Use native behavior for dead code elimination

pkg/compiler/lib/src/ssa/nodes.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of ssa;
 
 abstract class HVisitor<R> {
   R visitAdd(HAdd node);
   R visitAwait(HAwait node);
   R visitBitAnd(HBitAnd node);
@@ skipping 1732 matching lines @@
   HForeignCode.statement(js.Template codeTemplate, List<HInstruction> inputs,
       SideEffects effects,
       native.NativeBehavior nativeBehavior,
       TypeMask type)
       : this(codeTemplate, type, inputs, isStatement: true,
              effects: effects, nativeBehavior: nativeBehavior);
 
   accept(HVisitor visitor) => visitor.visitForeignCode(this);
 
   bool isJsStatement() => isStatement;
-  bool canThrow() => throwBehavior.canThrow;
+  bool canThrow() => canBeNull()
+      ? throwBehavior.canThrow
+      : throwBehavior.onNonNull.canThrow;
+
+  bool onlyThrowsNSM() => throwBehavior.onlyNullNSMGuard;
 }
 
 class HForeignNew extends HForeign {
   ClassElement element;
 
   /// If this field is not `null`, this call is from an inlined constructor and
   /// we have to register the instantiated type in the code generator. The
   /// [instructionType] of this node is not enough, because we also need the
   /// type arguments. See also [SsaFromAstMixin.currentInlinedInstantiations].
   List<DartType> instantiatedTypes;
@@ skipping 1394 matching lines @@
 class HDynamicType extends HRuntimeType {
   HDynamicType(DynamicType dartType, TypeMask instructionType)
       : super(const <HInstruction>[], dartType, instructionType);
 
   accept(HVisitor visitor) => visitor.visitDynamicType(this);
 
   int typeCode() => HInstruction.DYNAMIC_TYPE_TYPECODE;
 
   bool typeEquals(HInstruction other) => other is HDynamicType;
 }