correctly generate !=

idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java

@@ -107,6 +107,9 @@ public class ExpressionCodegen extends JetVisitor {
         gen(elseExpression, asmType);
 
         v.mark(endLabel);
+        if (asmType != Type.VOID_TYPE) {
+            myStack.push(StackValue.onStack(asmType));
+        }
     }
 
     @Override
@@ -141,7 +144,7 @@ public class ExpressionCodegen extends JetVisitor {
         gen(expression.getBody(), Type.VOID_TYPE);
 
         gen(expression.getCondition());
-        myStack.pop().condJump(condition, true, v);
+        myStack.pop().condJump(condition, false, v);
 
         v.mark(end);
 
@@ -477,7 +480,7 @@ public class ExpressionCodegen extends JetVisitor {
                         if (leftType == Type.INT_TYPE && rightType == Type.INT_TYPE) {
                             gen(expression.getLeft(), Type.INT_TYPE);
                             gen(expression.getRight(), Type.INT_TYPE);
-                            myStack.push(StackValue.icmp(JetTokens.EQEQ));
+                            myStack.push(StackValue.icmp(opToken));
                             return;
                         }
                         else {

idea/src/org/jetbrains/jet/codegen/StackValue.java

@@ -19,6 +19,7 @@ public abstract class StackValue {
     }
 
     public static StackValue onStack(Type type) {
+        assert type != Type.VOID_TYPE;
         return new OnStack(type);
     }
 
@@ -131,6 +132,9 @@ public abstract class StackValue {
             if (opToken == JetTokens.EQEQ) {
                 opcode = jumpIfFalse ? Opcodes.IF_ICMPNE : Opcodes.IF_ICMPEQ;
             }
+            else if (opToken == JetTokens.EXCLEQ) {
+                opcode = jumpIfFalse ? Opcodes.IF_ICMPEQ : Opcodes.IF_ICMPNE;
+            }
             else if (opToken == JetTokens.GT) {
                 opcode = jumpIfFalse ? Opcodes.IF_ICMPLE : Opcodes.IF_ICMPGT;
             }

idea/tests/org/jetbrains/jet/codegen/NamespaceGenTest.java

@@ -180,6 +180,11 @@ public class NamespaceGenTest extends LightCodeInsightFixtureTestCase {
         binOpTest("fun foo(a: Int, b: Int): Int = a % b", 14, 3, 2);
     }
 
+    public void testNE() throws Exception {
+        binOpTest("fun foo(a: Int, b: Int): Int = if (a != b) 1 else 0", 5, 5, 0);
+        binOpTest("fun foo(a: Int, b: Int): Int = if (a != b) 1 else 0", 5, 3, 1);
+    }
+
     public void testIfNoElse() throws Exception {
         loadFile("ifNoElse.jet");
         System.out.println(generateToText());