* [Bug tree-optimization/109539] [13/14 Regression] Compile-time hog in gimple-ssa-warn-access.cc since r13-6706-gadb70c2d1060b3
2023-04-18 6:48 [Bug tree-optimization/109539] New: [13/14 Regression] Compile-time hog in gimple-ssa-warn-access.cc since r13-6706-gadb70c2d1060b3 marxin at gcc dot gnu.org
@ 2023-04-18 6:50 ` marxin at gcc dot gnu.org
2023-04-18 8:22 ` marxin at gcc dot gnu.org
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From: marxin at gcc dot gnu.org @ 2023-04-18 6:50 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109539
Martin Liška <marxin at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |13.0
Ever confirmed|0 |1
CC| |jirislaby at gmail dot com
Last reconfirmed| |2023-04-18
Status|UNCONFIRMED |NEW
^ permalink raw reply [flat|nested] 9+ messages in thread* [Bug tree-optimization/109539] [13/14 Regression] Compile-time hog in gimple-ssa-warn-access.cc since r13-6706-gadb70c2d1060b3
2023-04-18 6:48 [Bug tree-optimization/109539] New: [13/14 Regression] Compile-time hog in gimple-ssa-warn-access.cc since r13-6706-gadb70c2d1060b3 marxin at gcc dot gnu.org
2023-04-18 6:50 ` [Bug tree-optimization/109539] " marxin at gcc dot gnu.org
@ 2023-04-18 8:22 ` marxin at gcc dot gnu.org
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From: marxin at gcc dot gnu.org @ 2023-04-18 8:22 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109539
--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
Created attachment 54877
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54877&action=edit
Reduced test-case
Takes 1.77s after the mentioned revision and 0.15s before it.
^ permalink raw reply [flat|nested] 9+ messages in thread* [Bug tree-optimization/109539] [13/14 Regression] Compile-time hog in gimple-ssa-warn-access.cc since r13-6706-gadb70c2d1060b3
2023-04-18 6:48 [Bug tree-optimization/109539] New: [13/14 Regression] Compile-time hog in gimple-ssa-warn-access.cc since r13-6706-gadb70c2d1060b3 marxin at gcc dot gnu.org
2023-04-18 6:50 ` [Bug tree-optimization/109539] " marxin at gcc dot gnu.org
2023-04-18 8:22 ` marxin at gcc dot gnu.org
@ 2023-04-18 8:44 ` rguenth at gcc dot gnu.org
2023-04-18 9:12 ` rguenth at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2023-04-18 8:44 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109539
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot gnu.org
Status|NEW |ASSIGNED
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
I will have a look.
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2023-04-18 6:48 [Bug tree-optimization/109539] New: [13/14 Regression] Compile-time hog in gimple-ssa-warn-access.cc since r13-6706-gadb70c2d1060b3 marxin at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2023-04-18 9:12 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109539
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
The issue is almost certainly the cost of pointers_related_p
Samples: 3M of event 'cycles', Event count (approx.): 3573086788171
Children Self Samples Command Shared Object Symbol
- 93.15% 0.80% 25898 cc1plus cc1plus [.] (anonymous
namespace)::pointers_related_p #
- 92.35% (anonymous namespace)::pointers_related_p
#
- 92.30% (anonymous namespace)::pointers_related_p
#
- 92.21% (anonymous namespace)::pointers_related_p
#
- 92.12% (anonymous namespace)::pointers_related_p
#
- 92.02% (anonymous namespace)::pointers_related_p
#
- 91.93% (anonymous namespace)::pointers_related_p
#
- 91.84% (anonymous namespace)::pointers_related_p
#
- 91.75% (anonymous namespace)::pointers_related_p
#
- 91.66% (anonymous namespace)::pointers_related_p
#
- 91.57% (anonymous
namespace)::pointers_related_p #
- 91.48% (anonymous
namespace)::pointers_related_p #
- 91.39% (anonymous
namespace)::pointers_related_p #
- 87.34% (anonymous
namespace)::pointers_related_p #
- 62.30% (anonymous
namespace)::pointers_related_p #
- 44.52% pointer_query::get_ref
#
- 44.51% compute_objsize
#
+ 15.03%
access_ref::size_remaining #
+ 14.49% wide_int_to_tree
#
+ 4.91%
generic_wide_int<fixed_wide_int_storage<128> >::operat#
+ 4.57% operator<
<generic_wide_int<fixed_wide_int_storage<128#
+ 2.41% poly_int<1u,
generic_wide_int<wide_int_ref_storage<fal#
+ 1.15%
pointer_query::~pointer_query #
0.80%
pointer_query::pointer_query #
0.78% compute_objsize_r
#
- 14.08% (anonymous
namespace)::pointers_related_p #
+ 6.14% access_ref::access_ref
#
+ 4.53% pointer_query::get_ref
#
+ 2.07% ptr_derefs_may_alias_p
#
+ 3.70% access_ref::access_ref
#
+ 25.03% pointer_query::get_ref
#
+ 4.04% pointer_query::get_ref
^ permalink raw reply [flat|nested] 9+ messages in thread* [Bug tree-optimization/109539] [13/14 Regression] Compile-time hog in gimple-ssa-warn-access.cc since r13-6706-gadb70c2d1060b3
2023-04-18 6:48 [Bug tree-optimization/109539] New: [13/14 Regression] Compile-time hog in gimple-ssa-warn-access.cc since r13-6706-gadb70c2d1060b3 marxin at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2023-04-18 9:49 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109539
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
So what we try to do is, when check_pointer_uses follows the use chain
of 'ptr' through say
ptr2 = ptr + 4;
then it wants to visit ptr2 uses as well. For PHIs we get to
ptr2 = PHI <..., ptr, ...>;
and we want to consider uses of ptr2 only if all other PHI arguments
are "related" to 'ptr'. To prove that we perform complicated gymnastics,
in particular the only real check done is
if (!ptr_derefs_may_alias_p (p, q))
return false;
and that's of course incredibly weak. To disprove relatedness
the pointers_related_p recurses, but only when either of both
pointers are defined by a PHI. It uses pointer-query to skip
chains of pointer adjustments up to such definition.
