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fix(memory): ignore CPU and DMA writes to unused I/O addresses

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Stores to I/O addresses with no register returned Unmapped and stopped the
machine. Hardware ignores them. Emulated writes there now pay their bus cost and
change nothing; host writes stay strict. The unmodeled internal memory control
register at 0x04xx0800 and all unused I/O reads remain diagnostics.

Rollback tests that used unused I/O as their failing word now run the block on
to a register that rejects the stored value: SIOMULTI2 outside multiplayer
mode, an RCNT GPIO serial IRQ, or 64-sample wave playback. Where no reachable
register can fail (JOYSTAT, POSTFLG/HALTCNT, IME, DMA3CNT), the test now checks
that the block commits and the unused word is ignored.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HhfHfHEuzv2AUTd6erW1gU
This commit is contained in:
0xrsydn 2026-10-14 11:38:51 +07:00
commit 20176716d9
16 changed files with 166 additions and 92 deletions
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29
crates/gba-core/tests/keypad.rs
View file

@ -371,8 +371,23 @@ fn cpu_store_samples_keys_then_irq_enters_on_the_following_step() {
#[test]
fn failed_block_store_does_not_commit_key_control_irq_history_or_halt_wake() {
// STMIA r0!,{r1,r2}: keypad word is valid, but RCNT's upper padding is not mapped.
let mut m = prepared(0xe8a0_0006, KEYINPUT, 0x4001_0000);
// STMIA r0!,{r1,r2}: the keypad word is valid, but RCNT enables a GPIO serial IRQ.
let mut mem = Memory::new(words(&[
0xe59f_000c,
0xe59f_100c,
0xe59f_200c,
0xe8a0_0006,
0xeaff_fffe,
KEYINPUT,
0x4001_0000,
0x0000_8100,
]))
.unwrap();
let mut cpu = Cpu::new(ROM_START);
for _ in 0..3 {
cpu.step(&mut mem).unwrap();
}
let mut m = Machine::new(cpu, mem);
press(m.memory_mut(), 1);
m.memory_mut().write16(IE, IRQ).unwrap();
let before = m.cpu().clone();
@ -380,9 +395,13 @@ fn failed_block_store_does_not_commit_key_control_irq_history_or_halt_wake() {
let timing = m.last_timing();
assert_eq!(
m.step(),
Err(MachineError::Cpu(CpuError::Memory(MemoryError::Unmapped(
KEYINPUT + 6
))))
Err(MachineError::Cpu(CpuError::Memory(
MemoryError::UnsupportedIo {
address: KEYINPUT + 5,
value: 0x81,
operation: "GPIO serial interrupt enable",
}
)))
);
assert_eq!(m.cpu(), &before);
assert_eq!(m.cycles(), cycles);