Drop __mul_used from IrOp::Mul codegen and __div_used from IrOp::Div
/ IrOp::Mod codegen (modulo reuses the same routine). The linker
skips gen_multiply / gen_divide for programs that never emit the
markers, following the same pattern already used by __audio_used /
__ppu_update_used / __sprite_cycle_used.
The optimizer already rewrites multiplies and divides by constant
powers of two into shifts (and modulo by constant powers of two
into masks), so the markers only fire for genuinely runtime math.
A program like `examples/comparisons.ne` that never multiplies or
divides now reclaims ~56 bytes of PRG; programs that use only one
of the two reclaim the other's share.
Audio goldens flip for every example that uses audio. The .ne
sources are unchanged and the pixel goldens are byte-identical —
the audio stream differs only because removing the math routines
shifts the audio tick's absolute address in PRG by 56 bytes, which
changes which of its internal branches cross 6502 page boundaries
and therefore the per-frame cycle count of a single NMI by 1-5
clocks. Over 180 frames the accumulated drift shifts APU register
write timing enough to render a different digital sample stream
at the same logical wave shape. Expected consequence of ROM-layout
change under cycle-accurate emulation; documented path per
CLAUDE.md "Updating goldens".
https://claude.ai/code/session_016kM6P7PukktBDqTZexrrAN
Every NEScript condition (`if x < N`, `while i < end`, etc.)
lowers in two IR ops: `CmpX(d, a, b)` materializes a 0/1
boolean into temp `d`, and the block's terminator
`Branch(d, t, f)` reads `d` and branches on it. The codegen
faithfully emitted both halves — `LDA / CMP / branch-to-true /
LDA #0 / JMP done / true: LDA #1 / done:`, then later
`LDA d_slot / BNE branch_t / JMP branch_f` — about 14 cycles +
13 bytes per condition.
The 6502's natural pattern is one `CMP` + one branch on the
flags it just set: 8 cycles, no register-clobber, no temp slot.
Detect the canonical pattern in `gen_block` (last op is an 8-bit
`CmpX` whose dest temp is what the terminator branches on, with
no other uses) and emit the fused form directly via a new
`gen_cmp_branch` helper. The temp's allocation, store, load, and
the terminator's branch fall away.
Bookkeeping subtlety: the source temps `a`/`b` must be retired
*after* the fused emit, not before — the original `gen_op` order
is "emit body of op, then `retire_op_sources`". Decrementing
their use counts before the CMP would free their slots while
they were still live; `load_temp(a)` would then re-allocate `a`
to whatever stale slot the free list popped next. Got hit by
this on the first attempt — the SHA-256 example dutifully
returned all-zero hashes until the order was fixed.
Updated `ir_codegen_local_label_suffix_is_bank_namespaced`: the
test was relying on `if x == 0` to emit `__ir_cmp_*` labels for
its bank-namespacing check, which the fusion now collapses into
direct branches. Switched the test source to a shift-by-variable
pattern (`x = x << n`), which always emits `__ir_shift_loop_*`
labels regardless of future cmp/branch optimizations.
Cycle savings: ~6 cycles per condition. The SHA-256 rotate
loops alone account for ~9K cycles per block. Across all
examples the cycle drift shows up as audio-tick phase shifts
in five timing-sensitive ROMs (`audio_demo`, `friendly_assets`,
`noise_triangle_sfx`, `platformer`, `sfx_pitch_envelope`); the
goldens for those are refreshed in this commit, plus
`platformer.gif` (the only demo gif whose bytes actually moved).
Verified: cargo test/clippy/fmt clean on rustc 1.95.0;
emulator harness 34/34; reproducibility diff clean; SHA-256 of
"NES" still computes to AE9145DB…4E0D.
https://claude.ai/code/session_01FRmSBruVWCufm3LsUVMs8v
Pulse-channel sfx with a multi-byte `pitch:` array used to silently
ignore everything past the first byte — the runtime audio tick
latched the period at trigger time and never updated it. Programs
that wanted a frequency sweep had no way to express it.
The compiler now compiles a per-frame pitch envelope blob alongside
the existing volume envelope when `decl.pitch` has more than one
distinct value. The blob is padded (or truncated) to the volume
envelope's length and ends in a zero sentinel so the runtime
walker stops both pointers on the same NMI. Sfx with a single
scalar pitch (or an array where every byte is the same) keep their
historical "no pitch blob, latch once" path and emit byte-identical
ROM bytes.
The runtime gains two new pieces, both gated on a new
`__sfx_pitch_used` codegen marker so programs without varying-pitch
sfx pay zero bytes:
1. `gen_audio_tick` emits a per-frame pitch update block inside
the SFX tick: read a byte through `(AUDIO_SFX_PITCH_PTR),Y`,
write it to `$4002` (pulse-1 period low), advance the pointer.
The block bails on a zero high-byte pointer so a single
program can mix scalar-pitch and varying-pitch sfx without
one clobbering the other.
2. `emit_play_pulse` seeds `AUDIO_SFX_PITCH_PTR_LO/HI` with the
pitch-blob label for varying-pitch sfx and zeros it for
scalar-pitch sfx. The per-call branch is skipped entirely
when the program has no varying-pitch sfx anywhere.
The new `examples/sfx_pitch_envelope.ne` exercises the path with
a 16-frame siren sweep. Triangle and noise per-frame pitch are
deferred — they share the same data shape but the runtime ticks
for those channels still write only their volume registers, see
docs/future-work.md for the gap.
https://claude.ai/code/session_01KEczoNUX3WmcFLfq6iAQxB
