[Bug tree-optimization/51117] New: [4.7 regression] rev.181172 causes glibc build failure

[Bug tree-optimization/51117] New: [4.7 regression] rev.181172 causes glibc build failure

[markus at trippelsdorf dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51117

             Bug #: 51117
           Summary: [4.7 regression] rev.181172 causes glibc build failure
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: markus@trippelsdorf.de


On x86_64-pc-linux-gnu I get the following error when I build the latest
git version of glibc:

cc   -nostdlib -nostartfiles -r -o /var/tmp/glibc-build/libc_pic.os \
 -Wl,-d -Wl,--whole-archive /var/tmp/glibc-build/libc_pic.a -o
/var/tmp/glibc-build/libc_pic.os
gcc   -nostdlib -nostartfiles -r -o /var/tmp/glibc-build/elf/librtld.map.o
'-Wl,-(' /var/tmp/glibc-build/elf/dl-allobjs.os /var/tmp/glibc-build/libc_
pic.a -lgcc '-Wl,-)' -Wl,-Map,/var/tmp/glibc-build/elf/librtld.mapT
/var/tmp/glibc-build/libc_pic.a(dl-addr.os): In function
`_dl_addr_inside_object':
/var/tmp/glibc/elf/dl-addr.c:155: multiple definition of
`_dl_addr_inside_object'
/var/tmp/glibc-build/elf/dl-allobjs.os:/var/tmp/glibc/elf/dl-open.c:673: first
defined here
/var/tmp/glibc-build/libc_pic.a(init-first.os):(.data+0x0): multiple definition
of `__libc_multiple_libcs'
/var/tmp/glibc-build/elf/dl-allobjs.os:/var/tmp/glibc/elf/rtld.c:658: first
defined here
collect2: error: ld returned 1 exit status
make[2]: *** [/var/tmp/glibc-build/elf/librtld.map] Error 1
make[2]: *** Waiting for unfinished jobs....

I've git bisected this failure to:

3c25489e88a7ea2937c19abff9163d9f7d8ca53a is the first bad commit
commit 3c25489e88a7ea2937c19abff9163d9f7d8ca53a
Author: matz <matz@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Tue Nov 8 16:47:16 2011 +0000

        * gengtype.c (write_field_root): Avoid out-of-scope access of newv.

        * tree-stdarg.c (execute_optimize_stdarg): Accept clobbers.

        * tree.h (TREE_CLOBBER_P): New macro.
        * gimple.h (gimple_clobber_p): New inline function.
        * gimplify.c (gimplify_bind_expr): Add clobbers for all variables
        that go out of scope and live in memory.
        * tree-ssa-operands.c (get_expr_operands): Transfer volatility also
        for constructors.
        * cfgexpand.c (decl_to_stack_part): New static variable.
        (add_stack_var): Allocate it, and remember mapping.
        (fini_vars_expansion): Deallocate it.
        (stack_var_conflict_p): Add early outs.
        (visit_op, visit_conflict, add_scope_conflicts_1,
        add_scope_conflicts): New static functions.
        (expand_used_vars_for_block): Don't call add_stack_var_conflict, tidy.
        (expand_used_vars): Add scope conflicts.
        (expand_gimple_stmt_1): Expand clobbers to nothing.
        (expand_debug_expr): Ditto.

        * tree-pretty-print.c (dump_generic_node): Dump clobbers nicely.
        * tree-ssa-live.c (remove_unused_locals): Remove clobbers that
        refer to otherwise unused locals.
        * tree-sra.c (build_accesses_from_assign): Ignore clobbers.
        * tree-ssa-dce.c (mark_stmt_if_obviously_necessary): Clobbers of
        SSA names aren't necessary.
        (propagate_necessity): Accept and ignore constructors on the rhs,
        tidy.
        * gimple.c (walk_gimple_op): Accept constructors like mem_rhs.
        * tree-ssa-structalias.c (find_func_aliases): Clobbers don't store
        any known value.
        * tree-ssa-sccvn.c (vn_reference_lookup_3): Ditto, in particular they
        don't zero-initialize something.
        * tree-ssa-phiopt.c (cond_if_else_store_replacement_1): Ignore
        clobber RHS, we don't want PHI nodes with those.

    testsuite/
        * gcc.dg/tree-ssa/20031015-1.c: Adjust.
        * g++.dg/tree-ssa/ehcleanup-1.C: Ditto.
        * g++.dg/eh/builtin1.C: Rewrite to not use local variables.
        * g++.dg/eh/builtin2.C: Ditto.
        * g++.dg/eh/builtin3.C: Ditto.


    git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@181172
138bc75d-0d04-0410-961f-82ee72b054a4

[Bug tree-optimization/51117] [4.7 regression] rev.181172 causes glibc build failure

[izamyatin at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51117

Igor Zamyatin <izamyatin at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |izamyatin at gmail dot com

--- Comment #1 from Igor Zamyatin <izamyatin at gmail dot com> 2011-11-15 10:32:30 UTC ---
I see the same problem. Anybody else met this issue?

[Bug tree-optimization/51117] [4.7 regression] rev.181172 causes glibc build failure

[matz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51117

Michael Matz <matz at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |MOVED

--- Comment #2 from Michael Matz <matz at gcc dot gnu.org> 2011-11-15 15:50:21 UTC ---
See http://sourceware.org/bugzilla/show_bug.cgi?id=13411 for analysis and 
possible patch.  The newly emitted calls to _Unwind_Resume suck in new object
files that weren't included before leading to these multiple defined symbols.
glibc needs to deal with this in one or the other way.

