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@intel.com Link: https://www.mail-archive.com/linux-crypto@vger.kernel.org/msg30418.html Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83356 Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83651 Fixes: 148b974deea9 ("crypto: aes-generic - build with -Os on gcc-7+") Signed-off-by: Arnd Bergmann arnd@arndb.de
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'
Thanks, Horia