307 lines
8.4 KiB
Go
307 lines
8.4 KiB
Go
package commands
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import (
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"fmt"
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"strings"
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"c65gm/internal/compiler"
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"c65gm/internal/preproc"
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"c65gm/internal/utils"
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)
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// PeekWCommand handles PEEKW statements (reads a word/2 bytes)
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// Syntax:
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//
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// PEEKW <address>[offset] GIVING|-> <dest> # old syntax
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// <dest> = PEEKW <address>[offset] # new syntax
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//
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// Where address is:
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// - Byte variable (zero-page indexed addressing)
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// - Word variable (self-modifying code or ZP pointer with offset)
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// - Expression (direct addressing)
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//
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// Destination must be a word variable
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type PeekWCommand struct {
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addrVarName string
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addrVarKind compiler.VarKind
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addrValue uint16
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isAddrVar bool
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isZPPointer bool
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offsetVarName string
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offsetValue uint8
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hasOffset bool
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isOffsetVar bool
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destVarName string
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pragmaSet preproc.PragmaSet
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}
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func (c *PeekWCommand) WillHandle(line preproc.Line) bool {
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params, err := utils.ParseParams(line.Text)
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if err != nil || len(params) != 4 {
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return false
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}
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// Old syntax: PEEKW ... (4 params)
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if strings.ToUpper(params[0]) == "PEEKW" {
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return true
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}
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// New syntax: <dest> = PEEKW <address>
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if params[1] == "=" && strings.ToUpper(params[2]) == "PEEKW" {
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return true
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}
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return false
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}
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func (c *PeekWCommand) Interpret(line preproc.Line, ctx *compiler.CompilerContext) error {
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// Clear state
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c.addrVarName = ""
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c.addrValue = 0
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c.isAddrVar = false
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c.isZPPointer = false
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c.offsetVarName = ""
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c.offsetValue = 0
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c.hasOffset = false
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c.isOffsetVar = false
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c.destVarName = ""
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// Store pragma set for Generate phase
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c.pragmaSet = ctx.Pragma.GetPragmaSetByIndex(line.PragmaSetIndex)
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params, err := utils.ParseParams(line.Text)
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if err != nil {
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return err
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}
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if len(params) != 4 {
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return fmt.Errorf("PEEKW: expected 4 parameters, got %d", len(params))
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}
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scope := ctx.CurrentScope()
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var addrParam string
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var destParam string
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// Determine syntax and parse accordingly
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if strings.ToUpper(params[0]) == "PEEKW" {
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// Old syntax: PEEKW <address> GIVING|-> <dest>
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// Validate separator (param 3)
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sep := strings.ToUpper(params[2])
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if sep != "GIVING" && sep != "->" {
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return fmt.Errorf("PEEKW: parameter #3 must be 'GIVING' or '->', got %q", params[2])
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}
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addrParam = params[1]
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destParam = params[3]
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} else {
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// New syntax: <dest> = PEEKW <address>
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if params[1] != "=" {
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return fmt.Errorf("PEEKW: expected '=' at position 2, got %q", params[1])
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}
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if strings.ToUpper(params[2]) != "PEEKW" {
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return fmt.Errorf("PEEKW: expected 'PEEKW' at position 3, got %q", params[2])
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}
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destParam = params[0]
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addrParam = params[3]
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}
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// Parse address - may have [offset]
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baseAddr, offsetParam := parseOffsetW(addrParam)
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constLookup := func(name string) (int64, bool) {
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sym := ctx.SymbolTable.Lookup(name, scope)
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if sym != nil && sym.IsConst() {
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return int64(sym.Value), true
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}
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return 0, false
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}
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// Try to parse base address
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varName, varKind, value, isVar, err := compiler.ParseOperandParam(
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baseAddr, ctx.SymbolTable, scope, constLookup)
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if err != nil {
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return fmt.Errorf("PEEKW: invalid address: %w", err)
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}
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if isVar {
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// It's a variable
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c.addrVarName = varName
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c.addrVarKind = varKind
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c.isAddrVar = true
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// Check if it's a ZP pointer
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addrSym := ctx.SymbolTable.Lookup(baseAddr, scope)
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if addrSym != nil {
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c.isZPPointer = addrSym.IsZeroPagePointer()
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}
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} else {
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// It's an expression/constant
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c.addrValue = value
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c.isAddrVar = false
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}
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// Parse offset if present
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if offsetParam != "" {
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// Offset only allowed with ZP pointers
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if !c.isZPPointer {
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return fmt.Errorf("PEEKW: offset [%s] only allowed with zero-page word pointer", offsetParam)
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}
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c.hasOffset = true
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// Try to parse offset as variable or expression
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offsetVarName, _, offsetValue, isOffsetVar, err := compiler.ParseOperandParam(
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offsetParam, ctx.SymbolTable, scope, constLookup)
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if err != nil {
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return fmt.Errorf("PEEKW: invalid offset: %w", err)
