[CVS 980326]: Bug in haifa scheduler on sparc-sun-solaris2.5.1

[Manfred Hollstein]

I just observed the following behaviour:

- configure'd egcs with --enable-haifa=yes
- bootstrapped using '-O9 -funroll-all-loops'

During  `make check'  cc1  runs  into  a  tight  loop  while compiling
loop-2c.c   and       loop-2d.c    with   `-O2    -fomit-frame-pointer
-finline-functions' and      either   of      `-funroll-loops'     and
`-funroll-all-loops'.

The  loop happens in in haifa-sched.c  between lines 1786 - 1812. This
code looks like:

              while (tail >= 0)
                {
                  if (head < 0)
                    head = tail;
                  child = queue[head];
                  if (degree[child] == 0)
                    {
                      degree[child] = -1;
                      rgn_bb_table[idx++] = child;
                      BLOCK_TO_BB (child) = ++count;
                      CONTAINING_RGN (child) = nr_regions;
                      queue[head] = queue[tail--];
                      fst_edge = current_edge = OUT_EDGES (child);

                      if (fst_edge > 0)
                        {
                          do
                            {
                              --degree[TO_BLOCK (current_edge)];
                              current_edge = NEXT_OUT (current_edge);
                            }
                          while (fst_edge != current_edge);
                        }
                    }
                  else
                    --head;
                }

Attaching to   the   running cc1  showed, it's  looping   without ever
decrementing  (not   even  touching)  `tail's value.   Apparently, all
`degree[child]' are unequal 0, which simply causes decrementing `head'
and once it's < 0, re-initializing it to the yet unchanged `tail'.

Interestingly, this doesn't happen on hppa1.1-hp-hpux10.20!

Has anybody else observed similar? Any fixes available?

Thanks

manfred