Messages in this thread | | | From | Nick Desaulniers <> | Date | Mon, 24 Jan 2022 14:49:29 -0800 | Subject | Re: [PATCH 2/2] MIPS: Loongson64: Wrap -mno-branch-likely with cc-option |
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On Mon, Jan 24, 2022 at 2:37 PM Nathan Chancellor <nathan@kernel.org> wrote: > > On Mon, Jan 24, 2022 at 12:40:58PM -0800, Nick Desaulniers wrote: > > On Thu, Jan 20, 2022 at 1:40 PM Nathan Chancellor <nathan@kernel.org> wrote: > > > > > > This flag is not supported by clang, which results in a warning: > > > > > > clang-14: warning: argument unused during compilation: '-mno-branch-likely' [-Wunused-command-line-argument] > > > > > > This breaks cc-option, which adds -Werror to make this warning fatal and > > > catch flags that are not supported. Wrap the flag in cc-option so that > > > it does not cause cc-option to fail, which can cause randconfigs to be > > > really noisy. > > > > > > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > > > > We should convert more of these tests to Kconfig checks that run once > > per configuration, rather than multiple times for a build. IIRC Linus > > mentioned this somewhere...yeah, the -Wimplicit-fallthrough patches. > > See > > dee2b702bcf06 ("kconfig: Add support for -Wimplicit-fallthrough") > > > > I wonder if we can check ARCH or SUBARCH in Kconfig to limit invoking > > the tool under test for certain arch specific command line flags? > > > > I'll take this patch over such a larger change, but I think towards > > the goal of speeding up already configured builds, we eventually want > > to be migrating cc-option and ld-option checks to Kconfig. > > > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > > Something like this appears to work, if that is more preferrable? > > diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig > index 058446f01487..a27a3ade810e 100644 > --- a/arch/mips/Kconfig > +++ b/arch/mips/Kconfig > @@ -3232,3 +3232,9 @@ endmenu > source "arch/mips/kvm/Kconfig" > > source "arch/mips/vdso/Kconfig" > + > +config CC_MNO_BRANCH_LIKELY > + string > + default "-mno-branch-likely" > + depends on MACH_LOONGSON64 || MACH_LOONGSON2EF > + depends on $(cc-option,-mno-branch-likely) > diff --git a/arch/mips/loongson2ef/Platform b/arch/mips/loongson2ef/Platform > index 50e659aca543..66ed09581417 100644 > --- a/arch/mips/loongson2ef/Platform > +++ b/arch/mips/loongson2ef/Platform > @@ -41,6 +41,6 @@ cflags-y += $(call cc-option,-mno-loongson-mmi) > # Loongson Machines' Support > # > > -cflags-$(CONFIG_MACH_LOONGSON2EF) += -I$(srctree)/arch/mips/include/asm/mach-loongson2ef -mno-branch-likely > +cflags-$(CONFIG_MACH_LOONGSON2EF) += -I$(srctree)/arch/mips/include/asm/mach-loongson2ef $(CONFIG_CC_MNO_BRANCH_LIKELY)
Does that allow someone to modify the value for CC_MNO_BRANCH_LIKELY in menuconfig?
If so, I'd rather the Makefiles have:
cflags-$(CONFIG_CC_MNO_BRANCH_LIKELY) += -mno-branch-likely
and CONFIG_CC_MNO_BRANCH_LIKELY be a bool rather than an editable string. I think that makes the Makefile more readable; you don't have to see what CONFIG_CC_MNO_BRANCH_LIKELY expands to in a different file.
See also CC_HAS_ASM_GOTO and CC_HAS_ASM_GOTO_OUTPUT in init/Kconfig.
> load-$(CONFIG_LEMOTE_FULOONG2E) += 0xffffffff80100000 > load-$(CONFIG_LEMOTE_MACH2F) += 0xffffffff80200000 > diff --git a/arch/mips/loongson64/Platform b/arch/mips/loongson64/Platform > index 3e660d6d3c2b..88fbdfe9ffcc 100644 > --- a/arch/mips/loongson64/Platform > +++ b/arch/mips/loongson64/Platform > @@ -33,5 +33,5 @@ cflags-y += $(call cc-option,-mno-loongson-mmi) > # Loongson Machines' Support > # > > -cflags-$(CONFIG_MACH_LOONGSON64) += -I$(srctree)/arch/mips/include/asm/mach-loongson64 -mno-branch-likely > +cflags-$(CONFIG_MACH_LOONGSON64) += -I$(srctree)/arch/mips/include/asm/mach-loongson64 $(CONFIG_CC_MNO_BRANCH_LIKELY) > load-$(CONFIG_CPU_LOONGSON64) += 0xffffffff80200000 > > > > --- > > > arch/mips/loongson64/Platform | 3 ++- > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > diff --git a/arch/mips/loongson64/Platform b/arch/mips/loongson64/Platform > > > index 981d3abc150e..acf9edc9b15d 100644 > > > --- a/arch/mips/loongson64/Platform > > > +++ b/arch/mips/loongson64/Platform > > > @@ -26,5 +26,6 @@ cflags-y += $(call cc-option,-mno-loongson-mmi) > > > # Loongson Machines' Support > > > # > > > > > > -cflags-$(CONFIG_MACH_LOONGSON64) += -I$(srctree)/arch/mips/include/asm/mach-loongson64 -mno-branch-likely > > > +cflags-$(CONFIG_MACH_LOONGSON64) += -I$(srctree)/arch/mips/include/asm/mach-loongson64 > > > +cflags-$(CONFIG_MACH_LOONGSON64) += $(call cc-option,-mno-branch-likely) > > > load-$(CONFIG_CPU_LOONGSON64) += 0xffffffff80200000 > > > -- > > > 2.34.1 > > > > > > > > > > > > -- > > Thanks, > > ~Nick Desaulniers >
-- Thanks, ~Nick Desaulniers
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