3 * File name: ir/opt/opt_osr.c
4 * Purpose: Operator Strength Reduction, based on
5 * Keith D. Cooper, L. Taylor Simpson, Christopher A. Vick
10 * Copyright: (c) 2006 Universität Karlsruhe
11 * Licence: This file protected by GPL - GNU GENERAL PUBLIC LICENSE.
44 /** The debug handle. */
45 DEBUG_ONLY(static firm_dbg_module_t *dbg;)
49 ir_node *head; /**< the head of the list */
53 typedef struct node_entry {
54 unsigned DFSnum; /**< the DFS number of this node */
55 unsigned low; /**< the low number of this node */
56 ir_node *header; /**< the header of this node */
57 int in_stack; /**< flag, set if the node is on the stack */
58 ir_node *next; /**< link to the next node the the same scc */
59 scc *pscc; /**< the scc of this node */
60 unsigned POnum; /**< the post order number for blocks */
63 /** The environment. */
64 typedef struct iv_env {
65 struct obstack obst; /**< an obstack for allocations */
66 ir_node **stack; /**< the node stack */
67 int tos; /**< tos index */
68 unsigned nextDFSnum; /**< the current DFS number */
69 unsigned POnum; /**< current post order number */
70 set *quad_map; /**< a map from (op, iv, rc) to node */
71 set *lftr_edges; /**< the set of lftr edges */
72 unsigned replaced; /**< number of replaced ops */
73 unsigned lftr_replaced; /**< number of applied linear function test replacements */
74 unsigned flags; /**< additional flags */
75 /** Function called to process a SCC. */
76 void (*process_scc)(scc *pscc, struct iv_env *env);
80 * An entry in the (op, node, node) -> node map.
82 typedef struct quad_t {
83 opcode code; /**< the opcode of the reduced operation */
84 ir_node *op1; /**< the first operand the reduced operation */
85 ir_node *op2; /**< the second operand of the reduced operation */
87 ir_node *res; /**< the reduced operation */
93 typedef struct LFTR_edge {
94 ir_node *src; /**< the source node */
95 ir_node *dst; /**< the destination node */
96 opcode code; /**< the opcode that must be applied */
97 ir_node *rc; /**< the region const that must be applied */
101 static ir_node *reduce(ir_node *orig, ir_node *iv, ir_node *rc, iv_env *env);
104 * Compare two LFTR edges.
106 static int LFTR_cmp(const void *e1, const void *e2, size_t size) {
107 const LFTR_edge *l1 = e1;
108 const LFTR_edge *l2 = e2;
110 return l1->src != l2->src;
116 static LFTR_edge *LFTR_find(ir_node *src, iv_env *env) {
121 return set_find(env->lftr_edges, &key, sizeof(key), HASH_PTR(src));
127 static void LFTR_add(ir_node *src, ir_node *dst, opcode code, ir_node *rc, iv_env *env) {
136 * There might be more than one edge here. This is rather bad
137 * because we currently store only one.
139 // assert(LFTR_find(src, env) == NULL);
140 set_insert(env->lftr_edges, &key, sizeof(key), HASH_PTR(src));
144 * Gets the node_entry of a node
146 static node_entry *get_irn_ne(ir_node *irn, iv_env *env) {
147 node_entry *e = get_irn_link(irn);
150 e = obstack_alloc(&env->obst, sizeof(*e));
151 memset(e, 0, sizeof(*e));
152 set_irn_link(irn, e);
158 * Check if irn is an IV.
160 * @param irn the node to check
161 * @param env the environment
163 * @returns the header if it is one, NULL else
165 static ir_node *is_iv(ir_node *irn, iv_env *env) {
166 return get_irn_ne(irn, env)->header;
170 * Check if irn is a region constant.
171 * The block or irn must strictly dominate the header block.
