[PATCH v2] riscv: don't specify -mno-save-restore when building with clang < 11

[Tobias Klauser]

Clang before version 11 doesn't support -msave-restore and
-mno-save-restore [1].

[1] https://github.com/ClangBuiltLinux/linux/issues/804

This avoids the following message when building with clang 10 and older:

  '-save-restore' is not a recognized feature for this target (ignoring feature)

Signed-off-by: Tobias Klauser <tklauser at distanz.ch>
---
v2: use cc-option and check for clang version

 arch/riscv/Makefile | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index fb6e37db836d..30e34946af86 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -44,7 +44,14 @@ riscv-march-$(CONFIG_RISCV_ISA_C)	:= $(riscv-march-y)c
 KBUILD_CFLAGS += -march=$(subst fd,,$(riscv-march-y))
 KBUILD_AFLAGS += -march=$(riscv-march-y)
 
-KBUILD_CFLAGS += -mno-save-restore
+KBUILD_CFLAGS += $(call cc-option,-mno-save-restore)
+# Clang versions less than 11 do not support save-restore. See
+# https://github.com/ClangBuiltLinux/linux/issues/804
+ifeq ($(CONFIG_CC_IS_CLANG), y)
+  ifeq ($(shell test $(CONFIG_CLANG_VERSION) -lt 110000; echo $$?),0)
+    KBUILD_CFLAGS := $(filter-out -mno-save-restore,$(KBUILD_CFLAGS))
+  endif
+endif
 KBUILD_CFLAGS += -DCONFIG_PAGE_OFFSET=$(CONFIG_PAGE_OFFSET)
 
 ifeq ($(CONFIG_CMODEL_MEDLOW),y)
-- 
2.27.0