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 /* State used when we know nothing about function. */
99 static struct funct_state_d varying_state
100 = { IPA_NEITHER, IPA_NEITHER, true, true, true };
103 typedef struct funct_state_d * funct_state;
105 /* The storage of the funct_state is abstracted because there is the
106 possibility that it may be desirable to move this to the cgraph
109 /* Array, indexed by cgraph node uid, of function states. */
111 DEF_VEC_P (funct_state);
112 DEF_VEC_ALLOC_P (funct_state, heap);
113 static VEC (funct_state, heap) *funct_state_vec;
115 /* Holders of ipa cgraph hooks: */
116 static struct cgraph_node_hook_list *function_insertion_hook_holder;
117 static struct cgraph_2node_hook_list *node_duplication_hook_holder;
118 static struct cgraph_node_hook_list *node_removal_hook_holder;
120 /* Try to guess if function body will always be visible to compiler
121 when compiling the call and whether compiler will be able
122 to propagate the information by itself. */
125 function_always_visible_to_compiler_p (tree decl)
127 return (!TREE_PUBLIC (decl) || DECL_DECLARED_INLINE_P (decl));
130 /* Emit suggestion about attribute ATTRIB_NAME for DECL. KNOWN_FINITE
131 is true if the function is known to be finite. The diagnostic is
132 controlled by OPTION. WARNED_ABOUT is a pointer_set unique for
133 OPTION, this function may initialize it and it is always returned
136 static struct pointer_set_t *
137 suggest_attribute (int option, tree decl, bool known_finite,
138 struct pointer_set_t *warned_about,
139 const char * attrib_name)
141 if (!option_enabled (option))
143 if (TREE_THIS_VOLATILE (decl)
144 || (known_finite && function_always_visible_to_compiler_p (decl)))
148 warned_about = pointer_set_create ();
149 if (pointer_set_contains (warned_about, decl))
151 pointer_set_insert (warned_about, decl);
152 warning_at (DECL_SOURCE_LOCATION (decl),
155 ? _("function might be candidate for attribute %<%s%>")
156 : _("function might be candidate for attribute %<%s%>"
157 " if it is known to return normally"), attrib_name);
161 /* Emit suggestion about __attribute_((pure)) for DECL. KNOWN_FINITE
162 is true if the function is known to be finite. */
165 warn_function_pure (tree decl, bool known_finite)
167 static struct pointer_set_t *warned_about;
170 = suggest_attribute (OPT_Wsuggest_attribute_pure, decl,
171 known_finite, warned_about, "pure");
174 /* Emit suggestion about __attribute_((const)) for DECL. KNOWN_FINITE
175 is true if the function is known to be finite. */
178 warn_function_const (tree decl, bool known_finite)
180 static struct pointer_set_t *warned_about;
182 = suggest_attribute (OPT_Wsuggest_attribute_const, decl,
183 known_finite, warned_about, "const");
187 warn_function_noreturn (tree decl)
189 static struct pointer_set_t *warned_about;
190 if (!lang_hooks.missing_noreturn_ok_p (decl))
192 = suggest_attribute (OPT_Wsuggest_attribute_noreturn, decl,
193 true, warned_about, "noreturn");
195 /* Init the function state. */
200 free (funct_state_vec);
204 /* Return true if we have a function state for NODE. */
207 has_function_state (struct cgraph_node *node)
210 || VEC_length (funct_state, funct_state_vec) <= (unsigned int)node->uid)
212 return VEC_index (funct_state, funct_state_vec, node->uid) != NULL;
215 /* Return the function state from NODE. */
217 static inline funct_state
218 get_function_state (struct cgraph_node *node)
221 || VEC_length (funct_state, funct_state_vec) <= (unsigned int)node->uid
222 || !VEC_index (funct_state, funct_state_vec, node->uid))
223 /* We might want to put correct previously_known state into varying. */
224 return &varying_state;
225 return VEC_index (funct_state, funct_state_vec, node->uid);
228 /* Set the function state S for NODE. */
231 set_function_state (struct cgraph_node *node, funct_state s)
234 || VEC_length (funct_state, funct_state_vec) <= (unsigned int)node->uid)
235 VEC_safe_grow_cleared (funct_state, heap, funct_state_vec, node->uid + 1);
236 VEC_replace (funct_state, funct_state_vec, node->uid, s);
239 /* Check to see if the use (or definition when CHECKING_WRITE is true)
240 variable T is legal in a function that is either pure or const. */
243 check_decl (funct_state local,
244 tree t, bool checking_write, bool ipa)
246 /* Do not want to do anything with volatile except mark any
247 function that uses one to be not const or pure. */
248 if (TREE_THIS_VOLATILE (t))
250 local->pure_const_state = IPA_NEITHER;
252 fprintf (dump_file, " Volatile operand is not const/pure");
256 /* Do not care about a local automatic that is not static. */
257 if (!TREE_STATIC (t) && !DECL_EXTERNAL (t))
260 /* If the variable has the "used" attribute, treat it as if it had a
261 been touched by the devil. */
262 if (DECL_PRESERVE_P (t))
264 local->pure_const_state = IPA_NEITHER;
266 fprintf (dump_file, " Used static/global variable is not const/pure\n");
270 /* In IPA mode we are not interested in checking actual loads and stores;
271 they will be processed at propagation time using ipa_ref. */
275 /* Since we have dealt with the locals and params cases above, if we
276 are CHECKING_WRITE, this cannot be a pure or constant
280 local->pure_const_state = IPA_NEITHER;
282 fprintf (dump_file, " static/global memory write is not const/pure\n");
