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Re: [Qemu-devel] [PATCH v4 22/22] fpu/softfloat: re-factor sqrt
From: |
Richard Henderson |
Subject: |
Re: [Qemu-devel] [PATCH v4 22/22] fpu/softfloat: re-factor sqrt |
Date: |
Tue, 13 Feb 2018 08:23:01 -0800 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 |
On 02/13/2018 07:50 AM, Peter Maydell wrote:
>> + /* We need two overflow bits at the top. Adding room for that is
>> + a right shift. If the exponent is odd, we can discard the low
>> + bit by multiplying the fraction by 2; that's a left shift.
>> + Combine those and we shift right if the exponent is even. */
>> + a_frac = a.frac;
>> + if (!(a.exp & 1)) {
>> + a_frac >>= 1;
>> + }
>> + a.exp >>= 1;
> Comment says "shift right if the exponent is even", but code
> says "shift right by 1 if exponent is odd, by 2 if exponent is even".
>
The last line is dividing the exponent by 2, not shifting the fraction.
r~
- [Qemu-devel] [PATCH v4 08/22] include/fpu/softfloat: add some float16 constants, (continued)
- [Qemu-devel] [PATCH v4 08/22] include/fpu/softfloat: add some float16 constants, Alex Bennée, 2018/02/06
- [Qemu-devel] [PATCH v4 10/22] fpu/softfloat: move the extract functions to the top of the file, Alex Bennée, 2018/02/06
- [Qemu-devel] [PATCH v4 09/22] fpu/softfloat: improve comments on ARM NaN propagation, Alex Bennée, 2018/02/06
- [Qemu-devel] [PATCH v4 07/22] include/fpu/softfloat: implement float16_set_sign helper, Alex Bennée, 2018/02/06
- [Qemu-devel] [PATCH v4 14/22] fpu/softfloat: re-factor div, Alex Bennée, 2018/02/06
- [Qemu-devel] [PATCH v4 16/22] fpu/softfloat: re-factor round_to_int, Alex Bennée, 2018/02/06
- [Qemu-devel] [PATCH v4 22/22] fpu/softfloat: re-factor sqrt, Alex Bennée, 2018/02/06
- Re: [Qemu-devel] [PATCH v4 22/22] fpu/softfloat: re-factor sqrt, Richard Henderson, 2018/02/13
[Qemu-devel] [PATCH v4 20/22] fpu/softfloat: re-factor minmax, Alex Bennée, 2018/02/06
[Qemu-devel] [PATCH v4 19/22] fpu/softfloat: re-factor scalbn, Alex Bennée, 2018/02/06
[Qemu-devel] [PATCH v4 21/22] fpu/softfloat: re-factor compare, Alex Bennée, 2018/02/06
[Qemu-devel] [PATCH v4 11/22] fpu/softfloat: define decompose structures, Alex Bennée, 2018/02/06
[Qemu-devel] [PATCH v4 18/22] fpu/softfloat: re-factor int/uint to float, Alex Bennée, 2018/02/06
[Qemu-devel] [PATCH v4 13/22] fpu/softfloat: re-factor mul, Alex Bennée, 2018/02/06