Re: [GD-General] Feedback wanted on POSH

[Brian H. <ho...@py...>]

> int - is fastest performing integer type for the platform. So,
> Opteron, G5/PPC970, and Itanium may likely nudge int from 32bits up
> to 64bits.

This isn't really a platform thing as much as it is a compiler thing.  
Many, if not most, C compilers on DEC Alpha made "int" 32-bits simply 
for compatibility reasons.

> float - fastest IEEE floating point arithmetic mode.
> So most everything was 32bits.. now we're migrating to 64bit, so
> this could change as well.

Very few CPUs implement 64-bit floating point as fast as 32-bit.  One 
thing that POSH doesn't try to do is abstract between IEEE and 
non-IEEE floating point formats.  That just gets too complicated.

> void* - most appropriate pointer type.
> So dos's void* was 16bit for tiny and small real mode, 32bit for
> medium and large mode, then protected mode/flat mode rolled around
> and 32bit (31bit) became norm, now we've been warned not to use the
> 32nd bit for house keeping because that'll get busted when
> migrating to 64bit.

This is one reason I'm specifically not supporting segmented 
architectures =3D)  And technically DOS had 32-bit sized pointers, but 
they were actually only 20-bit addresses, much like early Amiga had 
32-bit pointers but only 24-bit addresses (the good old days of 
shoving extra data in the high 8-bits...)

> As far as I know, the only truly standard types are:
> short - 16bit signed integer
> long - 32bit signed integer

nope

The only guarantee is:

sizeof(char)<=3Dsizeof(short)<=3Dsizeof(int)<=3Dsizeof(long)

For example, on the Cray T8, ALL types are 64-bits except for char I 
believe.

> Eventually we'll have to gracefully move C/C++ into the new world
> of SIMD capabilities.  I just hope there is also a plan to employ a
> much better set of type definitions to go with it.

Until the SIMD world can figure out how to refactor itself cleanly, I 
probably won't touch this, but it's something at the back of my mind.  
Right now "portable SIMD code" seems a bit like an oxymoron.

Brian