So we basically do forward relatedness in check_pointer_uses and
then backward relatedness in pointers_related_p.
I think we should eschew that completely and only try to handle "forward"
PHIs by the iteration in check_pointer_uses itself.
^ permalink raw reply [flat|nested] 9+ messages in thread* [Bug tree-optimization/109539] [13/14 Regression] Compile-time hog in gimple-ssa-warn-access.cc since r13-6706-gadb70c2d1060b3
2023-04-18 6:48 [Bug tree-optimization/109539] New: [13/14 Regression] Compile-time hog in gimple-ssa-warn-access.cc since r13-6706-gadb70c2d1060b3 marxin at gcc dot gnu.org
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From: cvs-commit at gcc dot gnu.org @ 2023-04-18 12:38 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109539
--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:
https://gcc.gnu.org/g:fdbaab2dc886f78a1e75512eeee0faa17e77c862
commit r14-30-gfdbaab2dc886f78a1e75512eeee0faa17e77c862
Author: Richard Biener <rguenther@suse.de>
Date: Tue Apr 18 11:49:48 2023 +0200
tree-optimization/109539 - restrict PHI handling in access diagnostics
Access diagnostics visits the SSA def-use chains to diagnose things like
dangling pointer uses. When that runs into PHIs it tries to prove
all incoming pointers of which one is the currently visited use are
related to decide whether to keep looking for the PHI def uses.
That turns out to be overly optimistic and thus costly. The following
scraps the existing handling for simply requiring that we eventually
visit all incoming pointers of the PHI during the def-use chain
analysis and only then process uses of the PHI def.
Note this handles backedges of natural loops optimistically, diagnosing
the first iteration. There's gcc.dg/Wuse-after-free-2.c containing
a testcase requiring this.
PR tree-optimization/109539
* gimple-ssa-warn-access.cc (pass_waccess::check_pointer_uses):
Re-implement pointer relatedness for PHIs.
^ permalink raw reply [flat|nested] 9+ messages in thread* [Bug tree-optimization/109539] [13/14 Regression] Compile-time hog in gimple-ssa-warn-access.cc since r13-6706-gadb70c2d1060b3
2023-04-18 6:48 [Bug tree-optimization/109539] New: [13/14 Regression] Compile-time hog in gimple-ssa-warn-access.cc since r13-6706-gadb70c2d1060b3 marxin at gcc dot gnu.org
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From: cvs-commit at gcc dot gnu.org @ 2023-04-18 12:38 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109539
--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-13 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:
https://gcc.gnu.org/g:68aea7801848f978f8b5461807dfd3b7a504da1e
commit r13-7215-g68aea7801848f978f8b5461807dfd3b7a504da1e
Author: Richard Biener <rguenther@suse.de>
Date: Tue Apr 18 11:49:48 2023 +0200
tree-optimization/109539 - restrict PHI handling in access diagnostics
Access diagnostics visits the SSA def-use chains to diagnose things like
dangling pointer uses. When that runs into PHIs it tries to prove
all incoming pointers of which one is the currently visited use are
related to decide whether to keep looking for the PHI def uses.
That turns out to be overly optimistic and thus costly. The following
scraps the existing handling for simply requiring that we eventually
visit all incoming pointers of the PHI during the def-use chain
analysis and only then process uses of the PHI def.
Note this handles backedges of natural loops optimistically, diagnosing
the first iteration. There's gcc.dg/Wuse-after-free-2.c containing
a testcase requiring this.
PR tree-optimization/109539
* gimple-ssa-warn-access.cc (pass_waccess::check_pointer_uses):
Re-implement pointer relatedness for PHIs.
(cherry picked from commit fdbaab2dc886f78a1e75512eeee0faa17e77c862)
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2023-04-18 6:48 [Bug tree-optimization/109539] New: [13/14 Regression] Compile-time hog in gimple-ssa-warn-access.cc since r13-6706-gadb70c2d1060b3 marxin at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2023-04-18 12:39 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109539
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|ASSIGNED |RESOLVED
--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed.
^ permalink raw reply [flat|nested] 9+ messages in thread