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Re: [Qemu-devel] [PATCH 10/21] memory: make section size a 128-bit integ
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From: |
Paolo Bonzini |
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Subject: |
Re: [Qemu-devel] [PATCH 10/21] memory: make section size a 128-bit integer |
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Date: |
Sun, 02 Jun 2013 21:52:42 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6 |
Il 02/06/2013 16:50, Peter Maydell ha scritto:
> On 2 June 2013 15:36, Paolo Bonzini <address@hidden> 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