Implement C11 _Atomic

This patch, relative to trunk and based on work done on the C11-atomic
branch, adds support for C11 _Atomic.  It is intended to include all
the required language support.

It does not include the <stdatomic.h> header; there's a version on the
branch, but it needs further review against the standard and test
coverage adding to the testsuite before I can propose it for mainline.

Support for atomic types having bigger alignment than the
corresponding non-atomic types is limited: it includes the code to
increase the alignment of types whose size is exactly 1, 2, 4, 8 or 16
to that of the corresponding integer type [*], but not anything for
target-specific alignment increases.  There's code for target-specific
alignment on the branch (and I intend to merge trunk back to the
branch once this patch is on trunk, so it's easy to tell what the
changes still left on the branch are), should any target maintainers
wish to have such alignment.  Note however that ideally libstdc++
atomics would be ABI-compatible with C atomics, requiring them to get
the same alignment; the branch has an "atomic" attribute for that
purpose, but I think further work on the C++ front-end changes would
be needed for them to be ready for mainline.

[*] The c-common.c code to resolve size-generic atomic built-in
functions to size-specific ones assumes that types are naturally
aligned (and so resolves to calls to the size-specific functions that
require natural alignment) without checking it.  If users should be
able to use the size-generic functions on types with lesser alignment,
e.g. _Complex double (8-byte rather than 16-byte aligned), rather than
just on their _Atomic variants, this is of course a bug in the code
resolving those built-in functions.  (The libatomic functions properly
check for alignment at runtime.)  But it seems reasonable enough
anyway to make _Atomic _Complex double 16-byte aligned.

Full use of _Atomic requires linking with libatomic, if you're doing
any atomic operations that aren't fully expanded inline; arguably
libatomic should be linked in by default with --as-needed (given that
previously ordinary C code didn't require the user to link any
libraries explicitly unless they directly called library functions),
but that's independent of this patch.  Correct handling of atomic
compound assignment for floating-point types also requires built-in
support for floating-point environment manipulation operations roughly
equivalent to feholdexcept, feclearexcept and feupdateenv (built-ins
are used to avoid introducing libm dependencies, which generic C code
not actually calling libm library functions shouldn't require); this
patch includes such support for x86 [*], and I expect other
architectures to be simpler.  If you don't have a libatomic port, the
execution tests for _Atomic simply won't be run; if you have libatomic
but not the floating-point support, the tests will be run but
c11-atomic-exec-5.c will fail (assuming the library features are
present for that test to run at all - it also requires pthreads).

[*] This could be optimized if desired by passing the types in
question to the target hook so it can generate code for only one of
x87 and SSE in most cases, much like an optimization present in glibc
when it internally does feholdexcept / fesetenv / feupdateenv
sequences.

_Atomic support is currently disabled for Objective-C and OpenMP.  For
both (but mainly OpenMP), the relevant parser code needs checking to
determine where convert_lvalue_to_rvalue calls need inserting to
ensure that accesses to atomic variables involve atomic loads.  For
Objective-C, there are also various special cases of compound
assignment that need special handling for atomics just as standard C
compound assignment is handled differently for atomics, as well as
some TYPE_MAIN_VARIANT calls to check for correctness for atomics; see
the comment on the relevant sorry () call for details.  OpenMP should
also have TYPE_MAIN_VARIANT uses checked as well as a use of
TYPE_QUALS_NO_ADDR_SPACE for a diagnostic in
c_parser_omp_declare_reduction (where the diagnostic refers to a
particular list of qualifiers).

Bootstrapped with no regressions on x86_64-unknown-linux-gnu.  OK to
commit (the various non-front-end pieces)?

gcc:
2013-11-05  Andrew MacLeod  <amacleod@redhat.com>
	    Joseph Myers  <joseph@codesourcery.com>