173 * @param irn the node to check
174 * @param header_block the header block of the induction variable
176 static int is_rc(ir_node *irn, ir_node *header_block) {
177 ir_node *block = get_nodes_block(irn);
179 return (block != header_block) && block_dominates(block, header_block);
183 * Set compare function for the quad set.
185 static int quad_cmp(const void *e1, const void *e2, size_t size) {
186 const quad_t *c1 = e1;
187 const quad_t *c2 = e2;
189 return c1->code != c2->code || c1->op1 != c2->op1 || c1->op2 != c2->op2;
193 * Check if an reduced operation was already calculated.
195 * @param code the opcode of the operation
196 * @param op1 the first operand of the operation
197 * @param op2 the second operand of the operation
198 * @param env the environment
200 * @return the already reduced node or NULL if this operation is not yet reduced
202 static ir_node *search(opcode code, ir_node *op1, ir_node *op2, iv_env *env) {
209 entry = set_find(env->quad_map, &key, sizeof(key),
210 (code * 9) ^ HASH_PTR(op1) ^HASH_PTR(op2));
217 * Add an reduced operation.
219 * @param code the opcode of the operation
220 * @param op1 the first operand of the operation
221 * @param op2 the second operand of the operation
222 * @param result the result of the reduced operation
223 * @param env the environment
225 static void add(opcode code, ir_node *op1, ir_node *op2, ir_node *result, iv_env *env) {
233 set_insert(env->quad_map, &key, sizeof(key),
234 (code * 9) ^ HASH_PTR(op1) ^HASH_PTR(op2));
238 * Find a location where to place a bin-op whose operands are in
241 * @param block1 the block of the first operand
242 * @param block2 the block of the second operand
244 * Note that we know here that such a place must exists. Moreover, this means
245 * that either block1 dominates block2 or vice versa. So, just return
248 static ir_node *find_location(ir_node *block1, ir_node *block2) {
249 if (block_dominates(block1, block2))
251 assert(block_dominates(block2, block1));
256 * Create a node that executes an op1 code op1 operation.
258 * @param code the opcode to execute
259 * @param db debug info to add to the new node
260 * @param op1 the first operand
261 * @param op2 the second operand
262 * @param mode the mode of the new operation
264 * @return the newly created node
266 static ir_node *do_apply(opcode code, dbg_info *db, ir_node *op1, ir_node *op2, ir_mode *mode) {
267 ir_graph *irg = current_ir_graph;
269 ir_node *block = find_location(get_nodes_block(op1), get_nodes_block(op2));
273 result = new_rd_Mul(db, irg, block, op1, op2, mode);
276 result = new_rd_Add(db, irg, block, op1, op2, mode);
279 result = new_rd_Sub(db, irg, block, op1, op2, mode);
289 * The Apply operation.
291 * @param orig the node that represent the original operation and determines
292 * the opcode, debug-info and mode of a newly created one
293 * @param op1 the first operand
294 * @param op2 the second operand
295 * @param env the environment
297 * @return the newly created node
299 static ir_node *apply(ir_node *orig, ir_node *op1, ir_node *op2, iv_env *env) {
300 opcode code = get_irn_opcode(orig);
301 ir_node *result = search(code, op1, op2, env);
304 dbg_info *db = get_irn_dbg_info(orig);
305 ir_node *op1_header = get_irn_ne(op1, env)->header;
306 ir_node *op2_header = get_irn_ne(op2, env)->header;
308 if (op1_header != NULL && is_rc(op2, op1_header)) {
309 result = reduce(orig, op1, op2, env);
311 else if (op2_header != NULL && is_rc(op1, op2_header)) {
312 result = reduce(orig, op2, op1, env);
315 result = do_apply(code, db, op1, op2, get_irn_mode(orig));
316 get_irn_ne(result, env)->header = NULL; }
322 * The Reduce operation.
