1 /* Callgraph based analysis of static variables.
2 Copyright (C) 2004, 2005, 2007, 2008, 2009, 2010
3 Free Software Foundation, Inc.
4 Contributed by Kenneth Zadeck <zadeck@naturalbridge.com>
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it under
9 the terms of the GNU General Public License as published by the Free
10 Software Foundation; either version 3, or (at your option) any later
13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
22 /* This file marks functions as being either const (TREE_READONLY) or
23 pure (DECL_PURE_P). It can also set a variant of these that
24 are allowed to loop indefinitely (DECL_LOOPING_CONST_PURE_P).
26 This must be run after inlining decisions have been made since
27 otherwise, the local sets will not contain information that is
28 consistent with post inlined state. The global sets are not prone
29 to this problem since they are by definition transitive. */
31 /* The code in this module is called by the ipa pass manager. It
32 should be one of the later passes since it's information is used by
33 the rest of the compilation. */
37 #include "coretypes.h"
40 #include "tree-flow.h"
41 #include "tree-inline.h"
42 #include "tree-pass.h"
43 #include "langhooks.h"
44 #include "pointer-set.h"
46 #include "ipa-utils.h"
53 #include "diagnostic.h"
54 #include "gimple-pretty-print.h"
55 #include "langhooks.h"
57 #include "lto-streamer.h"
59 #include "tree-scalar-evolution.h"
63 static struct pointer_set_t *visited_nodes;
65 /* Lattice values for const and pure functions. Everything starts out
66 being const, then may drop to pure and then neither depending on
68 enum pure_const_state_e
75 const char *pure_const_names[3] = {"const", "pure", "neither"};
77 /* Holder for the const_state. There is one of these per function
82 enum pure_const_state_e pure_const_state;
83 /* What user set here; we can be always sure about this. */
84 enum pure_const_state_e state_previously_known;
85 bool looping_previously_known;
87 /* True if the function could possibly infinite loop. There are a
88 lot of ways that this could be determined. We are pretty
89 conservative here. While it is possible to cse pure and const
90 calls, it is not legal to have dce get rid of the call if there
91 is a possibility that the call could infinite loop since this is
92 a behavioral change. */
98 typedef struct funct_state_d * funct_state;
100 /* The storage of the funct_state is abstracted because there is the
101 possibility that it may be desirable to move this to the cgraph
104 /* Array, indexed by cgraph node uid, of function states. */
106 DEF_VEC_P (funct_state);
107 DEF_VEC_ALLOC_P (funct_state, heap);
108 static VEC (funct_state, heap) *funct_state_vec;
110 /* Holders of ipa cgraph hooks: */
111 static struct cgraph_node_hook_list *function_insertion_hook_holder;
112 static struct cgraph_2node_hook_list *node_duplication_hook_holder;
113 static struct cgraph_node_hook_list *node_removal_hook_holder;
115 /* Try to guess if function body will always be visible to compiler
116 when compiling the call and whether compiler will be able
117 to propagate the information by itself. */
120 function_always_visible_to_compiler_p (tree decl)
122 return (!TREE_PUBLIC (decl) || DECL_DECLARED_INLINE_P (decl));
125 /* Emit suggestion about attribute ATTRIB_NAME for DECL. KNOWN_FINITE
126 is true if the function is known to be finite. The diagnostic is
127 controlled by OPTION. WARNED_ABOUT is a pointer_set unique for
128 OPTION, this function may initialize it and it is always returned
131 static struct pointer_set_t *
132 suggest_attribute (int option, tree decl, bool known_finite,
133 struct pointer_set_t *warned_about,
134 const char * attrib_name)
136 if (!option_enabled (option))
138 if (TREE_THIS_VOLATILE (decl)
139 || (known_finite && function_always_visible_to_compiler_p (decl)))
143 warned_about = pointer_set_create ();
144 if (pointer_set_contains (warned_about, decl))
146 pointer_set_insert (warned_about, decl);
147 warning_at (DECL_SOURCE_LOCATION (decl),
150 ? _("function might be candidate for attribute %<%s%>")
151 : _("function might be candidate for attribute %<%s%>"
152 " if it is known to return normally"), attrib_name);
156 /* Emit suggestion about __attribute_((pure)) for DECL. KNOWN_FINITE
157 is true if the function is known to be finite. */
160 warn_function_pure (tree decl, bool known_finite)
162 static struct pointer_set_t *warned_about;
165 = suggest_attribute (OPT_Wsuggest_attribute_pure, decl,
166 known_finite, warned_about, "pure");
169 /* Emit suggestion about __attribute_((const)) for DECL. KNOWN_FINITE
170 is true if the function is known to be finite. */
173 warn_function_const (tree decl, bool known_finite)
175 static struct pointer_set_t *warned_about;
177 = suggest_attribute (OPT_Wsuggest_attribute_const, decl,
178 known_finite, warned_about, "const");
182 warn_function_noreturn (tree decl)
184 static struct pointer_set_t *warned_about;
