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Date: Mon, 30 Mar 2026 12:01:19 +0200
From: Nathan Chancellor <nathan@kernel.org>
To: Nicolas Schier <nsc@kernel.org>, Rong Xu <xur@google.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>,
	Nick Desaulniers <nick.desaulniers+lkml@gmail.com>,
	Bill Wendling <morbo@google.com>,
	Justin Stitt <justinstitt@google.com>,
	Miguel Ojeda <ojeda@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Alice Ryhl <aliceryhl@google.com>,
	Sami Tolvanen <samitolvanen@google.com>,
	"Mike Rapoport (Microsoft)" <rppt@kernel.org>,
	Rafael Aquini <aquini@redhat.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Stafford Horne <shorne@gmail.com>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	Piotr Gorski <piotrgorski@cachyos.org>,
	Venkat Rao Bagalkote <venkat88@linux.ibm.com>,
	Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
	Teresa Johnson <tejohnson@google.com>, linux-kernel@vger.kernel.org,
	linux-kbuild@vger.kernel.org, llvm@lists.linux.dev
Subject: Re: [PATCH v7 3/3] kbuild: distributed build support for Clang
 ThinLTO
Message-ID: <20260330100119.GA1953970@ax162>
References: <20260328011927.3569802-1-xur@google.com>
 <20260328011927.3569802-4-xur@google.com>
 <acmF7nvIh2nX5hjK@levanger>
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In-Reply-To: <acmF7nvIh2nX5hjK@levanger>

On Sun, Mar 29, 2026 at 10:05:02PM +0200, Nicolas Schier wrote:
> On Sat, Mar 28, 2026 at 01:19:27AM +0000, xur@google.com wrote:
> > diff --git a/Makefile b/Makefile
> > index 69ccf9b8507d..d474b6f0f212 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -1047,11 +1047,11 @@ export CC_FLAGS_SCS
> >  endif
> >  
> >  ifdef CONFIG_LTO_CLANG
> > -ifdef CONFIG_LTO_CLANG_THIN
> > +ifdef CONFIG_LTO_CLANG_FULL
> > +CC_FLAGS_LTO	:= -flto
> > +else
> >  CC_FLAGS_LTO	:= -flto=thin -fsplit-lto-unit
> >  KBUILD_LDFLAGS += $(call ld-option,--lto-whole-program-visibility -mllvm -always-rename-promoted-locals=false)
> > -else
> > -CC_FLAGS_LTO	:= -flto
> >  endif
> >  CC_FLAGS_LTO	+= -fvisibility=hidden
> >  
> 
> This hunk is just reordering but does not change any functionality,
> right?

It does, as CONFIG_LTO_CLANG_THIN and CONFIG_LTO_CLANG_THIN_DIST are two
distinct options. That said, this hunk still does not look right based
on Yonghong's comment?

  https://lore.kernel.org/044bebc0-d996-4be3-9330-a64195c19a84@linux.dev/

Rong, have you tested this with a recent version of LLVM? Or has support
for this flag been added to the distributed mode since Yonghong's
comment?

> Nathan, Piotr: your tags got dropped from v6 to v7.  Do you want to
> renew them?

Yes, once the above is sorted out.

Cheers,
Nathan