2 * Copyright (C) 1995-2007 University of Karlsruhe. All right reserved.
4 * This file is part of libFirm.
6 * This file may be distributed and/or modified under the terms of the
7 * GNU General Public License version 2 as published by the Free Software
8 * Foundation and appearing in the file LICENSE.GPL included in the
9 * packaging of this file.
11 * Licensees holding valid libFirm Professional Edition licenses may use
12 * this file in accordance with the libFirm Commercial License.
13 * Agreement provided with the Software.
15 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
16 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * @brief Compute the strongly connected regions and build
23 * backedge/loop datastructures.
24 * A variation on the Tarjan algorithm. See also [Trapp:99],
26 * @author Goetz Lindenmaier
44 #include "irgraph_t.h"
52 /* A variant of the loop tree that avoids loops without head.
53 This reduces the depth of the loop tree. */
54 #define NO_LOOPS_WITHOUT_HEAD 1
56 static ir_graph *outermost_ir_graph; /* The outermost graph the scc is computed
58 static ir_loop *current_loop; /* Current loop construction is working
60 static int loop_node_cnt = 0; /* Counts the number of allocated loop nodes.
61 Each loop node gets a unique number.
62 What for? ev. remove. @@@ */
63 static int current_dfn = 1; /* Counter to generate depth first numbering
66 static int max_loop_depth = 0;
68 void link_to_reg_end (ir_node *n, void *env);
69 void set_projx_link(ir_node *cb_projx, ir_node *end_projx);
70 ir_node *get_projx_link(ir_node *cb_projx);
72 /**********************************************************************/
73 /* Node attributes **/
74 /**********************************************************************/
76 /**********************************************************************/
77 /* Node attributes needed for the construction. **/
78 /**********************************************************************/
80 typedef struct scc_info {
81 int in_stack; /**< Marks whether node is on the stack. */
82 int dfn; /**< Depth first search number. */
83 int uplink; /**< dfn number of ancestor. */
84 /* ir_loop *loop; *//* Refers to the containing loop. */
86 struct section *section;
92 static INLINE scc_info* new_scc_info(void) {
93 scc_info *info = obstack_alloc (outermost_ir_graph->obst, sizeof (scc_info));
94 memset (info, 0, sizeof (scc_info));
99 mark_irn_in_stack (ir_node *n) {
100 scc_info *scc = get_irn_link(n);
106 mark_irn_not_in_stack (ir_node *n) {
107 scc_info *scc = get_irn_link(n);
113 irn_is_in_stack (ir_node *n) {
114 scc_info *scc = get_irn_link(n);
116 return scc->in_stack;
120 set_irn_uplink (ir_node *n, int uplink) {
121 scc_info *scc = get_irn_link(n);
123 scc->uplink = uplink;
127 get_irn_uplink (ir_node *n) {
128 scc_info *scc = get_irn_link(n);
134 set_irn_dfn (ir_node *n, int dfn) {
135 scc_info *scc = get_irn_link(n);
141 get_irn_dfn (ir_node *n) {
142 scc_info *scc = get_irn_link(n);
149 set_irn_loop (ir_node *n, ir_loop *loop) {
153 /* Uses temporary information to get the loop */
154 ir_loop *(get_irn_loop)(const ir_node *n) {
155 return _get_irn_loop(n);
160 static ir_loop *find_nodes_loop (ir_node *n, ir_loop *l) {
164 /* Test whether n is contained in this loop. */
165 for (i = 0; i < get_loop_n_nodes(l); i++)
166 if (n == get_loop_node(l, i)) return l;
168 /* Is this a leave in the loop tree? If so loop not found. */
169 if (get_loop_n_sons(l) == 0) return NULL;
171 /* Else descend in the loop tree. */
172 for (i = 0; i < get_loop_n_sons(l); i++) {
173 res = find_nodes_loop(n, get_loop_son(l, i));
179 /* @@@ temporary implementation, costly!!! */
180 ir_loop * get_irn_loop(ir_node *n) {
181 ir_loop *l = get_irg_loop(current_ir_graph);
182 l = find_nodes_loop(n, l);
187 /**********************************************************************/
189 /**********************************************************************/
191 static ir_node **stack = NULL;
192 static int tos = 0; /* top of stack */
195 * initializes the stack
197 static INLINE void init_stack(void) {
199 ARR_RESIZE (ir_node *, stack, 1000);
201 stack = NEW_ARR_F (ir_node *, 1000);
207 static INLINE void free_stack(void) {
215 * push a node onto the stack
217 * @param n The node to push
222 if (tos == ARR_LEN (stack)) {
223 int nlen = ARR_LEN (stack) * 2;
224 ARR_RESIZE (ir_node *, stack, nlen);
227 mark_irn_in_stack(n);
231 * pop a node from the stack
233 * @return The topmost node
235 static INLINE ir_node *
238 ir_node *n = stack[--tos];
239 mark_irn_not_in_stack(n);
244 * The nodes up to n belong to the current loop.
245 * Removes them from the stack and adds them to the current loop.
