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Date: Sun, 02 Jun 2013 21:52:42 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 10/21] memory: make section size a 128-bit
	integer
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-devel@nongnu.org, Richard Henderson <rth@twiddle.net>

Il 02/06/2013 16:50, Peter Maydell ha scritto:
> On 2 June 2013 15:36, Paolo Bonzini <pbonzini@redhat.com> wrote:
>> This should work:
>>
>>     int64_t h;
>>     if (!n) {
>>         return a;
>>     }
>>     h = a.hi >> n;
> 
> This is undefined for n >= 64.

Yes, it has to be a.hi >> (n & 63).

> I would suggest looking at fpu/softfloat-macros.h:shift128Right()
> except that that has at least one clearly dubious thing in it
> (a check for "count < 64" in an else case that can't be reached
> if count < 64)...

It's a bit different in that I want an arithmetic right shift.

Paolo