libphobos/ChangeLog:

	* m4/druntime/os.m4: Update comment for DRUNTIME_OS_SOURCES.

The D run-time library does not depend on zlib, so only include it in
the library when Phobos is being built as well.

libphobos/ChangeLog:

	* src/Makefile.am: Don't add zlib when ENABLE_LIBDRUNTIME_ONLY.
	* src/Makefile.in: Regenerate.

The following testcase is miscompiled on aarch64-linux at -O3 since the
introduction of WIDEN_MINUS_EXPR.
The problem is if the inner type (half_type) is unsigned and the result
type in which the subtraction is performed (type) has precision more than
twice as larger as the inner type's precision.
For other widening operations like WIDEN_{PLUS,MULT}_EXPR, if half_type
is unsigned, the addition/multiplication result in itype is also unsigned
and needs to be zero-extended to type.
But subtraction is special, even when half_type is unsigned, the subtraction
behaves as signed (also regardless of whether the result type is signed or
unsigned), 0xfeU - 0xffU is -1 or 0xffffffffU, not 0x0000ffff.

I think it is better not to use mixed signedness of types in
WIDEN_MINUS_EXPR (have unsigned vector of operands and signed result
vector), so this patch instead adds another cast to make sure we always
sign-extend the result from itype to type if type is wider than itype.

2021-09-01  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/102124
	* tree-vect-patterns.c (vect_recog_widen_op_pattern): For ORIG_CODE
	MINUS_EXPR, if itype is unsigned with smaller precision than type,
	add an extra cast to signed variant of itype to ensure sign-extension.

	* gcc.dg/torture/pr102124.c: New test.

gcc/ChangeLog:

	* graph.c (draw_cfg_node_succ_edges): Do not color fallthru
	  edges and rather use colors for TRUE and FALSE edges.

This makes us avoid PREing calls that could trap across other
calls that might not return.  The PR88087 testcase has exactly
such case so I've refactored the testcase to contain a valid PRE.
I've also adjusted PRE to not consider pure calls possibly
not returning in line with what we do elsewhere.

Note we don't have a good idea whether a function always returns
normally or whether its body is known to never trap.  That's
something IPA could compute.

2021-09-01  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/93491
	* tree-ssa-pre.c (compute_avail): Set BB_MAY_NOTRETURN
	after processing the stmt itself.  Do not consider
	pure functions possibly not returning.  Properly avoid
	adding possibly trapping calls to EXP_GEN when there's
	a preceeding possibly not returning call.
	* tree-ssa-sccvn.c (vn_reference_may_trap): Conservatively
	not handle calls.

	* gcc.dg/torture/pr93491.c: New testcase.
	* gcc.dg/tree-ssa/pr88087.c: Change to valid PRE opportunity.

When doing whole-function SLP we have to make sure the recorded
base alignments we compute as the maximum alignment seen for a
base anywhere in the function is actually valid at the point
we want to make use of it.

To make this work we now record the stmt the alignment was derived
from in addition to the DRs innermost behavior and we use a
dominance check to verify the recorded info is valid when doing
BB vectorization.  For this to work for groups inside a BB that are
separate by a call that might not return we now store the DR
analysis group-id permanently and use that for an additional check
when the DRs are in the same BB.

2021-08-31  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/102139
	* tree-vectorizer.h (vec_base_alignments): Adjust hash-map
	type to record a std::pair of the stmt-info and the innermost
	loop behavior.
	(dr_vec_info::group): New member.
	* tree-vect-data-refs.c (vect_record_base_alignment): Adjust.
	(vect_compute_data_ref_alignment): Verify the recorded
	base alignment can be used.
	(data_ref_pair): Remove.
	(dr_group_sort_cmp): Adjust.
	(vect_analyze_data_ref_accesses): Store the group-ID in the
	dr_vec_info and operate on a vector of dr_vec_infos.

	* gcc.dg/torture/pr102139.c: New testcase.

