[turbofan] Jump threading awareness of frame elision.

src/compiler/jump-threading.h

Index: src/compiler/jump-threading.h
diff --git a/src/compiler/jump-threading.h b/src/compiler/jump-threading.h
index fa74ee9a5202abf8bfc0b88bedc01754f1efd56e..84520ba3ed2f26c5ca46fce0676b5fcf9d25f285 100644
--- a/src/compiler/jump-threading.h
+++ b/src/compiler/jump-threading.h
@@ -18,7 +18,7 @@ class JumpThreading {
   // Compute the forwarding map of basic blocks to their ultimate destination.
   // Returns {true} if there is at least one block that is forwarded.
   static bool ComputeForwarding(Zone* local_zone, ZoneVector<RpoNumber>& result,
-                                InstructionSequence* code);
+                                InstructionSequence* code, bool frame_at_start);

[Jarin, 2016/01/28 05:26:58]

Please explain what the {frame_at_start} parameter means in the comment above.

 
   // Rewrite the instructions to forward jumps and branches.
   // May also negate some branches.