[Bug tree-optimization/51551] New: tree-loop-optimize chews all memory

[Bug tree-optimization/51551] New: tree-loop-optimize chews all memory

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51551

             Bug #: 51551
           Summary: tree-loop-optimize chews all memory
    Classification: Unclassified
           Product: gcc
           Version: 4.6.2
            Status: UNCONFIRMED
          Keywords: memory-hog
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: gjl@gcc.gnu.org
              Host: i686-pc-linux-gnu
            Target: i686-pc-linux-gnu
             Build: i686-pc-linux-gnu


Created attachment 26082
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26082
bug-loop.c

The test program attached don't finish compilation and gcc is entering infinite
loop that chews up all of memory.

Compile with:

$ gcc bug-loop.c -S -Os

Following works:

$ gcc bug-loop.c -S -O2
$ gcc bug-loop.c -S -Os -fno-tree-loop-optimize

[Bug tree-optimization/51551] tree-loop-optimize chews all memory

[gjl at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51551

--- Comment #1 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2011-12-14 15:21:45 UTC ---
Created attachment 26083
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26083
Compiler output with -v

[Bug tree-optimization/51551] tree-loop-optimize chews all memory

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51551

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011-12-14
      Known to work|                            |4.7.0
     Ever Confirmed|0                           |1

--- Comment #2 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-12-14 16:36:12 UTC ---
It's complete unrolling (a known culprit).  4.7 works for some reason,
maybe because I fixed loop invariant motion (who knows ;)

[Bug tree-optimization/51551] tree-loop-optimize chews all memory

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51551

Mikael Pettersson <mikpe at it dot uu.se> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mikpe at it dot uu.se

--- Comment #3 from Mikael Pettersson <mikpe at it dot uu.se> 2011-12-26 16:51:40 UTC ---
This test case was fixed on trunk by r171465:
http://gcc.gnu.org/ml/gcc-patches/2011-03/msg01765.html
http://gcc.gnu.org/ml/gcc-cvs/2011-03/msg00889.html

However r171465 caused PR48290, so a backport also needs the two PR48290 fixes
(r171657 + r172494).  With all three backported to 4.6.2 the test case is fixed
there too with no test suite regressions for me on i686-linux.

But this may be a too large change for the upstream 4.6 branch.

[Bug tree-optimization/51551] tree-loop-optimize chews all memory

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51551

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
   Target Milestone|---                         |4.7.0
             Status|NEW                         |RESOLVED

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Closing as fixed in GCC 4.7.0. Propagating constants earlier does decrease
memory usage.