286 if (DECL_EXTERNAL (t) || TREE_PUBLIC (t))
288 /* Readonly reads are safe. */
289 if (TREE_READONLY (t) && !TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (t)))
290 return; /* Read of a constant, do not change the function state. */
294 fprintf (dump_file, " global memory read is not const\n");
295 /* Just a regular read. */
296 if (local->pure_const_state == IPA_CONST)
297 local->pure_const_state = IPA_PURE;
302 /* Compilation level statics can be read if they are readonly
304 if (TREE_READONLY (t))
308 fprintf (dump_file, " static memory read is not const\n");
309 /* Just a regular read. */
310 if (local->pure_const_state == IPA_CONST)
311 local->pure_const_state = IPA_PURE;
316 /* Check to see if the use (or definition when CHECKING_WRITE is true)
317 variable T is legal in a function that is either pure or const. */
320 check_op (funct_state local, tree t, bool checking_write)
322 t = get_base_address (t);
323 if (t && TREE_THIS_VOLATILE (t))
325 local->pure_const_state = IPA_NEITHER;
327 fprintf (dump_file, " Volatile indirect ref is not const/pure\n");
331 && (INDIRECT_REF_P (t) || TREE_CODE (t) == MEM_REF)
332 && TREE_CODE (TREE_OPERAND (t, 0)) == SSA_NAME
333 && !ptr_deref_may_alias_global_p (TREE_OPERAND (t, 0)))
336 fprintf (dump_file, " Indirect ref to local memory is OK\n");
339 else if (checking_write)
341 local->pure_const_state = IPA_NEITHER;
343 fprintf (dump_file, " Indirect ref write is not const/pure\n");
349 fprintf (dump_file, " Indirect ref read is not const\n");
350 if (local->pure_const_state == IPA_CONST)
351 local->pure_const_state = IPA_PURE;
355 /* compute state based on ECF FLAGS and store to STATE and LOOPING. */
358 state_from_flags (enum pure_const_state_e *state, bool *looping,
359 int flags, bool cannot_lead_to_return)
362 if (flags & ECF_LOOPING_CONST_OR_PURE)
365 if (dump_file && (dump_flags & TDF_DETAILS))
366 fprintf (dump_file, " looping");
368 if (flags & ECF_CONST)
371 if (dump_file && (dump_flags & TDF_DETAILS))
372 fprintf (dump_file, " const\n");
374 else if (flags & ECF_PURE)
377 if (dump_file && (dump_flags & TDF_DETAILS))
378 fprintf (dump_file, " pure\n");
380 else if (cannot_lead_to_return)
384 if (dump_file && (dump_flags & TDF_DETAILS))
385 fprintf (dump_file, " ignoring side effects->pure looping\n");
389 if (dump_file && (dump_flags & TDF_DETAILS))
390 fprintf (dump_file, " neihter\n");
391 *state = IPA_NEITHER;
396 /* Merge STATE and STATE2 and LOOPING and LOOPING2 and store
397 into STATE and LOOPING better of the two variants.
398 Be sure to merge looping correctly. IPA_NEITHER functions
399 have looping 0 even if they don't have to return. */
402 better_state (enum pure_const_state_e *state, bool *looping,
403 enum pure_const_state_e state2, bool looping2)
407 if (*state == IPA_NEITHER)
410 *looping = MIN (*looping, looping2);
412 else if (state2 != IPA_NEITHER)
413 *looping = MIN (*looping, looping2);
416 /* Merge STATE and STATE2 and LOOPING and LOOPING2 and store
417 into STATE and LOOPING worse of the two variants. */
420 worse_state (enum pure_const_state_e *state, bool *looping,
421 enum pure_const_state_e state2, bool looping2)
423 *state = MAX (*state, state2);
424 *looping = MAX (*looping, looping2);
427 /* Recognize special cases of builtins that are by themself not pure or const
428 but function using them is. */
430 special_builtlin_state (enum pure_const_state_e *state, bool *looping,
433 if (DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL)
434 switch (DECL_FUNCTION_CODE (callee))
436 case BUILT_IN_RETURN:
437 case BUILT_IN_UNREACHABLE:
438 case BUILT_IN_ALLOCA:
439 case BUILT_IN_STACK_SAVE:
440 case BUILT_IN_STACK_RESTORE:
441 case BUILT_IN_EH_POINTER:
442 case BUILT_IN_EH_FILTER:
443 case BUILT_IN_UNWIND_RESUME:
444 case BUILT_IN_CXA_END_CLEANUP:
445 case BUILT_IN_EH_COPY_VALUES:
446 case BUILT_IN_FRAME_ADDRESS:
448 case BUILT_IN_APPLY_ARGS:
452 case BUILT_IN_PREFETCH:
460 /* Check the parameters of a function call to CALL_EXPR to see if
461 there are any references in the parameters that are not allowed for
462 pure or const functions. Also check to see if this is either an
463 indirect call, a call outside the compilation unit, or has special
464 attributes that may also effect the purity. The CALL_EXPR node for
465 the entire call expression. */
468 check_call (funct_state local, gimple call, bool ipa)
470 int flags = gimple_call_flags (call);
471 tree callee_t = gimple_call_fndecl (call);
472 bool possibly_throws = stmt_could_throw_p (call);
473 bool possibly_throws_externally = (possibly_throws
474 && stmt_can_throw_external (call));
479 for (i = 0; i < gimple_num_ops (call); i++)
480 if (gimple_op (call, i)
481 && tree_could_throw_p (gimple_op (call, i)))
483 if (possibly_throws && cfun->can_throw_non_call_exceptions)
486 fprintf (dump_file, " operand can throw; looping\n");
487 local->looping = true;
489 if (possibly_throws_externally)
492 fprintf (dump_file, " operand can throw externally\n");
493 local->can_throw = true;
498 /* The const and pure flags are set by a variety of places in the
499 compiler (including here). If someone has already set the flags
500 for the callee, (such as for some of the builtins) we will use
501 them, otherwise we will compute our own information.
