internal/compiler/compiler.go

@@ -317,6 +317,7 @@ func (c *Compiler) getOptimizerConfig() *optimizer.Config {
 	if !cfg.Any() {
 		return nil
 	}
+	cfg.BuildIOMap(c.ctx.Pragma)
 	return cfg
 }
 

internal/optimizer/config.go

@@ -1,31 +1,72 @@
 package optimizer
 
 import (
+	"strconv"
+	"strings"
+
 	"c65gm/internal/preproc"
 )
 
 type Config struct {
-	EnableLoad  bool
-	EnableImm   bool
-	EnableJmp   bool
-	EnableSelf  bool
-	Debug       bool
-	ShowMarkers bool
+	EnableLoad      bool
+	EnableImm       bool
+	EnableJmp       bool
+	EnableSelf      bool
+	EnableStoreLoad bool
+	Debug           bool
+	ShowMarkers     bool
+	IOMap           [65536]bool
 }
 
 func NewConfig(ps preproc.PragmaSet) *Config {
 	all := ps.GetPragma("_P_OPT_ALL") != "" && ps.GetPragma("_P_OPT_ALL") != "0"
 
 	return &Config{
-		EnableLoad:  all || (ps.GetPragma("_P_OPT_LOAD") != "" && ps.GetPragma("_P_OPT_LOAD") != "0"),
-		EnableImm:   all || (ps.GetPragma("_P_OPT_IMM") != "" && ps.GetPragma("_P_OPT_IMM") != "0"),
-		EnableJmp:   all || (ps.GetPragma("_P_OPT_JMP") != "" && ps.GetPragma("_P_OPT_JMP") != "0"),
-		EnableSelf:  all || (ps.GetPragma("_P_OPT_SELF") != "" && ps.GetPragma("_P_OPT_SELF") != "0"),
-		Debug:       (ps.GetPragma("_P_OPT_DEBUG") != "" && ps.GetPragma("_P_OPT_DEBUG") != "0"),
-		ShowMarkers: (ps.GetPragma("_P_OPT_MARKERS") != "" && ps.GetPragma("_P_OPT_MARKERS") != "0"),
+		EnableLoad:      all || (ps.GetPragma("_P_OPT_LOAD") != "" && ps.GetPragma("_P_OPT_LOAD") != "0"),
+		EnableImm:       all || (ps.GetPragma("_P_OPT_IMM") != "" && ps.GetPragma("_P_OPT_IMM") != "0"),
+		EnableJmp:       all || (ps.GetPragma("_P_OPT_JMP") != "" && ps.GetPragma("_P_OPT_JMP") != "0"),
+		EnableSelf:      all || (ps.GetPragma("_P_OPT_SELF") != "" && ps.GetPragma("_P_OPT_SELF") != "0"),
+		EnableStoreLoad: all || (ps.GetPragma("_P_OPT_STLD") != "" && ps.GetPragma("_P_OPT_STLD") != "0"),
+		Debug:           (ps.GetPragma("_P_OPT_DEBUG") != "" && ps.GetPragma("_P_OPT_DEBUG") != "0"),
+		ShowMarkers:     (ps.GetPragma("_P_OPT_MARKERS") != "" && ps.GetPragma("_P_OPT_MARKERS") != "0"),
 	}
 }
 
 func (c *Config) Any() bool {
-	return c.EnableLoad || c.EnableImm || c.EnableJmp || c.EnableSelf
+	return c.EnableLoad || c.EnableImm || c.EnableJmp || c.EnableSelf || c.EnableStoreLoad
+}
+
+// BuildIOMap scans all pragma sets for _P_OPT_IO and marks I/O regions.
+func (c *Config) BuildIOMap(pragma *preproc.Pragma) {
+	for i := 0; i <= pragma.GetCurrentPragmaSetIndex(); i++ {
+		val := pragma.GetPragmaSetByIndex(i).GetPragma("_P_OPT_IO")
+		if val == "" {
+			continue
+		}
+		parts := strings.Fields(val)
+		if len(parts) >= 2 {
+			start := parsePragmaAddr(parts[0])
+			end := parsePragmaAddr(parts[1])
+			if start >= 0 && end >= 0 && start <= end && start < 65536 {
+				for a := start; a <= end && a < 65536; a++ {
+					c.IOMap[a] = true
+				}
+			}
+		}
+	}
+}
+
+func parsePragmaAddr(s string) int {
+	if strings.HasPrefix(s, "$") {
+		v, err := strconv.ParseUint(s[1:], 16, 16)
+		if err != nil {
+			return -1
+		}
+		return int(v)
+	}
+	v, err := strconv.ParseUint(s, 10, 16)
+	if err != nil {
+		return -1
+	}
+	return int(v)
 }

internal/optimizer/optimizer.go

@@ -11,6 +11,9 @@ func Optimize(lines []string, cfg *Config) []string {
 	parsed := parseLines(lines)
 	original := parsed
 
