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, bad 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. There are still a few instructions, such as __ashlti3 and __ashrti3, that require libgcc, which is fine. So, we also link to libgcc for these functions when needed, which is what several other architectures already have been doing for a long time. Signed-off-by: Jason A. Donenfeld <ja...@zx2c4.com> --- arch/arm64/Makefile | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 939b310913cf..70c7c0c1bccb 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__ @@ -108,7 +110,7 @@ core-$(CONFIG_NET) += arch/arm64/net/ core-$(CONFIG_KVM) += arch/arm64/kvm/ core-$(CONFIG_XEN) += arch/arm64/xen/ core-$(CONFIG_CRYPTO) += arch/arm64/crypto/ -libs-y := arch/arm64/lib/ $(libs-y) +libs-y := arch/arm64/lib/ $(shell $(CC) $(KBUILD_CFLAGS) -print-libgcc-file-name) $(libs-y) core-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a # Default target when executing plain make -- 2.14.2