503 Const and pure functions have less clobber effects than other
504 functions so we process these first. Otherwise if it is a call
505 outside the compilation unit or an indirect call we punt. This
506 leaves local calls which will be processed by following the call
510 enum pure_const_state_e call_state;
513 if (special_builtlin_state (&call_state, &call_looping, callee_t))
515 worse_state (&local->pure_const_state, &local->looping,
516 call_state, call_looping);
519 /* When bad things happen to bad functions, they cannot be const
521 if (setjmp_call_p (callee_t))
524 fprintf (dump_file, " setjmp is not const/pure\n");
525 local->looping = true;
526 local->pure_const_state = IPA_NEITHER;
529 if (DECL_BUILT_IN_CLASS (callee_t) == BUILT_IN_NORMAL)
530 switch (DECL_FUNCTION_CODE (callee_t))
532 case BUILT_IN_LONGJMP:
533 case BUILT_IN_NONLOCAL_GOTO:
535 fprintf (dump_file, " longjmp and nonlocal goto is not const/pure\n");
536 local->pure_const_state = IPA_NEITHER;
537 local->looping = true;
544 /* When not in IPA mode, we can still handle self recursion. */
545 if (!ipa && callee_t == current_function_decl)
548 fprintf (dump_file, " Recursive call can loop.\n");
549 local->looping = true;
551 /* Either calle is unknown or we are doing local analysis.
552 Look to see if there are any bits available for the callee (such as by
553 declaration or because it is builtin) and process solely on the basis of
557 enum pure_const_state_e call_state;
559 if (possibly_throws && cfun->can_throw_non_call_exceptions)
562 fprintf (dump_file, " can throw; looping\n");
563 local->looping = true;
565 if (possibly_throws_externally)
569 fprintf (dump_file, " can throw externally to lp %i\n",
570 lookup_stmt_eh_lp (call));
572 fprintf (dump_file, " callee:%s\n",
573 IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (callee_t)));
575 local->can_throw = true;
577 if (dump_file && (dump_flags & TDF_DETAILS))
578 fprintf (dump_file, " checking flags for call:");
579 state_from_flags (&call_state, &call_looping, flags,
580 ((flags & (ECF_NORETURN | ECF_NOTHROW))
581 == (ECF_NORETURN | ECF_NOTHROW))
582 || (!flag_exceptions && (flags & ECF_NORETURN)));
583 worse_state (&local->pure_const_state, &local->looping,
584 call_state, call_looping);
586 /* Direct functions calls are handled by IPA propagation. */
589 /* Wrapper around check_decl for loads in local more. */
592 check_load (gimple stmt ATTRIBUTE_UNUSED, tree op, void *data)
595 check_decl ((funct_state)data, op, false, false);
597 check_op ((funct_state)data, op, false);
601 /* Wrapper around check_decl for stores in local more. */
604 check_store (gimple stmt ATTRIBUTE_UNUSED, tree op, void *data)
607 check_decl ((funct_state)data, op, true, false);
609 check_op ((funct_state)data, op, true);
613 /* Wrapper around check_decl for loads in ipa mode. */
616 check_ipa_load (gimple stmt ATTRIBUTE_UNUSED, tree op, void *data)
619 check_decl ((funct_state)data, op, false, true);
621 check_op ((funct_state)data, op, false);
625 /* Wrapper around check_decl for stores in ipa mode. */
628 check_ipa_store (gimple stmt ATTRIBUTE_UNUSED, tree op, void *data)
631 check_decl ((funct_state)data, op, true, true);
633 check_op ((funct_state)data, op, true);
637 /* Look into pointer pointed to by GSIP and figure out what interesting side
640 check_stmt (gimple_stmt_iterator *gsip, funct_state local, bool ipa)
642 gimple stmt = gsi_stmt (*gsip);
645 if (is_gimple_debug (stmt))
650 fprintf (dump_file, " scanning: ");
651 print_gimple_stmt (dump_file, stmt, 0, 0);
654 /* Look for loads and stores. */
655 walk_stmt_load_store_ops (stmt, local,
656 ipa ? check_ipa_load : check_load,
657 ipa ? check_ipa_store : check_store);
659 if (gimple_code (stmt) != GIMPLE_CALL
660 && stmt_could_throw_p (stmt))
662 if (cfun->can_throw_non_call_exceptions)
665 fprintf (dump_file, " can throw; looping");
666 local->looping = true;
668 if (stmt_can_throw_external (stmt))
671 fprintf (dump_file, " can throw externally");
672 local->can_throw = true;
675 switch (gimple_code (stmt))
678 check_call (local, stmt, ipa);
681 if (DECL_NONLOCAL (gimple_label_label (stmt)))
682 /* Target of long jump. */
685 fprintf (dump_file, " nonlocal label is not const/pure");
686 local->pure_const_state = IPA_NEITHER;
690 for (i = 0; i < gimple_asm_nclobbers (stmt); i++)
692 tree op = gimple_asm_clobber_op (stmt, i);
693 if (strcmp (TREE_STRING_POINTER (TREE_VALUE (op)), "memory") == 0)
696 fprintf (dump_file, " memory asm clobber is not const/pure");
697 /* Abandon all hope, ye who enter here. */
698 local->pure_const_state = IPA_NEITHER;
701 if (gimple_asm_volatile_p (stmt))
704 fprintf (dump_file, " volatile is not const/pure");
705 /* Abandon all hope, ye who enter here. */
706 local->pure_const_state = IPA_NEITHER;
707 local->looping = true;
716 /* This is the main routine for finding the reference patterns for
717 global variables within a function FN. */
720 analyze_function (struct cgraph_node *fn, bool ipa)
722 tree decl = fn->decl;
723 tree old_decl = current_function_decl;
725 basic_block this_block;
727 l = XCNEW (struct funct_state_d);
728 l->pure_const_state = IPA_CONST;
729 l->state_previously_known = IPA_NEITHER;
730 l->looping_previously_known = true;
732 l->can_throw = false;
736 fprintf (dump_file, "\n\n local analysis of %s\n ",
737 cgraph_node_name (fn));
740 push_cfun (DECL_STRUCT_FUNCTION (decl));
741 current_function_decl = decl;
743 FOR_EACH_BB (this_block)
745 gimple_stmt_iterator gsi;
746 struct walk_stmt_info wi;
748 memset (&wi, 0, sizeof(wi));
749 for (gsi = gsi_start_bb (this_block);
753 check_stmt (&gsi, l, ipa);
754 if (l->pure_const_state == IPA_NEITHER && l->looping && l->can_throw)
760 if (l->pure_const_state != IPA_NEITHER)
762 /* Const functions cannot have back edges (an
763 indication of possible infinite loop side
765 if (mark_dfs_back_edges ())
767 /* Preheaders are needed for SCEV to work.
768 Simple lateches and recorded exits improve chances that loop will
769 proved to be finite in testcases such as in loop-15.c and loop-24.c */
770 loop_optimizer_init (LOOPS_NORMAL
771 | LOOPS_HAVE_RECORDED_EXITS);
772 if (dump_file && (dump_flags & TDF_DETAILS))
773 flow_loops_dump (dump_file, NULL, 0);
774 if (mark_irreducible_loops ())
777 fprintf (dump_file, " has irreducible loops\n");
785 FOR_EACH_LOOP (li, loop, 0)
786 if (!finite_loop_p (loop))
789 fprintf (dump_file, " can not prove finiteness of loop %i\n", loop->num);
795 loop_optimizer_finalize ();
799 if (dump_file && (dump_flags & TDF_DETAILS))
800 fprintf (dump_file, " checking previously known:");
801 state_from_flags (&l->state_previously_known, &l->looping_previously_known,
802 flags_from_decl_or_type (fn->decl),
803 cgraph_node_cannot_return (fn));
805 better_state (&l->pure_const_state, &l->looping,
806 l->state_previously_known,
807 l->looping_previously_known);
808 if (TREE_NOTHROW (decl))
809 l->can_throw = false;
812 current_function_decl = old_decl;
816 fprintf (dump_file, "Function is locally looping.\n");
818 fprintf (dump_file, "Function is locally throwing.\n");
819 if (l->pure_const_state == IPA_CONST)
820 fprintf (dump_file, "Function is locally const.\n");
821 if (l->pure_const_state == IPA_PURE)
822 fprintf (dump_file, "Function is locally pure.\n");
827 /* Called when new function is inserted to callgraph late. */
829 add_new_function (struct cgraph_node *node, void *data ATTRIBUTE_UNUSED)
831 if (cgraph_function_body_availability (node) < AVAIL_OVERWRITABLE)
833 /* There are some shared nodes, in particular the initializers on
834 static declarations. We do not need to scan them more than once
835 since all we would be interested in are the addressof
837 visited_nodes = pointer_set_create ();
838 if (cgraph_function_body_availability (node) > AVAIL_OVERWRITABLE)
839 set_function_state (node, analyze_function (node, true));
840 pointer_set_destroy (visited_nodes);
841 visited_nodes = NULL;
844 /* Called when new clone is inserted to callgraph late. */
847 duplicate_node_data (struct cgraph_node *src, struct cgraph_node *dst,
848 void *data ATTRIBUTE_UNUSED)
850 if (has_function_state (src))
852 funct_state l = XNEW (struct funct_state_d);
853 gcc_assert (!has_function_state (dst));
854 memcpy (l, get_function_state (src), sizeof (*l));
855 set_function_state (dst, l);
859 /* Called when new clone is inserted to callgraph late. */
862 remove_node_data (struct cgraph_node *node, void *data ATTRIBUTE_UNUSED)
864 if (has_function_state (node))
866 funct_state l = get_function_state (node);
867 if (l != &varying_state)
869 set_function_state (node, NULL);
875 register_hooks (void)
877 static bool init_p = false;
884 node_removal_hook_holder =
885 cgraph_add_node_removal_hook (&remove_node_data, NULL);
886 node_duplication_hook_holder =
887 cgraph_add_node_duplication_hook (&duplicate_node_data, NULL);
888 function_insertion_hook_holder =
889 cgraph_add_function_insertion_hook (&add_new_function, NULL);
893 /* Analyze each function in the cgraph to see if it is locally PURE or
897 generate_summary (void)
899 struct cgraph_node *node;
903 /* There are some shared nodes, in particular the initializers on
904 static declarations. We do not need to scan them more than once
905 since all we would be interested in are the addressof
907 visited_nodes = pointer_set_create ();
909 /* Process all of the functions.
