Return 0 if the addresses X and Y are known to point to different 2194 objects, 1 if they might be pointers to the same object. */ 2195 2196 static int 2197 base_alias_check (rtx x, rtx x_base, rtx y, rtx y_base, 2198 machine_mode x_mode, machine_mode y_mode) 2199 { 2200 /* If the address itself has no known base see if a known equivalent 2201 value has one. If either address still has no known base, nothing 2202 is known about aliasing. */ 2203 if (x_base == 0) 2204 { 2205 rtx x_c; 2206 2207 if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x) 2208 return 1; 2209 2210 x_base = find_base_term (x_c); 2211 if (x_base == 0) 2212 return 1; 2213 } 2214 2215 if (y_base == 0) 2216 { 2217 rtx y_c; 2218 if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y) 2219 return 1; 2220 2221 y_base = find_base_term (y_c); 2222 if (y_base == 0) 2223 return 1; 2224 } 2225 2226 /* If the base addresses are equal nothing is known about aliasing. */ 2227 if (rtx_equal_p (x_base, y_base)) 2228 return 1; 2229 2230 /* The base addresses are different expressions. If they are not accessed 2231 via AND, there is no conflict. We can bring knowledge of object 2232 alignment into play here. For example, on alpha, "char a, b;" can 2233 alias one another, though "char a; long b;" cannot. AND addresses may 2234 implicitly alias surrounding objects; i.e. unaligned access in DImode 2235 via AND address can alias all surrounding object types except those 2236 with aligment 8 or higher. */ 2237 if (GET_CODE (x) == AND && GET_CODE (y) == AND) 2238 return 1; 2239 if (GET_CODE (x) == AND 2240 && (!CONST_INT_P (XEXP (x, 1)) 2241 || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1)))) 2242 return 1; 2243 if (GET_CODE (y) == AND 2244 && (!CONST_INT_P (XEXP (y, 1)) 2245 || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1)))) 2246 return 1; 2247 2248 /* Differing symbols not accessed via AND never alias. */ 2249 if (GET_CODE (x_base) == SYMBOL_REF && GET_CODE (y_base) == SYMBOL_REF) 2250 return compare_base_symbol_refs (x_base, y_base) != 0; 2251 2252 if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS) 2253 return 0; 2254 2255 if (unique_base_value_p (x_base) || unique_base_value_p (y_base)) 2256 return 0; 2257 2258 return 1; 2259 } 2260 2261 /* Return TRUE if EXPR refers to a VALUE whose uid is greater than 2262 (or equal to) that of V. */ 2263 2264 static bool 2265 refs_newer_value_p (const_rtx expr, rtx v) 2266 { 2267 int minuid = CSELIB_VAL_PTR (v)->uid; 2268 subrtx_iterator::array_type array; 2269 FOR_EACH_SUBRTX (iter, array, expr, NONCONST) 2270 if (GET_CODE (*iter) == VALUE && CSELIB_VAL_PTR (*iter)->uid >= minuid) 2271 return true; 2272 return false; 2273 } 2274 2275 /* Convert the address X into something we can use. This is done by returning 2276 it unchanged unless it is a VALUE or VALUE +/- constant; for VALUE 2277 we call cselib to get a more useful rtx. */ 2278 2279 rtx 2280 get_addr (rtx x) 2281 { 2282 cselib_val *v; 2283 struct elt_loc_list *l; 2284 2285 if (GET_CODE (x) != VALUE) 2286 { 2287 if ((GET_CODE (x) == PLUS || GET_CODE (x) == MINUS) 2288 && GET_CODE (XEXP (x, 0)) == VALUE 2289 && CONST_SCALAR_INT_P (XEXP (x, 1))) 2290 { 2291 rtx op0 = get_addr (XEXP (x, 0)); 2292 if (op0 != XEXP (x, 0)) 2293 { 2294 poly_int64 c; 2295 if (GET_CODE (x) == PLUS 2296 && poly_int_rtx_p (XEXP (x, 1), &c)) 2297 return plus_constant (GET_MODE (x), op0, c); 2298 return simplify_gen_binary (GET_CODE (x), GET_MODE (x), 2299 op0, XEXP (x, 1)); 2300 } 2301 } 2302 return x; 2303 } 2304 v = CSELIB_VAL_PTR (x); 2305 if (v) 2306 { 2307 bool have_equivs = cselib_have_permanent_equivalences (); 2308 if (have_equivs) 2309 v = canonical_cselib_val (v); 2310 for (l = v->locs; l; l = l->next) 2311 if (CONSTANT_P (l->loc)) 2312 return l->loc; 2313 for (l = v->locs; l; l = l->next) 2314 if (!REG_P (l->loc) && !MEM_P (l->loc) 2315 /* Avoid infinite recursion when potentially dealing with 2316 var-tracking artificial equivalences, by skipping the 2317 equivalences themselves, and not choosing expressions 2318 that refer to newer VALUEs. */ 2319 && (!have_equivs 2320 || (GET_CODE (l->loc) != VALUE 2321 && !refs_newer_value_p (l->loc, x)))) 2322 return l->loc; 2323 if (have_equivs) 2324 { 2325 for (l = v->locs; l; l = l->next) 2326 if (REG_P (l->loc) 2327 || (GET_CODE (l->loc) != VALUE 2328 && !refs_newer_value_p (l->loc, x))) 2329 return l->loc; 2330 /* Return the canonical value. */ 2331 return v->val_rtx; 2332 } 2333 if (v->locs) 2334 return v->locs->loc; 2335 } 2336 return x; 2337 } 2338 2339 /* Return the address of the (N_REFS + 1)th memory reference to ADDR 2340 where SIZE is the size in bytes of the memory reference. If ADDR 2341 is not modified by the memory reference then ADDR is returned. */ 2342 2343 static rtx 2344 addr_side_effect_eval (rtx addr, poly_int64 size, int n_refs) 2345 { 2346 poly_int64 offset = 0; 2347 2348 switch (GET_CODE (addr)) 2349 { 2350 case PRE_INC: 2351 offset = (n_refs + 1) * size; 2352 break; 2353 case PRE_DEC: 2354 offset = -(n_refs + 1) * size; 2355 break; 2356 case POST_INC: 2357 offset = n_refs * size; 2358 break; 2359 case POST_DEC: 2360 offset = -n_refs * size; 2361 break; 2362 2363 default: 2364 return addr; 2365 } 2366 2367 addr = plus_constant (GET_MODE (addr), XEXP (addr, 0), offset); 2368 addr = canon_rtx (addr); 2369 2370 return addr; 2371 } 2372 2373 /* Return TRUE if an object X sized at XSIZE bytes and another object 2374 Y sized at YSIZE bytes, starting C bytes after X, may overlap. If 2375 any of the sizes is zero, assume an overlap, otherwise use the 2376 absolute value of the sizes as the actual sizes. */ 2377 2378 static inline bool 2379 offset_overlap_p (poly_int64 c, poly_int64 xsize, poly_int64 ysize) 2380 { 2381 if (known_eq (xsize, 0) || known_eq (ysize, 0)) 2382 return true; 2383 2384 if (maybe_ge (c, 0)) 2385 return maybe_gt (maybe_lt (xsize, 0) ? -xsize : xsize, c); 2386 else 2387 return maybe_gt (maybe_lt (ysize, 0) ? -ysize : ysize, -c); 2388 } 2389 2390 /* Return one if X and Y (memory addresses) reference the 2391 same location in memory or if the references overlap. 