[TUHS] Re: Porting Unix v6 to i386

Peter Jeremy peter.jeremy at alcatel.com.au
Fri Feb 15 13:08:29 AEST 2002

On 2002-Feb-14 14:30:50 -0800, "Aaron J. Grier" <agrier at poofygoof.com> wrote:
>support for PDP-11 was added to gcc a few months ago.  I don't think
>it's been well tested, but support exists in current versions of
>binutils and gcc.
>there's also support for the m68hc11/12 which are 16-bit.

This is only cross-compilation support.  gcc was never designed to be
hosted in a 16-bit environment.  An i386 gcc is:
   text    data     bss     dec     hex filename
1660236   22836   97104 1780176  1b29d0 /usr/libexec/cc1

Even taking into account the savings with 16-bit int's and pointers,
you won't get the data segment below 64k - and most of gcc's structures
are dynamically allocated.

>it seems like support for 80{,1,2}86 in gcc should be possible; it just
>hasn't been done yet.

Given that i386 is already supported, adding support for 16-bit x86
would be fairly easy.  The only major work would be handling the
16-bit addressing modes.

>another compiler that might be worth looking at is SDCC
>http://sdcc.sourceforge.net/ which is currently targeted towards 8-bit

Again, no x86 support and I don't believe the code generation is
that good.

>of course bootstrapping via the original K&R compiler would be the
>"classic" way to do it, though.  ;)

The PDP-11 is orthogonal and so PCC doesn't have to worry about
getting particular operands into particular registers.  I suspect
that supporting the i386's idiosyncracies would be non-trivial.


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