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Re: [Qemu-devel] [PATCH 3/3] tcg: Add MO_ALIGN, MO_UNALN


From: Richard Henderson
Subject: Re: [Qemu-devel] [PATCH 3/3] tcg: Add MO_ALIGN, MO_UNALN
Date: Wed, 13 May 2015 14:19:07 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0

On 05/13/2015 02:15 PM, Peter Maydell wrote:
> On 13 May 2015 at 22:08, Richard Henderson <address@hidden> wrote:
>>> Are unaligned accesses always slow-path, by the way?
> 
> Would it be in theory possible to fast-path MO_UNALN
> unaligned accesses if the host CPU supported unaligned
> accesses for whatever load/store insn we use in the TLB
> hit case?

We would also need to test for page boundary crossing.  That would take at
least 3 more insns, for a host that natively supports unaligned accesses.
Whether that's worth it or not would need testing...


r~




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