Turn mark deoptimize on undefined into a proper HPhase.

src/hydrogen-mark-deoptimize.cc

+// Copyright 2013 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:
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+//     * Redistributions in binary form must reproduce the above
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+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "hydrogen-mark-deoptimize.h"
+
+namespace v8 {
+namespace internal {
+
+void HMarkDeoptimizeOnUndefinedPhase::Run() {
+  const ZoneList<HPhi*>* phi_list = graph()->phi_list();
+  ZoneList<HPhi*> worklist(phi_list->length(), zone());
+  for (int i = 0; i < phi_list->length(); i++) {
+    HPhi* phi = phi_list->at(i);
+    if (phi->CheckFlag(HValue::kAllowUndefinedAsNaN)) {
+      for (HUseIterator it(phi->uses()); !it.Done(); it.Advance()) {
+        HValue* use_value = it.value();
+        if (!use_value->CheckFlag(HValue::kAllowUndefinedAsNaN)) {
+          // Enqueue to recursively check the phi operands below
+          phi->ClearFlag(HValue::kAllowUndefinedAsNaN);
+          ASSERT(!worklist.Contains(phi));
+          worklist.Add(phi, zone());
+          break;
+        }
+      }
+    }
+  }
+
+  // Recursively clear flag for phi operands
+  while (!worklist.is_empty()) {

[Dmitry Lomov (no reviews), 2013/07/29 15:31:48]

This fusion of two methods into one using the same worklist is a bit hard to
grok. Can we extract the second loop into a method and call it for each phi in
the phi list? (just the way the code was structured before)

[Benedikt Meurer, 2013/07/29 19:38:52]

Done. Also refactored the common AddToWorklist functionality into a separate
method.

+    HPhi* phi = worklist.RemoveLast();
+    ASSERT(!phi->CheckFlag(HValue::kAllowUndefinedAsNaN));
+    for (int i = 0; i < phi->OperandCount(); ++i) {
+      HValue* input = phi->OperandAt(i);
+      if (input->IsPhi() && input->CheckFlag(HValue::kAllowUndefinedAsNaN)) {
+        input->ClearFlag(HValue::kAllowUndefinedAsNaN);
+        ASSERT(!worklist.Contains(HPhi::cast(input)));
+        worklist.Add(HPhi::cast(input), zone());
+      }
+    }
+  }
+}
+
+} }  // namespace v8::internal