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internal/vm/{cpu,exec_funcs,opcodes,vm}: rename op -> operation for clarity (I hope), also general refactors

This commit is contained in:
Bradford Lamson-Scribner 2020-05-31 22:50:07 -06:00
parent 1b3f1f5b1f
commit b7a3ec4a6c
4 changed files with 86 additions and 85 deletions
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2
internal/vm/cpu.go
View File

@ -71,7 +71,7 @@ const (
// StackBottom represents the start of the stack
const StackBottom uint16 = 0x0100 // 256
// Mos6502 TODO: docs
// Mos6502 represents the cpu's registers
type Mos6502 struct {
sp byte // register - stack pointer
pc uint16 // register - program counter

128
internal/vm/exec_funcs.go
View File

@ -2,7 +2,7 @@ package vm
// interrupt, N Z C I D V
// push PC+2, push SR - - - 1 - -
func execBRK(a *Appleone, o op) error {
func execBRK(a *Appleone, o operation) error {
// set processer status flag to BRK
a.cpu.ps = flagBreak
@ -17,7 +17,7 @@ func execBRK(a *Appleone, o op) error {
// pull SR, pull PC N Z C I D V
// from stack
func execRTI(a *Appleone, o op) error {
func execRTI(a *Appleone, o operation) error {
a.cpu.ps = a.popStackWord()
a.cpu.pc = a.popStackDWord()
return nil
@ -25,7 +25,7 @@ func execRTI(a *Appleone, o op) error {
// M - 1 -> M N Z C I D V
// + + - - - -
func execDEC(a *Appleone, o op) error {
func execDEC(a *Appleone, o operation) error {
addr, err := a.getAddr(o)
if err != nil {
return err
@ -40,7 +40,7 @@ func execDEC(a *Appleone, o op) error {
// M + 1 -> M N Z C I D V
// + + - - - -
func execINC(a *Appleone, o op) error {
func execINC(a *Appleone, o operation) error {
addr, err := a.getAddr(o)
if err != nil {
return err
@ -55,7 +55,7 @@ func execINC(a *Appleone, o op) error {
// X + 1 -> X N Z C I D V
// + + - - - -
func execINX(a *Appleone, o op) error {
func execINX(a *Appleone, o operation) error {
a.cpu.x++
a.maybeSetFlagZero(a.cpu.x)
a.maybeSetFlagOverflow(a.cpu.x)
@ -64,7 +64,7 @@ func execINX(a *Appleone, o op) error {
// Y + 1 -> Y N Z C I D V
// + + - - - -
func execINY(a *Appleone, o op) error {
func execINY(a *Appleone, o operation) error {
a.cpu.y++
a.maybeSetFlagZero(a.cpu.y)
a.maybeSetFlagOverflow(a.cpu.y)
@ -73,7 +73,7 @@ func execINY(a *Appleone, o op) error {
// A -> X N Z C I D V
// + + - - - -
func execTAX(a *Appleone, o op) error {
func execTAX(a *Appleone, o operation) error {
a.cpu.x = a.cpu.a
a.maybeSetFlagZero(a.cpu.x)
a.maybeSetFlagOverflow(a.cpu.x)
@ -82,7 +82,7 @@ func execTAX(a *Appleone, o op) error {
// A -> Y N Z C I D V
// + + - - - -
func execTAY(a *Appleone, o op) error {
func execTAY(a *Appleone, o operation) error {
a.cpu.y = a.cpu.a
a.maybeSetFlagZero(a.cpu.y)
a.maybeSetFlagOverflow(a.cpu.y)
@ -91,7 +91,7 @@ func execTAY(a *Appleone, o op) error {
// X - 1 -> X N Z C I D V
// + + - - - -
func execDEX(a *Appleone, o op) error {
func execDEX(a *Appleone, o operation) error {
a.cpu.x--
a.maybeSetFlagZero(a.cpu.x)
a.maybeSetFlagOverflow(a.cpu.x)
@ -100,7 +100,7 @@ func execDEX(a *Appleone, o op) error {
// Y - 1 -> Y N Z C I D V
// + + - - - -
func execDEY(a *Appleone, o op) error {
func execDEY(a *Appleone, o operation) error {
