Re: [PATCH v2] [v2] crypto: aes-generic - fix aes-generic regression on powerpc

From: Horia Geanta
Date: Mon Sep 17 2018 - 05:19:16 EST

On 1/20/2018 2:44 AM, Herbert Xu wrote:
> On Mon, Jan 15, 2018 at 05:07:22PM +0100, Arnd Bergmann wrote:
>> My last bugfix added -Os on the command line, which unfortunately caused
>> a build regression on powerpc in some configurations.
>> I've done some more analysis of the original problem and found slightly
>> different workaround that avoids this regression and also results in
>> better performance on gcc-7.0: -fcode-hoisting is an optimization step
>> that got added in gcc-7 and that for all gcc-7 versions causes worse
>> performance.
>> This disables -fcode-hoisting on all compilers that understand the option.
>> For gcc-7.1 and 7.2 I found the same performance as my previous patch
>> (using -Os), in gcc-7.0 it was even better. On gcc-8 I could see no
>> change in performance from this patch. In theory, code hoisting should
>> not be able make things better for the AES cipher, so leaving it
>> disabled for gcc-8 only serves to simplify the Makefile change.
>> Reported-by: kbuild test robot <fengguang.wu@xxxxxxxxx>
>> Link:
>> Link:
>> Link:
>> Fixes: 148b974deea9 ("crypto: aes-generic - build with -Os on gcc-7+")
>> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> Patch applied. Thanks.
This fix ("commit 6e36719fbe90213fbba9f50093fa2d4d69b0e93c upstream") is needed
also in 4.14.y stable tree, since it contains commit
7cae67e31292 ("crypto: aes-generic - build with -Os on gcc-7+")

Compilation fails without it:
crypto/aes_generic.o: In function `crypto_aes_set_key':
crypto/aes_generic.c:1300: undefined reference to `_restgpr_31_x'