248 pop_scc_to_loop (ir_node *n)
257 set_irn_dfn(m, loop_node_cnt);
258 add_loop_node(current_loop, m);
259 set_irn_loop(m, current_loop);
262 /* if (m==n) break;*/
265 /* i might be bigger than 1 for dead (and that's why bad) loops */
267 printf("Mehr als eine Iteration!!!!!!!!!!!!!!!!!!!!!!!!!!!!11111\n");
271 /* GL ??? my last son is my grandson??? Removes loops with no
272 ir_nodes in them. Such loops have only another loop as son. (Why
273 can't they have two loops as sons? Does it never get that far? ) */
274 static void close_loop (ir_loop *l)
276 int last = get_loop_n_elements(l) - 1;
277 loop_element lelement = get_loop_element(l, last);
278 ir_loop *last_son = lelement.son;
280 if (get_kind(last_son) == k_ir_loop &&
281 get_loop_n_elements(last_son) == 1) {
284 lelement = get_loop_element(last_son, 0);
287 if (get_kind(gson) == k_ir_loop) {
288 loop_element new_last_son;
290 gson->outer_loop = l;
291 new_last_son.son = gson;
292 l->children[last] = new_last_son;
299 /* Removes and unmarks all nodes up to n from the stack.
300 The nodes must be visited once more to assign them to a scc. */
302 pop_scc_unmark_visit (ir_node *n)
308 set_irn_visited(m, 0);
312 /**********************************************************************/
313 /* The loop datastructure. **/
314 /**********************************************************************/
316 /* Allocates a new loop as son of current_loop. Sets current_loop
317 to the new loop and returns the father. */
318 ir_loop *new_loop (void) {
319 ir_loop *father, *son;
321 father = current_loop;
323 son = (ir_loop *) obstack_alloc (outermost_ir_graph->obst, sizeof (ir_loop));
324 memset (son, 0, sizeof (ir_loop));
325 son->kind = k_ir_loop;
326 son->children = NEW_ARR_F (loop_element, 0);
330 son->outer_loop = father;
331 add_loop_son(father, son);
332 son->depth = father->depth+1;
333 if (son->depth > max_loop_depth) max_loop_depth = son->depth;
334 } else { /* The root loop */
335 son->outer_loop = son;
340 son->loop_nr = get_irp_new_node_nr();
349 /* Finishes the datastructures, copies the arrays to the obstack
351 A. Schoesser: Caution: loop -> sons is gone. */
352 static void mature_loop (ir_loop *loop) {
355 new_sons = NEW_ARR_D (ir_loop *, current_ir_graph->obst, ARR_LEN(loop->sons));
356 memcpy (new_sons, loop->sons, sizeof (ir_loop *) * ARR_LEN(loop->sons));
357 DEL_ARR_F(loop->sons);
358 loop->sons = new_sons;
362 /* Returns outer loop, itself if outermost. */
363 ir_loop *(get_loop_outer_loop)(const ir_loop *loop) {
364 return _get_loop_outer_loop(loop);
367 /* Returns nesting depth of this loop */
368 int (get_loop_depth)(const ir_loop *loop) {
369 return _get_loop_depth(loop);
372 /* Returns the number of inner loops */
373 int (get_loop_n_sons)(const ir_loop *loop) {
374 return _get_loop_n_sons(loop);
377 /* Returns the pos`th loop_node-child *
378 * TODO: This method isn`t very efficient ! *
379 * Returns NULL if there isn`t a pos`th loop_node */
380 ir_loop *get_loop_son (ir_loop *loop, int pos) {
381 int child_nr = 0, loop_nr = -1;
383 assert(loop && loop->kind == k_ir_loop);
384 while(child_nr < ARR_LEN(loop->children))
386 if(*(loop -> children[child_nr].kind) == k_ir_loop)
389 return(loop -> children[child_nr].son);
395 /* Use EXCLUSIVELY this function to add sons, otherwise the loop->n_sons
399 add_loop_son(ir_loop *loop, ir_loop *son) {
402 assert(loop && loop->kind == k_ir_loop);
403 assert(get_kind(son) == k_ir_loop);
404 ARR_APP1 (loop_element, loop->children, lson);
408 /* Returns the number of nodes in the loop */
409 int get_loop_n_nodes (ir_loop *loop) {
410 assert(loop); assert(loop->kind == k_ir_loop);
411 return loop -> n_nodes;
412 /* return ARR_LEN(loop->nodes); */
415 /* Returns the pos`th ir_node-child *
416 * TODO: This method isn`t very efficient ! *
417 * Returns NULL if there isn`t a pos`th ir_node */
418 ir_node *get_loop_node (ir_loop *loop, int pos) {
419 int child_nr, node_nr = -1;
421 assert(loop && loop->kind == k_ir_loop);
422 assert(pos < get_loop_n_nodes(loop));
424 for (child_nr = 0; child_nr < ARR_LEN(loop->children); child_nr++) {
425 if(*(loop -> children[child_nr].kind) == k_ir_node)
428 return(loop -> children[child_nr].node);
431 assert(0 && "no child at pos found");
435 /* Use EXCLUSIVELY this function to add nodes, otherwise the loop->n_nodes
439 add_loop_node(ir_loop *loop, ir_node *n) {
442 assert(loop && loop->kind == k_ir_loop);
443 assert(get_kind(n) == k_ir_node || get_kind(n) == k_ir_graph); /* used in callgraph.c */
444 ARR_APP1 (loop_element, loop->children, ln);
448 /* Returns the number of elements contained in loop. */
449 int get_loop_n_elements (const ir_loop *loop) {
450 assert(loop && loop->kind == k_ir_loop);
451 return(ARR_LEN(loop->children));
