[Bug middle-end/32279] New: Fold 1.0/sqrt(x/y) to sqrt(y/x)

[Bug middle-end/32279] New: Fold 1.0/sqrt(x/y) to sqrt(y/x)

[rguenth at gcc dot gnu dot org]

This may even work for -funsafe-math-optimizations only (we round differently).
One has to enumerate all interesting cases (mainly x == 0) and see if NaN/Inf
are properly preserved in all cases.


-- 
           Summary: Fold 1.0/sqrt(x/y) to sqrt(y/x)
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32279

[Bug middle-end/32279] Fold 1.0/sqrt(x/y) to sqrt(y/x)

[ubizjak at gmail dot com]

------- Comment #1 from ubizjak at gmail dot com  2007-06-11 06:36 -------
Patch at http://gcc.gnu.org/ml/gcc-patches/2007-06/msg00655.html

Patch was also checked with 0.0, __builtin_inf and __builtin_nan, and the
results were the same as for unpatched gcc for all combinations that were
thrown in.


-- 

ubizjak at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |ubizjak at gmail dot com
                   |dot org                     |
                URL|                            |http://gcc.gnu.org/ml/gcc-
                   |                            |patches/2007-
                   |                            |06/msg00655.html
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|0                           |1
           Keywords|                            |patch
   Last reconfirmed|0000-00-00 00:00:00         |2007-06-11 06:36:21
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32279

[Bug middle-end/32279] Fold 1.0/sqrt(x/y) to sqrt(y/x)

[uros at gcc dot gnu dot org]

------- Comment #2 from uros at gcc dot gnu dot org  2007-06-11 09:09 -------
Subject: Bug 32279

Author: uros
Date: Mon Jun 11 09:09:24 2007
New Revision: 125614

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=125614
Log:
        PR middle-end/32279
        * fold-const (fold_binary) [RDIV_EXPR]: Optimize a/sqrt(b/c)
        into a*sqrt(c/b) if flag_unsafe_math_optimizations is set.

testsuite/ChangeLog:

        PR middle-end/32279
        * gcc.dg/builtins-11.c: Also check folding of a/sqrt(b/c).


Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/fold-const.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.dg/builtins-11.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32279

[Bug middle-end/32279] Fold 1.0/sqrt(x/y) to sqrt(y/x)

[ubizjak at gmail dot com]

------- Comment #3 from ubizjak at gmail dot com  2007-06-11 09:11 -------
Fixed.


-- 

ubizjak at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32279