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nescript/examples/comparisons.ne
Claude 7899714af1
examples: 4 new programs covering MMC3 + other e2e gaps
Four new examples bring total coverage to 18/18 ROMs through
the jsnes smoke test:

- mmc3_per_state_split.ne — two states, each with their own
  `on scanline(N)` handler at a different line (80 vs 160).
  Pressing START transitions between them. Verifies the
  per-state MMC3 IRQ dispatch: the `__ir_mmc3_reload` helper
  CMPs `current_state` on every NMI and writes the right
  latch value to `$C000`/`$C001`, and `__irq_user` runs the
  current state's handler when the counter fires. This is
  the first example that exercises the per-state reload logic
  at runtime, not just at compile-time.

- two_player.ne — exercises `p2.button.*` reads alongside
  the default (P1) `button.*`. Two independently-moveable
  sprites sharing a single frame handler and the runtime OAM
  cursor. The runtime's NMI controller poll already reads
  both `$4016` and `$4017`, but until this example no
  runtime test actually looked at `$08` (the P2 input byte).

- function_chain.ne — five-deep user-function call chain
  (`frame -> compute -> scale -> clamp -> fold -> taper`)
  with parameter passing through ZP `$04-$07` and return
  values through A. Early returns inside nested `if`s,
  handler-local result var, mixed shift + additive transforms.
  Catches any regression in: JSR stack discipline, param slot
  layout, RTS stack unwinding, return-value flow, or the
  analyzer's call-graph / max-depth computation.

- comparisons.ne — one `if` per comparison operator
  (`==`, `!=`, `<`, `<=`, `>`, `>=`) gated on a u8 ramping
  through 0..255. Each `if` drives a pip sprite at a fixed
  column. Exercises every `CmpKind::*` case in the IR
  codegen's `gen_cmp`, catching regressions in branch-opcode
  selection (BEQ/BNE/BCC/BCS) and inverted-branch peephole
  folding.

Smoke test deltas (all 18/18 pass, with per-example floors):

    comparisons           208  (floor 150)
    function_chain        104  (floor 100)
    mmc3_per_state_split  104  (floor 80)
    two_player            104  (floor 100)

`tests/emulator/run_examples.mjs` gets new `EXAMPLE_FLOORS`
entries for each, with notes describing the expected content
so a regression prints a helpful reason.

cargo test (313 unit + 37 integration), cargo fmt --check,
cargo clippy --release -- -D warnings all clean.

https://claude.ai/code/session_014Z5y3Q9krLcAxYpZQJhZ5V
2026-04-12 20:48:31 +00:00

50 lines
1.8 KiB
Text

// Comparisons — uses every comparison operator (==, !=, <, <=,
// >, >=) to drive a different pip on screen. Each pip only
// lights up when its corresponding comparison is true, so at
// any given moment the set of visible pips is a direct readout
// of which comparisons are passing.
//
// What this exercises end-to-end:
// - All six comparison operators in `if` conditions
// - Their lowering through `CmpKind::{Eq,Ne,Lt,LtEq,Gt,GtEq}`
// in `src/codegen/ir_codegen.rs::gen_cmp`
// - Each one correctly mapping to `BEQ`/`BNE`/`BCC`/`BCS` and
// producing the expected truth value in a branch
//
// The `value` variable ramps from 0 to 255 so the six
// comparisons against MIDPOINT (=128) all fire across one cycle.
//
// Build: cargo run -- build examples/comparisons.ne
game "Comparisons" {
mapper: NROM
}
const MIDPOINT: u8 = 128
var value: u8 = 0
on frame {
// Slowly ramp through 0..255 and wrap. At the wrap the u8
// overflow resets value to 0 — intentional, the pips will
// re-animate.
value += 1
// Always-visible player sprite so the harness has at least
// one solid OAM entry every frame. Its position reflects
// the current ramp value — easy to read at a glance.
draw Player at: (value, 120)
// Each comparison drives a pip at a fixed X position along
// the top. When its condition is true, the pip draws; when
// false, the draw is skipped and the cursor's next slot
// stays hidden from the OAM clear's $FE Y byte.
if value == MIDPOINT { draw Pip at: ( 32, 16) }
if value != MIDPOINT { draw Pip at: ( 64, 16) }
if value < MIDPOINT { draw Pip at: ( 96, 16) }
if value <= MIDPOINT { draw Pip at: (128, 16) }
if value > MIDPOINT { draw Pip at: (160, 16) }
if value >= MIDPOINT { draw Pip at: (192, 16) }
}
start Main