	* tree-core.h (enum cv_qualifier): Add TYPE_QUAL_ATOMIC.
	(enum tree_index): Add TI_ATOMICQI_TYPE, TI_ATOMICHI_TYPE,
	TI_ATOMICSI_TYPE, TI_ATOMICDI_TYPE and TI_ATOMICTI_TYPE.
	(struct tree_base): Add atomic_flag field.
	* tree.h (TYPE_ATOMIC): New accessor macro.
	(TYPE_QUALS, TYPE_QUALS_NO_ADDR_SPACE): Add TYPE_QUAL_ATOMIC.
	(TYPE_QUALS_NO_ADDR_SPACE_NO_ATOMIC): New macro.
	(atomicQI_type_node, atomicHI_type_node, atomicSI_type_node)
	(atomicDI_type_node, atomicTI_type_node): New macros for type
	nodes.
	* tree.c (set_type_quals): Set TYPE_ATOMIC.
	(find_atomic_core_type): New function.
	(build_qualified_type): Adjust alignment for qualified types.
	(build_atomic_base): New function
	(build_common_tree_nodes): Build atomicQI_type_node,
	atomicHI_type_node, atomicSI_type_node, atomicDI_type_node and
	atomicTI_type_node.
	* print-tree.c (print_node): Print atomic qualifier.
	* tree-pretty-print.c (dump_generic_node): Print atomic type
	attribute.
	* target.def (atomic_assign_expand_fenv): New hook.
	* doc/tm.texi.in (TARGET_ATOMIC_ASSIGN_EXPAND_FENV): New @hook.
	* doc/tm.texi: Regenerate.
	* targhooks.c (default_atomic_assign_expand_fenv): New function.
	* targhooks.h (default_atomic_assign_expand_fenv): Declare.
	* sync-builtins.def (__atomic_feraiseexcept): New built-in
	function.
	* config/i386/i386-builtin-types.def (VOID_FTYPE_PUSHORT): New
	function type.
	* config/i386/i386.c (enum ix86_builtins): Add
	IX86_BUILTIN_FNSTENV, IX86_BUILTIN_FLDENV, IX86_BUILTIN_FNSTSW and
	IX86_BUILTIN_FNCLEX.
	(bdesc_special_args): Add __builtin_ia32_fnstenv,
	__builtin_ia32_fldenv, __builtin_ia32_fnstsw and
	__builtin_ia32_fnclex.
	(ix86_expand_builtin): Handle the new built-in functions.
	(ix86_atomic_assign_expand_fenv): New function.
	(TARGET_ATOMIC_ASSIGN_EXPAND_FENV): New macro.
	* config/i386/i386.md (UNSPECV_FNSTENV, UNSPECV_FLDENV)
	(UNSPECV_FNSTSW, UNSPECV_FNCLEX): New unspecs.
	(fnstenv, fldenv, fnstsw, fnclex): New insns.

gcc/c-family:
2013-11-05  Andrew MacLeod  <amacleod@redhat.com>
	    Joseph Myers  <joseph@codesourcery.com>

	* c-common.h (enum rid): Add RID_ATOMIC.
	* c-common.c (c_common_reswords): Add _Atomic.
	(sync_resolve_params): Use TYPE_MAIN_VARIANT on pointer argument.
	(keyword_is_type_qualifier): Accept RID_ATOMIC.
	* c-format.c (check_format_types): Check for extra _Atomic
	qualifiers in format argument.
	* c-pretty-print.c (pp_c_cv_qualifiers): Handle atomic qualifier.
	(pp_c_type_qualifier_list): Mention _Atomic in comment.

gcc/c:
2013-11-05  Joseph Myers  <joseph@codesourcery.com>
	    Andrew MacLeod  <amacleod@redhat.com>

