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From: Conor Dooley <conor@kernel.org>
To: Charlie Jenkins <charlie@rivosinc.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>,
	linux-kernel@vger.kernel.org, Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	linux-riscv@lists.infradead.org
Subject: Re: [PATCH v2 2/5] riscv: Add checksum library
Date: Thu, 7 Sep 2023 10:52:35 +0100	[thread overview]
Message-ID: <20230907-9d5d2e7ef2a20edd75514470@fedora> (raw)
In-Reply-To: <20230905-optimize_checksum-v2-2-ccd658db743b@rivosinc.com>


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On Tue, Sep 05, 2023 at 09:46:51PM -0700, Charlie Jenkins wrote:

> +#ifdef CONFIG_RISCV_ISA_ZBB
> +	if (IS_ENABLED(CONFIG_RISCV_ALTERNATIVE)) {
> +		/*
> +		 * Zbb is likely available when the kernel is compiled with Zbb
> +		 * support, so nop when Zbb is available and jump when Zbb is
> +		 * not available.
> +		 */
> +		asm_volatile_goto(ALTERNATIVE("j %l[no_zbb]", "nop",  0,
> +					      RISCV_ISA_EXT_ZBB, 1)
> +		    :
> +		    :
> +		    :
> +		    : no_zbb);
> +	} else {
> +		if (!__riscv_isa_extension_available(NULL, RISCV_ISA_EXT_ZBB))
> +			goto no_zbb;
> +	}

Again, do these constructs have an appreciable benefit over doing
if (!riscv_has_extension_likely(<ZBB>)
	goto no_zbb;

?

That encaspulates the fallback to a non-alternative mechanism for you,
in case you had not noticed.

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  reply	other threads:[~2023-09-07  9:52 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-06  4:46 [PATCH v2 0/5] riscv: Add fine-tuned checksum functions Charlie Jenkins
2023-09-06  4:46 ` [PATCH v2 1/5] riscv: Checksum header Charlie Jenkins
2023-09-07  9:40   ` Conor Dooley
2023-09-07 17:44     ` Charlie Jenkins
2023-09-10 21:20       ` David Laight
2023-09-11 18:16         ` Charlie Jenkins
2023-09-06  4:46 ` [PATCH v2 2/5] riscv: Add checksum library Charlie Jenkins
2023-09-07  9:52   ` Conor Dooley [this message]
2023-09-07 17:47     ` Charlie Jenkins
2023-09-06  4:46 ` [PATCH v2 3/5] riscv: Vector checksum header Charlie Jenkins
2023-09-07  9:47   ` Conor Dooley
2023-09-07 17:43     ` Charlie Jenkins
2023-09-07  9:58   ` Conor Dooley
2023-09-07 17:41     ` Charlie Jenkins
2023-09-06  4:46 ` [PATCH v2 4/5] riscv: Vector checksum library Charlie Jenkins
2023-09-06  4:46 ` [PATCH v2 5/5] riscv: Test checksum functions Charlie Jenkins

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