0xrsydn/gameboy-rust
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feat(cpu): retain fetch access kinds across instruction execution

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0xrsydn 2026-10-06 16:53:05 +07:00
commit 86321f0071
21 changed files with 637 additions and 61 deletions
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11
crates/gba-core/src/cpu.rs
View file

@ -42,6 +42,8 @@ mod fetch_boundary_tests;
#[cfg(test)]
mod fetch_history_tests;
#[cfg(test)]
mod fetch_sequence_tests;
#[cfg(test)]
mod fetch_timing_tests;
#[cfg(test)]
mod instruction_tests;
@ -176,7 +178,7 @@ impl InstructionSet {
}
/// ARM/Thumb interpreter with register banks, instruction buffering, and nominal costs.
/// Clone/equality include buffered fetch results and their instruction-set tag.
/// Clone/equality include buffered fetch results, instruction state, and next fetch kind.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Cpu {
registers: [u32; 16],
@ -242,7 +244,7 @@ impl Cpu {
) -> Result<(), CpuError> {
let pipeline::Fetched {
instruction,
continuation,
mut continuation,
lookahead,
fill,
} = fetched;
@ -250,14 +252,15 @@ impl Cpu {
// Always clear the access context, including on diagnostic errors.
let pc = self.pc();
let instruction_set = self.instruction_set;
let refill = self.instruction_refills(instruction);
let summary = self.instruction_summary(instruction);
memory.begin_cpu_access(pc, self.instruction_set, fill.as_ref(), &lookahead);
let result = self.execute_instruction(instruction, memory);
memory.end_cpu_access(result.is_ok());
if result.is_ok() {
if refill {
if summary.refill {
self.refill_pipeline(memory);
} else {
continuation.next_access = summary.next_fetch_kind();
// A state change without an ordinary refill starts a cold sequence.
self.pipeline = if self.instruction_set == instruction_set
&& self.pc() == pc.wrapping_add(instruction_set.width())

9
crates/gba-core/src/cpu/dma_resume_tests.rs
View file

@ -165,6 +165,8 @@ fn failed_cpu_fetch_and_data_access_preserve_resume_until_success() {
assert_eq!(timing.code_cycles, 8);
assert_eq!(timing.data_cycles, 6);
assert_eq!(timing.internal_cycles, 1);
// The successful load creates a new sequence break after consuming DMA resume.
assert_eq!(cpu.step_timed(&mut bus).unwrap().code_cycles, 8);
assert_eq!(cpu.step_timed(&mut bus).unwrap().code_cycles, 6);
}
@ -191,7 +193,7 @@ fn host_accesses_and_clock_advances_do_not_consume_resume_but_untimed_cpu_does()
fn skipped_conditions_stores_and_boundaries_consume_resume_without_double_charging() {
for (pc, instruction, data) in [
(PC, 0x0591_0000, 0), // LDREQ skipped: Z is clear.
(PC, 0xe581_0000, 6), // STR already has an N code access.
(PC, 0xe581_0000, 6), // STR uses DMA's N, then breaks the following fetch.
(ROM_START + 0x20000 - 8, 0xe1a0_0000, 0), // PC+8 fetch boundary already forces N.
] {
let (mut cpu, mut bus) = program(false, pc, instruction);
@ -199,6 +201,10 @@ fn skipped_conditions_stores_and_boundaries_consume_resume_without_double_chargi
let timing = cpu.step_timed(&mut bus).unwrap();
assert_eq!(timing.code_cycles, 8);
assert_eq!(timing.data_cycles, data);
assert_eq!(
cpu.step_timed(&mut bus).unwrap().code_cycles,
if data == 6 { 8 } else { 6 }
);
assert_eq!(cpu.step_timed(&mut bus).unwrap().code_cycles, 6);
}
}
@ -210,6 +216,7 @@ fn waitcnt_cpu_store_uses_old_code_cost_but_dma_store_applies_before_resume() {
cpu.registers[1] = WAITCNT;
dma(&mut bus);
assert_eq!(cpu.step_timed(&mut bus).unwrap().code_cycles, 8);
assert_eq!(cpu.step_timed(&mut bus).unwrap().code_cycles, 5); // Store breaks the next fetch; new N=3, S=2.
assert_eq!(cpu.step_timed(&mut bus).unwrap().code_cycles, 4);
let (mut cpu, mut bus) = program(false, PC, 0xe1a0_0000);

