[hajile]

> I don't believe there is any practical "magical" sequence of instructions that could be easily recognised to implement Javascript conversion from float to int. If that is in fact as important as ARM apparently think it is (I have my doubts) then an equivalent of FJCVTZS should be added to RISC-V as an extension.

They claim 2%, but only in JS code. I'd guess static analysis of outputted v8/JSC/SM JIT code from the top 100 websites would give a very accurate estimation of the savings. One of the most fundamental performance boosters is using 31-bit ints instead of doubles, but every single time time the user needs to access a number for output, it must be converted to a double to keep the JS spec contract.

All that said, I think only Apple's last 4-6 chips and ARM's most recent generation of chips actually implement the instruction and people have been fine without it. I'd guess we'll not be seeing this in RISC-V until much lower-hanging fruits have been picked.