linux-kernel - Re: [PATCH] tools: drop nonsensical -O6

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Message-ID: <CAHaCkmejAaxvx_N9L1_uS5JpToLfBXPzGqs3C=8-Diy__=1sJA@mail.gmail.com>
Date: Wed, 11 Sep 2024 17:55:46 +0200
From: Jesper Juhl <jesperjuhl76@...il.com>
To: Sam James <sam@...too.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	"Liang, Kan" <kan.liang@...ux.intel.com>, Nathan Chancellor <nathan@...nel.org>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling <morbo@...gle.com>, 
	Justin Stitt <justinstitt@...gle.com>, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] tools: drop nonsensical -O6

Looks good to me.
Reviewed-by: Jesper Juhl <jesperjuhl76@...il.com>

On Sun, 8 Sept 2024 at 20:47, Sam James <sam@...too.org> wrote:
>
> -O6 is very much not-a-thing. Really, this should've been dropped
> entirely in 49b3cd306e60b9d889c775cb2ebb709f80dd8ae9 instead of just
> passing it for not-Clang.
>
> Just collapse it down to -O3, instead of "-O6 unless Clang, in which case
> -O3".
>
> GCC interprets > -O3 as -O3. It doesn't even interpret > -O3 as -Ofast,
> which is a good thing, given -Ofast has specific (non-)requirements for
> code built using it. So, this does nothing except look a bit daft.
>
> Remove the silliness and also save a few lines in the Makefiles accordingly.
>
> Signed-off-by: Sam James <sam@...too.org>
> ---
> I promise I'm not completely humourless, but given it's caused
> actual workarounds to be added for Clang, I don't think this is worth keeping.
>
> Plus it sort of propagates a silly myth that -O6 does anything.
>
>  tools/lib/api/Makefile     | 4 ----
>  tools/lib/subcmd/Makefile  | 4 +---
>  tools/lib/symbol/Makefile  | 4 ----
>  tools/perf/Makefile.config | 6 +-----
>  4 files changed, 2 insertions(+), 16 deletions(-)
>
> diff --git a/tools/lib/api/Makefile b/tools/lib/api/Makefile
> index 044860ac1ed1c..7f6396087b467 100644
> --- a/tools/lib/api/Makefile
> +++ b/tools/lib/api/Makefile
> @@ -31,11 +31,7 @@ CFLAGS := $(EXTRA_WARNINGS) $(EXTRA_CFLAGS)
>  CFLAGS += -ggdb3 -Wall -Wextra -std=gnu99 -U_FORTIFY_SOURCE -fPIC
>
>  ifeq ($(DEBUG),0)
> -ifeq ($(CC_NO_CLANG), 0)
>    CFLAGS += -O3
> -else
> -  CFLAGS += -O6
> -endif
>  endif
>
>  ifeq ($(DEBUG),0)
> diff --git a/tools/lib/subcmd/Makefile b/tools/lib/subcmd/Makefile
> index b87213263a5e0..6717b82fc5876 100644
> --- a/tools/lib/subcmd/Makefile
> +++ b/tools/lib/subcmd/Makefile
> @@ -38,10 +38,8 @@ endif
>
>  ifeq ($(DEBUG),1)
>    CFLAGS += -O0
> -else ifeq ($(CC_NO_CLANG), 0)
> -  CFLAGS += -O3
>  else
> -  CFLAGS += -O6
> +  CFLAGS += -O3
>  endif
>
>  # Treat warnings as errors unless directed not to
> diff --git a/tools/lib/symbol/Makefile b/tools/lib/symbol/Makefile
> index 13d43c6f92b4a..426b845edfacc 100644
> --- a/tools/lib/symbol/Makefile
> +++ b/tools/lib/symbol/Makefile
> @@ -31,11 +31,7 @@ CFLAGS := $(EXTRA_WARNINGS) $(EXTRA_CFLAGS)
>  CFLAGS += -ggdb3 -Wall -Wextra -std=gnu11 -U_FORTIFY_SOURCE -fPIC
>
>  ifeq ($(DEBUG),0)
> -ifeq ($(CC_NO_CLANG), 0)
>    CFLAGS += -O3
> -else
> -  CFLAGS += -O6
> -endif
>  endif
>
>  ifeq ($(DEBUG),0)
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index fa679db61f622..5d6b08a896150 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -238,11 +238,7 @@ endif
>
>  ifeq ($(DEBUG),0)
>  CORE_CFLAGS += -DNDEBUG=1
> -ifeq ($(CC_NO_CLANG), 0)
> -  CORE_CFLAGS += -O3
> -else
> -  CORE_CFLAGS += -O6
> -endif
> +CORE_CFLAGS += -O3
>  else
>    CORE_CFLAGS += -g
>    CXXFLAGS += -g
> --
> 2.46.0
>
>