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From: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <85b5aa04-ec85-a2b6-3b79-2bb991824004@linaro.org>
Date: Mon, 29 Jan 2018 07:50:43 -0800
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Subject: Re: [Qemu-devel] [PATCH v3 19/22] fpu/softfloat: re-factor scalbn
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To: =?UTF-8?Q?Alex_Benn=c3=a9e?= <alex.bennee@linaro.org>
Cc: peter.maydell@linaro.org, laurent@vivier.eu, bharata@linux.vnet.ibm.com, andrew@andrewdutcher.com, qemu-devel@nongnu.org, Aurelien Jarno <aurelien@aurel32.net>

On 01/29/2018 03:59 AM, Alex Bennée wrote:
> 
> Richard Henderson <richard.henderson@linaro.org> writes:
> 
>> On 01/24/2018 05:13 AM, Alex Bennée wrote:
>>> +/* Multiply A by 2 raised to the power N.  */
>>> +static FloatParts scalbn_decomposed(FloatParts a, int n,
>>> +                                          float_status *s)
>>> +{
>>> +    if (a.cls == float_class_normal) {
>>> +        a.exp += n;
>>> +    }
>>> +    return a;
>>> +}
>>
>> ...
>>
>>> -    if ( aExp == 0x7FF ) {
>>> -        if ( aSig ) {
>>> -            return propagateFloat64NaN(a, a, status);
>>
>> This is where we used to raise inexact.
>> In the new function we need to handle this as in round_to_int.
> 
> Why is the handling in round_canonical not good enough for this?

This is scalbn -- you don't call round_canonical.


r~