Eric Botcazou [Wed, 30 Apr 2025 10:41:36 +0000 (12:41 +0200)]
Fix GNAT build failure for x86/FreeBSD
gcc/ada/
PR ada/112958
* Makefile.rtl (LIBGNAT_TARGET_PAIRS) [x86 FreeBSD]: Add specific
version of s-dorepr.adb.
* libgnat/s-dorepr__freebsd.adb: New file.
AVR: target/119989 - Add missing clobbers to xload_<mode>_libgcc.
libgcc's __xload_1...4 is clobbering Z (and also R21 is some cases),
but avr.md had clobbers of respective GPRs only up to reload.
Outcome was that code reading from the same __memx address twice
could be wrong. This patch adds respective clobbers.
Backport from 2025-04-30 r14-11703
PR target/119989
gcc/
* config/avr/avr.md (xload_<mode>_libgcc): Clobber R21, Z.
gcc/testsuite/
* gcc.target/avr/torture/pr119989.h: New file.
* gcc.target/avr/torture/pr119989-memx-1.c: New test.
* gcc.target/avr/torture/pr119989-memx-2.c: New test.
* gcc.target/avr/torture/pr119989-memx-3.c: New test.
* gcc.target/avr/torture/pr119989-memx-4.c: New test.
Avoid using POINTER_DIFF_EXPR for overlap checks [PR119399]
In r10-4803-g8489e1f45b50600c I'd used POINTER_DIFF_EXPR to subtract
the two pointers involved in an overlap test. I'm not sure whether
I'd specifically chosen that over MINUS_EXPR or not; if so, the only
reason I can think of is that it is probably faster on targets with
PSImode pointers. Regardless, as the PR points out, subtracting
unrelated pointers using POINTER_DIFF_EXPR is undefined behaviour.
gcc/
PR tree-optimization/119399
* tree-data-ref.cc (create_waw_or_war_checks): Use a MINUS_EXPR
on two converted pointers, rather than converting a POINTER_DIFF_EXPR
on the pointers.
gcc/testsuite/
PR tree-optimization/119399
* gcc.dg/vect/pr119399.c: New test.
tree-data-refs.cc uses alignment information to try to optimise
the code generated for alias checks. The assumption for "normal"
non-grouped, full-width scalar accesses was that the access size
would be a multiple of the alignment. As Richi notes in the PR,
this is a documented precondition of dr_with_seg_len:
/* The minimum common alignment of DR's start address, SEG_LEN and
ACCESS_SIZE. */
unsigned int align;
PR115192 was a case in which this assumption didn't hold. The access
was part of an aligned 4-element group, but only the first 2 elements
of the group were accessed. The alignment was therefore double the
access size.
In r15-820-ga0fe4fb1c8d78045 I'd "fixed" that by capping the
alignment in one of the output routines. But I think that was
misconceived. The precondition means that we should cap the
alignment at source instead.
Failure to do that caused a similar wrong code bug in this PR,
where the alignment comes from a short bitfield access rather
than from a group access.
gcc/
PR tree-optimization/116125
* tree-vect-data-refs.cc (vect_prune_runtime_alias_test_list): Make
the dr_with_seg_len alignment fields describe tha access sizes as
well as the pointer alignment.
* tree-data-ref.cc (create_intersect_range_checks): Don't compensate
for invalid alignment fields here.
gcc/testsuite/
PR tree-optimization/116125
* gcc.dg/vect/pr116125.c: New test.
Since r12-5426 apply_late_template_attributes suppresses various global
state to avoid applying active pragmas to earlier declarations; we also
need to override target_option_current_node.
PR c++/114772
PR c++/101180
gcc/cp/ChangeLog:
* pt.cc (apply_late_template_attributes): Also override
target_option_current_node.
Harald Anlauf [Tue, 8 Apr 2025 20:30:15 +0000 (22:30 +0200)]
Fortran: fix issue with impure elemental subroutine and interface [PR119656]
PR fortran/119656
gcc/fortran/ChangeLog:
* interface.cc (gfc_compare_actual_formal): Fix front-end memleak
when searching for matching interfaces.
* trans-expr.cc (gfc_conv_procedure_call): If there is a formal
dummy corresponding to an absent argument, use its type, and only
fall back to inferred type otherwise.
d: Fix ICE in dwarf2out_imported_module_or_decl, at dwarf2out.cc:27676 [PR119817]
The ImportVisitor method for handling the importing of overload sets was
pushing NULL_TREE to the array of import decls, which in turn got passed
to `debug_hooks->imported_module_or_decl', triggering the observed
internal compiler error.
NULL_TREE is returned from `build_import_decl' when the symbol was
ignored for being non-trivial to represent in debug, for example,
template or tuple declarations. So similarly "skip" adding the symbol
when this is the case for overload sets too.
PR d/119817
gcc/d/ChangeLog:
* imports.cc (ImportVisitor::visit (OverloadSet *)): Don't push
NULL_TREE to vector of import symbols.
gcc/testsuite/ChangeLog:
* gdc.dg/debug/imports/m119817/a.d: New test.
* gdc.dg/debug/imports/m119817/b.d: New test.
* gdc.dg/debug/imports/m119817/package.d: New test.
* gdc.dg/debug/pr119817.d: New test.
Jonathan Wakely [Fri, 23 Jun 2023 12:50:01 +0000 (13:50 +0100)]
libstdc++: Qualify calls to debug mode helpers
These functions should be qualified to disable unwanted ADL.
The overload of __check_singular_aux for safe iterators was previously
being found by ADL, because it wasn't declared before __check_singular.
Add a declaration so that it can be found by qualified lookup.
libstdc++-v3/ChangeLog:
* include/debug/helper_functions.h (__get_distance)
(__check_singular, __valid_range_aux, __valid_range): Qualify
calls to disable ADL.
(__check_singular_aux(const _Safe_iterator_base*)): Declare
overload that was previously found via ADL.
Jonathan Wakely [Thu, 4 Apr 2024 09:33:33 +0000 (10:33 +0100)]
libstdc++: Fix infinite loop in std::istream::ignore(n, delim) [PR93672]
A negative delim value passed to std::istream::ignore can never match
any character in the stream, because the comparison is done using
traits_type::eq_int_type(sb->sgetc(), delim) and sgetc() never returns
negative values (except at EOF). The optimized version of ignore for the
std::istream specialization uses traits_type::find to locate the delim
character in the streambuf, which _can_ match a negative delim on
platforms where char is signed, but then we do another comparison using
eq_int_type which fails. The code then keeps looping forever, with
traits_type::find locating the character and traits_type::eq_int_type
saying it's not a match, so traits_type::find is used again and finds
the same character again.
A possible fix would be to check with eq_int_type after a successful
find, to see whether we really have a match. However, that would be
suboptimal since we know that a negative delimiter will never match
using eq_int_type. So a better fix is to adjust the check at the top of
the function that handles delim==eof(), so that we treat all negative
delim values as equivalent to EOF. That way we don't bother using find
to search for something that will never match with eq_int_type.
The version of ignore in the primary template doesn't need a change,
because it doesn't use traits_type::find, instead characters are
extracted one-by-one and always matched using eq_int_type. That avoids
the inconsistency between find and eq_int_type. The specialization for
std::wistream does use traits_type::find, but traits_type::to_int_type
is equivalent to an implicit conversion from wchar_t to wint_t, so
passing a wchar_t directly to ignore without using to_int_type works.
libstdc++-v3/ChangeLog:
PR libstdc++/93672
* src/c++98/istream.cc (istream::ignore(streamsize, int_type)):
Treat all negative delimiter values as eof().
* testsuite/27_io/basic_istream/ignore/char/93672.cc: New test.
* testsuite/27_io/basic_istream/ignore/wchar_t/93672.cc: New
test.
Jonathan Wakely [Fri, 28 Mar 2025 22:00:38 +0000 (22:00 +0000)]
libstdc++: Fix bogus -Wstringop-overflow in std::vector::insert [PR117983]
This was fixed on trunk by r15-4473-g3abe751ea86e34, but that isn't
suitable for backporting. Instead, just add another unreachable
condition in std::vector::_M_range_insert so the compiler knows this
memcpy doesn't use a length originating from a negative ptrdiff_t
converted to a very positive size_t.
libstdc++-v3/ChangeLog:
PR libstdc++/117983
* include/bits/vector.tcc (vector::_M_range_insert): Add
unreachable condition to tell the compiler begin() <= end().
* testsuite/23_containers/vector/modifiers/insert/117983.cc: New
test.
Inserting an empty range into a std::deque results in undefined calls to
either std::copy, std::copy_backward, std::move, or std::move_backward.
We call those algos with invalid arguments where the output range is the
same as the input range, e.g. std::copy(first, last, first) which
violates the preconditions for the algorithms.
This fix simply returns early if there's nothing to insert. Most callers
already ensure that we don't even call _M_range_insert_aux with an empty
range, but some callers don't. Rather than checking for n == 0 in each
of the callers, this just does the check once and uses __builtin_expect
to treat empty insertions as unlikely.
libstdc++-v3/ChangeLog:
PR libstdc++/118035
* include/bits/deque.tcc (_M_range_insert_aux): Return
immediately if inserting an empty range.
* testsuite/23_containers/deque/modifiers/insert/118035.cc: New
test.
Andrew Pinski [Mon, 14 Apr 2025 15:40:24 +0000 (08:40 -0700)]
testcase: Add testcase for already fixed PR [PR118476]
This testcase was fixed by r15-3052-gc7b76a076cb2c6ded but is
a testcase that failed in a different fashion and a much older
failure than the one added with r15-3052.
Andrew Pinski [Mon, 19 Aug 2024 15:06:36 +0000 (08:06 -0700)]
match: Reject non-ssa name/min invariants in gimple_extract [PR116412]
After the conversion for phiopt's conditional operand
to use maybe_push_res_to_seq, it was found that gimple_extract
will extract out from REALPART_EXPR/IMAGPART_EXPR/VCE and BIT_FIELD_REF,
a memory load. But that extraction was not needed as memory loads are not
simplified in match and simplify. So gimple_extract should return false
in those cases.
Changes since v1:
* Move the rejection to gimple_extract from factor_out_conditional_operation.
GCC13: the function is in gimple-match-head.cc rather than gimple-match-exports.cc.
Bootstrapped and tested on x86_64-linux-gnu.
PR tree-optimization/116412
gcc/ChangeLog:
* gimple-match-head.cc (gimple_extract): Return false if op0
was not a SSA name nor a min invariant for REALPART_EXPR/IMAGPART_EXPR/VCE
and BIT_FIELD_REF.
Andrew Pinski [Sun, 9 Mar 2025 06:43:54 +0000 (22:43 -0800)]
phiopt: Fix value_replacement for middle bb having phi nodes [PR118922]
After r12-5300-gf98f373dd822b3, value_replacement would be able to look at the
following cfg structure:
```
<bb 5> [local count: 1014686024]:
if (h_6 != 0)
goto <bb 7>; [94.50%]
else
goto <bb 6>; [5.50%]
value_replacement would incorrectly think the middle bb (6) was empty and so it decides
to remove condition in bb5 and replacing it with 0 as the function thought it was `h_6 ? 0 : h_6`.
But since the there is an incoming phi node to bb6 defining h_6 that is incorrect.
The fix is to check if there is phi nodes in the middle bb and set empty_or_with_defined_p to false.
This was not needed before r12-5300-gf98f373dd822b3 because the phi would have been dead otherwise due to
other checks.
Bootstrapped and tested on x86_64-linux-gnu.
PR tree-optimization/118922
gcc/ChangeLog:
* tree-ssa-phiopt.cc (value_replacement): Set empty_or_with_defined_p
to false when there is phi nodes for the middle bb.
Andrew Pinski [Sun, 27 Oct 2024 20:16:22 +0000 (13:16 -0700)]
vec-lowering: Fix ABSU lowering [PR111285]
ABSU_EXPR lowering incorrectly used the resulting type
for the new expression but in the case of ABSU the resulting
type is an unsigned type and with ABSU is folded away. The fix
is to use a signed type for the expression instead.
Bootstrapped and tested on x86_64-linux-gnu.
PR middle-end/111285
gcc/ChangeLog:
* tree-vect-generic.cc (do_unop): Use a signed type for the
operand if the operation was ABSU_EXPR.
Andrew Pinski [Tue, 1 Oct 2024 21:48:19 +0000 (14:48 -0700)]
backprop: Fix deleting of a phi node [PR116922]
The problem here is remove_unused_var is called on a name that is
defined by a phi node but it deletes it like removing a normal statement.
remove_phi_node should be called rather than gsi_remove for phinodes.
Note there is a possibility of using simple_dce_from_worklist instead
but that is for another day.
Andrew Pinski [Mon, 2 Dec 2024 16:35:23 +0000 (08:35 -0800)]
phiopt: Reset the number of iterations information of a loop when changing an exit from the loop [PR117243]
After r12-5300-gf98f373dd822b3, phiopt could get the following bb structure:
|
middle-bb -----|
| |
| |----| |
phi<1, 2> | |
cond | |
| | |
|--------+---|
Which was considered 2 loops. The inner loop had esimtate of upper_bound to be 8,
due to the original `for (b = 0; b <= 7; b++)`. The outer loop was already an
infinite one.
So phiopt would come along and change the condition to be unconditionally true,
we change the inner loop to being an infinite one but don't reset the estimate
on the loop and cleanup cfg comes along and changes it into one loop but also
does not reset the estimate of the loop. Then the loop unrolling uses the old estimate
and decides to add an unreachable there.o
So the fix is when phiopt changes an exit to a loop, reset the estimates, similar to
how cleanupcfg does it when merging some basic blocks.
Jonathan Wakely [Wed, 16 Apr 2025 17:38:03 +0000 (18:38 +0100)]
libstdc++: Add dg-options "-std=gnu++20" to backported tests
These tests were backported from gcc-14 where the testsuite
automatically adds -std=gnu++20 as needed. That doesn't happen on the
older release branches, so an explicit dg-options directive is needed to
ensure the tests are run by default. Otherwise they'll only be run when
somebody uses a custom --target_board that includes -std=gnu++20.
For 29_atomics/headers/stdatomic.h/115807.cc we need to compile with
-std=gnu++23 instead.
Jonathan Wakely [Mon, 9 Dec 2024 17:35:24 +0000 (17:35 +0000)]
libstdc++: Skip redundant assertions in std::array equality [PR106212]
As PR c++/106212 shows, the Debug Mode checks cause a compilation error
for equality comparisons involving std::array prvalues in constant
expressions. Those Debug Mode checks are redundant when
comparing two std::array objects, because we already know we have a
valid range. We can also avoid the unnecessary step of using
std::__niter_base to do __normal_iterator unwrapping, which isn't needed
because our std::array iterators are just pointers. Using
std::__equal_aux1 instead of std::equal avoids the redundant checks in
std::equal and std::__equal_aux.
libstdc++-v3/ChangeLog:
PR libstdc++/106212
* include/std/array (operator==): Use std::__equal_aux1 instead
of std::equal.
* testsuite/23_containers/array/comparison_operators/106212.cc:
New test.
Jonathan Wakely [Mon, 9 Dec 2024 17:35:24 +0000 (17:35 +0000)]
libstdc++: Skip redundant assertions in std::span construction [PR117966]
As PR c++/117966 shows, the Debug Mode checks cause a compilation error
for a global constexpr std::span. Those debug checks are redundant when
constructing from an array or a range, because we already know we have a
valid range and we know its size. Instead of delegating to the
std::span(contiguous_iterator, contiguous_iterator) constructor, just
initialize the data members directly.
libstdc++-v3/ChangeLog:
PR libstdc++/117966
* include/std/span (span(T (&)[N])): Do not delegate to
constructor that performs redundant checks.
(span(array<T, N>&), span(const array<T, N>&)): Likewise.
(span(Range&&), span(const span<T, N>&)): Likewise.
* testsuite/23_containers/span/117966.cc: New test.
This is needed to avoid errors outside the immediate context when
evaluating is_default_constructible_v<vector<T, A>> when A is not
default constructible.
To avoid diagnostic regressions for 23_containers/vector/48101_neg.cc we
need to make the std::allocator<cv T> partial specializations default
constructible, which they probably should have been anyway.
libstdc++-v3/ChangeLog:
PR libstdc++/113841
* include/bits/allocator.h (allocator<cv T>): Add default
constructor to partial specializations for cv-qualified types.
* include/bits/stl_vector.h (_Vector_impl::_Vector_impl()):
Constrain so that it's only present if the allocator is default
constructible.
* include/bits/stl_bvector.h (_Bvector_impl::_Bvector_impl()):
Likewise.
* testsuite/23_containers/vector/cons/113841.cc: New test.
Jonathan Wakely [Mon, 2 Sep 2024 10:29:13 +0000 (11:29 +0100)]
libstdc++: Specialize std::disable_sized_sentinel_for for std::move_iterator [PR116549]
LWG 3736 added a partial specialization of this variable template for
two std::move_iterator types. This is needed for the case where the
types satisfy std::sentinel_for and are subtractable, but do not model
the semantics requirements of std::sized_sentinel_for.
libstdc++-v3/ChangeLog:
PR libstdc++/116549
* include/bits/stl_iterator.h (disable_sized_sentinel_for):
Define specialization for two move_iterator types, as per LWG
3736.
* testsuite/24_iterators/move_iterator/lwg3736.cc: New test.
Jonathan Wakely [Thu, 14 Nov 2024 01:14:44 +0000 (01:14 +0000)]
libstdc++: Add missing parts of LWG 3480 for directory iterators [PR117560]
It looks like I only read half the resolution of LWG 3480 and decided we
already supported it. As well as making the non-member overloads of end
take their parameters by value, we need some specializations of the
enable_borrowed_range and enable_view variable templates.
libstdc++-v3/ChangeLog:
PR libstdc++/117560
* include/bits/fs_dir.h (enable_borrowed_range, enable_view):
Define specializations for directory iterators, as per LWG 3480.
* testsuite/27_io/filesystem/iterators/lwg3480.cc: New test.
Jonathan Wakely [Fri, 11 Apr 2025 10:08:34 +0000 (11:08 +0100)]
libstdc++: Document thread-safety for COW std::string [PR21334]
The gcc4-compatible copy-on-write std::string does not conform to the
C++11 requirements on data race avoidance in standard containers.
Specifically, calling non-const member functions such as begin() and
data() needs to do the "copy on write" operation and so is most
definitely a modification of the object. As such, those non-const
members must not be called concurrently with any other uses of the
string object.
libstdc++-v3/ChangeLog:
PR libstdc++/21334
* doc/xml/manual/using.xml: Document that container data race
avoidance rules do not apply to COW std::string.
* doc/html/*: Regenerate.
Richard Biener [Wed, 9 Apr 2025 12:36:19 +0000 (14:36 +0200)]
rtl-optimization/119689 - compare-debug failure with LRA
The previous change to fix LRA rematerialization broke compare-debug
for i586 bootstrap. Fixed by using prev_nonnote_nondebug_insn
instead of prev_nonnote_insn.
PR rtl-optimization/119689
PR rtl-optimization/115568
* lra-remat.cc (create_cands): Use prev_nonnote_nondebug_insn
to check whether insn2 is directly before insn.
[PR115568][LRA]: Use more strict output reload check in rematerialization
In this PR case LRA rematerialized a value from inheritance insn
instead of output reload one. This resulted in considering a
rematerilization candidate value available when it was actually
not. As a consequence an insn after rematerliazation used the
unexpected value and this use resulted in fp exception. The patch
fixes this bug.
gcc/ChangeLog:
PR rtl-optimization/115568
* lra-remat.cc (create_cands): Check that output reload insn is
adjacent to given insn. Update a comment.
Richard Biener [Thu, 18 Jul 2024 11:35:33 +0000 (13:35 +0200)]
middle-end/115641 - invalid address construction
fold_truth_andor_1 via make_bit_field_ref builds an address of
a CALL_EXPR which isn't valid GENERIC and later causes an ICE.
The following simply avoids the folding for f ().a != 1 || f ().b != 2
as it is a premature optimization anyway. The alternative would
have been to build a TARGET_EXPR around the call. To get this far
f () has to be const as otherwise the two calls are not semantically
equivalent for the optimization.
PR middle-end/115641
* fold-const.cc (decode_field_reference): If the inner
reference isn't something we can take the address of, fail.
Richard Biener [Sun, 13 Oct 2024 09:42:27 +0000 (11:42 +0200)]
tree-optimization/116481 - avoid building function_type[]
The following avoids building an array type with function or method
element type during diagnosing an array bound violation as this
will result in an error, rejecting a program with a not too useful
error message. Instead build such array type manually.
PR tree-optimization/116481
* pointer-query.cc (build_printable_array_type):
Build an array types with function or method element type
manually to avoid bogus diagnostic.
Richard Biener [Thu, 26 Sep 2024 13:41:59 +0000 (15:41 +0200)]
tree-optimization/116850 - corrupt post-dom info
Path isolation computes post-dominators on demand but can end up
splitting blocks after that, wrecking it. We can delay splitting
of blocks until we no longer need the post-dom info which is what
the following patch does to solve the issue.
PR tree-optimization/116850
* gimple-ssa-isolate-paths.cc (bb_split_points): New global.
(insert_trap): Delay BB splitting if post-doms are computed.
(find_explicit_erroneous_behavior): Process delayed BB
splitting after releasing post dominators.
(gimple_ssa_isolate_erroneous_paths): Do not free post-dom
info here.
Richard Biener [Fri, 15 Nov 2024 10:56:14 +0000 (11:56 +0100)]
tree-optimization/117574 - bougs niter lt-to-ne
When trying to change a IV from IV0 < IV1 to IV0' != IV1' we apply
fancy adjustments to the may_be_zero condition we compute rather
than using the obvious IV0->base >= IV1->base expression (to be
able to use > instead of >=?). This doesn't seem to go well.
PR tree-optimization/117574
* tree-ssa-loop-niter.cc (number_of_iterations_lt_to_ne):
Use the obvious may_be_zero condition.
Richard Biener [Thu, 5 Dec 2024 09:47:13 +0000 (10:47 +0100)]
tree-optimization/117912 - bogus address equivalences for __builtin_object_size
VN again is the culprit for exploiting address equivalences before
__builtin_object_size got the chance to do its job. This time
it isn't about union members but adjacent structure fields where
an address to one after the last element of an array field can
spill over to the next field.
The following protects all out-of-bound accesses on the upper bound
side (singling out TYPE_MAX_VALUE + 1 is more expensive). It
ignores other out-of-bound addresses that would invoke UB.
Zero-sized arrays are a bit awkward because the C++ represents them
with a -1U upper bound.
There's a similar issue for zero-sized components whose address can
be the same as the adjacent field in C.
PR tree-optimization/117912
* tree-ssa-sccvn.cc (copy_reference_ops_from_ref): For addresses
of zero-sized components do not set ->off if the object size pass
didn't run.
For OOB ARRAY_REF accesses in address expressions avoid setting
->off if the object size pass didn't run.
(valueize_refs_1): Likewise.
* c-c++-common/torture/pr117912-1.c: New testcase.
* c-c++-common/torture/pr117912-2.c: Likewise.
* c-c++-common/torture/pr117912-3.c: Likewise.
Richard Biener [Mon, 3 Feb 2025 08:55:50 +0000 (09:55 +0100)]
tree-optimization/118717 - store commoning vs. abnormals
When we sink common stores in cselim or the sink pass we have to
make sure to not introduce overlapping lifetimes for abnormals
used in the ref. The easiest is to avoid sinking stmts which
reference abnormals at all which is what the following does.
PR tree-optimization/118717
* tree-ssa-phiopt.cc (cond_if_else_store_replacement_1):
Do not common stores referencing abnormal SSA names.
* tree-ssa-sink.cc (sink_common_stores_to_bb): Likewise.
Eric Botcazou [Fri, 4 Apr 2025 09:45:23 +0000 (11:45 +0200)]
Ada: Fix thinko in Eigensystem for complex Hermitian matrices
The implementation solves the eigensystem for a NxN complex Hermitian matrix
by first solving it for a 2Nx2N real symmetric matrix and then interpreting
the 2Nx1 real vectors as Nx1 complex ones, but the last step does not work.
The patch fixes the last step and also performs a small cleanup throughout
the implementation, mostly in the commentary and without functional changes.
gcc/ada/
* libgnat/a-ngcoar.adb (Eigensystem): Adjust notation and fix the
layout of the real symmetric matrix in the main comment. Adjust
the layout of the associated code accordingly and correctly turn
the 2Nx1 real vectors into Nx1 complex ones.
(Eigenvalues): Minor similar tweaks.
* libgnat/a-ngrear.adb (Jacobi): Minor tweaks in the main comment.
Adjust notation and corresponding parameter names of functions.
Fix call to Unit_Matrix routine. Adjust the comment describing
the various kinds of iterations to match the implementation.
Jonathan Wakely [Fri, 31 Mar 2023 12:44:04 +0000 (13:44 +0100)]
libstdc++: Teach optimizer that empty COW strings are empty [PR107087]
The compiler doesn't know about the invariant that the _S_empty_rep()
object is immutable and so _M_length and _M_refcount are always zero.
This means that we get warnings about writing possibly-non-zero length
strings into buffers that can't hold them. If we teach the compiler that
the empty rep is always zero length, it knows it can be copied into any
buffer.
For Stage 1 we might want to also consider adding this to capacity():
if (_S_empty_rep()._M_capacity != 0)
__builtin_unreachable();
And this to _Rep::_M_is_leaked() and _Rep::_M_is_shared():
if (_S_empty_rep()._M_refcount != 0)
__builtin_unreachable();
libstdc++-v3/ChangeLog:
PR tree-optimization/107087
* include/bits/cow_string.h (basic_string::size()): Add
optimizer hint that _S_empty_rep()._M_length is always zero.
(basic_string::length()): Call size().
Jonathan Wakely [Thu, 8 Feb 2024 13:59:42 +0000 (13:59 +0000)]
libstdc++: Avoid aliasing violation in std::valarray [PR99117]
The call to __valarray_copy constructs an _Array object to refer to
this->_M_data but that means that accesses to this->_M_data are through
a restrict-qualified pointer. This leads to undefined behaviour when
copying from an _Expr object that actually aliases this->_M_data.
Replace the call to __valarray_copy with a plain loop. I think this
removes the only use of that overload of __valarray_copy, so it could
probably be removed. I haven't done that here.
libstdc++-v3/ChangeLog:
PR libstdc++/99117
* include/std/valarray (valarray::operator=(const _Expr&)):
Use loop to copy instead of __valarray_copy with _Array.
* testsuite/26_numerics/valarray/99117.cc: New test.
Iain Buclaw [Tue, 11 Mar 2025 16:56:18 +0000 (17:56 +0100)]
d: Fix regression returning from function with invariants [PR119139]
An optimization was added in GDC-12 which sets the TREE_READONLY flag on
all local variables with the storage class `const' assigned. For some
reason, const is also being added by the front-end to `__result'
variables in non-virtual functions, which ends up getting wrong code by
the gimplify pass promoting the local to static storage.
A bug has been raised upstream, as this looks like an error in the AST.
For now, turn off setting TREE_READONLY on all result variables.
PR d/119139
gcc/d/ChangeLog:
* decl.cc (get_symbol_decl): Don't set TREE_READONLY for __result
declarations.
Fix folding of BIT_NOT_EXPR for POLY_INT_CST [PR118976]
There was an embarrassing typo in the folding of BIT_NOT_EXPR for
POLY_INT_CSTs: it used - rather than ~ on the poly_int. Not sure
how that happened, but it might have been due to the way that
~x is implemented as -1 - x internally.
gcc/
PR tree-optimization/118976
* fold-const.cc (const_unop): Use ~ rather than - for BIT_NOT_EXPR.
* config/aarch64/aarch64.cc (aarch64_test_sve_folding): New function.
(aarch64_run_selftests): Run it.
aarch64: Fix folding of degenerate svwhilele case [PR117045]
The svwhilele folder mishandled the degenerate case in which
the second argument is the maximum integer. In that case,
the result is all-true regardless of the first parameter:
If the second scalar operand is equal to the maximum signed integer
value then a condition which includes an equality test can never fail
and the result will be an all-true predicate.
This is because the conceptual "increment the first operand
by 1 after each element" is done modulo the range of the operand.
The GCC code was instead treating it as infinite precision.
whilele_5.c even had a test for the incorrect behaviour.
The easiest fix seemed to be to handle that case specially before
doing constant folding. This also copes with variable first operands.
gcc/
PR target/116999
PR target/117045
* config/aarch64/aarch64-sve-builtins-base.cc
(svwhilelx_impl::fold): Check for WHILELTs of the minimum value
and WHILELEs of the maximum value. Fold them to all-false and
all-true respectively.
The testcase contains a VNx2QImode pseudo that is live across a call
and that cannot be allocated a call-preserved register. LRA quite
reasonably tried to save it before the call and restore it afterwards.
Unfortunately, the target told it to do that in SImode, even though
punning between SImode and VNx2QImode is disallowed by both
TARGET_CAN_CHANGE_MODE_CLASS and TARGET_MODES_TIEABLE_P.
The natural class to use for SImode is GENERAL_REGS, so this led
to an unsalvageable situation in which we had:
(set (subreg:VNx2QI (reg:SI A) 0) (reg:VNx2QI B))
where A needed GENERAL_REGS and B needed FP_REGS. We therefore ended
up in a reload loop.
The hooks above should ensure that this situation can never occur
for incoming subregs. It only happened here because the target
explicitly forced it.
The decision to use SImode for modes smaller than 4 bytes dates
back to the beginning of the port, before 16-bit floating-point
modes existed. I'm not sure whether promoting to SImode really
makes sense for any FPR, but that's a separate performance/QoI
discussion. For now, this patch just disallows using SImode
when it is wrong for correctness reasons, since that should be
safer to backport.
gcc/
PR testsuite/116238
* config/aarch64/aarch64.cc (aarch64_hard_regno_caller_save_mode):
Only return SImode if we can convert to and from it.
gcc/testsuite/
PR testsuite/116238
* gcc.target/aarch64/sve/pr116238.c: New test.
Christophe Lyon [Mon, 3 Mar 2025 11:12:18 +0000 (11:12 +0000)]
arm: Handle fixed PIC register in require_pic_register (PR target/115485)
Commit r9-4307-g89d7557202d25a forgot to accept a fixed PIC register
when extending the assert in require_pic_register.
arm_pic_register can be set explicitly by the user
(e.g. -mpic-register=r9) or implicitly as the default value with
-fpic/-fPIC/-fPIE and -mno-pic-data-is-text-relative -mlong-calls, and
we want to use/accept it when recording cfun->machine->pic_reg as used
to be the case.
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