swc Optimize `atom!` for inlinable strings and adopt it across swc

Optimize `atom!` for inlinable strings and adopt it across swc

Open lukesandberg opened this issue 5 months ago • 3 comments

This ports an optimization from Turbopacks rcstr implementation to swc

Atom has an optimization to store small strings inline, this optimizes the atom! macro to produce a constant Atom struct when possible instead using a once_cell::Lazy. This shifts work from runtime to compile time and should be a small code size optimization as well.

Many of the literal Atoms constructed in swc are for things like keywords, the vast majority of which fit within the 7 byte limit. Even for the pesky ones that don't (looking at you function!), we still optimize construction by leveraging the once_cell.

At the same time replace ~all calls to "<string-literal>".into() that were constructing an Atom with a call to the atom! macro., which should improve the impact of the change.