[Bug target/113341] Using GCC as the bootstrap compiler breaks LLVM on 32-bit PowerPC

["xry111 at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113341

Xi Ruoyao <xry111 at gcc dot gnu.org> changed:

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                 CC|                            |xry111 at gcc dot gnu.org

--- Comment #12 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
(In reply to John Paul Adrian Glaubitz from comment #11)
> (In reply to John Paul Adrian Glaubitz from comment #10)
> > (In reply to Kewen Lin from comment #9)
> > > Since it's a breakage during stage2, it's concluded that some built stage1
> > > stuffs behave unexpectedly.  You probably can try to run regression testing
> > > just with stage1 compiler to see if there is any regression exposed.
> > > 
> > > If without any luck, then you probably have to isolate into one or several
> > > object files, since you have "objects" for "good" and "bad" stage1 compiler,
> > > you can be able to isolate some in between further. Once you get some
> > > isolated, you can probably get some hints it's a bug in LLVM source or gcc.
> > 
> > Thanks. This sounds like a good idea. I will try to identify the object
> > files that differ.
> 
> First result of the comparison is that Clang and GCC are building with
> different flags:
> 
> Clang-only flags: -Werror=unguarded-availability-new
> -Wc++98-compat-extra-semi -Wcovered-switch-default -Wnon-virtual-dtor
> -Wstring-conversion -Wmisleading-indentation
> 
> GCC-only flags:  -fno-lifetime-dse    -Wno-missing-field-initializers  
> -Wno-maybe-uninitialized -Wno-nonnull -Wno-class-memaccess
> -Wno-redundant-move -Wno-pessimizing-move    -Wno-comment
> -Wno-misleading-indentation
> 
> I'll upload the build results later to my cloud space if anyone wants to
> help debug as the diff between the two build folders is rather big.

-Wxxx shouldn't have an effect on code generation.  -fno-lifetime-dse is quite
intentional, see PR106943.