0xrsydn/gameboy-rust
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feat(timing): implement nominal Game Pak opcode prefetch

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0xrsydn 2026-10-06 20:32:54 +07:00
commit 8f22092e06
25 changed files with 1062 additions and 124 deletions
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5
crates/gba-core/src/cpu/timing.rs
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@ -59,7 +59,7 @@ impl Cpu {
let fetched = self.fetch(memory)?;
let code_kind = memory.cpu_code_kind(self.next_fetch_kind());
// Source timing precedes data accesses and their WAITCNT writes.
memory.begin_cpu_timing();
memory.begin_cpu_timing(fetched.fill.is_some());
memory.record_code_access(
fetched.lookahead.address(),
self.instruction_set.access_width(),
@ -75,12 +75,13 @@ impl Cpu {
/// A missing discarded fetch cannot prevent entry or become a current-slot error.
pub(crate) fn take_irq_timed(&mut self, memory: &mut Memory) -> Option<StepTiming> {
let state = self.instruction_set;
let cold = !self.has_retained_pipeline();
let address = self.pc().wrapping_add(2 * state.width());
let kind = memory.cpu_code_kind(self.next_fetch_kind());
if !self.take_interrupt(memory.irq_pending(), false) {
return None;
}
memory.begin_cpu_timing();
memory.begin_cpu_timing(cold);
let fetch = memory.fetch_instruction(address, state);
memory.record_code_access(fetch.address(), state.access_width(), kind);
memory.discarded_cpu_fetch(&fetch);