TEST: Tests for "null" constant added

backend.native/tests/build.gradle

@@ -256,10 +256,15 @@ task local_variable(type: UnitKonanTest) {
     source = "codegen/basics/local_variable.kt"
 }
 
+
 task cast_simple(type: UnitKonanTest) {
     source = "codegen/basics/cast_simple.kt"
 }
 
+task null_check(type: UnitKonanTest) {
+    source = "codegen/basics/null_check.kt"
+}
+
 task hello0(type: RunKonanTest) {
     goldValue = "Hello, world!\n"
     source = "runtime/basic/hello0.kt"

backend.native/tests/codegen/basics/null_check-test.c

@@ -0,0 +1,19 @@
+#include <stdint.h>
+#include <stdio.h>
+
+extern void *resolve_symbol(const char*);
+
+int
+run_test() {
+  uint8_t (*null_check_eqeq1  )() = resolve_symbol("kfun:null_check_eqeq1()");
+  uint8_t (*null_check_eqeq2  )() = resolve_symbol("kfun:null_check_eqeq2()");
+  uint8_t (*null_check_eqeqeq1)() = resolve_symbol("kfun:null_check_eqeqeq1()");
+  uint8_t (*null_check_eqeqeq2)() = resolve_symbol("kfun:null_check_eqeqeq2()");
+
+  if (null_check_eqeq1())    return 1;
+  if (!null_check_eqeq2())   return 1;
+  if (null_check_eqeqeq1())  return 1;
+  if (!null_check_eqeqeq2()) return 1;
+
+  return 0;
+}

backend.native/tests/codegen/basics/null_check.kt

@@ -0,0 +1,23 @@
+//--- Test "eqeq" -------------------------------------------------------------//
+
+fun check_eqeq(a: Any?) = a == null
+
+fun null_check_eqeq1() : Boolean {
+  return check_eqeq(Any())
+}
+
+fun null_check_eqeq2() : Boolean {
+  return check_eqeq(null)
+}
+
+//--- Test "eqeqeq" -----------------------------------------------------------//
+
+fun check_eqeqeq(a: Any?) = a === null
+
+fun null_check_eqeqeq1() : Boolean {
+  return check_eqeqeq(Any())
+}
+
+fun null_check_eqeqeq2() : Boolean {
+  return check_eqeqeq(null)
+}