185 if (!lang_hooks.missing_noreturn_ok_p (decl))
187 = suggest_attribute (OPT_Wsuggest_attribute_noreturn, decl,
188 true, warned_about, "noreturn");
190 /* Init the function state. */
195 free (funct_state_vec);
199 /* Return true if we have a function state for NODE. */
202 has_function_state (struct cgraph_node *node)
205 || VEC_length (funct_state, funct_state_vec) <= (unsigned int)node->uid)
207 return VEC_index (funct_state, funct_state_vec, node->uid) != NULL;
210 /* Return the function state from NODE. */
212 static inline funct_state
213 get_function_state (struct cgraph_node *node)
215 static struct funct_state_d varying
216 = { IPA_NEITHER, IPA_NEITHER, true, true, true };
218 || VEC_length (funct_state, funct_state_vec) <= (unsigned int)node->uid)
219 /* We might want to put correct previously_known state into varying. */
221 return VEC_index (funct_state, funct_state_vec, node->uid);
224 /* Set the function state S for NODE. */
227 set_function_state (struct cgraph_node *node, funct_state s)
230 || VEC_length (funct_state, funct_state_vec) <= (unsigned int)node->uid)
231 VEC_safe_grow_cleared (funct_state, heap, funct_state_vec, node->uid + 1);
232 VEC_replace (funct_state, funct_state_vec, node->uid, s);
235 /* Check to see if the use (or definition when CHECKING_WRITE is true)
236 variable T is legal in a function that is either pure or const. */
239 check_decl (funct_state local,
240 tree t, bool checking_write, bool ipa)
242 /* Do not want to do anything with volatile except mark any
243 function that uses one to be not const or pure. */
244 if (TREE_THIS_VOLATILE (t))
246 local->pure_const_state = IPA_NEITHER;
248 fprintf (dump_file, " Volatile operand is not const/pure");
252 /* Do not care about a local automatic that is not static. */
253 if (!TREE_STATIC (t) && !DECL_EXTERNAL (t))
256 /* If the variable has the "used" attribute, treat it as if it had a
257 been touched by the devil. */
258 if (DECL_PRESERVE_P (t))
260 local->pure_const_state = IPA_NEITHER;
262 fprintf (dump_file, " Used static/global variable is not const/pure\n");
266 /* In IPA mode we are not interested in checking actual loads and stores;
267 they will be processed at propagation time using ipa_ref. */
271 /* Since we have dealt with the locals and params cases above, if we
272 are CHECKING_WRITE, this cannot be a pure or constant
276 local->pure_const_state = IPA_NEITHER;
278 fprintf (dump_file, " static/global memory write is not const/pure\n");
282 if (DECL_EXTERNAL (t) || TREE_PUBLIC (t))
284 /* Readonly reads are safe. */
285 if (TREE_READONLY (t) && !TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (t)))
286 return; /* Read of a constant, do not change the function state. */
290 fprintf (dump_file, " global memory read is not const\n");
291 /* Just a regular read. */
292 if (local->pure_const_state == IPA_CONST)
293 local->pure_const_state = IPA_PURE;
298 /* Compilation level statics can be read if they are readonly
300 if (TREE_READONLY (t))
304 fprintf (dump_file, " static memory read is not const\n");
305 /* Just a regular read. */
306 if (local->pure_const_state == IPA_CONST)
307 local->pure_const_state = IPA_PURE;
312 /* Check to see if the use (or definition when CHECKING_WRITE is true)
313 variable T is legal in a function that is either pure or const. */
316 check_op (funct_state local, tree t, bool checking_write)
318 t = get_base_address (t);
319 if (t && TREE_THIS_VOLATILE (t))
321 local->pure_const_state = IPA_NEITHER;
323 fprintf (dump_file, " Volatile indirect ref is not const/pure\n");
327 && INDIRECT_REF_P (t)
328 && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME
329 && !ptr_deref_may_alias_global_p (TREE_OPERAND (t, 0)))
332 fprintf (dump_file, " Indirect ref to local memory is OK\n");
335 else if (checking_write)
337 local->pure_const_state = IPA_NEITHER;
339 fprintf (dump_file, " Indirect ref write is not const/pure\n");
345 fprintf (dump_file, " Indirect ref read is not const\n");
346 if (local->pure_const_state == IPA_CONST)
347 local->pure_const_state = IPA_PURE;
351 /* compute state based on ECF FLAGS and store to STATE and LOOPING. */
354 state_from_flags (enum pure_const_state_e *state, bool *looping,
355 int flags, bool cannot_lead_to_return)
358 if (flags & ECF_LOOPING_CONST_OR_PURE)
361 if (dump_file && (dump_flags & TDF_DETAILS))
362 fprintf (dump_file, " looping");
364 if (flags & ECF_CONST)
367 if (dump_file && (dump_flags & TDF_DETAILS))
368 fprintf (dump_file, " const\n");
370 else if (flags & ECF_PURE)
373 if (dump_file && (dump_flags & TDF_DETAILS))
374 fprintf (dump_file, " pure\n");
376 else if (cannot_lead_to_return)
380 if (dump_file && (dump_flags & TDF_DETAILS))
381 fprintf (dump_file, " ignoring side effects->pure looping\n");
385 if (dump_file && (dump_flags & TDF_DETAILS))
386 fprintf (dump_file, " neihter\n");
387 *state = IPA_NEITHER;
392 /* Merge STATE and STATE2 and LOOPING and LOOPING2 and store
393 into STATE and LOOPING better of the two variants.
