Optimizations of shift operators

internal/commands/shiftl.go

@@ -175,84 +175,177 @@ func (c *ShiftLCommand) Interpret(line preproc.Line, ctx *compiler.CompilerConte
 }
 
 func (c *ShiftLCommand) Generate(ctx *compiler.CompilerContext) ([]string, error) {
+	// Case 1: BYTE destination
+	if c.destVarKind == compiler.KindByte {
+		return c.generateByteShift(ctx)
+	}
+	
+	// Case 2: WORD destination
+	return c.generateWordShift(ctx)
+}
+
+// generateByteShift handles BYTE << amount
+func (c *ShiftLCommand) generateByteShift(ctx *compiler.CompilerContext) ([]string, error) {
 	var asm []string
 	
-	// Check if shift amount >= bit width (result will be zero)
+	// Constant shift amount
-	bitWidth := 8
-	if c.destVarKind == compiler.KindWord {
-		bitWidth = 16
-	}
-
-	amountZero := false
 	if !c.amountIsVar {
-		// Constant amount
+		amount := c.amountValue
-		if c.amountValue >= uint16(bitWidth) {
+		
-			amountZero = true
+		// Shift >= 8 bits -> zero
-		}
+		if amount >= 8 {
+			if amount > 0 {
+				_, _ = fmt.Fprintf(os.Stderr, "%s:%d: warning: shift amount %d >= 8 bits, value will be zero\n",
+					c.line.Filename, c.line.LineNo, amount)
 			}
 			
-	if amountZero {
+			// Store zero
-		// Result is zero, just store zero
+			if c.sourceIsVar && c.sourceVarName == c.destVarName {
-		if c.destVarKind == compiler.KindByte {
+				// Same variable: just zero it
 				asm = append(asm, "\tlda #0")
 				asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
 			} else {
+				// Different: load zero and store
 				asm = append(asm, "\tlda #0")
 				asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
-			asm = append(asm, fmt.Sprintf("\tsta %s+1", c.destVarName))
 			}
 			return asm, nil
 		}
 		
-	// Step 1: Copy source to destination if needed
+		// Shift 0 -> copy source
-	if c.sourceIsVar && c.sourceVarName == c.destVarName {
+		if amount == 0 {
-		// Same variable, no copy needed
+			return c.generateByteCopy(), nil
-	} else {
-		copyAsm := c.generateCopy()
-		asm = append(asm, copyAsm...)
 		}
 		
-	// Step 2: Apply shift
+		// Constant shift 1-7
-	shiftAsm, err := c.generateShift(ctx)
+		return c.generateByteShiftConst(amount), nil
-	if err != nil {
-		return nil, err
 	}
-	asm = append(asm, shiftAsm...)
+	
+	// Variable shift amount
+	return c.generateByteShiftVar(ctx)
+}
+
+// generateByteCopy copies source to destination (BYTE)
+func (c *ShiftLCommand) generateByteCopy() []string {
+	var asm []string
+	
+	if c.sourceIsVar {
+		if c.sourceVarName == c.destVarName {
+			// Same variable, no copy needed
+			return asm
+		}
+		// Different variable
+		asm = append(asm, fmt.Sprintf("\tlda %s", c.sourceVarName))
+		asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+	} else {
+		// Literal
+		val := uint8(c.sourceValue & 0xFF)
+		asm = append(asm, fmt.Sprintf("\tlda #$%02x", val))
+		asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+	}
+	
+	return asm
+}
+
+// generateByteShiftConst generates BYTE << constant (1-7)
+func (c *ShiftLCommand) generateByteShiftConst(amount uint16) []string {
+	var asm []string
+	
+	// Copy source to destination if needed
+	copyAsm := c.generateByteCopy()
+	asm = append(asm, copyAsm...)
+	
+	// Apply shift
+	for i := uint16(0); i < amount; i++ {
+		asm = append(asm, fmt.Sprintf("\tasl %s", c.destVarName))
+	}
+	
+	return asm
+}
+
+// generateByteShiftVar generates BYTE << variable
+func (c *ShiftLCommand) generateByteShiftVar(ctx *compiler.CompilerContext) ([]string, error) {
+	var asm []string
+	
+	// Copy source to destination if needed
+	copyAsm := c.generateByteCopy()
+	asm = append(asm, copyAsm...)
+	
+	// Generate labels
+	loopLabel := ctx.GeneralStack.Push()
+	ctx.GeneralStack.Pop()
+	doneLabel := ctx.GeneralStack.Push()
+	ctx.GeneralStack.Pop()
+	
+	// Variable shift loop
+	asm = append(asm, fmt.Sprintf("\tldx %s", c.amountVarName))
+	asm = append(asm, fmt.Sprintf("\tbeq %s", doneLabel))
+	asm = append(asm, loopLabel)
+	asm = append(asm, fmt.Sprintf("\tasl %s", c.destVarName))
+	asm = append(asm, "\tdex")
+	asm = append(asm, fmt.Sprintf("\tbne %s", loopLabel))
+	asm = append(asm, doneLabel)
 	
