[Mono-list] 32-bit vs 64-bit Performance Discrepency

[Rodrigo Kumpera]

On Wed, Oct 26, 2011 at 10:12 PM, Justin Holewinski <
justin.holewinski at gmail.com> wrote:

> On Wed, Oct 26, 2011 at 7:37 PM, Rodrigo Kumpera <kumpera at gmail.com>wrote:
>
>>
>>
>> On Wed, Oct 26, 2011 at 9:06 PM, Justin Holewinski <
>> justin.holewinski at gmail.com> wrote:
>>
>>> On Wed, Oct 26, 2011 at 6:15 PM, Rodrigo Kumpera <kumpera at gmail.com>wrote:
>>>
>>>> The CLR demands that all floating point calculations to be conducted
>>>> with double precision.
>>>
>>>
>>> Where in the spec does it state this?  Everything I've read allows for
>>> both 32-bit and 64-bit representations, with the only restriction being that
>>> arithmetic must be performed with enough precision for the expression type.
>>>
>>> And if 64-bit arithmetic is required, why is 32-bit used in the 32-bit
>>> Mono VM, and in the .NET VM?
>>>
>>>
>>
>> 32bits mono uses 64bits precision for both float and double types.
>>
>
>> AFAICT, .net uses 64bits precision on all cases.
>>
>
> I'm getting code like the following on .NET 4.0 x64:
>
> 00000099  mov         rcx,qword ptr [rsp+000000D8h]
> 000000a1  mov         rax,qword ptr [rsp+30h]
> 000000a6  movss       xmm0,dword ptr [rsp+28h]
> 000000ac  mulss       xmm0,dword ptr [rcx+rax*4+10h]
> 000000b2  movss       dword ptr [rsp+38h],xmm0
>
> Is there any way to force Mono to use 32-bit arithmetic for floats?
>

No, not really.

Please file a bug over this as we probably should change it.
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