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Re: [Lightning] SPARC Fixes

From: Ludovic Courtès
Subject: Re: [Lightning] SPARC Fixes
Date: Tue, 31 Oct 2006 18:01:27 +0100
User-agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux)


Paolo Bonzini <address@hidden> writes:

>> For 1.2, we have to keep them anyway.  Even beyond, is may be a nice
>> thing to have because it probably looks familiar to many people.
> If you look at code produced by compilers, they rarely if ever
> push/pop.  What they do, is they allocate an area to "spill" in the
> variables that don't fit into the registers.  Even if the original
> code is stack-based bytecode, it's pretty easy to track the stack
> height at every point of the bytecodes, assuming it's balanced on
> control flow junctions.  Which is true for practically everything but
> Forth.  Then, using indexed loads instead of continuously updating the
> hardware stack pointer will be faster on most machines.

Agreed.  So, technically, you'd release a bug-fix 1.2 that leaves
`pushr' and `popr' and then a 1.3 or something with the new API?

>> I haven't looked at instruction encoding so I have no idea whether
>> patching `save' would be an easy task (I guess it shouldn't be too
>> hard).
> It's actually pretty easy.  Easier than fixing the SETHI/OR part as
> done to patch jit_patch_movi.

Ok.  I'm looking forward to testing it!  ;-)


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