 	return asm, nil
 }
 
-// generateCopy generates assembly to copy source to destination
+// generateWordShift handles WORD << amount
-func (c *ShiftLCommand) generateCopy() []string {
+func (c *ShiftLCommand) generateWordShift(ctx *compiler.CompilerContext) ([]string, error) {
+	// Constant shift amount
+	if !c.amountIsVar {
+		amount := c.amountValue
+		
+		// Shift >= 16 bits -> zero
+		if amount >= 16 {
+			if amount > 0 {
+				_, _ = fmt.Fprintf(os.Stderr, "%s:%d: warning: shift amount %d >= 16 bits, value will be zero\n",
+					c.line.Filename, c.line.LineNo, amount)
+			}
+			
+			// Store zero
+			if c.sourceIsVar && c.sourceVarName == c.destVarName {
+				// Same variable: zero both bytes
+				asm := []string{
+					"\tlda #0",
+					fmt.Sprintf("\tsta %s", c.destVarName),
+					fmt.Sprintf("\tsta %s+1", c.destVarName),
+				}
+				return asm, nil
+			} else {
+				// Different: load zero and store to both bytes
+				asm := []string{
+					"\tlda #0",
+					fmt.Sprintf("\tsta %s", c.destVarName),
+					fmt.Sprintf("\tsta %s+1", c.destVarName),
+				}
+				return asm, nil
+			}
+		}
+		
+		// Shift 0 -> copy source
+		if amount == 0 {
+			return c.generateWordCopy(), nil
+		}
+		
+		// Constant shift 1-15
+		return c.generateWordShiftConst(amount), nil
+	}
+	
+	// Variable shift amount
+	return c.generateWordShiftVar(ctx)
+}
+
+// generateWordCopy copies source to destination (WORD)
+func (c *ShiftLCommand) generateWordCopy() []string {
 	var asm []string
 	
-	// If source is literal, just load it
+	if c.sourceIsVar && c.sourceVarName == c.destVarName {
-	if !c.sourceIsVar {
+		// Same variable, no copy needed
-		lo := uint8(c.sourceValue & 0xFF)
-		hi := uint8((c.sourceValue >> 8) & 0xFF)
-
-		if c.destVarKind == compiler.KindByte {
-			asm = append(asm, fmt.Sprintf("\tlda #$%02x", lo))
-			asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
-		} else {
-			asm = append(asm, fmt.Sprintf("\tlda #$%02x", lo))
-			asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
-			// Optimization: don't reload if lo == hi
-			if lo != hi {
-				asm = append(asm, fmt.Sprintf("\tlda #$%02x", hi))
-			}
-			asm = append(asm, fmt.Sprintf("\tsta %s+1", c.destVarName))
-		}
 		return asm
 	}
 	
-	// Source is variable
+	if c.sourceIsVar {
-	if c.destVarKind == compiler.KindByte {
+		// Variable source
-		// Destination is byte
-		asm = append(asm, fmt.Sprintf("\tlda %s", c.sourceVarName))
-		asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
-	} else {
-		// Destination is word
 		if c.sourceVarKind == compiler.KindByte {
 			// Byte -> Word (zero-extend)
 			asm = append(asm, fmt.Sprintf("\tlda %s", c.sourceVarName))
@@ -266,83 +359,96 @@ func (c *ShiftLCommand) generateCopy() []string {
 			asm = append(asm, fmt.Sprintf("\tlda %s+1", c.sourceVarName))
 			asm = append(asm, fmt.Sprintf("\tsta %s+1", c.destVarName))
 		}
+	} else {
+		// Literal source
+		lo := uint8(c.sourceValue & 0xFF)
+		hi := uint8((c.sourceValue >> 8) & 0xFF)
+		asm = append(asm, fmt.Sprintf("\tlda #$%02x", lo))
+		asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+		if lo != hi {
+			asm = append(asm, fmt.Sprintf("\tlda #$%02x", hi))
+		}
+		asm = append(asm, fmt.Sprintf("\tsta %s+1", c.destVarName))
 	}
 	
 	return asm
 }
 
-// generateShift generates assembly to shift destination left by amount
+// generateWordShiftConst generates WORD << constant (1-15)
-func (c *ShiftLCommand) generateShift(ctx *compiler.CompilerContext) ([]string, error) {
+func (c *ShiftLCommand) generateWordShiftConst(amount uint16) []string {
 	var asm []string
 	
-	// Constant amount
+	// Special case: shift >= 8
-	if !c.amountIsVar {
+	if amount >= 8 && amount < 16 {
-		amount := c.amountValue
+		remaining := amount - 8
-		if amount == 0 {
-			return asm, nil // No shift needed
-		}
 		
-		// Determine bit width
+		// Get source low byte
-		bitWidth := 8
+		if c.sourceIsVar {
-		if c.destVarKind == compiler.KindWord {
+			if c.sourceVarName == c.destVarName {
-			bitWidth = 16
+				// Same variable: read from destination (already has value)
-		}
+				asm = append(asm, fmt.Sprintf("\tlda %s", c.destVarName))
-
-		// Warn if shift amount >= bit width (but not for 0)
-		if amount >= uint16(bitWidth) {
-			_, _ = fmt.Fprintf(os.Stderr, "%s:%d: warning: shift amount %d >= %d bits, value will be zero\n",
-				c.line.Filename, c.line.LineNo, amount, bitWidth)
-		}
-
-		if amount >= uint16(bitWidth) {
-			// Shift all bits out -> zero
-			if c.destVarKind == compiler.KindByte {
-				asm = append(asm, "\tlda #0")
-				asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
 			} else {
-				asm = append(asm, "\tlda #0")
+				// Different: read from source
-				asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+				asm = append(asm, fmt.Sprintf("\tlda %s", c.sourceVarName))
+			}
+		} else {
+			// Literal
+			lo := uint8(c.sourceValue & 0xFF)
+			asm = append(asm, fmt.Sprintf("\tlda #$%02x", lo))
+		}
+		
+		// Store to destination high byte
 		asm = append(asm, fmt.Sprintf("\tsta %s+1", c.destVarName))
-			}
+		
-			return asm, nil
+		// Zero low byte
+		asm = append(asm, "\tlda #0")
+		asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+		
+		// Shift high byte remaining bits
+		for i := uint16(0); i < remaining; i++ {
+			asm = append(asm, fmt.Sprintf("\tasl %s+1", c.destVarName))
 		}
 		
