Claude 53c454669d

runtime: gate controller-1 reads, skip whole input block when unused ...

With `has_p1_input` false, drop the three-instruction JOY1 shift
block from the NMI's input loop. With both `has_p1_input` and
`has_p2_input` false, drop the strobe write to \$4016 as well — the
entire controller-sampling block disappears. Audio- or compute-only
programs that never touch `button.*` pay zero cycles for input
sampling.

The IR codegen's `__p1_input_used` marker (emitted alongside the
P2 one in the previous commit) now drives this path through a new
`NmiOptions::has_p1_input` bool and an `NmiOptions::any_input()`
helper that's true when either port is active.

Savings for a truly non-interactive program:
 - ~18 bytes of NMI code (strobe + loop scaffold + the 6 bytes of
   per-port shifting that the P2 gate already caught).
 - ~80 cycles per frame (the 4 cycles of strobe plus the 5 cycles
   of DEX/BNE × 8 that the loop would otherwise run; net of the
   loop overhead that's ~40 cycles, but jsnes measures it as ~80
   because the JOY1 read itself was 4c × 8).

Two audio goldens flip — the two audio-only examples whose NMI
shifts forward by ~27 bytes once the strobe-and-loop block is
gone. Same cycle-accurate-APU-timing drift as every prior NMI
layout change.

https://claude.ai/code/session_016kM6P7PukktBDqTZexrrAN

2026-04-16 21:15:09 +00:00

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