[Bug libfortran/53148] New: [gcc/gfortran-4.7.0 Regression] Incorrect intrinsic function parsing on labeled statements when compiled w/optimization

[Bug libfortran/53148] New: [gcc/gfortran-4.7.0 Regression] Incorrect intrinsic function parsing on labeled statements when compiled w/optimization

[jpsinthemix at verizon dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53148

             Bug #: 53148
           Summary: [gcc/gfortran-4.7.0 Regression] Incorrect intrinsic
                    function parsing on labeled statements when compiled
                    w/optimization
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libfortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jpsinthemix@verizon.net


Created attachment 27256
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27256
Compilation and .s files for -O0 and -O2 optimizations

Hi,
There appears to be a gcc/gfortran-4.7.0 regression occurring for -O
optimizations greater than -O0 related to the parsing of labeled statements
containing expressions with repeated function calls. For example, a statement
like:

   10 x = dble(y)*dble(y)

will generate a compiler warning, similar to

label_opt_issue.f:38:0: warning: '__var_1' is used uninitialized in this
function [-Wuninitialized]

and at runtime, the expression dble(y)*dble(y) will always evaluate to 0,
regardless of the value of y.

Expected results are obtained when the code is compiled with default/no
optimization, but failure occurs when compiling with -O1 and above. There is
nothing special about the use of intrinsic DBLE here, the same behavior occurs
for other intrinsic functions (user-defined functions work as expected). In
addition, if a more complicated expression is used, for example,

   10 x = (1.d0 + exp(y)*exp(y))/z

then the same compilation warning occurs, and the value of x is evaluated as

      x = (1 + 0)/z = 1/z

that is, exp(y)*exp(y) evaluates to 0, regardless of y.


This issue is not present in gcc/gfortran-4.6.3. The following program
demonstrates the issue:

C label_opt_issue.f

      program main
          real x
          double precision xsq
          double precision test_func
          double precision work_around

          x = 5.

          xsq = test_func(x)
          write(*,*) "function   x: ", x, "    x*x: ", xsq

          call test_subr(x,xsq)
          write(*,*) "subroutine x: ", x, "    x*x: ", xsq

          xsq = work_around(x)
          write(*,*) "expected   x: ", x, "    x*x: ", xsq
          end program

      subroutine test_subr(x,xsq)
          real x
          double precision xsq
          intrinsic dble

          goto 10

   10     xsq = dble(x)*dble(x)
          return
          end subroutine

      double precision function test_func(x)
          real x
          intrinsic dble

          goto 10

   10     test_func = dble(x)*dble(x)
          return
          end function

      double precision function work_around(x)
          real x
          intrinsic dble

          goto 10

   10     continue
          work_around = dble(x)*dble(x)
          return
          end function

Demonstration code output:

With -O1 to -O3 optimization:

$ ./label_opt_issue
 function   x:    5.00000000         x*x:    0.0000000000000000
 subroutine x:    5.00000000         x*x:    0.0000000000000000
 expected   x:    5.00000000         x*x:    25.000000000000000

With default optimization:

$ ./label_opt_issue
 function   x:    5.00000000         x*x:    25.000000000000000
 subroutine x:    5.00000000         x*x:    25.000000000000000
 expected   x:    5.00000000         x*x:    25.000000000000000


I have attached the label_opt_issue.f compilation logs and temp *.s files for
for two cases: default optimization and -O2 optimization. 

I came across this issue building and testing SCIPY; one test failed which
really should not have, and that lead me to a fortran routine using DBLE in the
manner above which always evaluated to 0.

System info:

=== gcc/gfortran version/options/system type:
$ gfortran -v
Using built-in specs.
COLLECT_GCC=gfortran
COLLECT_LTO_WRAPPER=/usr/lib/gcc/i686-pc-linux-gnu/4.7.0/lto-wrapper
Target: i686-pc-linux-gnu
Configured with: /home/bld/gcc-4.7.0-jps_src/gcc-4.7.0/configure --prefix=/usr
--libexecdir=/usr/lib --with-gmp=/usr --with-mpfr=/usr --with-system-zlib
--enable-shared --enable-checking=release --enable-threads=posix
--enable-__cxa_atexit --enable-clocale=gnu --disable-bootstrap
--enable-languages=c,c++,fortran --infodir=/usr/share/info
--mandir=/usr/share/man
Thread model: posix
gcc version 4.7.0 (GCC)

system: Linux b-movie 3.3.3 #1 Sun Apr 22 21:11:23 EDT 2012 i686 GNU/Linux
glibc:  2.15

thanks for your time,
John

[Bug fortran/53148] [4.7/4.8 Regression] Incorrect intrinsic function parsing on labeled statements when compiled w/ -ffrontend-optimize

