Revert "[ADT] fail-fast iterators for DenseMap"

This reverts commit r231035.  It breaks clang.

llvm-svn: 231050

include/llvm/ADT/DenseMap.h

@@ -15,7 +15,6 @@
 #define LLVM_ADT_DENSEMAP_H
 
 #include "llvm/ADT/DenseMapInfo.h"
-#include "llvm/ADT/EpochTracker.h"
 #include "llvm/Support/AlignOf.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/MathExtras.h"
@@ -51,7 +50,7 @@ class DenseMapIterator;
 
 template <typename DerivedT, typename KeyT, typename ValueT, typename KeyInfoT,
           typename BucketT>
-class DenseMapBase : public DebugEpochBase {
+class DenseMapBase {
 public:
   typedef unsigned size_type;
   typedef KeyT key_type;
@@ -63,17 +62,16 @@ public:
       const_iterator;
   inline iterator begin() {
     // When the map is empty, avoid the overhead of AdvancePastEmptyBuckets().
-    return empty() ? end() : iterator(getBuckets(), getBucketsEnd(), *this);
+    return empty() ? end() : iterator(getBuckets(), getBucketsEnd());
   }
   inline iterator end() {
-    return iterator(getBucketsEnd(), getBucketsEnd(), *this, true);
+    return iterator(getBucketsEnd(), getBucketsEnd(), true);
   }
   inline const_iterator begin() const {
-    return empty() ? end()
+    return empty() ? end() : const_iterator(getBuckets(), getBucketsEnd());
-                   : const_iterator(getBuckets(), getBucketsEnd(), *this);
   }
   inline const_iterator end() const {
-    return const_iterator(getBucketsEnd(), getBucketsEnd(), *this, true);
+    return const_iterator(getBucketsEnd(), getBucketsEnd(), true);
   }
 
   bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const {
@@ -83,13 +81,11 @@ public:
 
   /// Grow the densemap so that it has at least Size buckets. Does not shrink
   void resize(size_type Size) {
-    incrementEpoch();
     if (Size > getNumBuckets())
       grow(Size);
   }
 
   void clear() {
-    incrementEpoch();
     if (getNumEntries() == 0 && getNumTombstones() == 0) return;
 
     // If the capacity of the array is huge, and the # elements used is small,
@@ -122,13 +118,13 @@ public:
   iterator find(const KeyT &Val) {
     BucketT *TheBucket;
     if (LookupBucketFor(Val, TheBucket))
-      return iterator(TheBucket, getBucketsEnd(), *this, true);
+      return iterator(TheBucket, getBucketsEnd(), true);
     return end();
   }
   const_iterator find(const KeyT &Val) const {
     const BucketT *TheBucket;
     if (LookupBucketFor(Val, TheBucket))
-      return const_iterator(TheBucket, getBucketsEnd(), *this, true);
+      return const_iterator(TheBucket, getBucketsEnd(), true);
     return end();
   }
 
@@ -141,14 +137,14 @@ public:
   iterator find_as(const LookupKeyT &Val) {
     BucketT *TheBucket;
     if (LookupBucketFor(Val, TheBucket))
-      return iterator(TheBucket, getBucketsEnd(), *this, true);
+      return iterator(TheBucket, getBucketsEnd(), true);
     return end();
   }
   template<class LookupKeyT>
   const_iterator find_as(const LookupKeyT &Val) const {
     const BucketT *TheBucket;
     if (LookupBucketFor(Val, TheBucket))
-      return const_iterator(TheBucket, getBucketsEnd(), *this, true);
+      return const_iterator(TheBucket, getBucketsEnd(), true);
     return end();
   }
 
@@ -167,13 +163,12 @@ public:
   std::pair<iterator, bool> insert(const std::pair<KeyT, ValueT> &KV) {
     BucketT *TheBucket;
     if (LookupBucketFor(KV.first, TheBucket))
-      return std::make_pair(iterator(TheBucket, getBucketsEnd(), *this, true),
+      return std::make_pair(iterator(TheBucket, getBucketsEnd(), true),
                             false); // Already in map.
 
     // Otherwise, insert the new element.
     TheBucket = InsertIntoBucket(KV.first, KV.second, TheBucket);
-    return std::make_pair(iterator(TheBucket, getBucketsEnd(), *this, true),
+    return std::make_pair(iterator(TheBucket, getBucketsEnd(), true), true);
-                          true);
   }
 
   // Inserts key,value pair into the map if the key isn't already in the map.
@@ -182,15 +177,14 @@ public:
   std::pair<iterator, bool> insert(std::pair<KeyT, ValueT> &&KV) {
     BucketT *TheBucket;
     if (LookupBucketFor(KV.first, TheBucket))
-      return std::make_pair(iterator(TheBucket, getBucketsEnd(), *this, true),
+      return std::make_pair(iterator(TheBucket, getBucketsEnd(), true),
                             false); // Already in map.
-
+    
     // Otherwise, insert the new element.
     TheBucket = InsertIntoBucket(std::move(KV.first),
                                  std::move(KV.second),
                                  TheBucket);
-    return std::make_pair(iterator(TheBucket, getBucketsEnd(), *this, true),
+    return std::make_pair(iterator(TheBucket, getBucketsEnd(), true), true);
-                          true);
   }
 
