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 #define get_dom_info(bl) (&(bl)->attr.block.dom)
  31
  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         return 0;
 109 }
 110
 111 ir_node *get_Block_dominated_first(const ir_node *bl)
 112 {
 113         assert(is_Block(bl));
 114         return get_dom_info(bl)->first;
 115 }
 116
 117 ir_node *get_Block_dominated_next(const ir_node *bl)
 118 {
 119         assert(is_Block(bl));
 120         return get_dom_info(bl)->next;
 121 }
 122
 123 void dom_tree_walk(ir_node *bl, irg_walk_func *pre,
 124                 irg_walk_func *post, void *env)
 125 {
 126         ir_node *p;
 127
 128         if(pre)
 129                 pre(bl, env);
 130
 131         dominates_for_each(bl, p) {
 132                 dom_tree_walk(p, pre, post, env);
 133         }
 134
 135         if(post)
 136                 post(bl, env);
 137 }
 138
 139 void dom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
 140                 irg_walk_func *post, void *env)
 141 {
 142         /* The root of the dominator tree should be the start node. */
 143         ir_node *root = get_irg_start_block(irg);
 144
 145   assert(irg->dom_state == dom_consistent
 146                         && "The dominators of the irg must be consistent");
 147         assert(root && "The start block of the graph is NULL?");
 148         assert(get_dom_info(root)->idom == NULL
 149                         && "The start node in the graph must be the root of the dominator tree");
 150         dom_tree_walk(root, pre, post, env);
 151 }
 152
 153 static void assign_tree_pre_order(ir_node *bl, void *data)
 154 {
 155         unsigned *num = data;
 156         dom_info *bi = get_dom_info(bl);
 157
 158         bi->tree_pre_num = (*num)++;
 159 }
 160
 161 static void assign_tree_pre_order_max(ir_node *bl, void *data)
 162 {
 163         dom_info *bi = get_dom_info(bl);
 164         ir_node *p;
 165         unsigned max = 0;
 166         unsigned children = 0;
 167
 168         for(p = bi->first; p; p = get_dom_info(p)->next) {
 169                 unsigned max_p = get_dom_info(p)->max_subtree_pre_num;
 170                 max = max > max_p ? max : max_p;
 171                 children++;
 172         }
 173
 174         bi->max_subtree_pre_num = children > 0 ? max : bi->tree_pre_num;
 175         assert(bi->max_subtree_pre_num >= bi->tree_pre_num);
 176 }
 177
 178 /*--------------------------------------------------------------------*/
 179 /*  Building and Removing the dominator datastructure                 */
 180 /*--------------------------------------------------------------------*/
 181
 182 static void count_and_init_blocks(ir_node *bl, void *env) {
 183   int *n_blocks = (int *) env;
 184   (*n_blocks) ++;
 185
 186         memset(get_dom_info(bl), 0, sizeof(dom_info));
 187   set_Block_idom(bl, NULL);
 188   set_Block_pre_num(bl, -1);
 189   set_Block_dom_depth(bl, -1);
 190 }
 191
 192 /* temporary type used while constructing the dominator tree. */
 193 typedef struct tmp_dom_info {
 194   ir_node *block;               /* backlink */
 195
 196   struct tmp_dom_info *semi;    /* semidominator */
 197   struct tmp_dom_info *parent;
 198   struct tmp_dom_info *label;   /* used for LINK and EVAL */
 199   struct tmp_dom_info *ancestor;/* used for LINK and EVAL */
 200   struct tmp_dom_info *dom;     /* After step 3, if the semidominator of w is
 201                                    its immediate dominator, then w->dom is the
 202                                    immediate dominator of w.  Otherwise w->dom
 203                                    is a vertex v whose number is smaller than
 204                                    w and whose immediate dominator is also w's
 205                                    immediate dominator. After step 4, w->dom
 206                                    is the immediate dominator of w.  */
 207   struct tmp_dom_info *bucket;  /* set of vertices with same semidominator */
 208 } tmp_dom_info;
 209
 210 /* Struct to pass info through walker. */
 211 typedef struct {
 212   tmp_dom_info *d;
 213   int used;
 214
 215 } dom_env;
 216
 217
 218 /* Walks Blocks along the out datastructure.  If recursion started with
 219    Start block misses control dead blocks. */
 220 static void init_tmp_dom_info(ir_node *bl, tmp_dom_info *parent,
 221                               tmp_dom_info *tdi_list, int* used) {
 222   tmp_dom_info *tdi;
 223   int i;
 224
 225   assert(get_irn_op(bl) == op_Block);
 226   if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
 227     return;
 228   mark_Block_block_visited(bl);
 229   set_Block_pre_num(bl, *used);
 230
 231   tdi = &tdi_list[*used];
 232   ++(*used);
 233
 234   tdi->semi = tdi;
 235   tdi->label = tdi;
 236   tdi->ancestor = NULL;
 237   tdi->bucket = NULL;
 238   tdi->parent = parent;
 239   tdi->block = bl;
 240
 241   /* Iterate */
 242   for(i = 0; i < get_Block_n_cfg_outs(bl); i++) {
 243     ir_node *pred = get_Block_cfg_out(bl, i);
 244     assert(get_irn_opcode(pred) == iro_Block);
 245     init_tmp_dom_info(pred, tdi, tdi_list, used);
 246   }
 247 }
 248
 249 static void
 250 dom_compress (tmp_dom_info *v)
 251 {
 252   assert (v->ancestor);
 253   if (v->ancestor->ancestor) {
 254     dom_compress (v->ancestor);
 255     if (v->ancestor->label->semi < v->label->semi) {
 256       v->label = v->ancestor->label;
 257     }
 258     v->ancestor = v->ancestor->ancestor;
 259   }
 260 }
 261
 262 /* if V is a root, return v, else return the vertex u, not being the
 263    root, with minimum u->semi on the path from v to its root. */
 264 INLINE static tmp_dom_info*
 265 dom_eval (tmp_dom_info *v)
 266 {
 267   if (!v->ancestor) return v;
 268   dom_compress (v);
 269   return v->label;
 270 }
 271
 272 /* make V W's ancestor */
 273 INLINE static void
 274 dom_link (tmp_dom_info *v, tmp_dom_info *w)
 275 {
 276   w->ancestor = v;
 277 }
 278
 279 /* Computes the dominator trees.  Sets a flag in irg to "dom_consistent".
