[kaffe] More JIT3 Questions

Warwick Hunter whunter at agile.tv
Wed Mar 26 14:20:02 PST 2003


Sounds promising. I am happy to help test your
MIPS JIT patch(es) when you are ready.


  D. Kissell wrote:
>>I'm still fumbling and grepping around, but for the moment it
>>certainly looks to me as if whoever wrote the jit3-mips.def
>>code is using the higher-level register management code
>>inappropriately, with the consequence that there is a lot
>>of memory traffic that could be eliminated by the simple
>>expedient of reserving 2-3 registers as MIPS/JIT temporaries
>>and using those for memory/memory copies, rather than
>>sucking the register allocator dry, then performing useless
>>spills/reloads.  But, again, I'm still groping/grepping around.
> Update: I have successfully fixed the TestNative bug in two
> different ways, but I'm still not 100% satisfied.
> The first hack was to go into config/mips/jit3-mips.def
> and replace  instances of rreg_float and rreg_double
> in the pushd_float and push_double code with instances
> of rreg_ideal_float and rreg_ideal_double which specify
> a floating temp register (f16 in this case).  The second
> hack was simply to flag f12 and f14 as Reserved in 
> comfig/mips/jit.h.  It may be that the "correct" approach
> would be to do something of both - reserving the FP
> arguments (and indeed, the integer argument registers)
> would seem to be prudent, given that the register allocator
> will otherwise trash them between their being set up by
> a method prologue and their being passed to an invoked
> method, but allocating a new register (or pair of registers)
> each time we want to copy values up the stack, such that
> we spill data for no good purpose is probably a bad idea
> anyway.
> I'll send a patch out at some point, but there are still 4
> failing regression tests (even with both the FP and the
> integer argument registers "Reserved"), and I'd like to 
> nail as many of them as I can before I distribute anything.
>             Kevin K.
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Warwick Hunter                    Agile TV Corporation
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