381
crates/gba-core/src/cpu/fetch_sequence_tests.rs Normal file
View file

@ -0,0 +1,381 @@
//! Original instruction-pair tests. Expected access kinds do not use CPU summaries.
use super::*;
use crate::{
dma::{DMA_BASE, DMA_STRIDE},
io::{HALTCNT, IE, IME, TIMER_BASE, WAITCNT},
machine::{Machine, StepKind},
memory::{BIOS_SIZE, ROM_CAPACITY, ROM_START},
timing::AccessKind,
};
const PC: u32 = ROM_START + 0x100;
const DATA: u32 = 0x0300_1000;
const ARM_NOP: u32 = 0xe1a0_0000;
const THUMB_NOP: u32 = 0x46c0;
fn program(thumb: bool, pc: u32, instructions: &[u32]) -> (Cpu, Memory) {
let width = if thumb { 2 } else { 4 };
let pattern = if thumb { 0x46c0_46c0 } else { ARM_NOP };
let offset = (pc & 0x01ff_ffff) as usize;
let length = (offset + 4 * width).clamp(0x20020, ROM_CAPACITY);
let mut rom = pattern.to_le_bytes().repeat(length.div_ceil(4));
for (index, instruction) in instructions.iter().enumerate() {
rom[offset + index * width..offset + (index + 1) * width]
.copy_from_slice(&instruction.to_le_bytes()[..width]);
}
let mut cpu = Cpu::new(pc);
if thumb {
cpu.instruction_set = InstructionSet::Thumb;
}
cpu.registers[0] = 7;
cpu.registers[1] = DATA;
cpu.registers[13] = DATA + 64;
(
cpu,
Memory::with_bios(rom, ARM_NOP.to_le_bytes().repeat(BIOS_SIZE / 4)).unwrap(),
)
}
#[test]
fn arm_instruction_effects_select_the_following_fetch_not_their_own() {
for (instruction, breaks) in [
(ARM_NOP, false),
(0xe1a0_0082, false), // Immediate shift.
(0xe10f_0000, false),
(0xe321_f01f, false), // MRS / MSR.
(0x0591_0000, false),
(0x0581_0000, false), // Skipped load/store.
(0x0000_0291, false),
(0x01a0_0312, false), // Skipped multiply/shift.
(0xe591_0000, true),
(0xe581_0000, true), // Word load/store.
(0xe5d1_0000, true),
(0xe5c1_0000, true), // Byte load/store.
(0xe1d1_00b0, true),
(0xe1c1_00b0, true), // Halfword load/store.
(0xe1d1_00d0, true),
(0xe1d1_00f0, true), // Signed byte/halfword.
(0xe891_0005, true),
(0xe881_0005, true), // Block load/store.
(0xe881_0000, true), // Empty block store.
(0xe101_0092, true),
(0xe141_0092, true), // SWP/SWPB.
(0xe1a0_0312, true), // Register shift, zero shift amount.
(0xe000_0392, true),
(0xe020_4392, true), // MUL/MLA.
(0xe085_4392, true),
(0xe0a5_4392, true), // UMULL/UMLAL.
(0xe0c5_4392, true),
(0xe0e5_4392, true), // SMULL/SMLAL.
] {
check_pair(false, instruction, breaks);
}
}
#[test]
fn thumb_instruction_effects_select_the_following_fetch_not_their_own() {
for (instruction, breaks) in [
(THUMB_NOP, false),
(0x0040, false),
(0x3001, false),
(0x4008, false),
(0xb001, false),
(0xf000, false), // AND, SP adjust, BL prefix.
(0xd000, false), // Skipped BEQ (Z clear).
(0x4800, true), // Literal load.
(0x6008, true),
(0x6808, true),
(0x7008, true),
(0x7808, true),
(0x8008, true),
(0x8808, true),
(0x9000, true),