ChangeLog:
	* MAINTAINERS: Add myself for write after approval.

Currently, the enums from define_c_enum and define_enum can only
has values one by one from 0.

In fact we can support the behaviour just like C, aka like
  (define_enum "mips_isa" [(mips1 1) mips2 (mips32 32) mips32r2]),
then we can get
  enum mips_isa {
    MIPS_ISA_MIPS1 = 1,
    MIPS_ISA_MIPS2 = 2,
    MIPS_ISA_MIPS32 = 32,
    MIPS_ISA_MIPS32R2 = 33
  };

gcc/ChangeLog:
	* read-md.c (md_reader::handle_enum): support value assignation.
	* doc/md.texi: record define_c_enum value assignation support.

bswap_view_convert is used twice in spots where gsi_insert_before is the
right thing, but in the last one it wants to insert preparation stmts
for the VIEW_CONVERT_EXPR emitted with gsi_insert_after, where at the
gsi we still need to insert bswap_stmt and maybe mask_stmt whose lhs
the preparation stmts will use.
So, this patch adds a BEFORE argument to the function and emits the
preparation statements before or after depending on that.

2021-09-01  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/102141
	* gimple-ssa-store-merging.c (bswap_view_convert): Add BEFORE
	argument.  If false, emit stmts after gsi instead of before, and
	with GSI_NEW_STMT.
	(bswap_replace): Adjust callers.  When converting output of bswap,
	emit VIEW_CONVERT prepratation stmts after a copy of gsi instead
	of before it.

	* gcc.dg/pr102141.c: New test.

This adds the testcase from the PR.

2021-09-01  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/102149
	* gcc.dg/torture/pr102149.c: New testcase.

This patch fixes an ICE during error-recovery regression in the C front-end.
The symptom is that the middle-end's sanity checking assertions fail during
gimplification when being asked to increment an array, which is non-sense.
The issue is that the C-front end has detected the type mismatch and
reported an error to the user, but hasn't provided any indication of this
to the middle-end, simply passing bogus trees that the optimizers recognize
as invalid.

This appears to be a frequently reported ICE with 94730, 94731, 101036
and 101365 all marked as duplicates.

I believe the correct (polite) fix is to mark the mismatched types as
problematic/dubious in the front-end, when the error is spotted, so that
the middle-end has a heads-up and can be a little more forgiving.  This
patch to c-decl.c's duplicate_decls sets (both) mismatched types to
error_mark_node if they are significantly different, and we've issued
an error message.  Alas, this is too punitive for FUNCTION_DECLs where
we store return types, parameter lists, parameter types and attributes
in the type, but fortunately the middle-end is already more cautious
about trusting possibly suspect function types.

This fix required one minor change to the testsuite, typedef-var-2.c
where after conflicting type definitions, we now no longer assume that
the (first or) second definition is the correct one.  This change only
affects the behaviour after seen_error(), so should be relatively safe.

2021-09-01  Roger Sayle  <roger@nextmovesoftware.com>
	    Joseph Myers  <joseph@codesourcery.com>

gcc/c/ChangeLog
	PR c/79412
	* c-decl.c (duplicate_decls): On significant mismatches, mark the
	types of both (non-function) decls as error_mark_node, so that the
	middle-end can see the code is malformed.
	(free_attr_access_data): Don't process if the type has been set to
	error_mark_node.

gcc/testsuite/ChangeLog
	PR c/79412
	* gcc.dg/pr79412.c: New test case.
	* gcc.dg/typedef-var-2.c: Update expeted errors.

gcc/ChangeLog:

	* emit-rtl.c (validate_subreg): Get rid of all float-int
	special cases.

This reverts commit 7218c2ec.

