linux-kernel - Re: [PATCH] crc32-pclmul: remove useless relative addressing

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Message-ID: <20171007041847.GD29803@gondor.apana.org.au>
Date:   Sat, 7 Oct 2017 12:18:47 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Mikulas Patocka <mpatocka@...hat.com>
Cc:     Alexander Boyko <alexander_boyko@...atex.com>,
        "David S. Miller" <davem@...emloft.net>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] crc32-pclmul: remove useless relative addressing

On Wed, Sep 06, 2017 at 10:41:21PM -0400, Mikulas Patocka wrote:
> In 32-bit mode, the x86 architecture can hold full 32-bit pointers.
> Therefore, the code that copies the current address to the %ecx register
> and uses %ecx-relative addressing is useless, we could just use absolute
> addressing.
> 
> The processors have a stack of return addresses for branch prediction. If 
> we use a call instruction and pop the return address, it desynchronizes 
> the return stack and causes branch prediction misses.
> 
> This patch also moves the data to the .rodata section.
> 
> Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
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