> 2023年4月6日 22:09，Nathan Chancellor <nathan@xxxxxxxxxx> 写道：
>
> On Thu, Apr 06, 2023 at 09:59:45PM +0100, Jiaxun Yang wrote:
>>
>>
>>> 2023年4月6日 21:09，Nathan Chancellor <nathan@xxxxxxxxxx> 写道：
>>>
>>> When building allnoconfig with clang after commit de34007751aa ("MIPS:
>>> generic: Enable all CPUs supported by virt board in Kconfig"), the
>>> following error occurs:
>>>
>>> error: unknown target CPU 'r4600'
>>> note: valid target CPU values are: mips1, mips2, mips3, mips4, mips5, mips32, mips32r2, mips32r3, mips32r5, mips32r6, mips64, mips64r2, mips64r3, mips64r5, mips64r6, octeon, octeon+, p5600
>>>
>>> Working around that, there are similar errors for 'loongson2e' and
>>> 'loongson2f'.
>>>
>>> These CPUs are not supported in clang/LLVM, so do not select support for
>>> them in MIPS_GENERIC_KERNEL when building with clang.
>>>
>>> Fixes: de34007751aa ("MIPS: generic: Enable all CPUs supported by virt board in Kconfig")
>>> Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
>>
>> Thanks for the patch.
>>
>> Actually there is no need for any special support for those CPUs.
>> We should be able to build those kernels with -march=mips3.
>>
>> I think something like:
>>
>> --- a/arch/mips/Makefile
>> +++ b/arch/mips/Makefile
>> @@ -150,7 +150,7 @@ cflags-y += $(call cc-option,-Wa$(comma)-mno-fix-loongson3-llsc,)
>> #
>> cflags-$(CONFIG_CPU_R3000) += -march=r3000
>> cflags-$(CONFIG_CPU_R4300) += -march=r4300 -Wa,--trap
>> -cflags-$(CONFIG_CPU_R4X00) += -march=r4600 -Wa,--trap
>> +cflags-$(CONFIG_CPU_R4X00) += $(call cc-option,-march=r4600,-march=mips3) -Wa,--trap
>> cflags-$(CONFIG_CPU_TX49XX) += -march=r4600 -Wa,--trap
>> cflags-$(CONFIG_CPU_MIPS32_R1) += -march=mips32 -Wa,--trap
>> cflags-$(CONFIG_CPU_MIPS32_R2) += -march=mips32r2 -Wa,--trap
>> @@ -181,8 +181,8 @@ endif
>> cflags-$(CONFIG_CAVIUM_CN63XXP1) += -Wa,-mfix-cn63xxp1
>> cflags-$(CONFIG_CPU_BMIPS) += -march=mips32 -Wa,-mips32 -Wa,--trap
>>
>> -cflags-$(CONFIG_CPU_LOONGSON2E) += -march=loongson2e -Wa,--trap
>> -cflags-$(CONFIG_CPU_LOONGSON2F) += -march=loongson2f -Wa,--trap
>> +cflags-$(CONFIG_CPU_LOONGSON2E) += $(call cc-option,-march=loongson2e,-march=mips3) -Wa,--trap
>> +cflags-$(CONFIG_CPU_LOONGSON2F) += $(call cc-option,-march=loongson2f,-march=mips3) -Wa,--trap
>> # Some -march= flags enable MMI instructions, and GCC complains about that
>> # support being enabled alongside -msoft-float. Thus explicitly disable MMI.
>> cflags-$(CONFIG_CPU_LOONGSON2EF) += $(call cc-option,-mno-loongson-mmi)
>>
>> Will make them build.
>
> Thank you for taking a look and the suggestion! I applied it and tried
> to build allnoconfig but I get
>
> error: ABI 'o32' is not supported on CPU 'mips3'
>
> immediately, which could certainly be a bug in clang...
There is a clang patch:
https://reviews.llvm.org/D146269
I’ve seen this warning with CONFIG_MIPS32_O32 enabled, but I think that’s not the case for allnoconfig...
Thanks
Jiaxun
>
> Cheers,
> Nathan
