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From: anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups: comp.arch
Subject: Re: Computer architects leaving Intel...
Date: Wed, 04 Sep 2024 08:05:51 GMT
Organization: Institut fuer Computersprachen, Technische Universitaet Wien
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BGB <cr88192@gmail.com> writes:
>Otherwise, annoying:
>Despite configuring GCC to use RV64G, it builds its C library as RV64GC 
>and is like "well, close enough".

This may be an artifact of bootstrapping.  At some point I built a new
version of gcc for our Alphas.  We had machines without the BWX
extensions and machines with the BWX extension.

Of course I built gcc on the fastest machine we had, one with BWX.
And then I found out that the resulting compiler binary would not run
on the machines without BWX.

Ok, so build it again, taking care to configure it to not use BWX in
bootstrapping itself.  However, somehow libgcc got inherited from the
previous build, so the resulting compiler would run on machines
without BWX, but the binaries it produced would not.  My guess is that
something similar happened for libgcc in your case.

I did another round of rebuilding, making sure that libgcc was rebuilt
from scratch without BWX.  I don't remember all that was involved;
maybe I just did this build on a machine that does not have BWX.

[Risc-V compressed instructions]
>Which is annoying because seemingly nearly every instruction has its own 
>encoding scheme for the immediate fields.

It's designed for easy hardware decoding, so maybe you just need to
discover the ideas behind that and put them into your decoder.

- anton
-- 
'Anyone trying for "industrial quality" ISA should avoid undefined behavior.'
  Mitch Alsup, <c17fcd89-f024-40e7-a594-88a85ac10d20o@googlegroups.com>