This may explain why iPhone XS is so anomalously fast at Speedometer 2.0. Low level benchmarks (and Apple themselves) suggested 15% improvement, what we got in the real world was almost 40% cc
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Replying to @steipete
More precisely: ARMv8.3 adds a new float-to-int instruction with errors and out-of-range values handled the way that JavaScript wants. The previous insns to get JavaScript's semantics were much slower. JavaScript's numbers are double by default so it needs this conversion a lot.










