[turbofan] Do not set node's mark to min on get

src/compiler/node-marker.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_COMPILER_NODE_MARKER_H_
 #define V8_COMPILER_NODE_MARKER_H_
 
 #include "src/compiler/node.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 // Forward declarations.
 class Graph;
 
 
 // Base class for templatized NodeMarkers.
 class NodeMarkerBase {
  public:
   NodeMarkerBase(Graph* graph, uint32_t num_states);
 
-  V8_INLINE Mark Get(Node* node) {
+  V8_INLINE Mark Get(const Node* node) {
     Mark mark = node->mark();
     if (mark < mark_min_) {
-      mark = mark_min_;
-      node->set_mark(mark_min_);
+      return 0;
     }
     DCHECK_LT(mark, mark_max_);
     return mark - mark_min_;
   }
   V8_INLINE void Set(Node* node, Mark mark) {
     DCHECK_LT(mark, mark_max_ - mark_min_);
     DCHECK_LT(node->mark(), mark_max_);
     node->set_mark(mark + mark_min_);
   }
 
  private:
   Mark const mark_min_;
   Mark const mark_max_;
 
   DISALLOW_COPY_AND_ASSIGN(NodeMarkerBase);
 };
 
 // A NodeMarker assigns a local "state" to every node of a graph in constant
 // memory. Only one NodeMarker per graph is valid at a given time, that is,
 // after you create a NodeMarker you should no longer use NodeMarkers that
 // were created earlier. Internally, the local state is stored in the Node
 // structure.
 //
 // When you initialize a NodeMarker, all the local states are conceptually
 // set to State(0) in constant time.
 //
 // In its current implementation, in debug mode NodeMarker will try to
-// (efficiently) detect invalid use of an older NodeMarker. Namely, if you get
-// or set a node with a NodeMarker, and then get or set that node
-// with an older NodeMarker you will get a crash.
+// (efficiently) detect invalid use of an older NodeMarker. Namely, if you set a
+// node with a NodeMarker, and then get or set that node with an older
+// NodeMarker you will get a crash.
 //
 // GraphReducer uses a NodeMarker, so individual Reducers cannot use a
 // NodeMarker.
 template <typename State>
 class NodeMarker : public NodeMarkerBase {
  public:
   V8_INLINE NodeMarker(Graph* graph, uint32_t num_states)
       : NodeMarkerBase(graph, num_states) {}
 
-  V8_INLINE State Get(Node* node) {
+  V8_INLINE State Get(const Node* node) {
     return static_cast<State>(NodeMarkerBase::Get(node));
   }
 
   V8_INLINE void Set(Node* node, State state) {
     NodeMarkerBase::Set(node, static_cast<Mark>(state));
   }
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_NODE_MARKER_H_