[Bug c/31642] New: -O2 -fno-guess-branch-probability -fno-tree-ch -fno-tree-dominator-opts -fno-tree-lrs -fno-tree-dce -fno-tree-vrp -funit-at-a-time -ftree-copy-prop -ftree-copyrename yields an infinite loop in SPEC benchmark 176.gcc

[Bug c/31642] New: -O2 -fno-guess-branch-probability -fno-tree-ch -fno-tree-dominator-opts -fno-tree-lrs -fno-tree-dce -fno-tree-vrp -funit-at-a-time -ftree-copy-prop -ftree-copyrename yields an infinite loop in SPEC benchmark 176.gcc

[kenneth dot hoste at elis dot ugent dot be]

Using -O2 -fno-guess-branch-probability -fno-tree-ch -fno-tree-dominator-opts
-fno-tree-lrs -fno-tree-dce -fno-tree-vrp -funit-at-a-time -ftree-copy-prop
-ftree-copyrename on the SPEC CPU2000 benchmark 176.gcc yields an infinite loop
(using the train input which usually runs for 2s runs for hours). 

This is confirmed on Fedora Core 4 / x86 (Intel Pentium 4), and also on an
linux/amd64 for which I have no details.

Removing any of the -fno-X flags seems to solve the issue, and adding
-ffloat-store doesn't change a thing, which suggests this is not floating-point
(convergence) related.


-- 
           Summary: -O2 -fno-guess-branch-probability -fno-tree-ch -fno-
                    tree-dominator-opts -fno-tree-lrs -fno-tree-dce -fno-
                    tree-vrp -funit-at-a-time -ftree-copy-prop -ftree-
                    copyrename yields an infinite loop in SPEC benchmark
                    176.gcc
           Product: gcc
           Version: 4.1.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: kenneth dot hoste at elis dot ugent dot be
  GCC host triplet: i686-Linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31642

[Bug middle-end/31642] -O2 -fno-guess-branch-probability -fno-tree-ch -fno-tree-dominator-opts -fno-tree-lrs -fno-tree-dce -fno-tree-vrp -funit-at-a-time -ftree-copy-prop -ftree-copyrename yields an infinite loop in SPEC benchmark 176.gcc

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2007-04-20 18:24 -------
We need a testcase.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |WAITING
          Component|c                           |middle-end


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31642

[Bug c/31642] -O2 -fno-guess-branch-probability -fno-tree-ch -fno-tree-dominator-opts -fno-tree-lrs -fno-tree-dce -fno-tree-vrp -funit-at-a-time -ftree-copy-prop -ftree-copyrename yields an infinite loop in SPEC benchmark 176.gcc

[kenneth dot hoste at elis dot ugent dot be]

------- Comment #2 from kenneth dot hoste at elis dot ugent dot be  2007-04-20 19:24 -------
(In reply to comment #1)
> We need a testcase.
> 

I would provide one if I knew how, I'm quite new at this... Any pointers?


-- 

kenneth dot hoste at elis dot ugent dot be changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|middle-end                  |c


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31642

[Bug middle-end/31642] -O2 -fno-guess-branch-probability -fno-tree-ch -fno-tree-dominator-opts -fno-tree-lrs -fno-tree-dce -fno-tree-vrp -funit-at-a-time -ftree-copy-prop -ftree-copyrename yields an infinite loop in SPEC benchmark 176.gcc

[kenneth dot hoste at elis dot ugent dot be]

------- Comment #3 from kenneth dot hoste at elis dot ugent dot be  2007-04-20 20:51 -------
    identifying source code lines corresponding to infinite loop using GDB:

    (gdb) backtrace
    #0  regclass (f=0x9ac29f4, nregs=71) at regclass.c:732
    #1  0x08065d5c in rest_of_compilation (decl=0x9b4526c) at toplev.c:3056
    #2  0x0805713b in finish_function (nested=0) at c-decl.c:6791
    #3  0x08048a25 in yyparse () at c-parse.c:1684
    #4  0x08066a83 in compile_file (name=Variable "name" is not available.
    ) at toplev.c:2227
    #5  0x080681a3 in main (argc=4, argv=0xbf945ea4) at toplev.c:3921
    (gdb) n
    736               else if ((GET_CODE (insn) == INSN
    (gdb) n
    717           for (insn = f; insn; insn = NEXT_INSN (insn))
    (gdb) n
    729               if (GET_CODE (insn) == NOTE
    (gdb) n
    732               else if (GET_CODE (insn) == NOTE
    (gdb) n
    736               else if ((GET_CODE (insn) == INSN
    (gdb) n
    717           for (insn = f; insn; insn = NEXT_INSN (insn))
    (gdb) backtrace
    #0  regclass (f=0x9ac29f4, nregs=71) at regclass.c:717
    #1  0x08065d5c in rest_of_compilation (decl=0x9b4526c) at toplev.c:3056
    #2  0x0805713b in finish_function (nested=0) at c-decl.c:6791
    #3  0x08048a25 in yyparse () at c-parse.c:1684
    #4  0x08066a83 in compile_file (name=Variable "name" is not available.
    ) at toplev.c:2227
    #5  0x080681a3 in main (argc=4, argv=0xbf945ea4) at toplev.c:3921
    (gdb) 

    The program seems stuck in the for-loop at line 717. The value for insn
seems to be cycling (it's taking different values, but cycles back to a
previous value).

    Any pointers on how to reduce this further are welcome... Since this is
(pretty old though) GCC code (the 176.gcc corresponds to a 2.x version of GCC I
believe), maybe someone can shed soem light on this? I'm not at all familiar
with GCCs insides...


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31642

[Bug middle-end/31642] -O2 -fno-guess-branch-probability -fno-tree-ch -fno-tree-dominator-opts -fno-tree-lrs -fno-tree-dce -fno-tree-vrp -funit-at-a-time -ftree-copy-prop -ftree-copyrename yields an infinite loop in SPEC benchmark 176.gcc

[steven at gcc dot gnu dot org]

------- Comment #4 from steven at gcc dot gnu dot org  2008-02-03 14:21 -------
No test case, no activity, and, really, quite old already.  Please re-open if
you can still reproduce this.


-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31642