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}
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if isOffsetVar {
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// Check it's a byte variable
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offsetSym := ctx.SymbolTable.Lookup(offsetParam, scope)
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if offsetSym != nil && !offsetSym.IsByte() {
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return fmt.Errorf("PEEKW: offset variable %q must be byte type", offsetParam)
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}
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c.offsetVarName = offsetVarName
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c.isOffsetVar = true
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} else {
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// Numeric offset - must fit in byte
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if offsetValue > 255 {
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return fmt.Errorf("PEEKW: offset value %d out of byte range", offsetValue)
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}
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c.offsetValue = uint8(offsetValue)
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c.isOffsetVar = false
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}
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}
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// Parse destination variable
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destSym := ctx.SymbolTable.Lookup(destParam, scope)
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if destSym == nil {
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return fmt.Errorf("PEEKW: unknown destination variable %q", destParam)
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}
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if destSym.IsConst() {
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return fmt.Errorf("PEEKW: cannot PEEKW into constant %q", destParam)
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}
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if !destSym.IsWord() {
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return fmt.Errorf("PEEKW: destination %q must be word type", destParam)
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}
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c.destVarName = destSym.FullName()
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// Check for self-referential PEEKW (reading through a pointer into itself)
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if c.isZPPointer && c.addrVarName == c.destVarName {
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return fmt.Errorf("PEEKW: cannot read through pointer %q into itself (would corrupt pointer during read)", c.destVarName)
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}
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return nil
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}
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func (c *PeekWCommand) Generate(ctx *compiler.CompilerContext) ([]string, error) {
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var asm []string
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// Case 1: ZP pointer with offset
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if c.isZPPointer {
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// Load offset into Y
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if c.hasOffset {
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if c.isOffsetVar {
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asm = append(asm, fmt.Sprintf("\tldy %s", c.offsetVarName))
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} else {
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asm = append(asm, fmt.Sprintf("\tldy #%d", c.offsetValue))
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}
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} else {
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asm = append(asm, "\tldy #0")
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}
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// Indexed indirect load - low byte
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asm = append(asm, fmt.Sprintf("\tlda (%s),y", c.addrVarName))
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asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
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// Increment Y and load high byte
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asm = append(asm, "\tiny")
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asm = append(asm, fmt.Sprintf("\tlda (%s),y", c.addrVarName))
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asm = append(asm, fmt.Sprintf("\tsta %s+1", c.destVarName))
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return asm, nil
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}
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// Case 2: Byte variable (zero-page indexed addressing)
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if c.isAddrVar && c.addrVarKind == compiler.KindByte {
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asm = append(asm, fmt.Sprintf("\tldx %s", c.addrVarName))
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asm = append(asm, "\tlda $00,x")
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asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
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asm = append(asm, "\tinx")
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asm = append(asm, "\tlda $00,x")
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asm = append(asm, fmt.Sprintf("\tsta %s+1", c.destVarName))
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return asm, nil
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}
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// Case 3: Word variable (self-modifying code)
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if c.isAddrVar && c.addrVarKind == compiler.KindWord {
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// Check for immutable code pragma
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if c.pragmaSet.GetPragma("_P_USE_IMMUTABLE_CODE") != "" {
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return nil, fmt.Errorf("PEEKW: USE_IMMUTABLE_CODE pragma set but construct requires self-modifying code (consider using zero page word for address)")
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}
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label1 := ctx.GeneralStack.Push()
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label2 := ctx.GeneralStack.Push()
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// Setup both labels with base address
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asm = append(asm, fmt.Sprintf("\tlda %s", c.addrVarName))
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asm = append(asm, fmt.Sprintf("\tsta %s+1", label1))
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asm = append(asm, fmt.Sprintf("\tsta %s+1", label2))
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asm = append(asm, fmt.Sprintf("\tlda %s+1", c.addrVarName))
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asm = append(asm, fmt.Sprintf("\tsta %s+2", label1))
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asm = append(asm, fmt.Sprintf("\tsta %s+2", label2))
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// Read low byte
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asm = append(asm, label1)
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asm = append(asm, "\tlda $ffff")
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asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
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// Increment address in label2
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asm = append(asm, fmt.Sprintf("\tinc %s+1", label2))
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asm = append(asm, fmt.Sprintf("\tbne %s", label2))
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asm = append(asm, fmt.Sprintf("\tinc %s+2", label2))
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// Read high byte
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asm = append(asm, label2)
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asm = append(asm, "\tlda $ffff")
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asm = append(asm, fmt.Sprintf("\tsta %s+1", c.destVarName))
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return asm, nil
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}
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// Case 4: Expression/constant address (direct addressing)
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asm = append(asm, fmt.Sprintf("\tlda %d", c.addrValue))
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asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
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asm = append(asm, fmt.Sprintf("\tlda %d", c.addrValue+1))
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asm = append(asm, fmt.Sprintf("\tsta %s+1", c.destVarName))
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return asm, nil
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}
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// parseOffsetW extracts offset from syntax like "var[offset]"
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// Returns (base, offset) where offset is empty if no brackets found
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func parseOffsetW(param string) (base string, offset string) {
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openBracket := strings.IndexByte(param, '[')
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closeBracket := strings.IndexByte(param, ']')
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if openBracket == -1 || closeBracket == -1 {
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return param, ""
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}
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if closeBracket <= openBracket || closeBracket != len(param)-1 {
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return param, ""
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}
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base = param[:openBracket]
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offset = param[openBracket+1 : closeBracket]
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return base, offset
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}
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