On 15 January 2018 at 16:07, Arnd Bergmann <arnd@xxxxxxxx> 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: https://www.mail-archive.com/linux-crypto@xxxxxxxxxxxxxxx/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@xxxxxxxx> Acked-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > --- > v2: fix a typo in the Makefile > --- > crypto/Makefile | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/crypto/Makefile b/crypto/Makefile > index daa69360e054..cdbc03b35510 100644 > --- a/crypto/Makefile > +++ b/crypto/Makefile > @@ -99,7 +99,7 @@ obj-$(CONFIG_CRYPTO_TWOFISH_COMMON) += twofish_common.o > obj-$(CONFIG_CRYPTO_SERPENT) += serpent_generic.o > CFLAGS_serpent_generic.o := $(call cc-option,-fsched-pressure) # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79149 > obj-$(CONFIG_CRYPTO_AES) += aes_generic.o > -CFLAGS_aes_generic.o := $(call cc-ifversion, -ge, 0701, -Os) # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83356 > +CFLAGS_aes_generic.o := $(call cc-option,-fno-code-hoisting) # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83356 > obj-$(CONFIG_CRYPTO_AES_TI) += aes_ti.o > obj-$(CONFIG_CRYPTO_CAMELLIA) += camellia_generic.o > obj-$(CONFIG_CRYPTO_CAST_COMMON) += cast_common.o > -- > 2.9.0 >