     PR middle-end/102133

A copy-paste error, a couple of missed checks to guard undefined accesses,
and we don't need to use type_uses_auto to extract the auto node we just
built.

gcc/cp/ChangeLog:

	* coroutines.cc (flatten_await_stmt): Fix copyo.
	* decl.c (reshape_init_class): Simplify.
	* module.cc (module_state::read_language): Add null check.
	* parser.c (build_range_temp): Avoid type_uses_auto.
	(cp_parser_class_specifier_1): Add null check.

gcc/fortran/ChangeLog:

	PR fortran/100950
	* simplify.c (substring_has_constant_len): Minimize checks for
	substring expressions being allowed.

gcc/testsuite/ChangeLog:

	PR fortran/100950
	* gfortran.dg/pr100950.f90: Extend coverage.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	PR libstdc++/98421
	* include/std/span (span(Iter, size_type), span(Iter, Iter)):
	Add valid range checks.
	* testsuite/23_containers/span/cons_1_assert_neg.cc: New test.
	* testsuite/23_containers/span/cons_2_assert_neg.cc: New test.

During overload resolution, when the arity of a function template
clearly disagrees with the arity of the call, no specialization of the
function template could yield a viable candidate.  The deduction routine
type_unification_real already notices this situation, but not before
it substitutes explicit template arguments into the template, a step
which could induce a hard error.  Although it's necessary to perform
this substitution first in order to check arity perfectly (since the
substitution can e.g. expand a non-trailing parameter pack), in most
cases we can determine ahead of time whether there's an arity
disagreement without needing to perform deduction at all.

To that end, this patch implements an (approximate) arity check in
add_template_candidate_real that guards actual deduction.  It's enabled
only when there are explicit template arguments since that's when
deduction can force otherwise avoidable template instantiations.  (I
experimented with enabling it unconditionally as an optimization, and
observed some improvements to compile time of about 5% but also some
slowdowns of about the same magnitude, so kept it conditional.)

In passing, this adds a least_p parameter to arity_rejection for sake
of consistent diagnostics with unify_arity.

A couple of testcases needed to be adjusted so that deduction continues
to occur as intended after this change.  Except in unify6.C, where we
were expecting foo<void ()> to be ill-formed due to substitution
forming a function type with an added 'const', but ISTM this is
permitted by [dcl.fct]/7, so I changed the test accordingly.

	PR c++/12672

gcc/cp/ChangeLog:

	* call.c (rejection_reason::call_varargs_p): Rename this
	previously unused member to ...
	(rejection_reason::least_p): ... this.
	(arity_rejection): Add least_p parameter.
	(add_template_candidate_real): When there are explicit
	template arguments, check that the arity of the call agrees with
	the arity of the function before attempting deduction.
	(print_arity_information): Add least_p parameter.
	(print_z_candidate): Adjust call to print_arity_information.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/decltype29.C: Adjust.
	* g++.dg/template/error56.C: Adjust.
	* g++.old-deja/g++.pt/unify6.C: Adjust.
	* g++.dg/template/explicit-args7.C: New test.

In r245300 (commit 02889d23)
"OpenACC tile clause support" that one had changed to three operands,
similar to 'OMP_CLAUSE_COLLAPSE'.

There is no (existing) test case where this seems to matter (likewise
for 'OMP_CLAUSE_COLLAPSE'), but it's good to be consistent.

	gcc/
	* tree.c (walk_tree_1) <OMP_CLAUSE_TILE>: Handle three operands.

... instead of 'omp_is_reference' vs.
'lang_hooks.decls.omp_privatize_by_reference'.

	gcc/
	* omp-general.h (omp_is_reference): Rename to...
	(omp_privatize_by_reference): ... this.  Adjust all users...
	* omp-general.c: ... here, ...
	* gimplify.c: ... here, ...
	* omp-expand.c: ... here, ...
	* omp-low.c: ... here.

