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

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Message-Id: <20230623134351.1898379-8-kernel@xen0n.name>
Date:   Fri, 23 Jun 2023 21:43:49 +0800
From:   WANG Xuerui <kernel@...0n.name>
To:     Huacai Chen <chenhuacai@...nel.org>
Cc:     WANG Rui <wangrui@...ngson.cn>, Xi Ruoyao <xry111@...111.site>,
        loongarch@...ts.linux.dev, linux-kbuild@...r.kernel.org,
        llvm@...ts.linux.dev, linux-kernel@...r.kernel.org,
        WANG Xuerui <git@...0n.name>
Subject: [PATCH 7/9] LoongArch: Tweak CFLAGS for Clang compatibility

From: WANG Xuerui <git@...0n.name>

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@...0n.name>
---
 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