-		// Unroll shift loop
+		return asm
+	}
+	
+	// Shift 1-7: normal copy and shift
+	copyAsm := c.generateWordCopy()
+	asm = append(asm, copyAsm...)
+	
+	// Apply shift
 	for i := uint16(0); i < amount; i++ {
-			if c.destVarKind == compiler.KindByte {
-				asm = append(asm, fmt.Sprintf("\tasl %s", c.destVarName))
-			} else {
 		asm = append(asm, fmt.Sprintf("\tasl %s", c.destVarName))
 		asm = append(asm, fmt.Sprintf("\trol %s+1", c.destVarName))
 	}
-		}
-		return asm, nil
-	}
 	
-	// Variable amount
+	return asm
+}
+
+// generateWordShiftVar generates WORD << variable
+func (c *ShiftLCommand) generateWordShiftVar(ctx *compiler.CompilerContext) ([]string, error) {
+	var asm []string
+	
+	// Copy source to destination if needed
+	copyAsm := c.generateWordCopy()
+	asm = append(asm, copyAsm...)
+	
 	// Generate labels
 	loopLabel := ctx.GeneralStack.Push()
 	ctx.GeneralStack.Pop()
 	doneLabel := ctx.GeneralStack.Push()
 	ctx.GeneralStack.Pop()
 	
-	// Load amount into X
+	// Variable shift loop
 	asm = append(asm, fmt.Sprintf("\tldx %s", c.amountVarName))
-
-	// Check for zero amount
 	asm = append(asm, fmt.Sprintf("\tbeq %s", doneLabel))
-
-	// Shift loop
 	asm = append(asm, loopLabel)
-	if c.destVarKind == compiler.KindByte {
-		asm = append(asm, fmt.Sprintf("\tasl %s", c.destVarName))
-	} else {
 	asm = append(asm, fmt.Sprintf("\tasl %s", c.destVarName))
 	asm = append(asm, fmt.Sprintf("\trol %s+1", c.destVarName))
-	}
 	asm = append(asm, "\tdex")
 	asm = append(asm, fmt.Sprintf("\tbne %s", loopLabel))
-
 	asm = append(asm, doneLabel)
+	
 	return asm, nil
 }
+

internal/commands/shiftl_test.go

@@ -518,6 +518,131 @@ func TestShiftLCommand_Generate(t *testing.T) {
 				"_L2",
 			},
 		},
+		{
+			name: "WORD optimization - shift by 8",
+			setup: func(ctx *compiler.CompilerContext) *ShiftLCommand {
+				ctx.SymbolTable.AddVar("result", "", compiler.KindWord, 0, preproc.Line{Filename: "test.c65", LineNo: 1})
+				return &ShiftLCommand{
+					sourceIsVar:   false,
+					sourceValue:   0x1234,
+					amountIsVar:   false,
+					amountValue:   8,
+					destVarName:   "result",
+					destVarKind:   compiler.KindWord,
+				}
+			},
+			wantLines: []string{
+				"\tlda #$34",
+				"\tsta result+1",
+				"\tlda #0",
+				"\tsta result",
+			},
+		},
+		{
+			name: "WORD optimization - shift by 12 (8 + 4)",
+			setup: func(ctx *compiler.CompilerContext) *ShiftLCommand {
+				ctx.SymbolTable.AddVar("result", "", compiler.KindWord, 0, preproc.Line{Filename: "test.c65", LineNo: 1})
+				return &ShiftLCommand{
+					sourceIsVar:   false,
+					sourceValue:   0x00AB,
+					amountIsVar:   false,
+					amountValue:   12,
+					destVarName:   "result",
+					destVarKind:   compiler.KindWord,
+				}
+			},
+			wantLines: []string{
+				"\tlda #$ab",
+				"\tsta result+1",
+				"\tlda #0",
+				"\tsta result",
+				"\tasl result+1",
+				"\tasl result+1",
+				"\tasl result+1",
+				"\tasl result+1",
+			},
+		},
+		{
+			name: "BYTE to WORD conversion with shift",
+			setup: func(ctx *compiler.CompilerContext) *ShiftLCommand {
+				ctx.SymbolTable.AddVar("byteval", "", compiler.KindByte, 0x55, preproc.Line{Filename: "test.c65", LineNo: 1})
+				ctx.SymbolTable.AddVar("result", "", compiler.KindWord, 0, preproc.Line{Filename: "test.c65", LineNo: 1})
+				return &ShiftLCommand{
+					sourceIsVar:   true,
+					sourceVarName: "byteval",
+					sourceVarKind: compiler.KindByte,
+					amountIsVar:   false,
+					amountValue:   4,
+					destVarName:   "result",
+					destVarKind:   compiler.KindWord,
+				}
+			},
+			wantLines: []string{
+				"\tlda byteval",
+				"\tsta result",
+				"\tlda #0",
+				"\tsta result+1",
+				"\tasl result",
+				"\trol result+1",
+				"\tasl result",
+				"\trol result+1",
+				"\tasl result",
+				"\trol result+1",
+				"\tasl result",
+				"\trol result+1",
+			},
+		},
+		{
+			name: "WORD to BYTE conversion with shift (truncation)",
+			setup: func(ctx *compiler.CompilerContext) *ShiftLCommand {
+				ctx.SymbolTable.AddVar("wordval", "", compiler.KindWord, 0x1234, preproc.Line{Filename: "test.c65", LineNo: 1})
+				ctx.SymbolTable.AddVar("result", "", compiler.KindByte, 0, preproc.Line{Filename: "test.c65", LineNo: 1})
+				return &ShiftLCommand{
+					sourceIsVar:   true,
+					sourceVarName: "wordval",
+					sourceVarKind: compiler.KindWord,
+					amountIsVar:   false,
+					amountValue:   4,
+					destVarName:   "result",
+					destVarKind:   compiler.KindByte,
+				}
+			},
+			wantLines: []string{
+				"\tlda wordval",
+				"\tsta result",
+				"\tasl result",
+				"\tasl result",
+				"\tasl result",
+				"\tasl result",
+			},
+		},
+		{
+			name: "WORD same source and destination",
+			setup: func(ctx *compiler.CompilerContext) *ShiftLCommand {
+				ctx.SymbolTable.AddVar("value", "", compiler.KindWord, 0x1234, preproc.Line{Filename: "test.c65", LineNo: 1})
+				ctx.SymbolTable.AddVar("shift", "", compiler.KindByte, 2, preproc.Line{Filename: "test.c65", LineNo: 1})
+				return &ShiftLCommand{
+					sourceIsVar:   true,
+					sourceVarName: "value",
+					sourceVarKind: compiler.KindWord,
+					amountIsVar:   true,
+					amountVarName: "shift",
+					amountVarKind: compiler.KindByte,
+					destVarName:   "value",
+					destVarKind:   compiler.KindWord,
+				}
+			},
+			wantLines: []string{
+				"\tldx shift",
+				"\tbeq _L2",
+				"_L1",
+				"\tasl value",
+				"\trol value+1",
+				"\tdex",
+				"\tbne _L1",
+				"_L2",
+			},
+		},
 	}
 
 	for _, tt := range tests {

internal/commands/shiftr.go

@@ -175,83 +175,320 @@ func (c *ShiftRCommand) Interpret(line preproc.Line, ctx *compiler.CompilerConte
 }
 
 func (c *ShiftRCommand) Generate(ctx *compiler.CompilerContext) ([]string, error) {
+	// Case 1: BYTE destination
+	if c.destVarKind == compiler.KindByte {
+		return c.generateByteShift(ctx)
+	}
+	
+	// Case 2: WORD destination
+	return c.generateWordShift(ctx)
+}
+
+// generateByteShift handles BYTE >> amount
+func (c *ShiftRCommand) generateByteShift(ctx *compiler.CompilerContext) ([]string, error) {
+	// Special case: WORD source, BYTE destination
+	if c.sourceVarKind == compiler.KindWord {
+		return c.generateWordToByteShift(ctx)
+	}
+	
 	var asm []string
 	
-	// Check if shift amount >= bit width (result will be zero)
+	// Constant shift amount
-	bitWidth := 8
-	if c.destVarKind == compiler.KindWord {
-		bitWidth = 16
-	}
-
-	amountZero := false
 	if !c.amountIsVar {
-		// Constant amount
+		amount := c.amountValue
-		if c.amountValue >= uint16(bitWidth) {
+		
-			amountZero = true
+		// Shift >= 8 bits -> zero
-		}
+		if amount >= 8 {
+			if amount > 0 {
+				_, _ = fmt.Fprintf(os.Stderr, "%s:%d: warning: shift amount %d >= 8 bits, value will be zero\n",
+					c.line.Filename, c.line.LineNo, amount)
 			}
 			
-	if amountZero {
+			// Store zero
-		// Result is zero, just store zero
+			if c.sourceIsVar && c.sourceVarName == c.destVarName {
-		if c.destVarKind == compiler.KindByte {
+				// Same variable: just zero it
 				asm = append(asm, "\tlda #0")
 				asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
 			} else {
+				// Different: load zero and store
 				asm = append(asm, "\tlda #0")
 				asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
-			asm = append(asm, fmt.Sprintf("\tsta %s+1", c.destVarName))
 			}
 			return asm, nil
 		}
 		
-	// Step 1: Copy source to destination if needed
+		// Shift 0 -> copy source
-	if c.sourceIsVar && c.sourceVarName == c.destVarName {
+		if amount == 0 {
-		// Same variable, no copy needed
+			return c.generateByteCopy(), nil
-	} else {
-		copyAsm := c.generateCopy()
-		asm = append(asm, copyAsm...)
 		}
 		
