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From: Nick Desaulniers <ndesaulniers@google.com>
Date: Thu, 31 Mar 2022 10:31:02 -0700
Message-ID: <CAKwvOdmbMPBOGvcZNURK6qMx8gm7dGFiWmtX_yXheEqQ8CNLsA@mail.gmail.com>
Subject: Re: [PATCH v5 0/3] bootconfig: Support embedding a bootconfig in
 kernel for non initrd boot
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>, Padmanabha Srinivasaiah <treasure4paddy@gmail.com>, 
	LKML <linux-kernel@vger.kernel.org>, Jonathan Corbet <corbet@lwn.net>, linux-doc@vger.kernel.org, 
	Randy Dunlap <rdunlap@infradead.org>, Sami Tolvanen <samitolvanen@google.com>, 
	Nathan Chancellor <nathan@kernel.org>, llvm@lists.linux.dev, 
	Masahiro Yamada <masahiroy@kernel.org>, 
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"

On Wed, Mar 30, 2022 at 6:45 PM Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> Hi Nick,
>
> On Wed, 30 Mar 2022 11:04:50 -0700
> Nick Desaulniers <ndesaulniers@google.com> wrote:
>
> >
> > Any chance we can use
> >
> > CFLAGS_REMOVE_<file>.o := $(CC_FLAGS_LTO)
> >
> > a la
> > commit d2dcd3e37475 ("x86, cpu: disable LTO for cpu.c")
>
> Hm, this looks good to me. Let me confirm that works.
> (Does this mean the bootconfig.o will be compiled to elf binary?)

I know we went with Masahiro's suggestion, which is clever and better,
but to answer this question; yes, under LTO, the linker can link
together inputs that are a mix of ELF object files (basically, no LTO
optimizations) with LLVM IR (w/ LTO optimizations between such files).
-- 
Thanks,
~Nick Desaulniers