(0x9800, true),
(0x5088, true),
(0x5288, true),
(0x5488, true),
(0x5688, true),
(0x5888, true),
(0x5a88, true),
(0x5c88, true),
(0x5e88, true),
(0xb405, true),
(0xbc05, true),
(0xc105, true),
(0xc905, true),
(0xb400, true),
(0xc100, true), // Empty stores.
(0x4090, true),
(0x40d0, true),
(0x4110, true),
(0x41d0, true), // Register shifts by r2=0.
(0x4348, true), // MUL.
] {
check_pair(true, instruction, breaks);
}
}
fn check_pair(thumb: bool, instruction: u32, breaks: bool) {
for window in 0..3 {
let (cpu, mut memory) = program(thumb, PC + window as u32 * 0x0200_0000, &[instruction]);
for first in 0..4 {
for second in 0..2 {
for prefetch in [0, 0x4000] {
memory
.write16(
WAITCNT,
(first << [2, 5, 8][window])
| (second << [4, 7, 10][window])
| prefetch,
)
.unwrap();
let n = [5, 4, 3, 9][first as usize];
let s = if second == 1 { 2 } else { [3, 5, 9][window] };
let extra = if thumb { 0 } else { s };
let mut cpu = cpu.clone();
// Cold startup keeps the existing nominal S policy.
assert_eq!(
cpu.step_timed(&mut memory).unwrap().code_cycles,
s + extra,
"first fetch for {instruction:08x}"
);
assert_eq!(
cpu.step_timed(&mut memory).unwrap().code_cycles,
if breaks { n + extra } else { s + extra },
"following fetch for {instruction:08x}"
);
assert_eq!(cpu.step_timed(&mut memory).unwrap().code_cycles, s + extra);
assert_eq!(memory.cycles(), 0);
}
}
}
}
}
#[test]
fn timed_and_untimed_execution_and_clones_retain_the_same_next_fetch_kind() {
for thumb in [false, true] {
let instruction = if thumb { 0x6808 } else { 0xe591_0000 };
let (mut timed, mut a) = program(thumb, PC, &[instruction]);
let (mut plain, mut b) = program(thumb, PC, &[instruction]);
timed.step_timed(&mut a).unwrap();
plain.step(&mut b).unwrap();
assert_eq!(timed, plain);
let mut copy = plain.clone();
for expected in [if thumb { 5 } else { 8 }, if thumb { 3 } else { 6 }] {
assert_eq!(timed.step_timed(&mut a).unwrap().code_cycles, expected);
assert_eq!(copy.step_timed(&mut b).unwrap().code_cycles, expected);
assert_eq!(timed, copy);
}
}
}
#[test]
fn following_transfers_branches_and_skipped_conditions_consume_the_prior_sequence_break() {
for thumb in [false, true] {
let load = if thumb { 0x6808 } else { 0xe591_0000 };
let store = if thumb { 0x6008 } else { 0xe581_0000 };
let branch = if thumb { 0xe000 } else { 0xea00_0000 };
let skipped = if thumb { 0xd000 } else { 0x0581_0000 };
for second in [load, store, branch, skipped] {
let (mut cpu, mut memory) = program(thumb, PC, &[load, second]);
cpu.step(&mut memory).unwrap();
let cost = cpu.step_timed(&mut memory).unwrap();
let n = if thumb { 5 } else { 8 };
let s = if thumb { 3 } else { 6 };
assert_eq!(
cost.code_cycles,
if second == branch { n + n + s } else { n }
);
assert_eq!(
cpu.step_timed(&mut memory).unwrap().code_cycles,
