[Bug fortran/109511] New: incorrectly rejects set_exponent with constant negative exponent

[Bug fortran/109511] New: incorrectly rejects set_exponent with constant negative exponent

[sebastien at debian dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109511

            Bug ID: 109511
           Summary: incorrectly rejects set_exponent with constant
                    negative exponent
           Product: gcc
           Version: 12.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sebastien at debian dot org
  Target Milestone: ---

The following program fails to compile:

program exponent
  print *, set_exponent(1., -1)
end program exponent

With the following error message:

exponent.f08:2:24:

    2 |   print *, set_exponent(1., -1)
      |                        1
Error: Result of SET_EXPONENT overflows its kind at (1)

But as I understand it, this is a valid program.

Note that the problem does not occur if the exponent is positive. It also does
not occur if the exponent is variable (even with a negative value). So it looks
like the static analyzer is overly restrictive.

[Bug fortran/109511] incorrectly rejects set_exponent with constant negative exponent

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109511

anlauf at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
           Keywords|                            |wrong-code
                 CC|                            |anlauf at gcc dot gnu.org
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-04-14

--- Comment #1 from anlauf at gcc dot gnu.org ---
Confirmed.

The simplification seems to use the old mpfr_mul_2exp which takes an
unsigned exponent.  There is the newer mpfr_mul_2si which accepts a signed
exponent.

[Bug fortran/109511] incorrectly rejects set_exponent with constant negative exponent

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109511

--- Comment #2 from anlauf at gcc dot gnu.org ---
It's even worse, as simplification for arguments X below one gives wrong
results:

set_exponent(0.75, 3)

gives 3.00000000, while the runtime version correctly prints 6.000000

All gfortran versions seem to be affected.

[Bug fortran/109511] incorrectly rejects set_exponent with constant negative exponent

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109511

--- Comment #3 from anlauf at gcc dot gnu.org ---
Created attachment 54860
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54860&action=edit
Patch

Patch I am testing.

[Bug fortran/109511] incorrectly rejects set_exponent with constant negative exponent

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109511

anlauf at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |anlauf at gcc dot gnu.org
             Status|NEW                         |ASSIGNED

--- Comment #4 from anlauf at gcc dot gnu.org ---
Submitted, with an additional fix for negative X:

https://gcc.gnu.org/pipermail/fortran/2023-April/059182.html

[Bug fortran/109511] incorrectly rejects set_exponent with constant negative exponent

[sebastien at debian dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109511

--- Comment #5 from Sébastien Villemot <sebastien at debian dot org> ---
Thanks for your work on this issue!

[Bug fortran/109511] incorrectly rejects set_exponent with constant negative exponent

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109511

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Harald Anlauf <anlauf@gcc.gnu.org>:

https://gcc.gnu.org/g:fa4cb42870df60deb8888dbd51e2ddc6d6ab9e6a

commit r13-7188-gfa4cb42870df60deb8888dbd51e2ddc6d6ab9e6a
Author: Harald Anlauf <anlauf@gmx.de>
Date:   Fri Apr 14 20:45:19 2023 +0200

    Fortran: fix compile-time simplification of SET_EXPONENT [PR109511]

    gcc/fortran/ChangeLog:

            PR fortran/109511
            * simplify.cc (gfc_simplify_set_exponent): Fix implementation of
            compile-time simplification of intrinsic SET_EXPONENT for argument
            X < 1 and for I < 0.

    gcc/testsuite/ChangeLog:

            PR fortran/109511
            * gfortran.dg/set_exponent_1.f90: New test.

[Bug fortran/109511] incorrectly rejects set_exponent with constant negative exponent

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109511

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Harald Anlauf
<anlauf@gcc.gnu.org>:

https://gcc.gnu.org/g:64efeac03cb9fa2603bb6628712f3a2541aef1cb

commit r12-9402-g64efeac03cb9fa2603bb6628712f3a2541aef1cb
Author: Harald Anlauf <anlauf@gmx.de>
Date:   Fri Apr 14 20:45:19 2023 +0200

    Fortran: fix compile-time simplification of SET_EXPONENT [PR109511]

    gcc/fortran/ChangeLog:

            PR fortran/109511
            * simplify.cc (gfc_simplify_set_exponent): Fix implementation of
            compile-time simplification of intrinsic SET_EXPONENT for argument
            X < 1 and for I < 0.

    gcc/testsuite/ChangeLog:

            PR fortran/109511
            * gfortran.dg/set_exponent_1.f90: New test.

    (cherry picked from commit fa4cb42870df60deb8888dbd51e2ddc6d6ab9e6a)

[Bug fortran/109511] incorrectly rejects set_exponent with constant negative exponent

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109511

--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Harald Anlauf
<anlauf@gcc.gnu.org>:

https://gcc.gnu.org/g:dfcdb457c462b9e35eb54d3b758221a119067e24

commit r11-10625-gdfcdb457c462b9e35eb54d3b758221a119067e24
Author: Harald Anlauf <anlauf@gmx.de>
Date:   Fri Apr 14 20:45:19 2023 +0200

    Fortran: fix compile-time simplification of SET_EXPONENT [PR109511]

    gcc/fortran/ChangeLog:

            PR fortran/109511
            * simplify.c (gfc_simplify_set_exponent): Fix implementation of
            compile-time simplification of intrinsic SET_EXPONENT for argument
            X < 1 and for I < 0.

    gcc/testsuite/ChangeLog:

            PR fortran/109511
            * gfortran.dg/set_exponent_1.f90: New test.

    (cherry picked from commit fa4cb42870df60deb8888dbd51e2ddc6d6ab9e6a)

[Bug fortran/109511] incorrectly rejects set_exponent with constant negative exponent

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109511

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Harald Anlauf
<anlauf@gcc.gnu.org>:

https://gcc.gnu.org/g:dd2cd1e70509aaeb3db3e7b322d8357bac817632

commit r10-11289-gdd2cd1e70509aaeb3db3e7b322d8357bac817632
Author: Harald Anlauf <anlauf@gmx.de>
Date:   Fri Apr 14 20:45:19 2023 +0200

    Fortran: fix compile-time simplification of SET_EXPONENT [PR109511]

    gcc/fortran/ChangeLog:

            PR fortran/109511
            * simplify.c (gfc_simplify_set_exponent): Fix implementation of
            compile-time simplification of intrinsic SET_EXPONENT for argument
            X < 1 and for I < 0.

    gcc/testsuite/ChangeLog:

            PR fortran/109511
            * gfortran.dg/set_exponent_1.f90: New test.

    (cherry picked from commit fa4cb42870df60deb8888dbd51e2ddc6d6ab9e6a)

[Bug fortran/109511] incorrectly rejects set_exponent with constant negative exponent

[anlauf at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109511

anlauf at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
   Target Milestone|---                         |10.5
         Resolution|---                         |FIXED

--- Comment #10 from anlauf at gcc dot gnu.org ---
Fixed on mainline for gcc-13, and on all open branches.  Closing.

Thanks for the report!