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Re: M68k backend has landed in LLVM - NetBSD support



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


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