[Bug rtl-optimization/58034] New: glibc nptl/tst-cleanup2 fail due to scheduling

[Bug rtl-optimization/58034] New: glibc nptl/tst-cleanup2 fail due to scheduling

[amodra at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58034

            Bug ID: 58034
           Summary: glibc nptl/tst-cleanup2 fail due to scheduling
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: amodra at gmail dot com

Created attachment 30575
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30575&action=edit
preprocessed test case

nprl/tst-cleanup2 fails when compiled with -O2 -mcpu=power6 due to sched1
moving an assignment to a REG over code that traps.

The relevant test case source:

  if (setjmp (jmpbuf))
    {
      puts ("Exiting main...");
      return 0;
    }

  sprintf (p, "This should segv\n");

  return 1;
}

The sprintf is optimised to three loads and stores.  The problem occurs due to
the assignment of 1 to the REG holding the function return value being
scheduled before the sprintf expansion.

[Bug rtl-optimization/58034] glibc nptl/tst-cleanup2 fail due to scheduling

[dje at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58034

David Edelsohn <dje at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-07-31
                 CC|                            |dje at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from David Edelsohn <dje at gcc dot gnu.org> ---
Confirmed.

[Bug rtl-optimization/58034] glibc nptl/tst-cleanup2 fail due to scheduling

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58034

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
  if (_setjmp (jmpbuf))

I wonder if this is due to _setjmp not being marked as return twice.

[Bug rtl-optimization/58034] glibc nptl/tst-cleanup2 fail due to scheduling

[dje at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58034

--- Comment #3 from David Edelsohn <dje at gcc dot gnu.org> ---
> I wonder if this is due to _setjmp not being marked as return twice.

Is that a missing decoration in the GLIBC declaration?

[Bug rtl-optimization/58034] glibc nptl/tst-cleanup2 fail due to scheduling

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58034

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #2)
>   if (_setjmp (jmpbuf))
> 
> I wonder if this is due to _setjmp not being marked as return twice.

Looking at special_function_p, it should return ECF_RETURNS_TWICE for that decl
if I read the code correctly as it disregards the _ and then matches setjmp.

[Bug rtl-optimization/58034] glibc nptl/tst-cleanup2 fail due to scheduling

[amodra at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58034

Alan Modra <amodra at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |4.7.2
      Known to fail|                            |4.8.1, 4.8.2, 4.9.0

--- Comment #5 from Alan Modra <amodra at gmail dot com> ---
This somewhat reduced testcase fails with mainline.

#include <setjmp.h>
#include <signal.h>

static sigjmp_buf jmpbuf;

static void
sig_handler (int signo)
{
  siglongjmp (jmpbuf, 1);
}

int
main (void)
{
  char *p = 0;
  struct sigaction sa;

  sa.sa_handler = sig_handler;
  sigemptyset (&sa.sa_mask);
  sa.sa_flags = SA_SIGINFO;

  if (sigaction (SIGSEGV, &sa, 0))
    return 1;

  if (setjmp (jmpbuf))
    return 0;
  __builtin_memcpy (p, "abc", 4);
  return 1;
}

[Bug rtl-optimization/58034] [4.8/4.9 Regression] glibc nptl/tst-cleanup2 fail due to scheduling

[joseph at codesourcery dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58034

--- Comment #6 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
On Wed, 31 Jul 2013, amodra at gmail dot com wrote:

> The relevant test case source:
> 
>   if (setjmp (jmpbuf))
>     {
>       puts ("Exiting main...");
>       return 0;
>     }
> 
>   sprintf (p, "This should segv\n");
> 
>   return 1;
> }
> 
> The sprintf is optimised to three loads and stores.  The problem occurs due to
> the assignment of 1 to the REG holding the function return value being
> scheduled before the sprintf expansion.

Well, in valid code this sprintf can't trap (sprintf using glibc 
extensions to register format extensions might).  Optimizing to three 
loads and stores, and then scheduling them, seems a valid optimization to 
me.  Does -fnon-call-exceptions help?  (Though I'd prefer 
-fno-builtin-sprintf as a fix for the glibc test.)

[Bug rtl-optimization/58034] [4.8/4.9 Regression] glibc nptl/tst-cleanup2 fail due to scheduling

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58034

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |jakub at gcc dot gnu.org
         Resolution|---                         |INVALID

--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I agree this looks like a glibc test issue rather than gcc bug.