From-SVN: r278663

2019-11-24  Jerry DeLisle  <jvdelisle@gcc.ngu.org>

	PR fortran/92100
	io/transfer.c (data_transfer_init_worker): Use fbuf_reset
	instead of fbuf_flush before the seek. Note that fbuf_reset
	calls fbuf_flush and adjusts fbuf pointers.

From-SVN: r278660

2019-11-23  Thomas Koenig  <tkoenig@gcc.gnu.org>
	Harald Anlauf <anlauf@gmx.de>

	PR fortran/92569
	* io/transfer.c (transfer_array_inner):  If position is
	at AFTER_ENDFILE in current unit, return from data loop.

2019-11-23  Thomas Koenig  <tkoenig@gcc.gnu.org>
	Harald Anlauf <anlauf@gmx.de>

	PR fortran/92569
	* gfortran.dg/eof_6.f90: New test.


Co-Authored-By: Harald Anlauf <anlauf@gmx.de>

From-SVN: r278659

Adds iterator singular check within the valid range check.

	* include/debug/functions.h: Remove <bits/move.h> include.
	(__check_singular_aux, __check_singular): Move...
	* include/debug/helper_functions.h:
	(__check_singular_aux, __check_singular): ...here.
	(__valid_range_aux): Adapt to use latter.
	Add <bits/move.h> include.
	* testsuite/25_algorithms/copy/debug/2_neg.cc: New.

From-SVN: r278658

	* combine.c (can_combine_p): Allow autoinc in jumps.

From-SVN: r278656

	* combine.c (combine_instructions): Record costs for jumps.

From-SVN: r278655

	* config/i386/i386.c (ix86_rtx_costs): Handle care of a PLUS in a
	COMPARE, representing an overflow detection.

From-SVN: r278654

From-SVN: r278653

From-SVN: r278648

2019-11-23  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/92442
	* gfortran.dg/bounds_check_21.f90: New test.

From-SVN: r278647

/bin/sh: :q: command not found
This patch adds opt_for_fn for all cross module params used by inliner
so they can be modified at function granuality.  With inlining almost always
there are three functions to consider (callee and caller of the inlined edge
and the outer function caller is inlined to).

I always use the outer function params since that is how local parameters
behave.  I hope it is kind of what is also expected in most case: it is better
to inline agressively into -O3 compiled code rather than inline agressively -O3
functions into their callers.

New params infrastructure is nice.  One drawback is that is very hard to
search for individual param uses since they all occupy global namespace.
With C++ world we had chance to do something like params.param_flag_name
or params::param_flag_name instead...

Bootstrapped/regtested x86_64-linux, comitted.

	* cif-code.def (MAX_INLINE_INSNS_SINGLE_O2_LIMIT): Remove.
	* doc/invoke.texi (max-inline-insns-single-O2,
	inline-heuristics-hint-percent-O2, inline-min-speedup-O2,
	early-inlining-insns-O2): Remove documentation.
	* ipa-fnsummary.c (analyze_function_body,
	compute_fn_summary): Use opt_for_fn when accessing parameters.
	* ipa-inline.c (caller_growth_limits, can_inline_edge_p,
	inline_insns_auto, can_inline_edge_by_limits_p,
	want_early_inline_function_p, big_speedup_p,
	want_inline_small_function_p, want_inline_self_recursive_call_p,
	recursive_inlining, compute_max_insns, inline_small_functions):
	Likewise.
	* opts.c (default_options): Add -O3 defaults for
	OPT__param_early_inlining_insns_,
	OPT__param_inline_heuristics_hint_percent_,
	OPT__param_inline_min_speedup_, OPT__param_max_inline_insns_single_.
	* params.opt (-param=early-inlining-insns-O2=,
	-param=inline-heuristics-hint-percent-O2=,
	-param=inline-min-speedup-O2=, -param=max-inline-insns-single-O2=
	-param=early-inlining-insns=, -param=inline-heuristics-hint-percent=,
	-param=inline-min-speedup=, -param=inline-unit-growth=,
	-param=large-function-growth=, -param=large-stack-frame=,
	-param=large-stack-frame-growth=, -param=large-unit-insns=,
	-param=max-inline-insns-recursive=,
	-param=max-inline-insns-recursive-auto=,
	-param=max-inline-insns-single=,
	-param=max-inline-insns-size=, -param=max-inline-insns-small=,
	-param=max-inline-recursive-depth=,
	-param=max-inline-recursive-depth-auto=,
	-param=min-inline-recursive-probability=,
	-param=partial-inlining-entry-probability=,
	-param=uninlined-function-insns=, -param=uninlined-function-time=,
	-param=uninlined-thunk-insns=, -param=uninlined-thunk-time=): Add
	Optimization.