 280    If the control flow of the graph is changed this flag must be set to
 281    "dom_inconsistent".  */
 282 void compute_doms(ir_graph *irg) {
 283   ir_graph *rem = current_ir_graph;
 284   int n_blocks, used, i, j;
 285   tmp_dom_info *tdi_list;   /* Ein Golf? */
 286
 287   current_ir_graph = irg;
 288
 289   /* Update graph state */
 290   assert(get_irg_phase_state(current_ir_graph) != phase_building);
 291   current_ir_graph->dom_state = dom_consistent;
 292
 293   /* Count the number of blocks in the graph. */
 294   n_blocks = 0;
 295   irg_block_walk(get_irg_end(current_ir_graph), count_and_init_blocks, NULL, &n_blocks);
 296
 297   /* Memory for temporary information. */
 298   tdi_list = xcalloc(n_blocks, sizeof(tdi_list[0]));
 299
 300   /* We need the out datastructure. */
 301   if (current_ir_graph->outs_state != outs_consistent)
 302     compute_outs(current_ir_graph);
 303
 304   /* this with a standard walker as passing the parent to the sons isn't
 305      simple. */
 306   used = 0;
 307   inc_irg_block_visited(current_ir_graph);
 308   init_tmp_dom_info(get_irg_start_block(current_ir_graph), NULL, tdi_list, &used);
 309   /* If not all blocks are reachable from Start by out edges this assertion
 310      fails.
 311      assert(used == n_blocks && "Precondition for dom construction violated"); */
 312   n_blocks = used;
 313
 314
 315   for (i = n_blocks-1; i > 0; i--) {  /* Don't iterate the root, it's done. */
 316     int irn_arity;
 317     tmp_dom_info *w = &tdi_list[i];
 318     tmp_dom_info *v;
 319
 320     /* Step 2 */
 321     irn_arity = get_irn_arity(w->block);
 322     for (j = 0;  j < irn_arity;  j++) {
 323       ir_node *cf_op = get_Block_cfgpred(w->block, j);
 324       ir_node *pred  = get_nodes_block(cf_op);
 325       tmp_dom_info *u;
 326
 327       if ((is_Bad(cf_op)) || (is_Bad(pred)) ||
 328           (get_Block_pre_num (pred) == -1))
 329         continue;       /* control-dead */
 330
 331       u = dom_eval (&tdi_list[get_Block_pre_num(pred)]);
 332       if (u->semi < w->semi) w->semi = u->semi;
 333     }
 334     /* Add w to w->semi's bucket.  w is in exactly one bucket, so
 335        buckets can ben implemented as linked lists. */
 336     w->bucket = w->semi->bucket;
 337     w->semi->bucket = w;
 338
 339     dom_link (w->parent, w);
 340
 341     /* Step 3 */
 342     while (w->parent->bucket) {
 343       tmp_dom_info *u;
 344       v = w->parent->bucket;
 345       /* remove v from w->parent->bucket */
 346       w->parent->bucket = v->bucket;
 347       v->bucket = NULL;
 348
 349       u = dom_eval (v);
 350       if (u->semi < v->semi)
 351         v->dom = u;
 352       else
 353         v->dom = w->parent;
 354     }
 355   }
 356   /* Step 4 */
 357   tdi_list[0].dom = NULL;
 358   set_Block_idom(tdi_list[0].block, NULL);
 359   set_Block_dom_depth(tdi_list[0].block, 1);
 360   for (i = 1;  i < n_blocks;  i++) {
 361     tmp_dom_info *w = &tdi_list[i];
 362
 363     if (w->dom != w->semi) w->dom = w->dom->dom;
 364     set_Block_idom(w->block, w->dom->block);
 365     set_Block_dom_depth(w->block, get_Block_dom_depth(w->dom->block) + 1);
 366   }
 367
 368   /* clean up */
 369   /*  free(tdi_list); @@@ does not work !!?? */
 370   current_ir_graph = rem;
 371
 372         /* Do a walk over the tree and assign the tree pre orders. */
 373         {
 374                 unsigned tree_pre_order = 0;
 375                 dom_tree_walk_irg(irg, assign_tree_pre_order,
 376                                 assign_tree_pre_order_max, &tree_pre_order);
 377         }
 378 }
 379
 380 void free_dom_and_peace(ir_graph *irg) {
 381   /* Update graph state */
 382   assert(get_irg_phase_state(current_ir_graph) != phase_building);
 383   current_ir_graph->dom_state = dom_none;
 384
 385   /* With the implementation right now there is nothing to free,
 386      but better call it anyways... */
 387 }