[Bug gcov-profile/42660] buggy instrumentation - return statement never executed.

["rguenth at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #2 from rguenth at gcc dot gnu dot org  2010-01-08 16:21 -------
Confirmed on trunk.  The return statement in bar() is not instrumented because
it is turned into a goto to the merged return statement by gimple lowering
and we are not good preserving gotos if they turn into fallthru edges later
(which in this case happens during EH lowering).

We go from

  [t.c : 11:15] s.10 = <retval>;
  [t.c : 11:15] std::basic_string<char>::basic_string (s.10);
  [t.c : 13:11] try
    {
      [t.c : 12:14] D.12564 = foo (i);
      [t.c : 12:14] D.12565 = (int) D.12564;
      [t.c : 12:14] s.11 = <retval>;
      [t.c : 12:15] std::basic_string<char>::operator+= (s.11, D.12565);
      [t.c : 13:10] goto <D.12568>;
    }
  catch
    {
      [t.c : 11:15] s.12 = <retval>;
      [t.c : 11:15] std::basic_string<char>::~basic_string (s.12);
    }
  <D.12568>:
  return <retval>;

to

  [t.c : 11:15] s.10 = <retval>;
  [t.c : 11:15] std::basic_string<char>::basic_string (s.10);
  [t.c : 12:14] D.12564 = foo (i);
  [t.c : 12:14] D.12565 = (int) D.12564;
  [t.c : 12:14] s.11 = <retval>;
  [t.c : 12:15] std::basic_string<char>::operator+= (s.11, D.12565);
  [t.c : 13:10] goto <D.12568>;
  <D.12568>:
  return <retval>;
  <D.12569>:
  [t.c : 11:15] s.12 = <retval>;
  [t.c : 11:15] std::basic_string<char>::~basic_string (s.12);
  resx 1

to

<bb 2>:
  [t.c : 11:15] s.10 = <retval>;
  [t.c : 11:15] std::basic_string<char>::basic_string (s.10);
  [t.c : 12:14] D.12564 = foo (i);
  [t.c : 12:14] D.12565 = (int) D.12564;
  [t.c : 12:14] s.11 = <retval>;
  [t.c : 12:15] std::basic_string<char>::operator+= (s.11, D.12565);

<bb 3>:
  return <retval>;

<L1>:
  [t.c : 11:15] s.12 = <retval>;
  [t.c : 11:15] std::basic_string<char>::~basic_string (s.12);
  resx 1

We could special-case this particular case of CFG construction of a fallthru
to the return block with just a single predecessor to copy the location
from the fallthru goto, but ... that looks like a hack.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2010-01-08 16:21:48
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42660