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Date: Thu, 5 Aug 2021 16:40:45 +0300 (MSK)
From: Alexander Monakov <amonakov@...ras.ru>
To: Stefan Kanthak <stefan.kanthak@...go.de>
cc: Szabolcs Nagy <nsz@...t70.net>, musl@...ts.openwall.com
Subject: Re: [Patch] src/math/i386/remquo.s: remove conditional branch,
shorter bit twiddling
On Wed, 4 Aug 2021, Stefan Kanthak wrote:
> The change just follows by removing 6 LOC/instructions.-)
Have you considered collecting the three bits in one go via a multiplication?
You can first isolate the necessary bits with 'and $0x4300, %eax', then do
'imul $0x910000, %eax, %eax' to put the required bits in EAX[31:29] in the
right order, then shift right by 29. Three instructions, 14 bytes.
Alexander
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