[Bug tree-optimization/51117] [4.7 regression] rev.181172 causes glibc build failure

[rth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51117

Richard Henderson <rth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
   Last reconfirmed|                            |2011-11-29
                 CC|                            |rth at gcc dot gnu.org
         Resolution|MOVED                       |
     Ever Confirmed|0                           |1

--- Comment #3 from Richard Henderson <rth at gcc dot gnu.org> 2011-11-29 18:06:55 UTC ---
I think this is a gcc bug.  In particular, one of two things ought to happen:

(1) Use the form of try_finally that ignores EH.  This would lose clobber
    information on EH paths; dunno if this really turns out to be important.

(2) Remove EH cleanup handlers that only involve clobbers which lead to 
    function exit via REX.  This would wait until pass_lower_eh_dispatch,
    as that's the first point at which we know whether we actually exit
    the function, post-inlining.

[Bug tree-optimization/51117] [4.7 regression] rev.181172 causes glibc build failure

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51117

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.7.0

[Bug tree-optimization/51117] [4.7 regression] rev.181172 causes glibc build failure

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51117

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

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

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-12-05 14:57:39 UTC ---
I agree it is a gcc bug, please see
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51275
for more information.

[Bug tree-optimization/51117] [4.7 regression] rev.181172 causes glibc build failure

[jsm28 at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51117

Joseph S. Myers <jsm28 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P1

[Bug tree-optimization/51117] [4.7 regression] rev.181172 causes glibc build failure

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51117

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |ASSIGNED
         AssignedTo|unassigned at gcc dot       |jakub at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-12-08 17:24:27 UTC ---
Created attachment 26025
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26025
gcc47-pr51117.patch

Untested fix.  This improves e.g.:
struct A { char buf[64]; };

void bar (A *);

void
foo ()
{
  {
    A a;
    bar (&a);
    if (a.buf[13])
      throw 1;
  }
  {
    A b;
    bar (&b);
    if (b.buf[13])
      throw 2;
  }
}

back to 4.6 generated code quality, but it doesn't already e.g.:
struct A
{
  char buf[64];
};
void bar (A *);
void
foo ()
{
  A c;
  bar (&c);
  try
  {
    {
      A a;
      bar (&a);
      if (a.buf[13])
throw 1;
      else if (a.buf[52])
throw 3;
    }
    {
      A b;
      bar (&b);
      if (b.buf[13])
throw 2;
    }
  }
  catch ( ...)
  {
    throw;
  }
}

I think it should be safe to move the clobbers to the EH destination of the
!stmt_can_throw_external (stmt) GIMPLE_RESX for that, but am not 100% sure
about that yet and would prefer to do it incrementally anyway.

[Bug tree-optimization/51117] [4.7 regression] rev.181172 causes glibc build failure

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51117

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-12-09 11:48:33 UTC ---
Author: jakub
Date: Fri Dec  9 11:48:30 2011
New Revision: 182158

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=182158
Log:
    PR tree-optimization/51117
    * tree-eh.c (optimize_clobbers): New function.
    (execute_lower_eh_dispatch): Call it.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/tree-eh.c

[Bug tree-optimization/51117] [4.7 regression] rev.181172 causes glibc build failure

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51117

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-12-09 16:09:48 UTC ---
Created attachment 26034
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26034
gcc47-pr51117-sink.patch

So far untested attempt to sink clobbers if a BB with all EH pred edges and a
single EH succ edge, ending with internal throwing RESX contains other than
that just CLOBBER stmts (and optionally debug stmts).
Such BBs force us to immediately rethrow with no actual code in between, when
the clobber stmts are sunk into the successor, we can actually ehcleanup those.
Had to tweak a little bit the conflict detection in the expander for that
though, without that it would think the vars still conflict on the incoming
edge (even when no actual insns that might touch memory appear before the
clobber).

[Bug tree-optimization/51117] [4.7 regression] rev.181172 causes glibc build failure

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51117

--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-12-09 20:50:50 UTC ---
Author: jakub
Date: Fri Dec  9 20:50:40 2011
New Revision: 182177

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=182177
Log:
    PR tree-optimization/51117
    * tree-eh.c (optimize_clobbers): Don't remove just one
    clobber, but all consecutive clobbers before RESX.
    Use gimple_clobber_p predicate.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/tree-eh.c

[Bug tree-optimization/51117] [4.7 regression] rev.181172 causes glibc build failure

[matz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51117

--- Comment #9 from Michael Matz <matz at gcc dot gnu.org> 2011-12-13 13:59:42 UTC ---
Author: matz
Date: Tue Dec 13 13:59:35 2011
New Revision: 182283

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=182283
Log:
    PR tree-optimization/51117
    * tree-eh.c (sink_clobbers): New function.
    (execute_lower_eh_dispatch): Call it for BBs ending with
    internally throwing RESX.
    * cfgexpand.c (add_scope_conflicts_1): Add all conflicts only
    at the first real instruction.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/cfgexpand.c
    trunk/gcc/tree-eh.c

[Bug tree-optimization/51117] [4.7 regression] rev.181172 causes glibc build failure

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51117

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #10 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-12-13 14:04:52 UTC ---
Fixed.

[Bug tree-optimization/51117] [4.7 regression] rev.181172 causes glibc build failure

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51117

--- Comment #11 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-12-15 17:27:11 UTC ---
Author: jakub
Date: Thu Dec 15 17:27:08 2011
New Revision: 182379

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=182379
Log:
    PR tree-optimization/51117
    * g++.dg/opt/pr51117.C: New test.

Added:
    trunk/gcc/testsuite/g++.dg/opt/pr51117.C
Modified:
    trunk/gcc/testsuite/ChangeLog