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Supporting 64-bit ARM systems

Supporting 64-bit ARM systems

Posted Jul 27, 2012 21:48 UTC (Fri) by jzbiciak (✭ supporter ✭, #5246)
In reply to: Supporting 64-bit ARM systems by marcH
Parent article: Supporting 64-bit ARM systems

That is true, although to a lesser extent. I'd say it gives you a point on the continuum.

JITs can use dynamic profile information (both block and path frequency) and specific details of the run environment to tailor the code, but they can't respond at the granularity of, say, re-ordering instructions due to cache misses, for example. If you have a purely statically scheduled instruction set like EPIC, no amount of JIT will help reorder loads if the miss patterns are data dependent and dynamically changing. (Speculate/Check loads can help, but only so much.)

Speaking of the ultimate JIT platform Transmeta: Even Transmeta has some hardware patents for hardware memory access speculation mechanisms. I recall one which was a speculative store buffer: The software would queue up stores for a predicted path, and then another instruction would either commit the queue or discard it. Or something like that... Ah, I think this might be the one: http://www.freepatentsonline.com/7225299.html


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