394 Be sure to merge looping correctly. IPA_NEITHER functions
395 have looping 0 even if they don't have to return. */
398 better_state (enum pure_const_state_e *state, bool *looping,
399 enum pure_const_state_e state2, bool looping2)
403 if (*state == IPA_NEITHER)
406 *looping = MIN (*looping, looping2);
408 else if (state2 != IPA_NEITHER)
409 *looping = MIN (*looping, looping2);
412 /* Merge STATE and STATE2 and LOOPING and LOOPING2 and store
413 into STATE and LOOPING worse of the two variants. */
416 worse_state (enum pure_const_state_e *state, bool *looping,
417 enum pure_const_state_e state2, bool looping2)
419 *state = MAX (*state, state2);
420 *looping = MAX (*looping, looping2);
423 /* Recognize special cases of builtins that are by themself not pure or const
424 but function using them is. */
426 special_builtlin_state (enum pure_const_state_e *state, bool *looping,
429 if (DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL)
430 switch (DECL_FUNCTION_CODE (callee))
432 case BUILT_IN_RETURN:
433 case BUILT_IN_UNREACHABLE:
434 case BUILT_IN_ALLOCA:
435 case BUILT_IN_STACK_SAVE:
436 case BUILT_IN_STACK_RESTORE:
437 case BUILT_IN_EH_POINTER:
438 case BUILT_IN_EH_FILTER:
439 case BUILT_IN_UNWIND_RESUME:
440 case BUILT_IN_CXA_END_CLEANUP:
441 case BUILT_IN_EH_COPY_VALUES:
442 case BUILT_IN_FRAME_ADDRESS:
444 case BUILT_IN_APPLY_ARGS:
445 case BUILT_IN_ARGS_INFO:
449 case BUILT_IN_PREFETCH:
457 /* Check the parameters of a function call to CALL_EXPR to see if
458 there are any references in the parameters that are not allowed for
459 pure or const functions. Also check to see if this is either an
460 indirect call, a call outside the compilation unit, or has special
461 attributes that may also effect the purity. The CALL_EXPR node for
462 the entire call expression. */
465 check_call (funct_state local, gimple call, bool ipa)
467 int flags = gimple_call_flags (call);
468 tree callee_t = gimple_call_fndecl (call);
469 bool possibly_throws = stmt_could_throw_p (call);
470 bool possibly_throws_externally = (possibly_throws
471 && stmt_can_throw_external (call));
476 for (i = 0; i < gimple_num_ops (call); i++)
477 if (gimple_op (call, i)
478 && tree_could_throw_p (gimple_op (call, i)))
480 if (possibly_throws && cfun->can_throw_non_call_exceptions)
483 fprintf (dump_file, " operand can throw; looping\n");
484 local->looping = true;
486 if (possibly_throws_externally)
489 fprintf (dump_file, " operand can throw externally\n");
490 local->can_throw = true;
495 /* The const and pure flags are set by a variety of places in the
496 compiler (including here). If someone has already set the flags
497 for the callee, (such as for some of the builtins) we will use
498 them, otherwise we will compute our own information.
500 Const and pure functions have less clobber effects than other
501 functions so we process these first. Otherwise if it is a call
502 outside the compilation unit or an indirect call we punt. This
503 leaves local calls which will be processed by following the call
507 enum pure_const_state_e call_state;
510 if (special_builtlin_state (&call_state, &call_looping, callee_t))
512 worse_state (&local->pure_const_state, &local->looping,
513 call_state, call_looping);
516 /* When bad things happen to bad functions, they cannot be const
518 if (setjmp_call_p (callee_t))
521 fprintf (dump_file, " setjmp is not const/pure\n");
522 local->looping = true;
523 local->pure_const_state = IPA_NEITHER;
526 if (DECL_BUILT_IN_CLASS (callee_t) == BUILT_IN_NORMAL)
527 switch (DECL_FUNCTION_CODE (callee_t))
529 case BUILT_IN_LONGJMP:
530 case BUILT_IN_NONLOCAL_GOTO:
532 fprintf (dump_file, " longjmp and nonlocal goto is not const/pure\n");
533 local->pure_const_state = IPA_NEITHER;
534 local->looping = true;
541 /* When not in IPA mode, we can still handle self recursion. */
542 if (!ipa && callee_t == current_function_decl)
545 fprintf (dump_file, " Recursive call can loop.\n");
546 local->looping = true;
548 /* Either calle is unknown or we are doing local analysis.
549 Look to see if there are any bits available for the callee (such as by
550 declaration or because it is builtin) and process solely on the basis of
554 enum pure_const_state_e call_state;
556 if (possibly_throws && cfun->can_throw_non_call_exceptions)
559 fprintf (dump_file, " can throw; looping\n");
560 local->looping = true;
562 if (possibly_throws_externally)
566 fprintf (dump_file, " can throw externally to lp %i\n",
567 lookup_stmt_eh_lp (call));
569 fprintf (dump_file, " callee:%s\n",
570 IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (callee_t)));
572 local->can_throw = true;
574 if (dump_file && (dump_flags & TDF_DETAILS))
575 fprintf (dump_file, " checking flags for call:");
576 state_from_flags (&call_state, &call_looping, flags,
577 ((flags & (ECF_NORETURN | ECF_NOTHROW))
578 == (ECF_NORETURN | ECF_NOTHROW))
579 || (!flag_exceptions && (flags & ECF_NORETURN)));
580 worse_state (&local->pure_const_state, &local->looping,
581 call_state, call_looping);
583 /* Direct functions calls are handled by IPA propagation. */
586 /* Wrapper around check_decl for loads in local more. */
589 check_load (gimple stmt ATTRIBUTE_UNUSED, tree op, void *data)
592 check_decl ((funct_state)data, op, false, false);
594 check_op ((funct_state)data, op, false);
598 /* Wrapper around check_decl for stores in local more. */
601 check_store (gimple stmt ATTRIBUTE_UNUSED, tree op, void *data)
604 check_decl ((funct_state)data, op, true, false);
606 check_op ((funct_state)data, op, true);
610 /* Wrapper around check_decl for loads in ipa mode. */
613 check_ipa_load (gimple stmt ATTRIBUTE_UNUSED, tree op, void *data)
616 check_decl ((funct_state)data, op, false, true);
618 check_op ((funct_state)data, op, false);
622 /* Wrapper around check_decl for stores in ipa mode. */
625 check_ipa_store (gimple stmt ATTRIBUTE_UNUSED, tree op, void *data)
628 check_decl ((funct_state)data, op, true, true);
630 check_op ((funct_state)data, op, true);
634 /* Look into pointer pointed to by GSIP and figure out what interesting side
