[Bug lto/65475] [5 Regression] ICE in odr_vtable_hasher::equal (Segmentation fault)

["hubicka at ucw dot cz" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65475

--- Comment #5 from Jan Hubicka <hubicka at ucw dot cz> ---
Hmm, yeah, in one unit base is virutal and in other it is not.  Perhaps just
dropping
that sanity check or restricting it to non-odr-violation-reported....

Honza

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65475
> 
> --- Comment #4 from Martin Liška <marxin at gcc dot gnu.org> ---
> Unfortunately, there is another problem with applied patch:
> 
> $ cat 1.ii
> namespace std {
> class exception {};
> class runtime_error : exception {
>   virtual char m_fn1();
> } a;
> }
> 
> $ cat 2.ii
> namespace std {
> class exception {
>   virtual char m_fn1();
> };
> class runtime_error : exception {
> } a;
> }
> 
> $ g++ 1.ii 2.ii -flto -O1
> /home/marxin/Programming/bin/gcc/bin/ld: error: /tmp/cc7v39VO.o: multiple
> definition of 'std::a'
> /home/marxin/Programming/bin/gcc/bin/ld: /tmp/ccJ8pPM4.o: previous definition
> here
> 2.ii:2:7: warning: type ???struct exception??? violates one definition rule [-Wodr]
>  class exception {
>        ^
> 1.ii:2:7: note: a type with different virtual table pointers is defined in
> another translation unit
>  class exception {};
>        ^
> 2.ii:2:7: warning: type ???struct exception??? violates one definition rule [-Wodr]
>  class exception {
>        ^
> 1.ii:2:7: note: a type with different bases is defined in another translation
> unit
>  class exception {};
>        ^
> 1.ii:3:7: warning: type ???struct runtime_error??? violates one definition rule
> [-Wodr]
>  class runtime_error : exception {
>        ^
> 2.ii:5:7: note: a type with different virtual table pointers is defined in
> another translation unit
>  class runtime_error : exception {
>        ^
> lto1: internal compiler error: in add_type_duplicate, at ipa-devirt.c:1575
> 0x77c43c add_type_duplicate
>     ../../gcc/ipa-devirt.c:1573
> 0x77c43c get_odr_type(tree_node*, bool)
>     ../../gcc/ipa-devirt.c:1772
> 0x77d25c register_odr_type(tree_node*)
>     ../../gcc/ipa-devirt.c:1848
> 0x5b43d6 lto_read_decls
>     ../../gcc/lto/lto.c:1946
> 0x5b4d7b lto_file_finalize
>     ../../gcc/lto/lto.c:2236
> 0x5b4d7b lto_create_files_from_ids
>     ../../gcc/lto/lto.c:2246
> 0x5b4d7b lto_file_read
>     ../../gcc/lto/lto.c:2287
> 0x5b4d7b read_cgraph_and_symbols
>     ../../gcc/lto/lto.c:2992
> 0x5b4d7b lto_main()
>     ../../gcc/lto/lto.c:3462
> 
> 
> Thanks,
> Martin
> 
> -- 
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From: "hubicka at ucw dot cz" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/65492] Bad optimization in -O3 due to if-conversion and/or unrolling
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ide492

--- Comment #7 from Jan Hubicka <hubicka at ucw dot cz> ---
> https://gcc.gnu.org/bugzilla/show_bug.cgi?ide492
>
> Richard Biener <rguenth at gcc dot gnu.org> changed:
>
>            What    |Removed                     |Added
> ----------------------------------------------------------------------------
>                  CC|                            |hubicka at gcc dot gnu.org
>
> --- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
> --param max-peel-branches default of 32 seems to be quite high.  For this
> loop we have two branches on the hot path and 4 times unrolling.
>
> Honza - how did you arrive at the default of 32?  Shouldn't that depend
> on the number of other stmts thus rather look at branch density?

In https://gcc.gnu.org/ml/gcc-patches/2012-10/msg02716.html I claim value
around 32 is needed for apply. (not that I would recall that)

I do not have really strong opinion concerning the branch density.

Honza