nsz Git - libfirm/blob - ir/ana/irdom.c

   1 /*
   2  * Project:     libFIRM
   3  * File name:   ir/ana/irdom.c
   4  * Purpose:     Construct and access dominator tree.
   5  * Author:      Goetz Lindenmaier
   6  * Modified by:
   7  * Created:     2.2002
   8  * CVS-ID:      $Id$
   9  * Copyright:   (c) 2002-2003 Universität Karlsruhe
  10  * Licence:     This file protected by GPL -  GNU GENERAL PUBLIC LICENSE.
  11  */
  12
  13 #ifdef HAVE_CONFIG_H
  14 #include "config.h"
  15 #endif
  16
  17 #ifdef HAVE_STRING_H
  18 #include <string.h>
  19 #endif
  20
  21 #include "irouts.h"
  22
  23 #include "xmalloc.h"
  24 #include "irgwalk.h"
  25 #include "irdom_t.h"
  26 #include "irgraph_t.h"   /* To access state field. */
  27 #include "irnode_t.h"
  28 #include "ircons_t.h"
  29
  30
  31 #define get_dom_info(bl) (&(bl)->attr.block.dom)
  32
  33 /*--------------------------------------------------------------------*/
  34 /** Accessing the dominator data structures                          **/
  35 /*--------------------------------------------------------------------*/
  36
  37 ir_node *get_Block_idom(const ir_node *bl) {
  38   assert(is_Block(bl));
  39   if (get_Block_dom_depth(bl) == -1) {
  40     /* This block is not reachable from Start */
  41     return new_Bad();
  42   }
  43   return get_dom_info(bl)->idom;
  44 }
  45
  46 void set_Block_idom(ir_node *bl, ir_node *n) {
  47         dom_info *bli = get_dom_info(bl);
  48
  49   assert(get_irn_op(bl) == op_Block);
  50
  51         /* Set the immediate dominator of bl to n */
  52         bli->idom = n;
  53
  54         /*
  55          * If we don't set the root of the dominator tree
  56          * Append bl to the dominates queue of n.
  57          */
  58         if(n != NULL) {
  59                 dom_info *ni = get_dom_info(n);
  60
  61                 bli->next = ni->first;
  62                 ni->first = bl;
  63         }
  64 }
  65
  66 int get_Block_pre_num(const ir_node *bl) {
  67   assert(get_irn_op(bl) == op_Block);
  68   return bl->attr.block.dom.pre_num;
  69 }
  70
  71 void set_Block_pre_num(ir_node *bl, int num) {
  72   assert(get_irn_op(bl) == op_Block);
  73   bl->attr.block.dom.pre_num = num;
  74 }
  75
  76 int get_Block_dom_depth(const ir_node *bl) {
  77   assert(get_irn_op(bl) == op_Block);
  78   return bl->attr.block.dom.dom_depth;
  79 }
  80
  81 void set_Block_dom_depth(ir_node *bl, int depth) {
  82   assert(get_irn_op(bl) == op_Block);
  83   bl->attr.block.dom.dom_depth = depth;
  84 }
  85
  86 unsigned get_Block_dom_tree_pre_num(const ir_node *bl)
  87 {
  88         assert(is_Block(bl));
  89         return get_dom_info(bl)->tree_pre_num;
  90 }
  91
  92 unsigned get_Block_dom_max_subtree_pre_num(const ir_node *bl)
  93 {
  94         assert(is_Block(bl));
  95         return get_dom_info(bl)->max_subtree_pre_num;
  96 }
  97
  98 int block_dominates(const ir_node *a, const ir_node *b)
  99 {
 100         const dom_info *ai, *bi;
 101
 102         if (is_Block(a) && is_Block(b)) {
 103                 ai = get_dom_info(a);
 104                 bi = get_dom_info(b);
 105                 return bi->tree_pre_num - ai->tree_pre_num
 106                         <= ai->max_subtree_pre_num - ai->tree_pre_num;
 107         }
 108
 109         return 0;
 110 }
 111
 112 ir_node *get_Block_dominated_first(const ir_node *bl)
 113 {
 114         assert(is_Block(bl));
 115         return get_dom_info(bl)->first;
 116 }
 117
 118 ir_node *get_Block_dominated_next(const ir_node *bl)
 119 {
 120         assert(is_Block(bl));
 121         return get_dom_info(bl)->next;
 122 }
 123
 124 void dom_tree_walk(ir_node *bl, irg_walk_func *pre,
 125                 irg_walk_func *post, void *env)
 126 {
 127         ir_node *p;
 128
 129         if(pre)
 130                 pre(bl, env);
 131
 132         dominates_for_each(bl, p) {
 133                 dom_tree_walk(p, pre, post, env);
 134         }
 135
 136         if(post)
 137                 post(bl, env);
 138 }
 139
 140 void dom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
 141                 irg_walk_func *post, void *env)
 142 {
 143         /* The root of the dominator tree should be the start node. */
 144         ir_node *root = get_irg_start_block(irg);
 145
 146   assert(irg->dom_state == dom_consistent
 147                         && "The dominators of the irg must be consistent");
 148         assert(root && "The start block of the graph is NULL?");
 149         assert(get_dom_info(root)->idom == NULL