	* gimple-ssa-warn-access.cc (maybe_warn_alloc_args_overflow): Test
	pointer element for equality to zero, not that of the cotaining
	array.

gcc/cp/ChangeLog:

	* parser.c (cp_parser_selection_statement): Use direct initialization
	instead of copy.

gcc/ChangeLog:

	* gcc-rich-location.h (gcc_rich_location): Make ctor explicit.

libcpp/ChangeLog:

	* include/line-map.h (class rich_location): Disable copying and
	assignment.

gcc/ChangeLog:
	* function.h (function): Add comments.
	(get_range_query): Same.  Add attribute returns nonnull.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	* configure.ac: Fix checks for F_GETFL, F_SETFL and O_NONBLOCK.
	* configure: Regenerate.

These destructors are noexcept anyway. I removed the redundant noexcept
from the error_category destructor's declaration in r0-123475, but
didn't remove it from the defaulted definition in system_error.cc. That
causes warnings if the library is built with Clang.

This removes the redundant noexcept from ~error_category and
~system_error and adds tests to ensure they really are noexcept.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	* src/c++11/system_error.cc (error_category::~error_category()):
	Remove noexcept-specifier.
	(system_error::~system_error()): Likewise.
	* testsuite/19_diagnostics/error_category/noexcept.cc: New test.
	* testsuite/19_diagnostics/system_error/noexcept.cc: New test.

This adds a missing return statement to the non-futex wait-until
operation.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	PR libstdc++/102074
	* include/bits/atomic_timed_wait.h (__timed_waiter_pool)
	[!_GLIBCXX_HAVE_PLATFORM_TIMED_WAIT]: Add missing return.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	* include/experimental/internet (__make_resolver_error_code):
	Handle EAI_SYSTEM errors.
	(basic_resolver_results): Use __make_resolver_error_code. Use
	Glibc NI_MAXHOST and NI_MAXSERV values for buffer sizes.

Solaris 11 does not have "http" in /etc/services, which causes this test
to fail. Try some other services until we find one that works.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	* testsuite/experimental/net/internet/resolver/ops/lookup.cc:
	Try other service if "http" fails.

My apologies for the inconvenience.  My recent patch to preserve
SUBREG_PROMOTED_VAR_P on (extend:HI (subreg/s:QI (reg:SI))), and other
places in the middle-end, has broken the build on several targets.

The change to convert_modes inadvertently used the same
subreg_promoted_mode idiom for retrieving the mode of a SUBREG_REG
as the existing code just a few lines earlier.  Alas in the meantime,
the original SUBREG gets replaced by one without SUBREG_PROMOTED_VAR_P,
the whole raison-d'etre for my patch, and I'd not realized/noticed
that subreg_promoted_mode asserts for this.  Alas neither the bootstrap
and regression test on x86_64-pc-linux-gnu nor my testing on nvptx-none
must have hit this particular case.  The logic of this transformation
is sound, it's the implementation that's bitten me.

This patch has been committed, after another "make bootstrap" on
x86_64-pc-linux-gnu (just in case), and confirmation/pre-approval
from Jeff Law that this indeed fixes the build failures seen on
several platforms.

My humble apologies again.

2021-08-31  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	* expr.c (convert_modes): Don't use subreg_promoted_mode on a
	SUBREG if it can't be guaranteed to a SUBREG_PROMOTED_VAR_P set.
	Instead use the standard (safer) is_a <scalar_int_mode> idiom.

Another place we can use iloc_sentinel instead of explicitly saving and
restoring input_location.

gcc/cp/ChangeLog:

	* constexpr.c (explain_invalid_constexpr_fn): Use iloc_sentinel.

The compiler tries to limit error cascades in limit_bad_template_recursion
by avoiding triggering a new instantiation from one that has caused errors.
We were exempting constexpr functions from this because they can be needed
for constant evaluation, but as more and more functions get marked
constexpr, this becomes an over-broad category.  So as suggested on IRC,
this patch only exempts functions that are needed for mandatory constant
evaluation.

As noted in the comment, this flag doesn't particularly need to use a bit in
the FUNCTION_DECL, but there were still some free.