324 * @param orig the node that represent the original operation and determines
325 * the opcode, debug-info and mode of a newly created one
326 * @param iv the induction variable
327 * @param rc the region constant
328 * @param env the environment
330 * @return the reduced node
332 static ir_node *reduce(ir_node *orig, ir_node *iv, ir_node *rc, iv_env *env) {
333 opcode code = get_irn_opcode(orig);
334 ir_node *result = search(code, iv, rc, env);
337 node_entry *e, *iv_e;
339 ir_mode *mode = get_irn_mode(orig);
341 result = exact_copy(iv);
343 /* Beware: we must always create a new nduction variable with the same mode
344 as the node we are replacing. Espicially this means the mode might be changed
345 from P to I and back. This is always possible, because we have only Phi, Add
347 set_irn_mode(result, mode);
348 add(code, iv, rc, result, env);
349 DB((dbg, LEVEL_3, " Created new %+F for %+F (%s %+F)\n", result, iv,
350 get_irn_opname(orig), rc));
352 iv_e = get_irn_ne(iv, env);
353 e = get_irn_ne(result, env);
354 e->header = iv_e->header;
356 /* create the LFTR edge */
357 LFTR_add(iv, result, code, rc, env);
359 n = get_irn_arity(result);
360 for (i = 0; i < n; ++i) {
361 ir_node *o = get_irn_n(result, i);
363 e = get_irn_ne(o, env);
364 if (e->header == iv_e->header)
365 o = reduce(orig, o, rc, env);
366 else if (is_Phi(result))
367 o = apply(orig, o, rc, env);
370 o = apply(orig, o, rc, env);
372 set_irn_n(result, i, o);
376 DB((dbg, LEVEL_3, " Already Created %+F for %+F (%s %+F)\n", result, iv,
377 get_irn_opname(orig), rc));
383 * The Replace operation.
385 * @param irn the node that will be replaced
386 * @param iv the induction variable
387 * @param rc the region constant
388 * @param env the environment
390 static int replace(ir_node *irn, ir_node *iv, ir_node *rc, iv_env *env) {
392 ir_loop *iv_loop = get_irn_loop(get_nodes_block(iv));
393 ir_loop *irn_loop = get_irn_loop(get_nodes_block(irn));
395 /* only replace nodes that are in the same (or deeper loops) */
396 if (get_loop_depth(irn_loop) >= get_loop_depth(iv_loop)) {
397 DB((dbg, LEVEL_2, " Replacing %+F\n", irn));
399 result = reduce(irn, iv, rc, env);
401 node_entry *e, *iv_e;
403 hook_strength_red(current_ir_graph, irn);
404 exchange(irn, result);
405 e = get_irn_ne(result, env);
406 iv_e = get_irn_ne(iv, env);
407 e->header = iv_e->header;
415 * Check if a node can be replaced (+, -, *).
417 * @param irn the node to check
418 * @param env the environment
420 * @return non-zero if irn should be Replace'd
422 static int check_replace(ir_node *irn, iv_env *env) {
423 ir_node *left, *right, *iv, *rc;
424 ir_op *op = get_irn_op(irn);
425 opcode code = get_op_code(op);
434 left = get_binop_left(irn);
435 right = get_binop_right(irn);
437 liv = is_iv(left, env);
438 riv = is_iv(right, env);
439 if (liv && is_rc(right, liv)) {
440 iv = left; rc = right;
442 else if (riv && is_op_commutative(op) &&
444 iv = right; rc = left;
448 if (code == iro_Mul && env->flags & osr_flag_ignore_x86_shift) {
450 tarval *tv = get_Const_tarval(rc);
452 if (tarval_is_long(tv)) {
453 long value = get_tarval_long(tv);
455 if (value == 2 || value == 4 || value == 8) {
456 /* do not reduce multiplications by 2, 4, 8 */
463 return replace(irn, iv, rc, env);
473 * Check which SCC's are induction variables.
