Re: Modern compilers for ye olde architectures

On 05/10/2021 14:22, Luke A. Guest wrote:
> 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.
>
> I know GCC has backends for some older architectures, but these do weird
> gymnastics such as implementing a virtual cpu in rtl and then lowering
> further.
>


Certainly modern techniques /can/ be applied to a Z80 compiler. And the
Z80 is a lot more powerful than many 8-bit CISC microcontrollers.


As far as I know, the only 8-bit target for gcc (in the mainline at
least) is the AVR. This is a RISC processor, with 32 8-bit registers,
and a much more orthogonal architecture. gcc does do some "weird
gymnastics", however - it allocates registers in pairs so that it can
pretend to be 16-bit, and then code gets simplified in peephole passes.


gcc also supports some 16-bit CISC devices.


For the Z80, however, there are a number of compiler options. There are
some commercial toolchains, such as HiSoft (IIRC), and there is the
"Rabbit" microcontroller which is a derivative of the Z80. It is
supported by a compiler for a somewhat extended version of C. Such
compilers are probably quite old, however, and might not be easily
available.


Your best bet is probably SDCC. This is a multi-target open source
compiler that is in regular development, and aimed specifically for
small CISC microcontroller cores. The Z80 is one of its targets.

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