[Bug fortran/52243] New: Avoid reallocation for: array1 = array1 / scalar for performance

[Bug fortran/52243] New: Avoid reallocation for: array1 = array1 / scalar for performance

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52243

             Bug #: 52243
           Summary: Avoid reallocation for:  array1 = array1 / scalar  for
                    performance
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: burnus@gcc.gnu.org
                CC: pault@gcc.gnu.org


Some testing with -Wrealloc-lhs (PR 52196) showed that it is rather common to
encounter the following code.

gfortran inserts a reallocation check - but as the same array is on the LHS and
on the RHS, the LHS must be allocated with the correct shape is the same.
Hence, no reallocation check should be inserted (missed optimization):

        nablamat=nablamat*hescale
         kpoints=kpoints/scale                                
      hreal=hreal/cmplx(real(nkpts),0.0)

    y2 = y2 + y

      ylm = conjg( ylm )
      phasusbmat=conjg(phasusbmat)

      cc = det * transpose(cc)

[Bug fortran/52243] Avoid reallocation for: array1 = array1 / scalar for performance

[tkoenig at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52243

Thomas Koenig <tkoenig at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2013-08-28
           Assignee|unassigned at gcc dot gnu.org      |tkoenig at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
I have a patch.

[Bug fortran/52243] Avoid reallocation for: array1 = array1 / scalar for performance

[tkoenig at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52243

--- Comment #2 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
Author: tkoenig
Date: Thu Aug 29 11:44:41 2013
New Revision: 202070

URL: http://gcc.gnu.org/viewcvs?rev=202070&root=gcc&view=rev
Log:
2013-08-29  Thomas Koenig  <tkoenig@gcc.gnu.org>

    PR fortran/52243
    * trans-expr.c (is_runtime_conformable):  New function.
    * gfc_trans_assignment_1:  Use it.

2013-08-29  Thomas Koenig  <tkoenig@gcc.gnu.org>

    PR fortran/52243
    * gfortran.dg/realloc_on_assign_14.f90:  Remove warning made
    obsolete by patch.
    * gfortran.dg/realloc_on_assign_19.f90:  New test.


Added:
    trunk/gcc/testsuite/gfortran.dg/realloc_on_assign_19.f90
Modified:
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/trans-expr.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gfortran.dg/realloc_on_assign_14.f90

[Bug fortran/52243] Avoid reallocation for: array1 = array1 / scalar for performance

[tkoenig at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52243

--- Comment #3 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
Fixed on trunk, closing.

[Bug fortran/52243] Avoid reallocation for: array1 = array1 / scalar for performance

[tkoenig at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52243

Thomas Koenig <tkoenig at gcc dot gnu.org> changed:

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

--- Comment #4 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
Really closing :-)