[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=gccview=revrev=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.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 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=gccview=revrev=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


-- 


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 #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))

[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))

[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


-- 


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=19706action=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).


-- 

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|-00-00 00:00:00 |2010-01-12 09:08:00
   date||


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