[Bug c++/28139] New: alias information for EH is wrong

[Bug c++/28139] New: alias information for EH is wrong

[amylaar at gcc dot gnu dot org]

The store at the beginning of a catch block can use an alias set that is
allegedly disjoint from the one used to load that value.  When scheduling,
this can cause the load to be moved before the store.


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           Summary: alias information for EH is wrong
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Keywords: wrong-code, EH
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: amylaar at gcc dot gnu dot org
GCC target triplet: sh-elf


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28139

[Bug c++/28139] alias information for EH is wrong

[amylaar at gcc dot gnu dot org]

------- Comment #1 from amylaar at gcc dot gnu dot org  2006-06-22 15:52 -------
Created an attachment (id=11730)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11730&action=view)
test case

This test case should go in testsuite/g++.dg/eh .


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28139

[Bug c++/28139] alias information for EH is wrong

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2006-06-22 16:28 -------
Hmm, I just get an error on a 64bit target so the testcase is at least invalid
for them:
t.c:19: error: cast from 'int*' to 'int' loses precision


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28139

[Bug c++/28139] alias information for EH is wrong

[pinskia at gcc dot gnu dot org]

------- Comment #3 from pinskia at gcc dot gnu dot org  2006-06-22 16:34 -------
Though it is obviously wrong from the front-end:
register void * D.2002;
(int * * const &) &D.2002


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pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2006-06-22 16:34:21
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28139

[Bug c++/28139] alias information for EH is wrong

[amylaar at gcc dot gnu dot org]

------- Comment #4 from amylaar at gcc dot gnu dot org  2006-06-22 16:55 -------
(In reply to comment #2)
> Hmm, I just get an error on a 64bit target so the testcase is at least invalid
> for them:
> t.c:19: error: cast from 'int*' to 'int' loses precision
> 
You can write this as:
exit ((int)(long long) &i);
I have verified that this also reproduces the problem on sh-elf.

(In reply to comment #3)
> Though it is obviously wrong from the front-end:
> register void * D.2002;
> (int * * const &) &D.2002
> 

As far as I can tell, this code in cp/except.c:expand_start_catch_block:
  /* Otherwise the type uses a bitwise copy, and we don't have to worry
     about the value of std::uncaught_exception and therefore can do the
     copy with the return value of __cxa_end_catch instead.  */
  else
    {
      tree init = do_begin_catch ();
      exp = create_temporary_var (ptr_type_node);
      DECL_REGISTER (exp) = 1;
      cp_finish_decl (exp, init, /*init_const_expr=*/false,
                      NULL_TREE, LOOKUP_ONLYCONVERTING);
      initialize_handler_parm (decl, exp);

is wrong.  exp has the wrong type, hence the store emitted by cp_finish_decl
will end up with the wrong alias set.
I'm not sure yet what the right type is, though. would that be the type of decl
for pointers, and a pointer to that type for non-pointers?  Or a reference?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28139

[Bug c++/28139] alias information for EH is wrong

[amylaar at gcc dot gnu dot org]

------- Comment #5 from amylaar at gcc dot gnu dot org  2006-06-22 22:16 -------
Created an attachment (id=11732)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11732&action=view)
patch

I'm currently testing this patch.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28139

[Bug c++/28139] alias information for EH is wrong

[patchapp at dberlin dot org]

------- Comment #6 from patchapp at dberlin dot org  2006-06-29 21:42 -------
Subject: Bug number PR 28139

A patch for this bug has been added to the patch tracker.
The mailing list url for the patch is
http://gcc.gnu.org/ml/gcc-patches/2006-06/msg01295.html


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28139

[Bug c++/28139] alias information for EH is wrong

[amylaar at gcc dot gnu dot org]

------- Comment #7 from amylaar at gcc dot gnu dot org  2006-07-03 16:39 -------
The keyword description says that the "alias" keyword is specific to missed
optimizations due to aliasing issues.
If that is true, than adding this keyword here was incorrect.  If that isn't
true, then the keyword description should be corrected.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28139

[Bug c++/28139] alias information for EH is wrong

[mrs at apple dot com]

------- Comment #8 from mrs at apple dot com  2006-08-25 22:27 -------
Date: Fri, 25 Aug 2006 16:03:00 -0400
From: Jason Merrill <jason@redhat.com>
Subject: Re: RFA: Fix PR 28139
Message-id: <44EF5774.5050601@redhat.com>

This is OK.

:REVIEWURL http://gcc.gnu.org/ml/gcc-patches/2006-06/msg01295.html:


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28139

[Bug c++/28139] alias information for EH is wrong

[amylaar at gcc dot gnu dot org]

------- Comment #9 from amylaar at gcc dot gnu dot org  2006-08-29 14:34 -------
Subject: Bug 28139

Author: amylaar
Date: Tue Aug 29 14:34:36 2006
New Revision: 116561

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=116561
Log:
cp:
        PR c++/28139
        * except.c (expand_start_catch_block): Use correct types for bitwise
        copy.
testsuite:
        PR c++/28139
        * g++.dg/eh/alias1.C: New test.

Added:
    trunk/gcc/testsuite/g++.dg/eh/alias1.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/except.c
    trunk/gcc/testsuite/ChangeLog


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28139

[Bug c++/28139] alias information for EH is wrong

[amylaar at gcc dot gnu dot org]

------- Comment #10 from amylaar at gcc dot gnu dot org  2006-08-29 15:02 -------
Fixed on mainline; however, the problem was already present in 4.1, so we need
to decide if we want the patch in the 4.1 branch.


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amylaar at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |4.1.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28139

[Bug c++/28139] alias information for EH is wrong

[pinskia at gcc dot gnu dot org]

------- Comment #11 from pinskia at gcc dot gnu dot org  2007-10-04 10:11 -------
Fixed so closing.


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pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
      Known to work|4.3.0                       |4.3.0 4.2.0
         Resolution|                            |FIXED
   Target Milestone|---                         |4.2.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28139