Added ssa destruction. TODO: Perm placement.

[libfirm] / ir / be / beirgmod.c

#include <stdlib.h>

#include "hashptr.h"
#include "pdeq.h"
#include "pset.h"
#include "pmap.h"

#include "irflag_t.h"
#include "ircons_t.h"
#include "irnode_t.h"
#include "irmode_t.h"
#include "irdom_t.h"
#include "iredges_t.h"

#include "besched_t.h"
#include "beirgmod.h"

struct _dom_front_info_t {
  pmap *df_map;
};

static void compute_df_local(ir_node *bl, void *data)
{
  pmap *df_map = ((dom_front_info_t *) data)->df_map;
  ir_node *idom = get_Block_idom(bl);
  int i, n;

  for(i = 0, n = get_irn_arity(bl); i < n; ++i) {

    /* The predecessor block */
    ir_node *pred = get_nodes_block(get_irn_n(bl, i));

    /* The dominance frontier set of the predecessor. */
    pset *df = pmap_get(df_map, pred);

    /*
     * Create the dominance frontier set of the predecessor
     * if it didn't exist.
     */
    if(!df) {
      df = pset_new_ptr(16);
      pmap_insert(df_map, pred, df);
    }


    if(pred != idom && bl)
      pset_insert_ptr(df, bl);
  }
}

static void compute_df_up(ir_node *bl, void *data)
{
  pmap *df_map = ((dom_front_info_t *) data)->df_map;
  ir_node *y;

  for(y = get_Block_dominated_first(bl); y; y = get_Block_dominated_next(y)) {
    ir_node *w;
    pset *df = pmap_get(df_map, y);

    for(w = pset_first(df); df; w = pset_next(df))
      if(!block_dominates(bl, w) || bl == w)
        pset_insert_ptr(df, w);
  }
}

dom_front_info_t *be_compute_dominance_frontiers(ir_graph *irg)
{
  dom_front_info_t *info = malloc(sizeof(*info));

  info->df_map = pmap_create();

  /* Perhaps both can we interwined */
  dom_tree_walk_irg(irg, compute_df_local, NULL, info);
  dom_tree_walk_irg(irg, NULL, compute_df_up, info);
  return info;
}

void be_free_dominance_frontiers(dom_front_info_t *info)
{
  pmap_entry *ent;

  for(ent = pmap_first(info->df_map); ent; ent = pmap_next(info->df_map))
    del_pset(ent->value);

  pmap_destroy(info->df_map);
  free(info);
}

pset *be_get_dominance_frontier(dom_front_info_t *info, ir_node *block)
{
  return pmap_get(info->df_map, block);
}

/**
 * Algorithm to place the Phi-Functions.
 * @see Appel, Modern Compiler Implementation in Java, 2nd ed., p. 399ff
 *
 * This function takes an original node and a set of already placed
 * copies of that node called @p copies. It places phi nodes at the
 * iterated dominance frontiers of these copies and puts these phi nodes
 * in the @p copies set, since they are another form of copies of the
 * original value.
 *
 * The rename phase (see below) is responsible for fixing up the usages
 * of the original node.
 *
 * @param orig The original node.
 * @param copies A set contianing nodes representing a copy of the
 * original node. Each node must be inserted into the block's schedule.
 * @param copy_blocks A set in which the blocks are recorded which
 * contain a copy. This is just for efficiency in later phases (see
 * rename).
 */
static void place_phi_functions(ir_node *orig, pset *copies,
    pset *copy_blocks, dom_front_info_t *df_info)
{
  int i;
  ir_node *orig_block = get_nodes_block(orig);
  ir_graph *irg = get_irn_irg(orig);
  ir_mode *mode = get_irn_mode(orig);
  pdeq *worklist = new_pdeq();
  pset *phi_blocks = pset_new_ptr(8);
  ir_node **ins = NULL;
  void *it;

  /*
   * Allocate an array for all blocks where the copies and the original
   * value were defined.
   */
  int n_orig_blocks = pset_count(copy_blocks) + 1;
  ir_node **orig_blocks = malloc(n_orig_blocks * sizeof(orig_blocks[0]));

  /*
   * Fill the array of definition blocks.
   */
  orig_blocks[0] = get_nodes_block(orig);

  /*
   * Fill the worklist queue and the rest of the orig blocks array.
   */
  for(it = pset_first(copies), i = 1; it; it = pset_next(copies)) {
    ir_node *copy_block = get_nodes_block(it);

    assert(block_dominates(orig_block, copy_block)
        && "The block of the copy must be dominated by the block of the value");

    pdeq_putr(worklist, it);
    orig_blocks[i++] = copy_block;
  }

  while(!pdeq_empty(worklist)) {
    ir_node *irn = pdeq_getl(worklist);
    ir_node *bl = get_nodes_block(irn);
    ir_node *y;
    int n_preds = get_irn_arity(bl);
    pset *df = be_get_dominance_frontier(df_info, bl);

    for(y = pset_first(df); y; y = pset_next(df)) {

      if(!pset_find_ptr(phi_blocks, y)) {
        ir_node *phi;
        int insert = 1;

