[Bug debug/61033] New: Infinite loop in variable tracking

[Bug debug/61033] New: Infinite loop in variable tracking

[michael.collison at linaro dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61033

            Bug ID: 61033
           Summary: Infinite loop in variable tracking
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: michael.collison at linaro dot org

Created attachment 32722
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32722&action=edit
Preprocssed file to reproduce bug

Data flow analysis in variable tracking does not converge and causes an
infinite loop with the attached file and following compile options:

./cc1plus -quiet -fpreprocessed qmltextgenerator.ii -dumpbase
qmltextgenerator.ii -march=armv4t -mfloat-abi=soft -mtls-dialect=gnu
-auxbase-strip x.o -g -O2 -Wformat=1 -Werror=format-security -Wall -Wextra
-version -fstack-protector -fvisibility=hidden -fvisibility-inlines-hidden
-fPIC --param ssp-buffer-size=4 -o qmltextgenerator.s

GCC configured with --target=arm-linux-gnueabi

[Bug debug/61033] Infinite loop in variable tracking

[ktkachov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61033

ktkachov at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |doko at gcc dot gnu.org

--- Comment #3 from ktkachov at gcc dot gnu.org ---
*** Bug 62013 has been marked as a duplicate of this bug. ***

[Bug debug/61033] Infinite loop in variable tracking

[ktkachov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61033

ktkachov at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |compile-time-hog
             Target|arm-linux-gnueabi           |arm-linux-gnueabi,
                   |                            |arm-none-eabi
      Known to work|                            |4.10.0, 4.7.4
      Known to fail|                            |4.8.3, 4.9.1

--- Comment #4 from ktkachov at gcc dot gnu.org ---
Filling in some fields, this still fails on the 4.8 and 4.9 branches but works
on trunk.

[Bug debug/61033] [4.8/4.9 Regression] Infinite loop in variable tracking

[cbaylis at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61033

cbaylis at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |cbaylis at gcc dot gnu.org

--- Comment #5 from cbaylis at gcc dot gnu.org ---
Created attachment 33244
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33244&action=edit
Reduced test case


$ arm-unknown-linux-gnueabihf-gcc -S -O2 -g reduced1.cpp

[Bug debug/61033] [4.8/4.9 Regression] Infinite loop in variable tracking

[cbaylis at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61033

--- Comment #6 from cbaylis at gcc dot gnu.org ---

git bisect points to r211625 as the revision which fixes/hides this bug on
trunk.

2014-06-13  Richard Biener  <rguenther@suse.de>

        * tree-ssa-pre.c (eliminate_dom_walker::before_dom_children):
        Rewrite to propagate the VN result into all uses where
        possible and to remove stmts becoming dead because of that.
        (eliminate): Generalize stmt removal handling, remove in
        reverse dominator order to support proper debug stmt
        generation.  Update stmts before removing stmts.
        * tree-ssa-propagate.c (propagate_tree_value): Remove
        bogus assert.

[Bug debug/61033] [4.8/4.9 Regression] Infinite loop in variable tracking

[michael.collison at linaro dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61033

--- Comment #7 from Michael Collison <michael.collison at linaro dot org> ---
Charlie,

I still feel that the var tracking pass should be able to protect itself 
from an infinite loop.

On 8/4/2014 11:43 AM, cbaylis at gcc dot gnu.org wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61033
>
> --- Comment #6 from cbaylis at gcc dot gnu.org ---
>
> git bisect points to r211625 as the revision which fixes/hides this bug on
> trunk.
>
> 2014-06-13  Richard Biener  <rguenther@suse.de>
>
>          * tree-ssa-pre.c (eliminate_dom_walker::before_dom_children):
>          Rewrite to propagate the VN result into all uses where
>          possible and to remove stmts becoming dead because of that.
>          (eliminate): Generalize stmt removal handling, remove in
>          reverse dominator order to support proper debug stmt
>          generation.  Update stmts before removing stmts.
>          * tree-ssa-propagate.c (propagate_tree_value): Remove
>          bogus assert.
>

[Bug debug/61033] [4.8/4.9 Regression] Infinite loop in variable tracking

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61033

David Binderman <dcb314 at hotmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dcb314 at hotmail dot com

--- Comment #8 from David Binderman <dcb314 at hotmail dot com> ---
Created attachment 33361
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33361&action=edit
C++ source code

[Bug debug/61033] [4.8/4.9 Regression] Infinite loop in variable tracking

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61033

--- Comment #9 from David Binderman <dcb314 at hotmail dot com> ---
(In reply to David Binderman from comment #8)
> Created attachment 33361 [details]
> C++ source code

Please ignore this attachment. It is for a different bug.

[Bug debug/61033] [4.8/4.9 Regression] Infinite loop in variable tracking

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61033

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.8.4

[Bug debug/61033] [4.8/4.9 Regression] Infinite loop in variable tracking

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61033

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2

[Bug debug/61033] [4.8/4.9 Regression] Infinite loop in variable tracking

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61033

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.8.4                       |4.8.5

--- Comment #11 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 4.8.4 has been released.

[Bug debug/61033] [4.8/4.9 Regression] Infinite loop in variable tracking

[michael.collison at linaro dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61033

Michael Collison <michael.collison at linaro dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|michael.collison at linaro dot org |mkuvyrkov at gcc dot gnu.org

--- Comment #12 from Michael Collison <michael.collison at linaro dot org> ---
GCC is looping infinitely in attempting to solve a data flow problem in
vt_find_locations. My working theory is that compute_bb_dataflow is incorrectly
asserting some value has changed. I have reduced my case to a candidate set of
basic blocks and a (candiate) RTL location this is continually removed/added.
The rtl location is:

dataflow difference found: removal of:
 name: D#255
   offset 0
     (mem/f/c:SI (value/u:SI 106:3955 @0x22cb2f8/0x23424a0) [3 result.d+0 S4
A32])


I understand that the argument to 'VALUE" is a cselib_val_struct but I don't
know how to map this back to a insn that is causing the problem. Any thoughts
on how I might debug thus further?

[Bug debug/61033] [4.8/4.9 Regression] Infinite loop in variable tracking

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61033

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.8.5                       |4.9.3

--- Comment #13 from Richard Biener <rguenth at gcc dot gnu.org> ---
The gcc-4_8-branch is being closed, re-targeting regressions to 4.9.3.

[Bug debug/61033] [4.9 Regression] Infinite loop in variable tracking

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61033

--- Comment #14 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 4.9.3 has been released.

[Bug debug/61033] [4.9 Regression] Infinite loop in variable tracking

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61033

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.9.3                       |4.9.4