linux-kernel - Re: [PATCH v2] mips: lib: uncached: fix non-standard usage of variable 'sp'

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Message-ID: <20201214152447.GC9149@alpha.franken.de>
Date:   Mon, 14 Dec 2020 16:24:47 +0100
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Anders Roxell <anders.roxell@...aro.org>
Cc:     natechancellor@...il.com, ndesaulniers@...gle.com,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH v2] mips: lib: uncached: fix non-standard usage of
 variable 'sp'

On Fri, Dec 11, 2020 at 11:24:37AM +0100, Anders Roxell wrote:
> When building mips tinyconfig with clang the following warning show up:
> 
> arch/mips/lib/uncached.c:45:6: warning: variable 'sp' is uninitialized when used here [-Wuninitialized]
>         if (sp >= (long)CKSEG0 && sp < (long)CKSEG2)
>             ^~
> arch/mips/lib/uncached.c:40:18: note: initialize the variable 'sp' to silence this warning
>         register long sp __asm__("$sp");
>                         ^
>                          = 0
> 1 warning generated.
> 
> Rework to make an explicit inline move, instead of the non-standard use
> of specifying registers for local variables. This is what's written
> from the gcc-10 manual [1] about specifying registers for local
> variables:
> 
> "6.47.5.2 Specifying Registers for Local Variables
> .................................................
> [...]
> 
> "The only supported use for this feature is to specify registers for
> input and output operands when calling Extended 'asm' (*note Extended
> Asm::).  [...]".
> 
> [1] https://docs.w3cub.com/gcc~10/local-register-variables
> Signed-off-by: Anders Roxell <anders.roxell@...aro.org>
> ---
>  arch/mips/lib/uncached.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

applied to mips-next.

Thomas.

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