 150                         && "The start node in the graph must be the root of the dominator tree");
 151         dom_tree_walk(root, pre, post, env);
 152 }
 153
 154 static void assign_tree_pre_order(ir_node *bl, void *data)
 155 {
 156         unsigned *num = data;
 157         dom_info *bi = get_dom_info(bl);
 158
 159         bi->tree_pre_num = (*num)++;
 160 }
 161
 162 static void assign_tree_pre_order_max(ir_node *bl, void *data)
 163 {
 164         dom_info *bi = get_dom_info(bl);
 165         ir_node *p;
 166         unsigned max = 0;
 167         unsigned children = 0;
 168
 169         for(p = bi->first; p; p = get_dom_info(p)->next) {
 170                 unsigned max_p = get_dom_info(p)->max_subtree_pre_num;
 171                 max = max > max_p ? max : max_p;
 172                 children++;
 173         }
 174
 175         bi->max_subtree_pre_num = children > 0 ? max : bi->tree_pre_num;
 176         assert(bi->max_subtree_pre_num >= bi->tree_pre_num);
 177 }
 178
 179 /*--------------------------------------------------------------------*/
 180 /*  Building and Removing the dominator datastructure                 */
 181 /*--------------------------------------------------------------------*/
 182
 183 static void count_and_init_blocks(ir_node *bl, void *env) {
 184   int *n_blocks = (int *) env;
 185   (*n_blocks) ++;
 186
 187         memset(get_dom_info(bl), 0, sizeof(dom_info));
 188   set_Block_idom(bl, NULL);
 189   set_Block_pre_num(bl, -1);
 190   set_Block_dom_depth(bl, -1);
 191 }
 192
 193 /* temporary type used while constructing the dominator tree. */
 194 typedef struct tmp_dom_info {
 195   ir_node *block;               /* backlink */
 196
 197   struct tmp_dom_info *semi;    /* semidominator */
 198   struct tmp_dom_info *parent;
 199   struct tmp_dom_info *label;   /* used for LINK and EVAL */
 200   struct tmp_dom_info *ancestor;/* used for LINK and EVAL */
 201   struct tmp_dom_info *dom;     /* After step 3, if the semidominator of w is
 202                                    its immediate dominator, then w->dom is the
 203                                    immediate dominator of w.  Otherwise w->dom
 204                                    is a vertex v whose number is smaller than
 205                                    w and whose immediate dominator is also w's
 206                                    immediate dominator. After step 4, w->dom
 207                                    is the immediate dominator of w.  */
 208   struct tmp_dom_info *bucket;  /* set of vertices with same semidominator */
 209 } tmp_dom_info;
 210
 211 /* Struct to pass info through walker. */
 212 typedef struct {
 213   tmp_dom_info *d;
 214   int used;
 215
 216 } dom_env;
 217
 218
 219 /* Walks Blocks along the out datastructure.  If recursion started with
 220    Start block misses control dead blocks. */
 221 static void init_tmp_dom_info(ir_node *bl, tmp_dom_info *parent,
 222                               tmp_dom_info *tdi_list, int* used) {
 223   tmp_dom_info *tdi;
 224   int i;
 225
 226   assert(get_irn_op(bl) == op_Block);
 227   if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
 228     return;
 229   mark_Block_block_visited(bl);
 230   set_Block_pre_num(bl, *used);
 231
 232   tdi = &tdi_list[*used];
 233   ++(*used);
 234
 235   tdi->semi = tdi;
 236   tdi->label = tdi;
 237   tdi->ancestor = NULL;
 238   tdi->bucket = NULL;
 239   tdi->parent = parent;
 240   tdi->block = bl;
 241
 242   /* Iterate */
 243   for(i = 0; i < get_Block_n_cfg_outs(bl); i++) {
 244     ir_node *pred = get_Block_cfg_out(bl, i);
 245     assert(get_irn_opcode(pred) == iro_Block);
 246     init_tmp_dom_info(pred, tdi, tdi_list, used);
 247   }
 248 }
 249
 250 static void
 251 dom_compress (tmp_dom_info *v)
 252 {
 253   assert (v->ancestor);
 254   if (v->ancestor->ancestor) {
 255     dom_compress (v->ancestor);
 256     if (v->ancestor->label->semi < v->label->semi) {
 257       v->label = v->ancestor->label;
 258     }
 259     v->ancestor = v->ancestor->ancestor;
 260   }
 261 }
 262
 263 /* if V is a root, return v, else return the vertex u, not being the
 264    root, with minimum u->semi on the path from v to its root. */
 265 INLINE static tmp_dom_info*
 266 dom_eval (tmp_dom_info *v)
 267 {
 268   if (!v->ancestor) return v;
 269   dom_compress (v);
 270   return v->label;
 271 }
 272
 273 /* make V W's ancestor */
 274 INLINE static void
 275 dom_link (tmp_dom_info *v, tmp_dom_info *w)
 276 {
 277   w->ancestor = v;
 278 }
 279
 280 /* Computes the dominator trees.  Sets a flag in irg to "dom_consistent".
