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Date: Fri, 10 Jul 2015 17:47:37 +0800
From: Lei Zhang <>
Subject: Re: extend SIMD intrinsics

> On Jul 7, 2015, at 9:16 PM, Solar Designer <> wrote:
> On Mon, Jul 06, 2015 at 11:15:41PM -0400, Alain Espinosa wrote:
>> In Visual C the difference of a simple assignment and a vload is that for the assignment the compiler generate an unaligned SIMD load instruction, and for vload it generates an aligned SIMD load with the usual restriction: if this memory access isn't aligned the required byte amount an exception is raised. In general the performance difference is negligible,  if any.
> When I corrected my code (bitslice DES code in JtR) to
> make the alignment apparent to gcc, it stopped generating the unaligned
> load instructions, generating the aligned ones instead.

Could you exemplify how you did it with some code?


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