2392 Return zero if they do not overlap, else return 2393 minus one in which case they still might reference the same location. 2394 2395 C is an offset accumulator. When 2396 C is nonzero, we are testing aliases between X and Y + C. 2397 XSIZE is the size in bytes of the X reference, 2398 similarly YSIZE is the size in bytes for Y. 2399 Expect that canon_rtx has been already called for X and Y. 2400 2401 If XSIZE or YSIZE is zero, we do not know the amount of memory being 2402 referenced (the reference was BLKmode), so make the most pessimistic 2403 assumptions. 2404 2405 If XSIZE or YSIZE is negative, we may access memory outside the object 2406 being referenced as a side effect. This can happen when using AND to 2407 align memory references, as is done on the Alpha. 2408 2409 Nice to notice that varying addresses cannot conflict with fp if no 2410 local variables had their addresses taken, but that's too hard now. 2411 2412 ??? Contrary to the tree alias oracle this does not return 2413 one for X + non-constant and Y + non-constant when X and Y are equal. 2414 If that is fixed the TBAA hack for union type-punning can be removed. */ 2415 2416 static int 2417 memrefs_conflict_p (poly_int64 xsize, rtx x, poly_int64 ysize, rtx y, 2418 poly_int64 c) 2419 { 2420 if (GET_CODE (x) == VALUE) 2421 { 2422 if (REG_P (y)) 2423 { 2424 struct elt_loc_list *l = NULL; 2425 if (CSELIB_VAL_PTR (x)) 2426 for (l = canonical_cselib_val (CSELIB_VAL_PTR (x))->locs; 2427 l; l = l->next) 2428 if (REG_P (l->loc) && rtx_equal_for_memref_p (l->loc, y)) 2429 break; 2430 if (l) 2431 x = y; 2432 else 2433 x = get_addr (x); 2434 } 2435 /* Don't call get_addr if y is the same VALUE. */ 2436 else if (x != y) 2437 x = get_addr (x); 2438 } 2439 if (GET_CODE (y) == VALUE) 2440 { 2441 if (REG_P (x)) 2442 { 2443 struct elt_loc_list *l = NULL; 2444 if (CSELIB_VAL_PTR (y)) 2445 for (l = canonical_cselib_val (CSELIB_VAL_PTR (y))->locs; 2446 l; l = l->next) 2447 if (REG_P (l->loc) && rtx_equal_for_memref_p (l->loc, x)) 2448 break; 2449 if (l) 2450 y = x; 2451 else 2452 y = get_addr (y); 2453 } 2454 /* Don't call get_addr if x is the same VALUE. */ 2455 else if (y != x) 2456 y = get_addr (y); 2457 } 2458 if (GET_CODE (x) == HIGH) 2459 x = XEXP (x, 0); 2460 else if (GET_CODE (x) == LO_SUM) 2461 x = XEXP (x, 1); 2462 else 2463 x = addr_side_effect_eval (x, maybe_lt (xsize, 0) ? -xsize : xsize, 0); 2464 if (GET_CODE (y) == HIGH) 2465 y = XEXP (y, 0); 2466 else if (GET_CODE (y) == LO_SUM) 2467 y = XEXP (y, 1); 2468 else 2469 y = addr_side_effect_eval (y, maybe_lt (ysize, 0) ? -ysize : ysize, 0); 2470 2471 if (GET_CODE (x) == SYMBOL_REF && GET_CODE (y) == SYMBOL_REF) 2472 { 2473 int cmp = compare_base_symbol_refs (x,y); 2474 2475 /* If both decls are the same, decide by offsets. */ 2476 if (cmp == 1) 2477 return offset_overlap_p (c, xsize, ysize); 2478 /* Assume a potential overlap for symbolic addresses that went 2479 through alignment adjustments (i.e., that have negative 2480 sizes), because we can't know how far they are from each 2481 other. */ 2482 if (maybe_lt (xsize, 0) || maybe_lt (ysize, 0)) 2483 return -1; 2484 /* If decls are different or we know by offsets that there is no overlap, 2485 we win. */ 2486 if (!cmp || !offset_overlap_p (c, xsize, ysize)) 2487 return 0; 2488 /* Decls may or may not be different and offsets overlap....*/ 2489 return -1; 2490 } 2491 else if (rtx_equal_for_memref_p (x, y)) 2492 { 2493 return offset_overlap_p (c, xsize, ysize); 2494 } 2495 2496 /* This code used to check for conflicts involving stack references and 2497 globals but the base address alias code now handles these cases. */ 2498 2499 if (GET_CODE (x) == PLUS) 2500 { 2501 /* The fact that X is canonicalized means that this 2502 PLUS rtx is canonicalized. */ 2503 rtx x0 = XEXP (x, 0); 2504 rtx x1 = XEXP (x, 1); 2505 2506 /* However, VALUEs might end up in different positions even in 2507 canonical PLUSes. Comparing their addresses is enough. */ 2508 if (x0 == y) 2509 return memrefs_conflict_p (xsize, x1, ysize, const0_rtx, c); 2510 else if (x1 == y) 2511 return memrefs_conflict_p (xsize, x0, ysize, const0_rtx, c); 2512 2513 poly_int64 cx1, cy1; 2514 if (GET_CODE (y) == PLUS) 2515 { 2516 /* The fact that Y is canonicalized means that this 2517 PLUS rtx is canonicalized. */ 2518 rtx y0 = XEXP (y, 0); 2519 rtx y1 = XEXP (y, 1); 2520 2521 if (x0 == y1) 2522 return memrefs_conflict_p (xsize, x1, ysize, y0, c); 2523 if (x1 == y0) 2524 return memrefs_conflict_p (xsize, x0, ysize, y1, c); 2525 2526 if (rtx_equal_for_memref_p (x1, y1)) 2527 return memrefs_conflict_p (xsize, x0, ysize, y0, c); 2528 if (rtx_equal_for_memref_p (x0, y0)) 2529 return memrefs_conflict_p (xsize, x1, ysize, y1, c); 2530 if (poly_int_rtx_p (x1, &cx1)) 2531 { 2532 if (poly_int_rtx_p (y1, &cy1)) 2533 return memrefs_conflict_p (xsize, x0, ysize, y0, 2534 c - cx1 + cy1); 2535 else 2536 return memrefs_conflict_p (xsize, x0, ysize, y, c - cx1); 2537 } 2538 else if (poly_int_rtx_p (y1, &cy1)) 2539 return memrefs_conflict_p (xsize, x, ysize, y0, c + cy1); 2540 2541 return -1; 2542 } 2543 else if (poly_int_rtx_p (x1, &cx1)) 2544 return memrefs_conflict_p (xsize, x0, ysize, y, c - cx1); 2545 } 2546 else if (GET_CODE (y) == PLUS) 2547 { 2548 /* The fact that Y is canonicalized means that this 2549 PLUS rtx is canonicalized. */ 2550 rtx y0 = XEXP (y, 0); 2551 rtx y1 = XEXP (y, 1); 2552 2553 if (x == y0) 2554 return memrefs_conflict_p (xsize, const0_rtx, ysize, y1, c); 2555 if (x == y1) 2556 return memrefs_conflict_p (xsize, const0_rtx, ysize, y0, c); 2557 2558 poly_int64 cy1; 2559 if (poly_int_rtx_p (y1, &cy1)) 2560 return memrefs_conflict_p (xsize, x, ysize, y0, c + cy1); 2561 else 2562 return -1; 2563 } 2564 2565 if (GET_CODE (x) == GET_CODE (y)) 2566 switch (GET_CODE (x)) 2567 { 2568 case MULT: 2569 { 2570 /* Handle cases where we expect the second operands to be the 2571 same, and check only whether the first operand would conflict 2572 or not. */ 2573 rtx x0, y0; 2574 rtx x1 = canon_rtx (XEXP (x, 1)); 2575 rtx y1 = canon_rtx (XEXP (y, 1)); 2576 if (! rtx_equal_for_memref_p (x1, y1)) 2577 return -1; 2578 x0 = canon_rtx (XEXP (x, 0)); 2579 y0 = canon_rtx (XEXP (y, 0)); 2580 if (rtx_equal_for_memref_p (x0, y0)) 2581 return offset_overlap_p (c, xsize, ysize); 2582 2583 /* Can't properly adjust our sizes. */ 2584 poly_int64 c1; 2585 if (!poly_int_rtx_p (x1, &c1) 2586 || !can_div_trunc_p (xsize, c1, &xsize) 2587 || !can_div_trunc_p (ysize, c1, &ysize) 2588 || !can_div_trunc_p (c, c1, &c)) 2589 return -1; 2590 return memrefs_conflict_p (xsize, x0, ysize, y0, c); 2591 } 2592 2593 default: 2594 break; 2595 } 2596 2597 /* Deal with alignment ANDs by adjusting offset and size so as to 2598 cover the maximum range, without taking any previously known 2599 alignment into account. Make a size negative after such an 2600 adjustments, so that, if we end up with e.g. two SYMBOL_REFs, we 2601 assume a potential overlap, because they may end up in contiguous 2602 memory locations and the stricter-alignment access may span over 2603 part of both. */ 2604 if (GET_CODE (x) == AND && CONST_INT_P (XEXP (x, 1))) 2605 { 2606 HOST_WIDE_INT sc = INTVAL (XEXP (x, 1)); 2607 unsigned HOST_WIDE_INT uc = sc; 2608 if (sc < 0 && pow2_or_zerop (-uc)) 2609 { 2610 if (maybe_gt (xsize, 0)) 2611 xsize = -xsize; 2612 if (maybe_ne (xsize, 0)) 2613 xsize += sc + 1; 2614 c -= sc + 1; 2615 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), 2616 ysize, y, c); 2617 } 2618 } 2619 if (GET_CODE (y) == AND && CONST_INT_P (XEXP (y, 1))) 2620 { 2621 HOST_WIDE_INT sc = INTVAL (XEXP (y, 1)); 2622 unsigned HOST_WIDE_INT uc = sc; 2623 if (sc < 0 && pow2_or_zerop (-uc)) 2624 { 2625 if (maybe_gt (ysize, 0)) 2626 ysize = -ysize; 2627 if (maybe_ne (ysize, 0)) 2628 ysize += sc + 1; 2629 c += sc + 1; 2630 return memrefs_conflict_p (xsize, x, 2631 ysize, canon_rtx (XEXP (y, 0)), c); 2632 } 2633 } 2634 2635 if (CONSTANT_P (x)) 2636 { 2637 poly_int64 cx, cy; 2638 if (poly_int_rtx_p (x, &cx) && poly_int_rtx_p (y, &cy)) 2639 { 2640 c += cy - cx; 2641 return offset_overlap_p (c, xsize, ysize); 2642 } 2643 2644 if (GET_CODE (x) == CONST) 2645 { 2646 if (GET_CODE (y) == CONST) 2647 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), 2648 ysize, canon_rtx (XEXP (y, 0)), c); 2649 else 2650 return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), 2651 ysize, y, c); 2652 } 2653 if (GET_CODE (y) == CONST) 2654 return memrefs_conflict_p (xsize, x, ysize, 2655 canon_rtx (XEXP (y, 0)), c); 2656 2657 /* Assume a potential overlap for symbolic addresses that went 2658 through alignment adjustments (i.e., that have negative 2659 sizes), because we can't know how far they are from each 2660 other. */ 2661 if (CONSTANT_P (y)) 2662 return (maybe_lt (xsize, 0) 2663 || maybe_lt (ysize, 0) 2664 || offset_overlap_p (c, xsize, ysize)); 2665 2666 return -1; 2667 } 2668 2669 return -1; 2670 } 2671 2672 /* Functions to compute memory dependencies. 2673 2674 Since we process the insns in execution order, we can build tables 2675 to keep track of what registers are fixed (and not aliased), what registers 2676 are varying in known ways, and what registers are varying in unknown 2677 ways. 2678 2679 If both memory references are volatile, then there must always be a 2680 dependence between the two references, since their order cannot be 2681 changed. A volatile and non-volatile reference can be interchanged 2682 though. 2683 2684 We also must allow AND addresses, because they may generate accesses 2685 outside the object being referenced. This is used to generate aligned 2686 addresses from unaligned addresses, for instance, the alpha 2687 storeqi_unaligned pattern. */ 2688 2689 /* Read dependence: X is read after read in MEM takes place. There can 2690 only be a dependence here if both reads are volatile, or if either is 2691 an explicit barrier. */ 2692 2693 int 2694 read_dependence (const_rtx mem, const_rtx x) 2695 { 2696 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) 2697 return true; 2698 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER 2699 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER) 2700 return true; 2701 return false; 2702 } 2703 2704 /* Look at the bottom of the COMPONENT_REF list for a DECL, and return it. */ 2705 2706 static tree 2707 decl_for_component_ref (tree x) 2708 { 2709 do 2710 { 2711 x = TREE_OPERAND (x, 0); 2712 } 2713 while (x && TREE_CODE (x) == COMPONENT_REF); 2714 2715 return x && DECL_P (x) ? x : NULL_TREE; 2716 } 2717 2718 /* Walk up the COMPONENT_REF list in X and adjust *OFFSET to compensate 2719 for the offset of the field reference. *KNOWN_P says whether the 2720 offset is known. */ 2721 2722 static void 2723 adjust_offset_for_component_ref (tree x, bool *known_p, 2724 poly_int64 *offset) 2725 { 2726 if (!