637 check_stmt (gimple_stmt_iterator *gsip, funct_state local, bool ipa)
639 gimple stmt = gsi_stmt (*gsip);
642 if (is_gimple_debug (stmt))
647 fprintf (dump_file, " scanning: ");
648 print_gimple_stmt (dump_file, stmt, 0, 0);
651 /* Look for loads and stores. */
652 walk_stmt_load_store_ops (stmt, local,
653 ipa ? check_ipa_load : check_load,
654 ipa ? check_ipa_store : check_store);
656 if (gimple_code (stmt) != GIMPLE_CALL
657 && stmt_could_throw_p (stmt))
659 if (cfun->can_throw_non_call_exceptions)
662 fprintf (dump_file, " can throw; looping");
663 local->looping = true;
665 if (stmt_can_throw_external (stmt))
668 fprintf (dump_file, " can throw externally");
669 local->can_throw = true;
672 switch (gimple_code (stmt))
675 check_call (local, stmt, ipa);
678 if (DECL_NONLOCAL (gimple_label_label (stmt)))
679 /* Target of long jump. */
682 fprintf (dump_file, " nonlocal label is not const/pure");
683 local->pure_const_state = IPA_NEITHER;
687 for (i = 0; i < gimple_asm_nclobbers (stmt); i++)
689 tree op = gimple_asm_clobber_op (stmt, i);
690 if (strcmp (TREE_STRING_POINTER (TREE_VALUE (op)), "memory") == 0)
693 fprintf (dump_file, " memory asm clobber is not const/pure");
694 /* Abandon all hope, ye who enter here. */
695 local->pure_const_state = IPA_NEITHER;
698 if (gimple_asm_volatile_p (stmt))
701 fprintf (dump_file, " volatile is not const/pure");
702 /* Abandon all hope, ye who enter here. */
703 local->pure_const_state = IPA_NEITHER;
704 local->looping = true;
713 /* This is the main routine for finding the reference patterns for
714 global variables within a function FN. */
717 analyze_function (struct cgraph_node *fn, bool ipa)
719 tree decl = fn->decl;
720 tree old_decl = current_function_decl;
722 basic_block this_block;
724 l = XCNEW (struct funct_state_d);
725 l->pure_const_state = IPA_CONST;
726 l->state_previously_known = IPA_NEITHER;
727 l->looping_previously_known = true;
729 l->can_throw = false;
733 fprintf (dump_file, "\n\n local analysis of %s\n ",
734 cgraph_node_name (fn));
737 push_cfun (DECL_STRUCT_FUNCTION (decl));
738 current_function_decl = decl;
740 FOR_EACH_BB (this_block)
742 gimple_stmt_iterator gsi;
743 struct walk_stmt_info wi;
745 memset (&wi, 0, sizeof(wi));
746 for (gsi = gsi_start_bb (this_block);
750 check_stmt (&gsi, l, ipa);
751 if (l->pure_const_state == IPA_NEITHER && l->looping && l->can_throw)
757 if (l->pure_const_state != IPA_NEITHER)
759 /* Const functions cannot have back edges (an
760 indication of possible infinite loop side
762 if (mark_dfs_back_edges ())
764 /* Preheaders are needed for SCEV to work.
765 Simple lateches and recorded exits improve chances that loop will
766 proved to be finite in testcases such as in loop-15.c and loop-24.c */
767 loop_optimizer_init (LOOPS_NORMAL
768 | LOOPS_HAVE_RECORDED_EXITS);
769 if (dump_file && (dump_flags & TDF_DETAILS))
770 flow_loops_dump (dump_file, NULL, 0);
771 if (mark_irreducible_loops ())
774 fprintf (dump_file, " has irreducible loops\n");
782 FOR_EACH_LOOP (li, loop, 0)
783 if (!finite_loop_p (loop))
786 fprintf (dump_file, " can not prove finiteness of loop %i\n", loop->num);
792 loop_optimizer_finalize ();
796 if (dump_file && (dump_flags & TDF_DETAILS))
797 fprintf (dump_file, " checking previously known:");
798 state_from_flags (&l->state_previously_known, &l->looping_previously_known,
799 flags_from_decl_or_type (fn->decl),
800 cgraph_node_cannot_return (fn));
802 better_state (&l->pure_const_state, &l->looping,
803 l->state_previously_known,
804 l->looping_previously_known);
805 if (TREE_NOTHROW (decl))
806 l->can_throw = false;
809 current_function_decl = old_decl;
813 fprintf (dump_file, "Function is locally looping.\n");
815 fprintf (dump_file, "Function is locally throwing.\n");
816 if (l->pure_const_state == IPA_CONST)
817 fprintf (dump_file, "Function is locally const.\n");
818 if (l->pure_const_state == IPA_PURE)
819 fprintf (dump_file, "Function is locally pure.\n");
824 /* Called when new function is inserted to callgraph late. */
826 add_new_function (struct cgraph_node *node, void *data ATTRIBUTE_UNUSED)
828 if (cgraph_function_body_availability (node) < AVAIL_OVERWRITABLE)
830 /* There are some shared nodes, in particular the initializers on
831 static declarations. We do not need to scan them more than once
832 since all we would be interested in are the addressof
834 visited_nodes = pointer_set_create ();
835 if (cgraph_function_body_availability (node) > AVAIL_OVERWRITABLE)
836 set_function_state (node, analyze_function (node, true));
837 pointer_set_destroy (visited_nodes);
838 visited_nodes = NULL;
841 /* Called when new clone is inserted to callgraph late. */
844 duplicate_node_data (struct cgraph_node *src, struct cgraph_node *dst,
845 void *data ATTRIBUTE_UNUSED)
847 if (has_function_state (src))
849 funct_state l = XNEW (struct funct_state_d);
850 gcc_assert (!has_function_state (dst));
851 memcpy (l, get_function_state (src), sizeof (*l));
852 set_function_state (dst, l);
856 /* Called when new clone is inserted to callgraph late. */
859 remove_node_data (struct cgraph_node *node, void *data ATTRIBUTE_UNUSED)
861 if (has_function_state (node))
863 free (get_function_state (node));
864 set_function_state (node, NULL);
870 register_hooks (void)
872 static bool init_p = false;
879 node_removal_hook_holder =
880 cgraph_add_node_removal_hook (&remove_node_data, NULL);
881 node_duplication_hook_holder =
882 cgraph_add_node_duplication_hook (&duplicate_node_data, NULL);
883 function_insertion_hook_holder =
884 cgraph_add_function_insertion_hook (&add_new_function, NULL);
888 /* Analyze each function in the cgraph to see if it is locally PURE or
892 generate_summary (void)
894 struct cgraph_node *node;
898 /* There are some shared nodes, in particular the initializers on
899 static declarations. We do not need to scan them more than once
900 since all we would be interested in are the addressof
902 visited_nodes = pointer_set_create ();
904 /* Process all of the functions.
