[Bug tree-optimization/42873] New: [4.5 Regression] deadlock in var tracking in recent builds

["zsojka at seznam dot cz" <gcc-bugzilla at gcc dot gnu dot org>]

This can be related to pr41371, but I think it is not duplicate. This one ends
in endless loop, as can be seen from -fdump-rtl-vartrack dumps - there are
about 50 lines periodically repeating.
I thought it's a dup of pr41371, but the compilation (of nonreduced testcase)
didn't finish even after one week.
Reduced testcase compilation finishes "in miliseconds" with -fno-var-tracking,
but takes forever without it. It's not slowly eating memory, so it never
crashes.

Command line:
gcc -O3 -g -fgcse-sm -ftracer testcase.c

Tested revisions (x86_64):
r156217 - fail
r156038 - fail
r155945 - fail (x86)
r155920 - fail
r155917 - fail
r155902 - OK
r155844 - OK (x86)
r155833 - OK
r155363 - OK
r154886 - OK
r153685 - OK
4.4 branch, r155365 - OK

Output (manually terminated):
$ time
/mnt/svn/gcc-trunk/binary-155920-lto/libexec/gcc/x86_64-unknown-linux-gnu/4.5.0/cc1
-v -O3 -g -fgcse-sm -ftracer testcase.c
ignoring nonexistent directory "/usr/local/include"
ignoring nonexistent directory
"/mnt/svn/gcc-trunk/binary-155920-lto/lib/gcc/x86_64-unknown-linux-gnu/4.5.0/../../../../x86_64-unknown-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /mnt/svn/gcc-trunk/binary-155920-lto/include

/mnt/svn/gcc-trunk/binary-155920-lto/lib/gcc/x86_64-unknown-linux-gnu/4.5.0/include

/mnt/svn/gcc-trunk/binary-155920-lto/lib/gcc/x86_64-unknown-linux-gnu/4.5.0/include-fixed
 /usr/include
End of search list.
 baz bar foo
Analyzing compilation unit
Performing interprocedural optimizations
 <visibility> <*free_lang_data> <early_local_cleanups> <whole-program> <cp>
<inline> <static-var> <pure-const>Assembling functions:
 foo^C

real    76m32.295s
user    74m33.830s
sys     0m0.730s


-- 
           Summary: [4.5 Regression] deadlock in var tracking in recent
                    builds
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: zsojka at seznam dot cz
  GCC host triplet: x86(_64)-pc-linux-gnu
GCC target triplet: x86(_64)-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42873