*known_p) 2727 return; 2728 do 2729 { 2730 tree xoffset = component_ref_field_offset (x); 2731 tree field = TREE_OPERAND (x, 1); 2732 if (!poly_int_tree_p (xoffset)) 2733 { 2734 *known_p = false; 2735 return; 2736 } 2737 2738 poly_offset_int woffset 2739 = (wi::to_poly_offset (xoffset) 2740 + (wi::to_offset (DECL_FIELD_BIT_OFFSET (field)) 2741 >> LOG2_BITS_PER_UNIT) 2742 + *offset); 2743 if (!woffset.to_shwi (offset)) 2744 { 2745 *known_p = false; 2746 return; 2747 } 2748 2749 x = TREE_OPERAND (x, 0); 2750 } 2751 while (x && TREE_CODE (x) == COMPONENT_REF); 2752 } 2753 2754 /* Return nonzero if we can determine the exprs corresponding to memrefs 2755 X and Y and they do not overlap. 2756 If LOOP_VARIANT is set, skip offset-based disambiguation */ 2757 2758 int 2759 nonoverlapping_memrefs_p (const_rtx x, const_rtx y, bool loop_invariant) 2760 { 2761 tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y); 2762 rtx rtlx, rtly; 2763 rtx basex, basey; 2764 bool moffsetx_known_p, moffsety_known_p; 2765 poly_int64 moffsetx = 0, moffsety = 0; 2766 poly_int64 offsetx = 0, offsety = 0, sizex, sizey; 2767 2768 /* Unless both have exprs, we can't tell anything. */ 2769 if (exprx == 0 || expry == 0) 2770 return 0; 2771 2772 /* For spill-slot accesses make sure we have valid offsets. */ 2773 if ((exprx == get_spill_slot_decl (false) 2774 && ! MEM_OFFSET_KNOWN_P (x)) 2775 || (expry == get_spill_slot_decl (false) 2776 && ! MEM_OFFSET_KNOWN_P (y))) 2777 return 0; 2778 2779 /* If the field reference test failed, look at the DECLs involved. */ 2780 moffsetx_known_p = MEM_OFFSET_KNOWN_P (x); 2781 if (moffsetx_known_p) 2782 moffsetx = MEM_OFFSET (x); 2783 if (TREE_CODE (exprx) == COMPONENT_REF) 2784 { 2785 tree t = decl_for_component_ref (exprx); 2786 if (! t) 2787 return 0; 2788 adjust_offset_for_component_ref (exprx, &moffsetx_known_p, &moffsetx); 2789 exprx = t; 2790 } 2791 2792 moffsety_known_p = MEM_OFFSET_KNOWN_P (y); 2793 if (moffsety_known_p) 2794 moffsety = MEM_OFFSET (y); 2795 if (TREE_CODE (expry) == COMPONENT_REF) 2796 { 2797 tree t = decl_for_component_ref (expry); 2798 if (! t) 2799 return 0; 2800 adjust_offset_for_component_ref (expry, &moffsety_known_p, &moffsety); 2801 expry = t; 2802 } 2803 2804 if (! DECL_P (exprx) || ! DECL_P (expry)) 2805 return 0; 2806 2807 /* If we refer to different gimple registers, or one gimple register 2808 and one non-gimple-register, we know they can't overlap. First, 2809 gimple registers don't have their addresses taken. Now, there 2810 could be more than one stack slot for (different versions of) the 2811 same gimple register, but we can presumably tell they don't 2812 overlap based on offsets from stack base addresses elsewhere. 2813 It's important that we don't proceed to DECL_RTL, because gimple 2814 registers may not pass DECL_RTL_SET_P, and make_decl_rtl won't be 2815 able to do anything about them since no SSA information will have 2816 remained to guide it. */ 2817 if (is_gimple_reg (exprx) || is_gimple_reg (expry)) 2818 return exprx != expry 2819 || (moffsetx_known_p && moffsety_known_p 2820 && MEM_SIZE_KNOWN_P (x) && MEM_SIZE_KNOWN_P (y) 2821 && !offset_overlap_p (moffsety - moffsetx, 2822 MEM_SIZE (x), MEM_SIZE (y))); 2823 2824 /* With invalid code we can end up storing into the constant pool. 2825 Bail out to avoid ICEing when creating RTL for this. 2826 See gfortran.dg/lto/20091028-2_0.f90. */ 2827 if (TREE_CODE (exprx) == CONST_DECL 2828 || TREE_CODE (expry) == CONST_DECL) 2829 return 1; 2830 2831 /* If one decl is known to be a function or label in a function and 2832 the other is some kind of data, they can't overlap. */ 2833 if ((TREE_CODE (exprx) == FUNCTION_DECL 2834 || TREE_CODE (exprx) == LABEL_DECL) 2835 != (TREE_CODE (expry) == FUNCTION_DECL 2836 || TREE_CODE (expry) == LABEL_DECL)) 2837 return 1; 2838 2839 /* If either of the decls doesn't have DECL_RTL set (e.g. marked as 2840 living in multiple places), we can't tell anything. Exception 2841 are FUNCTION_DECLs for which we can create DECL_RTL on demand. */ 2842 if ((!DECL_RTL_SET_P (exprx) && TREE_CODE (exprx) != FUNCTION_DECL) 2843 || (!DECL_RTL_SET_P (expry) && TREE_CODE (expry) != FUNCTION_DECL)) 2844 return 0; 2845 2846 rtlx = DECL_RTL (exprx); 2847 rtly = DECL_RTL (expry); 2848 2849 /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they 2850 can't overlap unless they are the same because we never reuse that part 2851 of the stack frame used for locals for spilled pseudos. */ 2852 if ((!MEM_P (rtlx) || !MEM_P (rtly)) 2853 && ! rtx_equal_p (rtlx, rtly)) 2854 return 1; 2855 2856 /* If we have MEMs referring to different address spaces (which can 2857 potentially overlap), we cannot easily tell from the addresses 2858 whether the references overlap. */ 2859 if (MEM_P (rtlx) && MEM_P (rtly) 2860 && MEM_ADDR_SPACE (rtlx) != MEM_ADDR_SPACE (rtly)) 2861 return 0; 2862 2863 /* Get the base and offsets of both decls. If either is a register, we 2864 know both are and are the same, so use that as the base. The only 2865 we can avoid overlap is if we can deduce that they are nonoverlapping 2866 pieces of that decl, which is very rare. */ 2867 basex = MEM_P (rtlx) ? XEXP (rtlx, 0) : rtlx; 2868 basex = strip_offset_and_add (basex, &offsetx); 2869 2870 basey = MEM_P (rtly) ? XEXP (rtly, 0) : rtly; 2871 basey = strip_offset_and_add (basey, &offsety); 2872 2873 /* If the bases are different, we know they do not overlap if both 2874 are constants or if one is a constant and the other a pointer into the 2875 stack frame. Otherwise a different base means we can't tell if they 2876 overlap or not. */ 2877 if (compare_base_decls (exprx, expry) == 0) 2878 return ((CONSTANT_P (basex) && CONSTANT_P (basey)) 2879 || (CONSTANT_P (basex) && REG_P (basey) 