if second == branch || second == skipped {
s
} else {
n
}
);
}
}
}
#[test]
fn pc_load_refills_restore_sequential_fetches_after_data_and_internal_cycles() {
for thumb in [false, true] {
let instruction = if thumb { 0xbd00 } else { 0xe591_f000 };
let (mut cpu, mut memory) = program(thumb, PC, &[instruction]);
memory
.write32(if thumb { DATA + 64 } else { DATA }, PC + 0x20)
.unwrap();
let cost = cpu.step_timed(&mut memory).unwrap();
assert_eq!(cost.code_cycles, if thumb { 11 } else { 20 });
assert_eq!(cost.data_cycles, 1);
assert_eq!(cost.internal_cycles, 1);
assert_eq!(
cpu.step_timed(&mut memory).unwrap().code_cycles,
if thumb { 3 } else { 6 }
);
}
}
#[test]
fn dma_override_coalesces_with_cpu_history_and_does_not_replay_the_penalty() {
for thumb in [false, true] {
for instruction in [
if thumb { 0x6808 } else { 0xe591_0000 },
if thumb { THUMB_NOP } else { ARM_NOP },
] {
let (mut cpu, mut memory) = program(thumb, PC, &[instruction]);
cpu.step(&mut memory).unwrap();
let dma = DMA_BASE + 3 * DMA_STRIDE;
memory.write32(dma, DATA).unwrap();
memory.write32(dma + 4, DATA + 128).unwrap();
memory.write32(dma + 8, 0x8400_0001).unwrap();
memory.step_dma().unwrap().unwrap();
assert_eq!(
cpu.step_timed(&mut memory).unwrap().code_cycles,
if thumb { 5 } else { 8 }
);
assert_eq!(
cpu.step_timed(&mut memory).unwrap().code_cycles,
if thumb { 3 } else { 6 }
);
}
}
}
#[test]
fn irq_uses_retained_incoming_kind_before_invalidating_the_interrupted_buffer() {
for thumb in [false, true] {
for instruction in [
if thumb { 0x6808 } else { 0xe591_0000 },
if thumb { THUMB_NOP } else { ARM_NOP },
] {
let (mut cpu, mut memory) = program(thumb, PC, &[instruction]);
cpu.step(&mut memory).unwrap();
memory.write16(IE, 8).unwrap();
memory.write16(IME, 1).unwrap();
memory.write32(TIMER_BASE, 0x00c0_ffff).unwrap();
memory.advance_cycles(1);
let n = instruction != if thumb { THUMB_NOP } else { ARM_NOP };
let expected = match (thumb, n) {
(true, true) => 7,
(true, false) => 5,
(false, true) => 10,
(false, false) => 8,
};
let mut machine = Machine::new(cpu, memory);
let start = machine.cycles();
assert_eq!(machine.step().unwrap(), StepKind::IrqEntry);
assert_eq!(machine.last_timing().code_cycles, expected);
assert_eq!(machine.cycles() - start, u64::from(expected));
assert_eq!(machine.cpu().next_fetch_kind(), AccessKind::Sequential);
assert_eq!(machine.step().unwrap(), StepKind::Instruction);
assert_eq!(machine.last_timing().code_cycles, 1);
}
}
}
#[test]
fn failed_execution_retains_next_kind_and_retry_does_not_consume_it() {
for thumb in [false, true] {
let load = if thumb { 0x6808 } else { 0xe591_0000 };
let (mut cpu, mut memory) = program(thumb, PC, &[load, load]);
cpu.step(&mut memory).unwrap();
cpu.registers[1] = 0x0e00_0000;
let before = cpu.clone();
for _ in 0..2 {
