First step of code cleanup and refactoring.

Moved the localVarIndex setters into a separate helperClass and optimized bytecodesize in regard to variable pushes

src/main/java/CodeGen/CodeGenHelper.java

@@ -0,0 +1,36 @@
+package CodeGen;
+
+import abstractSyntaxTree.Expression.SubReceiver;
+
+import java.util.LinkedHashMap;
+import java.util.List;
+
+public class CodeGenHelper {
+
+    public static String getFieldDescriptor(String type) {
+        switch (type) {
+            case "int":
+                return "I";
+            case "boolean":
+                return "Z";
+            case "char":
+                return "C";
+            default:
+                return "L" + type + ";";
+        }
+    }
+
+    public static int GetLocalVarIndex(LinkedHashMap<String, String> localVars, String varToSearchFor) {
+        int index = -1;
+        int counter = 0;
+        for (String key : localVars.keySet()) {
+            if (key.equals(varToSearchFor)) {
+                index = counter + 1; // +1 because the first local variable is at index 1, 0 is used for "this"
+                break;
+            }
+            counter++;
+        }
+        return index;
+    }
+
+}

src/main/java/abstractSyntaxTree/Class/FieldDecl.java

@@ -1,5 +1,6 @@
 package abstractSyntaxTree.Class;
 
+import CodeGen.CodeGenHelper;
 import TypeCheck.AbstractType;
 import TypeCheck.TypeCheckException;
 import TypeCheck.TypeCheckHelper;
@@ -47,23 +48,11 @@ public class FieldDecl extends AbstractType implements Node {
     }
 
     public void codeGen(ClassWriter cw) {
-        FieldVisitor fv = cw.visitField(Opcodes.ACC_PUBLIC, identifier, getFieldDescriptor(), null, null);
+        String descriptor = CodeGenHelper.getFieldDescriptor(type);
+        FieldVisitor fv = cw.visitField(Opcodes.ACC_PUBLIC, identifier, descriptor, null, null);
         fv.visitEnd();
     }
 
-    private String getFieldDescriptor() {
-        switch (type) {
-            case "int":
-                return "I";
-            case "boolean":
-                return "Z";
-            case "char":
-                return "C";
-            default:
-                return "L" + type + ";";
-        }
-    }
-
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;

src/main/java/abstractSyntaxTree/Class/MethodDecl.java

@@ -1,5 +1,6 @@
 package abstractSyntaxTree.Class;
 
+import CodeGen.CodeGenHelper;
 import TypeCheck.TypeCheckException;
 import TypeCheck.TypeCheckResult;
 import abstractSyntaxTree.Node;
@@ -91,7 +92,7 @@ public class MethodDecl implements Node {
                                 default -> mv.visitInsn(Opcodes.ACONST_NULL);
                             }
                         }
-                        descriptor = getFieldDescriptor(field.type);
+                        descriptor = CodeGenHelper.getFieldDescriptor(field.type);
                         mv.visitFieldInsn(Opcodes.PUTFIELD, classThatContainsMethod, fieldName, descriptor);
                         fieldFound = true;
                         break;
@@ -215,19 +216,6 @@ public class MethodDecl implements Node {
         return descriptor.toString();
     }
 
-    private String getFieldDescriptor(String type) {
-        switch (type) {
-            case "int":
-                return "I";
-            case "boolean":
-                return "Z";
-            case "char":
-                return "C";
-            default:
-                return "L" + type + ";";
-        }
-    }
-
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;

src/main/java/abstractSyntaxTree/Datatype/CharDatatype.java

@@ -3,6 +3,7 @@ package abstractSyntaxTree.Datatype;
 import TypeCheck.AbstractType;
 import TypeCheck.TypeCheckResult;
 import org.objectweb.asm.MethodVisitor;
+import org.objectweb.asm.Opcodes;
 
 import java.util.Objects;
 
@@ -21,11 +22,13 @@ public class CharDatatype extends AbstractType implements IDatatype{
 
     @Override
     public void codeGen(MethodVisitor mv) throws Exception {
-
+        if (value <= 5) {
-        // Possible use of BIPUSH and SIPUSH if the value is small enough
+            mv.visitInsn(Opcodes.ICONST_0 + value);
-        //This saves space in the bytecode which is not very relevant at this point, but could be implemented anyway
+        } else if (value <= Byte.MAX_VALUE) {
-
+            mv.visitIntInsn(Opcodes.BIPUSH, value);
-        mv.visitLdcInsn((int)value);
+        } else {
+            mv.visitIntInsn(Opcodes.SIPUSH, value);
+        }
     }
     @Override
     public boolean equals(Object o) {

src/main/java/abstractSyntaxTree/Datatype/IntDatatype.java

@@ -21,8 +21,6 @@ public class IntDatatype extends AbstractType implements IDatatype{
 