2880 && REGNO_PTR_FRAME_P (REGNO (basey))) 2881 || (CONSTANT_P (basey) && REG_P (basex) 2882 && REGNO_PTR_FRAME_P (REGNO (basex)))); 2883 2884 /* Offset based disambiguation not appropriate for loop invariant */ 2885 if (loop_invariant) 2886 return 0; 2887 2888 /* Offset based disambiguation is OK even if we do not know that the 2889 declarations are necessarily different 2890 (i.e. compare_base_decls (exprx, expry) == -1) */ 2891 2892 sizex = (!MEM_P (rtlx) ? poly_int64 (GET_MODE_SIZE (GET_MODE (rtlx))) 2893 : MEM_SIZE_KNOWN_P (rtlx) ? MEM_SIZE (rtlx) 2894 : -1); 2895 sizey = (!MEM_P (rtly) ? poly_int64 (GET_MODE_SIZE (GET_MODE (rtly))) 2896 : MEM_SIZE_KNOWN_P (rtly) ? MEM_SIZE (rtly) 2897 : -1); 2898 2899 /* If we have an offset for either memref, it can update the values computed 2900 above. */ 2901 if (moffsetx_known_p) 2902 offsetx += moffsetx, sizex -= moffsetx; 2903 if (moffsety_known_p) 2904 offsety += moffsety, sizey -= moffsety; 2905 2906 /* If a memref has both a size and an offset, we can use the smaller size. 2907 We can't do this if the offset isn't known because we must view this 2908 memref as being anywhere inside the DECL's MEM. */ 2909 if (MEM_SIZE_KNOWN_P (x) && moffsetx_known_p) 2910 sizex = MEM_SIZE (x); 2911 if (MEM_SIZE_KNOWN_P (y) && moffsety_known_p) 2912 sizey = MEM_SIZE (y); 2913 2914 return !ranges_maybe_overlap_p (offsetx, sizex, offsety, sizey); 2915 } 2916 2917 /* Helper for true_dependence and canon_true_dependence. 2918 Checks for true dependence: X is read after store in MEM takes place. 2919 2920 If MEM_CANONICALIZED is FALSE, then X_ADDR and MEM_ADDR should be 2921 NULL_RTX, and the canonical addresses of MEM and X are both computed 2922 here. If MEM_CANONICALIZED, then MEM must be already canonicalized. 2923 2924 If X_ADDR is non-NULL, it is used in preference of XEXP (x, 0). 2925 2926 Returns 1 if there is a true dependence, 0 otherwise. */ 2927 2928 static int 2929 true_dependence_1 (const_rtx mem, machine_mode mem_mode, rtx mem_addr, 2930 const_rtx x, rtx x_addr, bool mem_canonicalized) 2931 { 2932 rtx true_mem_addr; 2933 rtx base; 2934 int ret; 2935 2936 gcc_checking_assert (mem_canonicalized ? (mem_addr != NULL_RTX) 2937 : (mem_addr == NULL_RTX && x_addr == NULL_RTX)); 2938 2939 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) 2940 return 1; 2941 2942 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything. 2943 This is used in epilogue deallocation functions, and in cselib. */ 2944 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH) 2945 return 1; 2946 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH) 2947 return 1; 2948 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER 2949 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER) 2950 return 1; 2951 2952 if (! x_addr) 2953 x_addr = XEXP (x, 0); 2954 x_addr = get_addr (x_addr); 2955 2956 if (! mem_addr) 2957 { 2958 mem_addr = XEXP (mem, 0); 2959 if (mem_mode == VOIDmode) 2960 mem_mode = GET_MODE (mem); 2961 } 2962 true_mem_addr = get_addr (mem_addr); 2963 2964 /* Read-only memory is by definition never modified, and therefore can't 2965 conflict with anything. However, don't assume anything when AND 2966 addresses are involved and leave to the code below to determine 2967 dependence. We don't expect to find read-only set on MEM, but 2968 stupid user tricks can produce them, so don't die. */ 2969 if (MEM_READONLY_P (x) 2970 && GET_CODE (x_addr) != AND 2971 && GET_CODE (true_mem_addr) != AND) 2972 return 0; 2973 2974 /* If we have MEMs referring to different address spaces (which can 2975 potentially overlap), we cannot easily tell from the addresses 2976 whether the references overlap. */ 2977 if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x)) 2978 return 1; 2979 2980 base = find_base_term (x_addr); 2981 if (base && (GET_CODE (base) == LABEL_REF 2982 || (GET_CODE (base) == SYMBOL_REF 2983 && CONSTANT_POOL_ADDRESS_P (base)))) 2984 return 0; 2985 2986 rtx mem_base = find_base_term (true_mem_addr); 2987 if (! base_alias_check (x_addr, base, true_mem_addr, mem_base, 2988 GET_MODE (x), mem_mode)) 2989 return 0; 2990 2991 x_addr = canon_rtx (x_addr); 2992 if (!mem_canonicalized) 2993 mem_addr = canon_rtx (true_mem_addr); 2994 2995 if ((ret = memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr, 2996 SIZE_FOR_MODE (x), x_addr, 0)) != -1) 2997 return ret; 2998 2999 if (mems_in_disjoint_alias_sets_p (x, mem)) 3000 return 0; 3001 3002 if (nonoverlapping_memrefs_p (mem, x, false)) 3003 return 0; 3004 3005 return rtx_refs_may_alias_p (x, mem, true); 3006 } 3007 3008 /* True dependence: X is read after store in MEM takes place. */ 3009 3010 int 3011 true_dependence (const_rtx mem, machine_mode mem_mode, const_rtx x) 3012 { 3013 return true_dependence_1 (mem, mem_mode, NULL_RTX, 3014 x, NULL_RTX, /*mem_canonicalized=*/false); 3015 } 3016 3017 /* Canonical true dependence: X is read after store in MEM takes place. 3018 Variant of true_dependence which assumes MEM has already been 3019 canonicalized (hence we no longer do that here). 3020 The mem_addr argument has been added, since true_dependence_1 computed 3021 this value prior to canonicalizing. */ 3022 3023 int 3024 canon_true_dependence (const_rtx mem, machine_mode mem_mode, rtx mem_addr, 3025 const_rtx x, rtx x_addr) 3026 { 3027 return true_dependence_1 (mem, mem_mode, mem_addr, 3028 x, x_addr, /*mem_canonicalized=*/true); 3029 } 3030 3031 /* Returns nonzero if a write to X might alias a previous read from 3032 (or, if WRITEP is true, a write to) MEM. 3033 If X_CANONCALIZED is true, then X_ADDR is the canonicalized address of X, 3034 and X_MODE the mode for that access. 