-	// Step 2: Apply shift
+		// Constant shift 1-7
-	shiftAsm, err := c.generateShift(ctx)
+		return c.generateByteShiftConst(amount), nil
-	if err != nil {
-		return nil, err
 	}
-	asm = append(asm, shiftAsm...)
+	
+	// Variable shift amount
+	return c.generateByteShiftVar(ctx)
+}
+
+// generateByteCopy copies source to destination (BYTE)
+func (c *ShiftRCommand) generateByteCopy() []string {
+	var asm []string
+	
+	if c.sourceIsVar {
+		if c.sourceVarName == c.destVarName {
+			// Same variable, no copy needed
+			return asm
+		}
+		// Different variable
+		if c.sourceVarKind == compiler.KindWord {
+			// WORD source, BYTE destination - just take low byte
+			asm = append(asm, fmt.Sprintf("\tlda %s", c.sourceVarName))
+			asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+		} else {
+			// BYTE source
+			asm = append(asm, fmt.Sprintf("\tlda %s", c.sourceVarName))
+			asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+		}
+	} else {
+		// Literal
+		val := uint8(c.sourceValue & 0xFF)
+		asm = append(asm, fmt.Sprintf("\tlda #$%02x", val))
+		asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+	}
+	
+	return asm
+}
+
+// generateByteShiftConst generates BYTE >> constant (1-7)
+func (c *ShiftRCommand) generateByteShiftConst(amount uint16) []string {
+	var asm []string
+	
+	// Copy source to destination if needed
+	copyAsm := c.generateByteCopy()
+	asm = append(asm, copyAsm...)
+	
+	// Apply shift (right shift uses LSR)
+	for i := uint16(0); i < amount; i++ {
+		asm = append(asm, fmt.Sprintf("\tlsr %s", c.destVarName))
+	}
+	
+	return asm
+}
+
+// generateByteShiftVar generates BYTE >> variable
+func (c *ShiftRCommand) generateByteShiftVar(ctx *compiler.CompilerContext) ([]string, error) {
+	var asm []string
+	
+	// Copy source to destination if needed
+	copyAsm := c.generateByteCopy()
+	asm = append(asm, copyAsm...)
+	
+	// Generate labels
+	loopLabel := ctx.GeneralStack.Push()
+	ctx.GeneralStack.Pop()
+	doneLabel := ctx.GeneralStack.Push()
+	ctx.GeneralStack.Pop()
+	
+	// Variable shift loop (right shift uses LSR)
+	asm = append(asm, fmt.Sprintf("\tldx %s", c.amountVarName))
+	asm = append(asm, fmt.Sprintf("\tbeq %s", doneLabel))
+	asm = append(asm, loopLabel)
+	asm = append(asm, fmt.Sprintf("\tlsr %s", c.destVarName))
+	asm = append(asm, "\tdex")
+	asm = append(asm, fmt.Sprintf("\tbne %s", loopLabel))
+	asm = append(asm, doneLabel)
 	
 	return asm, nil
 }
 
-// generateCopy generates assembly to copy source to destination
+// generateWordToByteShift handles WORD >> amount -> BYTE
-func (c *ShiftRCommand) generateCopy() []string {
+func (c *ShiftRCommand) generateWordToByteShift(ctx *compiler.CompilerContext) ([]string, error) {
 	var asm []string
 	
-	// If source is literal, just load it
+	// Constant shift amount
-	if !c.sourceIsVar {
+	if !c.amountIsVar {
-		lo := uint8(c.sourceValue & 0xFF)
+		amount := c.amountValue
-		hi := uint8((c.sourceValue >> 8) & 0xFF)
 		
-		if c.destVarKind == compiler.KindByte {
+		// Shift >= 16 bits -> zero
-			asm = append(asm, fmt.Sprintf("\tlda #$%02x", lo))
+		if amount >= 16 {
-			asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+			if amount > 0 {
-		} else {
+				_, _ = fmt.Fprintf(os.Stderr, "%s:%d: warning: shift amount %d >= 16 bits, value will be zero\n",
-			asm = append(asm, fmt.Sprintf("\tlda #$%02x", lo))
+					c.line.Filename, c.line.LineNo, amount)
-			asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
-			if lo != hi {
-				asm = append(asm, fmt.Sprintf("\tlda #$%02x", hi))
-			}
-			asm = append(asm, fmt.Sprintf("\tsta %s+1", c.destVarName))
-		}
-		return asm
 			}
 			
-	// Source is variable
+			// Store zero
-	if c.destVarKind == compiler.KindByte {
+			asm = append(asm, "\tlda #0")
-		// Destination is byte
+			asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+			return asm, nil
+		}
+		
+		// Shift 0 -> just take low byte
+		if amount == 0 {
+			if c.sourceIsVar {
 				asm = append(asm, fmt.Sprintf("\tlda %s", c.sourceVarName))
 				asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
 			} else {
-		// Destination is word
+				val := uint8(c.sourceValue & 0xFF)
+				asm = append(asm, fmt.Sprintf("\tlda #$%02x", val))
+				asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+			}
+			return asm, nil
+		}
+		
+		// For WORD -> BYTE right shift, we need to handle the full WORD shift
+		// then take the low byte. This is more complex than BYTE shift.
+		
+		// Shift 8-15: result depends only on high byte
+		if amount >= 8 && amount < 16 {
+			remaining := amount - 8
+			
+			// Get high byte
+			if c.sourceIsVar {
+				asm = append(asm, fmt.Sprintf("\tlda %s+1", c.sourceVarName))
+			} else {
+				hi := uint8((c.sourceValue >> 8) & 0xFF)
+				asm = append(asm, fmt.Sprintf("\tlda #$%02x", hi))
+			}
+			
+			// Store to destination
+			asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+			
+			// Shift remaining bits
+			for i := uint16(0); i < remaining; i++ {
+				asm = append(asm, fmt.Sprintf("\tlsr %s", c.destVarName))
+			}
+			
+			return asm, nil
+		}
+		
+		// Shift 1-7: need full WORD shift, then take low byte
+		// We'll use the destination as a temporary for the low byte
+		// and handle high byte in A register
+		
+		if c.sourceIsVar {
+			// Load low byte to destination
+			asm = append(asm, fmt.Sprintf("\tlda %s", c.sourceVarName))
+			asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+			
+			// Load high byte to A
+			asm = append(asm, fmt.Sprintf("\tlda %s+1", c.sourceVarName))
+		} else {
+			// Literal source
+			lo := uint8(c.sourceValue & 0xFF)
+			hi := uint8((c.sourceValue >> 8) & 0xFF)
+			
+			asm = append(asm, fmt.Sprintf("\tlda #$%02x", lo))
+			asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+			asm = append(asm, fmt.Sprintf("\tlda #$%02x", hi))
+		}
+		
+		// Apply shifts: lsr A (high byte), ror destination (low byte)
+		for i := uint16(0); i < amount; i++ {
+			asm = append(asm, "\tlsr")
+			asm = append(asm, fmt.Sprintf("\tror %s", c.destVarName))
+		}
+		
+		return asm, nil
+	}
+	
+	// Variable shift amount - use general approach with loop
+	// We need X for shift count, A for high byte, destination for low byte
+	
+	// Generate labels
+	loopLabel := ctx.GeneralStack.Push()
+	ctx.GeneralStack.Pop()
+	doneLabel := ctx.GeneralStack.Push()
+	ctx.GeneralStack.Pop()
+	
+	if c.sourceIsVar {
+		// Load low byte to destination
+		asm = append(asm, fmt.Sprintf("\tlda %s", c.sourceVarName))
+		asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+		
+		// Load high byte to A
+		asm = append(asm, fmt.Sprintf("\tlda %s+1", c.sourceVarName))
+	} else {
+		// Literal source
+		lo := uint8(c.sourceValue & 0xFF)
+		hi := uint8((c.sourceValue >> 8) & 0xFF)
+		
+		asm = append(asm, fmt.Sprintf("\tlda #$%02x", lo))
+		asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+		asm = append(asm, fmt.Sprintf("\tlda #$%02x", hi))
+	}
+	
+	// Load shift amount to X
+	asm = append(asm, fmt.Sprintf("\tldx %s", c.amountVarName))
+	asm = append(asm, fmt.Sprintf("\tbeq %s", doneLabel))
+	
+	// Shift loop
+	asm = append(asm, loopLabel)
+	asm = append(asm, "\tlsr")
+	asm = append(asm, fmt.Sprintf("\tror %s", c.destVarName))
+	asm = append(asm, "\tdex")
+	asm = append(asm, fmt.Sprintf("\tbne %s", loopLabel))
+	asm = append(asm, doneLabel)
+	
+	return asm, nil
+}
+
+// generateWordShift handles WORD >> amount
+func (c *ShiftRCommand) generateWordShift(ctx *compiler.CompilerContext) ([]string, error) {
+	// Constant shift amount
+	if !c.amountIsVar {
+		amount := c.amountValue
+		
+		// Shift >= 16 bits -> zero
+		if amount >= 16 {
+			if amount > 0 {
+				_, _ = fmt.Fprintf(os.Stderr, "%s:%d: warning: shift amount %d >= 16 bits, value will be zero\n",
+					c.line.Filename, c.line.LineNo, amount)
+			}
+			
+			// Store zero
+			if c.sourceIsVar && c.sourceVarName == c.destVarName {
+				// Same variable: zero both bytes
+				asm := []string{
+					"\tlda #0",
+					fmt.Sprintf("\tsta %s", c.destVarName),
+					fmt.Sprintf("\tsta %s+1", c.destVarName),
+				}
+				return asm, nil
+			} else {
+				// Different: load zero and store to both bytes
+				asm := []string{
+					"\tlda #0",
+					fmt.Sprintf("\tsta %s", c.destVarName),
+					fmt.Sprintf("\tsta %s+1", c.destVarName),
+				}
+				return asm, nil
+			}
+		}
+		
+		// Shift 0 -> copy source
+		if amount == 0 {
+			return c.generateWordCopy(), nil
+		}
+		
+		// Constant shift 1-15
+		return c.generateWordShiftConst(amount), nil
+	}
+	
+	// Variable shift amount
+	return c.generateWordShiftVar(ctx)
+}
+
+// generateWordCopy copies source to destination (WORD)
+func (c *ShiftRCommand) generateWordCopy() []string {
+	var asm []string
+	
+	if c.sourceIsVar && c.sourceVarName == c.destVarName {
+		// Same variable, no copy needed
+		return asm
+	}
+	
+	if c.sourceIsVar {
+		// Variable source
 		if c.sourceVarKind == compiler.KindByte {
 			// Byte -> Word (zero-extend)
 			asm = append(asm, fmt.Sprintf("\tlda %s", c.sourceVarName))
@@ -265,84 +502,96 @@ func (c *ShiftRCommand) generateCopy() []string {
 			asm = append(asm, fmt.Sprintf("\tlda %s+1", c.sourceVarName))
 			asm = append(asm, fmt.Sprintf("\tsta %s+1", c.destVarName))
 		}
+	} else {
+		// Literal source
+		lo := uint8(c.sourceValue & 0xFF)
+		hi := uint8((c.sourceValue >> 8) & 0xFF)
+		asm = append(asm, fmt.Sprintf("\tlda #$%02x", lo))
+		asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+		if lo != hi {
+			asm = append(asm, fmt.Sprintf("\tlda #$%02x", hi))
+		}
+		asm = append(asm, fmt.Sprintf("\tsta %s+1", c.destVarName))
 	}
 	