   /// insert - Range insertion of pairs.
@@ -437,8 +431,6 @@ private:
   }
 
   BucketT *InsertIntoBucketImpl(const KeyT &Key, BucketT *TheBucket) {
-    incrementEpoch();
-
     // If the load of the hash table is more than 3/4, or if fewer than 1/8 of
     // the buckets are empty (meaning that many are filled with tombstones),
     // grow the table.
@@ -995,7 +987,7 @@ private:
 
 template <typename KeyT, typename ValueT, typename KeyInfoT, typename Bucket,
           bool IsConst>
-class DenseMapIterator : DebugEpochBase::HandleBase {
+class DenseMapIterator {
   typedef DenseMapIterator<KeyT, ValueT, KeyInfoT, Bucket, true> ConstIterator;
   friend class DenseMapIterator<KeyT, ValueT, KeyInfoT, Bucket, true>;
 
@@ -1011,10 +1003,8 @@ private:
 public:
   DenseMapIterator() : Ptr(nullptr), End(nullptr) {}
 
-  DenseMapIterator(pointer Pos, pointer E, const DebugEpochBase &Epoch,
+  DenseMapIterator(pointer Pos, pointer E, bool NoAdvance = false)
-                   bool NoAdvance = false)
+    : Ptr(Pos), End(E) {
-      : DebugEpochBase::HandleBase(&Epoch), Ptr(Pos), End(E) {
-    assert(isHandleInSync() && "invalid construction!");
     if (!NoAdvance) AdvancePastEmptyBuckets();
   }
 
@@ -1023,14 +1013,12 @@ public:
   // Otherwise this is a copy constructor for iterator.
   DenseMapIterator(
       const DenseMapIterator<KeyT, ValueT, KeyInfoT, Bucket, false> &I)
-      : DebugEpochBase::HandleBase(I), Ptr(I.Ptr), End(I.End) {}
+      : Ptr(I.Ptr), End(I.End) {}
 
   reference operator*() const {
-    assert(isHandleInSync() && "invalid iterator access!");
     return *Ptr;
   }
   pointer operator->() const {
-    assert(isHandleInSync() && "invalid iterator access!");
     return Ptr;
   }
 
@@ -1042,13 +1030,11 @@ public:
   }
 
   inline DenseMapIterator& operator++() {  // Preincrement
-    assert(isHandleInSync() && "invalid iterator access!");
     ++Ptr;
     AdvancePastEmptyBuckets();
     return *this;
   }
   DenseMapIterator operator++(int) {  // Postincrement
-    assert(isHandleInSync() && "invalid iterator access!");
     DenseMapIterator tmp = *this; ++*this; return tmp;
   }
 

include/llvm/ADT/EpochTracker.h

@@ -1,91 +0,0 @@
-//===- llvm/ADT/EpochTracker.h - ADT epoch tracking --------------*- C++ -*-==//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file defines the DebugEpochBase and DebugEpochBase::HandleBase classes.
-// These can be used to write iterators that are fail-fast when LLVM is built
-// with asserts enabled.
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef LLVM_ADT_EPOCH_TRACKER_H
-#define LLVM_ADT_EPOCH_TRACKER_H
-
-#include <cstdint>
-
-namespace llvm {
-
-#ifdef NDEBUG
-
-class DebugEpochBase {
-public:
-  void incrementEpoch() {}
-
-  class HandleBase {
-  public:
-    HandleBase() {}
-    explicit HandleBase(const DebugEpochBase *) {}
-    bool isHandleInSync() { return true; }
-  };
-};
-
-#else
-
-/// \brief A base class for data structure classes wishing to make iterators
-/// ("handles") pointing into themselves fail-fast.  When building without
-/// asserts, this class is empty and does nothing.
-///
-/// DebugEpochBase does not by itself track handles pointing into itself.  The
-/// expectation is that routines touching the handles will poll on
-/// isHandleInSync at appropriate points to assert that the handle they're using
-/// is still valid.
-///
-class DebugEpochBase {
-  uint64_t Epoch;
-
-public:
-  DebugEpochBase() : Epoch(0) {}
-
-  /// \brief Calling incrementEpoch invalidates all handles pointing into the
-  /// calling instance.
-  void incrementEpoch() { ++Epoch; }
-
-  /// \brief The destructor calls incrementEpoch to make use-after-free bugs
-  /// more likely to crash deterministically.
-  ~DebugEpochBase() { incrementEpoch(); }
-
-  /// \brief A base class for iterator classes ("handles") that wish to poll for
-  /// iterator invalidating modifications in the underlying data structure.
-  /// When LLVM is built without asserts, this class is empty and does nothing.
-  ///
-  /// HandleBase does not track the parent data structure by itself.  It expects
-  /// the routines modifying the data structure to call incrementEpoch when they
-  /// make an iterator-invalidating modification.
-  ///
-  class HandleBase {
-    const uint64_t *EpochAddress;
-    uint64_t EpochAtCreation;
-
-  public:
-    HandleBase() : EpochAddress(nullptr), EpochAtCreation(UINT64_MAX) {}
-
-    explicit HandleBase(const DebugEpochBase *Parent)
-        : EpochAddress(&Parent->Epoch), EpochAtCreation(Parent->Epoch) {}
-
-    /// \brief Returns true if the DebugEpochBase this Handle is linked to has
-    /// not called incrementEpoch on itself since the creation of this
-    /// HandleBase instance.
-    bool isHandleInSync() const { return *EpochAddress == EpochAtCreation; }
-  };
-};
-
-#endif
-
-} // namespace llvm
-
-#endif