3035 If MEM_CANONICALIZED is true, MEM is canonicalized. */ 3036 3037 static int 3038 write_dependence_p (const_rtx mem, 3039 const_rtx x, machine_mode x_mode, rtx x_addr, 3040 bool mem_canonicalized, bool x_canonicalized, bool writep) 3041 { 3042 rtx mem_addr; 3043 rtx true_mem_addr, true_x_addr; 3044 rtx base; 3045 int ret; 3046 3047 gcc_checking_assert (x_canonicalized 3048 ? (x_addr != NULL_RTX 3049 && (x_mode != VOIDmode || GET_MODE (x) == VOIDmode)) 3050 : (x_addr == NULL_RTX && x_mode == VOIDmode)); 3051 3052 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) 3053 return 1; 3054 3055 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything. 3056 This is used in epilogue deallocation functions. */ 3057 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH) 3058 return 1; 3059 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH) 3060 return 1; 3061 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER 3062 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER) 3063 return 1; 3064 3065 if (!x_addr) 3066 x_addr = XEXP (x, 0); 3067 true_x_addr = get_addr (x_addr); 3068 3069 mem_addr = XEXP (mem, 0); 3070 true_mem_addr = get_addr (mem_addr); 3071 3072 /* A read from read-only memory can't conflict with read-write memory. 3073 Don't assume anything when AND addresses are involved and leave to 3074 the code below to determine dependence. */ 3075 if (!writep 3076 && MEM_READONLY_P (mem) 3077 && GET_CODE (true_x_addr) != AND 3078 && GET_CODE (true_mem_addr) != AND) 3079 return 0; 3080 3081 /* If we have MEMs referring to different address spaces (which can 3082 potentially overlap), we cannot easily tell from the addresses 3083 whether the references overlap. */ 3084 if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x)) 3085 return 1; 3086 3087 base = find_base_term (true_mem_addr); 3088 if (! writep 3089 && base 3090 && (GET_CODE (base) == LABEL_REF 3091 || (GET_CODE (base) == SYMBOL_REF 3092 && CONSTANT_POOL_ADDRESS_P (base)))) 3093 return 0; 3094 3095 rtx x_base = find_base_term (true_x_addr); 3096 if (! base_alias_check (true_x_addr, x_base, true_mem_addr, base, 3097 GET_MODE (x), GET_MODE (mem))) 3098 return 0; 3099 3100 if (!x_canonicalized) 3101 { 3102 x_addr = canon_rtx (true_x_addr); 3103 x_mode = GET_MODE (x); 3104 } 3105 if (!mem_canonicalized) 3106 mem_addr = canon_rtx (true_mem_addr); 3107 3108 if ((ret = memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr, 3109 GET_MODE_SIZE (x_mode), x_addr, 0)) != -1) 3110 return ret; 3111 3112 if (nonoverlapping_memrefs_p (x, mem, false)) 3113 return 0; 3114 3115 return rtx_refs_may_alias_p (x, mem, false); 3116 } 3117 3118 /* Anti dependence: X is written after read in MEM takes place. */ 3119 3120 int 3121 anti_dependence (const_rtx mem, const_rtx x) 3122 { 3123 return write_dependence_p (mem, x, VOIDmode, NULL_RTX, 3124 /*mem_canonicalized=*/false, 3125 /*x_canonicalized*/false, /*writep=*/false); 3126 } 3127 3128 /* Likewise, but we already have a canonicalized MEM, and X_ADDR for X. 3129 Also, consider X in X_MODE (which might be from an enclosing 3130 STRICT_LOW_PART / ZERO_EXTRACT). 3131 If MEM_CANONICALIZED is true, MEM is canonicalized. */ 3132 3133 int 3134 canon_anti_dependence (const_rtx mem, bool mem_canonicalized, 3135 const_rtx x, machine_mode x_mode, rtx x_addr) 3136 { 3137 return write_dependence_p (mem, x, x_mode, x_addr, 3138 mem_canonicalized, /*x_canonicalized=*/true, 3139 /*writep=*/false); 3140 } 3141 3142 /* Output dependence: X is written after store in MEM takes place. */ 3143 3144 int 3145 output_dependence (const_rtx mem, const_rtx x) 3146 { 3147 return write_dependence_p (mem, x, VOIDmode, NULL_RTX, 3148 /*mem_canonicalized=*/false, 3149 /*x_canonicalized*/false, /*writep=*/true); 3150 } 3151 3152 /* Likewise, but we already have a canonicalized MEM, and X_ADDR for X. 3153 Also, consider X in X_MODE (which might be from an enclosing 3154 STRICT_LOW_PART / ZERO_EXTRACT). 3155 If MEM_CANONICALIZED is true, MEM is canonicalized. */ 3156 3157 int 3158 canon_output_dependence (const_rtx mem, bool mem_canonicalized, 3159 const_rtx x, machine_mode x_mode, rtx x_addr) 3160 { 3161 return write_dependence_p (mem, x, x_mode, x_addr, 3162 mem_canonicalized, /*x_canonicalized=*/true, 3163 /*writep=*/true); 3164 } 3165 3166 3167 3168 /* Check whether X may be aliased with MEM. Don't do offset-based 3169 memory disambiguation & TBAA. */ 3170 int 3171 may_alias_p (const_rtx mem, const_rtx x) 3172 { 3173 rtx x_addr, mem_addr; 3174 3175 if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem)) 3176 return 1; 3177 3178 /* (mem:BLK (scratch)) is a special mechanism to conflict with everything. 3179 This is used in epilogue deallocation functions. */ 3180 if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH) 3181 return 1; 3182 if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH) 3183 return 1; 3184 if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER 3185 || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER) 3186 return 1; 3187 3188 x_addr = XEXP (x, 0); 3189 x_addr = get_addr (x_addr); 3190 3191 mem_addr = XEXP (mem, 0); 3192 mem_addr = get_addr (mem_addr); 3193 3194 /* Read-only memory is by definition never modified, and therefore can't 3195 conflict with anything. However, don't assume anything when AND 3196 addresses are involved and leave to the code below to determine 3197 dependence. We don't expect to find read-only set on MEM, but 3198 stupid user tricks can produce them, so don't die. */ 3199 if (MEM_READONLY_P (x) 3200 && GET_CODE (x_addr) != AND 3201 && GET_CODE (mem_addr) != AND) 3202 return 0; 3203 3204 /* If we have MEMs referring to different address