[PATCH 7/9] LoongArch: Tweak CFLAGS for Clang compatibility

From: WANG Xuerui
Date: Fri Jun 23 2023 - 09:44:37 EST


From: WANG Xuerui <git@xxxxxxxxxx>

Now the arch code is mostly ready for LLVM/Clang consumption, it is time
to re-organize the CFLAGS a little to actually enable the LLVM build.

A build with !RELOCATABLE && !MODULE is confirmed working within a QEMU
environment; support for the two features are currently blocked by
LLVM/Clang, and will come later.

Signed-off-by: WANG Xuerui <git@xxxxxxxxxx>
---
arch/loongarch/Makefile | 14 +++++++++++---
arch/loongarch/vdso/Makefile | 6 +++++-
2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
index a27e264bdaa5..efe9b50bd829 100644
--- a/arch/loongarch/Makefile
+++ b/arch/loongarch/Makefile
@@ -46,12 +46,18 @@ ld-emul = $(64bit-emul)
cflags-y += -mabi=lp64s
endif

-cflags-y += -G0 -pipe -msoft-float
-LDFLAGS_vmlinux += -G0 -static -n -nostdlib
+ifndef CONFIG_CC_IS_CLANG
+cflags-y += -G0
+LDFLAGS_vmlinux += -G0
+endif
+cflags-y += -pipe
+LDFLAGS_vmlinux += -static -n -nostdlib

# When the assembler supports explicit relocation hint, we must use it.
# GCC may have -mexplicit-relocs off by default if it was built with an old
-# assembler, so we force it via an option.
+# assembler, so we force it via an option. For LLVM/Clang the desired behavior
+# is the default, and the flag is not supported, so don't pass it if Clang is
+# being used.
#
# When the assembler does not supports explicit relocation hint, we can't use
# it. Disable it if the compiler supports it.
@@ -61,8 +67,10 @@ LDFLAGS_vmlinux += -G0 -static -n -nostdlib
# combination of a "new" assembler and "old" compiler is not supported. Either
# upgrade the compiler or downgrade the assembler.
ifdef CONFIG_AS_HAS_EXPLICIT_RELOCS
+ifndef CONFIG_CC_IS_CLANG
cflags-y += -mexplicit-relocs
KBUILD_CFLAGS_KERNEL += -mdirect-extern-access
+endif
else
cflags-y += $(call cc-option,-mno-explicit-relocs)
KBUILD_AFLAGS_KERNEL += -Wa,-mla-global-with-pcrel
diff --git a/arch/loongarch/vdso/Makefile b/arch/loongarch/vdso/Makefile
index 4c859a0e4754..19f6c75a1106 100644
--- a/arch/loongarch/vdso/Makefile
+++ b/arch/loongarch/vdso/Makefile
@@ -25,13 +25,17 @@ endif
cflags-vdso := $(ccflags-vdso) \
-isystem $(shell $(CC) -print-file-name=include) \
$(filter -W%,$(filter-out -Wa$(comma)%,$(KBUILD_CFLAGS))) \
- -O2 -g -fno-strict-aliasing -fno-common -fno-builtin -G0 \
+ -O2 -g -fno-strict-aliasing -fno-common -fno-builtin \
-fno-stack-protector -fno-jump-tables -DDISABLE_BRANCH_PROFILING \
$(call cc-option, -fno-asynchronous-unwind-tables) \
$(call cc-option, -fno-stack-protector)
aflags-vdso := $(ccflags-vdso) \
-D__ASSEMBLY__ -Wa,-gdwarf-2

+ifndef CONFIG_CC_IS_CLANG
+cflags-vdso += -G0
+endif
+
ifneq ($(c-gettimeofday-y),)
CFLAGS_vgettimeofday.o += -include $(c-gettimeofday-y)
endif
--
2.40.0