	* g++.dg/tree-ssa/pr53844.C: Drop -O2 from param name.
	* g++.dg/tree-ssa/pr61034.C: Likewise.
	* g++.dg/tree-ssa/pr8781.C: Likewise.
	* g++.dg/warn/Wstringop-truncation-1.C: Likewise.
	* gcc.dg/ipa/pr63416.c: Likewise.
	* gcc.dg/tree-ssa/ssa-thread-12.c: Likewise.
	* gcc.dg/vect/pr66142.c: Likewise.
	* gcc.dg/winline-3.c: Likewise.
	* gcc.target/powerpc/pr72804.c: Likewise.

From-SVN: r278645

This patch adds opt_for_fn for all cross module params used by inliner
so they can be modified at function granuality.  With inlining almost always
there are three functions to consider (callee and caller of the inlined edge
and the outer function caller is inlined to).

I always use the outer function params since that is how local parameters
behave.  I hope it is kind of what is also expected in most case: it is better
to inline agressively into -O3 compiled code rather than inline agressively -O3
functions into their callers.

New params infrastructure is nice.  One drawback is that is very hard to
search for individual param uses since they all occupy global namespace.
With C++ world we had chance to do something like params.param_flag_name
or params::param_flag_name instead...

Bootstrapped/regtested x86_64-linux, comitted.

	* cif-code.def (MAX_INLINE_INSNS_SINGLE_O2_LIMIT): Remove.
	* doc/invoke.texi (max-inline-insns-single-O2,
	inline-heuristics-hint-percent-O2, inline-min-speedup-O2,
	early-inlining-insns-O2): Remove documentation.
	* ipa-fnsummary.c (analyze_function_body,
	compute_fn_summary): Use opt_for_fn when accessing parameters.
	* ipa-inline.c (caller_growth_limits, can_inline_edge_p,
	inline_insns_auto, can_inline_edge_by_limits_p,
	want_early_inline_function_p, big_speedup_p,
	want_inline_small_function_p, want_inline_self_recursive_call_p,
	recursive_inlining, compute_max_insns, inline_small_functions):
	Likewise.
	* opts.c (default_options): Add -O3 defaults for
	OPT__param_early_inlining_insns_,
	OPT__param_inline_heuristics_hint_percent_,
	OPT__param_inline_min_speedup_, OPT__param_max_inline_insns_single_.
	* params.opt (-param=early-inlining-insns-O2=,
	-param=inline-heuristics-hint-percent-O2=,
	-param=inline-min-speedup-O2=, -param=max-inline-insns-single-O2=
	-param=early-inlining-insns=, -param=inline-heuristics-hint-percent=,
	-param=inline-min-speedup=, -param=inline-unit-growth=,
	-param=large-function-growth=, -param=large-stack-frame=,
	-param=large-stack-frame-growth=, -param=large-unit-insns=,
	-param=max-inline-insns-recursive=,
	-param=max-inline-insns-recursive-auto=,
	-param=max-inline-insns-single=,
	-param=max-inline-insns-size=, -param=max-inline-insns-small=,
	-param=max-inline-recursive-depth=,
	-param=max-inline-recursive-depth-auto=,
	-param=min-inline-recursive-probability=,
	-param=partial-inlining-entry-probability=,
	-param=uninlined-function-insns=, -param=uninlined-function-time=,
	-param=uninlined-thunk-insns=, -param=uninlined-thunk-time=): Add
	Optimization.

