On Mon, Oct 19, 2009 at 10:40 AM, Steve Reinhardt <[email protected]> wrote: > I think this only works if IPRs do not have side effects. I'm pretty sure > there are IPR writes that need to be serializing because they change things > like ASID. It might be possible to treat IPR writes as serializing but not > IPR reads, though there may be IPR reads that have side effects that don't > tolerate re-ordering (e.g., if it's a clear-on-read reg where the cleared > state is reflected in some other reg). > > The EV6 PAL code has explicit scoreboard bits to manage these dependences. > > One easy test would be just to (temporarily) get rid of the IsIprAccess flag > on rduniq in arch/alpha/isa/decoder.isa and see if that works and if it > improves the IPC. Unfortunately, I think this would require a bunch of hacking in the decoder because currently callpal is just a single opcode and to do this, we'd have to create an opcode for each palcall (which wouldn't be all that bad, but would add several dozen instructions.)
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