455 Returns the pos`th loop element.
456 This may be a loop_node or a ir_node. The caller of this function has
457 to check the *(loop_element.kind) field for "k_ir_node" or "k_ir_loop"
458 and then select the appropriate "loop_element.node" or "loop_element.son".
461 loop_element get_loop_element(const ir_loop *loop, int pos) {
462 assert(loop && loop->kind == k_ir_loop && pos < ARR_LEN(loop->children));
463 return(loop -> children[pos]);
466 int get_loop_element_pos(const ir_loop *loop, void *le) {
468 assert(loop && loop->kind == k_ir_loop);
470 n = get_loop_n_elements(loop);
471 for (i = 0; i < n; i++)
472 if (get_loop_element(loop, i).node == le) return i;
476 int get_loop_loop_nr(const ir_loop *loop) {
477 assert(loop && loop->kind == k_ir_loop);
479 return loop->loop_nr;
486 /** A field to connect additional information to a loop. Only valid
487 if libfirm_debug is set. */
488 void set_loop_link (ir_loop *loop, void *link) {
489 assert(loop && loop->kind == k_ir_loop);
494 void *get_loop_link (const ir_loop *loop) {
495 assert(loop && loop->kind == k_ir_loop);
503 int (is_ir_loop)(const void *thing) {
504 return _is_ir_loop(thing);
507 /* The outermost loop is remarked in the surrounding graph. */
508 void (set_irg_loop)(ir_graph *irg, ir_loop *loop) {
509 _set_irg_loop(irg, loop);
512 /* Returns the root loop info (if exists) for an irg. */
513 ir_loop *(get_irg_loop)(ir_graph *irg) {
514 return _get_irg_loop(irg);
518 /**********************************************************************/
519 /* Constructing and destructing the loop/backedge information. **/
520 /**********************************************************************/
522 /* Initialization steps. **********************************************/
525 init_node (ir_node *n, void *env) {
527 set_irn_link (n, new_scc_info());
532 init_scc_common (void) {
539 init_scc (ir_graph *irg) {
541 irg_walk_graph (irg, init_node, NULL, NULL);
543 irg_walk (irg, link_to_reg_end, NULL, NULL);
550 cg_walk (init_node, NULL, NULL);
552 #if EXPERIMENTAL_LOOP_TREE
553 cg_walk (link_to_reg_end, NULL, NULL);
557 /* Condition for breaking the recursion. */
558 static int is_outermost_Start(ir_node *n) {
559 /* Test whether this is the outermost Start node. If so
560 recursion must end. */
561 if ((get_irn_op(n) == op_Block) &&
562 (get_Block_n_cfgpreds(n) == 1) &&
563 (get_irn_op(skip_Proj(get_Block_cfgpred(n, 0))) == op_Start) &&
564 (get_nodes_block(skip_Proj(get_Block_cfgpred(n, 0))) == n)) {
568 /* @@@ Bad condition:
569 not possible in interprocedural view as outermost_graph is
570 not necessarily the only with a dead-end start block.
571 Besides current_ir_graph is not set properly. */
572 if ((get_irn_op(n) == op_Block) &&
573 (n == get_irg_start_block(current_ir_graph))) {
574 if ((!get_interprocedural_view()) ||
575 (current_ir_graph == outermost_ir_graph))
582 /* When to walk from nodes to blocks. Only for Control flow operations? */
584 get_start_index(ir_node *n) {
585 #undef BLOCK_BEFORE_NODE
586 #define BLOCK_BEFORE_NODE 1
588 #if BLOCK_BEFORE_NODE
590 /* This version assures, that all nodes are ordered absolutely. This allows
591 to undef all nodes in the heap analysis if the block is false, which means
593 I.e., with this code, the order on the loop tree is correct. But a (single)
594 test showed the loop tree is deeper. */
595 if (get_irn_op(n) == op_Phi ||
596 get_irn_op(n) == op_Block ||
597 (get_irn_op(n) == op_Filter && get_interprocedural_view()) ||
598 (get_irg_pinned(get_irn_irg(n)) == op_pin_state_floats &&
599 get_irn_pinned(n) == op_pin_state_floats))
600 // Here we could test for backedge at -1 which is illegal
607 /* This version causes deeper loop trees (at least we verified this
609 But it guarantees that Blocks are analysed before nodes contained in the
610 block. If so, we can set the value to undef if the block is not \
612 if (is_cfop(n) || is_fragile_op(n) || get_irn_op(n) == op_Start)
620 /* Test for legal loop header: Block, Phi, ... */
621 static INLINE int is_possible_loop_head(ir_node *n) {
622 ir_op *op = get_irn_op(n);
623 return ((op == op_Block) ||
625 ((op == op_Filter) && get_interprocedural_view()));
628 /* Returns non-zero if n is a loop header, i.e., it is a Block, Phi
629 or Filter node and has predecessors within the loop and out
631 @arg root: only needed for assertion. */
633 is_head (ir_node *n, ir_node *root)
636 int some_outof_loop = 0, some_in_loop = 0;
638 /* Test for legal loop header: Block, Phi, ... */
639 if (!is_possible_loop_head(n))
642 if (!is_outermost_Start(n)) {
643 arity = get_irn_arity(n);
644 for (i = get_start_index(n); i < arity; i++) {
645 ir_node *pred = get_irn_n(n, i);
647 if (is_backedge(n, i)) continue;
648 if (!irn_is_in_stack(pred)) {
651 if(get_irn_uplink(pred) < get_irn_uplink(root)) {
652 assert(get_irn_uplink(pred) >= get_irn_uplink(root));
658 return some_outof_loop && some_in_loop;
662 * Returns non-zero if n is possible loop head of an endless loop.
