Rollback trunk to 3.21.16.2

src/hydrogen-alias-analysis.h

Index: src/hydrogen-alias-analysis.h
diff --git a/src/hydrogen-alias-analysis.h b/src/hydrogen-alias-analysis.h
index 21a54625ff8587a59532d26aa210a4423849f540..73e116e63e171e9a4fd8e1478a53ff1bb45e8236 100644
--- a/src/hydrogen-alias-analysis.h
+++ b/src/hydrogen-alias-analysis.h
@@ -88,6 +88,15 @@ class HAliasAnalyzer : public ZoneObject {
   inline bool NoAlias(HValue* a, HValue* b) {
     return Query(a, b) == kNoAlias;
   }
+
+  // Returns the actual value of an instruction. In the case of a chain
+  // of informative definitions, return the root of the chain.
+  HValue* ActualValue(HValue* obj) {
+    while (obj->IsInformativeDefinition()) {  // Walk a chain of idefs.
+      obj = obj->RedefinedOperand();
+    }
+    return obj;
+  }
 };