dwarf2out: For ppc64le IEEE quad long double, emit DW_TAG_typedef to _Float128 [PR104194]

dwarf2out: For ppc64le IEEE quad long double, emit DW_TAG_typedef to _Float128 [PR104194]

On Mon, Jan 24, 2022 at 11:26:27PM +0100, Jakub Jelinek via Gcc-patches wrote:
> Yet another short term solution might be not use DW_TAG_base_type
> for the IEEE quad long double, but instead pretend it is a DW_TAG_typedef
> with DW_AT_name "long double" to __float128 DW_TAG_base_type.
> I bet gdb would even handle it without any changes, but of course, it would
> be larger than the other proposed changes.

Here it is implemented.

Testcases I've played with are e.g.:
__ibm128 a;
long double b;
_Complex long double c;

static __attribute__((noinline)) int
foo (long double d)
{
  long double e = d + 1.0L;
  return 0;
}

int
main ()
{
  a = 1.0;
  b = 2.0;
  c = 5.0 + 6.0i;
  return foo (7.0L);
}
and
  real(kind=16) :: a
  complex(kind=16) :: b
  a = 1.0
  b = 2.0
end

Printing the values of the variables works well,
p &b or p &c shows pointer to the correct type, just
ptype b or ptype c prints _Float128 instead of
long double or complex _Float128 instead of complex long double.
Even worse in fortran where obviously _Float128 or
complex _Float128 aren't valid types, but as GDB knows them by name,
it is just ptype that is weird.

2022-01-26  Jakub Jelinek  <jakub@redhat.com>

	PR debug/104194
	* dwarf2out.cc (long_double_as_float128): New function.
	(modified_type_die): For powerpc64le IEEE 754 quad long double
	and complex long double emit those as DW_TAG_typedef to
	_Float128 or complex _Float128 base type.