[Bug c++/53294] New: Optimize out some exception code

[Bug c++/53294] New: Optimize out some exception code

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53294

             Bug #: 53294
           Summary: Optimize out some exception code
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: glisse@gcc.gnu.org


Hello,

it would be great if the compiler could transform code like:

  try {
    throw 42;
  } catch(...) {
  }

into nothing (or in practice into a simple goto, since there will be code
around). It already knows to remove the code after "throw", it could statically
check that the exception will be caught locally and thus skip the __cxa_throw,
__cxa_begin_catch game.

Filed as C++ front-end, but it might be for the middle-end, since it would be
best if this optimization happened after inlining.

[Bug c++/53294] Optimize out some exception code

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53294

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-05-09
     Ever Confirmed|0                           |1

--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-05-09 13:55:37 UTC ---
Certainly interesting.  We lower things too early into __cxa calls though
(I think) to make this work easily.

Consider cases like

struct X { int i; };

int foo (void)
{
  try {
    X x;
    x.i = 5;
    throw x;
  } catch (X& x) {
      return x.i;
  } catch (...) {
   return 0;
   }
}

[Bug c++/53294] Optimize out some exception code

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53294

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |DUPLICATE
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=38658
             Status|NEW                         |RESOLVED

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup of bug 38658.

*** This bug has been marked as a duplicate of bug 38658 ***