[Bug debug/44832] [4.6 Regression] -fcompare-debug failure for C++ i386.c

[amylaar at gcc dot gnu dot org]

------- Comment #30 from amylaar at gcc dot gnu dot org  2010-07-07 17:27 -------
(In reply to comment #28)
> No, the culprit is loop header copying which causes

I also see changes in the MEM_* after loop header copying.
It happens during the second call of copy_loop_header.  Alas,
it seems that copy_loop_header is innocent, because it gets
different freed ssa name versions for debug / no debug compilation:

Debug:

Breakpoint 5, copy_loop_headers () at ../../gcc/gcc/tree-ssa-loop-ch.c:140
140       loop_optimizer_init (LOOPS_HAVE_PREHEADERS
(gdb) call debug_tree(cfun->gimple_df->free_ssanames)
 <ssa_name 0xb7db20f0 nothrow var <var_decl 0xb7d97060 retval.3>def_stmt 

    version 87 in-free-list>
(gdb) call debug_tree(cfun->gimple_df->free_ssanames->common.chain)
 <ssa_name 0xb7dacfc0 nothrow var <var_decl 0xb7d91d80 retval.1>def_stmt 

    version 83 in-free-list>

No debug:

Breakpoint 5, copy_loop_headers () at ../../gcc/gcc/tree-ssa-loop-ch.c:140
140       loop_optimizer_init (LOOPS_HAVE_PREHEADERS
(gdb) call debug_tree(cfun->gimple_df->free_ssanames)
 <ssa_name 0xb7da5f90 nothrow var <var_decl 0xb7d95060 retval.3>def_stmt 

    version 87 in-free-list>
(gdb) call debug_tree(cfun->gimple_df->free_ssanames->common.chain)
 <ssa_name 0xb7da5db0 nothrow var <var_decl 0xb7d90d80 retval.1>def_stmt 

    version 82 in-free-list>


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44832