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feat(cpu): use actual fetch regions for boundary bus snapshots

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0xrsydn 2026-10-06 15:13:40 +07:00
commit 0a696ea3e7
14 changed files with 465 additions and 28 deletions
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7
crates/gba-core/src/memory.rs
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@ -396,11 +396,12 @@ impl Memory {
}
}
self.drive_iwram_fetch(fetch);
let same_region = fetch.address >> 24 == pc >> 24;
// The newly accessed bus supplies the snapshot, even across a region boundary.
// Unknown local lanes and unavailable/unsupported fetch observations stay diagnostic.
let prefetch = match instruction_set {
InstructionSet::Arm => fetch.bus_word,
InstructionSet::Thumb if !same_region => None,
InstructionSet::Thumb if pc >> 24 == 3 => self.iwram_bus.snapshot(),
InstructionSet::Thumb if fetch.instruction.is_err() => None,
InstructionSet::Thumb if fetch.address >> 24 == 3 => self.iwram_bus.snapshot(),
InstructionSet::Thumb => fetch.bus_word,
};
self.cpu_access = Some(CpuAccess { pc, prefetch });