Having 2 passes can enable so much more than a single pass.
Another alternative could be to have a first pass make notes in a separate buffer while parsing the input. The bandwidth of the note taking and reading can be much much lower than that required for fetching the billions of parameters.
Consider the flood fill algorithm or union-find algorithm, which feels magical upon first exposure.
https://en.wikipedia.org/wiki/Hoshen%E2%80%93Kopelman_algori...
Having 2 passes can enable so much more than a single pass.
Another alternative could be to have a first pass make notes in a separate buffer while parsing the input. The bandwidth of the note taking and reading can be much much lower than that required for fetching the billions of parameters.