Добавлена оптимизация: упрощение выражений

Author: aNNiMON

src/com/annimon/ownlang/parser/Optimizer.java

@@ -3,6 +3,7 @@
 import com.annimon.ownlang.parser.ast.Statement;
 import com.annimon.ownlang.parser.visitors.ConstantFolding;
 import com.annimon.ownlang.parser.visitors.DeadCodeElimination;
+import com.annimon.ownlang.parser.visitors.ExpressionSimplification;
 
 public final class Optimizer {
 
@@ -18,14 +19,17 @@ public static Statement optimize(Statement statement, int level) {
 
         final ConstantFolding constantFolding = new ConstantFolding();
         final DeadCodeElimination deadCodeElimination = new DeadCodeElimination();
+        final ExpressionSimplification expressionSimplification = new ExpressionSimplification();
 
         Statement result = statement;
         for (int i = 0; i < level; i++) {
             result = (Statement) result.accept(constantFolding, null);
             result = (Statement) result.accept(deadCodeElimination, null);
+            result = (Statement) result.accept(expressionSimplification, null);
         }
         System.out.print(constantFolding.summaryInfo());
         System.out.print(deadCodeElimination.summaryInfo());
+        System.out.print(expressionSimplification.summaryInfo());
         System.out.println();
         return result;
     }

src/com/annimon/ownlang/parser/visitors/ExpressionSimplification.java

@@ -0,0 +1,146 @@
+package com.annimon.ownlang.parser.visitors;
+
+import com.annimon.ownlang.lib.NumberValue;
+import com.annimon.ownlang.lib.Types;
+import com.annimon.ownlang.lib.Value;
+import com.annimon.ownlang.parser.Optimizer;
+import com.annimon.ownlang.parser.ast.BinaryExpression;
+import com.annimon.ownlang.parser.ast.ConditionalExpression;
+import com.annimon.ownlang.parser.ast.Node;
+import com.annimon.ownlang.parser.ast.UnaryExpression;
+import com.annimon.ownlang.parser.ast.ValueExpression;
+import com.annimon.ownlang.parser.ast.VariableExpression;
+
+/**
+ * Performs expression simplification.
+ */
+public class ExpressionSimplification extends OptimizationVisitor<Void> implements Optimizer.Info {
+
+    private int simplificationsCount;
+
+    public ExpressionSimplification() {
+        simplificationsCount = 0;
+    }
+
+    @Override
+    public int optimizationsCount() {
+        return simplificationsCount;
+    }
+
+    @Override
+    public String summaryInfo() {
+        if (optimizationsCount() == 0) return "";
+        final StringBuilder sb = new StringBuilder();
+        if (simplificationsCount > 0) {
+            sb.append("\nExpression simplifications: ").append(simplificationsCount);
+        }
+        return sb.toString();
+    }
+
+    @Override
+    public Node visit(BinaryExpression s, Void t) {
+        // operations with 0
+        final boolean expr1IsZero = isIntegerValue(s.expr1, 0);
+        if (expr1IsZero || isIntegerValue(s.expr2, 0)) {
+            switch (s.operation) {
+                case ADD:
+                    //  0 + x2 to x2, x1 + 0 to x1
+                    simplificationsCount++;
+                    return expr1IsZero ? s.expr2 : s.expr1;
+
+                case SUBTRACT:
+                    simplificationsCount++;
+                    if (expr1IsZero) {
+                        // 0 - x2 to -x2
+                        return new UnaryExpression(UnaryExpression.Operator.NEGATE, s.expr2);
+                    }
+                    // x1 - 0 to x1
+                    return s.expr1;
+
+                case MULTIPLY:
+                    // 0 * x2 to 0, x1 * 0 to 0
+                    simplificationsCount++;
+                    return new ValueExpression(0);
+
+                case DIVIDE:
+                    // 0 / x2 to 0
+                    if (expr1IsZero) {
+                        simplificationsCount++;
+                        return new ValueExpression(0);
+                    }
+                    break;
+            }
+        }
+
+        // operations with 1
+        final boolean expr1IsOne = isIntegerValue(s.expr1, 1);
+        if (expr1IsOne || isIntegerValue(s.expr2, 1)) {
+            switch (s.operation) {
+                case MULTIPLY:
+                    // 1 * x2 to x2, x1 * 1 to x1
+                    simplificationsCount++;
+                    return expr1IsOne ? s.expr2 : s.expr1;
+
+                case DIVIDE:
+                    // x1 / 1 to x1
+                    if (!expr1IsOne) {
+                        simplificationsCount++;
+                        return s.expr1;
+                    }
+                    break;
+            }
+        }
+
+        // x1 / -1 to -x1
+        if (isIntegerValue(s.expr2, -1)) {
+            simplificationsCount++;
+            return new UnaryExpression(UnaryExpression.Operator.NEGATE, s.expr1);
+        }
+
+        // x - x to 0
+        if (isSameVariables(s.expr1, s.expr2) && s.operation == BinaryExpression.Operator.SUBTRACT) {
+            simplificationsCount++;
+            return new ValueExpression(0);
+        }
+
+        return super.visit(s, t);
+    }
+
+    @Override
+    public Node visit(ConditionalExpression s, Void t) {
+        if (isIntegerValue(s.expr1, 0) && s.operation == ConditionalExpression.Operator.AND) {
+            // 0 && x2 to 0
+            simplificationsCount++;
+            return new ValueExpression(0);
+        }
+        if (isIntegerValue(s.expr1, 1) && s.operation == ConditionalExpression.Operator.OR) {
+            // 1 || x2 to 1
+            simplificationsCount++;
+            return new ValueExpression(1);
+        }
+        return super.visit(s, t);
+    }
+
+
+    private boolean isIntegerValue(Node node, int valueToCheck) {
+        if (!(node instanceof ValueExpression)) return false;
+
+        final Value value = ((ValueExpression) node).value;
+        if (value.type() != Types.NUMBER) return false;
+
+        final Number number = ((NumberValue) value).raw();
+        if ( (number instanceof Integer) || (number instanceof Short) || (number instanceof Byte)) {
+            return number.intValue() == valueToCheck;
+        }
+        return false;
+    }
+
+    private boolean isSameVariables(Node n1, Node n2) {
+        if ( (n1 instanceof VariableExpression) && (n2 instanceof VariableExpression) ) {
+            final VariableExpression v1 = (VariableExpression) n1;
+            final VariableExpression v2 = (VariableExpression) n2;
+            return v1.name.equals(v2.name);
+        }
+        return false;
+    }
+}