	PR c++/92193

gcc/cp/ChangeLog:

	* cp-tree.h (FNDECL_MANIFESTLY_CONST_EVALUATED): New.
	* constexpr.c (cxx_eval_call_expression): Set it.
	* pt.c (neglectable_inst_p): Check it.

gcc/testsuite/ChangeLog:

	* g++.dg/diagnostic/static_assert4.C: New test.

gcc/testsuite
	* gcc.target/mips/mips.exp: Add tree-vrp to mips_option_group.
	* gcc.target/mips/data-sym-multi-pool.c: Add -fno-tree-vrp.

gcc/

	* config.gcc (cris-*-elf, cris-*-none): Remove dbxelf.h from
	tm_file.
	(m32r-*-elf, m32rle-*-elf, m32r-*-linux): Likewise.
	(mn10300-*-*, am33_2.0-*-linux*): Likewise.
	(xtensa*-*-elf, xtensa*-*-linux, xtensa*-*-uclinux): Likewise.
	(m32c-*-elf*, m32c-*-rtems*): Likewise.
	* config/cris/cris.h (DBX_NO_XREFS): Remove.
	(DBX_CONTIN_LENGTH, DBX_CONTIN_CHAR): Likewise.
	* config/m32r/m32r.h (DBXOUT_SOURCE_LINE): Likewise.
	(DBX_DEBUGGING_INFO, DBX_CONTIN_LENGTH): Likewise.
	* config/mn10300/mn10300.h (DEFAULT_GDB_EXTENSIONS): Likewise.
	* config/mn10300/linux.h (DBX_REGISTER_NAMES): Likewise.

I'm getting:
FAIL: gcc.dg/vect/pr101145.c scan-tree-dump-times vect "vectorized 1 loops" 7
FAIL: gcc.dg/vect/pr101145_1.c scan-tree-dump-times vect "vectorized 1 loops" 2
FAIL: gcc.dg/vect/pr101145_2.c scan-tree-dump-times vect "vectorized 1 loops" 2
FAIL: gcc.dg/vect/pr101145_3.c scan-tree-dump-times vect "vectorized 1 loops" 2
FAIL: gcc.dg/vect/pr101145.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 7
FAIL: gcc.dg/vect/pr101145_1.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 2
FAIL: gcc.dg/vect/pr101145_2.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 2
FAIL: gcc.dg/vect/pr101145_3.c -flto -ffat-lto-objects  scan-tree-dump-times vect "vectorized 1 loops" 2
on i686-linux (or x86_64-linux with -m32/-mno-sse).
The problem is that those tests use dg-options, which in */vect/ testsuite
throws away all the carefully added default options to enable vectorization
on each target (and which e.g. vect_int etc. effective targets rely on).
The old way would be to name those tests gcc.dg/vect/O3-pr101145*,
but we can also use dg-additional-options (which doesn't throw the default
options, just appends to them) which is IMO better so that we don't have to
rename the tests.

2021-08-31  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/101145
	* gcc.dg/vect/pr101145.c: Use dg-additional-options with just -O3
	instead of dg-options with -O3 -fdump-tree-vect-details.
	* gcc.dg/vect/pr101145_1.c: Likewise.
	* gcc.dg/vect/pr101145_2.c: Likewise.
	* gcc.dg/vect/pr101145_3.c: Likewise.

'device_num' and 'ancestor' are now parsed on target device constructs for C,
C++, and Fortran (see OpenMP specification 5.0, p. 170). When 'ancestor' is
 used, then 'sorry, not supported' is output. Moreover, the restrictions for
'ancestor' are implemented (see OpenMP specification 5.0, p. 174f).

gcc/c/ChangeLog:

	* c-parser.c (c_parser_omp_clause_device): Parse device-modifiers 'device_num'
	and 'ancestor' in 'target device' clauses.

gcc/cp/ChangeLog:

	* parser.c (cp_parser_omp_clause_device): Parse device-modifiers 'device_num'
	and 'ancestor' in 'target device' clauses.
	* semantics.c (finish_omp_clauses): Error handling. Constant device ids must
	evaluate to '1' if 'ancestor' is used.