+	if cfg.EnableStoreLoad {
+		parsed = passStoreReload(parsed, cfg)
+	}
 	if cfg.EnableLoad {
 		parsed = passLoadElimination(parsed)
 	}

internal/optimizer/optimizer_test.go

@@ -250,3 +250,152 @@ func containsSubstring(lines []string, sub string) bool {
 	}
 	return false
 }
+
+func TestPassStoreReload(t *testing.T) {
+	cfg := &Config{}
+
+	tests := []struct {
+		name     string
+		input    []string
+		expected int
+	}{
+		{
+			name:     "sta x then lda x",
+			input:    lines("\tsta x", "\tlda x"),
+			expected: 1,
+		},
+		{
+			name:     "different variables",
+			input:    lines("\tsta x", "\tlda y"),
+			expected: 2,
+		},
+		{
+			name:     "ldy between sta and lda",
+			input:    lines("\tsta x", "\tldy #0", "\tlda x"),
+			expected: 2,
+		},
+		{
+			name:     "adc between — modifies A",
+			input:    lines("\tsta x", "\tadc #1", "\tlda x"),
+			expected: 3,
+		},
+		{
+			name:     "label between — barrier",
+			input:    lines("\tsta x", "label", "\tlda x"),
+			expected: 3,
+		},
+		{
+			name:     "different registers",
+			input:    lines("\tsta x", "\tldx x"),
+			expected: 2,
+		},
+		{
+			name:     "comment between",
+			input:    lines("\tsta x", "; source line", "\tlda x"),
+			expected: 2,
+		},
+		{
+			name:     "comment and ldy between",
+			input:    lines("\tsta x", "; POKE addr", "\tldy #5", "\tlda x"),
+			expected: 3,
+		},
+		{
+			name:     "SM code — operand with +",
+			input:    lines("\tsta _L1+1", "\tlda _L1+1"),
+			expected: 2,
+		},
+		{
+			name:     "indexed store — operand with (",
+			input:    lines("\tsta (zp),y", "\tlda (zp),y"),
+			expected: 2,
+		},
+		{
+			name:     "indexed store — operand with ,",
+			input:    lines("\tsta $D020,x", "\tlda $D020,x"),
+			expected: 2,
+		},
+		{
+			name:     "different operand offsets",
+			input:    lines("\tsta x", "\tlda x+1"),
+			expected: 2,
+		},
+		{
+			name:     "inx between — does not modify A",
+			input:    lines("\tsta x", "\tinx", "\tlda x"),
+			expected: 2,
+		},
+		{
+			name:     "dex between — does not modify A",
+			input:    lines("\tsta x", "\tdex", "\tlda x"),
+			expected: 2,
+		},
+		{
+			name:     "iny between — does not modify A",
+			input:    lines("\tsta x", "\tiny", "\tlda x"),
+			expected: 2,
+		},
+		{
+			name:     "dey between — does not modify A",
+			input:    lines("\tsta x", "\tdey", "\tlda x"),
+			expected: 2,
+		},
+		{
+			name:     "tax between — does not modify A",
+			input:    lines("\tsta x", "\ttax", "\tlda x"),
+			expected: 2,
+		},
+		{
+			name:     "tay between — does not modify A",
+			input:    lines("\tsta x", "\ttay", "\tlda x"),
+			expected: 2,
+		},
+		{
+			name:     "txa between — modifies A, keep lda",
+			input:    lines("\tsta x", "\ttxa", "\tlda x"),
+			expected: 3,
+		},
+		{
+			name:     "tya between — modifies A, keep lda",
+			input:    lines("\tsta x", "\ttya", "\tlda x"),
+			expected: 3,
+		},
+		{
+			name:     "pla between — modifies A, keep lda",
+			input:    lines("\tsta x", "\tpla", "\tlda x"),
+			expected: 3,
+		},
+		{
+			name:     "multiple stores — pick the last sta",
+			input:    lines("\tsta x", "\tsta y", "\tlda x"),
+			expected: 2, // sta x kept, sta y kept, lda x removed
+		},
+		{
+			name:     "@@OPT marker between — skip, lda removed",
+			input:    lines("\tsta x", "; @@OPT:LINEAR:LET", "\tlda x"),
+			expected: 1, // @@OPT stripped by stripOptMarkers
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			parsed := parseLines(tt.input)
+			result := passStoreReload(parsed, cfg)
+			cleaned := stripOptMarkers(result)
+			if got := len(cleaned); got != tt.expected {
+				t.Errorf("got %d lines, want %d\ninput: %v\noutput: %v", got, tt.expected, tt.input, linesToString(cleaned))
+			}
+		})
+	}
+}
+
+func TestPassStoreReloadIO(t *testing.T) {
+	cfg := &Config{}
+	cfg.IOMap[0xD020] = true
+
+	parsed := parseLines(lines("\tsta $D020", "\tlda $D020"))
+	result := passStoreReload(parsed, cfg)
+	cleaned := stripOptMarkers(result)
+	if len(cleaned) != 2 {
+		t.Errorf("expected 2 lines (I/O skip), got %d", len(cleaned))
+	}
+}