	* g++.dg/tree-ssa/pr53844.C: Drop -O2 from param name.
	* g++.dg/tree-ssa/pr61034.C: Likewise.
	* g++.dg/tree-ssa/pr8781.C: Likewise.
	* g++.dg/warn/Wstringop-truncation-1.C: Likewise.
	* gcc.dg/ipa/pr63416.c: Likewise.
	* gcc.dg/tree-ssa/ssa-thread-12.c: Likewise.
	* gcc.dg/vect/pr66142.c: Likewise.
	* gcc.dg/winline-3.c: Likewise.
	* gcc.target/powerpc/pr72804.c: Likewise.

From-SVN: r278644

	* ipa-fnsummary.c: Fix comment typos.
	* ipa-ref.h: Likewise.
	* ipa-predicate.h: Likewise.
	* ipa-split.c: Likewise.
	* ipa-inline-analysis.c: Likewise.
	* ipa-predicate.c: Likewise.
	* ipa-devirt.c: Likewise.
	* ipa-icf.h: Likewise.
	* profile-count.c: Likewise.
	* ipa-icf.c: Likewise.
	(sem_function::equals_wpa): Fix typos in dump messages.
	* ipa-icf-gimple.h: Fix comment typos.
	* ipa-inline-transform.c: Likewise.
	* ipa-polymorphic-call.c: Likewise.
	* ipa-fnsummary.h: Likewise.
	* ipa-inline.c: Likewise.
	(dump_inline_stats): Fix typo in debug dump message.
	* profile-count.h: Fix comment typos.

From-SVN: r278643

	PR target/92615
	* config/i386/i386.c (ix86_md_asm_adjust): If dest_mode is
	GET_MODE (dest), is not QImode, using ZERO_EXTEND and dest is not
	register_operand, force x into register before storing it into dest.
	Formatting fix.

	* gcc.target/i386/pr92615.c: New test.

From-SVN: r278642

re PR middle-end/83859 (Please add new attribute which will establish relation between parameters for buffer and its size)

	PR middle-end/83859
	* doc/extend.texi (attribute access): Fix a typo.

	* c-attribs.c (append_access_attrs): Avoid buffer overflow.  Avoid
	memory leak.  Use XNEWVEC macro.  Use auto_diagnostic_group to
	group warning with inform together.
	(handle_access_attribute): Formatting fix.

From-SVN: r278641

	PR rtl-optimization/92610
	* cse.c (rest_of_handle_cse2): Call cleanup_cfg (0) also if
	cse_cfg_altered is set, even when tem is 0.
	(rest_of_handle_cse_after_global_opts): Likewise.

	* g++.dg/opt/pr92610.C: New test.

From-SVN: r278640

PR c++/92365

2019-11-22  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        PR c++/92365
        * name-lookup.c (check_local_shadow): Use can_convert_arg
        instead of can_convert.

testsuite:
2019-11-22  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        PR c++/92365
        * g++.dg/pr92365.C: New test.

From-SVN: r278639

From-SVN: r278638

Part of P1327R1 is to allow typeid with an operand of polymorphic type in
constexpr.  I found that we pretty much support it already, the only tweak
was to allow TYPEID_EXPR (only created in a template) in constexpr in C++20.

	* constexpr.c (potential_constant_expression_1): Allow a typeid
	expression whose operand is of polymorphic type in constexpr in
	C++20.
	* rtti.c (build_typeid): Remove obsolete FIXME comment.

