[PATCH] support static nested constructors in bitfields (2/2)

[Olivier Hainque <hainque at adacore dot com>]

Hello,

This is the second part of the output_constructor rework to let it
handle nested aggregates in bitfields.

The general idea is to introduce a simple datastructure to keep track
of the current bitfield state and recurse, together with a predicate
to decide which values are handled and are thus considered valid
static initializers for bitfields.

Bootstrapped and regression tested on x86_64-suse-linux.

We are also using this internally with a GCC 4.3 base on a number of
other targets.

Thanks in advance,

Olivier

2008-07-24  Olivier Hainque  <hainque@adacore.com>
            Eric Botcazou  <ebotcazou@adacore.com>

	Support for output of static nested constructors within bitfields
	* varasm.c (initializer_constant_valid_for_bitfield_p): New
	predicate. Whether VALUE is a valid constant-valued expression
	for use in initializing a static bit-field.
	(oc_outer_state): New type. output_constructor outer state of
	relevance in recursive calls.
	(oc_local_state): byte_buffer_in_use is bool, not int.  Add a
	"last_relative_index" field to memorize the index of the last
	array element output within a bitfield.
	(output_constructor_array_range): Minor prototype and head
	comment adjustments.
	(output_constructor_regular_field): Likewise.  Adjust assignments
	to byte_buffer_in_use, now bool.
	(output_constructor_bitfield): Likewise.  Accept an OUTER state
	argument for recursive processing.  Recurse on record or array
	CONSTRUCTOR values, possibly past noop conversions.
	(output_constructor): Accept and honor an OUTER state argument for
	recursive calls + return total size.  Be prepared for nested
	constructors initializing bitfields and consider BLKmode toplevel
	fields as regular even if DECL_BIT_FIELD is set.
	(output_constant): Feed OUTER in calls to output_constructor.
	* output.h (initializer_constant_valid_for_bitfield_p): Declare.

	ada/
	* utils2.c (gnat_build_constructor): Factor out code.  Use
	initializer_constant_valid_for_bitfield_p for bit-fields and
	account for BLKmode in addition to DECL_BIT_FIELD as in
	output_constructor.

	testsuite/
	* gnat.dg/oconst[1-6].ad[bs]: New tests. Also support for ...
	* gnat.dg/test_oconst.adb: New test.