906 We process AVAIL_OVERWRITABLE functions. We can not use the results
907 by default, but the info can be used at LTO with -fwhole-program or
908 when function got clonned and the clone is AVAILABLE. */
910 for (node = cgraph_nodes; node; node = node->next)
911 if (cgraph_function_body_availability (node) >= AVAIL_OVERWRITABLE)
912 set_function_state (node, analyze_function (node, true));
914 pointer_set_destroy (visited_nodes);
915 visited_nodes = NULL;
919 /* Serialize the ipa info for lto. */
922 pure_const_write_summary (cgraph_node_set set,
923 varpool_node_set vset ATTRIBUTE_UNUSED)
925 struct cgraph_node *node;
926 struct lto_simple_output_block *ob
927 = lto_create_simple_output_block (LTO_section_ipa_pure_const);
928 unsigned int count = 0;
929 cgraph_node_set_iterator csi;
931 for (csi = csi_start (set); !csi_end_p (csi); csi_next (&csi))
933 node = csi_node (csi);
934 if (node->analyzed && has_function_state (node))
938 lto_output_uleb128_stream (ob->main_stream, count);
940 /* Process all of the functions. */
941 for (csi = csi_start (set); !csi_end_p (csi); csi_next (&csi))
943 node = csi_node (csi);
944 if (node->analyzed && has_function_state (node))
946 struct bitpack_d *bp;
949 lto_cgraph_encoder_t encoder;
951 fs = get_function_state (node);
953 encoder = ob->decl_state->cgraph_node_encoder;
954 node_ref = lto_cgraph_encoder_encode (encoder, node);
955 lto_output_uleb128_stream (ob->main_stream, node_ref);
957 /* Note that flags will need to be read in the opposite
958 order as we are pushing the bitflags into FLAGS. */
959 bp = bitpack_create ();
960 bp_pack_value (bp, fs->pure_const_state, 2);
961 bp_pack_value (bp, fs->state_previously_known, 2);
962 bp_pack_value (bp, fs->looping_previously_known, 1);
963 bp_pack_value (bp, fs->looping, 1);
964 bp_pack_value (bp, fs->can_throw, 1);
965 lto_output_bitpack (ob->main_stream, bp);
970 lto_destroy_simple_output_block (ob);
974 /* Deserialize the ipa info for lto. */
977 pure_const_read_summary (void)
979 struct lto_file_decl_data **file_data_vec = lto_get_file_decl_data ();
980 struct lto_file_decl_data *file_data;
984 while ((file_data = file_data_vec[j++]))
988 struct lto_input_block *ib
989 = lto_create_simple_input_block (file_data,
990 LTO_section_ipa_pure_const,
995 unsigned int count = lto_input_uleb128 (ib);
997 for (i = 0; i < count; i++)
1000 struct cgraph_node *node;
1001 struct bitpack_d *bp;
1003 lto_cgraph_encoder_t encoder;
1005 fs = XCNEW (struct funct_state_d);
1006 index = lto_input_uleb128 (ib);
1007 encoder = file_data->cgraph_node_encoder;
1008 node = lto_cgraph_encoder_deref (encoder, index);
1009 set_function_state (node, fs);
1011 /* Note that the flags must be read in the opposite
1012 order in which they were written (the bitflags were
1013 pushed into FLAGS). */
1014 bp = lto_input_bitpack (ib);
1015 fs->pure_const_state
1016 = (enum pure_const_state_e) bp_unpack_value (bp, 2);
1017 fs->state_previously_known
1018 = (enum pure_const_state_e) bp_unpack_value (bp, 2);
1019 fs->looping_previously_known = bp_unpack_value (bp, 1);
1020 fs->looping = bp_unpack_value (bp, 1);
1021 fs->can_throw = bp_unpack_value (bp, 1);
1024 int flags = flags_from_decl_or_type (node->decl);
1025 fprintf (dump_file, "Read info for %s/%i ",
1026 cgraph_node_name (node),
1028 if (flags & ECF_CONST)
1029 fprintf (dump_file, " const");
1030 if (flags & ECF_PURE)
1031 fprintf (dump_file, " pure");
1032 if (flags & ECF_NOTHROW)
1033 fprintf (dump_file, " nothrow");
1034 fprintf (dump_file, "\n pure const state: %s\n",
1035 pure_const_names[fs->pure_const_state]);
1036 fprintf (dump_file, " previously known state: %s\n",
1037 pure_const_names[fs->looping_previously_known]);
1039 fprintf (dump_file," function is locally looping\n");
1040 if (fs->looping_previously_known)
1041 fprintf (dump_file," function is previously known looping\n");
1043 fprintf (dump_file," function is locally throwing\n");
1045 bitpack_delete (bp);
1048 lto_destroy_simple_input_block (file_data,
1049 LTO_section_ipa_pure_const,
1057 ignore_edge (struct cgraph_edge *e)
1059 return (!e->can_throw_external);
1062 /* Return true if NODE is self recursive function. */
1065 self_recursive_p (struct cgraph_node *node)
1067 struct cgraph_edge *e;
1068 for (e = node->callees; e; e = e->next_callee)
1069 if (e->callee == node)
1074 /* Produce transitive closure over the callgraph and compute pure/const
1078 propagate_pure_const (void)
1080 struct cgraph_node *node;
1081 struct cgraph_node *w;
1082 struct cgraph_node **order =
1083 XCNEWVEC (struct cgraph_node *, cgraph_n_nodes);
1086 struct ipa_dfs_info * w_info;
1088 order_pos = ipa_utils_reduced_inorder (order, true, false, NULL);
