When a basic block A has been annotated with a count and it has only one
successor (or predecessor) B, we can propagate the A's count to B.
The algoritm without this change could leave B without an annotation if B had
other unannotated predecessors (or successors). For example, in the test case I added,
the loop header block was left unannotated, which prevented loop unrolling.

gcc/ChangeLog:
	* auto-profile.c (afdo_propagate_edge): Improve count propagation algorithm.

gcc/testsuite/ChangeLog:
	* gcc.dg/tree-prof/init-array.c: New test for unrolling inner loops.

Whilst debugging state explosions seen when enabling taint detection
with -fanalyzer (PR analyzer/103533), I noticed that constraint
manager instances could contain stray, redundant constants, such
as this instance:

constraint_manager:
  equiv classes:
    ec0: {(int)0 == [m_constant]‘0’}
    ec1: {(size_t)4 == [m_constant]‘4’}
  constraints:

where there are two equivalence classes, each just containing a
constant, with no constraints using them.

This patch makes constraint_manager::canonicalize more aggressive
about purging state, handling the case of purging a redundant
EC containing just a constant.

gcc/analyzer/ChangeLog:
	PR analyzer/103533
	* constraint-manager.cc (equiv_class::contains_non_constant_p):
	New.
	(constraint_manager::canonicalize): Call it when determining
	redundant ECs.
	(selftest::test_purging): New selftest.
	(selftest::run_constraint_manager_tests): Likewise.
	* constraint-manager.h (equiv_class::contains_non_constant_p):
	New decl.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>

Fixes 85289ba3.

2021-12-06  Paul A. Clarke  <pc@us.ibm.com>

gcc
	PR target/103545
	* config/rs6000/xmmintrin.h (_mm_movemask_ps): Replace "vector" with
	"__vector".

	* MAINTAINERS: Adding myself.

This patch does a little bit of cleanup by removing some unused
arguments, or marking them as unused.  It also removes the function
ctfc_debuginfo_early_finish_p and the corresponding hook macro
definition, which are not used by GCC.

gcc/
	* config/bpf/bpf.c (bpf_handle_preserve_access_index_attribute):
	Mark arguments `args' and flags' as unused.
	(bpf_core_newdecl): Remove unused local `newdecl'.
	(bpf_core_newdecl): Remove unused argument `loc'.
	(ctfc_debuginfo_early_finish_p): Remove unused function.
	(TARGET_CTFC_DEBUGINFO_EARLY_FINISH_P): Remove definition.
	(bpf_core_walk): Do not pass a location to bpf_core_newdecl.

When compiling an optabs.ii at -O2 with a release-checking build,
there were 6,643,575 calls to gimple_outgoing_range_stmt_p.  96.8% of
them were for blocks with a single successor, which never have a control
statement that generates new range info.  This patch therefore adds a
shortcut for that case.

This gives a ~1% compile-time improvement for the test.

I tried making the function inline (in the header) so that the
single_succ_p didn't need to be repeated, but it seemed to make things
slightly worse.

gcc/
	* gimple-range-edge.cc (gimple_outgoing_range::edge_range_p): Add
	a shortcut for blocks with single successors.
	* gimple-range-gori.cc (gori_map::calculate_gori): Likewise.

When compiling an optabs.ii at -O2 with a release-checking build,
the hottest function in the profile was irange_union.  This patch
tries to optimise it a bit.  The specific changes are:

- Use quick_push rather than safe_push, since the final number
  of entries is known in advance.

- Avoid assigning wi::to_wide & co. to a temporary wide_int,
  such as in:

    wide_int val_j = wi::to_wide (res[j]);

  wi::to_wide returns a wide_int "view" of the in-place INTEGER_CST
  storage.  Assigning the result to wide_int forces an unnecessary
  copy to temporary storage.

  This is one area where "auto" helps a lot.  In the end though,
  it seemed more readable to inline the wi::to_*s rather than
  use auto.

