Comment by sjrd

Interesting. When compiling Scala.js to ECMAScript 5, we still have an implementation of bitwise floating point conversions based on double operations and integer shifts. [1] We also use a lookup table for powers of 2, and don't use anything but primitives (no log or pow, notably). We do have a few divisions, but I see now how I could turn them into multiplications. Dealing with subnormals is tricky because the inverse of the subnormal powers of 2 are not representable.

We have one loop: a binary search in the table of powers of 2 for the double-to-bits conversion. It has a fixed number of iterations. I had tried to unroll it, but that did not perform any better.

I'll have to dig more to understand how they got rid of the comparisons, though.

I wonder whether their implementation would be faster than ours. At the time I wrote our conversions, they beat every previous implementation I was aware of hands down.

[1] https://github.com/scala-js/scala-js/blob/v1.20.2/linker-pri...