663 * I.e., it is a Block, Phi or Filter node and has only predecessors
665 * @param root: only needed for assertion.
668 is_endless_head (ir_node *n, ir_node *root)
671 int some_outof_loop = 0, some_in_loop = 0;
673 /* Test for legal loop header: Block, Phi, ... */
674 if (!is_possible_loop_head(n))
677 if (!is_outermost_Start(n)) {
678 arity = get_irn_arity(n);
679 for (i = get_start_index(n); i < arity; i++) {
680 ir_node *pred = get_irn_n(n, i);
682 if (is_backedge(n, i)) { continue; }
683 if (!irn_is_in_stack(pred)) {
684 some_outof_loop = 1; //printf(" some out of loop ");
686 if(get_irn_uplink(pred) < get_irn_uplink(root)) {
687 assert(get_irn_uplink(pred) >= get_irn_uplink(root));
693 return !some_outof_loop && some_in_loop;
696 /* Returns index of the predecessor with the smallest dfn number
697 greater-equal than limit. */
699 smallest_dfn_pred (ir_node *n, int limit)
701 int i, index = -2, min = -1;
703 if (!is_outermost_Start(n)) {
704 int arity = get_irn_arity(n);
705 for (i = get_start_index(n); i < arity; i++) {
706 ir_node *pred = get_irn_n(n, i);
708 if (is_backedge(n, i) || !irn_is_in_stack(pred)) continue;
709 if (get_irn_dfn(pred) >= limit && (min == -1 || get_irn_dfn(pred) < min)) {
711 min = get_irn_dfn(pred);
718 /* Returns index of the predecessor with the largest dfn number. */
720 largest_dfn_pred (ir_node *n)
722 int i, index = -2, max = -1;
724 if (!is_outermost_Start(n)) {
725 int arity = get_irn_arity(n);
726 for (i = get_start_index(n); i < arity; i++) {
727 ir_node *pred = get_irn_n(n, i);
728 if (is_backedge (n, i) || !irn_is_in_stack(pred)) continue;
729 if (get_irn_dfn(pred) > max) {
731 max = get_irn_dfn(pred);
738 /** Searches the stack for possible loop heads. Tests these for backedges.
739 If it finds a head with an unmarked backedge it marks this edge and
740 returns the tail of the loop.
741 If it finds no backedge returns NULL.
742 ("disable_backedge" in fiasco)
744 * @param n A node where uplink == dfn.
748 find_tail (ir_node *n) {
750 int i, res_index = -2;
753 if (!icfg && rm_cyclic_phis && remove_cyclic_phis (n)) return NULL;
755 m = stack[tos-1]; /* tos = top of stack */
756 if (is_head (m, n)) {
757 res_index = smallest_dfn_pred(m, 0);
758 if ((res_index == -2) && /* no smallest dfn pred found. */
762 if (m == n) return NULL; // Is this to catch Phi - self loops?
