[Bug gprof/13993] New: gprof failed to accumulate hist time

[manjian2006 at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=13993

             Bug #: 13993
           Summary: gprof failed to accumulate hist time
           Product: binutils
           Version: 2.22
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gprof
        AssignedTo: address@hidden
        ReportedBy: address@hidden
    Classification: Unclassified


This bug occurred in hist_assign_samples_1 which is located in hist.c.When
bin_high_pc < sym_low_pc was true at first hit,the variable j kept decreasing
until it overflowed.No symbol would be find in this situation.The following is
my fix of this bug,may harm the  performance.


static void
hist_assign_samples_1 (histogram *r)
{
  bfd_vma bin_low_pc, bin_high_pc;
  bfd_vma sym_low_pc, sym_high_pc;
  bfd_vma overlap, addr;
  unsigned int bin_count;
  unsigned int i;
  double count_time, credit;

  bfd_vma lowpc = r->lowpc / sizeof (UNIT);

  /* Iterate over all sample bins.  */
  for (i = 0; i < r->num_bins; ++i)
    {
        unsigned int j;
      bin_count = r->sample[i];
      if (! bin_count)
    continue;

      bin_low_pc = lowpc + (bfd_vma) (hist_scale * i);
      bin_high_pc = lowpc + (bfd_vma) (hist_scale * (i + 1));
      count_time = bin_count;

      DBG (SAMPLEDEBUG,
       printf (
      "[assign_samples] bin_low_pc=0x%lx, bin_high_pc=0x%lx, bin_count=%u\n",
            (unsigned long) (sizeof (UNIT) * bin_low_pc),
            (unsigned long) (sizeof (UNIT) * bin_high_pc),
            bin_count));
      total_time += count_time;

      /* Credit all symbols that are covered by bin I.  */
      for (j = 1; j < symtab.len; ++j)
    {
      sym_low_pc = symtab.base[j].hist.scaled_addr;
      sym_high_pc = symtab.base[j + 1].hist.scaled_addr;

      /* If high end of bin is below entry address,
         go for next bin.  */
      if (bin_high_pc < sym_low_pc)
      {
          j++;
        break;
      }

      /* If low end of bin is above high end of symbol,
         go for next symbol.  */
      if (bin_low_pc >= sym_high_pc)
        continue;

      overlap =
        MIN (bin_high_pc, sym_high_pc) - MAX (bin_low_pc, sym_low_pc);
      if (overlap > 0)
        {
          DBG (SAMPLEDEBUG,
           printf (
           "[assign_samples] [0x%lx,0x%lx) %s gets %f ticks %ld overlap\n",
               (unsigned long) symtab.base[j].addr,
               (unsigned long) (sizeof (UNIT) * sym_high_pc),
               symtab.base[j].name, overlap * count_time / hist_scale,
               (long) overlap));

          addr = symtab.base[j].addr;
          credit = overlap * count_time / hist_scale;

          /* Credit symbol if it appears in INCL_FLAT or that
         table is empty and it does not appear it in
         EXCL_FLAT.  */
          if (sym_lookup (&syms[INCL_FLAT], addr)
          || (syms[INCL_FLAT].len == 0
              && !sym_lookup (&syms[EXCL_FLAT], addr)))
        {
          symtab.base[j].hist.time += credit;
        }
          else
        {
          total_time -= credit;
        }
        }
    }
    }

  DBG (SAMPLEDEBUG, printf ("[assign_samples] total_time %f\n",
                total_time));
}

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