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Made an attempt to reduce cost of the most-likely path.

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This commit is contained in:
Thomas Harte 2016-06-28 18:46:00 -04:00
parent b0dae01e8f
commit 6e698e908e
1 changed files with 26 additions and 18 deletions
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44
Processors/6502/CPU6502.hpp
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@ -455,11 +455,17 @@ template <class T> class Processor {
int _cycles_left_to_run;
bool _ready_line_is_enabled;
bool _reset_line_is_enabled;
bool _irq_line_is_enabled, _irq_request_history[2];
bool _nmi_line_is_enabled;
enum InterruptRequestFlags: uint8_t {
Reset = 0x80,
IRQ = 0x40,
NMI = 0x20,
};
uint8_t _interrupt_requests;
bool _ready_is_active;
bool _ready_line_is_enabled;
bool _irq_line_is_enabled, _irq_request_history;
/*!
Gets the program representing an RST response.
@ -528,8 +534,8 @@ template <class T> class Processor {
_scheduledPrograms{nullptr, nullptr, nullptr, nullptr},
_interruptFlag(Flag::Interrupt),
_s(0),
_nextBusOperation(BusOperation::None)
_nextBusOperation(BusOperation::None),
_interrupt_requests(0)
{
// only the interrupt flag is defined upon reset but get_flags isn't going to
// mask the other flags so we need to do that, at least
@ -576,13 +582,15 @@ template <class T> class Processor {
#define checkSchedule(op) \
if(!_scheduledPrograms[scheduleProgramsReadPointer]) {\
scheduleProgramsReadPointer = _scheduleProgramsWritePointer = scheduleProgramProgramCounter = 0;\
if(_reset_line_is_enabled) {\
schedule_program(get_reset_program());\
} else if(_nmi_line_is_enabled) {\
_nmi_line_is_enabled = false;\
schedule_program(get_nmi_program());\
} else if(_irq_request_history[0]) {\
schedule_program(get_irq_program());\
if(_interrupt_requests) {\
if(_interrupt_requests & InterruptRequestFlags::Reset) {\
schedule_program(get_reset_program());\
} else if(_interrupt_requests & InterruptRequestFlags::NMI) {\
_interrupt_requests &= ~InterruptRequestFlags::NMI;\
schedule_program(get_nmi_program());\
} else if(_interrupt_requests & InterruptRequestFlags::IRQ) {\
schedule_program(get_irq_program());\
} \
} else {\
schedule_program(fetch_decode_execute);\
}\
@ -602,8 +610,8 @@ template <class T> class Processor {
while (!_ready_is_active && number_of_cycles > 0) {
if(nextBusOperation != BusOperation::None) {
_irq_request_history[0] = _irq_request_history[1];
_irq_request_history[1] = _irq_line_is_enabled && !_interruptFlag;
_interrupt_requests = (_interrupt_requests & ~InterruptRequestFlags::IRQ) | (_irq_request_history ? InterruptRequestFlags::IRQ : 0);
_irq_request_history = _irq_line_is_enabled && !_interruptFlag;
number_of_cycles -= static_cast<T *>(this)->perform_bus_operation(nextBusOperation, busAddress, busValue);
nextBusOperation = BusOperation::None;
}
@ -1171,7 +1179,7 @@ template <class T> class Processor {
*/
inline void set_reset_line(bool active)
{
_reset_line_is_enabled = active;
_interrupt_requests = (_interrupt_requests & ~InterruptRequestFlags::Reset) | (active ? InterruptRequestFlags::Reset : 0);
}
/*!
@ -1181,7 +1189,7 @@ template <class T> class Processor {
*/
inline bool get_reset_line()
{
return _reset_line_is_enabled;
return !!(_interrupt_requests & InterruptRequestFlags::Reset);
}
/*!
@ -1202,7 +1210,7 @@ template <class T> class Processor {
inline void set_nmi_line(bool active)
{
// NMI is edge triggered, not level
_nmi_line_is_enabled |= active;
_interrupt_requests |= (active ? InterruptRequestFlags::NMI : 0);
}
/*!