🚀 go-pugleaf

> How would you react to an instruction set that had no indexed addressing
> mode, but did have a mode where a register was ORed into the address?
> 
> I can vaguely recall having seen such a beast - is anyone familiar with it?

IBM 7090?  3-bit index register field, 3 index registers.  I believe the
registers selected were OR'd together, then ADDed to the offset.

> ....  Losing indexing for array accesses isn't too bad, since
> just about every expensive array operation can be written using
> pointers instead of indexes (post-increment doesn't require a
> carry to perform a memory address).

No semi-random access by subscripts?  Your machine is to be
programmed exclusively in C or assembler, never Fortran.

> So what can you do? Adding an index register in slows down the rest of your
> instruction set,

Even when you don't index?

> .... and, if memory is cheap, you might be willing to pad out a
> lot more of your structures, to get a speed increase.

or use a separate add instruction.