[turbofan] Use bounds checks to eliminate subsequent inc/dec overflow checks.

src/compiler/redundancy-elimination.h

 // Copyright 2016 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_REDUNDANCY_ELIMINATION_H_
 #define V8_COMPILER_REDUNDANCY_ELIMINATION_H_
 
 #include "src/compiler/graph-reducer.h"
 
 namespace v8 {
@@ skipping 16 matching lines @@
 
   class EffectPathChecks final {
    public:
     static EffectPathChecks* Copy(Zone* zone, EffectPathChecks const* checks);
     static EffectPathChecks const* Empty(Zone* zone);
     bool Equals(EffectPathChecks const* that) const;
     void Merge(EffectPathChecks const* that);
 
     EffectPathChecks const* AddCheck(Zone* zone, Node* node) const;
     Node* LookupCheck(Node* node) const;
+    Node* LookupBoundsCheckFor(Node* node) const;
 
    private:
     EffectPathChecks(Check* head, size_t size) : head_(head), size_(size) {}
 
     // We keep track of the list length so that we can find the longest
     // common tail easily.
     Check* head_;
     size_t size_;
   };
 
   class PathChecksForEffectNodes final {
    public:
     explicit PathChecksForEffectNodes(Zone* zone) : info_for_node_(zone) {}
     EffectPathChecks const* Get(Node* node) const;
     void Set(Node* node, EffectPathChecks const* checks);
 
    private:
     ZoneVector<EffectPathChecks const*> info_for_node_;
   };
 
   Reduction ReduceCheckNode(Node* node);
   Reduction ReduceEffectPhi(Node* node);
   Reduction ReduceStart(Node* node);
   Reduction ReduceOtherNode(Node* node);
 
   Reduction TakeChecksFromFirstEffect(Node* node);
   Reduction UpdateChecks(Node* node, EffectPathChecks const* checks);
 
+  Reduction TryReuseBoundsCheckForFirstInput(Node* node);
+
   Zone* zone() const { return zone_; }
 
   PathChecksForEffectNodes node_checks_;
   Zone* const zone_;
 
   DISALLOW_COPY_AND_ASSIGN(RedundancyElimination);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_REDUNDANCY_ELIMINATION_H_