763 for (i = tos-2; i >= 0; --i) {
766 if (is_head (m, n)) {
767 res_index = smallest_dfn_pred (m, get_irn_dfn(m) + 1);
768 if (res_index == -2) /* no smallest dfn pred found. */
769 res_index = largest_dfn_pred (m);
771 if ((m == n) && (res_index == -2)) { /* dont walk past loop head. */
777 /* We should not walk past our selves on the stack: The upcoming nodes
778 are not in this loop. We assume a loop not reachable from Start. */
787 /* A dead loop not reachable from Start. */
788 for (i = tos-2; i >= 0; --i) {
790 if (is_endless_head (m, n)) {
791 res_index = smallest_dfn_pred (m, get_irn_dfn(m) + 1);
792 if (res_index == -2) /* no smallest dfn pred found. */
793 res_index = largest_dfn_pred (m);
796 if (m == n) { break; } /* It's not an unreachable loop, either. */
798 //assert(0 && "no head found on stack");
802 if (res_index <= -2) {
803 /* It's a completely bad loop: without Phi/Block nodes that can
804 be a head. I.e., the code is "dying". We break the loop by
805 setting Bad nodes. */
806 int arity = get_irn_arity(n);
807 for (i = -1; i < arity; ++i) {
808 set_irn_n(n, i, get_irg_bad(get_irn_irg(n)));
812 assert (res_index > -2);
814 set_backedge (m, res_index);
815 return is_outermost_Start(n) ? NULL : get_irn_n(m, res_index);
819 #if EXPERIMENTAL_LOOP_TREE
821 /* ----------------------------------------------------------------
822 AS: This is experimental code to build loop trees suitable for
823 the heap analysis. Does not work correctly right now... :-(
826 Search in stack for the corresponding first Call-End-ProjX that
827 corresponds to one of the control flow predecessors of the given
828 block, that is the possible callers.
829 returns: the control predecessor to chose\
830 or -1 if no corresponding Call-End-Node could be found
832 - -------------------------------------------------------------- */
834 int search_endproj_in_stack(ir_node *start_block)
837 assert(is_Block(start_block));
838 for(i = tos - 1; i >= 0; --i)
840 if(get_irn_op(stack[i]) == op_Proj && get_irn_mode(stack[i]) == mode_X &&
841 get_irn_op(get_irn_n(stack[i], 0)) == op_EndReg)
843 printf("FOUND PROJ!!!!!!!!!!!!!!!!!!!!!!!!!!\n");
844 ir_node *end_projx = stack[i];
846 int arity = get_irn_arity(start_block);
847 for(j = 0; j < arity; j++)
849 ir_node *begin_projx = get_Block_cfgpred(get_irg_start_block(get_irn_irg(end_projx)),
850 get_Proj_proj(end_projx));
851 if(get_irn_n(start_block, j) == begin_projx)
853 printf("FOUND IT!!!!!!!!!!!!!!!!!!\n");
863 static pmap *projx_link = NULL;
865 void link_to_reg_end (ir_node *n, void *env) {
866 if(get_irn_op(n) == op_Proj &&
867 get_irn_mode(n) == mode_X &&
868 get_irn_op(get_irn_n(n, 0)) == op_EndReg) {
869 /* Reg End Projx -> Find the CallBegin Projx and hash it */
870 ir_node *end_projx = n;
871 ir_node *begin_projx = get_Block_cfgpred(get_irg_start_block(get_irn_irg(end_projx)),
872 get_Proj_proj(end_projx));
873 set_projx_link(begin_projx, end_projx);
877 void set_projx_link(ir_node *cb_projx, ir_node *end_projx)
879 if(projx_link == NULL)
880 projx_link = pmap_create();
881 pmap_insert(projx_link, (void *)cb_projx, (void *)end_projx);
884 ir_node *get_projx_link(ir_node *cb_projx)
886 return((ir_node *) pmap_get(projx_link, (void *)cb_projx));
892 is_outermost_loop(ir_loop *l) {
893 return l == get_loop_outer_loop(l);
897 /*-----------------------------------------------------------*
898 * The core algorithm. *
899 *-----------------------------------------------------------*/
901 static void scc (ir_node *n) {
903 if (irn_visited(n)) return;
906 /* Initialize the node */
907 set_irn_dfn(n, current_dfn); /* Depth first number for this node */
908 set_irn_uplink(n, current_dfn); /* ... is default uplink. */
909 set_irn_loop(n, NULL);
913 /* AS: get_start_index might return -1 for Control Flow Nodes, and thus a negative
914 array index would be passed to is_backedge(). But CFG Nodes dont't have a backedge array,
915 so is_backedge does not access array[-1] but correctly returns false! */
917 if (!is_outermost_Start(n)) {
918 int arity = get_irn_arity(n);
920 for (i = get_start_index(n); i < arity; i++) {
922 if (is_backedge(n, i)) continue;
923 m = get_irn_n(n, i); /* get_irn_ip_pred(n, i); */
924 /* if ((!m) || (get_irn_op(m) == op_Unknown)) continue; */
926 if (irn_is_in_stack(m)) {
927 /* Uplink of m is smaller if n->m is a backedge.
928 Propagate the uplink to mark the loop. */
929 if (get_irn_uplink(m) < get_irn_uplink(n))
930 set_irn_uplink(n, get_irn_uplink(m));
935 if (get_irn_dfn(n) == get_irn_uplink(n)) {
936 /* This condition holds for
937 1) the node with the incoming backedge.
938 That is: We found a loop!
939 2) Straight line code, because no uplink has been propagated, so the
940 uplink still is the same as the dfn.
942 But n might not be a proper loop head for the analysis. Proper loop
943 heads are Block and Phi nodes. find_tail searches the stack for
944 Block's and Phi's and takes those nodes as loop heads for the current
945 loop instead and marks the incoming edge as backedge. */
947 ir_node *tail = find_tail(n);
949 /* We have a loop, that is no straight line code,
950 because we found a loop head!
951 Next actions: Open a new loop on the loop tree and
952 try to find inner loops */
954 #if NO_LOOPS_WITHOUT_HEAD
955 /* This is an adaption of the algorithm from fiasco / optscc to
956 * avoid loops without Block or Phi as first node. This should
957 * severely reduce the number of evaluations of nodes to detect
958 * a fixpoint in the heap analysis.
959 * Further it avoids loops without firm nodes that cause errors
960 * in the heap analyses.
961 * But attention: don't do it for the outermost loop: This loop
962 * is not iterated. A first block can be a loop head in case of
963 * an endless recursion. */
967 if ((get_loop_n_elements(current_loop) > 0) || (is_outermost_loop(current_loop))) {
975 ir_loop *l = new_loop();
978 /* Remove the loop from the stack ... */
979 pop_scc_unmark_visit (n);
981 /* The current backedge has been marked, that is temporarily eliminated,
982 by find tail. Start the scc algorithm
983 anew on the subgraph that is left (the current loop without the backedge)
984 in order to find more inner loops. */
987 assert (irn_visited(n));
988 #if NO_LOOPS_WITHOUT_HEAD
995 /* No loop head was found, that is we have straightline code.
996 Pop all nodes from the stack to the current loop. */
1002 static void my_scc (ir_node *n) {
1004 if (irn_visited(n)) return;
1005 mark_irn_visited(n);
1007 /* Initialize the node */
1008 set_irn_dfn(n, current_dfn); /* Depth first number for this node */
1009 set_irn_uplink(n, current_dfn); /* ... is default uplink. */
1010 set_irn_loop(n, NULL);
1014 /* AS: get_start_index might return -1 for Control Flow Nodes, and thus a negative
1015 array index would be passed to is_backedge(). But CFG Nodes dont't have a backedge array,
1016 so is_backedge does not access array[-1] but correctly returns false! */
1018 if (!is_outermost_Start(n)) {
1019 int arity = get_irn_arity(n);
1021 for (i = get_start_index(n); i < arity; i++) {
1023 if (is_backedge(n, i)) continue;
1024 m = get_irn_n(n, i); /* get_irn_ip_pred(n, i); */
1025 /* if ((!m) || (get_irn_op(m) == op_Unknown)) continue; */
1027 if (irn_is_in_stack(m)) {
1028 /* Uplink of m is smaller if n->m is a backedge.
1029 Propagate the uplink to mark the loop. */
1030 if (get_irn_uplink(m) < get_irn_uplink(n))
1031 set_irn_uplink(n, get_irn_uplink(m));
1036 if (get_irn_dfn(n) == get_irn_uplink(n)) {
1037 /* This condition holds for
1038 1) the node with the incoming backedge.
1039 That is: We found a loop!
1040 2) Straight line code, because no uplink has been propagated, so the
1041 uplink still is the same as the dfn.
1043 But n might not be a proper loop head for the analysis. Proper loop
1044 heads are Block and Phi nodes. find_tail searches the stack for
1045 Block's and Phi's and takes those nodes as loop heads for the current
1046 loop instead and marks the incoming edge as backedge. */
1048 ir_node *tail = find_tail(n);
1050 /* We have a loop, that is no straight line code,
1051 because we found a loop head!
1052 Next actions: Open a new loop on the loop tree and
1053 try to find inner loops */
1055 #if NO_LOOPS_WITHOUT_HEAD
1056 /* This is an adaption of the algorithm from fiasco / optscc to
1057 * avoid loops without Block or Phi as first node. This should
1058 * severely reduce the number of evaluations of nodes to detect
1059 * a fixpoint in the heap analysis.
1060 * Further it avoids loops without firm nodes that cause errors
1061 * in the heap analyses. */
1065 if ((get_loop_n_elements(current_loop) > 0) || (is_outermost_loop(current_loop))) {
1073 ir_loop *l = new_loop();
1076 /* Remove the loop from the stack ... */
1077 pop_scc_unmark_visit (n);
1079 /* The current backedge has been marked, that is temporarily eliminated,
1080 by find tail. Start the scc algorithm
1081 anew on the subgraph that is left (the current loop without the backedge)
1082 in order to find more inner loops. */
1085 assert (irn_visited(n));
1086 #if NO_LOOPS_WITHOUT_HEAD
1093 /* No loop head was found, that is we have straightline code.