assert!(cpu.step_timed(&mut memory).is_err());
assert_eq!(cpu, before);
assert_eq!(cpu.next_fetch_kind(), AccessKind::NonSequential);
}
cpu.registers[1] = DATA;
assert_eq!(
cpu.step_timed(&mut memory).unwrap().code_cycles,
if thumb { 5 } else { 8 }
);
assert_eq!(
cpu.step_timed(&mut memory).unwrap().code_cycles,
if thumb { 5 } else { 8 }
);
assert_eq!(memory.cycles(), 0);
}
}
#[test]
fn missing_current_slot_and_masked_irq_preserve_the_pending_cpu_sequence() {
for thumb in [false, true] {
let instruction: u32 = if thumb { 0x6808 } else { 0xe591_0000 };
let width = if thumb { 2 } else { 4 };
let mut memory = Memory::new(instruction.to_le_bytes()[..width].to_vec()).unwrap();
let mut cpu = Cpu::new(ROM_START);
if thumb {
cpu.instruction_set = InstructionSet::Thumb;
}
cpu.registers[1] = DATA;
cpu.step(&mut memory).unwrap();
assert_eq!(cpu.next_fetch_kind(), AccessKind::NonSequential);
let before = cpu.clone();
assert!(cpu.step_timed(&mut memory).is_err());
assert_eq!(cpu, before);
memory.write16(IE, 8).unwrap();
memory.write16(IME, 1).unwrap();
memory.write32(TIMER_BASE, 0x00c0_ffff).unwrap();
memory.advance_cycles(1);
cpu.irq_disabled = true;
let before = cpu.clone();
assert_eq!(cpu.take_irq_timed(&mut memory), None);
assert_eq!(cpu, before);
// A debugger PC discontinuity cannot reuse the old sequence's access kind.
cpu.registers[15] = PC;
assert_eq!(cpu.next_fetch_kind(), AccessKind::Sequential);
}
}
#[test]
fn host_accesses_and_halt_idle_preserve_kind_but_debugger_invalidation_starts_cold() {
let (mut cpu, mut memory) = program(false, PC, &[0xe591_0000]);
cpu.step(&mut memory).unwrap();
memory.read32(DATA).unwrap();
memory.write32(DATA, 1).unwrap();
memory.advance_cycles(7);
memory.write8(HALTCNT, 0).unwrap();
let mut machine = Machine::new(cpu, memory);
assert_eq!(machine.step().unwrap(), StepKind::HaltIdle);
assert_eq!(machine.cpu().next_fetch_kind(), AccessKind::NonSequential);
let mut cpu = machine.cpu().clone();
cpu.invalidate_pipeline();
assert_eq!(cpu.next_fetch_kind(), AccessKind::Sequential);
assert_eq!(cpu.step_timed(machine.memory_mut()).unwrap().code_cycles, 6);
}
#[test]
fn page_and_wait_window_crossings_apply_the_retained_kind_at_the_new_fetch_address() {
for thumb in [false, true] {
let width = if thumb { 2 } else { 4 };
for (boundary, waitcnt, n, s) in [
(
ROM_START + 0x20000,
0,
if thumb { 5 } else { 8 },
if thumb { 3 } else { 6 },
),
(
0x0a00_0000,
0x80,
if thumb { 5 } else { 7 },
if thumb { 2 } else { 4 },
),
] {
let (mut cpu, mut memory) = program(
thumb,
boundary - 3 * width,
&[if thumb { 0x6808 } else { 0xe591_0000 }],
);
memory.write16(WAITCNT, waitcnt).unwrap();
cpu.step(&mut memory).unwrap();
assert_eq!(cpu.step_timed(&mut memory).unwrap().code_cycles, n);
assert_eq!(cpu.step_timed(&mut memory).unwrap().code_cycles, s);
}
}
}

