1 files changed, 54 insertions, 31 deletions

diff --git a/include/llvm/ExecutionEngine/Orc/SymbolStringPool.h b/include/llvm/ExecutionEngine/Orc/SymbolStringPool.h
index 717076e25609..c354f6c3559c 100644
--- a/include/llvm/ExecutionEngine/Orc/SymbolStringPool.h
+++ b/include/llvm/ExecutionEngine/Orc/SymbolStringPool.h
@@ -1,9 +1,8 @@
 //===- SymbolStringPool.h - Multi-threaded pool for JIT symbols -*- C++ -*-===//
 //
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
@@ -51,25 +50,20 @@ private:
 class SymbolStringPtr {
   friend class SymbolStringPool;
   friend struct DenseMapInfo<SymbolStringPtr>;
-  friend bool operator==(const SymbolStringPtr &LHS,
-                         const SymbolStringPtr &RHS);
-  friend bool operator<(const SymbolStringPtr &LHS, const SymbolStringPtr &RHS);
-
-  static SymbolStringPool::PoolMapEntry Tombstone;
 
 public:
   SymbolStringPtr() = default;
   SymbolStringPtr(const SymbolStringPtr &Other)
     : S(Other.S) {
-    if (S)
+    if (isRealPoolEntry(S))
       ++S->getValue();
   }
 
   SymbolStringPtr& operator=(const SymbolStringPtr &Other) {
-    if (S)
+    if (isRealPoolEntry(S))
       --S->getValue();
     S = Other.S;
-    if (S)
+    if (isRealPoolEntry(S))
       ++S->getValue();
     return *this;
   }
@@ -79,7 +73,7 @@ public:
   }
 
   SymbolStringPtr& operator=(SymbolStringPtr &&Other) {
-    if (S)
+    if (isRealPoolEntry(S))
       --S->getValue();
     S = nullptr;
     std::swap(S, Other.S);
@@ -87,34 +81,64 @@ public:
   }
 
   ~SymbolStringPtr() {
-    if (S)
+    if (isRealPoolEntry(S))
       --S->getValue();
   }
 
   StringRef operator*() const { return S->first(); }
 
+  friend bool operator==(const SymbolStringPtr &LHS,
+                         const SymbolStringPtr &RHS) {
+    return LHS.S == RHS.S;
+  }
+
+  friend bool operator!=(const SymbolStringPtr &LHS,
+                         const SymbolStringPtr &RHS) {
+    return !(LHS == RHS);
+  }
+
+  friend bool operator<(const SymbolStringPtr &LHS,
+                        const SymbolStringPtr &RHS) {
+    return LHS.S < RHS.S;
+  }
+
 private:
+  using PoolEntryPtr = SymbolStringPool::PoolMapEntry *;
 
   SymbolStringPtr(SymbolStringPool::PoolMapEntry *S)
       : S(S) {
-    if (S)
+    if (isRealPoolEntry(S))
       ++S->getValue();
   }
 
-  SymbolStringPool::PoolMapEntry *S = nullptr;
-};
+  // Returns false for null, empty, and tombstone values, true otherwise.
+  bool isRealPoolEntry(PoolEntryPtr P) {
+    return ((reinterpret_cast<uintptr_t>(P) - 1) & InvalidPtrMask) !=
+           InvalidPtrMask;
+  }
 
-inline bool operator==(const SymbolStringPtr &LHS, const SymbolStringPtr &RHS) {
-  return LHS.S == RHS.S;
-}
+  static SymbolStringPtr getEmptyVal() {
+    return SymbolStringPtr(reinterpret_cast<PoolEntryPtr>(EmptyBitPattern));
+  }
 
-inline bool operator!=(const SymbolStringPtr &LHS, const SymbolStringPtr &RHS) {
-  return !(LHS == RHS);
-}
+  static SymbolStringPtr getTombstoneVal() {
+    return SymbolStringPtr(reinterpret_cast<PoolEntryPtr>(TombstoneBitPattern));
+  }
 
-inline bool operator<(const SymbolStringPtr &LHS, const SymbolStringPtr &RHS) {
-  return LHS.S < RHS.S;
-}
+  constexpr static uintptr_t EmptyBitPattern =
+      std::numeric_limits<uintptr_t>::max()
+      << PointerLikeTypeTraits<PoolEntryPtr>::NumLowBitsAvailable;
+
+  constexpr static uintptr_t TombstoneBitPattern =
+      (std::numeric_limits<uintptr_t>::max() - 1)
+      << PointerLikeTypeTraits<PoolEntryPtr>::NumLowBitsAvailable;
+
+  constexpr static uintptr_t InvalidPtrMask =
+      (std::numeric_limits<uintptr_t>::max() - 3)
+      << PointerLikeTypeTraits<PoolEntryPtr>::NumLowBitsAvailable;
+
+  PoolEntryPtr S = nullptr;
+};
 
 inline SymbolStringPool::~SymbolStringPool() {
 #ifndef NDEBUG
@@ -151,16 +175,15 @@ template <>
 struct DenseMapInfo<orc::SymbolStringPtr> {
 
   static orc::SymbolStringPtr getEmptyKey() {
-    return orc::SymbolStringPtr();
+    return orc::SymbolStringPtr::getEmptyVal();
   }
 
   static orc::SymbolStringPtr getTombstoneKey() {
-    return orc::SymbolStringPtr(&orc::SymbolStringPtr::Tombstone);
+    return orc::SymbolStringPtr::getTombstoneVal();
   }
 
-  static unsigned getHashValue(orc::SymbolStringPtr V) {
-    uintptr_t IV = reinterpret_cast<uintptr_t>(V.S);
-    return unsigned(IV) ^ unsigned(IV >> 9);
+  static unsigned getHashValue(const orc::SymbolStringPtr &V) {
+    return DenseMapInfo<orc::SymbolStringPtr::PoolEntryPtr>::getHashValue(V.S);
   }
 
   static bool isEqual(const orc::SymbolStringPtr &LHS,