Index: llvm/include/llvm/Bitcode/LLVMBitCodes.h
===================================================================
--- llvm/include/llvm/Bitcode/LLVMBitCodes.h
+++ llvm/include/llvm/Bitcode/LLVMBitCodes.h
@@ -633,6 +633,7 @@
   ATTR_KIND_NOFREE = 62,
   ATTR_KIND_NOSYNC = 63,
   ATTR_KIND_SANITIZE_MEMTAG = 64,
+  ATTR_KIND_REACHABILITY = 65,
 };
 
 enum ComdatSelectionKindCodes {
Index: llvm/include/llvm/IR/Attributes.td
===================================================================
--- llvm/include/llvm/IR/Attributes.td
+++ llvm/include/llvm/IR/Attributes.td
@@ -127,6 +127,9 @@
 /// Function must not be optimized.
 def OptimizeNone : EnumAttr<"optnone">;
 
+/// Reachability from point A to B.
+def Reachability: EnumAttr<"reachable">;
+
 /// Function does not access memory.
 def ReadNone : EnumAttr<"readnone">;
 
Index: llvm/include/llvm/Transforms/IPO/Attributor.h
===================================================================
--- llvm/include/llvm/Transforms/IPO/Attributor.h
+++ llvm/include/llvm/Transforms/IPO/Attributor.h
@@ -1682,6 +1682,29 @@
   static const char ID;
 };
 
+/// An abstract interface to determine reachability of point A to B.
+struct AAReachability
+    : public StateWrapper<BooleanState, AbstractAttribute>, 
+      public IRPosition {
+  AAReachability(const IRPosition &IRP) : IRPosition(IRP) {}
+
+  /// Returns true if instruction is assumed reachable.
+  bool getAssumedReachability() const { return getAssumed(); }
+
+  /// Returns true if instruction is known reachable.
+  bool isKnownReachability() const { return getKnown(); }
+
+  /// Return an IR position, see struct IRPosition.
+  const IRPosition &getIRPosition() const override { return *this; }
+
+  /// Create an abstract attribute view for the position \p IRP.
+  static AAReachability &createForPosition(const IRPosition &IRP,
+                                           Attributor &A);
+
+  /// Unique ID (due to the unique address)
+  static const char ID;
+};
+
 /// An abstract interface for all noalias attributes.
 struct AANoAlias
     : public IRAttribute<Attribute::NoAlias,
Index: llvm/lib/Bitcode/Reader/BitcodeReader.cpp
===================================================================
--- llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -1300,6 +1300,10 @@
   case Attribute::SanitizeMemTag:
     llvm_unreachable("sanitize_memtag attribute not supported in raw format");
     break;
+  case Attribute::Reachability:
+    llvm_unreachable("reachable attribute not supported in raw format");
+    break;
+
   }
   llvm_unreachable("Unsupported attribute type");
 }
@@ -1314,7 +1318,8 @@
         I == Attribute::DereferenceableOrNull ||
         I == Attribute::ArgMemOnly ||
         I == Attribute::AllocSize ||
-        I == Attribute::NoSync)
+        I == Attribute::NoSync ||
+        I == Attribute::Reachability)
       continue;
     if (uint64_t A = (Val & getRawAttributeMask(I))) {
       if (I == Attribute::Alignment)
@@ -1541,6 +1546,8 @@
     return Attribute::ImmArg;
   case bitc::ATTR_KIND_SANITIZE_MEMTAG:
     return Attribute::SanitizeMemTag;
+  case bitc::ATTR_KIND_REACHABILITY:
+    return Attribute::Reachability;
   }
 }
 
Index: llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
===================================================================
--- llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -725,6 +725,8 @@
     return bitc::ATTR_KIND_IMMARG;
   case Attribute::SanitizeMemTag:
     return bitc::ATTR_KIND_SANITIZE_MEMTAG;
+  case Attribute::Reachability:
+    return bitc::ATTR_KIND_REACHABILITY;
   case Attribute::EndAttrKinds:
     llvm_unreachable("Can not encode end-attribute kinds marker.");
   case Attribute::None:
Index: llvm/lib/Transforms/IPO/Attributor.cpp
===================================================================
--- llvm/lib/Transforms/IPO/Attributor.cpp
+++ llvm/lib/Transforms/IPO/Attributor.cpp
@@ -2051,6 +2051,38 @@
   void trackStatistics() const override { STATS_DECLTRACK_CS_ATTR(willreturn); }
 };
 
+/// -------------------AAReachability Attribute--------------------------
+
+struct AAReachabilityImpl : AAReachability {
+  AAReachabilityImpl(const IRPosition &IRP) : AAReachability(IRP) {}
+
+  const std::string getAsStr() const override {
+    return getAssumedReachability() ? "reachable" : "may-reach";
+  }
+
+  /// See AbstractAttribute::initialize(...).
+  void initialize(Attributor &A) override {
+    getState().indicatePessimisticFixpoint();
+  }
+
+  /// See AbstractAttribute::updateImpl(...).
+  ChangeStatus updateImpl(Attributor &A) override {
+    return getState().indicatePessimisticFixpoint();
+  }
+
+  /// See AbstractAttribute::trackStatistics()
+  void trackStatistics() const override { STATS_DECLTRACK_CS_ATTR(reachable); }
+};
+
+struct AAReachabilityFunction final : public AAReachabilityImpl {
+  AAReachabilityFunction(const IRPosition &IRP) : AAReachabilityImpl(IRP) {}
+
+  /// See AbstractAttribute::trackStatistics()
+  void trackStatistics() const override {
+    STATS_DECLTRACK_CSARG_ATTR(Reachability)
+  }
+};
+
 /// ------------------------ NoAlias Argument Attribute ------------------------
 
 struct AANoAliasImpl : AANoAlias {
@@ -5684,6 +5716,7 @@
 const char AANoRecurse::ID = 0;
 const char AAWillReturn::ID = 0;
 const char AANoAlias::ID = 0;
+const char AAReachability::ID = 0;
 const char AANoReturn::ID = 0;
 const char AAIsDead::ID = 0;
 const char AADereferenceable::ID = 0;
@@ -5803,6 +5836,7 @@
 CREATE_ALL_ABSTRACT_ATTRIBUTE_FOR_POSITION(AANoFree)
 
 CREATE_FUNCTION_ONLY_ABSTRACT_ATTRIBUTE_FOR_POSITION(AAHeapToStack)
+CREATE_FUNCTION_ONLY_ABSTRACT_ATTRIBUTE_FOR_POSITION(AAReachability)
 
 CREATE_NON_RET_ABSTRACT_ATTRIBUTE_FOR_POSITION(AAMemoryBehavior)
 
Index: llvm/lib/Transforms/Utils/CodeExtractor.cpp
===================================================================
--- llvm/lib/Transforms/Utils/CodeExtractor.cpp
+++ llvm/lib/Transforms/Utils/CodeExtractor.cpp
@@ -869,6 +869,7 @@
       case Attribute::NoSync:
       case Attribute::None:
       case Attribute::NonNull:
+      case Attribute::Reachability:
       case Attribute::ReadNone:
       case Attribute::ReadOnly:
       case Attribute::Returned: