Do not compare boxed values with 0 via IFEQ/IFNE

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

@@ -2362,11 +2362,11 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> implem
             return genCmpWithNull(left, leftType, opToken);
         }
 
-        if (isIntZero(left, leftType)) {
+        if (isIntZero(left, leftType) && isIntPrimitive(rightType)) {
             return genCmpWithZero(right, rightType, opToken);
         }
 
-        if (isIntZero(right, rightType)) {
+        if (isIntZero(right, rightType) && isIntPrimitive(leftType)) {
             return genCmpWithZero(left, leftType, opToken);
         }
 

compiler/testData/codegen/controlStructures/compareBoxedIntegerToZero.kt

@@ -0,0 +1,8 @@
+fun box(): String {
+    val x: Int? = 0
+    if (x != 0) return "Fail $x"
+    if (0 != x) return "Fail $x"
+    if (!(x == 0)) return "Fail $x"
+    if (!(0 == x)) return "Fail $x"
+    return "OK"
+}

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

@@ -250,6 +250,11 @@ public class ControlStructuresTest extends CodegenTestCase {
         assertEquals(false, main.invoke(null, 1, 0));
     }
 
+    public void testCompareBoxedIntegerToZero() {
+        createEnvironmentWithMockJdkAndIdeaAnnotations(ConfigurationKind.JDK_ONLY);
+        blackBoxFile("controlStructures/compareBoxedIntegerToZero.kt");
+    }
+
     public void testCompareToNull() throws Exception {
         createEnvironmentWithMockJdkAndIdeaAnnotations(ConfigurationKind.JDK_ONLY);
         loadText("fun foo(a: String?, b: String?): Boolean = a == null && b !== null && null == a && null !== b");