[turbofan] Keep AstGraphBuilder context chain length in sync.

src/compiler/ast-graph-builder.h

 // Copyright 2014 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_AST_GRAPH_BUILDER_H_
 #define V8_COMPILER_AST_GRAPH_BUILDER_H_
 
 #include "src/ast.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/liveness-analyzer.h"
@@ skipping 366 matching lines @@
 // values are stored in one list using the following layout:
 //
 //  [parameters (+receiver)] [locals] [operand stack]
 //
 class AstGraphBuilder::Environment : public ZoneObject {
  public:
   Environment(AstGraphBuilder* builder, Scope* scope, Node* control_dependency);
 
   int parameters_count() const { return parameters_count_; }
   int locals_count() const { return locals_count_; }
+  int context_chain_length() { return static_cast<int>(contexts_.size()); }
   int stack_height() {
     return static_cast<int>(values()->size()) - parameters_count_ -
            locals_count_;
   }
 
   // Operations on parameter or local variables.
   void Bind(Variable* variable, Node* node);
   Node* Lookup(Variable* variable);
   void MarkAllLocalsLive();
 
+  // Operations on the context chain.
   Node* Context() const { return contexts_.back(); }
   void PushContext(Node* context) { contexts()->push_back(context); }
   void PopContext() { contexts()->pop_back(); }
+  void TrimContextChain(int trim_to_length) {
+    contexts()->resize(trim_to_length);
+  }
 
   // Operations on the operand stack.
   void Push(Node* node) {
     values()->push_back(node);
   }
   Node* Top() {
     DCHECK(stack_height() > 0);
     return values()->back();
   }
   Node* Pop() {
@@ skipping 11 matching lines @@
   }
   Node* Peek(int depth) {
     DCHECK(depth >= 0 && depth < stack_height());
     int index = static_cast<int>(values()->size()) - depth - 1;
     return values()->at(index);
   }
   void Drop(int depth) {
     DCHECK(depth >= 0 && depth <= stack_height());
     values()->erase(values()->end() - depth, values()->end());
   }
-  void Trim(int trim_to_height) {
+  void TrimStack(int trim_to_height) {
     int depth = stack_height() - trim_to_height;
     DCHECK(depth >= 0 && depth <= stack_height());
     values()->erase(values()->end() - depth, values()->end());
   }
 
   // Preserve a checkpoint of the environment for the IR graph. Any
   // further mutation of the environment will not affect checkpoints.
   Node* Checkpoint(BailoutId ast_id, OutputFrameStateCombine combine =
                                          OutputFrameStateCombine::Ignore());
 
@@ skipping 29 matching lines @@
     env->MarkAsUnreachable();
     return env;
   }
 
   // Copies this environment at a loop header control-flow point.
   Environment* CopyForLoop(BitVector* assigned, bool is_osr = false) {
     PrepareForLoop(assigned, is_osr);
     return CopyAndShareLiveness();
   }
 
-  int ContextStackDepth() { return static_cast<int>(contexts_.size()); }
-
  private:
   AstGraphBuilder* builder_;
   int parameters_count_;
   int locals_count_;
   LivenessAnalyzerBlock* liveness_block_;
   NodeVector values_;
   NodeVector contexts_;
   Node* control_dependency_;
   Node* effect_dependency_;
   Node* parameters_node_;
@@ skipping 15 matching lines @@
 
   // Prepare environment to be used as loop header.
   void PrepareForLoop(BitVector* assigned, bool is_osr = false);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_AST_GRAPH_BUILDER_H_