From: Will Deacon <will.deacon@arm.com>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, mark.rutland@arm.com
Subject: Re: [PATCH] arm64: support __int128 on gcc 5+
Date: Tue, 31 Oct 2017 11:51:56 +0000 [thread overview]
Message-ID: <20171031115156.GF5584@arm.com> (raw)
In-Reply-To: <20171031114319.24436-1-Jason@zx2c4.com>
On Tue, Oct 31, 2017 at 12:43:19PM +0100, Jason A. Donenfeld wrote:
> Versions of gcc prior to gcc 5 emitted a __multi3 function call when
> dealing with TI types, resulting in failures when trying to link to
> libgcc, and more generally, horrible performance. However, since gcc 5,
> the compiler supports actually emitting fast instructions, which means
> we can at long last enable this option and receive the speedups.
>
> The gcc commit that added proper Aarch64 support is:
> https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=d1ae7bb994f49316f6f63e6173f2931e837a351d
>
> This commit appears to be part of the gcc 5 release.
>
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---
> arch/arm64/Makefile | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> index 939b310913cf..1f8a0fec6998 100644
> --- a/arch/arm64/Makefile
> +++ b/arch/arm64/Makefile
> @@ -53,6 +53,8 @@ KBUILD_AFLAGS += $(lseinstr) $(brokengasinst)
> KBUILD_CFLAGS += $(call cc-option,-mabi=lp64)
> KBUILD_AFLAGS += $(call cc-option,-mabi=lp64)
>
> +KBUILD_CFLAGS += $(call cc-ifversion, -ge, 0500, -DCONFIG_ARCH_SUPPORTS_INT128)
> +
> ifeq ($(CONFIG_CPU_BIG_ENDIAN), y)
> KBUILD_CPPFLAGS += -mbig-endian
> CHECKFLAGS += -D__AARCH64EB__
Which code in the kernel actually uses 128-bit types directly? I know we
have some unfortunate occurences in our headers (including uapi) for the
vector registers, but I thought we generally used asm or copy routines to
access those.
Are you seeing a performance issue without this?
Will
next prev parent reply other threads:[~2017-10-31 11:51 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-31 10:17 CONFIG_ARCH_SUPPORTS_INT128 for AArch64 Jason A. Donenfeld
2017-10-31 10:43 ` Mark Rutland
2017-10-31 11:17 ` Jason A. Donenfeld
2017-10-31 11:43 ` [PATCH] arm64: support __int128 on gcc 5+ Jason A. Donenfeld
2017-10-31 11:51 ` Will Deacon [this message]
2017-10-31 11:57 ` Jason A. Donenfeld
2017-10-31 12:17 ` Will Deacon
2017-10-31 12:18 ` Jason A. Donenfeld
2017-11-02 13:47 ` Will Deacon
2017-11-02 17:43 ` [PATCH v2] " Jason A. Donenfeld
2017-11-03 13:42 ` Will Deacon
2017-11-03 14:02 ` Ard Biesheuvel
2017-11-03 14:14 ` Jason A. Donenfeld
2017-11-03 14:18 ` [PATCH v3] " Jason A. Donenfeld
2017-11-06 9:31 ` [PATCH v4] " Jason A. Donenfeld
2017-11-06 15:59 ` Catalin Marinas
2017-11-06 16:14 ` Catalin Marinas
[not found] ` <CAHmME9p+ef-+fmdiO15LU7X3Sr-CDyngpPwKZN2FqOQmZNjLtg@mail.gmail.com>
2017-11-06 16:55 ` Ard Biesheuvel
2017-11-06 23:58 ` [PATCH v5] " Jason A. Donenfeld
2017-11-07 0:01 ` [PATCH v4] " Jason A. Donenfeld
2017-11-07 2:13 ` Will Deacon
2017-11-07 2:16 ` Jason A. Donenfeld
2017-11-02 20:24 ` [PATCH] " Jason A. Donenfeld
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