	* g++.dg/cpp2a/constexpr-typeid1.C: New test.
	* g++.dg/cpp2a/constexpr-typeid2.C: New test.
	* g++.dg/cpp2a/constexpr-typeid3.C: New test.
	* g++.dg/cpp2a/constexpr-typeid4.C: New test.

From-SVN: r278635

re PR c/90677 (gcc-9.1.0 fails to build __gcc_diag__ souce: error: 'cgraph_node' is not defined as a type)

	PR c/90677
	* c-common.h (identifier_global_tag): Declare.
	* c-format.c (get_pointer_to_named_type): Renamed to ...
	(get_named_type): ... this.  Use identifier_global_tag instead of
	identifier_global_value, handle the return value being a TYPE_P.
	(init_dynamic_diag_info): Adjust get_pointer_to_named_type callers
	to call get_named_type instead.  Formatting fixes.
c/
	* c-decl.c (identifier_global_tag): Define.
cp/
	* cp-objcp-common.c (identifier_global_tag): Define.
testsuite/
	* c-c++-common/pr90677.c: New test.

From-SVN: r278634

	PR c++/92458
	* tree-hash-traits.h (tree_decl_hash, tree_ssa_name_hash,
	tree_hash): Move to ...
	* tree.h (tree_decl_hash, tree_ssa_name_hash, tree_hash): ... here.
	(struct decl_tree_cache_traits, struct type_tree_cache_traits): New
	types.
	(decl_tree_cache_map, tree_tree_cache_map): New typedefs.

	* init.c (nsdmi_inst): Change type to
	decl_tree_cache_map * from tree_cache_map *.
	* constraint.cc (decl_constraints): Likewise.
	* decl.c (get_tuple_decomp_init): Likewise.
	* pt.c (defarg_inst, explicit_specifier_map): Likewise.
	(tsubst_default_argument, store_explicit_specifier): Use
	decl_tree_cache_map::create_ggc rather than
	tree_cache_map::create_ggc.
	* cp-objcp-common.c (debug_type_map): Change type to
	type_tree_cache_map * from tree_cache_map *.

	* g++.dg/pch/pr92458.C: New test.
	* g++.dg/pch/pr92458.Hs: New test.

From-SVN: r278633

The tests amended here now have different code-gen with default
options because, previously, the access were indirected per Darwin
ABI for common accesses.  The revised code-gen does not match the
expected scan-asms because Darwin defaults to fPIC.  For these tests,
it seems that the best solution is to use '-mdynamic-no-pic' in the
m32 case which makes the output similar to the ElF platform default.

gcc/testsuite/ChangeLog:

2019-11-22  Iain Sandoe  <iain@sandoe.co.uk>

	* gcc.target/i386/pr27971.c: Use mdynamic-no-pic for m32 on
	Darwin.
	* gcc.target/i386/sse2-load-multi.c: Likewise.
	* gcc.target/i386/sse2-store-multi.c: Likewise.

From-SVN: r278631

From-SVN: r278630

	* c-cppbuiltin.c (c_cpp_builtins): Bump __cpp_init_captures
	and __cpp_generic_lambdas for -std=c++2a.  Define
	__cpp_designated_initializers, __cpp_constexpr_in_decltype and
	__cpp_consteval for -std=c++2a.  Remove a FIXME comment about
	__cpp_concepts for -std=c++2a.

	* g++.dg/cpp1z/feat-cxx1z.C: Only compile with -std=c++17.
	* g++.dg/cpp2a/feat-cxx2a.C: Adjust for P1902R1 changes.
	* g++.dg/cpp2a/desig15.C: New test.
	* g++.dg/cpp2a/lambda-pack-init3.C: New test.
	* g++.dg/cpp2a/lambda-generic6.C: New test.
	* g++.dg/cpp2a/consteval15.C: New test.

