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Small efficiency boost in CPU by eliminating excess reads for addressing modes that do not require it (namely, Relative and Implied modes). This also improves quality of inspection metrics since extra reads were causing some memory to be mis-categorized.

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This commit is contained in:
Brendan Robert 2015-09-05 12:26:03 -05:00
parent 8942d6462e
commit baa79b26c2
1 changed files with 17 additions and 8 deletions
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25
src/main/java/jace/apple2e/MOS65C02.java
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@ -319,10 +319,11 @@ public class MOS65C02 extends CPU {
} }
int address = 0; int address = 0;
int value = 0; int value = 0;
boolean shouldFetch;
private void fetch(MOS65C02 cpu) { private void fetch(MOS65C02 cpu) {
address = getMode().calculator.calculateAddress(cpu); address = getMode().calculator.calculateAddress(cpu);
value = getMode().calculator.getValue(!command.isStoreOnly(), cpu); value = shouldFetch ? getMode().calculator.getValue(!command.isStoreOnly(), cpu) : 0;
} }
public void execute(MOS65C02 cpu) { public void execute(MOS65C02 cpu) {
@ -330,15 +331,20 @@ public class MOS65C02 extends CPU {
} }
private OPCODE(int val, COMMAND c, MODE m, int wait) { private OPCODE(int val, COMMAND c, MODE m, int wait) {
this(val, c, m, wait, false); this(val, c, m, wait, m.fetchValue, false);
} }
private OPCODE(int val, COMMAND c, MODE m, int wait, boolean extended) { private OPCODE(int val, COMMAND c, MODE m, int wait, boolean extended) {
this(val, c, m, wait, m.fetchValue, extended);
}
private OPCODE(int val, COMMAND c, MODE m, int wait, boolean fetch, boolean extended) {
code = val; code = val;
waitCycles = wait - 1; waitCycles = wait - 1;
command = c; command = c;
addressingMode = m; addressingMode = m;
isExtendedOpcode = extended; isExtendedOpcode = extended;
shouldFetch = fetch;
} }
} }
@ -346,15 +352,15 @@ public class MOS65C02 extends CPU {
abstract int calculateAddress(MOS65C02 cpu); abstract int calculateAddress(MOS65C02 cpu);
default int getValue(boolean isRead, MOS65C02 cpu) { default int getValue(boolean generateEvent, MOS65C02 cpu) {
int address = calculateAddress(cpu); int address = calculateAddress(cpu);
return (address > -1) ? (0x0ff & cpu.getMemory().read(address, TYPE.READ_DATA, isRead, false)) : 0; return (address > -1) ? (0x0ff & cpu.getMemory().read(address, TYPE.READ_DATA, generateEvent, false)) : 0;
} }
} }
public enum MODE { public enum MODE {
IMPLIED(1, "", (cpu) -> -1), IMPLIED(1, "", (cpu) -> -1, false),
// RELATIVE(2, "#$~1 ($R)"), // RELATIVE(2, "#$~1 ($R)"),
RELATIVE(2, "$R", (cpu) -> { RELATIVE(2, "$R", (cpu) -> {
int pc = cpu.getProgramCounter(); int pc = cpu.getProgramCounter();
@ -362,7 +368,7 @@ public class MOS65C02 extends CPU {
// The wait cycles are not added unless the branch actually happens! // The wait cycles are not added unless the branch actually happens!
cpu.setPageBoundaryPenalty((address & 0x00ff00) != (pc & 0x00ff00)); cpu.setPageBoundaryPenalty((address & 0x00ff00) != (pc & 0x00ff00));
return address; return address;
}), }, false),
IMMEDIATE(2, "#$~1", (cpu) -> cpu.getProgramCounter() + 1), IMMEDIATE(2, "#$~1", (cpu) -> cpu.getProgramCounter() + 1),
ZEROPAGE(2, "$~1", (cpu) -> cpu.getMemory().read(cpu.getProgramCounter() + 1, TYPE.READ_OPERAND, cpu.readAddressTriggersEvent, false) & 0x00FF), ZEROPAGE(2, "$~1", (cpu) -> cpu.getMemory().read(cpu.getProgramCounter() + 1, TYPE.READ_OPERAND, cpu.readAddressTriggersEvent, false) & 0x00FF),
ZEROPAGE_X(2, "$~1,X", (cpu) -> 0x0FF & (cpu.getMemory().read(cpu.getProgramCounter() + 1, TYPE.READ_OPERAND, cpu.readAddressTriggersEvent, false) + cpu.X)), ZEROPAGE_X(2, "$~1,X", (cpu) -> 0x0FF & (cpu.getMemory().read(cpu.getProgramCounter() + 1, TYPE.READ_OPERAND, cpu.readAddressTriggersEvent, false) + cpu.X)),
@ -452,8 +458,13 @@ public class MOS65C02 extends CPU {
boolean twoByte = false; boolean twoByte = false;
boolean relative = false; boolean relative = false;
boolean implied = true; boolean implied = true;
boolean fetchValue = true;
private MODE(int size, String fmt, AddressCalculator calc) { private MODE(int size, String fmt, AddressCalculator calc) {
this(size, fmt, calc, true);
}
private MODE(int size, String fmt, AddressCalculator calc, boolean fetch) {
this.fetchValue = fetch;
this.size = size; this.size = size;
if (fmt.contains("~")) { if (fmt.contains("~")) {
this.f1 = fmt.substring(0, fmt.indexOf('~')); this.f1 = fmt.substring(0, fmt.indexOf('~'));
@ -1122,13 +1133,11 @@ public class MOS65C02 extends CPU {
public void push(byte val) { public void push(byte val) {
getMemory().write(0x0100 + STACK, val, true, false); getMemory().write(0x0100 + STACK, val, true, false);
STACK = (STACK - 1) & 0x0FF; STACK = (STACK - 1) & 0x0FF;
//System.out.println("--> PUSH "+Integer.toString(0x0FF & val, 16));
} }
public byte pop() { public byte pop() {
STACK = (STACK + 1) & 0x0FF; STACK = (STACK + 1) & 0x0FF;
byte val = getMemory().read(0x0100 + STACK, TYPE.READ_DATA, true, false); byte val = getMemory().read(0x0100 + STACK, TYPE.READ_DATA, true, false);
//System.out.println("<-- POP "+Integer.toString(0x0FF & val, 16));
return val; return val;
} }