 281    If the control flow of the graph is changed this flag must be set to
 282    "dom_inconsistent".  */
 283 void compute_doms(ir_graph *irg) {
 284   ir_graph *rem = current_ir_graph;
 285   int n_blocks, used, i, j;
 286   tmp_dom_info *tdi_list;   /* Ein Golf? */
 287
 288   current_ir_graph = irg;
 289
 290   /* Update graph state */
 291   assert(get_irg_phase_state(current_ir_graph) != phase_building);
 292   current_ir_graph->dom_state = dom_consistent;
 293
 294   /* Count the number of blocks in the graph. */
 295   n_blocks = 0;
 296   irg_block_walk(get_irg_end(current_ir_graph), count_and_init_blocks, NULL, &n_blocks);
 297
 298   /* Memory for temporary information. */
 299   tdi_list = xcalloc(n_blocks, sizeof(tdi_list[0]));
 300
 301   /* We need the out datastructure. */
 302   if (current_ir_graph->outs_state != outs_consistent)
 303     compute_outs(current_ir_graph);
 304
 305   /* this with a standard walker as passing the parent to the sons isn't
 306      simple. */
 307   used = 0;
 308   inc_irg_block_visited(current_ir_graph);
 309   init_tmp_dom_info(get_irg_start_block(current_ir_graph), NULL, tdi_list, &used);
 310   /* If not all blocks are reachable from Start by out edges this assertion
 311      fails.
 312      assert(used == n_blocks && "Precondition for dom construction violated"); */
 313   n_blocks = used;
 314
 315
 316   for (i = n_blocks-1; i > 0; i--) {  /* Don't iterate the root, it's done. */
 317     int irn_arity;
 318     tmp_dom_info *w = &tdi_list[i];
 319     tmp_dom_info *v;
 320
 321     /* Step 2 */
 322     irn_arity = get_irn_arity(w->block);
 323     for (j = 0;  j < irn_arity;  j++) {
 324       ir_node *pred = get_Block_cfgpred_block(w->block, j);
 325       tmp_dom_info *u;
 326
 327       if (is_Bad(pred) || (get_Block_pre_num (pred) == -1))
 328         continue;       /* control-dead */
 329
 330       u = dom_eval (&tdi_list[get_Block_pre_num(pred)]);
 331       if (u->semi < w->semi) w->semi = u->semi;
 332     }
 333     /* Add w to w->semi's bucket.  w is in exactly one bucket, so
 334        buckets can ben implemented as linked lists. */
 335     w->bucket = w->semi->bucket;
 336     w->semi->bucket = w;
 337
 338     dom_link (w->parent, w);
 339
 340     /* Step 3 */
 341     while (w->parent->bucket) {
 342       tmp_dom_info *u;
 343       v = w->parent->bucket;
 344       /* remove v from w->parent->bucket */
 345       w->parent->bucket = v->bucket;
 346       v->bucket = NULL;
 347
 348       u = dom_eval (v);
 349       if (u->semi < v->semi)
 350         v->dom = u;
 351       else
 352         v->dom = w->parent;
 353     }
 354   }
 355   /* Step 4 */
 356   tdi_list[0].dom = NULL;
 357   set_Block_idom(tdi_list[0].block, NULL);
 358   set_Block_dom_depth(tdi_list[0].block, 1);
 359   for (i = 1;  i < n_blocks;  i++) {
 360     tmp_dom_info *w = &tdi_list[i];
 361
 362     if (w->dom != w->semi) w->dom = w->dom->dom;
 363     set_Block_idom(w->block, w->dom->block);
 364     set_Block_dom_depth(w->block, get_Block_dom_depth(w->dom->block) + 1);
 365   }
 366
 367   /* clean up */
 368   /*  free(tdi_list); @@@ does not work !!?? */
 369   current_ir_graph = rem;
 370
 371         /* Do a walk over the tree and assign the tree pre orders. */
 372         {
 373                 unsigned tree_pre_order = 0;
 374                 dom_tree_walk_irg(irg, assign_tree_pre_order,
 375                                 assign_tree_pre_order_max, &tree_pre_order);
 376         }
 377 }
 378
 379 void free_dom_and_peace(ir_graph *irg) {
 380   /* Update graph state */
 381   assert(get_irg_phase_state(current_ir_graph) != phase_building);
 382   current_ir_graph->dom_state = dom_none;
 383
 384   /* With the implementation right now there is nothing to free,
 385      but better call it anyways... */
 386 }