- Use to_widest_int rather than to_wide_int.  Both are functionally
  correct, but to_widest_int is more efficient, for three reasons:

  - to_wide returns a wide-int representation in which the most
    significant element might not be canonically sign-extended.
    This is because we want to allow the storage of an INTEGER_CST
    like 0x1U << 31 to be accessed directly with both a wide_int view
    (where only 32 bits matter) and a widest_int view (where many more
    bits matter, and where the 32 bits are zero-extended to match the
    unsigned type).  However, operating on uncanonicalised wide_int
    forms is less efficient than operating on canonicalised forms.

  - to_widest_int has a constant rather than variable precision and
    there are never any redundant upper bits to worry about.

  - Using widest_int avoids the need for an overflow check, since
    there is enough precision to add 1 to any IL constant without
    wrap-around.

This gives a ~2% compile-time speed up with the test above.

I also tried adding a path for two single-pair ranges, but it
wasn't a win.

gcc/
	* value-range.cc (irange::irange_union): Use quick_push rather
	than safe_push.  Use widest_int rather than wide_int.  Avoid
	assigning wi::to_* results to wide*_int temporaries.

Before walking the CFG and filling all cache entries, check if the
same information is available in a dominator.

	* gimple-range-cache.cc (ranger_cache::fill_block_cache): Check for
	a range from dominators before filling the cache.
	(ranger_cache::range_from_dom): New.
	* gimple-range-cache.h (ranger_cache::range_from_dom): Add prototype.

There are times we only need to know if any edge from a block can calculate
a range.

	* gimple-range-gori.h (class gori_compute):: Add prototypes.
	* gimple-range-gori.cc (gori_compute::has_edge_range_p): Add alternate
	API for basic block.  Call for edge alterantive.
	(gori_compute::may_recompute_p): Ditto.

Add

commit 70b04384
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Tue Nov 30 05:31:26 2021 -0800

    libsanitizer: Use SSE to save and restore XMM registers

to LOCAL_PATCHES.

	* LOCAL_PATCHES: Add commit 70b04384.

Use SSE, instead of AVX, to save and restore XMM registers to support
processors without AVX.  The affected codes are unused in upstream since

https://github.com/llvm/llvm-project/commit/66d4ce7e26a5

and will be removed in

https://reviews.llvm.org/D112604

This fixed

FAIL: g++.dg/tsan/pthread_cond_clockwait.C   -O0  execution test
FAIL: g++.dg/tsan/pthread_cond_clockwait.C   -O2  execution test

on machines without AVX.

	PR sanitizer/103466
	* tsan/tsan_rtl_amd64.S (__tsan_trace_switch_thunk): Replace
	vmovdqu with movdqu.
	(__tsan_report_race_thunk): Likewise.

The recent fix to PR103527 exposed an issue with how the various
special casing for AVX512 masks in vect_build_gather_load_calls
are handled.  The following makes that more obvious, fixing the
miscompile of 403.gcc.

2021-12-06  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/103581
	* tree-vect-stmts.c (vect_build_gather_load_calls): Properly
	guard all the AVX512 mask cases.

	* gcc.dg/vect/pr103581.c: New testcase.

contrib/ChangeLog:

	* filter-clang-warnings.py: Filter out one warning.

When SLP reduction chain vectorization support added handling of
an outer conversion in the chain picking a failed reduction up
as SLP reduction that broke the invariant that the whole reduction
was forward reachable.  The following plugs that hole noting
a future enhancement possibility.

2021-12-06  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/103544
	* tree-vect-slp.c (vect_analyze_slp): Only add a SLP reduction
	opportunity if the stmt in question is the reduction root.
	(dot_slp_tree): Add missing check for NULL child.

	* gcc.dg/vect/pr103544.c: New testcase.

On Mon, Dec 06, 2021 at 11:00:30AM +0100, Martin Liška wrote:
> Jakub, I think the patch broke avr-linux target:
>
> g++  -fno-PIE -c   -g   -DIN_GCC  -DCROSS_DIRECTORY_STRUCTURE   -fno-exceptions -fno-rtti -fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings -Wcast-qual -Wno-erro
> /home/marxin/Programming/gcc/gcc/config/avr/avr.c: In function ‘void avr_output_data_section_asm_op(const void*)’:
> /home/marxin/Programming/gcc/gcc/config/avr/avr.c:10097:26: error: invalid conversion from ‘const void*’ to ‘const char*’ [-fpermissive]

This patch fixes that.

2021-12-06  Jakub Jelinek  <jakub@redhat.com>

	PR pch/71934
	* config/avr/avr.c (avr_output_data_section_asm_op,
	avr_output_bss_section_asm_op): Change argument type from const void *
	to const char *.

CSE uses equivalence classes to keep track of expressions that all have the same
values at the current point in the program.

Normal equivalences through SETs only insert and perform lookups in this set but
equivalence determined from comparisons, e.g.

(insn 46 44 47 7 (set (reg:CCZ 17 flags)
        (compare:CCZ (reg:SI 105 [ iD.2893 ])
            (const_int 0 [0]))) "cse.c":18:22 7 {*cmpsi_ccno_1}
     (expr_list:REG_DEAD (reg:SI 105 [ iD.2893 ])
        (nil)))

creates the equivalence EQ on (reg:SI 105 [ iD.2893 ]) and (const_int 0 [0]).

This causes a merge to happen between the two equivalence sets denoted by
(const_int 0 [0]) and (reg:SI 105 [ iD.2893 ]) respectively.

The operation happens through merge_equiv_classes however this function has an
invariant that the classes to be merge not contain any duplicates.  This is
because it frees entries before merging.

The given testcase when using the supplied flags trigger an ICE due to the
equivalence set being

(rr) p dump_class (class1)
Equivalence chain for (reg:SI 105 [ iD.2893 ]):
(reg:SI 105 [ iD.2893 ])
$3 = void

(rr) p dump_class (class2)
Equivalence chain for (const_int 0 [0]):
(const_int 0 [0])
(reg:SI 97 [ _10 ])
(reg:SI 97 [ _10 ])
$4 = void

This happens because the original INSN being recorded is

(insn 18 17 24 2 (set (subreg:V1SI (reg:SI 97 [ _10 ]) 0)
        (const_vector:V1SI [
                (const_int 0 [0])
            ])) "cse.c":11:9 1363 {*movv1si_internal}
     (expr_list:REG_UNUSED (reg:SI 97 [ _10 ])
        (nil)))

and we end up generating two equivalences. the first one is simply that
reg:SI 97 is 0.  The second one is that 0 can be extracted from the V1SI, so
subreg (subreg:V1SI (reg:SI 97) 0) 0 == 0.  This nested subreg gets folded away
to just reg:SI 97 and we re-insert the same equivalence.

This patch changes it so that if the nunits of a subreg is 1 then don't generate
a vec_select from the subreg as the subreg will be folded away and we get a dup.

gcc/ChangeLog:

	PR rtl-optimization/103404
	* cse.c (find_sets_in_insn): Don't select elements out of a V1 mode
	subreg.

gcc/testsuite/ChangeLog:

	PR rtl-optimization/103404
	* gcc.target/i386/pr103404.c: New test.

When moves between integer and sse registers are cheap.

2021-12-06  Hongtao Liu  <Hongtao.liu@intel.com>
	    Uroš Bizjak  <ubizjak@gmail.com>
gcc/ChangeLog:

	PR target/95740
	* config/i386/i386.c (ix86_preferred_reload_class): Allow
	integer regs when moves between register units are cheap.
	* config/i386/i386.h (INT_SSE_CLASS_P): New.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/pr95740.c: New test.

This is the original binutils bugzilla report,
https://sourceware.org/bugzilla/show_bug.cgi?id=28509

And this is the first version of the proposed binutils patch,
https://sourceware.org/pipermail/binutils/2021-November/118398.html

After applying the binutils patch, I get the the unexpected error when
building libgcc,

/scratch/nelsonc/riscv-gnu-toolchain/riscv-gcc/libgcc/config/riscv/div.S:42:
/scratch/nelsonc/build-upstream/rv64gc-linux/build-install/riscv64-unknown-linux-gnu/bin/ld: relocation R_RISCV_JAL against `__udivdi3' which may bind externally can not be used when making a shared object; recompile with -fPIC

Therefore, this patch add an extra hidden alias symbol for __udivdi3, and
then use HIDDEN_JUMPTARGET to target a non-preemptible symbol instead.
The solution is similar to glibc as follows,
https://sourceware.org/git/?p=glibc.git;a=commit;h=68389203832ab39dd0dbaabbc4059e7fff51c29b

libgcc/ChangeLog:

	* config/riscv/div.S: Add the hidden alias symbol for __udivdi3, and
	then use HIDDEN_JUMPTARGET to target it since it is non-preemptible.
	* config/riscv/riscv-asm.h: Added new macros HIDDEN_JUMPTARGET and
	HIDDEN_DEF.

This moves the GTY declaration of the meta-data indentifier
array into the header that enumerates these and provides
shorthand defines for them.  This avoids a problem seen with
a relocatable PCH implementation.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>

gcc/objc/ChangeLog:

	* objc-next-metadata-tags.h (objc_rt_trees): Declare here.
	* objc-next-runtime-abi-01.c: Remove from here.
	* objc-next-runtime-abi-02.c: Likewise.
	* objc-runtime-shared-support.c: Reorder headers, provide
	a GTY declaration the definition of objc_rt_trees.

The new builtin machinery has an early exit, so move the AIX-specific
builtins before the new machinery.

gcc/ChangeLog:

	* config/rs6000/rs6000-call.c (rs6000_init_builtins): Move
	AIX math builtin initialization before new_builtins_are_live.

This was fixed by r11-86.

	PR c++/93614

gcc/testsuite/ChangeLog:

	* g++.dg/template/lookup18.C: New test.

Implements moste of OpenMP 5.1 atomic extensions,
except that 'compare' is parsed but rejected during
resolution. (As the trans-openmp.c handling is missing.)

gcc/fortran/ChangeLog:

	* dump-parse-tree.c (show_omp_clauses): Handle
	weak/compare/fail clause.
	* gfortran.h (gfc_omp_clauses): Add weak, compare, fail.
	* openmp.c (enum omp_mask1, gfc_match_omp_clauses,
	OMP_ATOMIC_CLAUSES): Update for new clauses.
	(gfc_match_omp_atomic): Update for 5.1 atomic changes.
	(is_conversion): Support widening in one go.
	(is_scalar_intrinsic_expr): New.
	(resolve_omp_atomic): Update for 5.1 atomic changes.
	* parse.c (parse_omp_oacc_atomic): Update for compare.
	* resolve.c (gfc_resolve_blocks): Update asserts.
	* trans-openmp.c (gfc_trans_omp_atomic): Handle new clauses.

gcc/testsuite/ChangeLog:

	* gfortran.dg/gomp/atomic-2.f90: Move now supported code to ...
	* gfortran.dg/gomp/atomic.f90: here.
	* gfortran.dg/gomp/atomic-10.f90: New test.
	* gfortran.dg/gomp/atomic-12.f90: New test.
	* gfortran.dg/gomp/atomic-15.f90: New test.
	* gfortran.dg/gomp/atomic-16.f90: New test.
	* gfortran.dg/gomp/atomic-17.f90: New test.
	* gfortran.dg/gomp/atomic-18.f90: New test.
	* gfortran.dg/gomp/atomic-19.f90: New test.
	* gfortran.dg/gomp/atomic-20.f90: New test.
	* gfortran.dg/gomp/atomic-22.f90: New test.
	* gfortran.dg/gomp/atomic-24.f90: New test.
	* gfortran.dg/gomp/atomic-25.f90: New test.
	* gfortran.dg/gomp/atomic-26.f90: New test.

libgomp/ChangeLog

	* libgomp.texi (OpenMP 5.1): Update status.

This fixes a -Wuninitialized warning for std::cmatch m1, m2; m1=m2;

Also name the template parameters in the forward declaration, to get rid
of the <template-parameter-1-1> noise in diagnostics.

libstdc++-v3/ChangeLog:

	PR libstdc++/103549
	* include/bits/regex.h (match_results): Give names to template
	parameters in first declaration.
	(match_results::_M_begin): Add default member-initializer.

libgomp/ChangeLog:

	* libgomp.texi (OMP_PLACES): Extend description for OMP 5.1 changes.

This patch fixes spelling of prefer (misspelled as preffer).

2021-12-04  Jakub Jelinek  <jakub@redhat.com>

	* config/i386/x86-tune.def (X86_TUNE_PARTIAL_REG_DEPENDENCY): Fix
	comment typo, Preffer -> prefer.
	* ipa-modref-tree.c (modref_access_node::closer_pair_p): Likewise.

P1272R4 has added to the std::byteswap new stuff to me quite unrelated
clarification for std::bit_cast.
The patch treats it as DR, applying to all languages.
We no longer diagnose if padding bits are stored into unsigned char
or std::byte result, fields or bitfields, instead arrange for that result,
those fields or bitfields to get indeterminate value (empty
CONSTRUCTOR with CONSTRUCTOR_NO_ZEROING or just leaving the member's
initializer out and setting CONSTRUCTOR_NO_ZEROING on parent).

We still have a bug that we don't diagnose in lots of places lvalue-to-rvalue
conversions of indeterminate values or class objects with some indeterminate
members.

2021-12-04  Jakub Jelinek <jakub@redhat.com>

	* cp-tree.h (is_byte_access_type_not_plain_char): Declare.
	* tree.c (is_byte_access_type_not_plain_char): New function.
	* constexpr.c (clear_uchar_or_std_byte_in_mask): New function.
	(cxx_eval_bit_cast): Don't error about padding bits if target
	type is unsigned char or std::byte, instead return no clearing
	ctor.  Use clear_uchar_or_std_byte_in_mask.

	* g++.dg/cpp2a/bit-cast11.C: New test.
	* g++.dg/cpp2a/bit-cast12.C: New test.
	* g++.dg/cpp2a/bit-cast13.C: New test.
	* g++.dg/cpp2a/bit-cast14.C: New test.

The https://gcc.gnu.org/pipermail/gcc-patches/2020-November/557903.html
change broke the following testcases.  The problem is when a pragma
namespace allows expansion (i.e. p->is_nspace && p->allow_expansion),
e.g. the omp or acc namespaces do, then when parsing the second pragma
token we do it with pfile->state.in_directive set,
pfile->state.prevent_expansion clear and pfile->state.in_deferred_pragma
clear (the last one because we don't know yet if it will be a deferred
pragma or not).  If the pragma line only contains a single name
and newline after it, and there exists a function-like macro with the
same name, the preprocessor needs to peek in funlike_invocation_p
the next token whether it isn't ( but in this case it will see a newline.
As pfile->state.in_directive is set, we don't read anything after the
newline, pfile->buffer->need_line is set and CPP_EOF is lexed, which
funlike_invocation_p doesn't push back.  Because name is a function-like
macro and on the pragma line there is no ( after the name, it isn't
expanded, and control flow returns to do_pragma.  If name is valid
deferred pragma, we set pfile->state.in_deferred_pragma (and really
need it set so that e.g. end_directive later on doesn't eat all the
tokens from the pragma line).

Before Nathan's change (which unfortunately didn't contain rationale
on why it is better to do it like that), this wasn't a problem,
next _cpp_lex_direct called when we want next token would return
CPP_PRAGMA_EOF when it saw buffer->need_line, which would turn off
pfile->state.in_deferred_pragma and following get token would already
read the next line.  But Nathan's patch replaced it with an assertion
failure that now triggers and CPP_PRAGMA_EOL is done only when lexing
the '\n'.  Except for this special case that works fine, but in
this case it doesn't because when peeking the token we still didn't know
that it will be a deferred pragma.
I've tried to fix that up in do_pragma by detecting this and pushing
CPP_PRAGMA_EOL as lookahead, but that doesn't work because end_directive
still needs to see pfile->state.in_deferred_pragma set.

So, this patch affectively reverts part of Nathan's change, CPP_PRAGMA_EOL
addition isn't done only when parsing the '\n', but is now done in both
places, in the first one instead of the assertion failure.

2021-12-04  Jakub Jelinek  <jakub@redhat.com>

	PR preprocessor/102432
	* lex.c (_cpp_lex_direct): If buffer->need_line while
	pfile->state.in_deferred_pragma, return CPP_PRAGMA_EOL token instead
	of assertion failure.

	* c-c++-common/gomp/pr102432.c: New test.
	* c-c++-common/goacc/pr102432.c: New test.

When -fif-conversion2 is enabled, we attempt to replace conditional
branches around unconditional traps with conditional traps.  That
canonicalizes compares, which may change an immediate that barely fits
into one that doesn't.

The compare for the trap is first checked using the predicates of
cbranch predicates, and then, compare and conditional trap insns are
emitted and recognized.

In the failing s390x testcase, i <=u 0xffff_ffff is canonicalized into
i <u 0x1_0000_0000, and the latter immediate doesn't fit.  The insn
predicates (both cbranch and cmpdi_ccu) happily accept it, since the
register allocator has no trouble getting them into registers.  The
problem is that ifcvt2 runs after reload, so we recognize the compare
insn successfully, but later on we barf when we find that none of the
constraints fit.

This patch arranges for the trap_if-issuing bits in ifcvt to validate
post-reload insns using a stricter test that also checks that operands
fit the constraints.


for  gcc/ChangeLog

	PR rtl-optimization/103028
	* ifcvt.c (find_cond_trap): Validate new insns more strictly
	after reload.

for  gcc/testsuite/ChangeLog

	PR rtl-optimization/103028
	* gcc.dg/pr103028.c: New.

vector long long int and vector double require VSX not just Altivec.

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/vec_reve_1.c: Require VSX.

This introduces a new RAII type to simplify the emplace members which
currently use try-catch blocks to deallocate a node if an exception is
thrown by the comparisons done during insertion. The new type is created
on the stack and manages the allocation of a new node and deallocates it
in the destructor if it wasn't inserted into the tree. It also provides
helper functions for doing the insertion, releasing ownership of the
node to the tree.

Also, we don't need to use long qualified names if we put the return
type after the nested-name-specifier.

libstdc++-v3/ChangeLog:

	* include/bits/stl_tree.h (_Rb_tree::_Auto_node): Define new
	RAII helper for creating and inserting new nodes.
	(_Rb_tree::_M_insert_node): Use trailing-return-type to simplify
	out-of-line definition.
	(_Rb_tree::_M_insert_lower_node): Likewise.
	(_Rb_tree::_M_insert_equal_lower_node): Likewise.
	(_Rb_tree::_M_emplace_unique): Likewise. Use _Auto_node.
	(_Rb_tree::_M_emplace_equal): Likewise.
	(_Rb_tree::_M_emplace_hint_unique): Likewise.
	(_Rb_tree::_M_emplace_hint_equal): Likewise.

We can make some function signatures shorter to print by omitting redundant
nested-name-specifiers in the rest of the declarator.

gcc/cp/ChangeLog:

	* error.c (current_dump_scope): New variable.
	(dump_scope): Check it.
	(dump_function_decl): Set it.

gcc/testsuite/ChangeLog:

	* g++.dg/diagnostic/scope1.C: New test.

PR101324 shows a problem in disabling shrink-wrapping when using -mrop-protect
when there is a attribute optimize/pragma.  The fix envolves moving the handling
of flag_shrink_wrap so it gets re-disbled when we change or add options.

2021-12-03  Martin Liska  <mliska@suse.cz>

gcc/
	PR target/101324
	* config/rs6000/rs6000.c (rs6000_option_override_internal): Move the
	disabling of shrink-wrapping when using -mrop-protect from here...
	(rs6000_override_options_after_change): ...to here.

2021-12-03  Peter Bergner  <bergner@linux.ibm.com>

gcc/testsuite/
	PR target/101324
	* gcc.target/powerpc/pr101324.c: New test.

This patch adds a new effective-target function that tests whether
it is safe to emit the ROP-protect instructions and updates the
ROP test cases to use it.

2021-12-03  Peter Bergner  <bergner@linux.ibm.com>

gcc/testsuite/
	* lib/target-supports.exp (check_effective_target_rop_ok): New function.
	* gcc.target/powerpc/rop-1.c: Use it.
	* gcc.target/powerpc/rop-2.c: Likewise.
	* gcc.target/powerpc/rop-3.c: Likewise.
	* gcc.target/powerpc/rop-4.c: Likewise.
	* gcc.target/powerpc/rop-5.c: Likewise.

gcc/fortran/ChangeLog:

	PR fortran/103505
	* array.c (match_array_element_spec): Try to simplify array
	element specifications to improve early checking.
	* expr.c (gfc_try_simplify_expr): New.  Try simplification of an
	expression via gfc_simplify_expr.  When an error occurs, roll
	back.
	* gfortran.h (gfc_try_simplify_expr): Declare it.

gcc/testsuite/ChangeLog:

	PR fortran/103505
	* gfortran.dg/pr103505.f90: New test.

Co-authored-by: Steven G. Kargl <kargl@gcc.gnu.org>

In r11-4758, I tried to fix this problem:

  int &&i = 0;
  decltype(auto) j = i; // should behave like int &&j = i; error

wherein do_auto_deduction was getting confused with a REFERENCE_REF_P
and it didn't realize its operand was a name, not an expression, and
deduced the wrong type.

Unfortunately that fix broke this:

  int&& r = 1;
  decltype(auto) rr = (r);

where 'rr' should be 'int &' since '(r)' is an expression, not a name.  But
because I stripped the INDIRECT_REF with the r11-4758 change, we deduced
'rr's type as if decltype had gotten a name, resulting in 'int &&'.

I suspect I thought that the REF_PARENTHESIZED_P check when setting
'bool id' in do_auto_deduction would handle the (r) case, but that's not
the case; while the documentation for REF_PARENTHESIZED_P specifically says
it can be set in INDIRECT_REF, we don't actually do so.

This patch sets REF_PARENTHESIZED_P even on REFERENCE_REF_P, so that
do_auto_deduction can use it.

It also removes code in maybe_undo_parenthesized_ref that I think is
dead -- and we don't hit it while running dg.exp.  To adduce more data,
it also looks dead here:
https://splichal.eu/lcov/gcc/cp/semantics.c.gcov.html
(It's dead since r9-1417.)

Also add a fixed test for c++/81176.

	PR c++/103403

gcc/cp/ChangeLog:

	* cp-gimplify.c (cp_fold): Don't recurse if maybe_undo_parenthesized_ref
	doesn't change its argument.
	* pt.c (do_auto_deduction): Don't strip REFERENCE_REF_P trees if they
	are REF_PARENTHESIZED_P.  Use stripped_init when checking for
	id-expression.
	* semantics.c (force_paren_expr): Set REF_PARENTHESIZED_P on
	REFERENCE_REF_P trees too.
	(maybe_undo_parenthesized_ref): Remove dead code.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp1y/decltype-auto2.C: New test.
	* g++.dg/cpp1y/decltype-auto3.C: New test.
	* g++.dg/cpp1y/decltype-auto4.C: New test.
	* g++.dg/cpp1z/decomp-decltype1.C: New test.