Goal
Add representation selection and unboxed value pipelines across VM/native frames so numeric, Boolean, string, object, and typed-data hot paths avoid repeated NaN-box tagging/coercion.
Scope
- Extend profiles and SSA types beyond Number-only sites: int32, uint32, double, Boolean, nullish, interned/flat string, ordinary object/array, typed-array view, BigInt where sound, and unions.
- Select unboxed local/temporary representations, explicit conversions, and phi representations with overflow/NaN/-0/infinity semantics.
- Keep values unboxed across inlined calls and loops; box only at observable storage, generic runtime, deopt, debug, or host boundaries.
- Add architecture-neutral register classes and spill/map metadata for integer, FP, SIMD, and managed values.
- Specialize common ToNumber/ToString/ToPropertyKey/equality paths without bypassing user coercion.
No-workaround rules
- No 32-bit truncation of general Numbers, canonicalization that loses NaN/-0 behavior, guessed string/object identity, or unrooted managed pointer.
- A representation mismatch deoptimizes before observable work with exact reconstruction.
Acceptance
- Differential edge suites cover overflow, -0, NaN payload behavior where observable, infinities, BigInt mixing, Symbols, throwing coercions, and representation-changing loops.
- Stack maps and deopt materialize exact boxed Values after GC relocation.
- No-GIL profile merges and guards are race-safe under TSan.
- Profiles show reduced conversions/tag checks/spills on declared #460 rows, with code-size and compilation-cost accounting.
- Original #44 and full correctness gates remain green.
Foundation
The current 8-byte NaN-boxed Value stays the canonical observable/storage representation; numeric optimizer guards and frame maps landed under #431/#432/#437.