911 We process AVAIL_OVERWRITABLE functions. We can not use the results
912 by default, but the info can be used at LTO with -fwhole-program or
913 when function got clonned and the clone is AVAILABLE. */
915 for (node = cgraph_nodes; node; node = node->next)
916 if (cgraph_function_body_availability (node) >= AVAIL_OVERWRITABLE)
917 set_function_state (node, analyze_function (node, true));
919 pointer_set_destroy (visited_nodes);
920 visited_nodes = NULL;
924 /* Serialize the ipa info for lto. */
927 pure_const_write_summary (cgraph_node_set set,
928 varpool_node_set vset ATTRIBUTE_UNUSED)
930 struct cgraph_node *node;
931 struct lto_simple_output_block *ob
932 = lto_create_simple_output_block (LTO_section_ipa_pure_const);
933 unsigned int count = 0;
934 cgraph_node_set_iterator csi;
936 for (csi = csi_start (set); !csi_end_p (csi); csi_next (&csi))
938 node = csi_node (csi);
939 if (node->analyzed && has_function_state (node))
943 lto_output_uleb128_stream (ob->main_stream, count);
945 /* Process all of the functions. */
946 for (csi = csi_start (set); !csi_end_p (csi); csi_next (&csi))
948 node = csi_node (csi);
949 if (node->analyzed && has_function_state (node))
954 lto_cgraph_encoder_t encoder;
956 fs = get_function_state (node);
958 encoder = ob->decl_state->cgraph_node_encoder;
959 node_ref = lto_cgraph_encoder_encode (encoder, node);
960 lto_output_uleb128_stream (ob->main_stream, node_ref);
962 /* Note that flags will need to be read in the opposite
963 order as we are pushing the bitflags into FLAGS. */
964 bp = bitpack_create (ob->main_stream);
965 bp_pack_value (&bp, fs->pure_const_state, 2);
966 bp_pack_value (&bp, fs->state_previously_known, 2);
967 bp_pack_value (&bp, fs->looping_previously_known, 1);
968 bp_pack_value (&bp, fs->looping, 1);
969 bp_pack_value (&bp, fs->can_throw, 1);
970 lto_output_bitpack (&bp);
974 lto_destroy_simple_output_block (ob);
978 /* Deserialize the ipa info for lto. */
981 pure_const_read_summary (void)
983 struct lto_file_decl_data **file_data_vec = lto_get_file_decl_data ();
984 struct lto_file_decl_data *file_data;
988 while ((file_data = file_data_vec[j++]))
992 struct lto_input_block *ib
993 = lto_create_simple_input_block (file_data,
994 LTO_section_ipa_pure_const,
999 unsigned int count = lto_input_uleb128 (ib);
1001 for (i = 0; i < count; i++)
1004 struct cgraph_node *node;
1005 struct bitpack_d bp;
1007 lto_cgraph_encoder_t encoder;
1009 fs = XCNEW (struct funct_state_d);
1010 index = lto_input_uleb128 (ib);
1011 encoder = file_data->cgraph_node_encoder;
1012 node = lto_cgraph_encoder_deref (encoder, index);
1013 set_function_state (node, fs);
1015 /* Note that the flags must be read in the opposite
1016 order in which they were written (the bitflags were
1017 pushed into FLAGS). */
1018 bp = lto_input_bitpack (ib);
1019 fs->pure_const_state
1020 = (enum pure_const_state_e) bp_unpack_value (&bp, 2);
1021 fs->state_previously_known
1022 = (enum pure_const_state_e) bp_unpack_value (&bp, 2);
1023 fs->looping_previously_known = bp_unpack_value (&bp, 1);
1024 fs->looping = bp_unpack_value (&bp, 1);
1025 fs->can_throw = bp_unpack_value (&bp, 1);
1028 int flags = flags_from_decl_or_type (node->decl);
1029 fprintf (dump_file, "Read info for %s/%i ",
1030 cgraph_node_name (node),
1032 if (flags & ECF_CONST)
1033 fprintf (dump_file, " const");
1034 if (flags & ECF_PURE)
1035 fprintf (dump_file, " pure");
1036 if (flags & ECF_NOTHROW)
1037 fprintf (dump_file, " nothrow");
1038 fprintf (dump_file, "\n pure const state: %s\n",
1039 pure_const_names[fs->pure_const_state]);
1040 fprintf (dump_file, " previously known state: %s\n",
1041 pure_const_names[fs->looping_previously_known]);
1043 fprintf (dump_file," function is locally looping\n");
1044 if (fs->looping_previously_known)
1045 fprintf (dump_file," function is previously known looping\n");
1047 fprintf (dump_file," function is locally throwing\n");
1051 lto_destroy_simple_input_block (file_data,
1052 LTO_section_ipa_pure_const,
1060 ignore_edge (struct cgraph_edge *e)
1062 return (!e->can_throw_external);
1065 /* Return true if NODE is self recursive function. */
1068 self_recursive_p (struct cgraph_node *node)
1070 struct cgraph_edge *e;
1071 for (e = node->callees; e; e = e->next_callee)
1072 if (e->callee == node)
1077 /* Produce transitive closure over the callgraph and compute pure/const
1081 propagate_pure_const (void)
1083 struct cgraph_node *node;
1084 struct cgraph_node *w;
1085 struct cgraph_node **order =
1086 XCNEWVEC (struct cgraph_node *, cgraph_n_nodes);
1089 struct ipa_dfs_info * w_info;
1091 order_pos = ipa_utils_reduced_inorder (order, true, false, NULL);
1094 dump_cgraph (dump_file);
