Much faster resolution avoiding a single getSet with callbacks.

core6502/addressing.go

@@ -29,46 +29,44 @@ func getWordInLine(line []uint8) uint16 {
 }
 
 func resolveValue(s *State, line []uint8, opcode opcode) uint8 {
-	getValue, _, _ := resolve(s, line, opcode)
-	return getValue()
+	switch opcode.addressMode {
+	case modeAccumulator:
+		return s.reg.getA()
+	case modeImplicitX:
+		return s.reg.getX()
+	case modeImplicitY:
+		return s.reg.getY()
+	case modeImmediate:
+		return line[1]
+	}
+
+	// The value is in memory
+	address := resolveAddress(s, line, opcode)
+	return s.mem.Peek(address)
 }
 
-func resolveGetSetValue(s *State, line []uint8, opcode opcode) (value uint8, setValue func(uint8)) {
-	getValue, setValue, _ := resolve(s, line, opcode)
-	value = getValue()
-	return
-}
+func resolveSetValue(s *State, line []uint8, opcode opcode, value uint8) {
+	switch opcode.addressMode {
+	case modeAccumulator:
+		s.reg.setA(value)
+		return
+	case modeImplicitX:
+		s.reg.setX(value)
+		return
+	case modeImplicitY:
+		s.reg.setY(value)
+		return
+	}
 
-func resolveSetValue(s *State, line []uint8, opcode opcode) func(uint8) {
-	_, setValue, _ := resolve(s, line, opcode)
-	return setValue
+	// The value is in memory
+	address := resolveAddress(s, line, opcode)
+	s.mem.Poke(address, value)
 }
 
 func resolveAddress(s *State, line []uint8, opcode opcode) uint16 {
-	_, _, address := resolve(s, line, opcode)
-	return address
-}
-
-func resolve(s *State, line []uint8, opcode opcode) (getValue func() uint8, setValue func(uint8), address uint16) {
-	hasAddress := true
-	register := regNone
+	var address uint16
 
 	switch opcode.addressMode {
-	case modeAccumulator:
-		getValue = func() uint8 { return s.reg.getA() }
-		hasAddress = false
-		register = regA
-	case modeImplicitX:
-		getValue = func() uint8 { return s.reg.getX() }
-		hasAddress = false
-		register = regX
-	case modeImplicitY:
-		getValue = func() uint8 { return s.reg.getY() }
-		hasAddress = false
-		register = regY
-	case modeImmediate:
-		getValue = func() uint8 { return line[1] }
-		hasAddress = false
 	case modeZeroPage:
 		address = uint16(line[1])
 	case modeZeroPageX:
@@ -103,25 +101,10 @@ func resolve(s *State, line []uint8, opcode opcode) (getValue func() uint8, setV
 		// Two addressing modes combined. We refer to the second one, relative,
 		// placed one byte after the zeropage reference
 		address = s.reg.getPC() + uint16(int8(line[2])) // Note: line[2] is signed
-
 	default:
 		panic("Assert failed. Missing addressing mode")
 	}
-
-	if hasAddress {
-		getValue = func() uint8 { return s.mem.Peek(address) }
-	}
-
-	setValue = func(value uint8) {
-		if hasAddress {
-			s.mem.Poke(address, value)
-		} else if register != regNone {
-			s.reg.setRegister(register, value)
-		} else {
-			panic("Assert failed. Should never happen")
-		}
-	}
-	return
+	return address
 }
 
 func lineString(line []uint8, opcode opcode) string {

core6502/operations.go

@@ -12,20 +12,20 @@ func buildOpTransfer(regSrc int, regDst int) opFunc {
 
 func buildOpIncDec(inc bool) opFunc {
 	return func(s *State, line []uint8, opcode opcode) {
-		value, setValue := resolveGetSetValue(s, line, opcode)
+		value := resolveValue(s, line, opcode)
 		if inc {
 			value++
 		} else {
 			value--
 		}
 		s.reg.updateFlagZN(value)
-		setValue(value)
+		resolveSetValue(s, line, opcode, value)
 	}
 }
 
 func buildOpShift(isLeft bool, isRotate bool) opFunc {
 	return func(s *State, line []uint8, opcode opcode) {
-		value, setValue := resolveGetSetValue(s, line, opcode)
+		value := resolveValue(s, line, opcode)
 
 		oldCarry := s.reg.getFlagBit(flagC)
 		var carry bool
@@ -44,7 +44,7 @@ func buildOpShift(isLeft bool, isRotate bool) opFunc {
 		}
 		s.reg.updateFlag(flagC, carry)
 		s.reg.updateFlagZN(value)
-		setValue(value)
+		resolveSetValue(s, line, opcode, value)
 	}
 }
 
@@ -58,9 +58,8 @@ func buildOpLoad(regDst int) opFunc {
 
 func buildOpStore(regSrc int) opFunc {
 	return func(s *State, line []uint8, opcode opcode) {
-		setValue := resolveSetValue(s, line, opcode)
 		value := s.reg.getRegister(regSrc)
-		setValue(value)
+		resolveSetValue(s, line, opcode, value)
 	}
 }
 
@@ -96,12 +95,13 @@ func buildOpBranchOnBit(bit uint8, test bool) opFunc {
 
 func buildOpSetBit(bit uint8, set bool) opFunc {
 	return func(s *State, line []uint8, opcode opcode) {
-		value, setValue := resolveGetSetValue(s, line, opcode)
+		value := resolveValue(s, line, opcode)
 		if set {
-			setValue(value | (1 << bit))
+			value = value | (1 << bit)
 		} else {
-			setValue(value &^ (1 << bit))
+			value = value &^ (1 << bit)
 		}
+		resolveSetValue(s, line, opcode, value)
 	}
 }
 
@@ -117,17 +117,17 @@ func opBIT(s *State, line []uint8, opcode opcode) {
 }
 
 func opTRB(s *State, line []uint8, opcode opcode) {
-	value, setValue := resolveGetSetValue(s, line, opcode)
+	value := resolveValue(s, line, opcode)
 	a := s.reg.getA()
 	s.reg.updateFlag(flagZ, (value&a) == 0)
-	setValue(value &^ a)
+	resolveSetValue(s, line, opcode, value&^a)
 }
 
 func opTSB(s *State, line []uint8, opcode opcode) {
-	value, setValue := resolveGetSetValue(s, line, opcode)
+	value := resolveValue(s, line, opcode)
 	a := s.reg.getA()
 	s.reg.updateFlag(flagZ, (value&a) == 0)
-	setValue(value | a)
+	resolveSetValue(s, line, opcode, value|a)
 }
 
 func buildOpCompare(reg int) opFunc {
@@ -305,6 +305,5 @@ func opBRKAlt(s *State, line []uint8, opcode opcode) {
 }
 
 func opSTZ(s *State, line []uint8, opcode opcode) {
-	setValue := resolveSetValue(s, line, opcode)
-	setValue(0)
+	resolveSetValue(s, line, opcode, 0)
 }