From: Masahiro Yamada <masahiroy@kernel.org>
To: Mark Wielaard <mark@klomp.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Michal Marek <michal.lkml@markovi.net>,
Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
Ian Rogers <irogers@google.com>, Andi Kleen <andi@firstfloor.org>,
linux-toolchains@vger.kernel.org,
Nick Desaulniers <ndesaulniers@google.com>,
Segher Boessenkool <segher@kernel.crashing.org>,
Florian Weimer <fw@deneb.enyo.de>,
Sedat Dilek <sedat.dilek@gmail.com>
Subject: Re: [PATCH V2] Only add -fno-var-tracking-assignments workaround for old GCC versions.
Date: Wed, 21 Oct 2020 00:27:52 +0900 [thread overview]
Message-ID: <CAK7LNATi5X_UjeEwP_+BJETOoVHZTxdh3e=e2SJZbvH69MHM+g@mail.gmail.com> (raw)
In-Reply-To: <20201017120135.4004-1-mark@klomp.org>
On Sat, Oct 17, 2020 at 9:02 PM Mark Wielaard <mark@klomp.org> wrote:
>
> Some old GCC versions between 4.5.0 and 4.9.1 might miscompile code
> with -fvar-tracking-assingments (which is enabled by default with -g -O2).
> commit 2062afb4f added -fno-var-tracking-assignments unconditionally to
> work around this. But newer versions of GCC no longer have this bug, so
> only add it for versions of GCC before 5.0. This allows various tools
> such as a perf probe or gdb debuggers or systemtap to resolve variable
> locations using dwarf locations in more code.
>
> Changes in V2:
> - Update commit message explaining purpose.
> - Explicitly mention GCC version in comment.
> - Wrap workaround in ifdef CONFIG_CC_IS_GCC
>
> Signed-off-by: Mark Wielaard <mark@klomp.org>
> Acked-by: Ian Rogers <irogers@google.com>
> Reviewed-by: Andi Kleen <andi@firstfloor.org>
> Cc: linux-toolchains@vger.kernel.org
> Cc: Nick Desaulniers <ndesaulniers@google.com>
> Cc: Segher Boessenkool <segher@kernel.crashing.org>
> Cc: Florian Weimer <fw@deneb.enyo.de>
> Cc: Sedat Dilek <sedat.dilek@gmail.com>
> ---
Applied to linux-kbuild. Thanks.
> Makefile | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index 51540b291738..964754b4cedf 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -813,7 +813,11 @@ KBUILD_CFLAGS += -ftrivial-auto-var-init=zero
> KBUILD_CFLAGS += -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
> endif
>
> -DEBUG_CFLAGS := $(call cc-option, -fno-var-tracking-assignments)
> +# Workaround for GCC versions < 5.0
> +# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61801
> +ifdef CONFIG_CC_IS_GCC
> +DEBUG_CFLAGS := $(call cc-ifversion, -lt, 0500, $(call cc-option, -fno-var-tracking-assignments))
> +endif
>
> ifdef CONFIG_DEBUG_INFO
> ifdef CONFIG_DEBUG_INFO_SPLIT
> --
> 2.18.4
>
--
Best Regards
Masahiro Yamada
next prev parent reply other threads:[~2020-10-20 15:40 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-06 13:17 Additional debug info to aid cacheline analysis Peter Zijlstra
2020-10-06 19:00 ` Arnaldo Carvalho de Melo
2020-10-08 5:58 ` Stephane Eranian
2020-10-08 7:02 ` Peter Zijlstra
2020-10-08 9:32 ` Mark Wielaard
2020-10-08 21:23 ` Andi Kleen
2020-10-10 20:58 ` Mark Wielaard
2020-10-10 21:51 ` Mark Wielaard
[not found] ` <20201010220712.5352-1-mark@klomp.org>
2020-10-10 22:21 ` [PATCH] Only add -fno-var-tracking-assignments workaround for old GCC versions Ian Rogers
2020-10-12 18:59 ` Nick Desaulniers
2020-10-12 19:12 ` Mark Wielaard
2020-10-14 15:31 ` Sedat Dilek
2020-10-14 11:01 ` Mark Wielaard
2020-10-14 15:17 ` Andi Kleen
2020-10-17 12:01 ` [PATCH V2] " Mark Wielaard
2020-10-19 19:30 ` Nick Desaulniers
2020-10-20 15:27 ` Masahiro Yamada [this message]
2020-10-10 22:33 ` [PATCH] " Mark Wielaard
2020-10-11 11:04 ` Additional debug info to aid cacheline analysis Segher Boessenkool
2020-10-11 12:15 ` Florian Weimer
2020-10-11 12:23 ` Mark Wielaard
2020-10-11 12:28 ` Florian Weimer
2020-10-30 5:26 ` Namhyung Kim
2020-10-30 9:16 ` Mark Wielaard
2020-10-30 10:10 ` Peter Zijlstra
2020-11-02 8:27 ` Masami Hiramatsu
2020-11-03 4:22 ` Namhyung Kim
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