From b7a3ec4a6c284bc6db8899dc3a2dfcac7c230e00 Mon Sep 17 00:00:00 2001 From: Bradford Lamson-Scribner Date: Sun, 31 May 2020 22:50:07 -0600 Subject: [PATCH] internal/vm/{cpu,exec_funcs,opcodes,vm}: rename op -> operation for clarity (I hope), also general refactors --- internal/vm/cpu.go | 2 +- internal/vm/exec_funcs.go | 128 ++++++++++++++++++-------------------- internal/vm/opcodes.go | 20 +++--- internal/vm/vm.go | 21 +++++-- 4 files changed, 86 insertions(+), 85 deletions(-) diff --git a/internal/vm/cpu.go b/internal/vm/cpu.go index 32bcdd3..f303bd7 100644 --- a/internal/vm/cpu.go +++ b/internal/vm/cpu.go @@ -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 diff --git a/internal/vm/exec_funcs.go b/internal/vm/exec_funcs.go index d395e50..1735374 100644 --- a/internal/vm/exec_funcs.go +++ b/internal/vm/exec_funcs.go @@ -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 diff --git a/internal/vm/opcodes.go b/internal/vm/opcodes.go index 5f2403f..c2f74f8 100644 --- a/internal/vm/opcodes.go +++ b/internal/vm/opcodes.go @@ -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 // -------------------------------------------- diff --git a/internal/vm/vm.go b/internal/vm/vm.go index 0d993a9..fc808d7 100644 --- a/internal/vm/vm.go +++ b/internal/vm/vm.go @@ -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 +}