From-SVN: r278628

	PR tree-optimization/92618
	* tree-ssa-reassoc.c (v_info): Change from auto_vec to a struct
	containing the auto_vec and a tree.
	(undistribute_bitref_for_vector): Handle the case when element type
	of vec is not the same as type of the BIT_FIELD_REF.  Formatting
	fixes.

	* gcc.c-torture/compile/pr92618.c: New test.
	* gcc.c-torture/execute/pr92618.c: New test.

From-SVN: r278626

gcc/ChangeLog:

	PR middle-end/83859
	* attribs.h (struct attr_access): New.
	* attribs.c (decl_attributes): Add an informational note.
	* builtins.c (check_access): Make extern.  Consistently set no-warning
	after issuing a warning.  Handle calls through function pointers.  Set
	no-warning.
	* builtins.h (check_access): Declare.
	* calls.c (rdwr_access_hash): New type.
	(rdwr_map): Same.
	(init_attr_rdwr_indices): New function.
	(maybe_warn_rdwr_sizes): Same.
	(initialize_argument_information): Call init_attr_rdwr_indices.
	Call maybe_warn_rdwr_sizes.
	(get_size_range): Avoid null argument.
	* doc/extend.texi (attribute access): Document new attribute.

gcc/c-family/ChangeLog:

	PR middle-end/83859
	* c-attribs.c (handle_access_attribute): New function.
	(c_common_attribute_table): Add new attribute.
	(get_argument_type): New function.
	(append_access_attrs): New function.
	(get_nonnull_operand): Rename...
	(get_attribute_operand): ...to this.
	* c-common.c (get_nonnull_operand): Rename...
	(get_attribute_operand): ...to this.

gcc/testsuite/ChangeLog:

	PR middle-end/83859
	* c-c++-common/attr-nonstring-8.c: Adjust text of expected warning.
	* gcc.dg/Wstringop-overflow-23.c: New test.
	* gcc.dg/Wstringop-overflow-24.c: New test.
	* gcc.dg/attr-access-read-only.c: New test.
	* gcc.dg/attr-access-read-write.c: New test.
	* gcc.dg/attr-access-read-write-2.c: New test.
	* gcc.dg/attr-access-write-only.c: New test.

From-SVN: r278624

gcc/ChangeLog:

	PR middle-end/88226
	* builtins.c (check_nul_terminated_array): New function.
	(fold_builtin_0): Remove declaration.
	(fold_builtin_1): Same.
	(fold_builtin_2): Same.
	(fold_builtin_3): Same.
	(fold_builtin_strpbrk): Add argument.
	(fold_builtin_strspn): Same.
	(fold_builtin_strcspn): Same.
	(expand_builtin_strcat): Call it.  Remove unused argument.
	(expand_builtin_stpncpy): Same.
	(expand_builtin_strncat): Same.
	(expand_builtin_strncpy): Same.  Adjust indentation.
	(expand_builtin_strcmp): Same.
	(expand_builtin_strncmp): Same.
	(expand_builtin_fork_or_exec): Same.
	(expand_builtin): Handle more built-ins.
	(fold_builtin_2): Add argument.
	(fold_builtin_n): Make static.  Add argument.
	(fold_call_expr): Pass new argument to fold_builtin_n and fold_builtin_2.
	(fold_builtin_call_array): Pass new argument to fold_builtin_n.
	(fold_builtin_strpbrk): Add argument.  Call check_nul_terminated_array.
	(fold_call_stmt): Pass new argument to fold_builtin_n.
	* builtins.h: Correct a comment.
	* gimple-fold.c (gimple_fold_builtin_strchr): Call
	check_nul_terminated_array.
	* tree-ssa-strlen.c (handle_builtin_strlen): Call
	check_nul_terminated_array.
	(handle_builtin_strchr): Same.
	(handle_builtin_string_cmp): Same.

gcc/testsuite/ChangeLog:

	PR middle-end/88226
	* gcc.dg/Wstringop-overflow-22.c: New test.
	* gcc.dg/tree-ssa/builtin-fprintf-warn-1.c: Remove xfails.