     @Override
     public void codeGen(MethodVisitor mv) throws Exception {
-        
-        //Example of using BIPUSH and SIPUSH for optimizing bytecode size
         if (value >= Byte.MIN_VALUE && value <= Byte.MAX_VALUE)
             mv.visitIntInsn(Opcodes.BIPUSH, value);
         else if (value >= Short.MIN_VALUE && value <= Short.MAX_VALUE)

src/main/java/abstractSyntaxTree/Expression/CharConstantExpression.java

@@ -27,7 +27,13 @@ public class CharConstantExpression extends AbstractType implements IExpression{
 
     @Override
     public void codeGen(MethodVisitor mv, LinkedHashMap<String, String> localVars, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext) throws Exception {
-        mv.visitIntInsn(Opcodes.BIPUSH, (int) value);
+        if (value <= 5) {
+            mv.visitInsn(Opcodes.ICONST_0 + value);
+        } else if (value <= Byte.MAX_VALUE) {
+            mv.visitIntInsn(Opcodes.BIPUSH, value);
+        } else {
+            mv.visitIntInsn(Opcodes.SIPUSH, value);
+        }
     }
 
     @Override

src/main/java/abstractSyntaxTree/Expression/InstVarExpression.java

@@ -1,5 +1,6 @@
 package abstractSyntaxTree.Expression;
 
+import CodeGen.CodeGenHelper;
 import TypeCheck.AbstractType;
 import TypeCheck.TypeCheckException;
 import TypeCheck.TypeCheckResult;
@@ -74,15 +75,7 @@ public class InstVarExpression extends AbstractType implements IExpression {
 
                 if (i == 0) {
                     // Load the local variable onto the stack
-                    int index = -1;
+                    int index = CodeGenHelper.GetLocalVarIndex(localVars, this.receivers.get(i).identifier);
-                    int counter = 0;
-                    for (String key : localVars.keySet()) {
-                        if (key.equals(this.receivers.get(i).identifier)) {
-                            index = counter + 1; // +1 because the first local variable is at index 1, 0 is used for "this"
-                            break;
-                        }
-                        counter++;
-                    }
 
                     if (index == -1) {
                         if (typeContext.get(thisClass).get(this.receivers.get(i).identifier) != null) {
@@ -119,15 +112,7 @@ public class InstVarExpression extends AbstractType implements IExpression {
                 else {
 
                     // Load the local variable onto the stack
-                    int index = -1;
+                    int index = CodeGenHelper.GetLocalVarIndex(localVars, this.receivers.get(i).identifier);
-                    int counter = 0;
-                    for (String key : localVars.keySet()) {
-                        if (key.equals(this.receivers.get(i).identifier)) {
-                            index = counter + 1; // +1 because the first local variable is at index 1, 0 is used for "this"
-                            break;
-                        }
-                        counter++;
-                    }
 
                     if (index == -1) {
                         if (typeContext.get(typeOfReciever).get(this.receivers.get(i).identifier) != null) {
@@ -157,15 +142,7 @@ public class InstVarExpression extends AbstractType implements IExpression {
             // Load the field in fieldName
 
             // Load the local variable onto the stack
-            int index = -1;
+            int index = CodeGenHelper.GetLocalVarIndex(localVars, fieldName);
-            int counter = 0;
-            for (String key : localVars.keySet()) {
-                if (key.equals(fieldName)) {
-                    index = counter + 1; // +1 because the first local variable is at index 1, 0 is used for "this"
-                    break;
-                }
-                counter++;
-            }
 
             if (index == -1) {
                 if (typeContext.get(typeOfReciever).get(fieldName) != null) {
@@ -192,15 +169,7 @@ public class InstVarExpression extends AbstractType implements IExpression {
             }
         } else if (receivers.get(0).thisExpression) {
             // Load the local variable or instVar of this onto the stack
-            int index = -1;
+            int index = CodeGenHelper.GetLocalVarIndex(localVars, fieldName);
-            int counter = 0;
-            for (String key : localVars.keySet()) {
-                if (key.equals(fieldName)) {
-                    index = counter + 1; // +1 because the first local variable is at index 1, 0 is used for "this"
-                    break;
-                }
-                counter++;
-            }
 
             if (index == -1) {
                 mv.visitVarInsn(Opcodes.ALOAD, 0);

src/main/java/abstractSyntaxTree/Expression/IntConstantExpression.java

@@ -28,9 +28,16 @@ public class IntConstantExpression extends AbstractType implements IExpression{
 
