Integer conversions too pedantic in 64-bit

[spir]

On 02/17/2011 10:13 AM, Don wrote:
> David Nadlinger wrote:
>> On 2/17/11 8:56 AM, Denis Koroskin wrote:
>>> I second that. word/uword are shorter than ssize_t/size_t and more in
>>> line with other type names.
>>>
>>> I like it.
>>
>> I agree that size_t/ptrdiff_t are misnomers and I'd love to kill them with
>> fire, but when I read about »word«, I intuitively associated it with »two
>> bytes« first – blame Intel or whoever else, but the potential for confusion
>> is definitely not negligible.
>>
>> David
>
> Me too. A word is two bytes. Any other definition seems to be pretty useless.
>
> The whole concept of "machine word" seems very archaic and incorrect to me
> anyway. It assumes that the data registers and address registers are the same
> size, which is very often not true.
> For example, on an 8-bit machine (eg, 6502 or Z80), the accumulator was only 8
> bits, yet size_t was definitely 16 bits.
> It's quite plausible that at some time in the future we'll get a machine with
> 128-bit registers and data bus, but retaining the 64 bit address bus. So we
> could get a size_t which is smaller than the machine word.
>
> In summary: size_t is not the machine word.

Right, there is no single native machine word size; but I guess what we're 
interesting in is, from those sizes, the one that ensures minimal processing 
time. I mean, the data size for which there are native computation instructions 
(logical, numeric), so that if we use it we get the least number of cycles for 
a given operation.
Also, this size (on common modern architectures, at least) allows directly 
accessing all of the memory address space; not a neglectable property ;-).
Or are there points I'm overlooking?

Denis
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