[Bug target/39760] New: register allocation costs are not well described on AVR

[bonzini at gnu dot org]

The same alternative can produce very different instruction sequences.  For
example:

  if (compare_sign_p (insn))
    {
      if (l) *l = 1;
      return AS1 (tst,%B0);
    }
  if (reg_unused_after (insn, op)
      && compare_eq_p (insn))
    {
      /* Faster than sbiw if we can clobber the operand.  */
      if (l) *l = 1;
      return AS2 (or,%A0,%B0);
    }
  if (test_hard_reg_class (ADDW_REGS, op))
    {
      if (l) *l = 1;
      return AS2 (sbiw,%0,0);
    }
  if (l) *l = 2;
  return (AS2 (cp,%A0,__zero_reg__) CR_TAB
          AS2 (cpc,%B0,__zero_reg__));


-- 
           Summary: register allocation costs are not well described on AVR
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bonzini at gnu dot org
GCC target triplet: avr-*-*


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39760