linux-kernel - RE: [PATCH] compiler/gcc: Raise minimum GCC version for kernel builds to 4.8

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Message-ID: <04ca01d633a8$9abb8070$d0328150$@codeaurora.org>
Date:   Tue, 26 May 2020 16:57:07 -0500
From:   "Brian Cain" <bcain@...eaurora.org>
To:     "'Nick Desaulniers'" <ndesaulniers@...gle.com>,
        "'Guenter Roeck'" <linux@...ck-us.net>
Cc:     "'Will Deacon'" <will@...nel.org>, <linux-hexagon@...r.kernel.org>,
        "'LKML'" <linux-kernel@...r.kernel.org>,
        "'Thomas Gleixner'" <tglx@...utronix.de>,
        "'Masahiro Yamada'" <masahiroy@...nel.org>,
        "'Peter Zijlstra'" <peterz@...radead.org>,
        "'Arnd Bergmann'" <arnd@...db.de>, <sidneym@...eaurora.org>
Subject: RE: [PATCH] compiler/gcc: Raise minimum GCC version for kernel builds to 4.8

> -----Original Message-----
> From: linux-hexagon-owner@...r.kernel.org <linux-hexagon-
> owner@...r.kernel.org> On Behalf Of Nick Desaulniers
...
> On Tue, May 26, 2020 at 8:30 AM Guenter Roeck <linux@...ck-us.net> wrote:
> >
> > On Mon, May 11, 2020 at 09:41:37PM +0100, Will Deacon wrote:
> > > It is very rare to see versions of GCC prior to 4.8 being used to
> > > build the mainline kernel. These old compilers are also known to
> > > have codegen issues which can lead to silent miscompilation:
> > >
> > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145
> > >
> > > Raise the minimum GCC version to 4.8 for building the kernel and
> > > remove some tautological Kconfig dependencies as a consequence.
> >
> > My hexagon compiler is v4.6.1, and I have been unable to find a more
> > recent version. Does anyone happen to have a pointer to a hexagon
> > toolchain with gcc 4.8 or later ?
> 
> IIUC, hexagon moved to LLVM, though that target still has issues building the
> kernel.
> https://github.com/ClangBuiltLinux/linux/issues?q=is%3Aopen+is%3Aissue+lab
> el%3A%22%5BARCH%5D+hexagon%22

Indeed, we did move to llvm.  The build works with the clang_rt-builtins lib.  But that issue indicates that it's an unnecessary wart to require that.  From what I understand, other arches contribute these builtins content to the kernel build, so we'll do the same.

I'll prioritize this update.

-Brian