Use combined_fn in tree-vrp.c

[Richard Biener]

On Fri, Nov 13, 2015 at 12:27 PM, Richard Sandiford
<richard.sandiford@arm.com> wrote:
> Richard Biener <richard.guenther@gmail.com> writes:
>> On Tue, Nov 10, 2015 at 1:09 AM, Bernd Schmidt <bschmidt@redhat.com> wrote:
>>> On 11/07/2015 01:46 PM, Richard Sandiford wrote:
>>>>
>>>> @@ -3814,8 +3817,8 @@ extract_range_basic (value_range *vr, gimple *stmt)
>>>>           break;
>>>>           /* Both __builtin_ffs* and __builtin_popcount return
>>>>              [0, prec].  */
>>>> -       CASE_INT_FN (BUILT_IN_FFS):
>>>> -       CASE_INT_FN (BUILT_IN_POPCOUNT):
>>>> +       CASE_CFN_FFS:
>>>> +       CASE_CFN_POPCOUNT:
>>>>           arg = gimple_call_arg (stmt, 0);
>>>>           prec = TYPE_PRECISION (TREE_TYPE (arg));
>>>>           mini = 0;
>>>
>>>
>>> So let me see if I understood this. From what we discussed the purpose of
>>> these new internal functions is that they can have vector types. If so,
>>> isn't this code (here and elsewhere) which expects integers potentially
>>> going to be confused?
>>
>> We indeed need to add additional checks to most users of CASE_CFN_* to cover
>> the bigger freedom that exists with respect to types.
>
> The code above is OK because it's only handling integral types.
> A vector popcount or vector ffs must return a vector result.
>
>> Richard, please audit all the cases you change for that.
>
> I had another look and the only problematical uses I could see are the
> match.pd ones.  E.g.:
>
>  /* Optimize logN(func()) for various exponential functions.  We
>     want to determine the value "x" and the power "exponent" in
>     order to transform logN(x**exponent) into exponent*logN(x).  */
>  (for logs (LOG  LOG   LOG   LOG2 LOG2  LOG2  LOG10 LOG10)
>       exps (EXP2 EXP10 POW10 EXP  EXP10 POW10 EXP   EXP2)
>   (simplify
>    (logs (exps @0))
>    (with {
>      tree x;
>      switch (exps)
>        {
>        CASE_CFN_EXP:
>          /* Prepare to do logN(exp(exponent)) -> exponent*logN(e).  */
>          x = build_real_truncate (type, dconst_e ());
>          break;
>        CASE_CFN_EXP2:
>          /* Prepare to do logN(exp2(exponent)) -> exponent*logN(2).  */
>          x = build_real (type, dconst2);
>          break;
>        CASE_CFN_EXP10:
>        CASE_CFN_POW10:
>          /* Prepare to do logN(exp10(exponent)) -> exponent*logN(10).  */
>          {
>            REAL_VALUE_TYPE dconst10;
>            real_from_integer (&dconst10, VOIDmode, 10, SIGNED);
>            x = build_real (type, dconst10);
>          }
>          break;
>        default:
>          gcc_unreachable ();
>        }
>      }
>     (mult (logs { x; }) @0))))
>
> Here we could either add a SCALAR_FLOAT_TYPE_P check or extend
> build_real to handle vector types.  Which do you think would be best?

I don't like extending build_real.  For now add a SCALAR_FLOAT_TYPE_P.

Or maybe extend build_real ...

Well.  Go with SCALAR_FLOAT_TYPE_P.

Thanks,
Richard.

>
> Thanks,
> Richard
>