[patch] change specific int128 -> generic intN

[DJ Delorie <dj at redhat dot com>]

This patch replaces the current int128 support with a generic intN
support, which happens to provide int128 as well as up to three
additional intN types per target.  I will post a separate patch for
the msp430 backend demonstrating the use of this new feature for
__int20, as well as a third to fix some problems with PSImode in
general.

The general idea is that genmodes has a new macro INT_N() for
<tm>-modes.def, which gives the mode and precision to use for
target-specific intN types.  These types are always created, but the
parser will error with "unsupported" if the target does not support
that mode for that compile (i.e. because of command line switches,
etc).  There's an INT_N(TI,128) in the common sources.

If the target defines any types larger than "long long", those types
(like int128 before) will be used for type promotion, but types
smaller than "long long" will not, to avoid confusing the C type
promotion rules.  Otherwise, it's up to the source being compiled to
specific __intN types as desired.

The only non-automatic part of this is the table of pre-computed
constants in builtin_define_type_minmax() (c-family/c-cppbuiltin.c).
I've added the entries for int20 and int24 but each target will need
to expand the table as needed.

gcc/

	* machmode.h (int_n_data_t): New.
	(int_n_enabled_p): New.
	(int_n_data): New.
	* tree.c (int_n_enabled_p): New.
	(int_n_trees): New.
	(make_or_reuse_type): Check for all __intN types, not just
	__int128.
	(build_common_tree_nodes): Likewise.  Also fill in integer_typs[]
	entries.
	* tree.h (int128_integer_type_node): Remove.
	(int128_unsigned_type_node): Remove.
	(int_n_trees_t): New.
	(int_n_enabled_p): New.
	(int_n_trees): New.
	* toplev.c (standard_type_bitsize): New.
	(do_compile): Check which __intN types are enabled for the current
	run.
	* builtin-types.def (BT_INT128): Remove.
	(BT_UINT128): Remove.
	* machmode.def: Add macro to create __intN for all targets.
	* stor-layout.c (mode_for_size): Support __intN types.
	(smallest_mode_for_size): Likewise.
	* genmodes.c (struct mode_data): Add int_n field.
	(blank_mode): Likewise.
	(INT_N): New.
	(make_int_n): New.
	(emit_insn_modes_h): Count __intN entries and define
	NUM_INT_N_ENTS.
	(emit_mode_int_n): New.
	(emit_insn_modes_c): Call it.
	* gimple.c (gimple_signed_or_unsigned_type): Check for all __intN
	types, not just __int128.
	* tree-core.h (integer_type_kind): Remove __int128-specific
	entries, reserve spots for __intN entries.

gcc/c-family/

	* c-pretty-print.c (pp_c_integer_constant): Check for all __intN
	types, not just __int128.
	* c-cppbuiltin.c (c_cpp_builtins): Add builtins for all __intN
	types, not just __int128.
	* c-common.c (c_common_reswords): Remove __int128 special case.
	(c_common_type_for_size): Check for all __intN types, not just
	__int128.
	(c_common_type_for_mode): Likewise.
	(c_common_signed_or_unsigned_type): Likewise.
	(c_build_bitfield_integer_type): Likewise.
	(c_common_nodes_and_builtins): Likewise.
	(keyword_begins_type_specifier): Likewise.
	* c-common.h (rid): Remove RID_INT128 and add RID_INT_N_* for all
	__intN variants.

gcc/c/

	* c-parser.c (c_parse_init): Add RID entries for each __intN.
	(c_token_starts_typename): Check all __intN, not just __int128.
	(c_token_starts_declspecs): Likewise.
	(c_parser_declspecs): Likewise.
	(c_parser_attribute_any_word): Likewise.
	(c_parser_objc_selector): Likewise.
	* c-tree.h (c_typespec_keyword): cts_int128 -> cts_int_n.
	(struct c_declspecs): Add int_n_idx field to record *which* __intN
	is specified.
	* c-decl.c (declspecs_add_type): Check for all __intN, not just
	__int128.
	(finish_declspecs): Likewise.

gcc/cp/
	* typeck.c (cp_common_type): Check for all __intN types, not just
	__int128.
	* decl.c (grokdeclarator): Likewise.
	* rtti.c (emit_support_tinfos): Remove __int128-specific entries.
	* parser.c (cp_lexer_next_token_is_decl_specifier_keyword): Check
	for all __intN types, not just __int128.
	(cp_parser_simple_type_specifier): Likewise.
	* mangle.c (integer_type_codes): Remove int128-specific codes.
	* cp-tree.h (cp_decl_specifier_seq): Add int_n_idx to store which
	__intN was specified.
	* lex.c (init_reswords): Reserve all __intN keywords.

gcc/lto/
	* lto-lang.c (lto_build_c_type_nodes): Check intN types for
	size-type as well.
	(lto_init): Initialize all intN types, not just int128.