linux-kernel - Re: [PATCH v2 2/2] sparc64: Use lzcnt instruction for fls and _

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Message-Id: <20170927.151020.2182569060914905496.davem@davemloft.net>
Date:   Wed, 27 Sep 2017 15:10:20 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     anthony.yznaga@...cle.com
Cc:     sam@...nborg.org, vijay.ac.kumar@...cle.com,
        linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org,
        babu.moger@...cle.com, rob.gardner@...cle.com
Subject: Re: [PATCH v2 2/2] sparc64: Use lzcnt instruction for fls and __fls

From: Anthony Yznaga <anthony.yznaga@...cle.com>
Date: Wed, 27 Sep 2017 14:45:34 -0700

> Vijay,
> Older assemblers may not support this flag so you’ll need to
> hardcode the lzcnt instructions using .word directives.

Right, older binutils do not support the T4 instructions.

This is why we hardcode the opcodes for all of the crypto
instructions used under arch/sparc64/crypto/, for example.