Abcd for performance check.

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index a2ddc04b9174f2ec7b95f68acd3acd199ee0a848..3cc8ade284e4a029d399529198fdf9f2b38c8f87 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -437,6 +437,28 @@ void HLoopInformation::RegisterBackEdge(HBasicBlock* block) {
 }
 
 
+void HLoopInformation::ProcessEdge(HBasicBlock* destination) {
+  HLoopInformation* target_loop = destination->current_loop();
+  if (IsInThisLoop(target_loop)) return;
+
+  HLoopInformation* current_loop = this;
+  while (current_loop != NULL) {
+    if (target_loop == current_loop) return;
+    current_loop->exits_count_++;
+    current_loop = current_loop->parent_loop();
+  }
+}
+
+
+void HLoopInformation::ProcessThrow() {
+  HLoopInformation* current_loop = this;
+  while (current_loop != NULL) {

[Jakob Kummerow, 2013/04/17 11:34:15]

Please add a comment saying that when we support try..catch in crankshaft, we
need another condition here: break the while-loop when encountering the catch
block. From a correctness PoV we're safe anyway, but unnecessarily marking loops
as having additional exits could prevent BCE.

[Massi, 2013/05/07 11:32:03]

Done.

+    current_loop->exits_count_++;
+    current_loop = current_loop->parent_loop();
+  }
+}
+
+
 HBasicBlock* HLoopInformation::GetLastBackEdge() const {
   int max_id = -1;
   HBasicBlock* result = NULL;
@@ -2017,6 +2039,14 @@ void HGraph::OrderBlocks() {
     HBasicBlock* b = reverse_result[i];
     blocks_.Add(b, zone());
     b->set_block_id(index++);
+
+    HLoopInformation* loop = b->current_loop();
+    if (loop != NULL) {
+      for (int i = 0; i < b->end()->SuccessorCount(); i++) {
+        HBasicBlock* successor = b->end()->SuccessorAt(i);
+        loop->ProcessEdge(successor);
+      }
+    }
   }
 }
 
@@ -3413,6 +3443,12 @@ void HInferRepresentation::Analyze() {
           current->CheckFlag(HInstruction::kFlexibleRepresentation)) {
         current->ChangeRepresentation(Representation::Tagged());
       }
+
+      if (current->IsThrow()) {

[Jakob Kummerow, 2013/04/17 11:34:15]

Let's move this into the block ordering phase where ProcessEdge is called too.

[Massi, 2013/05/07 11:32:03]

Done.

+        if (block->current_loop() != NULL) {
+          block->current_loop()->ProcessThrow();
+        }
+      }
     }
   }
 }