From-SVN: r278623

2019-11-22  Andrew Stubbs  <ams@codesourcery.com>

	gcc/
	* config/gcn/gcn.c (OMP_LDS_SIZE): Define.
	(ACC_LDS_SIZE): Define.
	(OTHER_LDS_SIZE): Define.
	(LDS_SIZE): Redefine using above.
	(gcn_expand_prologue): Initialize m0 with LDS_SIZE-1.

From-SVN: r278622

gcc/testsuite/ChangeLog:

	PR tree-optimization/92501
	* gcc.dg/strcmpopt_7.c: New test.

gcc/ChangeLog:

	PR tree-optimization/92501
	* gimple-fold.c ((gimple_fold_builtin_string_compare): Let strncmp
	handle unterminated arrays.  Rename local variables for clarity.

From-SVN: r278621

2019-11-22  Andrew Stubbs  <ams@codesourcery.com>

	gcc/
	* config/gcn/gcn.c (gcn_hsa_declare_function_name): Calculate
	granulated_sgprs according to architecture.

From-SVN: r278617

	* ggc-page.c (ggc_collect): Call memory_block_pool::trim.
	* memory-block.cc (memory_block_pool::clear_free_list): Rename to ...
	(memory_block_pool::reduce_free_list): ... this one.
	(memory_block_pool::trim): New static function.
	* memory-block.h (memory_block_pool::freelist_size): New constant
	(memory_block_pool::clear_free_list): Rename to ...
	(memory_block_pool::reduce_free_list): ... this one.
	(memory_block_pool::trim): Declare.
	
	* lto.c (lto_wpa_write_files): Call memory_block_pool::trim.

From-SVN: r278616

vect-widen-mult-u8.c and vect-widen-mult-u8-u32.c were failing
on arm-linux-gnueabihf with epilogue vectorisation because we
print the expected messages twice rather than once.  We could
fix that either by removing the counts or by disabling epilogue
loop vectorisation.  The other vect-widen-mult-* tests do the
latter, so I did the same here.

2019-11-22  Richard Sandiford  <richard.sandiford@arm.com>

gcc/testsuite/
	* gcc.dg/vect/vect-widen-mult-u8.c: Disable epilogue loop
	vectorization.
	* gcc.dg/vect/vect-widen-mult-u8-u32.c: Likewise.

From-SVN: r278613

gcc.dg/vect/vect-cond-reduc-3.c had been failing on
arm-linux-gnueabihf since the test was added, because the test needs
support for VEC_COND_EXPR <float cmp float, int, int> whereas the target
only supports VEC_COND_EXPRs in which all modes are the same.  (I have
a fix for that, but it's not really stage 3 material.)

2019-11-22  Richard Sandiford  <richard.sandiford@arm.com>

gcc/testsuite/
	* gcc.dg/vect/vect-cond-reduc-3.c: Require vect_cond_mixed
	rather than vect_condition.

From-SVN: r278612

gcc.target/aarch64/sve/clastb_[57].c started failing after the increase
in the cost of vec_to_scalar (r278452).  The problem is that we were
double-counting the cost of the CLASTB: once in vect_model_reduction_cost
as a vec_to_scalar and once in vectorizable_condition as a plain
vector_stmt.

Based on the TODO above vect_model_reduction_cost, I think the
preferred long-term direction is for vectorizable_* to cost these
things itself, so that's what the patch does (for this one case only).

2019-11-22  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* tree-vect-stmts.c (vect_model_simple_cost): Take an optional
	vect_cost_for_stmt.
	(vectorizable_condition): Calculate the cost of EXTRACT_LAST_REDUCTION
	here rather than...
	* tree-vect-loop.c (vect_model_reduction_cost): ...here.

