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Date: Thu, 20 Jan 2011 13:06:40 +0100
From: Christophe Lyon <christophe.lyon@st.com>
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Subject: Re: [Qemu-devel] [PATCH] Support saturation with shift=0.
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

On 19.01.2011 17:51, Peter Maydell wrote:
> On 19 January 2011 16:10, Christophe Lyon <christophe.lyon@st.com> wrote:
>>
>> This patch fixes corner-case saturations, when the target range is
>> zero. It merely removes the guard against (sh == 0), and makes:
>> __ssat(0x87654321, 1) return 0xffffffff and set the saturation flag
> 
> did you mean __ssat(0x87654321, 0) here? (they give the same
> result, of course, but it's the sh==0 case the patch is changing...)

Well... the ARM ARM says that the position for saturation is in the range 1 to 32, so I think the assembler encodes 1 less than what the user actually wrote. Hence at user level we use '1', but '0' is encoded and then parsed by qemu. Am I wrong?

Obviously, I can rephrase the commit message :-)

> 
>> __usat(0x87654321, 0) return 0 and set the saturation flag
>>
>> Signed-off-by: Christophe Lyon <christophe.lyon@st.com>
> 
> Checked against the ARM ARM and tested by
> random-instruction-sequence generation.
> 

Thanks.