1095 ipa_utils_print_order(dump_file, "reduced", order, order_pos);
1098 /* Propagate the local information thru the call graph to produce
1099 the global information. All the nodes within a cycle will have
1100 the same info so we collapse cycles first. Then we can do the
1101 propagation in one pass from the leaves to the roots. */
1102 for (i = 0; i < order_pos; i++ )
1104 enum pure_const_state_e pure_const_state = IPA_CONST;
1105 bool looping = false;
1109 if (dump_file && (dump_flags & TDF_DETAILS))
1110 fprintf (dump_file, "Starting cycle\n");
1112 /* Find the worst state for any node in the cycle. */
1114 while (w && pure_const_state != IPA_NEITHER)
1116 struct cgraph_edge *e;
1117 struct cgraph_edge *ie;
1119 struct ipa_ref *ref;
1121 funct_state w_l = get_function_state (w);
1122 if (dump_file && (dump_flags & TDF_DETAILS))
1123 fprintf (dump_file, " Visiting %s/%i state:%s looping %i\n",
1124 cgraph_node_name (w),
1126 pure_const_names[w_l->pure_const_state],
1129 /* First merge in function body properties. */
1130 worse_state (&pure_const_state, &looping,
1131 w_l->pure_const_state, w_l->looping);
1132 if (pure_const_state == IPA_NEITHER)
1135 /* For overwritable nodes we can not assume anything. */
1136 if (cgraph_function_body_availability (w) == AVAIL_OVERWRITABLE)
1138 worse_state (&pure_const_state, &looping,
1139 w_l->state_previously_known,
1140 w_l->looping_previously_known);
1141 if (dump_file && (dump_flags & TDF_DETAILS))
1144 " Overwritable. state %s looping %i\n",
1145 pure_const_names[w_l->state_previously_known],
1146 w_l->looping_previously_known);
1153 /* We consider recursive cycles as possibly infinite.
1154 This might be relaxed since infinite recursion leads to stack
1159 /* Now walk the edges and merge in callee properties. */
1160 for (e = w->callees; e; e = e->next_callee)
1162 struct cgraph_node *y = e->callee;
1163 enum pure_const_state_e edge_state = IPA_CONST;
1164 bool edge_looping = false;
1166 if (dump_file && (dump_flags & TDF_DETAILS))
1170 cgraph_node_name (e->callee),
1173 if (cgraph_function_body_availability (y) > AVAIL_OVERWRITABLE)
1175 funct_state y_l = get_function_state (y);
1176 if (dump_file && (dump_flags & TDF_DETAILS))
1179 " state:%s looping:%i\n",
1180 pure_const_names[y_l->pure_const_state],
1183 if (y_l->pure_const_state > IPA_PURE
1184 && cgraph_edge_cannot_lead_to_return (e))
1186 if (dump_file && (dump_flags & TDF_DETAILS))
1188 " Ignoring side effects"
1189 " -> pure, looping\n");
1190 edge_state = IPA_PURE;
1191 edge_looping = true;
1195 edge_state = y_l->pure_const_state;
1196 edge_looping = y_l->looping;
1199 else if (special_builtlin_state (&edge_state, &edge_looping,
1203 state_from_flags (&edge_state, &edge_looping,
1204 flags_from_decl_or_type (y->decl),
1205 cgraph_edge_cannot_lead_to_return (e));
1207 /* Merge the results with what we already know. */
1208 better_state (&edge_state, &edge_looping,
1209 w_l->state_previously_known,
1210 w_l->looping_previously_known);
1211 worse_state (&pure_const_state, &looping,
1212 edge_state, edge_looping);
1213 if (pure_const_state == IPA_NEITHER)
1216 if (pure_const_state == IPA_NEITHER)
1219 /* Now process the indirect call. */
1220 for (ie = node->indirect_calls; ie; ie = ie->next_callee)
1222 enum pure_const_state_e edge_state = IPA_CONST;
1223 bool edge_looping = false;
1225 if (dump_file && (dump_flags & TDF_DETAILS))
1226 fprintf (dump_file, " Indirect call");
1227 state_from_flags (&edge_state, &edge_looping,
1228 ie->indirect_info->ecf_flags,
1229 cgraph_edge_cannot_lead_to_return (ie));
1230 /* Merge the results with what we already know. */
1231 better_state (&edge_state, &edge_looping,
1232 w_l->state_previously_known,
1233 w_l->looping_previously_known);
1234 worse_state (&pure_const_state, &looping,
1235 edge_state, edge_looping);
1236 if (pure_const_state == IPA_NEITHER)
1239 if (pure_const_state == IPA_NEITHER)
1242 /* And finally all loads and stores. */
1243 for (i = 0; ipa_ref_list_reference_iterate (&node->ref_list, i, ref); i++)
1245 enum pure_const_state_e ref_state = IPA_CONST;
1246 bool ref_looping = false;
1250 /* readonly reads are safe. */
1251 if (TREE_READONLY (ipa_ref_varpool_node (ref)->decl))
1253 if (dump_file && (dump_flags & TDF_DETAILS))
1254 fprintf (dump_file, " nonreadonly global var read\n");
1255 ref_state = IPA_PURE;
1258 if (ipa_ref_cannot_lead_to_return (ref))
1260 ref_state = IPA_NEITHER;
1261 if (dump_file && (dump_flags & TDF_DETAILS))
1262 fprintf (dump_file, " global var write\n");
1267 better_state (&ref_state, &ref_looping,
1268 w_l->state_previously_known,
1269 w_l->looping_previously_known);
1270 worse_state (&pure_const_state, &looping,
1271 ref_state, ref_looping);
