[Bug middle-end/42694] Compiler could optimize pow (x, 0.75) into sqrt (x) * sqrt (sqrt (x))

[Bug middle-end/42694] Compiler could optimize pow (x, 0.75) into sqrt (x) * sqrt (sqrt (x))

[meissner at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42694

--- Comment #8 from Michael Meissner <meissner at gcc dot gnu.org> 2010-12-07 17:42:04 UTC ---
Created attachment 22675
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22675
Add check for sqrt optab being present before doing some optimizations

[Bug middle-end/42694] Compiler could optimize pow (x, 0.75) into sqrt (x) * sqrt (sqrt (x))

[meissner at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42694

--- Comment #9 from Michael Meissner <meissner at gcc dot gnu.org> 2010-12-08 16:34:26 UTC ---
Author: meissner
Date: Wed Dec  8 16:34:20 2010
New Revision: 167594

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=167594
Log:
PR 42694: add checks to make sure sqrt is supported

Added:
    trunk/gcc/testsuite/gcc.target/powerpc/ppc-pow.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/builtins.c
    trunk/gcc/testsuite/ChangeLog

[Bug middle-end/42694] Compiler could optimize pow (x, 0.75) into sqrt (x) * sqrt (sqrt (x))

[meissner at gcc dot gnu dot org]

------- Comment #7 from meissner at gcc dot gnu dot org  2010-04-14 15:03 -------
Fixed with subversion id 158346.


-- 

meissner at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42694

[Bug middle-end/42694] Compiler could optimize pow (x, 0.75) into sqrt (x) * sqrt (sqrt (x))

[meissner at gcc dot gnu dot org]

------- Comment #6 from meissner at gcc dot gnu dot org  2010-04-14 15:02 -------
Subject: Bug 42694

Author: meissner
Date: Wed Apr 14 15:01:40 2010
New Revision: 158346

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=158346
Log:
PR 42694: Optimize pow (x, 0.25), pow (x, 0.75), pow (x, 1./6.)

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/builtins.c


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42694

[Bug middle-end/42694] Compiler could optimize pow (x, 0.75) into sqrt (x) * sqrt (sqrt (x))

[paolo dot carlini at oracle dot com]

------- Comment #5 from paolo dot carlini at oracle dot com  2010-01-26 10:03 -------
With my "user of the compiler" hat, I must say that I was also put off by the 3
new switches... fwiw


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42694

[Bug middle-end/42694] Compiler could optimize pow (x, 0.75) into sqrt (x) * sqrt (sqrt (x))

[rguenth at gcc dot gnu dot org]

------- Comment #4 from rguenth at gcc dot gnu dot org  2010-01-26 09:57 -------
Ugh, I don't like more switches.  Instead I would say that using two sqrt
calls instead of one pow call is always profitable if not optimizing for size
and the target has an optab for sqrt.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42694

[Bug middle-end/42694] Compiler could optimize pow (x, 0.75) into sqrt (x) * sqrt (sqrt (x))

[meissner at gcc dot gnu dot org]

------- Comment #3 from meissner at gcc dot gnu dot org  2010-01-26 00:40 -------
Created an attachment (id=19706)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=19706&action=view)
Proposed patch to fix the problem

Patch to add 3 new switches to tune whether to use a combination of sqrt/cbrt
to replace pow.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42694

[Bug middle-end/42694] Compiler could optimize pow (x, 0.75) into sqrt (x) * sqrt (sqrt (x))

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2010-01-12 09:08 -------
Confirmed and easy to add in the pow expander (expand_builtin_pow).


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rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rguenth at gcc dot gnu dot
                   |                            |org
           Severity|normal                      |enhancement
             Status|UNCONFIRMED                 |NEW
          Component|rtl-optimization            |middle-end
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2010-01-12 09:08:00
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42694