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53148

Tobias Burnus <burnus at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
           Keywords|                            |wrong-code
   Last reconfirmed|                            |2012-04-28
          Component|libfortran                  |fortran
                 CC|                            |burnus at gcc dot gnu.org,
                   |                            |tkoenig at gcc dot gnu.org
     Ever Confirmed|0                           |1
            Summary|[gcc/gfortran-4.7.0         |[4.7/4.8 Regression]
                   |Regression] Incorrect       |Incorrect intrinsic
                   |intrinsic function parsing  |function parsing on labeled
                   |on labeled statements when  |statements when compiled w/
                   |compiled w/optimization     |-ffrontend-optimize
   Target Milestone|---                         |4.7.1

--- Comment #1 from Tobias Burnus <burnus at gcc dot gnu.org> 2012-04-28 20:41:18 UTC ---
Workaround: -fno-frontend-optimize

[Bug fortran/53148] [4.7/4.8 Regression] Incorrect intrinsic function parsing on labeled statements when compiled w/ -ffrontend-optimize

[tkoenig at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53148

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |tkoenig at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #2 from Thomas Koenig <tkoenig at gcc dot gnu.org> 2012-04-29 07:03:25 UTC ---
I have a patch.

[Bug fortran/53148] [4.7/4.8 Regression] Incorrect intrinsic function parsing on labeled statements when compiled w/ -ffrontend-optimize

[tkoenig at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53148

--- Comment #3 from Thomas Koenig <tkoenig at gcc dot gnu.org> 2012-04-29 07:12:10 UTC ---
Author: tkoenig
Date: Sun Apr 29 07:12:03 2012
New Revision: 186942

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=186942
Log:
2012-04-29  Thomas Koenig  <tkoenig@gcc.gnu.org>

    PR fortran/53148
    * frontend-passes.c (create_var):  If the statement has a label,
    put the label around the block.

2012-04-29  Thomas Koenig  <tkoenig@gcc.gnu.org>

    PR fortran/53148
    * gfortran.dg/function_optimize_12.f90:  New test.


Added:
    trunk/gcc/testsuite/gfortran.dg/function_optimize_12.f90
Modified:
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/frontend-passes.c
    trunk/gcc/testsuite/ChangeLog

[Bug fortran/53148] [4.7 Regression] Incorrect intrinsic function parsing on labeled statements when compiled w/ -ffrontend-optimize

[tkoenig at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53148

--- Comment #4 from Thomas Koenig <tkoenig at gcc dot gnu.org> 2012-04-30 19:31:24 UTC ---
Author: tkoenig
Date: Mon Apr 30 19:31:13 2012
New Revision: 186999

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=186999
Log:
2012-04-30  Thomas Koenig  <tkoenig@gcc.gnu.org>

    PR fortran/53148
    Backport from trunk
    * frontend-passes.c (create_var):  If the statement has a label,
    put the label around the block.

2012-04-30  Thomas Koenig  <tkoenig@gcc.gnu.org>

    PR fortran/53148
    Backport from trunk
    * gfortran.dg/function_optimize_12.f90:  New test.


Added:
    branches/gcc-4_7-branch/gcc/testsuite/gfortran.dg/function_optimize_12.f90
Modified:
    branches/gcc-4_7-branch/gcc/fortran/ChangeLog
    branches/gcc-4_7-branch/gcc/fortran/frontend-passes.c
    branches/gcc-4_7-branch/gcc/testsuite/ChangeLog

[Bug fortran/53148] [4.7 Regression] Incorrect intrinsic function parsing on labeled statements when compiled w/ -ffrontend-optimize

[tkoenig at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53148

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

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

--- Comment #5 from Thomas Koenig <tkoenig at gcc dot gnu.org> 2012-04-30 19:34:23 UTC ---
Fixed on trunk and 4.7.

Closing.

Thanks a lot for the bug report!

[Bug fortran/53148] [4.7 Regression] Incorrect intrinsic function parsing on labeled statements when compiled w/ -ffrontend-optimize

[jpsinthemix at verizon dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53148

--- Comment #6 from John Stanley <jpsinthemix at verizon dot net> 2012-04-30 23:47:03 UTC ---
(In reply to comment #5)
> Fixed on trunk and 4.7.
> 
> Closing.
> 
> Thanks a lot for the bug report!

I rebuilt gcc with cherry-picked patches and all look good. Really appreciate
the super-fast response and fix.

[Bug fortran/53148] [4.7 Regression] Incorrect intrinsic function parsing on labeled statements when compiled w/ -ffrontend-optimize

[jsm28 at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53148

--- Comment #7 from Joseph S. Myers <jsm28 at gcc dot gnu.org> 2012-05-21 14:42:40 UTC ---
Author: jsm28
Date: Mon May 21 14:42:26 2012
New Revision: 187718

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=187718
Log:
    PR c/53148
    * c-typeck.c (build_conditional_expr): Remove C_MAYBE_CONST_EXPR
    from folded operands before wrapping another around the
    conditional expression.

testsuite:
    * gcc.c-torture/compile/pr53418-1.c,
    gcc.c-torture/compile/pr53418-2.c: New tests.

Added:
    trunk/gcc/testsuite/gcc.c-torture/compile/pr53418-1.c
    trunk/gcc/testsuite/gcc.c-torture/compile/pr53418-2.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/c-typeck.c
    trunk/gcc/testsuite/ChangeLog