     @Override
     public void codeGen(MethodVisitor mv, LinkedHashMap<String, String> localVars, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext) throws Exception {
-        //TODO: When we are finished this can be done more efficiently
+        if (value >= -1 && value <= 5) {
+            mv.visitInsn(Opcodes.ICONST_0 + value);
+        } else if (value >= Byte.MIN_VALUE && value <= Byte.MAX_VALUE) {
+            mv.visitIntInsn(Opcodes.BIPUSH, value);
+        } else if (value >= Short.MIN_VALUE && value <= Short.MAX_VALUE) {
+            mv.visitIntInsn(Opcodes.SIPUSH, value);
+        } else {
             mv.visitLdcInsn(value);
         }
+    }
 
     @Override
     public boolean equals(Object o) {

src/main/java/abstractSyntaxTree/Expression/LocalVarIdentifier.java

@@ -1,5 +1,6 @@
 package abstractSyntaxTree.Expression;
 
+import CodeGen.CodeGenHelper;
 import TypeCheck.AbstractType;
 import TypeCheck.TypeCheckException;
 import TypeCheck.TypeCheckHelper;
@@ -52,15 +53,7 @@ public class LocalVarIdentifier extends AbstractType implements IExpression{
         if (localVars.containsKey(identifier)) {
             type = localVars.get(identifier);
             // Find the index of the variable
-            int index = -1;
+            int index = CodeGenHelper.GetLocalVarIndex(localVars, identifier);
-            int counter = 0;
-            for (String key : localVars.keySet()) {
-                if (key.equals(identifier)) {
-                    index = counter + 1; // +1 because the first local variable is at index 1, 0 is used for "this"
-                    break;
-                }
-                counter++;
-            }
 
             if (index == -1) {
                 throw new Exception("Variable " + identifier + " not found");
@@ -84,25 +77,13 @@ public class LocalVarIdentifier extends AbstractType implements IExpression{
             // Load "this" onto the stack
             mv.visitVarInsn(Opcodes.ALOAD, 0);
             // Get the field from "this"
-            mv.visitFieldInsn(Opcodes.GETFIELD, thisClass, identifier, getFieldDescriptor(type));
+            String descriptor = CodeGenHelper.getFieldDescriptor(type);
+
+            mv.visitFieldInsn(Opcodes.GETFIELD, thisClass, identifier, descriptor);
         } else
             throw new Exception("Variable " + identifier + " not found");
     }
 
-    //TODO move this to a helper class and remove the doubled code in MethodDecl and in other places
-    private String getFieldDescriptor(String type) {
-        switch (type) {
-            case "int":
-                return "I";
-            case "boolean":
-                return "Z";
-            case "char":
-                return "C";
-            default:
-                return "L" + type + ";";
-        }
-    }
-
     @Override
     public TypeCheckResult getTypeCheckResult() {
         return super.getTypeCheckResult();

src/main/java/abstractSyntaxTree/Expression/UnaryExpression.java

@@ -2,9 +2,7 @@ package abstractSyntaxTree.Expression;
 
 import TypeCheck.AbstractType;
 import TypeCheck.TypeCheckException;
-import TypeCheck.TypeCheckHelper;
 import TypeCheck.TypeCheckResult;
-import abstractSyntaxTree.Datatype.IDatatype;
 import abstractSyntaxTree.Parameter.ParameterList;
 import org.objectweb.asm.MethodVisitor;
 import org.objectweb.asm.Opcodes;

src/main/java/abstractSyntaxTree/Statement/IfElseStatement.java

@@ -54,9 +54,6 @@ public class IfElseStatement extends AbstractType implements IStatement{
     }
 
 
-    //TODO: There are 2 NOPs and one athrow on the stack between the if-Block and else-Block execution --> I have no idea why
-    // I think they are generated because of the jump operations below and can not be eliminated
-    // as they do not negatively impact the execution of the code logic wise we can ignore them
     @Override
     public void codeGen(MethodVisitor mv, LinkedHashMap<String, String> localVars, HashMap<String, HashMap<String, String>> typeContext, HashMap<String, HashMap<String, HashMap<String, ParameterList>>> methodContext) throws Exception {