a.cpu.y--
a.maybeSetFlagZero(a.cpu.y)
a.maybeSetFlagOverflow(a.cpu.y)
@ -109,7 +109,7 @@ func execDEY(a *Appleone, o op) error {
// M -> A N Z C I D V
// + + - - - -
func execLDA(a *Appleone, o op) error {
func execLDA(a *Appleone, o operation) error {
operand, err := a.getOperand(o)
if err != nil {
return err
@ -122,7 +122,7 @@ func execLDA(a *Appleone, o op) error {
// M -> X N Z C I D V
// + + - - - -
func execLDX(a *Appleone, o op) error {
func execLDX(a *Appleone, o operation) error {
operand, err := a.getOperand(o)
if err != nil {
return err
@ -135,7 +135,7 @@ func execLDX(a *Appleone, o op) error {
// M -> Y N Z C I D V
// + + - - - -
func execLDY(a *Appleone, o op) error {
func execLDY(a *Appleone, o operation) error {
operand, err := a.getOperand(o)
if err != nil {
return err
@ -148,7 +148,7 @@ func execLDY(a *Appleone, o op) error {
// A + M + C -> A, C N Z C I D V
// + + + - - +
func execADC(a *Appleone, o op) error {
func execADC(a *Appleone, o operation) error {
b, err := a.getOperand(o)
if err != nil {
return err
@ -177,7 +177,7 @@ func execADC(a *Appleone, o op) error {
// A - M - C -> A N Z C I D V
// + + + - - +
func execSBC(a *Appleone, o op) error {
func execSBC(a *Appleone, o operation) error {
operand, err := a.getOperand(o)
if err != nil {
return err
@ -211,7 +211,7 @@ func execSBC(a *Appleone, o op) error {
// X -> M N Z C I D V
// - - - - - -
func execSTX(a *Appleone, o op) error {
func execSTX(a *Appleone, o operation) error {
addr, err := a.getAddr(o)
if err != nil {
return err
@ -222,7 +222,7 @@ func execSTX(a *Appleone, o op) error {
// Y -> M N Z C I D V
// - - - - - -
func execSTY(a *Appleone, o op) error {
func execSTY(a *Appleone, o operation) error {
addr, err := a.getAddr(o)
if err != nil {
return err
@ -233,7 +233,7 @@ func execSTY(a *Appleone, o op) error {
// A -> M N Z C I D V
// - - - - - -
func execSTA(a *Appleone, o op) error {
func execSTA(a *Appleone, o operation) error {
addr, err := a.getAddr(o)
if err != nil {
return err
@ -244,7 +244,7 @@ func execSTA(a *Appleone, o op) error {
// branch on Z = 1 N Z C I D V
// - - - - - -
func execBEQ(a *Appleone, o op) error {
func execBEQ(a *Appleone, o operation) error {
if a.getFlag(flagZero) == flagZero {
a.branch(o)
}
@ -253,7 +253,7 @@ func execBEQ(a *Appleone, o op) error {
// branch on Z = 0 N Z C I D V
// - - - - - -
func execBNE(a *Appleone, o op) error {
func execBNE(a *Appleone, o operation) error {
if a.getFlag(flagZero) != flagZero {
a.branch(o)
}
@ -262,7 +262,7 @@ func execBNE(a *Appleone, o op) error {
// branch on V = 0 N Z C I D V
// - - - - - -
func execBVC(a *Appleone, o op) error {
func execBVC(a *Appleone, o operation) error {
if a.getFlag(flagOverflow) == 0 {
a.branch(o)
}
@ -271,7 +271,7 @@ func execBVC(a *Appleone, o op) error {
// branch on V = 1 N Z C I D V
// - - - - - -
func execBVS(a *Appleone, o op) error {
func execBVS(a *Appleone, o operation) error {
if a.getFlag(flagOverflow) != 0 {
a.branch(o)
}
@ -280,7 +280,7 @@ func execBVS(a *Appleone, o op) error {
// bits 7 and 6 of operand are transfered to bit 7 and 6 of SR (N,V);
// the zeroflag is set to the result of operand AND accumulator.