 	return asm
 }
 
-// generateShift generates assembly to shift destination right by amount
+// generateWordShiftConst generates WORD >> constant (1-15)
-func (c *ShiftRCommand) generateShift(ctx *compiler.CompilerContext) ([]string, error) {
+func (c *ShiftRCommand) generateWordShiftConst(amount uint16) []string {
 	var asm []string
 	
-	// Constant amount
+	// Special case: shift >= 8
-	if !c.amountIsVar {
+	if amount >= 8 && amount < 16 {
-		amount := c.amountValue
+		remaining := amount - 8
-		if amount == 0 {
-			return asm, nil // No shift needed
-		}
 		
-		// Determine bit width
+		// Get source high byte
-		bitWidth := 8
+		if c.sourceIsVar {
-		if c.destVarKind == compiler.KindWord {
+			if c.sourceVarName == c.destVarName {
-			bitWidth = 16
+				// Same variable: read from destination (already has value)
-		}
+				asm = append(asm, fmt.Sprintf("\tlda %s+1", c.destVarName))
-
-		// Warn if shift amount >= bit width (but not for 0)
-		if amount >= uint16(bitWidth) {
-			_, _ = fmt.Fprintf(os.Stderr, "%s:%d: warning: shift amount %d >= %d bits, value will be zero\n",
-				c.line.Filename, c.line.LineNo, amount, bitWidth)
-		}
-
-		if amount >= uint16(bitWidth) {
-			// Shift all bits out -> zero
-			if c.destVarKind == compiler.KindByte {
-				asm = append(asm, "\tlda #0")
-				asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
 			} else {
-				asm = append(asm, "\tlda #0")
+				// Different: read from source
+				asm = append(asm, fmt.Sprintf("\tlda %s+1", c.sourceVarName))
+			}
+		} else {
+			// Literal
+			hi := uint8((c.sourceValue >> 8) & 0xFF)
+			asm = append(asm, fmt.Sprintf("\tlda #$%02x", hi))
+		}
+		
+		// Store to destination low byte
 		asm = append(asm, fmt.Sprintf("\tsta %s", c.destVarName))
+		
+		// Zero high byte
+		asm = append(asm, "\tlda #0")
 		asm = append(asm, fmt.Sprintf("\tsta %s+1", c.destVarName))
-			}
+		
-			return asm, nil
+		// Shift low byte remaining bits (right shift)
+		for i := uint16(0); i < remaining; i++ {
+			asm = append(asm, fmt.Sprintf("\tlsr %s", c.destVarName))
 		}
 		
-		// Unroll shift loop
+		return asm
+	}
+	
+	// Shift 1-7: normal copy and shift
+	copyAsm := c.generateWordCopy()
+	asm = append(asm, copyAsm...)
+	
+	// Apply shift (right shift uses LSR high byte, ROR low byte)
 	for i := uint16(0); i < amount; i++ {
-			if c.destVarKind == compiler.KindByte {
-				asm = append(asm, fmt.Sprintf("\tlsr %s", c.destVarName))
-			} else {
 		asm = append(asm, fmt.Sprintf("\tlsr %s+1", c.destVarName))
 		asm = append(asm, fmt.Sprintf("\tror %s", c.destVarName))
 	}
-		}
-		return asm, nil
-	}
 	
-	// Variable amount
+	return asm
+}
+
+// generateWordShiftVar generates WORD >> variable
+func (c *ShiftRCommand) generateWordShiftVar(ctx *compiler.CompilerContext) ([]string, error) {
+	var asm []string
+	
+	// Copy source to destination if needed
+	copyAsm := c.generateWordCopy()
+	asm = append(asm, copyAsm...)
+	
 	// Generate labels
 	loopLabel := ctx.GeneralStack.Push()
 	ctx.GeneralStack.Pop()
 	doneLabel := ctx.GeneralStack.Push()
 	ctx.GeneralStack.Pop()
 	
