nsz Git - libfirm/blob - ir/opt/critical_edges.c

   1 /*
   2  * This file is part of libFirm.
   3  * Copyright (C) 2012 University of Karlsruhe.
   4  */
   5
   6 /**
   7  * @file
   8  * @brief    Remove critical edges.
   9  * @author   Christian Schaefer, Goetz Lindenmaier, Sebastian Felis,
  10  *           Michael Beck
  11  */
  12 #include "config.h"
  13
  14 #include "irop_t.h"
  15 #include "irnode_t.h"
  16 #include "ircons.h"
  17 #include "irgwalk.h"
  18 #include "irgopt.h"
  19
  20 typedef struct cf_env {
  21         char ignore_exc_edges; /**< set if exception edges should be ignored. */
  22         char changed;          /**< flag indicates that the cf graphs has changed. */
  23 } cf_env;
  24
  25 /**
  26  * Called by walker of remove_critical_cf_edges().
  27  *
  28  * Place an empty block to an edge between a blocks of multiple
  29  * predecessors and a block of multiple successors.
  30  *
  31  * @param n   IR node
  32  * @param env Environment of walker.
  33  */
  34 static void walk_critical_cf_edges(ir_node *n, void *env)
  35 {
  36         int arity, i;
  37         ir_node *pre, *block, *jmp;
  38         cf_env *cenv = (cf_env*)env;
  39         ir_graph *irg = get_irn_irg(n);
  40
  41         /* Block has multiple predecessors */
  42         arity = get_irn_arity(n);
  43         if (arity > 1) {
  44                 if (n == get_irg_end_block(irg))
  45                         return;  /*  No use to add a block here.      */
  46
  47                 for (i = 0; i < arity; ++i) {
  48                         const ir_op *cfop;
  49
  50                         pre = get_irn_n(n, i);
  51                         /* don't count Bad's */
  52                         if (is_Bad(pre))
  53                                 continue;
  54
  55                         cfop = get_irn_op(skip_Proj(pre));
  56                         if (is_op_fragile(cfop)) {
  57                                 if (cenv->ignore_exc_edges && is_x_except_Proj(pre))
  58                                         continue;
  59                                 goto insert;
  60                         }
  61                         if (is_unknown_jump(pre)) {
  62                                 /* we can't add blocks in between ijmp and its destinations
  63                                  * TODO: What now, we can't split all critical edges because of this... */
  64                                 fprintf(stderr, "libfirm warning: Couldn't split all critical edges (compiler will probably fail now)\n");
  65                                 continue;
  66                         }
  67                         /* we don't want place nodes in the start block, so handle it like forking */
  68                         if (is_op_forking(cfop) || cfop == op_Start) {
  69                                 /* Predecessor has multiple successors. Insert new control flow edge edges. */
  70 insert:
  71                                 /* set predecessor of new block */
  72                                 block = new_r_Block(irg, 1, &pre);
  73                                 /* insert new jmp node to new block */
  74                                 jmp = new_r_Jmp(block);
  75                                 /* set successor of new block */
  76                                 set_irn_n(n, i, jmp);
  77                                 cenv->changed = 1;
  78                         }
  79                 }
  80         }
  81 }
  82
  83 void remove_critical_cf_edges_ex(ir_graph *irg, int ignore_exception_edges)
  84 {
  85         cf_env env;
  86
  87         env.ignore_exc_edges = (char)ignore_exception_edges;
  88         env.changed          = 0;
  89
  90         irg_block_walk_graph(irg, NULL, walk_critical_cf_edges, &env);
  91         if (env.changed) {
  92                 /* control flow changed */
  93                 clear_irg_properties(irg, IR_GRAPH_PROPERTY_CONSISTENT_DOMINANCE);
  94         }
  95         add_irg_properties(irg, IR_GRAPH_PROPERTY_NO_CRITICAL_EDGES);
  96 }
  97
  98 void remove_critical_cf_edges(ir_graph *irg)
  99 {
 100         remove_critical_cf_edges_ex(irg, 1);
 101 }