linux-kernel - Re: [PATCH 1/3] Kconfig.debug: simplify the dependency of DEBUG_INFO

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Message-ID: <CAK7LNAT2gSqwKEwXUQ2V7TsdkGiN3bNdCyEVfi7axsb3rAEWzg@mail.gmail.com>
Date:   Tue, 4 Oct 2022 04:56:28 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>
Subject: Re: [PATCH 1/3] Kconfig.debug: simplify the dependency of DEBUG_INFO_DWARF4/5

On Tue, Oct 4, 2022 at 1:53 AM Nick Desaulniers <ndesaulniers@...gle.com> wrote:
>
> On Sun, Oct 2, 2022 at 11:11 AM Masahiro Yamada <masahiroy@...nel.org> wrote:
> >
> > Commit c0a5c81ca9be ("Kconfig.debug: drop GCC 5+ version check for
> > DWARF5") could have cleaned up the code a bit deeper.
> >
> > "CC_IS_CLANG &&" is unneeded. No functional change is intended.
>
> This implies that there are only 2 compilers capable of building the
> kernel; consider also removing
> include/linux/compiler-intel.h
> if ICC is no longer supported.  Otherwise, what implications does this
> patch have for ICC?




I am just doing logical simplification in general.

When A and B are bool,

   !A || (A && B)

is always redundant.
It can be simplified into

   !A || B



So, this patch is irrelevant to the presence of the third compiler, ICC.

Such an implication happened in commit c0a5c81ca9be.
When you dropped GCC 5+ check, you converted
"GCC_VERSION >= 50000" into "!CC_IS_CLANG" instead of "CC_IS_GCC".


"CC_IS_GCC" and "!CC_IS_CLANG" are not equivalent,
but a lot of code already expects that, and nobody asked
"We have the third compiler, so do we need CC_IS_ICC?"



I agree that we can drop ICC support, but I want to
point out that ICC is DON'T_CARE to my patch.








> >
> > Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> > ---
> >
> >  lib/Kconfig.debug | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > index d3e5f36bb01e..f4b2165f24db 100644
> > --- a/lib/Kconfig.debug
> > +++ b/lib/Kconfig.debug
> > @@ -264,7 +264,7 @@ config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
> >  config DEBUG_INFO_DWARF4
> >         bool "Generate DWARF Version 4 debuginfo"
> >         select DEBUG_INFO
> > -       depends on !CC_IS_CLANG || (CC_IS_CLANG && (AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)))
> > +       depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)
> >         help
> >           Generate DWARF v4 debug info. This requires gcc 4.5+, binutils 2.35.2
> >           if using clang without clang's integrated assembler, and gdb 7.0+.
> > @@ -276,7 +276,7 @@ config DEBUG_INFO_DWARF4
> >  config DEBUG_INFO_DWARF5
> >         bool "Generate DWARF Version 5 debuginfo"
> >         select DEBUG_INFO
> > -       depends on !CC_IS_CLANG || (CC_IS_CLANG && (AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)))
> > +       depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)
> >         help
> >           Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc
> >           5.0+ accepts the -gdwarf-5 flag but only had partial support for some
> > --
> > 2.34.1
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers



-- 
Best Regards
Masahiro Yamada