gcc/fortran/ChangeLog:

	* gfortran.h: Add variable for 'ancestor' in struct gfc_omp_clauses.
	* openmp.c (gfc_match_omp_clauses): Parse device-modifiers 'device_num'
	and 'ancestor' in 'target device' clauses.
	* trans-openmp.c (gfc_trans_omp_clauses): Set OMP_CLAUSE_DEVICE_ANCESTOR.

gcc/ChangeLog:

	* gimplify.c (gimplify_scan_omp_clauses): Error handling. 'ancestor' only
	allowed on target constructs and only with particular other clauses.
	* omp-expand.c (expand_omp_target): Output of 'sorry, not supported' if
	'ancestor' is used.
	* omp-low.c (check_omp_nesting_restrictions): Error handling. No nested OpenMP
	structs when 'ancestor' is used.
	(scan_omp_1_stmt): No usage of OpenMP runtime routines in a target region when
	'ancestor' is used.
	* tree-pretty-print.c (dump_omp_clause): Append 'ancestor'.
	* tree.h (OMP_CLAUSE_DEVICE_ANCESTOR): Define macro.

gcc/testsuite/ChangeLog:

	* c-c++-common/gomp/target-device-1.c: New test.
	* c-c++-common/gomp/target-device-2.c: New test.
	* c-c++-common/gomp/target-device-ancestor-1.c: New test.
	* c-c++-common/gomp/target-device-ancestor-2.c: New test.
	* c-c++-common/gomp/target-device-ancestor-3.c: New test.
	* c-c++-common/gomp/target-device-ancestor-4.c: New test.
	* gfortran.dg/gomp/target-device-1.f90: New test.
	* gfortran.dg/gomp/target-device-2.f90: New test.
	* gfortran.dg/gomp/target-device-ancestor-1.f90: New test.
	* gfortran.dg/gomp/target-device-ancestor-2.f90: New test.
	* gfortran.dg/gomp/target-device-ancestor-3.f90: New test.
	* gfortran.dg/gomp/target-device-ancestor-4.f90: New test.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	* testsuite/17_intro/names.cc: Undefine some more names used
	by Solaris system headers.

SUBREG_PROMOTED_VAR_P is a mechanism for tracking that a partial subreg
is correctly zero-extended or sign-extended in the parent register.  For
example, the RTL (subreg/s/v:QI (reg/v:SI 23 [ x ]) 0) indicates that the
byte x is zero extended in reg:SI 23, which is useful for optimization.
An example is that zero extending the above QImode value to HImode can
simply use a wider subreg, i.e. (subreg:HI (reg/v:SI 23 [ x ]) 0).

This patch addresses the oversight/missed optimization opportunity that
the new HImode subreg above should retain its SUBREG_PROMOTED_VAR_P
annotation as its value is guaranteed to be correctly extended in the
SImode parent.  The code below to preserve SUBREG_PROMOTED_VAR_P is already
present in the middle-end (e.g. simplify-rtx.c:7232-7242) but missing
from one or two (precisely three) places that (accidentally) strip it.

Whilst there I also added another optimization.  If we need to extend
the above QImode value beyond the SImode register holding it, say to
DImode, we can eliminate the SUBREG and simply extend from the SImode
register to DImode.

2021-08-31  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	* expr.c (convert_modes): Preserve SUBREG_PROMOTED_VAR_P when
	creating a (wider) partial subreg from a SUBREG_PROMOTED_VAR_P
	subreg.
	* simplify-rtx.c (simplify_unary_operation_1) [SIGN_EXTEND]:
	Likewise, preserve SUBREG_PROMOTED_VAR_P when creating a (wider)
	partial subreg from a SUBREG_PROMOTED_VAR_P subreg.  Generate
	SIGN_EXTEND of the SUBREG_REG when a subreg would be paradoxical.
	[ZERO_EXTEND]: Likewise, preserve SUBREG_PROMOTED_VAR_P when
	creating a (wider) partial subreg from a SUBREG_PROMOTED_VAR_P
	subreg.  Generate ZERO_EXTEND of the SUBREG_REG when a subreg
	would be paradoxical.