3
crates/gba-core/src/cpu/fetch_timing_tests.rs
View file

@ -164,9 +164,10 @@ fn a_boundary_waitcnt_store_uses_old_fetch_settings_and_the_next_fetch_uses_new_
cpu.registers[0] = 0xc0; // WS1 N=3, S=2.
cpu.registers[1] = WAITCNT;
let cost = cpu.step_timed(&mut memory).unwrap();
assert_eq!(cost.code_cycles, 10); // Old WS1 N=5, S=5 at lookahead 0x0a000004.
assert_eq!(cost.code_cycles, 10); // Old WS1 S+S=10 at lookahead 0x0a000004.
assert_eq!(cost.data_cycles, 1);
assert_eq!(memory.waitcnt(), 0xc0);
assert_eq!(cpu.step_timed(&mut memory).unwrap().code_cycles, 5); // Store's next fetch: new N+S.
assert_eq!(cpu.step_timed(&mut memory).unwrap().code_cycles, 4);
}

22
crates/gba-core/src/cpu/pipeline.rs
View file

@ -1,6 +1,9 @@
//! ARM/Thumb instruction buffering. Timing and bus ownership remain separate.
//! ARM/Thumb instruction buffering and the next CPU fetch access kind.
use super::{Cpu, CpuError, InstructionSet};
use crate::memory::{InstructionFetch, Memory, MemoryError};
use crate::{
memory::{InstructionFetch, Memory, MemoryError},
timing::AccessKind,
};
#[derive(Debug, Clone, PartialEq, Eq)]
pub(super) struct Pipeline {
@ -9,6 +12,7 @@ pub(super) struct Pipeline {
// Deferred strict-fetch results for the next execute and decode positions.
// Thumb halfwords are zero-extended; their upper bits are not another opcode.
instructions: [Result<u32, MemoryError>; 2],
pub(super) next_access: AccessKind,
}
pub(super) struct Fetched {
@ -21,11 +25,21 @@ pub(super) struct Fetched {
impl Cpu {
/// Discard buffered instructions after debugger code edits or rebinding memory.
/// Ordinary CPU/DMA stores and host inspection must not call this automatically.
/// The next step fills from its current PC/state without adding nominal cycles.
/// The next step uses nominal S startup with no separate fill charge.
/// This also discards the prior CPU fetch kind, but not Memory's DMA override.
pub fn invalidate_pipeline(&mut self) {
self.pipeline = None;
}
/// Cold/debugger entry keeps the existing nominal S startup policy.
/// A mismatched PC/state cannot reuse another sequence's access kind.
pub(super) fn next_fetch_kind(&self) -> AccessKind {
self.pipeline
.as_ref()
.filter(|pipe| pipe.pc == self.pc() && pipe.instruction_set == self.instruction_set)
.map_or(AccessKind::Sequential, |pipe| pipe.next_access)
}
pub(super) fn fetch(&self, memory: &Memory) -> Result<Fetched, CpuError> {
let pc = self.pc();
let instruction_set = self.instruction_set;
@ -53,6 +67,7 @@ impl Cpu {
pc: pc.wrapping_add(width),
instruction_set,
instructions: [decode, fetched.instruction.clone()],
next_access: AccessKind::Sequential, // Set from execution only on success.
},
lookahead: fetched,
fill,
@ -73,6 +88,7 @@ impl Cpu {
pc,
instruction_set,
instructions: fetches.map(|fetch| fetch.instruction),
next_access: AccessKind::Sequential,
});
}
}

