Hello.
I have made following changes to inspect inlining of roundeven with
the following test code:
double
plusone (double d)
{
    return __builtin_roundeven (d) + 1;
}

Running the program using -O2 foo.c gave internal compiler error which
I believe is because gcc_unreachable() at:

if (TARGET_SSE4_1)
    emit_insn (gen_sse4_1_round<mode>2
           (operands[0], operands[1], GEN_INT (ROUND_<ROUNDING>
                               | ROUND_NO_EXC)));
I think the following condition matches the criterion? :
> I think the code will be much clearer if it explicitly says
> ROUND_ROUNDEVEN | ROUND_NO_EXC,

     else if (TARGET_64BIT || (<MODE>mode != DFmode))
    {
      if (ROUND_<ROUNDING> == ROUND_FLOOR)
        ix86_expand_floorceil (operands[0], operands[1], true);
      else if (ROUND_<ROUNDING> == ROUND_CEIL)
        ix86_expand_floorceil (operands[0], operands[1], false);
      else if (ROUND_<ROUNDING> == ROUND_TRUNC)
        ix86_expand_trunc (operands[0], operands[1]);
      else
        gcc_unreachable ();
    }
in:
(define_expand "<rounding_insn><mode>2"
But with -mavx, generated the vroundsd insn. Does it mean ROUNDEVEN
should have a condition in the else if, but comments above
ix86_expand* functions in i386-expand.c says that those are for SSE2
sequences?

Thanks,
--Tejas


On Mon, 17 Jun 2019 at 22:45, Joseph Myers <joseph@codesourcery.com> wrote:
>
> On Mon, 17 Jun 2019, Tejas Joshi wrote:
>
> > > existing ROUND_NO_EXC definition in GCC.  A new definition will need
> > > adding alongside ROUND_FLOOR, ROUND_CEIL and ROUND_TRUNC to correspond to
> > > rounding to nearest with ties to even, evaluating to 0.)
> >
> > So (ROUND_ROUNDEVEN   0x0) be declared for rounding towards nearest
> > even for rounding mode argument? But reference says that RC field
> > should end up as 00B for rounding ties to even? I am also much
>
> I think the code will be much clearer if it explicitly says
> ROUND_ROUNDEVEN | ROUND_NO_EXC, than if it hardcodes implicit knowledge
> that 0 is the value used for rounding to nearest with ties to even.
>
> --
> Joseph S. Myers
> joseph@codesourcery.com