476 * @param env the environment
478 static void classify_iv(scc *pscc, iv_env *env) {
479 ir_node *irn, *next, *header = NULL;
480 node_entry *b, *h = NULL;
481 int j, only_phi, num_outside;
484 /* find the header block for this scc */
485 for (irn = pscc->head; irn; irn = next) {
486 node_entry *e = get_irn_link(irn);
487 ir_node *block = get_nodes_block(irn);
490 b = get_irn_ne(block, env);
493 if (h->POnum < b->POnum) {
504 /* check if this scc contains only Phi, Add or Sub nodes */
508 for (irn = pscc->head; irn; irn = next) {
509 node_entry *e = get_irn_ne(irn, env);
512 switch (get_irn_opcode(irn)) {
518 for (j = get_irn_arity(irn) - 1; j >= 0; --j) {
519 ir_node *pred = get_irn_n(irn, j);
520 node_entry *pe = get_irn_ne(pred, env);
522 if (pe->pscc != e->pscc) {
523 /* not in the same SCC, must be a region const */
524 if (! is_rc(pred, header)) {
525 /* not an induction variable */
531 } else if (out_rc != pred) {
538 /* not an induction variable */
542 /* found an induction variable */
543 DB((dbg, LEVEL_2, " Found an induction variable:\n "));
544 if (only_phi && num_outside == 1) {
545 /* a phi cycle with only one real predecessor can be collapsed */
546 DB((dbg, LEVEL_2, " Found an USELESS Phi cycle:\n "));
548 for (irn = pscc->head; irn; irn = next) {
549 node_entry *e = get_irn_ne(irn, env);
552 exchange(irn, out_rc);
558 /* set the header for every node in this scc */
559 for (irn = pscc->head; irn; irn = next) {
560 node_entry *e = get_irn_ne(irn, env);
563 DB((dbg, LEVEL_2, " %+F,", irn));
565 DB((dbg, LEVEL_2, "\n"));
569 for (irn = pscc->head; irn; irn = next) {
570 node_entry *e = get_irn_ne(irn, env);
573 if (! check_replace(irn, env))
579 * Process a SCC for the operator strength reduction.
581 * @param pscc the SCC
582 * @param env the environment
584 static void process_scc(scc *pscc, iv_env *env) {
585 ir_node *head = pscc->head;
586 node_entry *e = get_irn_link(head);
592 DB((dbg, LEVEL_4, " SCC at %p:\n ", pscc));
593 for (irn = pscc->head; irn; irn = next) {
594 node_entry *e = get_irn_link(irn);
598 DB((dbg, LEVEL_4, " %+F,", irn));
600 DB((dbg, LEVEL_4, "\n"));
604 if (e->next == NULL) {
605 /* this SCC has only a single member */
606 check_replace(head, env);
608 classify_iv(pscc, env);
613 * If an SCC is a Phi only cycle, remove it.
615 static void remove_phi_cycle(scc *pscc, iv_env *env) {
620 /* check if this scc contains only Phi, Add or Sub nodes */
622 for (irn = pscc->head; irn; irn = next) {
623 node_entry *e = get_irn_ne(irn, env);
629 for (j = get_irn_arity(irn) - 1; j >= 0; --j) {
630 ir_node *pred = get_irn_n(irn, j);
631 node_entry *pe = get_irn_ne(pred, env);
633 if (pe->pscc != e->pscc) {
634 /* not in the same SCC, must be the only input */
637 } else if (out_rc != pred) {
643 /* found a Phi cycle */
644 DB((dbg, LEVEL_2, " Found an USELESS Phi cycle:\n "));
646 for (irn = pscc->head; irn; irn = next) {
647 node_entry *e = get_irn_ne(irn, env);
650 exchange(irn, out_rc);
656 * Process a SCC for the Phi cycle removement.