internal/optimizer/pass_stld.go

@@ -0,0 +1,91 @@
+package optimizer
+
+import "strings"
+
+// passStoreReload removes redundant reloads immediately after stores.
+// Pattern: sta X; ...(non-A-modifying)...; lda X  → remove lda
+func passStoreReload(lines []asmLine, cfg *Config) []asmLine {
+	var result []asmLine
+
+	for i := 0; i < len(lines); i++ {
+		line := lines[i]
+
+		if line.isCode && line.opcode == "sta" && isSafeStldOperand(line.operand, cfg) {
+			res := findMatchingLoad(lines, i+1, line.operand, cfg)
+			if res.found {
+				result = append(result, line)
+				for j := i + 1; j < res.idx; j++ {
+					result = append(result, lines[j])
+				}
+				i = res.idx // skip the lda on next iteration
+				continue
+			}
+		}
+
+		result = append(result, line)
+	}
+
+	return result
+}
+
+type matchResult struct {
+	idx   int
+	found bool
+}
+
+// findMatchingLoad scans forward from `start` for `lda operand`.
+// Only passes through comments and non-A-modifying code.
+func findMatchingLoad(lines []asmLine, start int, operand string, cfg *Config) matchResult {
+	for i := start; i < len(lines); i++ {
+		l := lines[i]
+
+		if l.optMarker || l.isComment {
+			continue
+		}
+		if l.isLabel {
+			return matchResult{}
+		}
+		if l.isCode && l.opcode == "lda" && l.operand == operand && isSafeStldOperand(l.operand, cfg) {
+			return matchResult{i, true}
+		}
+		if modifiesA(l) {
+			return matchResult{}
+		}
+	}
+	return matchResult{}
+}
+
+// modifiesA returns true if the instruction puts a new value into A.
+func modifiesA(line asmLine) bool {
+	if !line.isCode {
+		return false
+	}
+	switch line.opcode {
+	case "lda", "adc", "sbc", "and", "ora", "eor", "pla", "txa", "tya":
+		return true
+	case "asl", "lsr", "rol", "ror":
+		return line.operand == "" || line.operand == "a"
+	case "inc", "dec":
+		return false
+	default:
+		return false
+	}
+}
+
+// isSafeStldOperand returns true if the operand is safe for store-then-reload optimization.
+// Unsafe: I/O addresses (in cfg.IOMap), self-modifying code pattern (+N), indexed/indirect.
+func isSafeStldOperand(operand string, cfg *Config) bool {
+	if strings.ContainsAny(operand, "(,+") {
+		return false
+	}
+
+	// Check if operand is a direct hex address in an I/O region
+	if strings.HasPrefix(operand, "$") {
+		addr := parseHexOrDec(operand)
+		if addr >= 0 && addr < 65536 && cfg.IOMap[addr] {
+			return false
+		}
+	}
+
+	return true
+}

internal/optimizer/scanner.go

@@ -9,7 +9,7 @@ import (
 // Returns -1 if s is not a parseable simple number (e.g. label references, <label, >label).
 func parseHexOrDec(s string) int {
 	if strings.HasPrefix(s, "$") {
-		v, err := strconv.ParseInt(s[1:], 16, 16)
+		v, err := strconv.ParseUint(s[1:], 16, 16)
 		if err != nil {
 			return -1
 		}
@@ -19,7 +19,7 @@ func parseHexOrDec(s string) int {
 	if idx := strings.IndexAny(s, ",)"); idx >= 0 {
 		s = s[:idx]
 	}
-	v, err := strconv.ParseInt(s, 10, 16)
+	v, err := strconv.ParseUint(s, 10, 16)
 	if err != nil {
 		return -1
 	}