func execBIT(a *Appleone, o op) error {
func execBIT(a *Appleone, o operation) error {
operand, err := a.getOperand(o)
if err != nil {
return err
@ -298,7 +298,7 @@ func execBIT(a *Appleone, o op) error {
// branch on C = 0 N Z C I D V
// - - - - - -
func execBCC(a *Appleone, o op) error {
func execBCC(a *Appleone, o operation) error {
if a.getFlag(flagCarry) == 0 {
a.branch(o)
}
@ -307,7 +307,7 @@ func execBCC(a *Appleone, o op) error {
// branch on N = 1 N Z C I D V
// - - - - - -
func execBMI(a *Appleone, o op) error {
func execBMI(a *Appleone, o operation) error {
if a.getFlag(flagNegative) == flagNegative {
a.branch(o)
}
@ -316,7 +316,7 @@ func execBMI(a *Appleone, o op) error {
// branch on N = 0 N Z C I D V
// - - - - - -
func execBPL(a *Appleone, o op) error {
func execBPL(a *Appleone, o operation) error {
if a.getFlag(flagNegative) == 0 {
a.branch(o)
}
@ -325,7 +325,7 @@ func execBPL(a *Appleone, o op) error {
// branch on C = 1 N Z C I D V
// - - - - - -
func execBCS(a *Appleone, o op) error {
func execBCS(a *Appleone, o operation) error {
if a.getFlag(flagCarry) != 0 {
a.branch(o)
}
@ -334,7 +334,7 @@ func execBCS(a *Appleone, o op) error {
// X - M N Z C I D V
// + + + - - -
func execCPX(a *Appleone, o op) error {
func execCPX(a *Appleone, o operation) error {
operand, err := a.getOperand(o)
if err != nil {
return err
@ -345,7 +345,7 @@ func execCPX(a *Appleone, o op) error {
// A EOR M -> A N Z C I D V
// + + - - - -
func execEOR(a *Appleone, o op) error {
func execEOR(a *Appleone, o operation) error {
operand, err := a.getOperand(o)
if err != nil {
return err
@ -358,7 +358,7 @@ func execEOR(a *Appleone, o op) error {
// A - M N Z C I D V
// + + + - - -
func execCMP(a *Appleone, o op) error {
func execCMP(a *Appleone, o operation) error {
operand, err := a.getOperand(o)
if err != nil {
return err
@ -369,7 +369,7 @@ func execCMP(a *Appleone, o op) error {
// Y - M N Z C I D V
// + + + - - -
func execCPY(a *Appleone, o op) error {
func execCPY(a *Appleone, o operation) error {
operand, err := a.getOperand(o)
if err != nil {
return err
@ -380,62 +380,62 @@ func execCPY(a *Appleone, o op) error {
// 0 -> C N Z C I D V
// - - 0 - - -
func execCLC(a *Appleone, o op) error {
func execCLC(a *Appleone, o operation) error {
a.clearFlag(flagCarry)
return nil
}
// 0 -> D N Z C I D V
// - - - - 0 -
func execCLD(a *Appleone, o op) error {
func execCLD(a *Appleone, o operation) error {
a.clearFlag(flagDecimalMode)
return nil
}
// 0 -> I N Z C I D V
// - - - 0 - -
func execCLI(a *Appleone, o op) error {
func execCLI(a *Appleone, o operation) error {
a.clearFlag(flagDisableInterrupts)
return nil
}
// 0 -> V N Z C I D V
// - - - - - 0
func execCLV(a *Appleone, o op) error {
func execCLV(a *Appleone, o operation) error {
a.clearFlag(flagOverflow)
return nil
}
// 1 -> C N Z C I D V
// - - 1 - - -
func execSEC(a *Appleone, o op) error {
func execSEC(a *Appleone, o operation) error {
a.setFlag(flagCarry)
return nil
}
// 1 -> D N Z C I D V
// - - - - 1 -
func execSED(a *Appleone, o op) error {
func execSED(a *Appleone, o operation) error {
a.setFlag(flagDecimalMode)
return nil
}
// 1 -> I N Z C I D V
// - - - 1 - -
func execSEI(a *Appleone, o op) error {
func execSEI(a *Appleone, o operation) error {
a.setFlag(flagDisableInterrupts)
return nil
}
// --- N Z C I D V
// - - - - - -
func execNOP(a *Appleone, o op) error {
func execNOP(a *Appleone, o operation) error {
return nil
}