658 * @param pscc the SCC
659 * @param env the environment
661 static void process_phi_only_scc(scc *pscc, iv_env *env) {
662 ir_node *head = pscc->head;
663 node_entry *e = get_irn_link(head);
669 DB((dbg, LEVEL_4, " SCC at %p:\n ", pscc));
670 for (irn = pscc->head; irn; irn = next) {
671 node_entry *e = get_irn_link(irn);
675 DB((dbg, LEVEL_4, " %+F,", irn));
677 DB((dbg, LEVEL_4, "\n"));
682 remove_phi_cycle(pscc, env);
687 * Push a node onto the stack.
689 * @param env the environment
690 * @param n the node to push
692 static void push(iv_env *env, ir_node *n) {
695 if (env->tos == ARR_LEN(env->stack)) {
696 int nlen = ARR_LEN(env->stack) * 2;
697 ARR_RESIZE(ir_node *, env->stack, nlen);
699 env->stack[env->tos++] = n;
700 e = get_irn_ne(n, env);
705 * pop a node from the stack
707 * @param env the environment
709 * @return The topmost node
711 static ir_node *pop(iv_env *env)
713 ir_node *n = env->stack[--env->tos];
714 node_entry *e = get_irn_ne(n, env);
721 * Do Tarjan's SCC algorithm and drive OSR.
723 * @param irn start at this node
724 * @param env the environment
726 static void dfs(ir_node *irn, iv_env *env)
729 node_entry *node = get_irn_ne(irn, env);
731 mark_irn_visited(irn);
733 /* do not put blocks into the scc */
735 n = get_irn_arity(irn);
736 for (i = 0; i < n; ++i) {
737 ir_node *pred = get_irn_n(irn, i);
739 if (irn_not_visited(pred))
744 ir_node *block = get_nodes_block(irn);
746 node->DFSnum = env->nextDFSnum++;
747 node->low = node->DFSnum;
750 /* handle the block */
751 if (irn_not_visited(block))
754 n = get_irn_arity(irn);
755 for (i = 0; i < n; ++i) {
756 ir_node *pred = get_irn_n(irn, i);
757 node_entry *o = get_irn_ne(pred, env);
759 if (irn_not_visited(pred)) {
761 node->low = MIN(node->low, o->low);
763 if (o->DFSnum < node->DFSnum && o->in_stack)
764 node->low = MIN(o->DFSnum, node->low);
766 if (node->low == node->DFSnum) {
767 scc *pscc = obstack_alloc(&env->obst, sizeof(*pscc));
775 e = get_irn_ne(x, env);
777 e->next = pscc->head;
781 env->process_scc(pscc, env);
787 * Do the DFS by starting at the End node of a graph.
789 * @param irg the graph to process
790 * @param env the environment
792 static void do_dfs(ir_graph *irg, iv_env *env) {
793 ir_graph *rem = current_ir_graph;
794 ir_node *end = get_irg_end(irg);
797 current_ir_graph = irg;
798 inc_irg_visited(irg);
800 /* visit all visible nodes */
803 /* visit the keep-alives */
804 n = get_End_n_keepalives(end);
805 for (i = 0; i < n; ++i) {
806 ir_node *ka = get_End_keepalive(end, i);
808 if (irn_not_visited(ka))
812 current_ir_graph = rem;
816 * Post-block-walker: assign the post-order number.
818 static void assign_po(ir_node *block, void *ctx) {
820 node_entry *e = get_irn_ne(block, env);
822 e->POnum = env->POnum++;
826 * Follows the LFTR edges and return the last node in the chain.
828 * @param irn the node that should be followed
829 * @param env the IV environment
832 * In the current implementation only the last edge is stored, so
833 * only one chain exists. That's why we might miss some opportunities.
835 static ir_node *followEdges(ir_node *irn, iv_env *env) {
837 LFTR_edge *e = LFTR_find(irn, env);
846 * Apply one LFTR edge operation.
