Expand description
The multi-word integer core: every wider-than-a-word integer operation, built once from lane operations and parameterized by the lane shape.
A Builder writes a Routine; its word-level methods emit one lane operation each, and its mw_*
methods compose them into operations on multi-word values (Mw, little-endian words). The algorithms are
the textbook ones a narrow datapath uses: ripple carries, schoolbook products from multiplier-width digits
accumulated by column, restoring division, barrel shifts from constant shifts and selects, a binary-search
leading-zero count. None branches on data.