From: David Laight <David.Laight@ACULAB.COM>
To: 'Jisheng Zhang' <jszhang@kernel.org>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>
Cc: "linux-riscv@lists.infradead.org"
<linux-riscv@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] riscv: select ARCH_HAS_FAST_MULTIPLIER
Date: Wed, 22 Nov 2023 11:16:23 +0000 [thread overview]
Message-ID: <47995b4daafb43348fc839ffb486f56b@AcuMS.aculab.com> (raw)
In-Reply-To: <20231121144340.3492-1-jszhang@kernel.org>
...
> However, the
> situation exists on x86 too, for example, P4 doesn't have fast
> integer multiplies ...
P4 doesn't have fast anything :-)
More interestingly does anything modern not have fast multiplies?
(that you'd consider running Linux on).
The silicon required isn't that big.
IIRC an 'n' bit multiplier requires n^2 full adders and has
the latency of 2n adders.
David
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prev parent reply other threads:[~2023-11-22 11:16 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-21 14:43 [PATCH] riscv: select ARCH_HAS_FAST_MULTIPLIER Jisheng Zhang
2023-11-21 22:20 ` Samuel Holland
2023-11-22 11:16 ` David Laight [this message]
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