847 * Return NULL if the transformation cannot be done safely without
850 * @param rc the IV node that should be translated
851 * @param e the LFTR edge
852 * @param env the IV environment
854 * @return the translated region constant or NULL
855 * if the translation was not possible
858 * In the current implementation only the last edge is stored, so
859 * only one chain exists. That's why we might miss some opportunities.
861 static ir_node *applyOneEdge(ir_node *rc, LFTR_edge *e, iv_env *env) {
862 if (env->flags & osr_flag_lftr_with_ov_check) {
863 tarval *tv_l, *tv_r, *tv;
864 tarval_int_overflow_mode_t ovmode;
866 /* overflow can only be decided for Consts */
867 if (! is_Const(e->rc)) {
868 DB((dbg, LEVEL_4, " = UNKNOWN (%+F)", e->rc));
872 tv_l = get_Const_tarval(rc);
873 tv_r = get_Const_tarval(e->rc);
875 ovmode = tarval_get_integer_overflow_mode();
876 tarval_set_integer_overflow_mode(TV_OVERFLOW_BAD);
880 tv = tarval_mul(tv_l, tv_r);
881 DB((dbg, LEVEL_4, " * %+F", tv_r));
884 tv = tarval_add(tv_l, tv_r);
885 DB((dbg, LEVEL_4, " + %+F", tv_r));
888 tv = tarval_sub(tv_l, tv_r);
889 DB((dbg, LEVEL_4, " - %+F", tv_r));
895 tarval_set_integer_overflow_mode(ovmode);
897 if (tv == tarval_bad) {
898 DB((dbg, LEVEL_4, " = OVERFLOW"));
901 return new_r_Const(current_ir_graph, get_irn_n(rc, -1), get_tarval_mode(tv), tv);
903 return do_apply(e->code, NULL, rc, e->rc, get_irn_mode(rc));
907 * Applies the operations represented by the LFTR edges to a
908 * region constant and returns the value.
909 * Return NULL if the transformation cannot be done safely without
912 * @param iv the IV node that starts the LFTR edge chain
913 * @param rc the region constant that should be translated
914 * @param env the IV environment
916 * @return the translated region constant or NULL
917 * if the translation was not possible
919 static ir_node *applyEdges(ir_node *iv, ir_node *rc, iv_env *env) {
922 if (env->flags & osr_flag_lftr_with_ov_check) {
923 /* overflow can only be decided for Consts */
924 if (! is_Const(rc)) {
925 DB((dbg, LEVEL_4, " = UNKNOWN (%+F)\n", rc));
928 DB((dbg, LEVEL_4, "%+F", get_Const_tarval(rc)));
931 for (irn = iv; rc;) {
932 LFTR_edge *e = LFTR_find(irn, env);
934 rc = applyOneEdge(rc, e, env);
940 DB((dbg, LEVEL_3, "\n"));
945 * Walker, finds Cmp(iv, rc) or Cmp(rc, iv)
946 * and tries to optimize them.
948 static void do_lftr(ir_node *cmp, void *ctx) {
950 ir_node *left, *right, *liv, *riv;
952 ir_node *nleft = NULL, *nright = NULL;
954 if (get_irn_op(cmp) != op_Cmp)
957 left = get_Cmp_left(cmp);
958 right = get_Cmp_right(cmp);
960 liv = is_iv(left, env);
961 riv = is_iv(right, env);
962 if (liv && is_rc(right, liv)) {
963 iv = left; rc = right;
965 nright = applyEdges(iv, rc, env);
966 if (nright && nright != rc) {
967 nleft = followEdges(iv, env);
970 else if (riv && is_rc(left, riv)) {
971 iv = right; rc = left;
973 nleft = applyEdges(iv, rc, env);
974 if (nleft && nleft != rc) {
975 nright = followEdges(iv, env);
979 if (nleft && nright) {
980 DB((dbg, LEVEL_2, " LFTR for %+F\n", cmp));
981 set_Cmp_left(cmp, nleft);
982 set_Cmp_right(cmp, nright);
983 ++env->lftr_replaced;
988 * do linear function test replacement.