1272 if (pure_const_state == IPA_NEITHER)
1275 w_info = (struct ipa_dfs_info *) w->aux;
1276 w = w_info->next_cycle;
1278 if (dump_file && (dump_flags & TDF_DETAILS))
1279 fprintf (dump_file, "Result %s looping %i\n",
1280 pure_const_names [pure_const_state],
1283 /* Copy back the region's pure_const_state which is shared by
1284 all nodes in the region. */
1288 funct_state w_l = get_function_state (w);
1289 enum pure_const_state_e this_state = pure_const_state;
1290 bool this_looping = looping;
1292 if (w_l->state_previously_known != IPA_NEITHER
1293 && this_state > w_l->state_previously_known)
1295 this_state = w_l->state_previously_known;
1296 this_looping |= w_l->looping_previously_known;
1298 if (!this_looping && self_recursive_p (w))
1299 this_looping = true;
1300 if (!w_l->looping_previously_known)
1301 this_looping = false;
1303 /* All nodes within a cycle share the same info. */
1304 w_l->pure_const_state = this_state;
1305 w_l->looping = this_looping;
1310 if (!TREE_READONLY (w->decl))
1312 warn_function_const (w->decl, !this_looping);
1314 fprintf (dump_file, "Function found to be %sconst: %s\n",
1315 this_looping ? "looping " : "",
1316 cgraph_node_name (w));
1318 cgraph_set_readonly_flag (w, true);
1319 cgraph_set_looping_const_or_pure_flag (w, this_looping);
1323 if (!DECL_PURE_P (w->decl))
1325 warn_function_pure (w->decl, !this_looping);
1327 fprintf (dump_file, "Function found to be %spure: %s\n",
1328 this_looping ? "looping " : "",
1329 cgraph_node_name (w));
1331 cgraph_set_pure_flag (w, true);
1332 cgraph_set_looping_const_or_pure_flag (w, this_looping);
1338 w_info = (struct ipa_dfs_info *) w->aux;
1339 w = w_info->next_cycle;
1344 for (node = cgraph_nodes; node; node = node->next)
1346 /* Get rid of the aux information. */
1349 w_info = (struct ipa_dfs_info *) node->aux;
1358 /* Produce transitive closure over the callgraph and compute nothrow
1362 propagate_nothrow (void)
1364 struct cgraph_node *node;
1365 struct cgraph_node *w;
1366 struct cgraph_node **order =
1367 XCNEWVEC (struct cgraph_node *, cgraph_n_nodes);
1370 struct ipa_dfs_info * w_info;
1372 order_pos = ipa_utils_reduced_inorder (order, true, false, ignore_edge);
1375 dump_cgraph (dump_file);
1376 ipa_utils_print_order(dump_file, "reduced for nothrow", order, order_pos);
1379 /* Propagate the local information thru the call graph to produce
1380 the global information. All the nodes within a cycle will have
1381 the same info so we collapse cycles first. Then we can do the
1382 propagation in one pass from the leaves to the roots. */
1383 for (i = 0; i < order_pos; i++ )
1385 bool can_throw = false;
1388 /* Find the worst state for any node in the cycle. */
1392 struct cgraph_edge *e, *ie;
1393 funct_state w_l = get_function_state (w);
1396 || cgraph_function_body_availability (w) == AVAIL_OVERWRITABLE)
1402 for (e = w->callees; e; e = e->next_callee)
1404 struct cgraph_node *y = e->callee;
1406 if (cgraph_function_body_availability (y) > AVAIL_OVERWRITABLE)
1408 funct_state y_l = get_function_state (y);
1412 if (y_l->can_throw && !TREE_NOTHROW (w->decl)
1413 && e->can_throw_external)
1416 else if (e->can_throw_external && !TREE_NOTHROW (y->decl))
1419 for (ie = node->indirect_calls; ie; ie = ie->next_callee)
1420 if (ie->can_throw_external)
1422 w_info = (struct ipa_dfs_info *) w->aux;
1423 w = w_info->next_cycle;
1426 /* Copy back the region's pure_const_state which is shared by
1427 all nodes in the region. */
1431 funct_state w_l = get_function_state (w);
1432 if (!can_throw && !TREE_NOTHROW (w->decl))
1434 struct cgraph_edge *e;
1435 cgraph_set_nothrow_flag (w, true);
1436 for (e = w->callers; e; e = e->next_caller)
1437 e->can_throw_external = false;
1439 fprintf (dump_file, "Function found to be nothrow: %s\n",
1440 cgraph_node_name (w));
1442 else if (can_throw && !TREE_NOTHROW (w->decl))
1443 w_l->can_throw = true;
1444 w_info = (struct ipa_dfs_info *) w->aux;
1445 w = w_info->next_cycle;
1450 for (node = cgraph_nodes; node; node = node->next)
1452 /* Get rid of the aux information. */
1455 w_info = (struct ipa_dfs_info *) node->aux;
1465 /* Produce the global information by preforming a transitive closure
1466 on the local information that was produced by generate_summary. */
1471 struct cgraph_node *node;
1473 cgraph_remove_function_insertion_hook (function_insertion_hook_holder);
1474 cgraph_remove_node_duplication_hook (node_duplication_hook_holder);
1475 cgraph_remove_node_removal_hook (node_removal_hook_holder);
1477 /* Nothrow makes more function to not lead to return and improve
1479 propagate_nothrow ();
1480 propagate_pure_const ();
1483 for (node = cgraph_nodes; node; node = node->next)
