1 files changed, 55 insertions, 0 deletions
diff --git a/deps/v8/src/crankshaft/hydrogen-mark-unreachable.cc b/deps/v8/src/crankshaft/hydrogen-mark-unreachable.cc
new file mode 100644
index 0000000000..4e1dd689ee
--- /dev/null
+++ b/deps/v8/src/crankshaft/hydrogen-mark-unreachable.cc
@@ -0,0 +1,55 @@
+// Copyright 2013 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.
+
+#include "src/crankshaft/hydrogen-mark-unreachable.h"
+
+namespace v8 {
+namespace internal {
+
+
+void HMarkUnreachableBlocksPhase::MarkUnreachableBlocks() {
+  // If there is unreachable code in the graph, propagate the unreachable marks
+  // using a fixed-point iteration.
+  bool changed = true;
+  const ZoneList<HBasicBlock*>* blocks = graph()->blocks();
+  while (changed) {
+    changed = false;
+    for (int i = 0; i < blocks->length(); i++) {
+      HBasicBlock* block = blocks->at(i);
+      if (!block->IsReachable()) continue;
+      bool is_reachable = blocks->at(0) == block;
+      for (HPredecessorIterator it(block); !it.Done(); it.Advance()) {
+        HBasicBlock* predecessor = it.Current();
+        // A block is reachable if one of its predecessors is reachable,
+        // doesn't deoptimize and either is known to transfer control to the
+        // block or has a control flow instruction for which the next block
+        // cannot be determined.
+        if (predecessor->IsReachable() && !predecessor->IsDeoptimizing()) {
+          HBasicBlock* pred_succ;
+          bool known_pred_succ =
+              predecessor->end()->KnownSuccessorBlock(&pred_succ);
+          if (!known_pred_succ || pred_succ == block) {
+            is_reachable = true;
+            break;
+          }
+        }
+        if (block->is_osr_entry()) {
+          is_reachable = true;
+        }
+      }
+      if (!is_reachable) {
+        block->MarkUnreachable();
+        changed = true;
+      }
+    }
+  }
+}
+
+
+void HMarkUnreachableBlocksPhase::Run() {
+  MarkUnreachableBlocks();
+}
+
+}  // namespace internal
+}  // namespace v8