[Bug middle-end/32503] __builtin_powi - optimize for other exponents besides 2 and 0.5

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=32503

--- Comment #4 from Eric Gallager  ---
(In reply to Richard Biener from comment #2)
> Confirmed.  I had done tree-level expansion of powi into add/mul sequences at
> one time.  But this had been rejected for some reason I cannot remember
> right now.

Do you at least remember when that time was, so we can know where to go looking
in the archives?

[Bug middle-end/32503] __builtin_powi - optimize for other exponents besides 2 and 0.5

[jb at gcc dot gnu dot org]

--- Comment #3 from jb at gcc dot gnu dot org  2007-06-26 19:00 ---
(In reply to comment #2)
> Confirmed.  I had done tree-level expansion of powi into add/mul sequences at
> one time.  But this had been rejected for some reason I cannot remember right
> now.

The middle-end is able to expand builtin_powi for constant integers. The
problem with vectorization is that the vectorizer runs before the pow(i)
expansion, and the vectorizer is only aware of exponenets 2 and 0.5. Expanding
in the FE works around that problem. In fact, it seems the FE expander is
lifted from the ME.


-- 

jb at gcc dot gnu dot org changed:

   What|Removed |Added

 CC||jb at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32503

[Bug middle-end/32503] __builtin_powi - optimize for other exponents besides 2 and 0.5

[rguenth at gcc dot gnu dot org]

--- Comment #2 from rguenth at gcc dot gnu dot org  2007-06-26 10:47 ---
Confirmed.  I had done tree-level expansion of powi into add/mul sequences at
one time.  But this had been rejected for some reason I cannot remember right
now.


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rguenth at gcc dot gnu dot org changed:

   What|Removed |Added

 CC||rguenth at gcc dot gnu dot
   ||org
 Status|UNCONFIRMED |NEW
 Ever Confirmed|0   |1
   Last reconfirmed|-00-00 00:00:00 |2007-06-26 10:47:05
   date||


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32503

[Bug middle-end/32503] __builtin_powi - optimize for other exponents besides 2 and 0.5

[burnus at gcc dot gnu dot org]

--- Comment #1 from burnus at gcc dot gnu dot org  2007-06-25 19:56 ---
> Additionally: It would be great if there would be a variant for long integers
> (8 byte integers) and long long (16 byte integers) as PR32239 could only use
> __builtin_powi for int4 and not for int8 or int16.

Actually, gfortran uses also:  pow(integer,integer) and pow(complex,integer),
which could also profit from a middle/back-end support. (integer: 4, 8, 16
bytes; complex: single, double, long double precision).


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32503