[patch, fortran] Fix wrong-code regression with netcdf and SPEC due to argument repacking

[Thomas Koenig]

Hello world,

the attached patch fixes the wrong-code regression due to the
inline argument repacking patch, r271377.

What had gone wrong?  gfortran used to pack and  unpack arrays
unconditionally passed to old-style assumed size or .  For code like

module t2
   implicit none
contains
   subroutine foo(a)
     real, dimension(*) :: a
   end subroutine foo
end module t2

module t1
   use t2
   implicit none
contains
   subroutine bar(a)
     real, dimension(:) :: a
     call foo(a)
   end subroutine bar
end module t1

program main
   use t1
   call bar([1.0, 2.0])
end program main

this meant that an (always contiguous) array constructor was
passed down to an assumed shape array, which then passed it
on to an assumed size, explicit shape or adjustable array.
Packing was not problematic (apart from performance), but
unpacking tried to write into the array constructor.

So, this patch inserts a run-time check for contiguous arrays
and does not do packing/unpacking in that case.

Thanks to Toon and Martin for finding an open test case which
actually failed, and for help with debugging.

(Always repacking also likely impacted performance when it didn't
lead to wrong code, we will have to see how performance is with
this version).

OK for trunk?

Regards

	Thomas

2019-05-29  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/90539
	* gfortran.h (gfc_has_dimen_vector_ref): Add prototype.
	* trans.h (gfc_conv_subref_array_arg): Add argument check_contiguous.
	(gfc_conv_is_contiguous_expr): Add prototype.
	* frontend-passes.c (has_dimen_vector_ref): Remove prototype,
	rename to
	(gfc_has_dimen_vector_ref): New function name.
	(matmul_temp_args): Use gfc_has_dimen_vector_ref.
	(inline_matmul_assign): Likewise.
	* trans-array.c (gfc_conv_array_parameter): Also check for absence
	of a vector subscript before calling gfc_conv_subref_array_arg.
	Pass additional argument to gfc_conv_subref_array_arg.
	* trans-expr.c (gfc_conv_subref_array_arg): Add argument
	check_contiguous. If that is true, check if the argument
	is contiguous and do not repack in that case.
	* trans-intrinsic.c (gfc_conv_intrinsic_is_contiguous): Split
	away most of the work into, and call
	(gfc_conv_intrinsic_is_coniguous_expr): New function.

2019-05-29  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/90539
	* gfortran.dg/internal_pack_21.f90: Adjust scan patterns.
	* gfortran.dg/internal_pack_22.f90: New test.
	* gfortran.dg/internal_pack_23.f90: New test.
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