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This has been tried (not on vaporhardware Mill, I'm more thinking about e.g. Intel Itanium) and it failed. The reason is extremely simple: a speculative OOO pr
by temac 5y ago
This has been tried (not on vaporhardware Mill, I'm more thinking about e.g. Intel Itanium) and it failed.
The reason is extremely simple: a speculative OOO processor optimizes dynamically. If you switch that with static compile time optimizations, you are bound to only be as fast as before in some quite limited parameter ranges (like: number of entries in a hash table, size of an image, etc.)
- homerowilson 5y agoAlso don't forget the really interesting Transmeta processors, also ultimately a failure. VLIW is very difficult in practice.
- p_l 5y agoTransmeta were VLIW, yes, but weren't EPIC - which is the main difference involved. VLIW just means there's a long instruction word, usually targeting multiple units, but it doesn't necessarily mean there's no dynamic reshuffle in the CPU architecture or anything like that. EPIC stood for Explicitly Parallel Instruction Computing, and took the "let's push it all to compiler" to the extreme. Itanium was never supposed to have any form of branch prediction or OOB, because it was supposed to be handled by the compiler. This led to someone quipping that Itanium was a very fast DSP, but ridiculously expensive.