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>

1 files changed, 21 insertions, 0 deletions

diff --git a/arch/mips/loongson64/Platform b/arch/mips/loongson64/Platform
index 2e48e83d5524..85d808924c94 100644
--- a/arch/mips/loongson64/Platform
+++ b/arch/mips/loongson64/Platform
@@ -22,6 +22,27 @@ ifdef CONFIG_CPU_LOONGSON2F_WORKAROUNDS
   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
 #