Use dyn dispatch to reduce monomorphization bloat (~177KB savings) #516
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Add #[inline(never)] wrapper pattern to prevent monomorphization of heavy process functions across multiple input types. The public API remains generic for ergonomics, but delegates to non-generic internal functions that use dynamic dispatch. Changes: - decoder.rs: Add process_dyn/skip_frame_dyn with #[inline(never)] - process.rs: Use &mut dyn JxlBitstreamInput - codestream_parser/mod.rs: Use &mut dyn JxlBitstreamInput - box_parser.rs: Use &mut dyn JxlBitstreamInput Binary size impact (with 3 input types): - Before: 4,065 KB (.text), 3x86KB process copies - After: 3,883 KB (.text), 1x86KB process copy - Savings: ~177 KB
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Summary
Add
#[inline(never)]wrapper pattern to prevent monomorphization of heavy process functions across multiple input types. The public API remains generic for ergonomics, but delegates to non-generic internal functions that use dynamic dispatch.Changes
decoder.rs: Addprocess_dyn/skip_frame_dynwith#[inline(never)]process.rs: Use&mut dyn JxlBitstreamInputcodestream_parser/mod.rs: Use&mut dyn JxlBitstreamInputbox_parser.rs: Use&mut dyn JxlBitstreamInputBinary size impact
Tested with example using 3 different input types (
&[u8],BufReader<Cursor>,BufReader<File>):Why this approach?
We evaluated 3 options:
#[inline(never)]on internal functions only → didn't work (public API still monomorphized)&mut dyn→ works but breaks API#[inline(never)]internal → works, API compatible ✓Test plan
cargo build --releasepassescargo fmtpasses