        /*
         * Set the orig node as the only operand of the
         * phi node.
         */
        ins = realloc(ins, n_preds * sizeof(ins[0]));
        for(i = 0; i < n_preds; ++i)
          ins[0] = orig;

        /* Insert phi node */
        phi = new_r_Phi(irg, bl, n_preds, ins, mode);

        /*
         * The phi node itself is also a copy of the original
         * value. So put it in the copies set also, so that
         * the rename phase can treat them right.
         */
        pset_insert_ptr(copies, phi);
        pset_insert_ptr(copy_blocks, y);

        /* Insert the phi node into the schedule */
        sched_add_before(sched_first(y), phi);

        /* Insert the phi node in the phi blocks set. */
        pset_insert_ptr(phi_blocks, y);

        /*
         * If orig or a copy of it were not defined in y,
         * add y to the worklist.
         */
        for(i = 0; i < n_orig_blocks; ++i)
          if(orig_blocks[i] == y) {
            insert = 0;
            break;
          }

        if(insert)
          pdeq_putr(worklist, y);

      }
    }
  }

  del_pset(phi_blocks);
  del_pdeq(worklist);

  free(orig_blocks);

  if(ins)
    free(ins);
}

/**
 * Find the copy of the given original node whose value is 'active'
 * at a usage.
 *
 * The usage is given as a node and a position. Initially, the given operand
 * points to a node for which copies were introduced. We have to find
 * the valid copy for this usage. This is done by travering the
 * dominance tree upwards. If the usage is a phi function, we start
 * traversing from the predecessor block which corresponds to the phi
 * usage.
 *
 * @param usage The node which uses the original node.
 * @param pos The number of the argument which corresponds to the
 * original node.
 * @param copy_blocks A set containing all basic block in which copies
 * of the original node are located.
 * @param copies A set containing all node which are copies from the
 * original node.
 * @return The valid copy for usage.
 */
static ir_node *search_def(ir_node *usage, int pos, pset *copies, pset *copy_blocks)
{
  ir_node *curr_bl;

  curr_bl = get_nodes_block(usage);

  /*
   * If the usage is in a phi node, search the copy in the
   * predecessor denoted by pos.
   */
  if(is_Phi(usage))
    curr_bl = get_nodes_block(get_irn_n(curr_bl, pos));

  /*
   * Traverse the dominance tree upwards from the
   * predecessor block of the usage.
   */
  while(curr_bl != NULL) {

    /*
     * If this block contains a copy, search the block
     * instruction by instruction.
     */
    if(pset_find_ptr(copy_blocks, curr_bl)) {
      ir_node *irn;

      /* Look at each instruction from last to first. */
      sched_foreach_reverse(curr_bl, irn) {

        /* Take the first copy we find. */
        if(pset_find_ptr(copies, irn))
          return irn;
      }

      assert(0 && "We must have encountered a copy");
    }

    /* If were not done yet, look in the immediate dominator */
    curr_bl = get_Block_idom(curr_bl);
  }

  return NULL;
}


static void fix_usages(ir_node *orig, pset *copies, pset *copy_blocks)
{
  int i;
  int n_outs = 0;
  const ir_edge_t *edge;
  const ir_edge_t **outs;

  /* Count the number of outs. */
  foreach_out_edge(orig, edge)
    n_outs++;

  /*
   * Put all outs into an array.
   * This is neccessary, since the outs would be modified while
   * interating on them what could bring the outs module in trouble.
   */
  outs = malloc(n_outs * sizeof(outs[0]));
  foreach_out_edge(orig, edge)
    outs[i++] = edge;

  /*
   * Search the valid def for each out and set it.
   */
  for(i = 0; i < n_outs; ++i) {
    ir_node *def;
    ir_node *irn = get_edge_src_irn(outs[i]);
    int pos = get_edge_src_pos(outs[i]);

    def = search_def(irn, pos, copies, copy_blocks);
    set_irn_n(irn, pos, def);
  }

  free(outs);
}

void be_introduce_copies(dom_front_info_t *info, ir_node *orig, int n, ir_node *copy_nodes[])
{
  pset *copies = pset_new_ptr(2 * n);
  pset *copy_blocks = pset_new_ptr(2 * n);
  int save_optimize = get_optimize();
  int i;

  /* Fill the sets. */
  for(i = 0; i < n; ++i) {
    pset_insert_ptr(copies, copy_nodes[i]);
    pset_insert_ptr(copy_blocks, get_nodes_block(copy_nodes[i]));
  }

  /*
   * Disable optimization so that the phi functions do not
   * disappear.
   */
  set_optimize(0);

  /*
   * Place the phi functions and reroute the usages.
   */
  place_phi_functions(orig, copies, copy_blocks, info);
  fix_usages(orig, copies, copy_blocks);

  /* reset the optimizations */
  set_optimize(save_optimize);

  del_pset(copies);
  del_pset(copy_blocks);
}