On Mon, Jun 24, 2019 at 1:08 AM Ian Lance Taylor <i...@golang.org> wrote:
>
> On Fri, Jun 7, 2019 at 5:04 AM Martin Liška <mli...@suse.cz> wrote:
> >
> > On 6/7/19 10:57 AM, Richard Biener wrote:
> > > On Mon, Jun 3, 2019 at 3:35 PM Martin Liška <mli...@suse.cz> wrote:
> > >>
> > >> On 6/1/19 12:06 AM, Jeff Law wrote:
> > >>> On 5/22/19 3:13 AM, Martin Liška wrote:
> > >>>> On 5/21/19 1:51 PM, Richard Biener wrote:
> > >>>>> On Tue, May 21, 2019 at 1:02 PM Martin Liška <mli...@suse.cz> wrote:
> > >>>>>>
> > >>>>>> On 5/21/19 11:38 AM, Richard Biener wrote:
> > >>>>>>> On Tue, May 21, 2019 at 12:07 AM Jeff Law <l...@redhat.com> wrote:
> > >>>>>>>>
> > >>>>>>>> On 5/13/19 1:41 AM, Martin Liška wrote:
> > >>>>>>>>> On 11/8/18 9:56 AM, Martin Liška wrote:
> > >>>>>>>>>> On 11/7/18 11:23 PM, Jeff Law wrote:
> > >>>>>>>>>>> On 10/30/18 6:28 AM, Martin Liška wrote:
> > >>>>>>>>>>>> On 10/30/18 11:03 AM, Jakub Jelinek wrote:
> > >>>>>>>>>>>>> On Mon, Oct 29, 2018 at 04:14:21PM +0100, Martin Liška wrote:
> > >>>>>>>>>>>>>> +hashtab_chk_error ()
> > >>>>>>>>>>>>>> +{
> > >>>>>>>>>>>>>> + fprintf (stderr, "hash table checking failed: "
> > >>>>>>>>>>>>>> + "equal operator returns true for a pair "
> > >>>>>>>>>>>>>> + "of values with a different hash value");
> > >>>>>>>>>>>>> BTW, either use internal_error here, or at least if using
> > >>>>>>>>>>>>> fprintf
> > >>>>>>>>>>>>> terminate with \n, in your recent mail I saw:
> > >>>>>>>>>>>>> ...different hash valueduring RTL pass: vartrack
> > >>>>>>>>>>>>> ^^^^^^
> > >>>>>>>>>>>> Sure, fixed in attached patch.
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> Martin
> > >>>>>>>>>>>>
> > >>>>>>>>>>>>>> + gcc_unreachable ();
> > >>>>>>>>>>>>>> +}
> > >>>>>>>>>>>>> Jakub
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>> 0001-Sanitize-equals-and-hash-functions-in-hash-tables.patch
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> From 0d9c979c845580a98767b83c099053d36eb49bb9 Mon Sep 17
> > >>>>>>>>>>>> 00:00:00 2001
> > >>>>>>>>>>>> From: marxin <mli...@suse.cz>
> > >>>>>>>>>>>> Date: Mon, 29 Oct 2018 09:38:21 +0100
> > >>>>>>>>>>>> Subject: [PATCH] Sanitize equals and hash functions in
> > >>>>>>>>>>>> hash-tables.
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> ---
> > >>>>>>>>>>>> gcc/hash-table.h | 40 +++++++++++++++++++++++++++++++++++++++-
> > >>>>>>>>>>>> 1 file changed, 39 insertions(+), 1 deletion(-)
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> diff --git a/gcc/hash-table.h b/gcc/hash-table.h
> > >>>>>>>>>>>> index bd83345c7b8..694eedfc4be 100644
> > >>>>>>>>>>>> --- a/gcc/hash-table.h
> > >>>>>>>>>>>> +++ b/gcc/hash-table.h
> > >>>>>>>>>>>> @@ -503,6 +503,7 @@ private:
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> value_type *alloc_entries (size_t n CXX_MEM_STAT_INFO)
> > >>>>>>>>>>>> const;
> > >>>>>>>>>>>> value_type *find_empty_slot_for_expand (hashval_t);
> > >>>>>>>>>>>> + void verify (const compare_type &comparable, hashval_t
> > >>>>>>>>>>>> hash);
> > >>>>>>>>>>>> bool too_empty_p (unsigned int);
> > >>>>>>>>>>>> void expand ();
> > >>>>>>>>>>>> static bool is_deleted (value_type &v)
> > >>>>>>>>>>>> @@ -882,8 +883,12 @@ hash_table<Descriptor, Allocator>
> > >>>>>>>>>>>> if (insert == INSERT && m_size * 3 <= m_n_elements * 4)
> > >>>>>>>>>>>> expand ();
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> - m_searches++;
> > >>>>>>>>>>>> +#if ENABLE_EXTRA_CHECKING
> > >>>>>>>>>>>> + if (insert == INSERT)
> > >>>>>>>>>>>> + verify (comparable, hash);
> > >>>>>>>>>>>> +#endif
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> + m_searches++;
> > >>>>>>>>>>>> value_type *first_deleted_slot = NULL;
> > >>>>>>>>>>>> hashval_t index = hash_table_mod1 (hash,
> > >>>>>>>>>>>> m_size_prime_index);
> > >>>>>>>>>>>> hashval_t hash2 = hash_table_mod2 (hash,
> > >>>>>>>>>>>> m_size_prime_index);
> > >>>>>>>>>>>> @@ -930,6 +935,39 @@ hash_table<Descriptor, Allocator>
> > >>>>>>>>>>>> return &m_entries[index];
> > >>>>>>>>>>>> }
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> +#if ENABLE_EXTRA_CHECKING
> > >>>>>>>>>>>> +
> > >>>>>>>>>>>> +/* Report a hash table checking error. */
> > >>>>>>>>>>>> +
> > >>>>>>>>>>>> +ATTRIBUTE_NORETURN ATTRIBUTE_COLD
> > >>>>>>>>>>>> +static void
> > >>>>>>>>>>>> +hashtab_chk_error ()
> > >>>>>>>>>>>> +{
> > >>>>>>>>>>>> + fprintf (stderr, "hash table checking failed: "
> > >>>>>>>>>>>> + "equal operator returns true for a pair "
> > >>>>>>>>>>>> + "of values with a different hash value\n");
> > >>>>>>>>>>>> + gcc_unreachable ();
> > >>>>>>>>>>>> +}
> > >>>>>>>>>>> I think an internal_error here is probably still better than a
> > >>>>>>>>>>> simple
> > >>>>>>>>>>> fprintf, even if the fprintf is terminated with a \n :-)
> > >>>>>>>>>> Fully agree with that, but I see a lot of build errors when
> > >>>>>>>>>> using internal_error.
> > >>>>>>>>>>
> > >>>>>>>>>>> The question then becomes can we bootstrap with this stuff
> > >>>>>>>>>>> enabled and
> > >>>>>>>>>>> if not, are we likely to soon? It'd be a shame to put it into
> > >>>>>>>>>>> EXTRA_CHECKING, but then not be able to really use
> > >>>>>>>>>>> EXTRA_CHECKING
> > >>>>>>>>>>> because we've got too many bugs to fix.
> > >>>>>>>>>> Unfortunately it's blocked with these 2 PRs:
> > >>>>>>>>>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87845
> > >>>>>>>>>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87847
> > >>>>>>>>> Hi.
> > >>>>>>>>>
> > >>>>>>>>> I've just added one more PR:
> > >>>>>>>>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90450
> > >>>>>>>>>
> > >>>>>>>>> I'm sending updated version of the patch that provides a
> > >>>>>>>>> disablement for the 3 PRs
> > >>>>>>>>> with a new function disable_sanitize_eq_and_hash.
> > >>>>>>>>>
> > >>>>>>>>> With that I can bootstrap and finish tests. However, I've done
> > >>>>>>>>> that with a patch
> > >>>>>>>>> limits maximal number of checks:
> > >>>>>>>> So rather than call the disable_sanitize_eq_and_hash, can you have
> > >>>>>>>> its
> > >>>>>>>> state set up when you instantiate the object? It's not a huge
> > >>>>>>>> deal,
> > >>>>>>>> just thinking about loud.
> > >>>>>>>>
> > >>>>>>>>
> > >>>>>>>>
> > >>>>>>>> So how do we want to go forward, particularly the EXTRA_EXTRA
> > >>>>>>>> checking
> > >>>>>>>> issue :-)
> > >>>>>>>
> > >>>>>>> There is at least one PR where we have a table where elements _in_
> > >>>>>>> the
> > >>>>>>> table are never compared against each other but always against
> > >>>>>>> another
> > >>>>>>> object (I guess that's usual even), but the setup is in a way that
> > >>>>>>> the
> > >>>>>>> comparison function only works with those. With the patch we verify
> > >>>>>>> hashing/comparison for something that is never used.
> > >>>>>>>
> > >>>>>>> So - wouldn't it be more "correct" to only verify comparison/hashing
> > >>>>>>> at lookup time, using the object from the lookup and verify that
> > >>>>>>> against
> > >>>>>>> all other elements?
> > >>>>>>
> > >>>>>> I don't a have problem with that. Apparently this changes fixes
> > >>>>>> PR90450 and PR87847.
> > >>>>>>
> > >>>>>> Changes from previous version:
> > >>>>>> - verification happens only when an element is searched (not
> > >>>>>> inserted)
> > >>>>>> - new argument 'sanitize_eq_and_hash' added for
> > >>>>>> hash_table::hash_table
> > >>>>>> - new param has been introduced hash-table-verification-limit in
> > >>>>>> order
> > >>>>>> to limit number of elements that are compared within a table
> > >>>>>> - verification happens only with flag_checking >= 2
> > >>>>>>
> > >>>>>> I've been bootstrapping and testing the patch right now.
> > >>>>>
> > >>>>> Looks like I misremembered the original patch. The issue isn't
> > >>>>> comparing random two elements in the table.
> > >>>>>
> > >>>>> That it fixes PR90450 is because LIM never calls find_slot_with_hash
> > >>>>> without INSERTing.
> > >>>>>
> > >>>>
> > >>>> There's updated version of the patch where I check all find operations
> > >>>> (both w/ and w/o insertion).
> > >>>>
> > >>>> Patch can bootstrap on x86_64-linux-gnu and survives regression tests
> > >>>> except for:
> > >>>>
> > >>>> $ ./xgcc -B.
> > >>>> /home/marxin/Programming/gcc/gcc/testsuite/gcc.dg/torture/pr63941.c
> > >>>> -O2 -c
> > >>>> hash table checking failed: equal operator returns true for a pair of
> > >>>> values with a different hash value
> > >>>> during GIMPLE pass: lim
> > >>>> /home/marxin/Programming/gcc/gcc/testsuite/gcc.dg/torture/pr63941.c:
> > >>>> In function ‘fn1’:
> > >>>> /home/marxin/Programming/gcc/gcc/testsuite/gcc.dg/torture/pr63941.c:6:1:
> > >>>> internal compiler error: in hashtab_chk_error, at hash-table.h:1019
> > >>>> 6 | fn1 ()
> > >>>> | ^~~
> > >>>> 0x6c5725 hashtab_chk_error
> > >>>> /home/marxin/Programming/gcc/gcc/hash-table.h:1019
> > >>>> 0xe504ea hash_table<mem_ref_hasher, false,
> > >>>> xcallocator>::verify(ao_ref* const&, unsigned int)
> > >>>> /home/marxin/Programming/gcc/gcc/hash-table.h:1040
> > >>>> 0xe504ea hash_table<mem_ref_hasher, false,
> > >>>> xcallocator>::find_slot_with_hash(ao_ref* const&, unsigned int,
> > >>>> insert_option)
> > >>>> /home/marxin/Programming/gcc/gcc/hash-table.h:960
> > >>>> 0xe504ea gather_mem_refs_stmt
> > >>>> /home/marxin/Programming/gcc/gcc/tree-ssa-loop-im.c:1501
> > >>>> 0xe504ea analyze_memory_references
> > >>>> /home/marxin/Programming/gcc/gcc/tree-ssa-loop-im.c:1625
> > >>>> 0xe504ea tree_ssa_lim
> > >>>> /home/marxin/Programming/gcc/gcc/tree-ssa-loop-im.c:2646
> > >>>> 0xe504ea execute
> > >>>> /home/marxin/Programming/gcc/gcc/tree-ssa-loop-im.c:2708
> > >>>>
> > >>>> Richi: it's after your recent patch.
> > >>>>
> > >>>> For some reason I don't see PR87847 issue any longer.
> > >>>>
> > >>>>
> > >>>> May I install the patch with disabled sanitization in
> > >>>> tree-ssa-loop-im.c ?
> > >>> Don't we still need to deal with the naked fprintf when there's a
> > >>> failure. ie, shouldn't we be raising it with a gcc_assert or somesuch?
> > >>
> > >> Good point, I've just adjusted that.
> > >>
> > >> Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
> > >>
> > >> Ready to be installed?
> > >
> > > Ugh, the cselib one is really bad. But I don't hold my breath for anyone
> > > fixing it ...
> >
> > Yes :D It's been some time and there's no interest in the PR.
> >
> > >
> > > One question - there's unconditional
> > >
> > > + if (m_sanitize_eq_and_hash)
> > > + verify (comparable, hash);
> > >
> > > which will read a global variable and have (possibly not inline) call
> > > to verify on a common path even with checking disabled. So I think
> > > we want to compile this checking feature out for !CHECKING_P
> > > or at least make the if __builtin_expect (..., 0), ::verify not
> > > inlined and marked pure () (thus, !CHECKING_P is simplest ;)).
> >
> > Fixed. May I install the patch? The cselib issue can be solved later..
>
> After this patch, when I do a configure with --disable-bootstrap, and
> build with "gcc (Debian 7.3.0-18) 7.3.0", I get a lot of warnings of
> the form
>
> In file included from ../../gccgo3/gcc/coretypes.h:440:0,
> from ../../gccgo3/gcc/go/go-system.h:137,
> from ../../gccgo3/gcc/go/gofrontend/go.cc:7:
> ../../gccgo3/gcc/hash-table.h:1017:1: warning: ‘void
> hashtab_chk_error()’ defined but not used [-Wunused-function]
> hashtab_chk_error ()
> ^~~~~~~~~~~~~~~~~
>
> These are just warnings, since I am using --disable-bootstrap, but
> they are distracting.
>
> This patch fixes it. OK for trunk?
Hmm, the function is called exactly once. I guess the intent was
to not emit the printf in every ::verify instance but then why not
instantiate this function in just hash-table.c and not mark it inline?
Richard.
>
> Ian
>
> 2019-06-23 Ian Lance Taylor <i...@golang.org>
>
> * hash-table.h (hashtab_chk_error): Add ATTRIBUTE_UNUSED.
