Re: [PATCH v4 1/2] arm: lib: xor-neon: remove unnecessary GCC < 4.6 warning

On Tue, Jan 19, 2021 at 2:04 PM David Laight [off-list ref] wrote:

From: Adrian Ratiu

quoted

Sent: 19 January 2021 13:17
To: linux-arm-kernel@lists.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.

...

quoted

-#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.

Yes, patch 2 in the series removes it from .c source, and passes
-ftree-vectorize during Kbuild.

        David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

-- 
Thanks,
~Nick Desaulniers

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