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

   1 /*
   2  * This file is part of libFirm.
   3  * Copyright (C) 2012 University of Karlsruhe.
   4  */
   5
   6 /**
   7  * @file
   8  * @brief       Algorithms for computing dominance frontiers.
   9  * @author      Sebastian Hack, Daniel Grund
  10  * @date        04.05.2005
  11  */
  12 #include "config.h"
  13
  14 #include "obst.h"
  15 #include "pmap.h"
  16 #include "pdeq.h"
  17 #include "irdom.h"
  18 #include "array.h"
  19 #include "irgraph.h"
  20 #include "iredges_t.h"
  21 #include "irnodeset.h"
  22
  23 /**
  24  * A wrapper for get_Block_idom.
  25  * This function returns the block itself, if the block is the start
  26  * block. Returning NULL would make any != comparison true which
  27  * suggests, that the start block is dominated by some other node.
  28  * @param bl The block.
  29  * @return The immediate dominator of the block.
  30  */
  31 static inline ir_node *get_idom(ir_node *bl)
  32 {
  33         ir_node *idom = get_Block_idom(bl);
  34         return idom == NULL ? bl : idom;
  35 }
  36
  37 /**
  38  * Compute the dominance frontier for a given block.
  39  *
  40  * @param blk   the block where the calculation starts
  41  *
  42  * @return the list of all blocks in the dominance frontier of blk
  43  */
  44 static ir_node **compute_df(ir_node *blk, ir_dom_front_info_t *info)
  45 {
  46         ir_node *c;
  47         ir_node **df_list = NEW_ARR_F(ir_node *, 0);
  48
  49         /* Add local dominance frontiers */
  50         foreach_block_succ(blk, edge) {
  51                 ir_node *y = get_edge_src_irn(edge);
  52
  53                 if (get_idom(y) != blk) {
  54                         ARR_APP1(ir_node *, df_list, y);
  55                 }
  56         }
  57
  58         /*
  59          * Go recursively down the dominance tree and add all blocks
  60          * into the dominance frontiers of the children, which are not
  61          * dominated by the given block.
  62          */
  63         for (c = get_Block_dominated_first(blk); c; c = get_Block_dominated_next(c)) {
  64                 size_t i;
  65                 ir_node **df_c_list = compute_df(c, info);
  66
  67                 for (i = ARR_LEN(df_c_list); i > 0;) {
  68                         ir_node *w = df_c_list[--i];
  69                         if (get_idom(w) != blk)
  70                                 ARR_APP1(ir_node *, df_list, w);
  71                 }
  72         }
  73
  74         /* now copy the flexible array to the obstack */
  75         ir_node **const df = DUP_ARR_D(ir_node*, &info->obst, df_list);
  76         DEL_ARR_F(df_list);
  77
  78         pmap_insert(info->df_map, blk, df);
  79         return df;
  80 }
  81
  82 void ir_compute_dominance_frontiers(ir_graph *irg)
  83 {
  84         ir_dom_front_info_t *info = &irg->domfront;
  85
  86         assure_edges(irg);
  87         obstack_init(&info->obst);
  88         info->df_map = pmap_create();
  89         assure_doms(irg);
  90         compute_df(get_irg_start_block(irg), info);
  91
  92         add_irg_properties(irg, IR_GRAPH_PROPERTY_CONSISTENT_DOMINANCE_FRONTIERS);
  93 }
  94
  95 void ir_free_dominance_frontiers(ir_graph *irg)
  96 {
  97         clear_irg_properties(irg, IR_GRAPH_PROPERTY_CONSISTENT_DOMINANCE_FRONTIERS);
  98
  99         ir_dom_front_info_t *info = &irg->domfront;
 100         if (info->df_map == NULL)
 101                 return;
 102
 103         obstack_free(&info->obst, NULL);
 104         pmap_destroy(info->df_map);
 105         info->df_map = NULL;
 106 }
 107
 108 /* Get the dominance frontier of a block. */
 109 ir_node **ir_get_dominance_frontier(const ir_node *block)
 110 {
 111         ir_graph            *irg  = get_irn_irg(block);
 112         ir_dom_front_info_t *info = &irg->domfront;
 113         return pmap_get(ir_node*, info->df_map, block);
 114 }