// (PC+1) -> PCL N Z C I D V
// (PC+2) -> PCH - - - - - -
func execJMP(a *Appleone, o op) error {
func execJMP(a *Appleone, o operation) error {
if o.addrMode == indirect {
addr, err := a.getAddr(o)
if err != nil {
@ -454,14 +454,14 @@ func execJMP(a *Appleone, o op) error {
// push A N Z C I D V
// - - - - - -
func execPHA(a *Appleone, o op) error {
func execPHA(a *Appleone, o operation) error {
a.pushWordToStack(a.cpu.a)
return nil
}
// X -> A N Z C I D V
// + + - - - -
func execTXA(a *Appleone, o op) error {
func execTXA(a *Appleone, o operation) error {
a.cpu.a = a.cpu.x
a.maybeSetFlagOverflow(a.cpu.a)
a.maybeSetFlagZero(a.cpu.a)
@ -470,7 +470,7 @@ func execTXA(a *Appleone, o op) error {
// Y -> A N Z C I D V
// + + - - - -
func execTYA(a *Appleone, o op) error {
func execTYA(a *Appleone, o operation) error {
a.cpu.a = a.cpu.y
a.maybeSetFlagOverflow(a.cpu.a)
a.maybeSetFlagZero(a.cpu.a)
@ -479,7 +479,7 @@ func execTYA(a *Appleone, o op) error {
// SP -> X N Z C I D V
// + + - - - -
func execTSX(a *Appleone, o op) error {
func execTSX(a *Appleone, o operation) error {
a.cpu.x = a.cpu.sp
a.maybeSetFlagOverflow(a.cpu.x)
a.maybeSetFlagZero(a.cpu.x)
@ -488,7 +488,7 @@ func execTSX(a *Appleone, o op) error {
// pull A N Z C I D V
// + + - - - -
func execPLA(a *Appleone, o op) error {
func execPLA(a *Appleone, o operation) error {
a.cpu.a = a.popStackWord()
a.maybeSetFlagOverflow(a.cpu.a)
a.maybeSetFlagZero(a.cpu.a)
@ -496,7 +496,7 @@ func execPLA(a *Appleone, o op) error {
}
// pull SR from stack N Z C I D V
func execPLP(a *Appleone, o op) error {
func execPLP(a *Appleone, o operation) error {
a.cpu.ps = a.popStackWord() | 0B_00110000
a.maybeSetFlagOverflow(a.cpu.a)
a.maybeSetFlagZero(a.cpu.a)
@ -505,7 +505,7 @@ func execPLP(a *Appleone, o op) error {
// push SR N Z C I D V
// - - - - - -
func execPHP(a *Appleone, o op) error {
func execPHP(a *Appleone, o operation) error {
a.pushWordToStack(a.cpu.ps)
return nil
}
@ -513,7 +513,7 @@ func execPHP(a *Appleone, o op) error {
// push (PC+2), N Z C I D V
// (PC+1) -> PCL - - - - - -
// (PC+2) -> PCH
func execJSR(a *Appleone, o op) error {
func execJSR(a *Appleone, o operation) error {
a.pushDWordToStack(a.cpu.pc - 1)
addr, err := a.getAddr(o)
if err != nil {
@ -525,14 +525,14 @@ func execJSR(a *Appleone, o op) error {
// pull PC, PC+1 -> PC N Z C I D V
// - - - - - -
func execRTS(a *Appleone, o op) error {
func execRTS(a *Appleone, o operation) error {
a.cpu.pc = a.popStackDWord() + 1
return nil
}
// 0 -> [76543210] -> C N Z C I D V
// 0 + + - - -
func execLSR(a *Appleone, o op) error {
func execLSR(a *Appleone, o operation) error {
operand, err := a.getOperand(o)
if err != nil {
return err
@ -555,18 +555,16 @@ func execLSR(a *Appleone, o op) error {
return nil
}
addr, err := a.getAddr(o)
if err != nil {
if err := a.setMem(o, operand); err != nil {
return err
}
a.mem[addr] = operand
return nil
}
// C <- [76543210] <- C N Z C I D V
// + + + - - -
func execROL(a *Appleone, o op) error {
func execROL(a *Appleone, o operation) error {
operand, err := a.getOperand(o)
if err != nil {
return err
@ -597,18 +595,16 @@ func execROL(a *Appleone, o op) error {
return nil
}
addr, err := a.getAddr(o)
if err != nil {
if err := a.setMem(o, operand); err != nil {
return err
}
a.mem[addr] = operand
return nil
}
// X -> SP N Z C I D V
// - - - - - -
func execTXS(a *Appleone, o op) error {
func execTXS(a *Appleone, o operation) error {
a.cpu.sp = a.cpu.x
// TODO: needed?
