[Bug fortran/107874] merge not using all its arguments

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107874

kargl at gcc dot gnu.org changed:

           What    |Removed                     |Added
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                 CC|                            |kargl at gcc dot gnu.org

--- Comment #2 from kargl at gcc dot gnu.org ---
John thanks for posting the bug.

Harald, you are likely right the patch can be moved down.  I'll programmed up
the example from the Fortran 2018 standard, which works as expected.  So, there
is definitely something about a scalar mask choosing the actual argument before
both are evaluated.

   program foo
   call bah
   contains
      subroutine bah
         logical, parameter :: t = .true., f = .false.
         logical, parameter ::  mask(2,3)= reshape([t, f, f, f, t, t], [2,3])
         integer tsrc(2,3), fsrc(2,3), res(2,3)
         !
         ! Direct reference to merge
         !
         tsrc = reshape([1, 2, 6, 4, 5, 6], [2,3])
         fsrc = reshape([0, 7, 3, 4, 2, 8], [2,3])
         res = 42
         res = merge(tsrc, fsrc, mask)

         write(*,'(*(I0,1X))') res(1,:)  ! Should be 1 3 5
         write(*,'(*(I0,1X))') res(2,:)  ! Should be 7 4 6
         write(*,*)
         !
         ! Load matrices via a function.
         !
         res = 0 ! Clear
         res = merge(load('t'), load('f'), mask) ! Clear
         write(*,'(*(I0,1X))') res(1,:)  ! Should be 1 3 5
         write(*,'(*(I0,1X))') res(2,:)  ! Should be 7 4 6    
      end subroutine bah
      function load(c) result(r)
         integer r(2,3)
         character, intent(in) :: c
         if (c == 't') then
            r = reshape([1, 2, 6, 4, 5, 6], [2,3])
            print *, 'loaded t'
         else if (c == 'f') then
            r = reshape([0, 7, 3, 4, 2, 8], [2,3])
            print *, 'loaded f'
         else
            stop 'whoops'
         end if
      end function load
end program foo