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From: Masahiro Yamada <>
To: Nick Desaulniers <>
Cc: Nathan Chancellor <>,
	Miguel Ojeda <>,
	Fangrui Song <>,
	Michal Marek <>,
	Arnd Bergmann <>,
	Linux Kernel Mailing List <>,
	Linux Kbuild mailing list <>,
	clang-built-linux <>,
	Geert Uytterhoeven <>,
	Christoph Hellwig <>,
	Linus Torvalds <>
Subject: Re: [PATCH v3 2/2] Makefile: infer CROSS_COMPILE from SRCARCH for CC=clang LLVM_IAS=1
Date: Sat, 31 Jul 2021 00:15:22 +0900	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Fri, Jul 30, 2021 at 9:19 AM Nick Desaulniers
<> wrote:
> On Thu, Jul 29, 2021 at 2:00 PM Nathan Chancellor <> wrote:
> >
> > While I understand that the LLVM=1 LLVM_IAS=1 case works perfectly fine
> > with this series, I am of the belief that making it work for CC=clang
> > LLVM_IAS=1 is a mistake because there is no way for that configuration
> > to work for cross compiling without CROSS_COMPILE.
> So with v3 of this change, rather than:
> $ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make CC=clang -j72
> If you wanted to omit CROSS_COMPILE, you'd need:
> $ ARCH=arm64 make CC=clang LLVM_IAS=1 LD=ld.lld OBJCOPY=llvm-objcopy
> STRIP=llvm-strip
> or
> $ ARCH=arm64 make CC=clang LLVM_IAS=1 LD=aarch64-linux-gnu-ld
> OBJCOPY=aarch64-linux-gnu-objcopy STRIP=aarch64-linux-gnu-strip


  $ ARCH=arm64 make LLVM=1 LLVM_IAS=1

still works.

> That's straight up worse IMO and defeats the purpose of "shortening
> the command line," which should be the goal.  Not "making CC=clang
> maximally flexible."  We don't want folks generally using CC=clang;
> preferably they'd use LLVM=1.  I need to rewrite our docs to make that
> more explicit and straightforward.  And if folks would prefer to use
> CC=clang for whatever reason, let them explicitly state CROSS_COMPILE
> then.
> So I agree with Nathan, and hope Masahiro will reconsider that perhaps
> the v2 variant that required LLVM=1 maybe makes more sense.

We can always infer the target triple from ARCH unless CROSS_COMPILE is given.

Doing this all the time makes nothing wrong.

"Whether CROSS_COMPILE is unneeded" is a different thing.

> Either way, I need to fix the comment in the new script, commit
> message, and docs, so v4 is necessary.
> I'm tempted to add a rewrite of our docs to say "just use LLVM=1"
> front and center, then get into finer grain details below, moving this
> second patch to be the third in a series.  Let's see what Masahiro's
> thoughts are though first. (I do appreciate them, even when I
> disagree).

I am not sure about that.

LLVM=1 is a very strong all-or-nothing flag,
but technically there is no reason to force it.

(At least, target-tools and host-tools look
independent to each other to me)

When you send v4, one more request:
Please drop LLVM_IAS=1 check as well.

Best Regards
Masahiro Yamada

  parent reply	other threads:[~2021-07-30 15:16 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-29 16:50 [PATCH v3 0/2] infer CROSS_COMPILE from SRCARCH for CC=clang LLVM_IAS=1 Nick Desaulniers
2021-07-29 16:50 ` [PATCH v3 1/2] Makefile: move initial clang flag handling into scripts/Makefile.clang Nick Desaulniers
2021-07-29 16:50 ` [PATCH v3 2/2] Makefile: infer CROSS_COMPILE from SRCARCH for CC=clang LLVM_IAS=1 Nick Desaulniers
2021-07-29 19:40   ` Arnd Bergmann
2021-07-29 21:00   ` Nathan Chancellor
2021-07-30  0:19     ` Nick Desaulniers
2021-07-30  6:50       ` Miguel Ojeda
2021-07-30 15:15       ` Masahiro Yamada [this message]
2021-07-30 15:10     ` Masahiro Yamada

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