CODEGEN: support for instanceof for null implemented

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/IrToBitcode.kt

@@ -645,6 +645,7 @@ internal class CodeGeneratorVisitor(val context: Context) : IrElementVisitorVoid
 
         return valuePhi
     }
+
     //-------------------------------------------------------------------------//
 
     private fun evaluateExpressionAndJump(expression: IrExpression, destination: ContinuationBlock) {
@@ -1242,9 +1243,29 @@ internal class CodeGeneratorVisitor(val context: Context) : IrElementVisitorVoid
         val type     = value.typeOperand
         val srcArg   = evaluateExpression(codegen.newVar(), value.argument)!!     // Evaluate src expression.
 
-        return genInstanceOf(tmpVariableName, srcArg, type)
+        val bbNull       = codegen.basicBlock()
+        val bbInstanceOf = codegen.basicBlock()
+        val bbExit       = codegen.basicBlock()
+
+        val condition = codegen.icmpEq(srcArg, codegen.kNullObjHeaderPtr, codegen.newVar())
+        codegen.condBr(condition, bbNull, bbInstanceOf)
+
+        codegen.positionAtEnd(bbNull)
+        val resultNull = if (TypeUtils.isNullableType(type)) kTrue else kFalse
+        codegen.br(bbExit)
+
+        codegen.positionAtEnd(bbInstanceOf)
+        val resultInstanceOf = genInstanceOf(tmpVariableName, srcArg, type)
+        codegen.br(bbExit)
+
+        codegen.positionAtEnd(bbExit)
+        val result = codegen.phi(kBoolean, codegen.newVar())
+        codegen.addPhiIncoming(result, bbNull to resultNull, bbInstanceOf to resultInstanceOf)
+        return result
     }
 
+    //-------------------------------------------------------------------------//
+
     private fun genInstanceOf(tmpVariableName: String, obj: LLVMValueRef, type: KotlinType): LLVMValueRef {
         val dstDescriptor = TypeUtils.getClassDescriptor(type)                         // Get class descriptor for dst type.
         val dstTypeInfo   = codegen.typeInfoValue(dstDescriptor!!)                     // Get TypeInfo for dst type.

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/LlvmUtils.kt

@@ -115,6 +115,7 @@ internal val ContextUtils.kObjHeaderPtrPtr: LLVMTypeRef
 internal val ContextUtils.kTypeInfoPtr: LLVMTypeRef
     get() = pointerType(kTypeInfo)
 internal val kInt1         = LLVMInt1Type()!!
+internal val kBoolean      = kInt1
 internal val kInt8Ptr      = pointerType(int8Type)
 internal val kInt8PtrPtr   = pointerType(kInt8Ptr)
 internal val kImmInt32One  = Int32(1).llvm