plans for 64bit support (Joshua Root)

[Vincent Lefevre]

On 2007-12-20 22:22:51 +0100, Markus Weissmann wrote:
> If I remember correctly, all powerpc instructions have a length of
> 32 bit.

That's not different from the ARM.

> Given that you need some bits for the opcode, a mere 16 bit remain to  
> stuff a constant value to it (for the load high/add intermediate  
> instructions).

You missed the point: there is no need to encode the constant in the
instructions since it can be somewhere else in the memory (e.g. in a
"constant pool").

> Keep in mind that these 64 bit constants only cost you for pointers.

If all pointers are sufficiently close to each other, another solution
is to keep a base pointer in some register, and compute the other ones
with an addition to a 16-bit or a 32-bit constant (2 or 3 instructions).

-- 
Vincent Lefèvre <vincent at vinc17.org> - Web: <http://www.vinc17.org/>
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