990 * @param irg the graph that should be optimized
991 * @param env the IV environment
993 static void lftr(ir_graph *irg, iv_env *env) {
994 irg_walk_graph(irg, NULL, do_lftr, env);
998 * Pre-walker: set all node links to NULL and fix the
999 * block of Proj nodes.
1001 static void clear_and_fix(ir_node *irn, void *env)
1003 set_irn_link(irn, NULL);
1006 ir_node *pred = get_Proj_pred(irn);
1007 set_irn_n(irn, -1, get_irn_n(pred, -1));
1011 /* Performs Operator Strength Reduction for the passed graph. */
1012 void opt_osr(ir_graph *irg, unsigned flags) {
1016 if (! get_opt_strength_red()) {
1017 /* only kill Phi cycles */
1018 remove_phi_cycles(irg);
1022 rem = current_ir_graph;
1023 current_ir_graph = irg;
1025 FIRM_DBG_REGISTER(dbg, "firm.opt.osr");
1027 DB((dbg, LEVEL_1, "Doing Operator Strength Reduction for %+F\n", irg));
1029 obstack_init(&env.obst);
1030 env.stack = NEW_ARR_F(ir_node *, 128);
1034 env.quad_map = new_set(quad_cmp, 64);
1035 env.lftr_edges = new_set(LFTR_cmp, 64);
1037 env.lftr_replaced = 0;
1039 env.process_scc = process_scc;
1041 /* Clear all links and move Proj nodes into the
1042 the same block as it's predecessors.
1043 This can improve the placement of new nodes.
1045 irg_walk_graph(irg, NULL, clear_and_fix, NULL);
1047 /* we need dominance */
1049 assure_irg_outs(irg);
1051 /* calculate the post order number for blocks. */
1052 irg_out_block_walk(get_irg_start_block(irg), NULL, assign_po, &env);
1054 /* calculate the SCC's and drive OSR. */
1058 /* try linear function test replacements */
1061 set_irg_outs_inconsistent(irg);
1062 DB((dbg, LEVEL_1, "Replacements: %u + %u (lftr)\n\n", env.replaced, env.lftr_replaced));
1065 del_set(env.lftr_edges);
1066 del_set(env.quad_map);
1067 DEL_ARR_F(env.stack);
1068 obstack_free(&env.obst, NULL);
1070 current_ir_graph = rem;
1073 /* Remove any Phi cycles with only one real input. */
1074 void remove_phi_cycles(ir_graph *irg) {
1078 rem = current_ir_graph;
1079 current_ir_graph = irg;
1081 FIRM_DBG_REGISTER(dbg, "firm.opt.remove_phi");
1083 DB((dbg, LEVEL_1, "Doing Phi cycle removement for %+F\n", irg));
1085 obstack_init(&env.obst);
1086 env.stack = NEW_ARR_F(ir_node *, 128);
1090 env.quad_map = NULL;
1091 env.lftr_edges = NULL;
1093 env.lftr_replaced = 0;
1095 env.process_scc = process_phi_only_scc;
1097 /* Clear all links and move Proj nodes into the
1098 the same block as it's predecessors.
1099 This can improve the placement of new nodes.
1101 irg_walk_graph(irg, NULL, clear_and_fix, NULL);
1103 /* we need dominance */
1104 assure_irg_outs(irg);
1106 /* calculate the post order number for blocks. */
1107 irg_out_block_walk(get_irg_start_block(irg), NULL, assign_po, &env);
1109 /* calculate the SCC's and drive OSR. */
1113 set_irg_outs_inconsistent(irg);
1114 DB((dbg, LEVEL_1, "remove_phi_cycles: %u Cycles removed\n\n", env.replaced));
1117 DEL_ARR_F(env.stack);
1118 obstack_free(&env.obst, NULL);
1120 current_ir_graph = rem;