[turbofan] Limit use of FrameStateBeforeAndAfter helper.

This limits the use of the aforementioned helper class to only binary
and compare operations. These are the only operatins left that require
two frame state inputs on the same node.

R=jarin@chromium.org
BUG=v8:5021

Review-Url: https://codereview.chromium.org/2050673002
Cr-Commit-Position: refs/heads/master@{#36832}

src/compiler/ast-graph-builder.h

@@ -231,11 +231,18 @@ class AstGraphBuilder : public AstVisitor {
   // Helper to indicate a node exits the function body.
   void UpdateControlDependencyToLeaveFunction(Node* exit);
 
-  // Builds deoptimization for a given node.
+  // Prepare information for lazy deoptimization. This information is attached
+  // to the given node and the output value produced by the node is combined.
+  // Conceptually this frame state is "after" a given operation.
   void PrepareFrameState(Node* node, BailoutId ast_id,
                          OutputFrameStateCombine framestate_combine =
                              OutputFrameStateCombine::Ignore());
 
+  // Prepare information for eager deoptimization. This information is carried
+  // by dedicated {Checkpoint} nodes that are wired into the effect chain.
+  // Conceptually this frame state is "before" a given operation.
+  void PrepareEagerCheckpoint(BailoutId ast_id);
+
   BitVector* GetVariablesAssignedInLoop(IterationStatement* stmt);
 
   // Check if the given statement is an OSR entry.