Patch to the gcc version 2.95.3

[Marcio de Oliveira Buss <ra990898 at ic dot unicamp dot br>]

  gcc version 2.95.2 presents two bugs in the source code of
  the function compute_dominators, located at the file flow.c
  I think this patch could be inserted in the version 2.95.3
  to correct the problem.

  The explanation follows:

  The algorithm to compute dominators in the CFG begins its for
  loop with the first basic block after the entry block. In the case 
  of gcc, this is the block 0. In the Muchnick's book page 182 one can
  found such algorithm, which begins with the basic block namely 1  
  because this is its first block after the entry block. But in the
  case of gcc, it is not the case.


*** flow.c      Wed Aug  4 04:09:48 1999
--- flow2.c     Thu Jul  6 17:11:16 2000

***************
*** 4652,4658 ****
    while (changed)
      {
        changed = 0;
!       for (bb = 1; bb < n_basic_blocks; bb++)
        {
           sbitmap_intersect_of_predecessors (temp_bitmap[bb],dominators,
                                              bb, s_preds);
--- 4652,4658 ----
    while (changed)
      {
        changed = 0;
!       for (bb = 0; bb < n_basic_blocks; bb++)
        {
          sbitmap_intersect_of_predecessors (temp_bitmap[bb], dominators,
                                             bb, s_preds);



  Also, the block indexed by n_basic_blocks - 1 can only postdominates
  itself in the beginning of the computation. But in the actual 
  implementation, the block 0 is initially marked as post-dominating
  the basic block `n_basic_blocks - 1'.



***************
*** 4645,4651 ****
    SET_BIT (dominators[0], 0);
  
    sbitmap_zero (post_dominators[n_basic_blocks - 1]);
!   SET_BIT (post_dominators[n_basic_blocks - 1], 0);
  
    passes = 0;
    changed = 1;
--- 4645,4651 ----
    SET_BIT (dominators[0], 0);
  
    sbitmap_zero (post_dominators[n_basic_blocks - 1]);
!   SET_BIT (post_dominators[n_basic_blocks - 1], n_basic_block - 1);
  
    passes = 0;
    changed = 1;




    ChangeLog:

    Thu Jul 06 17:57:07 2000  Marcio Buss  (marcio.buss@ic.unicamp.br)

    * flow.c (compute_dominators) : Starts the algorithm with the
    first basic block after the entry block, in the case, 0.
    Mark n_basic_blocks-1 as initially postdominating itself.