From: "H. Peter Anvin" <hpa@zytor.com>
To: Michael Davidson <md@google.com>, Michal Marek <mmarek@suse.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
"David S. Miller" <davem@davemloft.net>,
Shaohua Li <shli@kernel.org>
Cc: Alexander Potapenko <glider@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
Matthias Kaehlcke <mka@chromium.org>,
x86@kernel.org, linux-kbuild@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
linux-raid@vger.kernel.org
Subject: Re: [PATCH 2/7] Makefile, x86, LLVM: disable unsupported optimization flags
Date: Fri, 17 Mar 2017 14:32:10 -0700 [thread overview]
Message-ID: <ad94b647-4ba0-4ae9-be8f-6fe7e9406def@zytor.com> (raw)
In-Reply-To: <20170317001520.85223-3-md@google.com>
On 03/16/17 17:15, Michael Davidson wrote:
> Unfortunately, while clang generates a warning about these flags
> being unsupported it still exits with a status of 0 so we have
> to explicitly disable them instead of just using a cc-option check.
>
> Signed-off-by: Michael Davidson <md@google.com>
> ---
> Makefile | 2 ++
> arch/x86/Makefile | 2 ++
> 2 files changed, 4 insertions(+)
>
> diff --git a/Makefile b/Makefile
> index b21fd0ca2946..5e97e5fc1eea 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -629,7 +629,9 @@ ARCH_AFLAGS :=
> ARCH_CFLAGS :=
> include arch/$(SRCARCH)/Makefile
>
> +ifneq ($(cc-name),clang)
> KBUILD_CFLAGS += $(call cc-option,-fno-delete-null-pointer-checks,)
> +endif
> KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,)
>
> ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> index 2d449337a360..894a8d18bf97 100644
> --- a/arch/x86/Makefile
> +++ b/arch/x86/Makefile
> @@ -87,11 +87,13 @@ else
> KBUILD_AFLAGS += -m64
> KBUILD_CFLAGS += -m64
>
> +ifneq ($(cc-name),clang)
> # Align jump targets to 1 byte, not the default 16 bytes:
> KBUILD_CFLAGS += -falign-jumps=1
>
> # Pack loops tightly as well:
> KBUILD_CFLAGS += -falign-loops=1
> +endif
>
> # Don't autogenerate traditional x87 instructions
> KBUILD_CFLAGS += $(call cc-option,-mno-80387)
>
NAK. Fix your compiler, or use a wrapper script or something. It is
absolutely *not* acceptable to disable this since future versions of
clang *should* support that.
That being said, it might make sense to look for a key pattern like
"(un|not )supported" on stderr the try-run macro. Is there really no
-Wno- or -Werror= option to turn off this craziness?
-hpa
next prev parent reply other threads:[~2017-03-17 21:43 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-17 0:15 [PATCH 0/7] LLVM: make x86_64 kernel build with clang Michael Davidson
2017-03-17 0:15 ` [PATCH 1/7] Makefile, LLVM: add -no-integrated-as to KBUILD_[AC]FLAGS Michael Davidson
2017-04-03 22:49 ` Matthias Kaehlcke
2017-04-21 7:49 ` Masahiro Yamada
2017-03-17 0:15 ` [PATCH 2/7] Makefile, x86, LLVM: disable unsupported optimization flags Michael Davidson
2017-03-17 21:32 ` H. Peter Anvin [this message]
2017-03-17 21:34 ` H. Peter Anvin
2017-04-05 18:08 ` Masahiro Yamada
2017-04-05 19:01 ` Matthias Kaehlcke
2017-04-05 19:11 ` Michael Davidson
2017-04-10 14:54 ` Masahiro Yamada
2017-03-17 0:15 ` [PATCH 3/7] x86, LLVM: suppress clang warnings about unaligned accesses Michael Davidson
2017-03-17 23:50 ` hpa
2017-04-03 23:01 ` Matthias Kaehlcke
2017-04-13 23:14 ` Matthias Kaehlcke
2017-04-13 23:55 ` H. Peter Anvin
2017-04-14 0:23 ` Matthias Kaehlcke
2017-04-14 5:30 ` hpa
2017-03-17 0:15 ` [PATCH 4/7] x86, boot, LLVM: #undef memcpy etc in string.c Michael Davidson
2017-06-22 22:31 ` Matthias Kaehlcke
2017-06-22 22:37 ` H. Peter Anvin
2017-06-30 18:32 ` Matthias Kaehlcke
2017-03-17 0:15 ` [PATCH 5/7] x86, boot, LLVM: Use regparm=0 for memcpy and memset Michael Davidson
2017-03-17 12:08 ` Peter Zijlstra
2017-06-22 22:38 ` H. Peter Anvin
2017-03-17 0:15 ` [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Michael Davidson
2017-03-17 12:08 ` Peter Zijlstra
2017-03-17 12:31 ` Alexander Potapenko
2017-03-17 12:32 ` Alexander Potapenko
2017-03-17 18:03 ` Borislav Petkov
2017-03-17 18:47 ` Dmitry Vyukov
2017-03-17 18:57 ` Borislav Petkov
2017-03-17 19:05 ` Dmitry Vyukov
2017-03-17 19:26 ` Peter Zijlstra
2017-03-17 19:29 ` Peter Zijlstra
2017-03-24 13:50 ` Dmitry Vyukov
2017-03-24 14:10 ` Peter Zijlstra
2017-03-24 14:22 ` Dmitry Vyukov
2017-03-18 0:41 ` Fengguang Wu
2017-03-17 12:44 ` Peter Zijlstra
2017-03-17 18:52 ` Michael Davidson
2017-03-17 19:27 ` Peter Zijlstra
2017-03-17 20:04 ` hpa
2017-03-24 13:47 ` Dmitry Vyukov
2017-03-24 14:09 ` Peter Zijlstra
2017-03-17 0:15 ` [PATCH 7/7] crypto, x86, LLVM: aesni - fix token pasting Michael Davidson
2017-04-03 23:14 ` Matthias Kaehlcke
2017-03-17 8:17 ` [PATCH 0/7] LLVM: make x86_64 kernel build with clang Dmitry Vyukov
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