Hi Jason, On Tue, Oct 31, 2017 at 12:43:19PM +0100, Jason A. Donenfeld wrote: > Versions of gcc prior to gcc 5 emitted a __multi3 function call when > dealing with TI types, resulting in failures when trying to link to > libgcc, and more generally, horrible performance. However, since gcc 5, > the compiler supports actually emitting fast instructions, which means > we can at long last enable this option and receive the speedups. > > The gcc commit that added proper Aarch64 support is: > https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=d1ae7bb994f49316f6f63e6173f2931e837a351d > > This commit appears to be part of the gcc 5 release. > > Signed-off-by: Jason A. Donenfeld <ja...@zx2c4.com> > --- > arch/arm64/Makefile | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile > index 939b310913cf..1f8a0fec6998 100644 > --- a/arch/arm64/Makefile > +++ b/arch/arm64/Makefile > @@ -53,6 +53,8 @@ KBUILD_AFLAGS += $(lseinstr) $(brokengasinst) > KBUILD_CFLAGS += $(call cc-option,-mabi=lp64) > KBUILD_AFLAGS += $(call cc-option,-mabi=lp64) > > +KBUILD_CFLAGS += $(call cc-ifversion, -ge, 0500, > -DCONFIG_ARCH_SUPPORTS_INT128) > + > ifeq ($(CONFIG_CPU_BIG_ENDIAN), y) > KBUILD_CPPFLAGS += -mbig-endian > CHECKFLAGS += -D__AARCH64EB__
This breaks an allmodconfig build: lib/ubsan.o: In function `get_signed_val': ubsan.c:(.text.unlikely+0x13c): undefined reference to `__ashlti3' ubsan.c:(.text.unlikely+0x144): undefined reference to `__ashrti3' make: *** [vmlinux] Error 1 so I'm going to drop it for now. My toolchain is: gcc version 7.1.1 20170707 (Linaro GCC 7.1-2017.08) Will