spaces (which can 3205 potentially overlap), we cannot easily tell from the addresses 3206 whether the references overlap. */ 3207 if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x)) 3208 return 1; 3209 3210 rtx x_base = find_base_term (x_addr); 3211 rtx mem_base = find_base_term (mem_addr); 3212 if (! base_alias_check (x_addr, x_base, mem_addr, mem_base, 3213 GET_MODE (x), GET_MODE (mem_addr))) 3214 return 0; 3215 3216 if (nonoverlapping_memrefs_p (mem, x, true)) 3217 return 0; 3218 3219 /* TBAA not valid for loop_invarint */ 3220 return rtx_refs_may_alias_p (x, mem, false); 3221 } 3222 3223 void 3224 init_alias_target (void) 3225 { 3226 int i; 3227 3228 if (!arg_base_value) 3229 arg_base_value = gen_rtx_ADDRESS (VOIDmode, 0); 3230 3231 memset (static_reg_base_value, 0, sizeof static_reg_base_value); 3232 3233 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) 3234 /* Check whether this register can hold an incoming pointer 3235 argument. FUNCTION_ARG_REGNO_P tests outgoing register 3236 numbers, so translate if necessary due to register windows. */ 3237 if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i)) 3238 && targetm.hard_regno_mode_ok (i, Pmode)) 3239 static_reg_base_value[i] = arg_base_value; 3240 3241 /* RTL code is required to be consistent about whether it uses the 3242 stack pointer, the frame pointer or the argument pointer to 3243 access a given area of the frame. We can therefore use the 3244 base address to distinguish between the different areas. */ 3245 static_reg_base_value[STACK_POINTER_REGNUM] 3246 = unique_base_value (UNIQUE_BASE_VALUE_SP); 3247 static_reg_base_value[ARG_POINTER_REGNUM] 3248 = unique_base_value (UNIQUE_BASE_VALUE_ARGP); 3249 static_reg_base_value[FRAME_POINTER_REGNUM] 3250 = unique_base_value (UNIQUE_BASE_VALUE_FP); 3251 3252 /* The above rules extend post-reload, with eliminations applying 3253 consistently to each of the three pointers. Cope with cases in 3254 which the frame pointer is eliminated to the hard frame pointer 3255 rather than the stack pointer. */ 3256 if (!HARD_FRAME_POINTER_IS_FRAME_POINTER) 3257 static_reg_base_value[HARD_FRAME_POINTER_REGNUM] 3258 = unique_base_value (UNIQUE_BASE_VALUE_HFP); 3259 } 3260 3261 /* Set MEMORY_MODIFIED when X modifies DATA (that is assumed 3262 to be memory reference. */ 3263 static bool memory_modified; 3264 static void 3265 memory_modified_1 (rtx x, const_rtx pat ATTRIBUTE_UNUSED, void *data) 3266 { 3267 if (MEM_P (x)) 3268 { 3269 if (anti_dependence (x, (const_rtx)data) || output_dependence (x, (const_rtx)data)) 3270 memory_modified = true; 3271 } 3272 } 3273 3274 3275 /* Return true when INSN possibly modify memory contents of MEM 3276 (i.e. address can be modified). */ 3277 bool 3278 memory_modified_in_insn_p (const_rtx mem, const_rtx insn) 3279 { 3280 if (!INSN_P (insn)) 3281 return false; 3282 /* Conservatively assume all non-readonly MEMs might be modified in 3283 calls. */ 3284 if (CALL_P (insn)) 3285 return true; 3286 memory_modified = false; 3287 note_stores (PATTERN (insn), memory_modified_1, CONST_CAST_RTX(mem)); 3288 return memory_modified; 3289 } 3290 3291 /* Initialize the aliasing machinery. Initialize the REG_KNOWN_VALUE 3292 array. */ 3293 3294 void 3295 init_alias_analysis (void) 3296 { 3297 unsigned int maxreg = max_reg_num (); 3298 int changed, pass; 3299 int i; 3300 unsigned int ui; 3301 rtx_insn *insn; 3302 rtx val; 3303 int rpo_cnt; 3304 int *rpo; 3305 3306 timevar_push (TV_ALIAS_ANALYSIS); 3307 3308 vec_safe_grow_cleared (reg_known_value, maxreg - FIRST_PSEUDO_REGISTER); 3309 reg_known_equiv_p = sbitmap_alloc (maxreg - FIRST_PSEUDO_REGISTER); 3310 bitmap_clear (reg_known_equiv_p); 3311 3312 /* If we have memory allocated from the previous run, use it. */ 3313 if (old_reg_base_value) 3314 reg_base_value = old_reg_base_value; 3315 3316 if (reg_base_value) 3317 reg_base_value->truncate (0); 3318 3319 vec_safe_grow_cleared (reg_base_value, maxreg); 3320 3321 new_reg_base_value = XNEWVEC (rtx, maxreg); 3322 reg_seen = sbitmap_alloc (maxreg); 3323 3324 /* The basic idea is that each pass through this loop will use the 3325 "constant" information from the previous pass to propagate alias 3326 information through another level of assignments. 3327 3328 The propagation is done on the CFG in reverse post-order, to propagate 3329 things forward as far as possible in each iteration. 3330 3331 This could get expensive if the assignment chains are long. Maybe 3332 we should throttle the number of iterations, possibly based on 3333 the optimization level or flag_expensive_optimizations. 3334 3335 We could propagate more information in the first pass by making use 3336 of DF_REG_DEF_COUNT to determine immediately that the alias information 3337 for a pseudo is "constant". 3338 3339 A program with an uninitialized variable can cause an infinite loop 3340 here. Instead of doing a full dataflow analysis to detect such problems 3341 we just cap the number of iterations for the loop. 3342 3343 The state of the arrays for the set chain in question does not matter 3344 since the program has undefined behavior. */ 3345 3346 rpo = XNEWVEC (int, n_basic_blocks_for_fn (cfun)); 3347 rpo_cnt = pre_and_rev_post_order_compute (NULL, rpo, false); 3348 3349 /* The prologue/epilogue insns are not threaded onto the 3350 insn chain until after reload has completed. Thus, 3351 there is no sense wasting time checking if INSN is in 3352 the prologue/epilogue until after reload has completed. */ 3353 bool could_be_prologue_epilogue = ((targetm.have_prologue () 3354 || targetm.have_epilogue ()) 3355 && reload_completed); 3356 3357 pass = 0; 3358 do 3359 { 3360 /* Assume