Johnny Billquist wrote:
Manuel Bouyer wrote:On Sun, Oct 19, 2008 at 02:07:36PM +0200, Johnny Billquist wrote:Hey! Don't shoot the messenger.But no, I wouldn't consider them all "native". The size of the registers is what I'd define as native.The size of the registers depend on the instruction on x86_64 ...The concept of using just a part of a register is hardly new, by the way.As far as I know, all CPUs do the same when playing with a data type that is shorter than the size of the register. Only the parts that fit into the data type of the instruction are actually modified in the register by the instruction. That don't change the number of bits that actually are stored in the register, though.
And to nitpickingly comment myself, some architectures, with some instructions, will either sign-extend or zero-extend registers when playing with smaller data types.
There. I'll be quiet now. :-)
Johnny