1094 Pop all nodes from the stack to the current loop. */
1100 /* Constructs backedge information for irg. In interprocedural view constructs
1101 backedges for all methods called by irg, too. */
1102 int construct_backedges(ir_graph *irg) {
1103 ir_graph *rem = current_ir_graph;
1106 assert(!get_interprocedural_view() &&
1107 "not implemented, use construct_ip_backedges");
1110 current_ir_graph = irg;
1111 outermost_ir_graph = irg;
1113 init_scc(current_ir_graph);
1115 current_loop = NULL;
1116 new_loop(); /* sets current_loop */
1117 head_rem = current_loop; /* Just for assertion */
1119 inc_irg_visited(current_ir_graph);
1121 scc(get_irg_end(current_ir_graph));
1123 assert(head_rem == current_loop);
1124 set_irg_loop(current_ir_graph, current_loop);
1125 set_irg_loopinfo_state(current_ir_graph, loopinfo_consistent);
1126 assert(get_irg_loop(current_ir_graph)->kind == k_ir_loop);
1128 irg->loops = current_loop;
1132 count_loop (the_loop, &count, &depth);
1136 current_ir_graph = rem;
1138 return max_loop_depth;
1142 int construct_ip_backedges (void) {
1143 ir_graph *rem = current_ir_graph;
1144 int rem_ipv = get_interprocedural_view();
1148 assert(get_irp_ip_view_state() == ip_view_valid);
1150 outermost_ir_graph = get_irp_main_irg();
1154 current_loop = NULL;
1155 new_loop(); /* sets current_loop */
1156 set_interprocedural_view(1);
1158 inc_max_irg_visited();
1159 for (i = 0; i < get_irp_n_irgs(); i++)
1160 set_irg_visited(get_irp_irg(i), get_max_irg_visited());
1162 /** We have to start the walk at the same nodes as cg_walk. **/
1163 /* Walk starting at unreachable procedures. Only these
1164 * have End blocks visible in interprocedural view. */
1165 for (i = 0; i < get_irp_n_irgs(); i++) {
1167 current_ir_graph = get_irp_irg(i);
1169 sb = get_irg_start_block(current_ir_graph);
1171 if ((get_Block_n_cfgpreds(sb) > 1) ||
1172 (get_nodes_block(get_Block_cfgpred(sb, 0)) != sb)) continue;
1174 scc(get_irg_end(current_ir_graph));
1177 /* Check whether we walked all procedures: there could be procedures
1178 with cyclic calls but no call from the outside. */
1179 for (i = 0; i < get_irp_n_irgs(); i++) {
1181 current_ir_graph = get_irp_irg(i);
1183 /* Test start block: if inner procedure end and end block are not
1184 * visible and therefore not marked. */
1185 sb = get_irg_start_block(current_ir_graph);
1186 if (get_irn_visited(sb) < get_irg_visited(current_ir_graph)) scc(sb);
1189 /* Walk all endless loops in inner procedures.
1190 * We recognize an inner procedure if the End node is not visited. */
1191 for (i = 0; i < get_irp_n_irgs(); i++) {
1193 current_ir_graph = get_irp_irg(i);
1195 e = get_irg_end(current_ir_graph);
1196 if (get_irn_visited(e) < get_irg_visited(current_ir_graph)) {
1198 /* Don't visit the End node. */
1199 for (j = 0; j < get_End_n_keepalives(e); j++) scc(get_End_keepalive(e, j));
1203 set_irg_loop(outermost_ir_graph, current_loop);
1204 set_irg_loopinfo_state(current_ir_graph, loopinfo_ip_consistent);
1205 assert(get_irg_loop(outermost_ir_graph)->kind == k_ir_loop);
1207 current_ir_graph = rem;
1208 set_interprocedural_view(rem_ipv);
1209 return max_loop_depth;
1212 void my_construct_ip_backedges (void) {
1213 ir_graph *rem = current_ir_graph;
1214 int rem_ipv = get_interprocedural_view();
1217 assert(get_irp_ip_view_state() == ip_view_valid);
1219 outermost_ir_graph = get_irp_main_irg();
1223 current_loop = NULL;
1224 new_loop(); /* sets current_loop */
1225 set_interprocedural_view(1);
1227 inc_max_irg_visited();
1228 for (i = 0; i < get_irp_n_irgs(); i++)
1229 set_irg_visited(get_irp_irg(i), get_max_irg_visited());
1231 /** We have to start the walk at the same nodes as cg_walk. **/
1232 /* Walk starting at unreachable procedures. Only these
1233 * have End blocks visible in interprocedural view. */
1234 for (i = 0; i < get_irp_n_irgs(); i++) {
1236 current_ir_graph = get_irp_irg(i);
1238 sb = get_irg_start_block(current_ir_graph);
1240 if ((get_Block_n_cfgpreds(sb) > 1) ||
1241 (get_nodes_block(get_Block_cfgpred(sb, 0)) != sb)) continue;
1243 my_scc(get_irg_end(current_ir_graph));
1246 /* Check whether we walked all procedures: there could be procedures
1247 with cyclic calls but no call from the outside. */
1248 for (i = 0; i < get_irp_n_irgs(); i++) {
1250 current_ir_graph = get_irp_irg(i);
1252 /* Test start block: if inner procedure end and end block are not
1253 * visible and therefore not marked. */
1254 sb = get_irg_start_block(current_ir_graph);
1255 if (get_irn_visited(sb) < get_irg_visited(current_ir_graph)) scc(sb);
1258 /* Walk all endless loops in inner procedures.
