The reset-time "no user palette" path was emitting 32 unrolled
`LDA #imm / STA $2007` pairs (~170 bytes) to write the built-in
palette. Replace it with the same indirect-loop loader the
user-palette path already uses (runtime::gen_initial_palette_load),
with the 32-byte default palette spliced into PRG under a
`__default_palette` data block. Net saving is ~120 bytes — ~20
bytes of code + 32 bytes of data vs ~170 bytes of unrolled stores.
Delete `Linker::gen_palette_load` (dead after the refactor) and its
unit test. Replace with two tests covering the observable
behaviour: the default palette bytes appear in PRG when no user
palette is declared, and the `__default_palette` label is
suppressed when the user does declare a palette.
Audio goldens flip again for audio_demo, noise_triangle_sfx, and
sfx_pitch_envelope. These are the three audio examples that don't
declare their own palette — shrinking the default-palette load
shifts their audio tick's absolute address by ~120 bytes, which
changes branch page-crossing timing and therefore the exact APU
register write sample offsets. Same class of drift as the
mul/divide gating commit.
https://claude.ai/code/session_016kM6P7PukktBDqTZexrrAN
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
Multi-tile sprites used to require one hand-written `draw` per tile,
e.g. the four-call sequence in `examples/platformer.ne`'s
`draw_player()`. The new `metasprite Name { ... }` declaration
collects parallel `dx`/`dy`/`frame` arrays plus a reference to the
underlying sprite, and `draw Name at: (x, y)` expands to one OAM
slot per tile in the IR lowering — the codegen sees N regular
DrawSprite ops, so the runtime OAM cursor allocator picks them up
without any metasprite-specific awareness.
The metasprite's `frame:` array is interpreted *relative to the
underlying sprite's base tile*: index 0 means "the first tile this
sprite owns", which is the natural reading for a 16×16 hero whose
pixel art the asset resolver split into four consecutive tiles.
The lowering walks `program.sprites` to compute base tile indices
the same way `assets::resolve_sprites` would, then folds the base
into each frame entry before storing the metasprite info. Sprites
sourced from external `@chr(...)` / `@binary(...)` files whose
bytes aren't available at parse time fall back to a one-tile
assumption — those programs are rare and can declare metasprites
against pixel-art sprites instead.
The new `examples/metasprite_demo.ne` declares a 16×16 hero sprite
and arranges its four tiles into a metasprite, then sweeps the
hero across the screen so the harness captures it mid-motion.
The new keyword is added to the lexer/token list, and the parser
accepts `sprite:` (the otherwise-keyword) as a property name in
metasprite bodies so the natural spelling parses.
https://claude.ai/code/session_01KEczoNUX3WmcFLfq6iAQxB
