Re: Is pmax alive?

[David Holland <dholland-mips%netbsd.org@localhost>]

On Tue, May 10, 2016 at 06:57:31PM +0100, Maciej W. Rozycki wrote:
 > On Tue, 10 May 2016, Felix Deichmann wrote:
 >  If people agree on removing the `.set noreorder' directive (note that it 
 > will affect all MIPS ports, not only pmax, though the change is supposed 
 > to be functionally neutral, which can perhaps be verified with `objdump 
 > -d'),

So the problem with that is that gas doesn't really fill in delay
slots; only the original assembler written by the MIPS folks has ever
really done much of that.

Also after twenty years of bitrot I would not trust gas to get the
delay slots for supervisor instructions right for mips-I. It might
work, but it might not too.

My recommendation would be to scrape up whatever docs we can find and
assemble a canonical table of nop and delay requirements, then write
an analyzer tool to run on .o files to detect violations. This is not
very hard (disassembling mips machine code is somewhat annoying but
straightforward) and has the advantage of being robust and reasonably
future-proof. And useful for anything that wants to run on mips.

The problem I've always had is getting authoritative information about
the requirements.

That and (especially on early r3xxx and r4xxx models) some of them
vary randomly from model to model.

-- 
David A. Holland
dholland%netbsd.org@localhost