1259 * We recognize an inner procedure if the End node is not visited. */
1260 for (i = 0; i < get_irp_n_irgs(); i++) {
1262 current_ir_graph = get_irp_irg(i);
1264 e = get_irg_end(current_ir_graph);
1265 if (get_irn_visited(e) < get_irg_visited(current_ir_graph)) {
1267 /* Don't visit the End node. */
1268 for (j = 0; j < get_End_n_keepalives(e); j++) scc(get_End_keepalive(e, j));
1272 set_irg_loop(outermost_ir_graph, current_loop);
1273 set_irg_loopinfo_state(current_ir_graph, loopinfo_ip_consistent);
1274 assert(get_irg_loop(outermost_ir_graph)->kind == k_ir_loop);
1276 current_ir_graph = rem;
1277 set_interprocedural_view(rem_ipv);
1280 static void reset_backedges(ir_node *n) {
1281 if (is_possible_loop_head(n)) {
1282 int rem = get_interprocedural_view();
1284 set_interprocedural_view(1);
1286 set_interprocedural_view(1);
1288 set_interprocedural_view(rem);
1294 static void loop_reset_backedges(ir_loop *l) {
1296 reset_backedges(get_loop_node(l, 0));
1297 for (i = 0; i < get_loop_n_nodes(l); ++i)
1298 set_irn_loop(get_loop_node(l, i), NULL);
1299 for (i = 0; i < get_loop_n_sons(l); ++i) {
1300 loop_reset_backedges(get_loop_son(l, i));
1305 static void loop_reset_node(ir_node *n, void *env) {
1307 set_irn_loop(n, NULL);
1312 /** Removes all loop information.
1313 Resets all backedges */
1314 void free_loop_information(ir_graph *irg) {
1315 /* We can not use this recursion, as the loop might contain
1316 illegal nodes by now. Why else would we throw away the
1318 if (get_irg_loop(irg)) loop_reset_backedges(get_irg_loop(irg));
1320 irg_walk_graph(irg, loop_reset_node, NULL, NULL);
1321 set_irg_loop(irg, NULL);
1322 set_irg_loopinfo_state(current_ir_graph, loopinfo_none);
1323 /* We cannot free the loop nodes, they are on the obstack. */
1327 void free_all_loop_information (void) {
1329 int rem = get_interprocedural_view();
1330 set_interprocedural_view(1); /* To visit all filter nodes */
1331 for (i = 0; i < get_irp_n_irgs(); i++) {
1332 free_loop_information(get_irp_irg(i));
1334 set_interprocedural_view(rem);
1341 /* Debug stuff *************************************************/
1343 static int test_loop_node(ir_loop *l) {
1344 int i, has_node = 0, found_problem = 0;
1347 assert(l && l->kind == k_ir_loop);
1349 if (get_loop_n_elements(l) == 0) {
1351 dump_loop(l, "-ha");
1354 le = get_loop_element(l, 0);
1355 if (*(le.kind) != k_ir_node) {
1356 assert(le.kind && *(le.kind) == k_ir_loop);
1359 dump_loop(l, "-ha");
1362 if ((*(le.kind) == k_ir_node) && !is_possible_loop_head(le.node)) {
1364 dump_loop(l, "-ha");
1367 if ((get_loop_depth(l) != 0) &&
1368 (*(le.kind) == k_ir_node) && !has_backedges(le.node)) {
1370 dump_loop(l, "-ha");
1375 for (i = 0; i < get_loop_n_elements(l); ++i) {
1376 le = get_loop_element(l, i);
1377 if (*(le.kind) == k_ir_node)
1380 if (test_loop_node(le.son)) found_problem = 1;
1383 if (has_node == 0) {
1385 dump_loop(l, "-ha");
1388 return found_problem;
1391 /** Prints all loop nodes that
1392 * - do not have any firm nodes, only loop sons
1393 * - the header is not a Phi, Block or Filter.
1395 void find_strange_loop_nodes(ir_loop *l) {
1396 int found_problem = 0;
1397 found_problem = test_loop_node(l);
1398 printf("Finished Test\n\n");
1399 if (found_problem) exit(0);
1403 /* ------------------------------------------------------------------- */
1404 /* Simple analyses based on the loop information */
1405 /* ------------------------------------------------------------------- */
1407 int is_loop_variant(ir_loop *l, ir_loop *b) {
1410 if (l == b) return 1;
1412 n_elems = get_loop_n_elements(l);
1413 for (i = 0; i < n_elems; ++i) {
1414 loop_element e = get_loop_element(l, i);
1415 if (is_ir_loop(e.kind))
1416 if (is_loop_variant(e.son, b))
1423 /* Test whether a value is loop invariant.
1425 * @param n The node to be tested.
1426 * @param block A block node. We pass the block, not the loop as we must
1427 * start off with a block loop to find all proper uses.
1429 * Returns non-zero, if the node n is not changed in the loop block
1430 * belongs to or in inner loops of this blocks loop. */
1431 int is_loop_invariant(ir_node *n, ir_node *block) {
1432 ir_loop *l = get_irn_loop(block);
1433 ir_node *b = (is_Block(n)) ? n : get_nodes_block(n);
1434 return !is_loop_variant(l, get_irn_loop(b));