42
crates/gba-core/src/cpu/timing.rs
View file

@ -1,6 +1,6 @@
//! Nominal ARM7 instruction-cycle summaries, separate from instruction semantics.
//! Code costs use source-fetch and target-pair addresses; data costs use actual bus accesses.
//! Source access kinds remain instruction-local nominal summaries.
//! Successful execution records the next fetch kind in the instruction buffer.
use super::{Cpu, CpuError, InstructionSet};
use crate::{
@ -9,13 +9,23 @@ use crate::{
};
#[derive(Default)]
struct Summary {
code_kind: AccessKind,
refill: bool,
pub(super) struct Summary {
data: bool,
pub(super) refill: bool,
internal: u32,
}
impl Summary {
/// Data accesses and internal cycles break the following code sequence.
/// A refill ends with a sequential target fetch and starts a new sequence.
pub(super) fn next_fetch_kind(&self) -> AccessKind {
if !self.refill && (self.data || self.internal != 0) {
AccessKind::NonSequential
} else {
AccessKind::Sequential
}
}
fn branch() -> Self {
Self {
refill: true,
@ -25,11 +35,7 @@ impl Summary {
fn transfer(load: bool, pc: bool) -> Self {
Self {
code_kind: if load {
AccessKind::Sequential
} else {
AccessKind::NonSequential
},
data: true,
refill: load && pc,
internal: u32::from(load),
}
@ -52,15 +58,12 @@ impl Cpu {
pub fn step_timed(&mut self, memory: &mut Memory) -> Result<StepTiming, CpuError> {
let fetched = self.fetch(memory)?;
let instruction = fetched.instruction;
let summary = match self.instruction_set {
InstructionSet::Arm => self.arm_summary(instruction),
InstructionSet::Thumb => self.thumb_summary(instruction),
};
let summary = self.instruction_summary(instruction);
let fetch_address = fetched.lookahead.address();
let width = self.instruction_set.access_width();
// A WAITCNT store affects subsequent instructions, not this code access.
let waitcnt = memory.waitcnt();
let code_kind = memory.cpu_code_kind(summary.code_kind);
let code_kind = memory.cpu_code_kind(self.next_fetch_kind());
memory.begin_data_timing();
let result = self.execute_fetched(fetched, memory);
let data_cycles = memory.end_data_timing();
@ -82,11 +85,11 @@ impl Cpu {
pub(crate) fn take_irq_timed(&mut self, memory: &mut Memory) -> Option<StepTiming> {
let state = self.instruction_set;
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;
}
let waitcnt = memory.waitcnt();
let kind = memory.cpu_code_kind(AccessKind::Sequential);
let fetch = memory.fetch_instruction(address, state);
memory.discarded_cpu_fetch(&fetch);
self.refill_pipeline(memory);
@ -122,6 +125,7 @@ impl Cpu {
}
if instruction & 0x0fb0_0ff0 == 0x0100_0090 {
return Summary {
data: true,
internal: 1,
..Summary::default()
}; // SWP: two N data accesses
@ -158,12 +162,12 @@ impl Cpu {
}
}
// Share the existing control-flow classification with bounded bus history.
// Classify before instruction effects in both timed and untimed execution.
// A PC write can refill even when its target equals the sequential address.
pub(super) fn instruction_refills(&self, instruction: u32) -> bool {
pub(super) fn instruction_summary(&self, instruction: u32) -> Summary {
match self.instruction_set {
InstructionSet::Arm => self.arm_summary(instruction).refill,
InstructionSet::Thumb => self.thumb_summary(instruction).refill,
InstructionSet::Arm => self.arm_summary(instruction),
InstructionSet::Thumb => self.thumb_summary(instruction),
}
}

4
crates/gba-core/src/cpu/timing_tests.rs
View file

@ -338,9 +338,9 @@ fn waitcnt_store_charges_old_code_settings_and_new_settings_apply_next_step() {
let mut cpu = Cpu::new(ROM_START);
cpu.registers[0] = WAITCNT;
cpu.registers[1] = 0x18; // N=3 and S=2 per halfword
assert_eq!(cpu.step_timed(&mut memory).unwrap(), expected(8, 1, 0));
assert_eq!(cpu.step_timed(&mut memory).unwrap(), expected(6, 1, 0)); // Incoming S at old WAITCNT.
assert_eq!(memory.waitcnt(), 0x18);
assert_eq!(cpu.step_timed(&mut memory).unwrap(), expected(4, 0, 0));
assert_eq!(cpu.step_timed(&mut memory).unwrap(), expected(5, 0, 0)); // Following N at new WAITCNT.
}
#[test]

4
crates/gba-core/tests/machine.rs
View file

@ -65,8 +65,8 @@ fn timer_demo_configures_hardware_in_cpu_code_and_handles_exactly_one_irq() {
assert_eq!(machine.cpu().registers()[10], 1);
assert_eq!(machine.memory().read16(IF).unwrap(), 0);
assert_eq!(machine.memory().read16(TIMER_BASE + 2).unwrap(), 0);
// IRQ entry gains five cycles before the timer stops; return loses five afterward.
assert_eq!(machine.memory().read16(TIMER_BASE).unwrap(), 0xfff9);
// Persistent fetch kinds move costs between setup instructions and the running timer.
assert_eq!(machine.memory().read16(TIMER_BASE).unwrap(), 0xfffb);
for _ in 0..100 {
assert_eq!(machine.step().unwrap(), StepKind::Instruction);
}