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LR35902: Optimize CPU loop to prevent no-op cycles from being calculated

This commit is contained in:
Jeffrey Pfau 2016-02-14 01:57:53 -08:00
parent ed94288902
commit c89c3964db
2 changed files with 17 additions and 10 deletions
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9
src/lr35902/lr35902.c
View File

@ -148,8 +148,15 @@ void LR35902Tick(struct LR35902Core* cpu) {
}
void LR35902Run(struct LR35902Core* cpu) {
while (cpu->cycles < cpu->nextEvent) {
while (true) {
_LR35902Step(cpu);
if (cpu->cycles >= cpu->nextEvent) {
break;
} else if (cpu->executionState < LR35902_CORE_EXECUTE) {
// Silly hack: keep us from calling step if we know the next step is a no-op
++cpu->cycles;
++cpu->executionState;
}
}
cpu->irqh.processEvents(cpu);
}

18
src/lr35902/lr35902.h
View File

@ -36,16 +36,16 @@ union FlagRegister {
#pragma pack(pop)
enum LR35902ExecutionState {
LR35902_CORE_FETCH = 0,
LR35902_CORE_IDLE_0,
LR35902_CORE_IDLE_1,
LR35902_CORE_EXECUTE = 3,
LR35902_CORE_FETCH = 3,
LR35902_CORE_IDLE_0 = 0,
LR35902_CORE_IDLE_1 = 1,
LR35902_CORE_EXECUTE = 2,
LR35902_CORE_MEMORY_LOAD = 4,
LR35902_CORE_MEMORY_STORE = 8,
LR35902_CORE_READ_PC = 12,
LR35902_CORE_STALL = 16,
LR35902_CORE_OP2 = 20
LR35902_CORE_MEMORY_LOAD = 7,
LR35902_CORE_MEMORY_STORE = 11,
LR35902_CORE_READ_PC = 15,
LR35902_CORE_STALL = 19,
LR35902_CORE_OP2 = 23
};
struct LR35902Memory {