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by kyboren
890 days ago
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Not prediction, predication: https://en.wikipedia.org/wiki/Predication_(computer_architec... By avoiding conditional branches and essentially masking out some instructions, you can avoid stalls and mis-predictions and keep the pipeline full. Actually I think @IainIreland mis-remembers what the seasoned architect told him about Itanium. While Itanium did support predicated instructions, the problematic static scheduling was actually because Itanium was a VLIW machine: https://en.wikipedia.org/wiki/VLIW . TL;DR: dynamic scheduling on superscalar out-of-order processors with vector units works great and the transistor overhead got increasingly cheap, but static scheduling stayed really hard. |
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