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Date: Thu, 16 May 2024 12:29:08 +0200
From: Andrew Jones <ajones@ventanamicro.com>
To: Conor Dooley <conor.dooley@microchip.com>
CC: Conor Dooley <conor@kernel.org>, linux-riscv@lists.infradead.org,
 xiao.w.wang@intel.com, pulehui@huawei.com,
 Charlie Jenkins <charlie@rivosinc.com>,
 Paul Walmsley <paul.walmsley@sifive.com>,
 Palmer Dabbelt <palmer@dabbelt.com>, linux-kernel@vger.kernel.org
Subject: =?US-ASCII?Q?Re=3A_=5BPATCH_v1=5D_RISC-V=3A_separate_Zbb_optimisatio?=
 =?US-ASCII?Q?ns_requiring_and_not_requiring_toolchain_support?=
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On May 16, 2024 10:59:44 AM GMT+02:00, Conor Dooley <conor=2Edooley@microch=
ip=2Ecom> wrote:
>On Thu, May 16, 2024 at 09:59:44AM +0200, Andrew Jones wrote:
>> On Wed, May 15, 2024 at 04:27:40PM GMT, Conor Dooley wrote:
>>=20
>> So the new hidden config is a shorthand for
>>=20
>> #if defined(CONFIG_RISCV_ISA_ZBB) && \
>>     defined(CONFIG_TOOLCHAIN_HAS_ZBB) && \
>>     defined(CONFIG_RISCV_ALTERNATIVE)
>>=20
>> which is reasonable to add, since that's a mouthful, but I'm not sure t=
he
>> name, RISCV_ISA_ZBB_ALT, does a good job conveying all that=2E
>>=20
>> If we instead just dropped the 'depends on TOOLCHAIN_HAS_ZBB' from
>> config RISCV_ISA_ZBB (keeping the 'depends on RISCV_ALTERNATIVE',
>> since nobody is really complaining about that), then we could change
>> this to
>>=20
>> #if defined(CONFIG_RISCV_ISA_ZBB) && defined(CONFIG_TOOLCHAIN_HAS_ZBB)
>
>Yeah, I think this is a cleaner solution=2E
>
>> >  	asm goto(ALTERNATIVE("j %l[legacy]", "nop", 0,
>> >  				      RISCV_ISA_EXT_ZBB, 1)
>> >  			  : : : : legacy);
>> > diff --git a/arch/riscv/include/asm/bitops=2Eh b/arch/riscv/include/a=
sm/bitops=2Eh
>> > index 880606b0469a=2E=2E3ed810a6123d 100644
>> > --- a/arch/riscv/include/asm/bitops=2Eh
>> > +++ b/arch/riscv/include/asm/bitops=2Eh
>> > @@ -15,7 +15,7 @@
>> >  #include <asm/barrier=2Eh>
>> >  #include <asm/bitsperlong=2Eh>
>> > =20
>> > -#if !defined(CONFIG_RISCV_ISA_ZBB) || defined(NO_ALTERNATIVE)
>> > +#if !defined(CONFIG_RISCV_ISA_ZBB_ALT) || defined(NO_ALTERNATIVE)
>>=20
>> nit: It's sufficient to check !defined(CONFIG_RISCV_ISA_ZBB), so no nee=
d
>> for this change or its #endif comment change below=2E
>
>Are you sure? I did test leaving this as-was and it broke the build for
>llvm-14=2E

Oops, sorry=2E I didn't look at the full context=2E You were right=2E

Thanks,
drew

>
>Cheers,
>Conor=2E