	* c-aux-info.c (gen_type): Handle atomic qualifier.
	* c-decl.c (validate_proto_after_old_defn): Do not remove atomic
	qualifiers when compating types.
	(shadow_tag_warned): Handle atomic_p in declspecs.
	(quals_from_declspecs): Likewise.
	(start_decl): Use c_type_promotes_to when promoting argument
	types.
	(grokdeclarator): Handle _Atomic.
	(get_parm_info): Diagnose any qualifier on "void" as only
	parameter.
	(store_parm_decls_oldstyle): Do not remove atomic qualifiers when
	comparing types.  Use c_type_promotes_to when promoting argument
	types.
	(finish_function): Use c_type_promotes_to when promoting argument
	types.
	(build_null_declspecs): Handle atomic_p in declspecs.
	(declspecs_add_qual): Handle RID_ATOMIC.
	* c-parser.c (c_token_starts_typename, c_token_is_qualifier)
	(c_token_starts_declspecs): Handle RID_ATOMIC.
	(c_parser_declspecs): Handle atomic type specifiers and
	qualifiers.
	(c_parser_typeof_specifier): Remove const and _Atomic qualifiers
	from types of expressions with atomic type.
	(c_parser_direct_declarator_inner): Use convert_lvalue_to_rvalue.
	(c_parser_attribute_any_word): Handle RID_ATOMIC.
	(c_parser_initializer, c_parser_initelt, c_parser_initval)
	(c_parser_statement_after_labels, c_parser_switch_statement)
	(c_parser_for_statement, c_parser_expr_no_commas)
	(c_parser_conditional_expression, c_parser_binary_expression)
	(c_parser_cast_expression, c_parser_unary_expression)
	(c_parser_postfix_expression)
	(c_parser_postfix_expression_after_primary, c_parser_expression):
	Use convert_lvalue_to_rvalue.
	(c_parser_expression_conv, c_parser_expr_list): Document
	conversion of lvalues to rvalues.  Use convert_lvalue_to_rvalue.
	(c_parser_objc_synchronized_statement): Use
	convert_lvalue_to_rvalue.
	(c_parser_objc_selector): Handle RID_ATOMIC.
	(c_parser_objc_receiver, c_parser_array_notation): Use
	convert_lvalue_to_rvalue.
	* c-tree.h (ctsk_typeof): Adjust comment to mention use for
	_Atomic (type-name).
	(struct c_declspecs): Add atomic_p field.
	(convert_lvalue_to_rvalue): Declare.
	* c-typeck.c (c_type_promotes_to): Promote atomic types to
	corresponding atomic types.
	(qualify_type): Don't add _Atomic qualifiers from second argument.
	(comp_target_types): Do not allow _Atomic mismatches.
	(type_lists_compatible_p): Do not remove atomic qualifiers when
	comparing types.
	(really_atomic_lvalue, convert_lvalue_to_rvalue)
	(build_atomic_assign): New functions.
	(build_unary_op): Use build_atomic_assign for atomic increment and
	decrement.
	(build_conditional_expr): Do not treat _Atomic void as a qualified
	version of void.
	(build_modify_expr): Use build_atomic_assign for atomic LHS.
	(find_anonymous_field_with_type, convert_to_anonymous_field)
	(convert_for_assignment): Do not remove atomic qualifiers when
	comparing types.
	(digest_init): Do not accept initialization of arrays of atomic
	elements by string constants.
	(build_asm_expr): Use convert_lvalue_to_rvalue.
	(build_binary_op): Do not treat _Atomic void as a qualified
	version of void.

gcc/objc:
2013-11-05  Andrew MacLeod  <amacleod@redhat.com>

	* objc-act.c (objc_push_parm): Handle atomic qualifier.

gcc/testsuite:
2013-11-05  Joseph Myers  <joseph@codesourcery.com>

	* lib/target-supports.exp
	(check_effective_target_fenv_exceptions): New function.
	* lib/atomic-dg.exp, gcc.dg/atomic/atomic.exp: New files.
	* gcc.dg/atomic/c11-atomic-exec-1.c,
	gcc.dg/atomic/c11-atomic-exec-2.c,
	gcc.dg/atomic/c11-atomic-exec-3.c,
	gcc.dg/atomic/c11-atomic-exec-4.c,
	gcc.dg/atomic/c11-atomic-exec-5.c, gcc.dg/c11-atomic-1.c,
	gcc.dg/c11-atomic-2.c, gcc.dg/c11-atomic-3.c,
	gcc.dg/c90-atomic-1.c, gcc.dg/c99-atomic-1.c: New tests.

libatomic:
2013-11-05  Joseph Myers  <joseph@codesourcery.com>

	* fenv.c: New file.
	* libatomic.map (LIBATOMIC_1.1): New symbol version.  Include
	__atomic_feraiseexcept.
	* configure.ac (libtool_VERSION): Change to 2:0:1.
	(fenv.h): Test for header.
	* Makefile.am (libatomic_la_SOURCES): Add fenv.c.
	* Makefile.in, auto-config.h.in, configure: Regenerate.

Implement C11 _Atomic

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