nothing will change this iteration of the loop. */ 3361 changed = 0; 3362 3363 /* We want to assign the same IDs each iteration of this loop, so 3364 start counting from one each iteration of the loop. */ 3365 unique_id = 1; 3366 3367 /* We're at the start of the function each iteration through the 3368 loop, so we're copying arguments. */ 3369 copying_arguments = true; 3370 3371 /* Wipe the potential alias information clean for this pass. */ 3372 memset (new_reg_base_value, 0, maxreg * sizeof (rtx)); 3373 3374 /* Wipe the reg_seen array clean. */ 3375 bitmap_clear (reg_seen); 3376 3377 /* Initialize the alias information for this pass. */ 3378 for (i = 0; i < FIRST_PSEUDO_REGISTER; i++) 3379 if (static_reg_base_value[i] 3380 /* Don't treat the hard frame pointer as special if we 3381 eliminated the frame pointer to the stack pointer instead. */ 3382 && !(i == HARD_FRAME_POINTER_REGNUM 3383 && reload_completed 3384 && !frame_pointer_needed 3385 && targetm.can_eliminate (FRAME_POINTER_REGNUM, 3386 STACK_POINTER_REGNUM))) 3387 { 3388 new_reg_base_value[i] = static_reg_base_value[i]; 3389 bitmap_set_bit (reg_seen, i); 3390 } 3391 3392 /* Walk the insns adding values to the new_reg_base_value array. */ 3393 for (i = 0; i < rpo_cnt; i++) 3394 { 3395 basic_block bb = BASIC_BLOCK_FOR_FN (cfun, rpo[i]); 3396 FOR_BB_INSNS (bb, insn) 3397 { 3398 if (NONDEBUG_INSN_P (insn)) 3399 { 3400 rtx note, set; 3401 3402 if (could_be_prologue_epilogue 3403 && prologue_epilogue_contains (insn)) 3404 continue; 3405 3406 /* If this insn has a noalias note, process it, Otherwise, 3407 scan for sets. A simple set will have no side effects 3408 which could change the base value of any other register. */ 3409 3410 if (GET_CODE (PATTERN (insn)) == SET 3411 && REG_NOTES (insn) != 0 3412 && find_reg_note (insn, REG_NOALIAS, NULL_RTX)) 3413 record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL); 3414 else 3415 note_stores (PATTERN (insn), record_set, NULL); 3416 3417 set = single_set (insn); 3418 3419 if (set != 0 3420 && REG_P (SET_DEST (set)) 3421 && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER) 3422 { 3423 unsigned int regno = REGNO (SET_DEST (set)); 3424 rtx src = SET_SRC (set); 3425 rtx t; 3426 3427 note = find_reg_equal_equiv_note (insn); 3428 if (note && REG_NOTE_KIND (note) == REG_EQUAL 3429 && DF_REG_DEF_COUNT (regno) != 1) 3430 note = NULL_RTX; 3431 3432 poly_int64 offset; 3433 if (note != NULL_RTX 3434 && GET_CODE (XEXP (note, 0)) != EXPR_LIST 3435 && ! rtx_varies_p (XEXP (note, 0), 1) 3436 && ! reg_overlap_mentioned_p (SET_DEST (set), 3437 XEXP (note, 0))) 3438 { 3439 set_reg_known_value (regno, XEXP (note, 0)); 3440 set_reg_known_equiv_p (regno, 3441 REG_NOTE_KIND (note) == REG_EQUIV); 3442 } 3443 else if (DF_REG_DEF_COUNT (regno) == 1 3444 && GET_CODE (src) == PLUS 3445 && REG_P (XEXP (src, 0)) 3446 && (t = get_reg_known_value (REGNO (XEXP (src, 0)))) 3447 && poly_int_rtx_p (XEXP (src, 1), &offset)) 3448 { 3449 t = plus_constant (GET_MODE (src), t, offset); 3450 set_reg_known_value (regno, t); 3451 set_reg_known_equiv_p (regno, false); 3452 } 3453 else if (DF_REG_DEF_COUNT (regno) == 1 3454 && ! rtx_varies_p (src, 1)) 3455 { 3456 set_reg_known_value (regno, src); 3457 set_reg_known_equiv_p (regno, false); 3458 } 3459 } 3460 } 3461 else if (NOTE_P (insn) 3462 && NOTE_KIND (insn) == NOTE_INSN_FUNCTION_BEG) 3463 copying_arguments = false; 3464 } 3465 } 3466 3467 /* Now propagate values from new_reg_base_value to reg_base_value. */ 3468 gcc_assert (maxreg == (unsigned int) max_reg_num ()); 3469 3470 for (ui = 0; ui < maxreg; ui++) 3471 { 3472 if (new_reg_base_value[ui] 3473 && new_reg_base_value[ui] != (*reg_base_value)[ui] 3474 && ! rtx_equal_p (new_reg_base_value[ui], (*reg_base_value)[ui])) 3475 { 3476 (*reg_base_value)[ui] = new_reg_base_value[ui]; 3477 changed = 1; 3478 } 3479 } 3480 } 3481 while (changed && ++pass < MAX_ALIAS_LOOP_PASSES); 3482 XDELETEVEC (rpo); 3483 3484 /* Fill in the remaining entries. */ 3485 FOR_EACH_VEC_ELT (*reg_known_value, i, val) 3486 { 3487 int regno = i + FIRST_PSEUDO_REGISTER; 3488 if (! val) 3489 set_reg_known_value (regno, regno_reg_rtx[regno]); 3490 } 3491 3492 /* Clean up. */ 3493 free (new_reg_base_value); 3494 new_reg_base_value = 0; 3495 sbitmap_free (reg_seen); 3496 reg_seen = 0; 3497 timevar_pop (TV_ALIAS_ANALYSIS); 3498 } 3499 3500 /* Equate REG_BASE_VALUE (reg1) to REG_BASE_VALUE (reg2). 3501 Special API for var-tracking pass purposes. */ 3502 3503 void 3504 vt_equate_reg_base_value (const_rtx reg1, const_rtx reg2) 3505 { 3506 (*reg_base_value)[REGNO (reg1)] = REG_BASE_VALUE (reg2); 3507 } 3508 3509 void 3510 end_alias_analysis (void) 3511 { 3512 old_reg_base_value = reg_base_value; 3513 vec_free (reg_known_value); 3514 sbitmap_free (reg_known_equiv_p); 3515 } 3516 3517 void 3518 dump_alias_stats_in_alias_c (FILE *s) 3519 { 3520 fprintf (s, " TBAA oracle: %llu disambiguations %llu queries\n" 3521 " %llu are in alias set 0\n" 3522 " %llu queries asked about the same object\n" 3523 " %llu queries asked about the same alias set\n" 3524 " %llu access volatile\n" 3525 " %llu are dependent in the DAG\n" 3526 " %llu are aritificially in conflict with void *\n", 3527 alias_stats.num_disambiguated, 3528 alias_stats.num_alias_zero + alias_stats.num_same_alias_set 3529 + alias_stats.num_same_objects + alias_stats.num_volatile 3530 + alias_stats.num_dag + alias_stats.num_disambiguated 3531 + alias_stats.num_universal, 3532 alias_stats.num_alias_zero, alias_stats.num_same_alias_set, 3533 alias_stats.num_same_objects, alias_stats.num_volatile, 3534 alias_stats.num_dag, alias_stats.num_universal); 3535 } 3536 #include "gt-alias.h" 3537