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Re: C# and Parrot

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Dan Sugalski
October 18, 2002 13:46
Re: C# and Parrot
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At 1:38 PM +0100 10/18/02, Simon Cozens wrote:
> (Rhys Weatherley) writes:
>>      int x = ...;
>>      int y = (short)x;
>>  The value of x is truncated to 16 bits, and then sign-extended
>>  to int.  I'm looking for something like the "conv.i2" instruction
>>  in IL, or "i2s" in JVM.
>One concievable way to do that is basically have the hypothetical
>CSInt and CSShort PMC classes know and care how many bits they're
>supposed to be, and handle overflow internally.

Yep, that's definitely a good way to do that. In many cases I think 
it'll be the right way

>If need an op to do it, you can always provide a custom one. I think.

Alternately, we can have ops that act on I regs as 8, 16, 32 or, 
maybe, 64 bit quantities. Dealing with I regs as 64 bit quantities on 
a 32 bit system is somewhat problematic, as there are interesting 
architectural issues. (Do you double up registers? If so, what about 
systems that don't need it? Or do you keep a second set of 
half-registers squirrelled away somewhere? Which is an interesting 
problem in cache coherency, not to mention a hack)

--------------------------------------"it's like this"-------------------
Dan Sugalski                          even samurai                         have teddy bears and even
                                       teddy bears get drunk

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