MIPS: Loongson-3: Improve -march option and move it to Platform
If GCC >= 4.9 and Binutils >=2.25, we use -march=loongson3a, otherwise
we use -march=mips64r2, this can slightly improve performance. Besides,
arch/mips/loongson64/Platform is a better location rather than arch/
mips/Makefile.
Signed-off-by: Huacai Chen <chenhc@lemote.com>
Cc: Aurelien Jarno <aurelien@aurel32.net>
Cc: Steven J. Hill <Steven.Hill@imgtec.com>
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/12161/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/loongson64/Platform b/arch/mips/loongson64/Platform
index 2e48e83..85d8089 100644
--- a/arch/mips/loongson64/Platform
+++ b/arch/mips/loongson64/Platform
@@ -22,6 +22,27 @@
endif
endif
+cflags-$(CONFIG_CPU_LOONGSON3) += -Wa,--trap
+#
+# binutils from v2.25 on and gcc starting from v4.9.0 treat -march=loongson3a
+# as MIPS64 R2; older versions as just R1. This leaves the possibility open
+# that GCC might generate R2 code for -march=loongson3a which then is rejected
+# by GAS. The cc-option can't probe for this behaviour so -march=loongson3a
+# can't easily be used safely within the kbuild framework.
+#
+ifeq ($(call cc-ifversion, -ge, 0409, y), y)
+ ifeq ($(call ld-ifversion, -ge, 22500000, y), y)
+ cflags-$(CONFIG_CPU_LOONGSON3) += \
+ $(call cc-option,-march=loongson3a -U_MIPS_ISA -D_MIPS_ISA=_MIPS_ISA_MIPS64)
+ else
+ cflags-$(CONFIG_CPU_LOONGSON3) += \
+ $(call cc-option,-march=mips64r2,-mips64r2 -U_MIPS_ISA -D_MIPS_ISA=_MIPS_ISA_MIPS64)
+ endif
+else
+ cflags-$(CONFIG_CPU_LOONGSON3) += \
+ $(call cc-option,-march=mips64r2,-mips64r2 -U_MIPS_ISA -D_MIPS_ISA=_MIPS_ISA_MIPS64)
+endif
+
#
# Loongson Machines' Support
#