[Bug libfortran/38199] missed optimization: I/O performance

["manfred99 at gmx dot ch" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38199

--- Comment #22 from Manfred Schwarb <manfred99 at gmx dot ch> 2013-02-15 10:20:46 UTC ---
Last month I had a private communication with Jerry, whether this bug
can be closed. I decided to add a summary to the bugzilla page:

The fix of Thomas is restricted to scalars and list-io. One could simply
replace buffer by buffer(1) in my test case 2 in comment #1 (using list-io):
!234567
      character buffer(1)*100000
      integer i,j

      DO j=1,9999
        write(buffer(1),'(i4)') j
        write(*,*) buffer(1)(1:4)
        read(buffer,*) i
        write(*,*) i
      ENDDO
      end

And we are again dog slow.
For formatted IO (comment #21), this patch does not help either.

Timings of the above test case:
gfortran4.3:     10.3s
gfortran4.7:     13.5s
gfortran4.8:     15.8s

as comparison, test case 2 of comment #1:
gfortran4.8:     0.26s


Timings for testcase in comment #21:
gfortran4.3:    2.7s
gfortran4.6:    2.7s
gfortran4.7:    4.7s  <---
gfortran4.8:    4.0s