Re: [PATCH 1/6] Use IFN_SQRT in tree-vect-patterns.c

[Richard Biener <richard dot guenther at gmail dot com>]

On Tue, Nov 10, 2015 at 11:57 AM, Richard Sandiford
<richard.sandiford@arm.com> wrote:
> Richard Biener <richard.guenther@gmail.com> writes:
>> On Mon, Nov 9, 2015 at 5:21 PM, Richard Sandiford
>> <richard.sandiford@arm.com> wrote:
>>> In practice all targets that can vectorise sqrt define the appropriate
>>> sqrt<mode>2 optab.  The only case where this isn't immediately obvious
>>> is the libmass support in rs6000.c, but Mike Meissner said that it shouldn't
>>> be exercised for sqrt.
>>>
>>> This patch therefore uses the internal function interface instead of
>>> going via the target hook.
>>>
>>>
>>> gcc/
>>>         * tree-vect-patterns.c: Include internal-fn.h.
>>>         (vect_recog_pow_pattern): Use IFN_SQRT instead of BUILT_IN_SQRT*.
>>>
>>> diff --git a/gcc/tree-vect-patterns.c b/gcc/tree-vect-patterns.c
>>> index bab9a4f..a803e8c 100644
>>> --- a/gcc/tree-vect-patterns.c
>>> +++ b/gcc/tree-vect-patterns.c
>>> @@ -39,6 +39,7 @@ along with GCC; see the file COPYING3.  If not see
>>>  #include "tree-vectorizer.h"
>>>  #include "dumpfile.h"
>>>  #include "builtins.h"
>>> +#include "internal-fn.h"
>>>  #include "case-cfn-macros.h"
>>>
>>>  /* Pattern recognition functions  */
>>> @@ -1052,18 +1053,13 @@ vect_recog_pow_pattern (vec<gimple *> *stmts, tree *type_in,
>>>    if (TREE_CODE (exp) == REAL_CST
>>>        && real_equal (&TREE_REAL_CST (exp), &dconsthalf))
>>>      {
>>> -      tree newfn = mathfn_built_in (TREE_TYPE (base), BUILT_IN_SQRT);
>>>        *type_in = get_vectype_for_scalar_type (TREE_TYPE (base));
>>> -      if (*type_in)
>>> +      if (*type_in && direct_internal_fn_supported_p (IFN_SQRT, *type_in))
>>>         {
>>> -         gcall *stmt = gimple_build_call (newfn, 1, base);
>>> -         if (vectorizable_function (stmt, *type_in, *type_in)
>>> -             != NULL_TREE)
>>> -           {
>>> -             var = vect_recog_temp_ssa_var (TREE_TYPE (base), stmt);
>>> -             gimple_call_set_lhs (stmt, var);
>>> -             return stmt;
>>> -           }
>>> +         gcall *stmt = gimple_build_call_internal (IFN_SQRT, 1, base);
>>> +         var = vect_recog_temp_ssa_var (TREE_TYPE (base), stmt);
>>> +         gimple_call_set_lhs (stmt, var);
>>> +         return stmt;
>>
>> Looks ok but I wonder if this is dead code with
>>
>> (for pows (POW)
>>      sqrts (SQRT)
>>      cbrts (CBRT)
>>  (simplify
>>   (pows @0 REAL_CST@1)
>>   (with {
>>     const REAL_VALUE_TYPE *value = TREE_REAL_CST_PTR (@1);
>>     REAL_VALUE_TYPE tmp;
>>    }
>>    (switch
>> ...
>>     /* pow(x,0.5) -> sqrt(x).  */
>>     (if (flag_unsafe_math_optimizations
>>          && canonicalize_math_p ()
>>          && real_equal (value, &dconsthalf))
>>      (sqrts @0))
>
> Yeah, I wondered that too, although I think it's more likely to be dead
> because of sincos.  In the end it just seemed like a rabiit hole too far
> though.

Indeed.  sincos should also fix the pow(x, 2.) case handled.

Richard.

>> Anyway, patch is ok.
>
> Thanks,
> Richard
>