better handling of empty if/else blocks

compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java

@@ -155,6 +155,19 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
         return genQualified(receiver, expression.getBaseExpression());
     }
 
+    private static boolean isEmptyExpression(JetElement expr) {
+        if(expr == null)
+            return true;
+        if(expr instanceof JetBlockExpression) {
+            JetBlockExpression blockExpression = (JetBlockExpression) expr;
+            List<JetElement> statements = blockExpression.getStatements();
+            if(statements.size() == 0 || statements.size() == 1 && isEmptyExpression(statements.get(0))) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     @Override
     public StackValue visitIfExpression(JetIfExpression expression, StackValue receiver) {
         Type asmType = expressionType(expression);
@@ -167,27 +180,36 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
             throw new CompilationException();
         }
 
-        if (thenExpression == null) {
+        if (isEmptyExpression(thenExpression)) {
+            if (isEmptyExpression(elseExpression)) {
+                condition.put(asmType, v);
+                return StackValue.onStack(asmType);
+            }
             return generateSingleBranchIf(condition, elseExpression, false);
         }
-
+        else {
-        if (elseExpression == null) {
+            if (isEmptyExpression(elseExpression)) {
-            return generateSingleBranchIf(condition, thenExpression, true);
+                return generateSingleBranchIf(condition, thenExpression, true);
+            }
         }
 
 
         Label elseLabel = new Label();
         condition.condJump(elseLabel, true, v);   // == 0, i.e. false
 
+        Label end = continueLabel == null ? new Label() : continueLabel;
+
         gen(thenExpression, asmType);
 
-        Label endLabel = new Label();
+        v.goTo(end);
-        v.goTo(endLabel);
         v.mark(elseLabel);
 
         gen(elseExpression, asmType);
 
-        v.mark(endLabel);
+        if(end != continueLabel)
+            v.mark(end);
+        else
+            v.goTo(end);
 
         return StackValue.onStack(asmType);
     }
@@ -198,16 +220,21 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
         myContinueTargets.push(condition);
         v.mark(condition);
 
-        Label end = new Label();
+        Label end = continueLabel != null ? continueLabel : new Label();
         myBreakTargets.push(end);
 
+        Label savedContinueLabel = continueLabel;
+        continueLabel = condition;
+
         final StackValue conditionValue = gen(expression.getCondition());
         conditionValue.condJump(end, true, v);
 
         gen(expression.getBody(), Type.VOID_TYPE);
         v.goTo(condition);
 
-        v.mark(end);
+        continueLabel = savedContinueLabel;
+        if(end != continueLabel)
+            v.mark(end);
         myBreakTargets.pop();
         myContinueTargets.pop();
 
@@ -519,13 +546,14 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
     }
 
     private StackValue generateSingleBranchIf(StackValue condition, JetExpression expression, boolean inverse) {
-        Label endLabel = new Label();
+        Label end = continueLabel != null ? continueLabel : new Label();
 
-        condition.condJump(endLabel, inverse, v);
+        condition.condJump(end, inverse, v);
 
         gen(expression, Type.VOID_TYPE);
 
-        v.mark(endLabel);
+        if(continueLabel != end)
+            v.mark(end);
         return StackValue.none();
     }
 
@@ -655,6 +683,8 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
         return StackValue.onStack(Type.getObjectType(closure.getClassname()));
     }
 
+    private Label continueLabel;
+    
     private StackValue generateBlock(List<JetElement> statements) {
         Label blockStart = new Label();
         v.mark(blockStart);
@@ -671,9 +701,12 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
         }
 
         StackValue answer = StackValue.none();
+        Label savedContinueLabel = continueLabel;
+        continueLabel = null;
         for (int i = 0, statementsSize = statements.size(); i < statementsSize; i++) {
             JetElement statement = statements.get(i);
             if (i == statements.size() - 1 /*&& statement instanceof JetExpression && !bindingContext.get(BindingContext.STATEMENT, statement)*/) {
+                continueLabel = savedContinueLabel;
                 answer = gen(statement);
             }
             else {

compiler/testData/codegen/controlStructures/quicksort.jet

@@ -0,0 +1,42 @@
+fun IntArray.swap(i:Int, j:Int) {
+    val temp = this[i]
+    this[i] = this[j]
+    this[j] = temp
+}
+
+fun IntArray.quicksort() = quicksort(0, size-1)
+
+fun IntArray.quicksort(L: Int, R:Int) {
+    val m = this[(L + R) / 2]
+    var i = L
+    var j = R
+    while (i <= j) {
+        while (this[i] < m)
+            i++
+        while (this[j] > m)
+            j--
+        if (i <= j) {
+            swap(i++, j--)
+        }
+        else {
+        }
+    }
+    if (L < j)
+        quicksort(L, j)
+    if (R > i)
+        quicksort(i, R)
+}
+
+fun box() : String {
+    val a = IntArray(10)
+    for(i in 0..4) {
+        a[2*i]   =  2*i
+        a[2*i+1] = -2*i-1
+    }
+    a.quicksort()
+    for(i in 0..9) {
+        System.out?.print(a[i])
+        System.out?.print(' ')
+    }
+    return "OK"
+}

compiler/testData/codegen/regressions/kt239.jet

@@ -1,3 +1,5 @@
-fun box(i: Int?) {
+fun box() : String {
+    val i : Int? = 0
     val j = i?.plus(3) //verify error
+    return "OK"
 }

compiler/tests/org/jetbrains/jet/codegen/ControlStructuresTest.java

@@ -220,4 +220,9 @@ public class ControlStructuresTest extends CodegenTestCase {
         createEnvironmentWithFullJdk();
         blackBoxFile("regressions/kt434.jet");
     }
+
+    public void testQuicksort() throws Exception {
+        blackBoxFile("controlStructures/quicksort.jet");
+//        System.out.println(generateToText());
+    }
 }

compiler/tests/org/jetbrains/jet/codegen/PrimitiveTypesTest.java

@@ -266,7 +266,7 @@ public class PrimitiveTypesTest extends CodegenTestCase {
     }
 
     public void testKt239 () throws Exception {
-        blackBoxFile("regressions/kt242.jet");
+        blackBoxFile("regressions/kt239.jet");
     }
 
     public void testKt243 () throws Exception {

examples/src/benchmarks/Quicksort.java

@@ -30,6 +30,8 @@ public class Quicksort {
     }
 
     public static void main(String[] args) {
+        long start = System.currentTimeMillis();
+
         // Sample data
         int[] a = new int[100000000];
         for (int i = 0; i < a.length; i++) {
@@ -38,8 +40,6 @@ public class Quicksort {
                 a[i] = -a[i];
         }
 
-        long start = System.currentTimeMillis();
-
         quicksort(a);
 
         long total = System.currentTimeMillis() - start;

examples/src/benchmarks/Quicksort.kt

@@ -17,7 +17,7 @@ fun IntArray.quicksort(L: Int, R:Int) {
             i++
         while (this[j] > m)
             j--
-        if (i <= j) { KT-5
+        if (i <= j) {
             swap(i++, j--)
         }
     }
@@ -28,6 +28,8 @@ fun IntArray.quicksort(L: Int, R:Int) {
 }
 
 fun main(array: Array<String>) {
+    val start = System.currentTimeMillis()
+
     val a = IntArray(100000000)
     var i = 0
     val len = a.size
@@ -38,8 +40,6 @@ fun main(array: Array<String>) {
         i++
     }
 
-    val start = System.currentTimeMillis()
-
     a.quicksort()
 
     val total = System.currentTimeMillis() - start