[Mono-list] 32-bit vs 64-bit Performance Discrepency
kumpera at gmail.com
Wed Oct 26 20:56:00 EDT 2011
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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