Add a function to compute loop nesting level to HBasicBlock.

src/hydrogen.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 202 matching lines @@
 bool HBasicBlock::Dominates(HBasicBlock* other) const {
   HBasicBlock* current = other->dominator();
   while (current != NULL) {
     if (current == this) return true;
     current = current->dominator();
   }
   return false;
 }
 
 
+int HBasicBlock::LoopNestingDepth() const {
+  const HBasicBlock* current = this;
+  int result  = (current->IsLoopHeader()) ? 1 : 0;
+  while (current->parent_loop_header() != NULL) {
+    current = current->parent_loop_header();
+    result++;
+  }
+  return result;
+}
+
+
 void HBasicBlock::PostProcessLoopHeader(IterationStatement* stmt) {
   ASSERT(IsLoopHeader());
 
   SetJoinId(stmt->EntryId());
   if (predecessors()->length() == 1) {
     // This is a degenerated loop.
     DetachLoopInformation();
     return;
   }
 
@@ skipping 6327 matching lines @@
       trace_.Add("\n");
     }
 
     PrintEmptyProperty("xhandlers");
     PrintEmptyProperty("flags");
 
     if (current->dominator() != NULL) {
       PrintBlockProperty("dominator", current->dominator()->block_id());
     }
 
+    PrintIntProperty("loop_depth", current->LoopNestingDepth());
+
     if (chunk != NULL) {
       int first_index = current->first_instruction_index();
       int last_index = current->last_instruction_index();
       PrintIntProperty(
           "first_lir_id",
           LifetimePosition::FromInstructionIndex(first_index).Value());
       PrintIntProperty(
           "last_lir_id",
           LifetimePosition::FromInstructionIndex(last_index).Value());
     }
@@ skipping 230 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify();
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal