On 6/11/19 9:16 AM, Martin Liška wrote:
On 6/11/19 2:27 PM, Jason Merrill wrote:
On 6/11/19 3:41 AM, Martin Liška wrote:
On 6/10/19 8:21 PM, Jason Merrill wrote:
On Mon, Jun 10, 2019 at 3:08 AM Martin Liška <mli...@suse.cz> wrote:
On 6/7/19 11:43 PM, Jason Merrill wrote:
On Fri, Jun 7, 2019 at 8:14 AM Martin Liška <mli...@suse.cz> wrote:
On 6/7/19 2:09 PM, Richard Biener wrote:
On Fri, Jun 7, 2019 at 2:03 PM 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..
You missed the second occurance
- m_searches++;
+ if (m_sanitize_eq_and_hash)
+ verify (comparable, hash);
Yep ;) I've just install the patch.
This is breaking my build:
/home/jason/gt/gcc/hash-map.h:123:71: error: no matching function for
call to ‘hash_table<hash_map<mem_alloc_d\
escription<mem_usage>::mem_location_hash, mem_usage*,
simple_hashmap_traits<default_hash_traits<mem_alloc_desc\
ription<mem_usage>::mem_location_hash>, mem_usage*> >::hash_entry,
false, xcallocator>::hash_table(size_t&, bo\
ol&, bool&, mem_alloc_origin, const char*&, int&, const char*&)’
: m_table (n, ggc, gather_mem_stats, HASH_MAP_ORIGIN PASS_MEM_STAT) {}
Looks like this needs to be updated to pass an argument to the new
sanitize_eq_and_hash parameter.
Jason
Sorry for the breakage, I've just fixed that in r272104.
Thanks. I'm also seeing a massive compile time hit from this: A
constexpr testcase that I've been looking at went from compiling in 13
seconds to 78 seconds, 6 times as long. I would expect template-heavy
code to see similar problems when sanitization is enabled for those
hash tables. Could we keep the parameter low or 0 by default, and
just do occasional sanitize runs with it explicitly enabled?
Makes sense to me. Can you please provide a test-case which I can measure?
This is the one I've been looking at:
struct Int {
constexpr Int(int v): v(v) {}
constexpr Int& operator+=(Int b) { this->v += b.v; return *this; }
constexpr Int& operator++() { ++this->v; return *this; }
private:
friend constexpr bool operator<(Int a, Int b) { return a.v < b.v; }
int v;
};
constexpr int f(int n) {
Int i = {0};
Int k = {0};
k = 0;
for (; k<10000; ++k) {
i += k;
}
return n;
}
template<int N> struct S {
static constexpr int sm = S<N-1>::sm+f(N);
};
template<> struct S<0> {
static constexpr int sm = 0;
};
constexpr int r = S<20>::sm;
Jason
For the test-case provided I see:
$ time g++ time.cc -c --param hash-table-verification-limit=100
real 0m1.855s
user 0m1.829s
sys 0m0.025s
$ time g++ time.cc -c --param hash-table-verification-limit=0
real 0m1.275s
user 0m1.219s
sys 0m0.052s
$ time g++-9 time.cc -c
real 0m0.939s
user 0m0.827s
sys 0m0.109s
So it's slower, but I can't confirm the huge slowdown you see.
Is it due to r272144?
Hmm, I wonder if this is because of the
--enable-gather-detailed-mem-stats hash tables.
Jason
