Liveness analysis: declare don't-care registers and flags at port exits

Gatchan commented

2026-11-02 17:38:43 +00:00

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Bridges currently recompute every register/flag the original leaves at exit, path by path (field batch 1: ~0.6 line of bridge per line of game code). Brief §7.1 item 4: values the original leaves dead may be declared don't-care, each declaration checked by a liveness analysis of the routine's callers (see lessons.md §1, liveness details: PHP/PLP pairing, A low/high bytes, M bit).

Scope: a tool that computes, per routine, which of A(lo/hi)/X/Y/P flags/D/DB are live after return over all call sites; the shadow comparison skips declared dead values and the fuzzer poisons them. Goal: cut bridge cost and make batches of 15-30 routines practical.

From the 2026-11-02 plan review.

Bridges currently recompute every register/flag the original leaves at exit, path by path (field batch 1: ~0.6 line of bridge per line of game code). Brief §7.1 item 4: values the original leaves dead may be declared don't-care, each declaration checked by a liveness analysis of the routine's callers (see lessons.md §1, liveness details: PHP/PLP pairing, A low/high bytes, M bit). Scope: a tool that computes, per routine, which of A(lo/hi)/X/Y/P flags/D/DB are live after return over all call sites; the shadow comparison skips declared dead values and the fuzzer poisons them. Goal: cut bridge cost and make batches of 15-30 routines practical. From the 2026-11-02 plan review.

Gatchan added this to the Phase 2 - field ports milestone

2026-11-02 17:38:43 +00:00

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2026-11-02 17:38:43 +00:00

Gatchan referenced this issue

2026-11-03 02:56:37 +00:00

Field batch 1 readability follow-ups (bridge decision tree, bridge-shaped API, accessor names) #46

Gatchan referenced this issue from a pull request that will close it,