1091 dump_cgraph (dump_file);
1092 ipa_utils_print_order(dump_file, "reduced", order, order_pos);
1095 /* Propagate the local information thru the call graph to produce
1096 the global information. All the nodes within a cycle will have
1097 the same info so we collapse cycles first. Then we can do the
1098 propagation in one pass from the leaves to the roots. */
1099 for (i = 0; i < order_pos; i++ )
1101 enum pure_const_state_e pure_const_state = IPA_CONST;
1102 bool looping = false;
1106 if (dump_file && (dump_flags & TDF_DETAILS))
1107 fprintf (dump_file, "Starting cycle\n");
1109 /* Find the worst state for any node in the cycle. */
1111 while (w && pure_const_state != IPA_NEITHER)
1113 struct cgraph_edge *e;
1114 struct cgraph_edge *ie;
1116 struct ipa_ref *ref;
1118 funct_state w_l = get_function_state (w);
1119 if (dump_file && (dump_flags & TDF_DETAILS))
1120 fprintf (dump_file, " Visiting %s/%i state:%s looping %i\n",
1121 cgraph_node_name (w),
1123 pure_const_names[w_l->pure_const_state],
1126 /* First merge in function body properties. */
1127 worse_state (&pure_const_state, &looping,
1128 w_l->pure_const_state, w_l->looping);
1129 if (pure_const_state == IPA_NEITHER)
1132 /* For overwritable nodes we can not assume anything. */
1133 if (cgraph_function_body_availability (w) == AVAIL_OVERWRITABLE)
1135 worse_state (&pure_const_state, &looping,
1136 w_l->state_previously_known,
1137 w_l->looping_previously_known);
1138 if (dump_file && (dump_flags & TDF_DETAILS))
1141 " Overwritable. state %s looping %i\n",
1142 pure_const_names[w_l->state_previously_known],
1143 w_l->looping_previously_known);
1150 /* We consider recursive cycles as possibly infinite.
1151 This might be relaxed since infinite recursion leads to stack
1156 /* Now walk the edges and merge in callee properties. */
1157 for (e = w->callees; e; e = e->next_callee)
1159 struct cgraph_node *y = e->callee;
1160 enum pure_const_state_e edge_state = IPA_CONST;
1161 bool edge_looping = false;
1163 if (dump_file && (dump_flags & TDF_DETAILS))
1167 cgraph_node_name (e->callee),
1170 if (cgraph_function_body_availability (y) > AVAIL_OVERWRITABLE)
1172 funct_state y_l = get_function_state (y);
1173 if (dump_file && (dump_flags & TDF_DETAILS))
1176 " state:%s looping:%i\n",
1177 pure_const_names[y_l->pure_const_state],
1180 if (y_l->pure_const_state > IPA_PURE
1181 && cgraph_edge_cannot_lead_to_return (e))
1183 if (dump_file && (dump_flags & TDF_DETAILS))
1185 " Ignoring side effects"
1186 " -> pure, looping\n");
1187 edge_state = IPA_PURE;
1188 edge_looping = true;
1192 edge_state = y_l->pure_const_state;
1193 edge_looping = y_l->looping;
1196 else if (special_builtlin_state (&edge_state, &edge_looping,
1200 state_from_flags (&edge_state, &edge_looping,
1201 flags_from_decl_or_type (y->decl),
1202 cgraph_edge_cannot_lead_to_return (e));
1204 /* Merge the results with what we already know. */
1205 better_state (&edge_state, &edge_looping,
1206 w_l->state_previously_known,
1207 w_l->looping_previously_known);
1208 worse_state (&pure_const_state, &looping,
1209 edge_state, edge_looping);
1210 if (pure_const_state == IPA_NEITHER)
1213 if (pure_const_state == IPA_NEITHER)
1216 /* Now process the indirect call. */
1217 for (ie = node->indirect_calls; ie; ie = ie->next_callee)
1219 enum pure_const_state_e edge_state = IPA_CONST;
1220 bool edge_looping = false;
1222 if (dump_file && (dump_flags & TDF_DETAILS))
1223 fprintf (dump_file, " Indirect call");
1224 state_from_flags (&edge_state, &edge_looping,
1225 ie->indirect_info->ecf_flags,
1226 cgraph_edge_cannot_lead_to_return (ie));
1227 /* Merge the results with what we already know. */
1228 better_state (&edge_state, &edge_looping,
1229 w_l->state_previously_known,
1230 w_l->looping_previously_known);
1231 worse_state (&pure_const_state, &looping,
1232 edge_state, edge_looping);
1233 if (pure_const_state == IPA_NEITHER)
1236 if (pure_const_state == IPA_NEITHER)
1239 /* And finally all loads and stores. */
1240 for (i = 0; ipa_ref_list_reference_iterate (&node->ref_list, i, ref); i++)
1242 enum pure_const_state_e ref_state = IPA_CONST;
1243 bool ref_looping = false;
1247 /* readonly reads are safe. */
1248 if (TREE_READONLY (ipa_ref_varpool_node (ref)->decl))
1250 if (dump_file && (dump_flags & TDF_DETAILS))
1251 fprintf (dump_file, " nonreadonly global var read\n");
1252 ref_state = IPA_PURE;
1255 if (ipa_ref_cannot_lead_to_return (ref))
1257 ref_state = IPA_NEITHER;
1258 if (dump_file && (dump_flags & TDF_DETAILS))
1259 fprintf (dump_file, " global var write\n");
1264 better_state (&ref_state, &ref_looping,
1265 w_l->state_previously_known,
1266 w_l->looping_previously_known);
1267 worse_state (&pure_const_state, &looping,
