[Bug target/31137] New: missing "break" in switch for MULT in avr_rtx_costs

["christer at weinigel dot se" <gcc-bugzilla at gcc dot gnu dot org>]

I have just started reading the gcc code a bit, and while looking at the avr
port I noticed that in the function avr_rtx_costs in avr.c there is some code
to calculate the cost of a multiplication:

    case MULT:
      switch (mode)
        {
        case QImode:
          if (AVR_HAVE_MUL)
            *total = COSTS_N_INSNS (optimize_size ? 3 : 4);
          else if (optimize_size)
            *total = COSTS_N_INSNS (AVR_MEGA ? 2 : 1);
          else
            return false;

        case HImode:
          if (AVR_HAVE_MUL)
            *total = COSTS_N_INSNS (optimize_size ? 7 : 10);
          else if (optimize_size)
            *total = COSTS_N_INSNS (AVR_MEGA ? 2 : 1);
          else
            return false;

        default:
          return false;
        }
      *total += avr_operand_rtx_cost (XEXP (x, 0), mode, code);
      *total += avr_operand_rtx_cost (XEXP (x, 1), mode, code);
      return true;

if AVR_HAVE_MUL is true, the above code will be equal to the following:

    case MULT:
      switch (mode)
        {
        case QImode:
          *total = COSTS_N_INSNS (optimize_size ? 3 : 4);

        case HImode:
          *total = COSTS_N_INSNS (optimize_size ? 7 : 10);

        default:
          return false;
        }
      *total += avr_operand_rtx_cost (XEXP (x, 0), mode, code);
      *total += avr_operand_rtx_cost (XEXP (x, 1), mode, code);
      return true;

which I belive is incorrect since it means that the assignments to *total in
the switch statement are useless.  It probably doesn't break anything serious
but might give slightly worse optimizations.


-- 
           Summary: missing "break" in switch for MULT in avr_rtx_costs
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: christer at weinigel dot se
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: avr-unknown-none


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31137