From-SVN: r278611

The patterns neg_scc_insn and not_scc_insn are not correct, leading to
failing pr77309 test for ARC700. Add two new bic compare with zero
patterns to improve output code.

gcc/
xxxx-xx-xx  Claudiu Zissulescu  <claziss@synopsys.com>

	* config/arc/arc.md (bic_f): Use cc_set_register predicate.
	(bic_cmp0_noout): New pattern.
	(bic_cmp0): Likewise.
	(neg_scc_insn): Remove pattern.
	(not_scc_insn): Likewise.

From-SVN: r278610

Fix ARC specific tests by improving the matching pattern and adding
the missing functionality in arc.exp

gcc/tests
xxxx-xx-xx  Claudiu Zissulescu  <claziss@synopsys.com>

	* gcc.target/arc/add_n-combine.c: Match add1/2/3 instruction in
	output assembly.
	* gcc.target/arc/arc.exp (check_effective_target_codedensity):
	Add.
	* gcc.target/arc/cmem-7.c: Fix matching patterns.
	* gcc.target/arc/cmem-bit-1.c: Likewise.
	* gcc.target/arc/cmem-bit-2.c: Likewise.
	* gcc.target/arc/cmem-bit-3.c: Likewise.
	* gcc.target/arc/cmem-bit-4.c: Likewise.
	* gcc.target/arc/interrupt-2.c: Match rtie insn for A7.
	* gcc.target/arc/store-merge-1.c: This test is only meaningful for
	architectures with double load/store operations.

From-SVN: r278609

gcc/testsuite/ChangeLog:
	* gcc.dg/strlenopt-66.c: Avoid buffer overflow.  Add more test cases.

From-SVN: r278608

From-SVN: r278607

The patch to make -fcommon the default introduces a bogus claim into
the GCC documentation.

-fcommon was claimed to be incompatible with ISO C for preventing
duplicate definitions from being diagnosed.  It does, but as that
elicits undefined behaviour (the requirement that there shall be no
more than one external definition is not a constraint), ISO C does not
require any diagnostic for it.  In the absence of any other rule this
would violate, both -fcommon and -fno-common are fully compatible with
all versions of ISO C.

2019-11-21  Harald van Dijk  <harald@gigawatt.nl>

	* doc/invoke.texi (-fcommon): Remove claim about ISO C.

From-SVN: r278604

Various bad uses of the [[fallthrough]] attribute are constraint
violations in C2x, so need pedwarns rather than warnings.

This patch duly turns the relevant warnings into pedwarns.  The
relevant code is not specific to C, and does not know which form the
attribute was given in ([[fallthrough]] or [[gnu::fallthrough]] or
__attribute__((fallthrough))), but as I understand it these usages are
also erroneous for C++ and it seems reasonable to give a pedwarn here
even when a form other than [[fallthrough]] is being used.

The precise meaning of the standard wording about "The next statement
that would be executed" seems a but unclear in some corner cases; the
tests added keep to cases where it is clear whether or not the next
statement executed is of the required form.

Bootstrapped with no regressions for x86_64-pc-linux-gnu.

gcc:
	* gimplify.c (expand_FALLTHROUGH_r, expand_FALLTHROUGH): Use
	pedwarn instead of warning_at for fallthrough not preceding a case
	or default label.

gcc/c-family:
	* c-attribs.c (handle_fallthrough_attribute): Use pedwarn instead
	of warning.

gcc/testsuite:
	* gcc.dg/c2x-attr-fallthrough-6.c: New test.  Split out from
	c2x-attr-fallthrough-3.c.
	* gcc.dg/c2x-attr-fallthrough-1.c: Add more tests.
	* gcc.dg/c2x-attr-fallthrough-2.c: Update expected diagnostics.
	* gcc.dg/c2x-attr-fallthrough-3.c: Split inside-switch part of
	test out to c2x-attr-fallthrough-6.c.

From-SVN: r278599