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