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Re: [Qemu-devel] [PATCH v2 10/20] fpu/softfloat: define decompose struct
From: |
Peter Maydell |
Subject: |
Re: [Qemu-devel] [PATCH v2 10/20] fpu/softfloat: define decompose structures |
Date: |
Thu, 18 Jan 2018 14:31:25 +0000 |
On 18 January 2018 at 14:26, Philippe Mathieu-Daudé <address@hidden> wrote:
>
>
> Le 18 janv. 2018 10:09 AM, "Alex Bennée" <address@hidden> a écrit :
>
>
> Philippe Mathieu-Daudé <address@hidden> writes:
>>> +typedef struct {
>>> + uint64_t frac : 64;
>>
>> I think this does not work on LLP64/IL32P64 model.
>>
>> Should we add a check in ./configure and refuse to build on IL32P64
>> model? This would be safer IMHO.
>>
>>> + int exp : 32;
>>> + float_class cls : 8;
>>> + int : 23;
>>> + bool sign : 1;
>>
>> checking on "ISO/IEC 14882:1998" 9.6 Bit-fields:
>>
>> Alignment of bit-fields is implementation-defined. Bit-fields are packed
>> into some addressable allocation unit. [Note: bit-fields straddle
>> allocation units on some machines and not on others. Bit-fields are
>> assigned right-to-left on some machines, left-to-right on others. ]
>>
>> I'd still write it:
>>
>> int :23, sign :1;
>>
>>> +} decomposed_parts;
>
> I think rather than stuff it into bit fields we can just leave it up to
> the compiler?
>
>
> Yep, my only worry here is the IL32P64 model, if we care.
I don't think we care much about IL32P64, but the code should
still work there, right? It doesn't actually make any assumptions
about bitfield layout.
I think I agree that we shouldn't use bitfields here if we don't
need to, though.
thanks
-- PMM
- [Qemu-devel] [PATCH v2 07/20] fpu/softfloat: propagate signalling NaNs in MINMAX, (continued)
- [Qemu-devel] [PATCH v2 10/20] fpu/softfloat: define decompose structures, Alex Bennée, 2018/01/09
- Re: [Qemu-devel] [PATCH v2 10/20] fpu/softfloat: define decompose structures, Richard Henderson, 2018/01/09
- Re: [Qemu-devel] [PATCH v2 10/20] fpu/softfloat: define decompose structures, Peter Maydell, 2018/01/12
- Re: [Qemu-devel] [PATCH v2 10/20] fpu/softfloat: define decompose structures, Philippe Mathieu-Daudé, 2018/01/12
- Re: [Qemu-devel] [PATCH v2 10/20] fpu/softfloat: define decompose structures, Alex Bennée, 2018/01/18
- Re: [Qemu-devel] [PATCH v2 10/20] fpu/softfloat: define decompose structures, Philippe Mathieu-Daudé, 2018/01/18
- Re: [Qemu-devel] [PATCH v2 10/20] fpu/softfloat: define decompose structures,
Peter Maydell <=
- Re: [Qemu-devel] [PATCH v2 10/20] fpu/softfloat: define decompose structures, Philippe Mathieu-Daudé, 2018/01/18
- Re: [Qemu-devel] [PATCH v2 10/20] fpu/softfloat: define decompose structures, Peter Maydell, 2018/01/18
- Re: [Qemu-devel] [PATCH v2 10/20] fpu/softfloat: define decompose structures, Alex Bennée, 2018/01/23
[Qemu-devel] [PATCH v2 11/20] fpu/softfloat: re-factor add/sub, Alex Bennée, 2018/01/09
[Qemu-devel] [PATCH v2 14/20] fpu/softfloat: re-factor muladd, Alex Bennée, 2018/01/09