Re: Modern compilers for ye olde architectures

"Luke A. Guest" <laguest@archeia.com> writes:
>I have a Z80 project in mind and would like to build a compiler for a
>Z80. I was wondering if modern backend techniques can be applied
>successfully for these old CPU's, i.e. SSA.


SSA can certainly be used in a compiler for the Z80, but SSA is not a
back-end technique; it's a way to represent data flow in the
intermediate representation.


As for the back-end, it seems to me that the major problem with the
Z80 is that it does not have general-purpose registers; instead, many
instructions deal with specific registers. Many early architectures
were like that, and assembly programmers could puzzle out good
register assignments, but compilers were not particularly good at it.
So eventually computer architects introduced machines with
general-purpose registers like the PDP-11, the VAX, and the RISCs; and
compiler writers developed techniques like graph colouring to make
good use of these architectures.


Maybe with the increased memory and processing power available now,
one could do better, but given that special-purpose registers are
mostly a thing of the past, there has not been much research into
that, that I am aware of. Maybe the puzzle-solving approach to
register allocation can help, but I am not familiar enough with that
to say for sure.


- anton
--
M. Anton Ertl
anton@mips.complang.tuwien.ac.at
http://www.complang.tuwien.ac.at/anton/

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