As recently remarked by Jeff Law, SUBREGs are the "forever chemicals"
of GCC's RTL; once created they persist in the environment.  The problem,
according to the comment on lines 5428-5438 of combine.c is that
non-tieable SUBREGs interfere with reload/register allocation, so
combine often doesn't touch/clean-up instructions containing a SUBREG.

This is the first and simplest of two patches to tackle that problem,
by teaching combine to avoid converting explicit TRUNCATEs into
SUBREGs that it can't handle.

Consider the following (hypothetical) sequence of instructions on
a STORE_FLAG_VALUE=1 target, which stores a zero or one in an SI
register, then uselessly truncates to QImode, then extends it again.

(set (reg:SI 27) (ne:SI (reg:BI 28) (const_int 0)))
(set (reg:QI 26) (truncate:QI (reg:SI 27)))
(set (reg:SI 0) (zero_extend:SI (reg:QI 26)))

which ideally (i.e. with this patch) combine would simplify to:
(set (reg:SI 0) (ne:SI (reg:BI 28) (const_int 0)))

Alas currently, during combine the middle TRUNCATE is converted into
a lowpart SUBREG, which subst then turns into (clobber (const_int 0)),
abandoning the attempted combination, that then never reaches recog.

2021-08-31  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	* combine.c (combine_simplify_rtx): Avoid converting an explicit
	TRUNCATE into a lowpart SUBREG on !TRULY_NOOP_TRUNCATION targets.
	* simplify-rtx.c (simplify_unary_operation_1): Likewise.

This fixes a typo in the condition guarding the cleanup of the
visited flag of costed scalar stmts.

2021-08-31  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/102142
	* tree-vect-slp.c (vect_bb_vectorization_profitable_p): Fix
	condition under which to unset the visited flag.

	* g++.dg/torture/pr102142.C: New testcase.

Quoting from https://gcc.gnu.org/pipermail/gcc/2021-July/236716.html:

--------------------------------------------------------------------
It was pointed out to me off-list that config/aarch64/value-unwind.h
is missing the runtime exception.  It looks like a few other files
are too; a fuller list is:

libgcc/config/aarch64/value-unwind.h
libgcc/config/frv/frv-abi.h
libgcc/config/i386/value-unwind.h
libgcc/config/pa/pa64-hpux-lib.h

Certainly for the aarch64 file this was simply a mistake;
it seems to have been copied from the i386 version, both of which
reference the runtime exception but don't actually include it.
--------------------------------------------------------------------

Similarly, frv-abi.h referenced the exception but didn't include it.
pa64-hpux-lib.h was missing any reference to the exception.

The decision was that this was simply a mistake
[https://gcc.gnu.org/pipermail/gcc/2021-July/236717.html]:

--------------------------------------------------------------------
[…] It generally is
considered a textual omission.  The runtime library components of GCC
are intended to be licensed under the runtime exception, which was
granted and approved at the time of introduction.
--------------------------------------------------------------------

and that we should simply change all of the files above
[https://gcc.gnu.org/pipermail/gcc/2021-July/236719.html]:

--------------------------------------------------------------------
Please correct the text in the files. The files in libgcc used in the
GCC runtime are intended to be licensed with the runtime exception and
GCC previously was granted approval for that licensing and purpose.

[…]

The runtime exception explicitly was intended for this purpose and
usage at the time that GCC received approval to apply the exception.
--------------------------------------------------------------------

libgcc/
	* config/aarch64/value-unwind.h: Add missing runtime exception
	paragraph.
	* config/frv/frv-abi.h: Likewise.
	* config/i386/value-unwind.h: Likewise.
	* config/pa/pa64-hpux-lib.h: Likewise.