Re: Computer architects leaving Intel...

On 14/09/2024 21:26, Thomas Koenig wrote:

MitchAlsup1 <mitchalsup@aol.com> schrieb:
 

In many cases int is slower now than long -- which violates the notion
of int from K&R days.

 That's a designers's choice, I think.  It is possible to add 32-bit
instructions which should be as fast (or possibly faster) than
64-bit instructions, as AMD64 and ARM have shown.
 

For some kinds of instructions, that's true - for others, it's not so easy without either making rather complicated instructions or having assembly instructions with undefined behaviour (imagine the terror that would bring to some people!).
A classic example would be for "y = p[x++];" in a loop.  For a 64-bit type x, you would set up one register once with "p + x", and then have a load with post-increment instruction in the loop.  You can also do that with x as a 32-bit int, unless you are of the opinion that enough apples added to a pile should give a negative number of apples.  But with a wrapping type for x - such as unsigned int in C or modulo types in Ada, you have little choice but to hold "p" and "x" separately in registers, add them for every load, and do the increment and modulo operation.  I really can't see this all being handled by a single instruction.
Of course you could add a 32-bit zero extend or sign extend to many 32-bit ALU instructions and save some instructions - many architectures already support that kind of thing.

And having a smaller memory footprint is also beneficial, especially
for caches.
 (Plus, there are FORTRAN's storage association rules, but these should
be less used by now.  But for a 64-bit integer, they pretty much would
require a 64-bit REAL and a 128-bit DOUBLE PRECISION).