-
+	// Variable shift loop (right shift uses LSR high byte, ROR low byte)
-	// Load amount into X
 	asm = append(asm, fmt.Sprintf("\tldx %s", c.amountVarName))
-
-	// Check for zero amount
 	asm = append(asm, fmt.Sprintf("\tbeq %s", doneLabel))
-
-	// Shift loop
 	asm = append(asm, loopLabel)
-	if c.destVarKind == compiler.KindByte {
-		asm = append(asm, fmt.Sprintf("\tlsr %s", c.destVarName))
-	} else {
 	asm = append(asm, fmt.Sprintf("\tlsr %s+1", c.destVarName))
 	asm = append(asm, fmt.Sprintf("\tror %s", c.destVarName))
-	}
 	asm = append(asm, "\tdex")
 	asm = append(asm, fmt.Sprintf("\tbne %s", loopLabel))
-
 	asm = append(asm, doneLabel)
+	
 	return asm, nil
 }
+

internal/commands/shiftr_test.go

@@ -518,6 +518,136 @@ func TestShiftRCommand_Generate(t *testing.T) {
 				"_L2",
 			},
 		},
+		{
+			name: "WORD optimization - shift by 8",
+			setup: func(ctx *compiler.CompilerContext) *ShiftRCommand {
+				ctx.SymbolTable.AddVar("result", "", compiler.KindWord, 0, preproc.Line{Filename: "test.c65", LineNo: 1})
+				return &ShiftRCommand{
+					sourceIsVar:   false,
+					sourceValue:   0x1234,
+					amountIsVar:   false,
+					amountValue:   8,
+					destVarName:   "result",
+					destVarKind:   compiler.KindWord,
+				}
+			},
+			wantLines: []string{
+				"\tlda #$12",
+				"\tsta result",
+				"\tlda #0",
+				"\tsta result+1",
+			},
+		},
+		{
+			name: "WORD optimization - shift by 12 (8 + 4)",
+			setup: func(ctx *compiler.CompilerContext) *ShiftRCommand {
+				ctx.SymbolTable.AddVar("result", "", compiler.KindWord, 0, preproc.Line{Filename: "test.c65", LineNo: 1})
+				return &ShiftRCommand{
+					sourceIsVar:   false,
+					sourceValue:   0xAB00,
+					amountIsVar:   false,
+					amountValue:   12,
+					destVarName:   "result",
+					destVarKind:   compiler.KindWord,
+				}
+			},
+			wantLines: []string{
+				"\tlda #$ab",
+				"\tsta result",
+				"\tlda #0",
+				"\tsta result+1",
+				"\tlsr result",
+				"\tlsr result",
+				"\tlsr result",
+				"\tlsr result",
+			},
+		},
+		{
+			name: "BYTE to WORD conversion with shift",
+			setup: func(ctx *compiler.CompilerContext) *ShiftRCommand {
+				ctx.SymbolTable.AddVar("byteval", "", compiler.KindByte, 0x55, preproc.Line{Filename: "test.c65", LineNo: 1})
+				ctx.SymbolTable.AddVar("result", "", compiler.KindWord, 0, preproc.Line{Filename: "test.c65", LineNo: 1})
+				return &ShiftRCommand{
+					sourceIsVar:   true,
+					sourceVarName: "byteval",
+					sourceVarKind: compiler.KindByte,
+					amountIsVar:   false,
+					amountValue:   4,
+					destVarName:   "result",
+					destVarKind:   compiler.KindWord,
+				}
+			},
+			wantLines: []string{
+				"\tlda byteval",
+				"\tsta result",
+				"\tlda #0",
+				"\tsta result+1",
+				"\tlsr result+1",
+				"\tror result",
+				"\tlsr result+1",
+				"\tror result",
+				"\tlsr result+1",
+				"\tror result",
+				"\tlsr result+1",
+				"\tror result",
+			},
+		},
+		{
+			name: "WORD to BYTE conversion with shift (truncation)",
+			setup: func(ctx *compiler.CompilerContext) *ShiftRCommand {
+				ctx.SymbolTable.AddVar("wordval", "", compiler.KindWord, 0x1234, preproc.Line{Filename: "test.c65", LineNo: 1})
+				ctx.SymbolTable.AddVar("result", "", compiler.KindByte, 0, preproc.Line{Filename: "test.c65", LineNo: 1})
+				return &ShiftRCommand{
+					sourceIsVar:   true,
+					sourceVarName: "wordval",
+					sourceVarKind: compiler.KindWord,
+					amountIsVar:   false,
+					amountValue:   4,
+					destVarName:   "result",
+					destVarKind:   compiler.KindByte,
+				}
+			},
+			wantLines: []string{
+				"\tlda wordval",
+				"\tsta result",
+				"\tlda wordval+1",
+				"\tlsr",
+				"\tror result",
+				"\tlsr",
+				"\tror result",
+				"\tlsr",
+				"\tror result",
+				"\tlsr",
+				"\tror result",
+			},
+		},
+		{
+			name: "WORD same source and destination",
+			setup: func(ctx *compiler.CompilerContext) *ShiftRCommand {
+				ctx.SymbolTable.AddVar("value", "", compiler.KindWord, 0x1234, preproc.Line{Filename: "test.c65", LineNo: 1})
+				ctx.SymbolTable.AddVar("shift", "", compiler.KindByte, 2, preproc.Line{Filename: "test.c65", LineNo: 1})
+				return &ShiftRCommand{
+					sourceIsVar:   true,
+					sourceVarName: "value",
+					sourceVarKind: compiler.KindWord,
+					amountIsVar:   true,
+					amountVarName: "shift",
+					amountVarKind: compiler.KindByte,
+					destVarName:   "value",
+					destVarKind:   compiler.KindWord,
+				}
+			},
+			wantLines: []string{
+				"\tldx shift",
+				"\tbeq _L2",
+				"_L1",
+				"\tlsr value+1",
+				"\tror value",
+				"\tdex",
+				"\tbne _L1",
+				"_L2",
+			},
+		},
 	}
 
 	for _, tt := range tests {