| Message ID | 20221014201354.3190007-1-ndesaulniers@google.com |
|---|---|
| Headers | show |
| Series | pass -march= only to compiler | expand |
On Fri, Oct 14, 2022 at 1:14 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > When both -march= and -Wa,-march= are specified for assembler or > assembler-with-cpp sources, GCC and Clang will prefer the -Wa,-march= > value but Clang will warn that -march= is unused. > > warning: argument unused during compilation: '-march=armv6k' > [-Wunused-command-line-argument] > > This is the top group of warnings we observe when using clang to > assemble the kernel via `ARCH=arm make LLVM=1`. > > Arnd sent a v2 of my previous patch > https://lore.kernel.org/linux-arm-kernel/20210928154143.2106903-14-arnd@kernel.org/ > I added yet a few more instances I found since then. Nathan pointed out > a new one too that I've fixed since v3. > > Fixing this will allow us to enable > -Werror=unused-command-line-argument for clang builds. > > v3 had an issue wrt. __thumb2__ > https://lore.kernel.org/llvm/CAKwvOdmkd2PxvMUZA=A-72eATGDZkqDj--Bv1W+Xt_K_LWdROA@mail.gmail.com/ > I've incorporated idea from Nathan and Ard on that. I probably should have made a note: the base of this series is a little funny. It's based on today's linux-next (20221014) but with 0a7606a9832ab375a38425a659bda13712ca89ae reverted. It sounds like 0a7606a9832ab375a38425a659bda13712ca89ae might be dropped from -next imminently https://lore.kernel.org/linux-next/CAK7LNARg8OpqLR_71PJV3ZoLuDV8+mz9mphg=CzEeEEMY0G3rw@mail.gmail.com/.
On Fri, Oct 14, 2022 at 01:13:51PM -0700, Nick Desaulniers wrote: > arch-y and tune-y used lazy evaluation since they used to contain > cc-option checks. They don't any longer, so just eagerly evaluate these > command line flags. > > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> > --- > No change from v3. > > arch/arm/Makefile | 60 +++++++++++++++++++++-------------------------- > 1 file changed, 27 insertions(+), 33 deletions(-) > > diff --git a/arch/arm/Makefile b/arch/arm/Makefile > index c846119c448f..8dd943b50b7d 100644 > --- a/arch/arm/Makefile > +++ b/arch/arm/Makefile > @@ -63,44 +63,38 @@ KBUILD_CFLAGS += $(call cc-option,-fno-ipa-sra) > # Note that GCC does not numerically define an architecture version > # macro, but instead defines a whole series of macros which makes > # testing for a specific architecture or later rather impossible. > -arch-$(CONFIG_CPU_32v7M) =-D__LINUX_ARM_ARCH__=7 -march=armv7-m > -arch-$(CONFIG_CPU_32v7) =-D__LINUX_ARM_ARCH__=7 -march=armv7-a > -arch-$(CONFIG_CPU_32v6) =-D__LINUX_ARM_ARCH__=6 -march=armv6 > -# Only override the compiler option if ARMv6. The ARMv6K extensions are > +arch-$(CONFIG_CPU_32v7M) :=-D__LINUX_ARM_ARCH__=7 -march=armv7-m > +arch-$(CONFIG_CPU_32v7) :=-D__LINUX_ARM_ARCH__=7 -march=armv7-a > +arch-$(CONFIG_CPU_32v6) :=-D__LINUX_ARM_ARCH__=6 -march=armv6 > +# Only override the compiler opt:ion if ARMv6. The ARMv6K extensions are > # always available in ARMv7 > ifeq ($(CONFIG_CPU_32v6),y) > -arch-$(CONFIG_CPU_32v6K) =-D__LINUX_ARM_ARCH__=6 -march=armv6k > +arch-$(CONFIG_CPU_32v6K) :=-D__LINUX_ARM_ARCH__=6 -march=armv6k > endif > -arch-$(CONFIG_CPU_32v5) =-D__LINUX_ARM_ARCH__=5 -march=armv5te > -arch-$(CONFIG_CPU_32v4T) =-D__LINUX_ARM_ARCH__=4 -march=armv4t > -arch-$(CONFIG_CPU_32v4) =-D__LINUX_ARM_ARCH__=4 -march=armv4 > -arch-$(CONFIG_CPU_32v3) =-D__LINUX_ARM_ARCH__=3 -march=armv3m > - > -# Evaluate arch cc-option calls now > -arch-y := $(arch-y) > +arch-$(CONFIG_CPU_32v5) :=-D__LINUX_ARM_ARCH__=5 -march=armv5te > +arch-$(CONFIG_CPU_32v4T) :=-D__LINUX_ARM_ARCH__=4 -march=armv4t > +arch-$(CONFIG_CPU_32v4) :=-D__LINUX_ARM_ARCH__=4 -march=armv4 > +arch-$(CONFIG_CPU_32v3) :=-D__LINUX_ARM_ARCH__=3 -march=armv3m > > # This selects how we optimise for the processor. > -tune-$(CONFIG_CPU_ARM7TDMI) =-mtune=arm7tdmi > -tune-$(CONFIG_CPU_ARM720T) =-mtune=arm7tdmi > -tune-$(CONFIG_CPU_ARM740T) =-mtune=arm7tdmi > -tune-$(CONFIG_CPU_ARM9TDMI) =-mtune=arm9tdmi > -tune-$(CONFIG_CPU_ARM940T) =-mtune=arm9tdmi > -tune-$(CONFIG_CPU_ARM946E) =-mtune=arm9e > -tune-$(CONFIG_CPU_ARM920T) =-mtune=arm9tdmi > -tune-$(CONFIG_CPU_ARM922T) =-mtune=arm9tdmi > -tune-$(CONFIG_CPU_ARM925T) =-mtune=arm9tdmi > -tune-$(CONFIG_CPU_ARM926T) =-mtune=arm9tdmi > -tune-$(CONFIG_CPU_FA526) =-mtune=arm9tdmi > -tune-$(CONFIG_CPU_SA110) =-mtune=strongarm110 > -tune-$(CONFIG_CPU_SA1100) =-mtune=strongarm1100 > -tune-$(CONFIG_CPU_XSCALE) =-mtune=xscale > -tune-$(CONFIG_CPU_XSC3) =-mtune=xscale > -tune-$(CONFIG_CPU_FEROCEON) =-mtune=xscale > -tune-$(CONFIG_CPU_V6) =-mtune=arm1136j-s > -tune-$(CONFIG_CPU_V6K) =-mtune=arm1136j-s > - > -# Evaluate tune cc-option calls now > -tune-y := $(tune-y) > +tune-$(CONFIG_CPU_ARM7TDMI) :=-mtune=arm7tdmi > +tune-$(CONFIG_CPU_ARM720T) :=-mtune=arm7tdmi > +tune-$(CONFIG_CPU_ARM740T) :=-mtune=arm7tdmi > +tune-$(CONFIG_CPU_ARM9TDMI) :=-mtune=arm9tdmi > +tune-$(CONFIG_CPU_ARM940T) :=-mtune=arm9tdmi > +tune-$(CONFIG_CPU_ARM946E) :=-mtune=arm9e > +tune-$(CONFIG_CPU_ARM920T) :=-mtune=arm9tdmi > +tune-$(CONFIG_CPU_ARM922T) :=-mtune=arm9tdmi > +tune-$(CONFIG_CPU_ARM925T) :=-mtune=arm9tdmi > +tune-$(CONFIG_CPU_ARM926T) :=-mtune=arm9tdmi > +tune-$(CONFIG_CPU_FA526) :=-mtune=arm9tdmi > +tune-$(CONFIG_CPU_SA110) :=-mtune=strongarm110 > +tune-$(CONFIG_CPU_SA1100) :=-mtune=strongarm1100 > +tune-$(CONFIG_CPU_XSCALE) :=-mtune=xscale > +tune-$(CONFIG_CPU_XSC3) :=-mtune=xscale > +tune-$(CONFIG_CPU_FEROCEON) :=-mtune=xscale > +tune-$(CONFIG_CPU_V6) :=-mtune=arm1136j-s > +tune-$(CONFIG_CPU_V6K) :=-mtune=arm1136j-s > > ifeq ($(CONFIG_AEABI),y) > CFLAGS_ABI :=-mabi=aapcs-linux -mfpu=vfp > -- > 2.38.0.413.g74048e4d9e-goog > >
On Fri, Oct 14, 2022 at 01:13:53PM -0700, Nick Desaulniers wrote: > Avoids an error from the assembler for CONFIG_THUMB2 kernels: > > clang-15: error: hardware TLS register is not supported for the thumbv4t > sub-architecture > > This flag only makes sense to pass to the compiler, not the assembler. > > Perhaps CFLAGS_ABI can be renamed to CPPFLAGS_ABI to reflect that they > will be passed to both the compiler and assembler for sources that > require pre-processing. > > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> > --- > arch/arm/Makefile | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm/Makefile b/arch/arm/Makefile > index 8dd943b50b7d..ee888070b2ff 100644 > --- a/arch/arm/Makefile > +++ b/arch/arm/Makefile > @@ -111,7 +111,7 @@ CFLAGS_ABI += -meabi gnu > endif > > ifeq ($(CONFIG_CURRENT_POINTER_IN_TPIDRURO),y) > -CFLAGS_ABI += -mtp=cp15 > +KBUILD_CFLAGS += -mtp=cp15 > endif > > # Accept old syntax despite ".syntax unified" > -- > 2.38.0.413.g74048e4d9e-goog >
On Fri, Oct 14, 2022 at 01:13:54PM -0700, Nick Desaulniers wrote: > When both -march= and -Wa,-march= are specified for assembler or > assembler-with-cpp sources, GCC and Clang will prefer the -Wa,-march= > value but Clang will warn that -march= is unused. > > warning: argument unused during compilation: '-march=armv6k' > [-Wunused-command-line-argument] > > This is the top group of warnings we observe when using clang to > assemble the kernel via `ARCH=arm make LLVM=1`. > > Split the arch-y make variable into two, so that -march= flags only get > passed to the compiler, not the assembler. -D flags are added to > KBUILD_CPPFLAGS which is used for both C and assembler-with-cpp sources. > > Clang is trying to warn that it doesn't support different values for > -march= and -Wa,-march= (like GCC does, but the kernel doesn't need this) > though the value of the preprocessor define __thumb2__ is based on > -march=. Make sure to re-set __thumb2__ via -D flag for assembler > sources now that we're no longer passing -march= to the assembler. Set > it to a different value than the preprocessor would for -march= in case > -march= gets accidentally re-added to KBUILD_AFLAGS in the future. > Thanks to Ard and Nathan for this suggestion. > > Link: https://github.com/ClangBuiltLinux/linux/issues/1315 > Link: https://github.com/ClangBuiltLinux/linux/issues/1587 > Link: https://github.com/llvm/llvm-project/issues/55656 > Suggested-by: Ard Biesheuvel <ardb@kernel.org> > Suggested-by: Nathan Chancellor <nathan@kernel.org> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> This passed through my build matrix on top of commit dca45efbe3c8 ("Merge tag 'sound-fix-6.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound") and I saw no additional warnings/errors: Reviewed-by: Nathan Chancellor <nathan@kernel.org> Tested-by: Nathan Chancellor <nathan@kernel.org> > --- > Changes v3 -> v4: > * Add -D__thumb2__=2 to KBUILD_AFLAGS as per in-person discussion with > Ard and Nathan, and their SB tags. > * Reword commit message. > > arch/arm/Makefile | 36 +++++++++++++++++++++++++----------- > 1 file changed, 25 insertions(+), 11 deletions(-) > > diff --git a/arch/arm/Makefile b/arch/arm/Makefile > index ee888070b2ff..b58998749ead 100644 > --- a/arch/arm/Makefile > +++ b/arch/arm/Makefile > @@ -60,21 +60,34 @@ endif > KBUILD_CFLAGS += $(call cc-option,-fno-ipa-sra) > > # This selects which instruction set is used. > +arch-$(CONFIG_CPU_32v7M) :=-march=armv7-m > +arch-$(CONFIG_CPU_32v7) :=-march=armv7-a > +arch-$(CONFIG_CPU_32v6) :=-march=armv6 > +# Only override the compiler option if ARMv6. The ARMv6K extensions are > +# always available in ARMv7 > +ifeq ($(CONFIG_CPU_32v6),y) > +arch-$(CONFIG_CPU_32v6K) :=-march=armv6k > +endif > +arch-$(CONFIG_CPU_32v5) :=-march=armv5te > +arch-$(CONFIG_CPU_32v4T) :=-march=armv4t > +arch-$(CONFIG_CPU_32v4) :=-march=armv4 > +arch-$(CONFIG_CPU_32v3) :=-march=armv3m > + > # Note that GCC does not numerically define an architecture version > # macro, but instead defines a whole series of macros which makes > # testing for a specific architecture or later rather impossible. > -arch-$(CONFIG_CPU_32v7M) :=-D__LINUX_ARM_ARCH__=7 -march=armv7-m > -arch-$(CONFIG_CPU_32v7) :=-D__LINUX_ARM_ARCH__=7 -march=armv7-a > -arch-$(CONFIG_CPU_32v6) :=-D__LINUX_ARM_ARCH__=6 -march=armv6 > -# Only override the compiler opt:ion if ARMv6. The ARMv6K extensions are > +cpp-$(CONFIG_CPU_32v7M) :=-D__LINUX_ARM_ARCH__=7 > +cpp-$(CONFIG_CPU_32v7) :=-D__LINUX_ARM_ARCH__=7 > +cpp-$(CONFIG_CPU_32v6) :=-D__LINUX_ARM_ARCH__=6 > +# Only override the compiler option if ARMv6. The ARMv6K extensions are > # always available in ARMv7 > ifeq ($(CONFIG_CPU_32v6),y) > -arch-$(CONFIG_CPU_32v6K) :=-D__LINUX_ARM_ARCH__=6 -march=armv6k > +cpp-$(CONFIG_CPU_32v6K) :=-D__LINUX_ARM_ARCH__=6 > endif > -arch-$(CONFIG_CPU_32v5) :=-D__LINUX_ARM_ARCH__=5 -march=armv5te > -arch-$(CONFIG_CPU_32v4T) :=-D__LINUX_ARM_ARCH__=4 -march=armv4t > -arch-$(CONFIG_CPU_32v4) :=-D__LINUX_ARM_ARCH__=4 -march=armv4 > -arch-$(CONFIG_CPU_32v3) :=-D__LINUX_ARM_ARCH__=3 -march=armv3m > +cpp-$(CONFIG_CPU_32v5) :=-D__LINUX_ARM_ARCH__=5 > +cpp-$(CONFIG_CPU_32v4T) :=-D__LINUX_ARM_ARCH__=4 > +cpp-$(CONFIG_CPU_32v4) :=-D__LINUX_ARM_ARCH__=4 > +cpp-$(CONFIG_CPU_32v3) :=-D__LINUX_ARM_ARCH__=3 > > # This selects how we optimise for the processor. > tune-$(CONFIG_CPU_ARM7TDMI) :=-mtune=arm7tdmi > @@ -119,15 +132,16 @@ AFLAGS_NOWARN :=$(call as-option,-Wa$(comma)-mno-warn-deprecated,-Wa$(comma)-W) > > ifeq ($(CONFIG_THUMB2_KERNEL),y) > CFLAGS_ISA :=-mthumb -Wa,-mimplicit-it=always $(AFLAGS_NOWARN) > -AFLAGS_ISA :=$(CFLAGS_ISA) -Wa$(comma)-mthumb > +AFLAGS_ISA :=$(CFLAGS_ISA) -Wa$(comma)-mthumb -D__thumb2__=2 > else > CFLAGS_ISA :=$(call cc-option,-marm,) $(AFLAGS_NOWARN) > AFLAGS_ISA :=$(CFLAGS_ISA) > endif > > # Need -Uarm for gcc < 3.x > +KBUILD_CPPFLAGS +=$(cpp-y) > KBUILD_CFLAGS +=$(CFLAGS_ABI) $(CFLAGS_ISA) $(arch-y) $(tune-y) $(call cc-option,-mshort-load-bytes,$(call cc-option,-malignment-traps,)) -msoft-float -Uarm > -KBUILD_AFLAGS +=$(CFLAGS_ABI) $(AFLAGS_ISA) $(arch-y) $(tune-y) -include asm/unified.h -msoft-float > +KBUILD_AFLAGS +=$(CFLAGS_ABI) $(AFLAGS_ISA) -Wa,$(arch-y) $(tune-y) -include asm/unified.h -msoft-float > > CHECKFLAGS += -D__arm__ > > -- > 2.38.0.413.g74048e4d9e-goog >