Regression for i686 gdb.dwarf2/pieces-optimized-out.exp

Regression for i686 gdb.dwarf2/pieces-optimized-out.exp

Git 9a0dc9e3 regressed gdb.dwarf2/pieces-optimized-out.exp, visible on
i686 (the test doesn't run on x86_64):

 (gdb) p s
 -$1 = {a = 5, b = <optimized out>, c = <optimized out>, d = <optimized out>}
 +$1 = {a = 5, b = <optimized out>, c = 0, d = 0}
 -(gdb) PASS: gdb.dwarf2/pieces-optimized-out.exp: print s
 +(gdb) FAIL: gdb.dwarf2/pieces-optimized-out.exp: print s

The regression was caused by this removal in cp-valprint.c:

  @@ -293,12 +293,6 @@ cp_print_value_fields (struct type *type, struct type *real_type,
		  {
		    fputs_filtered (_("<synthetic pointer>"), stream);
		  }
  -             else if (!value_bits_valid (val,
  -                                         TYPE_FIELD_BITPOS (type, i),
  -                                         TYPE_FIELD_BITSIZE (type, i)))
  -               {
  -                 val_print_optimized_out (val, stream);
  -               }
		else
		  {
		    struct value_print_options opts = *options;

The idea was that we'd just fallback to calling value_field_bitfield,
which handles unavailable values (in unpack_value_bits_as_long_1) so
should be able to handle optimized out values too.  Alas, it doesn't.
This is currently a bit too messy.  Instead of teaching
unpack_value_bits_as_long_1 about optimized out bits, let's bite the
bullet and teach the value code to handle partially optimized out
bitfield, by having it unpack a bitfield and then propagate the range
metadata.  Turns out the resulting code looks simpler and clearer.

Tested on x86_64 Fedora 20, -m64/-m32.

gdb/ChangeLog:

	* value.c (value_ranges_copy_adjusted): New function, factored out
	from ...
	(value_contents_copy_raw): ... here.
	(unpack_value_bits_as_long_1): Rename back to ...
	(unpack_bits_as_long): ... this.  Remove 'original_value' and
	'result' parameters.  Change return type to LONGEST.
	(unpack_value_bits_as_long): Delete.
	(unpack_value_field_as_long_1): Delete.
	(unpack_value_field_as_long, unpack_field_as_long): Reimplement.
	(unpack_value_bitfield): New function.
	(value_field_bitfield): Reimplement using unpack_value_bitfield.
	(value_fetch_lazy): Use unpack_value_bitfield.
	* value.h (unpack_value_bits_as_long): Delete declaration.