linux-kernel - RE: [PATCH v4 1/2] arm: lib: xor-neon: remove unnecessary GCC

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Date:   Tue, 19 Jan 2021 22:04:20 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Adrian Ratiu' <adrian.ratiu@...labora.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
CC:     Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Russell King <linux@...linux.org.uk>,
        Ard Biesheuvel <ardb@...nel.org>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        "kernel@...labora.com" <kernel@...labora.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v4 1/2] arm: lib: xor-neon: remove unnecessary GCC < 4.6
 warning

From: Adrian Ratiu
> Sent: 19 January 2021 13:17
> To: linux-arm-kernel@...ts.infradead.org
> 
> Drop warning because kernel now requires GCC >= v4.9 after
> commit 6ec4476ac825 ("Raise gcc version requirement to 4.9")
> and clarify that -ftree-vectorize now always needs enabling
> for GCC by directly testing the presence of CONFIG_CC_IS_GCC.
...
> -#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
> +#ifdef CONFIG_CC_IS_GCC
>  #pragma GCC optimize "tree-vectorize"
> -#else

I thought that #pragma optimise was very likely to remove
a random subset of the command line parameters leading to
incorrect/unexpected code.

As such the extra option needs to passed in as a per source
file compiler option.

	David

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