Simplify computation of environment stack delta.

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"
 
@@ skipping 272 matching lines @@
   // Visit expressions.
   void Visit(Expression* expr);
   void VisitForTest(Expression* expr);
   void VisitForEffect(Expression* expr);
   void VisitForValue(Expression* expr);
   void VisitForValueOrNull(Expression* expr);
   void VisitForValueOrTheHole(Expression* expr);
   void VisitForValues(ZoneList<Expression*>* exprs);
 
   // Common for all IterationStatement bodies.
-  void VisitIterationBody(IterationStatement* stmt, LoopBuilder* loop, int);
+  void VisitIterationBody(IterationStatement* stmt, LoopBuilder* loop);
 
   // Dispatched from VisitCallRuntime.
   void VisitCallJSRuntime(CallRuntime* expr);
 
   // Dispatched from VisitUnaryOperation.
   void VisitDelete(UnaryOperation* expr);
   void VisitVoid(UnaryOperation* expr);
   void VisitTypeof(UnaryOperation* expr);
   void VisitNot(UnaryOperation* expr);
 
@@ skipping 89 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) {
+    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);
 
   // Control dependency tracked by this environment.
   Node* GetControlDependency() { return control_dependency_; }
   void UpdateControlDependency(Node* dependency) {
     control_dependency_ = dependency;
   }
@@ skipping 57 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_