1484 if (has_function_state (node))
1485 free (get_function_state (node));
1486 VEC_free (funct_state, heap, funct_state_vec);
1492 gate_pure_const (void)
1494 return (flag_ipa_pure_const
1495 /* Don't bother doing anything if the program has errors. */
1499 struct ipa_opt_pass_d pass_ipa_pure_const =
1503 "pure-const", /* name */
1504 gate_pure_const, /* gate */
1505 propagate, /* execute */
1508 0, /* static_pass_number */
1509 TV_IPA_PURE_CONST, /* tv_id */
1510 0, /* properties_required */
1511 0, /* properties_provided */
1512 0, /* properties_destroyed */
1513 0, /* todo_flags_start */
1514 0 /* todo_flags_finish */
1516 generate_summary, /* generate_summary */
1517 pure_const_write_summary, /* write_summary */
1518 pure_const_read_summary, /* read_summary */
1519 NULL, /* write_optimization_summary */
1520 NULL, /* read_optimization_summary */
1521 NULL, /* stmt_fixup */
1523 NULL, /* function_transform */
1524 NULL /* variable_transform */
1527 /* Return true if function should be skipped for local pure const analysis. */
1530 skip_function_for_local_pure_const (struct cgraph_node *node)
1532 /* Because we do not schedule pass_fixup_cfg over whole program after early optimizations
1533 we must not promote functions that are called by already processed functions. */
1535 if (function_called_by_processed_nodes_p ())
1538 fprintf (dump_file, "Function called in recursive cycle; ignoring\n");
1541 if (cgraph_function_body_availability (node) <= AVAIL_OVERWRITABLE)
1544 fprintf (dump_file, "Function is not available or overwrittable; not analyzing.\n");
1550 /* Simple local pass for pure const discovery reusing the analysis from
1551 ipa_pure_const. This pass is effective when executed together with
1552 other optimization passes in early optimization pass queue. */
1555 local_pure_const (void)
1557 bool changed = false;
1560 struct cgraph_node *node;
1562 node = cgraph_node (current_function_decl);
1563 skip = skip_function_for_local_pure_const (node);
1564 if (!warn_suggest_attribute_const
1565 && !warn_suggest_attribute_pure
1569 /* First do NORETURN discovery. */
1570 if (!skip && !TREE_THIS_VOLATILE (current_function_decl)
1571 && EDGE_COUNT (EXIT_BLOCK_PTR->preds) == 0)
1573 warn_function_noreturn (cfun->decl);
1575 fprintf (dump_file, "Function found to be noreturn: %s\n",
1576 lang_hooks.decl_printable_name (current_function_decl, 2));
1578 /* Update declaration and reduce profile to executed once. */
1579 TREE_THIS_VOLATILE (current_function_decl) = 1;
1580 if (node->frequency > NODE_FREQUENCY_EXECUTED_ONCE)
1581 node->frequency = NODE_FREQUENCY_EXECUTED_ONCE;
1585 l = analyze_function (node, false);
1587 switch (l->pure_const_state)
1590 if (!TREE_READONLY (current_function_decl))
1592 warn_function_const (current_function_decl, !l->looping);
1595 cgraph_set_readonly_flag (node, true);
1596 cgraph_set_looping_const_or_pure_flag (node, l->looping);
1600 fprintf (dump_file, "Function found to be %sconst: %s\n",
1601 l->looping ? "looping " : "",
1602 lang_hooks.decl_printable_name (current_function_decl,
1605 else if (DECL_LOOPING_CONST_OR_PURE_P (current_function_decl)
1610 cgraph_set_looping_const_or_pure_flag (node, false);
1614 fprintf (dump_file, "Function found to be non-looping: %s\n",
1615 lang_hooks.decl_printable_name (current_function_decl,
1621 if (!DECL_PURE_P (current_function_decl))
1625 cgraph_set_pure_flag (node, true);
1626 cgraph_set_looping_const_or_pure_flag (node, l->looping);
1629 warn_function_pure (current_function_decl, !l->looping);
1631 fprintf (dump_file, "Function found to be %spure: %s\n",
1632 l->looping ? "looping " : "",
1633 lang_hooks.decl_printable_name (current_function_decl,
1636 else if (DECL_LOOPING_CONST_OR_PURE_P (current_function_decl)
1641 cgraph_set_looping_const_or_pure_flag (node, false);
1645 fprintf (dump_file, "Function found to be non-looping: %s\n",
1646 lang_hooks.decl_printable_name (current_function_decl,
1654 if (!l->can_throw && !TREE_NOTHROW (current_function_decl))
1656 struct cgraph_edge *e;
1658 cgraph_set_nothrow_flag (node, true);
1659 for (e = node->callers; e; e = e->next_caller)
1660 e->can_throw_external = false;
1663 fprintf (dump_file, "Function found to be nothrow: %s\n",
1664 lang_hooks.decl_printable_name (current_function_decl,
1670 return execute_fixup_cfg ();
1675 struct gimple_opt_pass pass_local_pure_const =
1679 "local-pure-const", /* name */
1680 gate_pure_const, /* gate */
1681 local_pure_const, /* execute */
1684 0, /* static_pass_number */
1685 TV_IPA_PURE_CONST, /* tv_id */
1686 0, /* properties_required */
1687 0, /* properties_provided */
1688 0, /* properties_destroyed */
1689 0, /* todo_flags_start */
1690 0 /* todo_flags_finish */