Re: [PATCH] Put cleanups of cleanups after cleanups (PR gcov-profile/64634)

[Jeff Law]

On 02/18/15 11:40, Jakub Jelinek wrote:

Hi!

Richard's GIMPLE EH rewrite in r151696 regressed following testcase.
The problem is that when lowering:
   [gcov-15.C:14:5] try
     {
       [gcov-15.C:18:12] D.2335 = __cxa_allocate_exception (4);
       [gcov-15.C:18:12] try
         {
           [gcov-15.C:18:12] [gcov-15.C:18:12] MEM[(int *)D.2335] = 5;
         }
       catch
         {
           [gcov-15.C:18:11] __cxa_free_exception (D.2335);
         }
       [gcov-15.C:18:11] __cxa_throw (D.2335, &_ZTIi, 0B);
     }
   catch
     {
       [gcov-15.C:20:3] catch (NULL)
         {
           [gcov-15.C:20:3] try
             {
               [gcov-15.C:20:10] D.2340 = __builtin_eh_pointer (0);
               [gcov-15.C:20:10] __cxa_begin_catch (D.2340);
               [gcov-15.C:22:15] catchEx ();
             }
           finally
             {
               [gcov-15.C:20:10] __cxa_end_catch ();
             }
         }
     }
we put the cleanup of the catch cleanup in front of the catch cleanup
in the EH sequence:
   [gcov-15.C:18:12] D.2335 = __cxa_allocate_exception (4);
   [gcov-15.C:18:12] [gcov-15.C:18:12] MEM[(int *)D.2335] = 5;
   [gcov-15.C:18:11] __cxa_throw (D.2335, &_ZTIi, 0B);
   <D.2345>:
   [gcov-15.C:24:1] D.2341 = 0;
   [gcov-15.C:24:1] goto <D.2342>;
   <D.2342>:
   [gcov-15.C:24:1] return D.2341;
   <D.2343>:
   [gcov-15.C:20:10] __cxa_end_catch ();
   resx 3
   <D.2346>:
   eh_dispatch 1
   resx 1
   <D.2344>:
   [gcov-15.C:20:10] D.2340 = __builtin_eh_pointer (1);
   [gcov-15.C:20:10] __cxa_begin_catch (D.2340);
   [gcov-15.C:22:15] catchEx ();
   [gcov-15.C:20:10] __cxa_end_catch ();
   goto <D.2345>;
and as the __cxa_end_catch () is the first bb for line 20,
gcov without -a considers that bb count as the one to be shown.
Before the gimple EH rewrite and also with this patch we instead
order the cleanup (__cxa_end_catch ()) after the __cxa_begin_catch ():
   [gcov-15.C:18:12] D.2335 = __cxa_allocate_exception (4);
   [gcov-15.C:18:12] [gcov-15.C:18:12] MEM[(int *)D.2335] = 5;
   [gcov-15.C:18:11] __cxa_throw (D.2335, &_ZTIi, 0B);
   <D.2345>:
   [gcov-15.C:24:1] D.2341 = 0;
   [gcov-15.C:24:1] goto <D.2342>;
   <D.2342>:
   [gcov-15.C:24:1] return D.2341;
   <D.2346>:
   eh_dispatch 1
   resx 1
   <D.2344>:
   [gcov-15.C:20:10] D.2340 = __builtin_eh_pointer (1);
   [gcov-15.C:20:10] __cxa_begin_catch (D.2340);
   [gcov-15.C:22:15] catchEx ();
   [gcov-15.C:20:10] __cxa_end_catch ();
   goto <D.2345>;
   <D.2343>:
   [gcov-15.C:20:10] __cxa_end_catch ();
   resx 3

Bootstrapped/regtested on x86_64-linux and i686-linux,
libstdc++.so.6 compiled without and with the patch is identical on
x86_64-linux.  The testcase also has identical generated code both at -O0
and -O2 when compiled without coverage.  Ok for trunk?

2015-02-18  Jakub Jelinek  <ja...@redhat.com>

        PR gcov-profile/64634
        * tree-eh.c (frob_into_branch_around): Fix up typos
        in function comment.
        (lower_catch): Put eh_seq resulting from EH lowering of
        the cleanup sequence after the cleanup rather than before
        it.

        * g++.dg/gcov/gcov-15.C: New test.

OK.
jeff