Re: M68k backend has landed in LLVM - NetBSD support

[John Klos <john%ziaspace.com@localhost>]

> One thing I wonder is whether LLVM/clang can actually be built and run 
> on NetBSD/m68k: NetBSD's VM on m68k only uses a single root page for the 
> page tables, so with 4KB pages you have a hard VM ceiling of only a 
> couple hundred megabytes, and with 8KB pages you're still under a 
> gigabyte.

This is already a problem. On an Amiga with 128 megs of memory and 256 
megs of swap, gcc 10.3.0 runs in to "virtual memory exhausted: Cannot 
allocate memory" issues with cmake, for instance.

> Granted modern GCC will take a significant amount of time and memory to 
> build as well, but I don't think it's as heavy in that respect as LLVM. 
> Maybe it's time for someone versed in the intricacies of the m68k MMUs 
> to add support for more root pages…

Now's the time... I have another Amiga with 336 megabytes - it could have 
as much as 912 megs - and a Macintosh Quadra with 520 megabytes, and 
neither can use the full amount yet.

I'd love to find any books, documentation, whatever, about MMU setup on 
m68k. I'm learning what I can from NetBSD's Alpha code - it ain't easy!

John