1268 ref_state, ref_looping);
1269 if (pure_const_state == IPA_NEITHER)
1272 w_info = (struct ipa_dfs_info *) w->aux;
1273 w = w_info->next_cycle;
1275 if (dump_file && (dump_flags & TDF_DETAILS))
1276 fprintf (dump_file, "Result %s looping %i\n",
1277 pure_const_names [pure_const_state],
1280 /* Copy back the region's pure_const_state which is shared by
1281 all nodes in the region. */
1285 funct_state w_l = get_function_state (w);
1286 enum pure_const_state_e this_state = pure_const_state;
1287 bool this_looping = looping;
1289 if (w_l->state_previously_known != IPA_NEITHER
1290 && this_state > w_l->state_previously_known)
1292 this_state = w_l->state_previously_known;
1293 this_looping |= w_l->looping_previously_known;
1295 if (!this_looping && self_recursive_p (w))
1296 this_looping = true;
1297 if (!w_l->looping_previously_known)
1298 this_looping = false;
1300 /* All nodes within a cycle share the same info. */
1301 w_l->pure_const_state = this_state;
1302 w_l->looping = this_looping;
1307 if (!TREE_READONLY (w->decl))
1309 warn_function_const (w->decl, !this_looping);
1311 fprintf (dump_file, "Function found to be %sconst: %s\n",
1312 this_looping ? "looping " : "",
1313 cgraph_node_name (w));
1315 cgraph_set_readonly_flag (w, true);
1316 cgraph_set_looping_const_or_pure_flag (w, this_looping);
1320 if (!DECL_PURE_P (w->decl))
1322 warn_function_pure (w->decl, !this_looping);
1324 fprintf (dump_file, "Function found to be %spure: %s\n",
1325 this_looping ? "looping " : "",
1326 cgraph_node_name (w));
1328 cgraph_set_pure_flag (w, true);
1329 cgraph_set_looping_const_or_pure_flag (w, this_looping);
1335 w_info = (struct ipa_dfs_info *) w->aux;
1336 w = w_info->next_cycle;
1341 for (node = cgraph_nodes; node; node = node->next)
1343 /* Get rid of the aux information. */
1346 w_info = (struct ipa_dfs_info *) node->aux;
1355 /* Produce transitive closure over the callgraph and compute nothrow
1359 propagate_nothrow (void)
1361 struct cgraph_node *node;
1362 struct cgraph_node *w;
1363 struct cgraph_node **order =
1364 XCNEWVEC (struct cgraph_node *, cgraph_n_nodes);
1367 struct ipa_dfs_info * w_info;
1369 order_pos = ipa_utils_reduced_inorder (order, true, false, ignore_edge);
1372 dump_cgraph (dump_file);
1373 ipa_utils_print_order(dump_file, "reduced for nothrow", order, order_pos);
1376 /* Propagate the local information thru the call graph to produce
1377 the global information. All the nodes within a cycle will have
1378 the same info so we collapse cycles first. Then we can do the
1379 propagation in one pass from the leaves to the roots. */
1380 for (i = 0; i < order_pos; i++ )
1382 bool can_throw = false;
1385 /* Find the worst state for any node in the cycle. */
1389 struct cgraph_edge *e, *ie;
1390 funct_state w_l = get_function_state (w);
1393 || cgraph_function_body_availability (w) == AVAIL_OVERWRITABLE)
1399 for (e = w->callees; e; e = e->next_callee)
1401 struct cgraph_node *y = e->callee;
1403 if (cgraph_function_body_availability (y) > AVAIL_OVERWRITABLE)
1405 funct_state y_l = get_function_state (y);
1409 if (y_l->can_throw && !TREE_NOTHROW (w->decl)
1410 && e->can_throw_external)
1413 else if (e->can_throw_external && !TREE_NOTHROW (y->decl))
1416 for (ie = node->indirect_calls; ie; ie = ie->next_callee)
1417 if (ie->can_throw_external)
1419 w_info = (struct ipa_dfs_info *) w->aux;
1420 w = w_info->next_cycle;
1423 /* Copy back the region's pure_const_state which is shared by
1424 all nodes in the region. */
1428 funct_state w_l = get_function_state (w);
1429 if (!can_throw && !TREE_NOTHROW (w->decl))
1431 struct cgraph_edge *e;
1432 cgraph_set_nothrow_flag (w, true);
1433 for (e = w->callers; e; e = e->next_caller)
1434 e->can_throw_external = false;
1436 fprintf (dump_file, "Function found to be nothrow: %s\n",
1437 cgraph_node_name (w));
1439 else if (can_throw && !TREE_NOTHROW (w->decl))
1440 w_l->can_throw = true;
1441 w_info = (struct ipa_dfs_info *) w->aux;
1442 w = w_info->next_cycle;
1447 for (node = cgraph_nodes; node; node = node->next)
1449 /* Get rid of the aux information. */
1452 w_info = (struct ipa_dfs_info *) node->aux;
1462 /* Produce the global information by preforming a transitive closure
1463 on the local information that was produced by generate_summary. */
1468 struct cgraph_node *node;
1470 cgraph_remove_function_insertion_hook (function_insertion_hook_holder);
1471 cgraph_remove_node_duplication_hook (node_duplication_hook_holder);
1472 cgraph_remove_node_removal_hook (node_removal_hook_holder);
1474 /* Nothrow makes more function to not lead to return and improve
1476 propagate_nothrow ();
1477 propagate_pure_const ();
1480 for (node = cgraph_nodes; node; node = node->next)