// a.maybeSetFlagZero(a.cpu.sp)
@ -618,7 +614,7 @@ func execTXS(a *Appleone, o op) error {
// C -> [76543210] -> C N Z C I D V
// + + + - - -
func execROR(a *Appleone, o op) error {
func execROR(a *Appleone, o operation) error {
operand, err := a.getOperand(o)
if err != nil {
return err
@ -649,18 +645,16 @@ func execROR(a *Appleone, o op) error {
return nil
}
addr, err := a.getAddr(o)
if err != nil {
if err := a.setMem(o, operand); err != nil {
return err
}
a.mem[addr] = operand
return nil
}
// C <- [76543210] <- 0 N Z C I D V
// + + + - - -
func execASL(a *Appleone, o op) error {
func execASL(a *Appleone, o operation) error {
operand, err := a.getOperand(o)
if err != nil {
return err
@ -682,18 +676,16 @@ func execASL(a *Appleone, o op) error {
return nil
}
addr, err := a.getAddr(o)
if err != nil {
if err := a.setMem(o, operand); err != nil {
return err
}
a.mem[addr] = operand
return nil
}
// A AND M -> A N Z C I D V
// + + - - - -
func execAND(a *Appleone, o op) error {
func execAND(a *Appleone, o operation) error {
operand, err := a.getOperand(o)
if err != nil {
return err
@ -706,7 +698,7 @@ func execAND(a *Appleone, o op) error {
// A OR M -> A N Z C I D V
// + + - - - -
func execORA(a *Appleone, o op) error {
func execORA(a *Appleone, o operation) error {
operand, err := a.getOperand(o)
if err != nil {
return err

20
internal/vm/opcodes.go
View File

@ -4,18 +4,18 @@ import (
"errors"
)
// op represents an operation. It includes the name of the op, it's 8 bit hexidecimal
// opcode, how many bytes it occupies (it's size), as well as it's addressing mode.
type op struct {
// operation includes the name of the operation, it's 8 bit hexidecimal opcode, how
// many bytes it occupies (it's size), as well as it's addressing mode.
type operation struct {
name string
opcode byte
size byte
addrMode addrMode
exec func(a *Appleone, o op) error
exec func(a *Appleone, op operation) error
}
func newOp(name string, opcode, size byte, addrMode addrMode, exec func(a *Appleone, o op) error) op {
return op{
func newOp(name string, opcode, size byte, addrMode addrMode, exec func(a *Appleone, op operation) error) operation {
return operation{
name: name,
opcode: opcode,
size: size,
@ -24,18 +24,18 @@ func newOp(name string, opcode, size byte, addrMode addrMode, exec func(a *Apple
}
}
// opByCode takes an opcode (a single byte/word) and returns the associated operation
func opByCode(b byte) (op, error) {
// operationByCode takes an opcode (a single byte/word) and returns the associated operation
func operationByCode(b byte) (operation, error) {
o, ok := opcodes[b]
if !ok {
return op{}, errors.New("unknown opcode")
return operation{}, errors.New("unknown opcode")
}
return o, nil
}
// opcodes represent all of the Apple 1 opcodes available. Each 8 bit opcode is mapped to a corresponding
// "op" which is just a struct holding metadata about the operation.
var opcodes = map[byte]op{
var opcodes = map[byte]operation{
// BRK Force Break
// addressing assembler opc bytes cyles
// --------------------------------------------

21
internal/vm/vm.go
View File

@ -26,19 +26,19 @@ func (a *Appleone) load(addr uint16, data []byte) {
}
func (a *Appleone) step() {
op, err := opByCode(a.mem[a.cpu.pc])
operation, err := operationByCode(a.mem[a.cpu.pc])
if err != nil {
fmt.Println("TODO")
}
a.cpu.pc += uint16(op.size)
a.cpu.pc += uint16(operation.size)
if err := op.exec(a, op); err != nil {
if err := operation.exec(a, operation); err != nil {
fmt.Println("TODO")
}
}
func (a *Appleone) getAddr(o op) (uint16, error) {
func (a *Appleone) getAddr(o operation) (uint16, error) {
switch o.addrMode {
// TODO: will these ever apply here?
// case accumulator:
@ -75,7 +75,7 @@ func (a *Appleone) getAddr(o op) (uint16, error) {
}
}
func (a *Appleone) getOperand(o op) (byte, error) {
func (a *Appleone) getOperand(o operation) (byte, error) {
if o.addrMode == accumulator {
return a.cpu.a, nil
}
@ -156,7 +156,7 @@ func (a *Appleone) maybeSetFlagOverflow(word byte) {
// Branch offsets are signed 8-bit values, -128 ... +127, negative offsets in two's
// complement. Page transitions may occur and add an extra cycle to the exucution
func (a *Appleone) branch(o op) error {
func (a *Appleone) branch(o operation) error {
offset, err := a.getOperand(o)
if err != nil {
return err
@ -187,3 +187,12 @@ func (a *Appleone) compare(b1, b2 byte) {
b := byte(uint16(b1) - uint16(b2))
a.maybeSetFlagOverflow(b)
}
func (a *Appleone) setMem(o operation, operand byte) error {
addr, err := a.getAddr(o)
if err != nil {
return err
}
a.mem[addr] = operand
return nil
}