[Bug fortran/106579] New: ieee_signaling_nan problem in fortran on powerpc64

["seurer at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106579

            Bug ID: 106579
           Summary: ieee_signaling_nan problem in fortran on powerpc64
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: seurer at gcc dot gnu.org
  Target Milestone: ---

There is an issue with ieee_signaling_nan as used in fortran on powerpc64 when
--with-long-double-format=ieee is used.

Extracted from gfortran.dg/ieee/signaling_3.f90:

program test
  use, intrinsic :: iso_c_binding
  use, intrinsic :: ieee_arithmetic
  implicit none

  real(kind=c_long_double) :: z

  if (ieee_support_nan(z)) then
    z = ieee_value(z, ieee_signaling_nan)
    if (ieee_class(z) /= ieee_signaling_nan) stop 100
  end if

end program test

seurer@fowler:~/gcc/git/build/gcc-12-test$
/home/seurer/gcc/git/build/gcc-12-test/gcc/testsuite/gfortran/../../gfortran
-B/home/seurer/gcc/git/build/gcc-12-test/gcc/testsuite/gfortran/../../
-B/home/seurer/gcc/git/build/gcc-12-test/powerpc64le-unknown-linux-gnu/./libgfortran/
signaling_3a.f90 -fdiagnostics-plain-output -fdiagnostics-plain-output -O0
-pedantic-errors -fintrinsic-modules-path
/home/seurer/gcc/git/build/gcc-12-test/powerpc64le-unknown-linux-gnu/./libgfortran/
-fno-unsafe-math-optimizations -frounding-math -fsignaling-nans
-B/home/seurer/gcc/git/build/gcc-12-test/powerpc64le-unknown-linux-gnu/./libgfortran/.libs
-L/home/seurer/gcc/git/build/gcc-12-test/powerpc64le-unknown-linux-gnu/./libgfortran/.libs
-L/home/seurer/gcc/git/build/gcc-12-test/powerpc64le-unknown-linux-gnu/./libgfortran/.libs
-L/home/seurer/gcc/git/build/gcc-12-test/powerpc64le-unknown-linux-gnu/./libatomic/.libs
-B/home/seurer/gcc/git/build/gcc-12-test/powerpc64le-unknown-linux-gnu/./libquadmath/.libs
-L/home/seurer/gcc/git/build/gcc-12-test/powerpc64le-unknown-linux-gnu/./libquadmath/.libs
-L/home/seurer/gcc/git/build/gcc-12-test/powerpc64le-unknown-linux-gnu/./libquadmath/.libs
-lm -o ./signaling_3a.exe

seurer@fowler:~/gcc/git/build/gcc-12-test$ ./signaling_3a.exe 
STOP 100


This happens for both gcc 12 and 13 (trunk).

It occurs on powerpc64 LE with the compiler being tested configured with
--with-long-double-format=ieee on Fedora 36 which is the first powerpc64 distro
built with --with-long-double-format=ieee.  The distro compiler is gcc version
12.1.1 20220507 (Red Hat 12.1.1-1) (GCC).


Note the specific test case, signaling_3.f90, was added here but another test
case signaling_2.f90 fails the same way.

commit e89d0befe3ec3238fca6de2cb078eb403b8c7e99 (HEAD)
Author: Francois-Xavier Coudert <fxcoudert@gcc.gnu.org>
Date:   Mon Jan 17 12:46:48 2022 +0100

    Fortran: provide a fallback implementation of issignaling