1481 if (has_function_state (node))
1482 free (get_function_state (node));
1483 VEC_free (funct_state, heap, funct_state_vec);
1489 gate_pure_const (void)
1491 return (flag_ipa_pure_const
1492 /* Don't bother doing anything if the program has errors. */
1496 struct ipa_opt_pass_d pass_ipa_pure_const =
1500 "pure-const", /* name */
1501 gate_pure_const, /* gate */
1502 propagate, /* execute */
1505 0, /* static_pass_number */
1506 TV_IPA_PURE_CONST, /* tv_id */
1507 0, /* properties_required */
1508 0, /* properties_provided */
1509 0, /* properties_destroyed */
1510 0, /* todo_flags_start */
1511 0 /* todo_flags_finish */
1513 generate_summary, /* generate_summary */
1514 pure_const_write_summary, /* write_summary */
1515 pure_const_read_summary, /* read_summary */
1516 NULL, /* write_optimization_summary */
1517 NULL, /* read_optimization_summary */
1518 NULL, /* stmt_fixup */
1520 NULL, /* function_transform */
1521 NULL /* variable_transform */
1524 /* Return true if function should be skipped for local pure const analysis. */
1527 skip_function_for_local_pure_const (struct cgraph_node *node)
1529 /* Because we do not schedule pass_fixup_cfg over whole program after early optimizations
1530 we must not promote functions that are called by already processed functions. */
1532 if (function_called_by_processed_nodes_p ())
1535 fprintf (dump_file, "Function called in recursive cycle; ignoring\n");
1538 if (cgraph_function_body_availability (node) <= AVAIL_OVERWRITABLE)
1541 fprintf (dump_file, "Function is not available or overwrittable; not analyzing.\n");
1547 /* Simple local pass for pure const discovery reusing the analysis from
1548 ipa_pure_const. This pass is effective when executed together with
1549 other optimization passes in early optimization pass queue. */
1552 local_pure_const (void)
1554 bool changed = false;
1557 struct cgraph_node *node;
1559 node = cgraph_node (current_function_decl);
1560 skip = skip_function_for_local_pure_const (node);
1561 if (!warn_suggest_attribute_const
1562 && !warn_suggest_attribute_pure
1566 /* First do NORETURN discovery. */
1567 if (!skip && !TREE_THIS_VOLATILE (current_function_decl)
1568 && EDGE_COUNT (EXIT_BLOCK_PTR->preds) == 0)
1570 warn_function_noreturn (cfun->decl);
1572 fprintf (dump_file, "Function found to be noreturn: %s\n",
1573 lang_hooks.decl_printable_name (current_function_decl, 2));
1575 /* Update declaration and reduce profile to executed once. */
1576 TREE_THIS_VOLATILE (current_function_decl) = 1;
1577 if (node->frequency > NODE_FREQUENCY_EXECUTED_ONCE)
1578 node->frequency = NODE_FREQUENCY_EXECUTED_ONCE;
1582 l = analyze_function (node, false);
1584 switch (l->pure_const_state)
1587 if (!TREE_READONLY (current_function_decl))
1589 warn_function_const (current_function_decl, !l->looping);
1592 cgraph_set_readonly_flag (node, true);
1593 cgraph_set_looping_const_or_pure_flag (node, l->looping);
1597 fprintf (dump_file, "Function found to be %sconst: %s\n",
1598 l->looping ? "looping " : "",
1599 lang_hooks.decl_printable_name (current_function_decl,
1602 else if (DECL_LOOPING_CONST_OR_PURE_P (current_function_decl)
1607 cgraph_set_looping_const_or_pure_flag (node, false);
1611 fprintf (dump_file, "Function found to be non-looping: %s\n",
1612 lang_hooks.decl_printable_name (current_function_decl,
1618 if (!DECL_PURE_P (current_function_decl))
1622 cgraph_set_pure_flag (node, true);
1623 cgraph_set_looping_const_or_pure_flag (node, l->looping);
1626 warn_function_pure (current_function_decl, !l->looping);
1628 fprintf (dump_file, "Function found to be %spure: %s\n",
1629 l->looping ? "looping " : "",
1630 lang_hooks.decl_printable_name (current_function_decl,
1633 else if (DECL_LOOPING_CONST_OR_PURE_P (current_function_decl)
1638 cgraph_set_looping_const_or_pure_flag (node, false);
1642 fprintf (dump_file, "Function found to be non-looping: %s\n",
1643 lang_hooks.decl_printable_name (current_function_decl,
1651 if (!l->can_throw && !TREE_NOTHROW (current_function_decl))
1653 struct cgraph_edge *e;
1655 cgraph_set_nothrow_flag (node, true);
1656 for (e = node->callers; e; e = e->next_caller)
1657 e->can_throw_external = false;
1660 fprintf (dump_file, "Function found to be nothrow: %s\n",
1661 lang_hooks.decl_printable_name (current_function_decl,
1667 return execute_fixup_cfg ();
1672 struct gimple_opt_pass pass_local_pure_const =
1676 "local-pure-const", /* name */
1677 gate_pure_const, /* gate */
1678 local_pure_const, /* execute */
1681 0, /* static_pass_number */
1682 TV_IPA_PURE_CONST, /* tv_id */
1683 0, /* properties_required */
1684 0, /* properties_provided */
1685 0, /* properties_destroyed */
1686 0, /* todo_flags_start */
1687 0 /* todo_flags_finish */