diff --git a/allocator_config.h b/allocator_config.h
index 58c2e35..8e103f2 100644
--- a/allocator_config.h
+++ b/allocator_config.h
@@ -21,6 +21,35 @@
 
 namespace scudo {
 
+// The combined allocator uses a structure as a template argument that
+// specifies the configuration options for the various subcomponents of the
+// allocator.
+//
+// struct ExampleConfig {
+//   // SizeClasMmap to use with the Primary.
+//   using SizeClassMap = DefaultSizeClassMap;
+//   // Indicates possible support for Memory Tagging.
+//   static const bool MaySupportMemoryTagging = false;
+//   // Defines the Primary allocator to use.
+//   typedef SizeClassAllocator64<ExampleConfig> Primary;
+//   // Log2 of the size of a size class region, as used by the Primary.
+//   static const uptr PrimaryRegionSizeLog = 30U;
+//   // Defines the type and scale of a compact pointer. A compact pointer can
+//   // be understood as the offset of a pointer within the region it belongs
+//   // to, in increments of a power-of-2 scale.
+//   // eg: Ptr = Base + (CompactPtr << Scale).
+//   typedef u32 PrimaryCompactPtrT;
+//   static const uptr PrimaryCompactPtrScale = SCUDO_MIN_ALIGNMENT_LOG;
+//   // Defines the minimal & maximal release interval that can be set.
+//   static const s32 PrimaryMinReleaseToOsIntervalMs = INT32_MIN;
+//   static const s32 PrimaryMaxReleaseToOsIntervalMs = INT32_MAX;
+//   // Defines the type of cache used by the Secondary. Some additional
+//   // configuration entries can be necessary depending on the Cache.
+//   typedef MapAllocatorNoCache SecondaryCache;
+//   // Thread-Specific Data Registry used, shared or exclusive.
+//   template <class A> using TSDRegistryT = TSDRegistrySharedT<A, 8U, 4U>;
+// };
+
 // Default configurations for various platforms.
 
 struct DefaultConfig {
@@ -29,10 +58,13 @@
 
 #if SCUDO_CAN_USE_PRIMARY64
   typedef SizeClassAllocator64<DefaultConfig> Primary;
-  static const uptr PrimaryRegionSizeLog = 30U;
+  static const uptr PrimaryRegionSizeLog = 32U;
+  typedef uptr PrimaryCompactPtrT;
+  static const uptr PrimaryCompactPtrScale = 0;
 #else
   typedef SizeClassAllocator32<DefaultConfig> Primary;
   static const uptr PrimaryRegionSizeLog = 19U;
+  typedef uptr PrimaryCompactPtrT;
 #endif
   static const s32 PrimaryMinReleaseToOsIntervalMs = INT32_MIN;
   static const s32 PrimaryMaxReleaseToOsIntervalMs = INT32_MAX;
@@ -55,9 +87,12 @@
 #if SCUDO_CAN_USE_PRIMARY64
   typedef SizeClassAllocator64<AndroidConfig> Primary;
   static const uptr PrimaryRegionSizeLog = 28U;
+  typedef u32 PrimaryCompactPtrT;
+  static const uptr PrimaryCompactPtrScale = SCUDO_MIN_ALIGNMENT_LOG;
 #else
   typedef SizeClassAllocator32<AndroidConfig> Primary;
   static const uptr PrimaryRegionSizeLog = 18U;
+  typedef uptr PrimaryCompactPtrT;
 #endif
   static const s32 PrimaryMinReleaseToOsIntervalMs = 1000;
   static const s32 PrimaryMaxReleaseToOsIntervalMs = 1000;
@@ -81,9 +116,12 @@
 #if SCUDO_CAN_USE_PRIMARY64
   typedef SizeClassAllocator64<AndroidSvelteConfig> Primary;
   static const uptr PrimaryRegionSizeLog = 27U;
+  typedef u32 PrimaryCompactPtrT;
+  static const uptr PrimaryCompactPtrScale = SCUDO_MIN_ALIGNMENT_LOG;
 #else
   typedef SizeClassAllocator32<AndroidSvelteConfig> Primary;
   static const uptr PrimaryRegionSizeLog = 16U;
+  typedef uptr PrimaryCompactPtrT;
 #endif
   static const s32 PrimaryMinReleaseToOsIntervalMs = 1000;
   static const s32 PrimaryMaxReleaseToOsIntervalMs = 1000;
@@ -107,6 +145,8 @@
 
   typedef SizeClassAllocator64<FuchsiaConfig> Primary;
   static const uptr PrimaryRegionSizeLog = 30U;
+  typedef u32 PrimaryCompactPtrT;
+  static const uptr PrimaryCompactPtrScale = SCUDO_MIN_ALIGNMENT_LOG;
   static const s32 PrimaryMinReleaseToOsIntervalMs = INT32_MIN;
   static const s32 PrimaryMaxReleaseToOsIntervalMs = INT32_MAX;
 
diff --git a/local_cache.h b/local_cache.h
index 089aeb9..8ee2b1c 100644
--- a/local_cache.h
+++ b/local_cache.h
@@ -17,24 +17,25 @@
 
 template <class SizeClassAllocator> struct SizeClassAllocatorLocalCache {
   typedef typename SizeClassAllocator::SizeClassMap SizeClassMap;
+  typedef typename SizeClassAllocator::CompactPtrT CompactPtrT;
 
   struct TransferBatch {
     static const u32 MaxNumCached = SizeClassMap::MaxNumCachedHint;
-    void setFromArray(void **Array, u32 N) {
+    void setFromArray(CompactPtrT *Array, u32 N) {
       DCHECK_LE(N, MaxNumCached);
       Count = N;
-      memcpy(Batch, Array, sizeof(void *) * Count);
+      memcpy(Batch, Array, sizeof(Batch[0]) * Count);
     }
     void clear() { Count = 0; }
-    void add(void *P) {
+    void add(CompactPtrT P) {
       DCHECK_LT(Count, MaxNumCached);
       Batch[Count++] = P;
     }
-    void copyToArray(void **Array) const {
-      memcpy(Array, Batch, sizeof(void *) * Count);
+    void copyToArray(CompactPtrT *Array) const {
+      memcpy(Array, Batch, sizeof(Batch[0]) * Count);
     }
     u32 getCount() const { return Count; }
-    void *get(u32 I) const {
+    CompactPtrT get(u32 I) const {
       DCHECK_LE(I, Count);
       return Batch[I];
     }
@@ -45,7 +46,7 @@
 
   private:
     u32 Count;
-    void *Batch[MaxNumCached];
+    CompactPtrT Batch[MaxNumCached];
   };
 
   void initLinkerInitialized(GlobalStats *S, SizeClassAllocator *A) {
@@ -78,13 +79,10 @@
     // Count, while Chunks might be further off (depending on Count). That keeps
     // the memory accesses in close quarters.
     const uptr ClassSize = C->ClassSize;
-    void *P = C->Chunks[--C->Count];
-    // The jury is still out as to whether any kind of PREFETCH here increases
-    // performance. It definitely decreases performance on Android though.
-    // if (!SCUDO_ANDROID) PREFETCH(P);
+    CompactPtrT CompactP = C->Chunks[--C->Count];
     Stats.add(StatAllocated, ClassSize);
     Stats.sub(StatFree, ClassSize);
-    return P;
+    return Allocator->decompactPtr(ClassId, CompactP);
   }
 
   void deallocate(uptr ClassId, void *P) {
@@ -97,7 +95,8 @@
       drain(C, ClassId);
     // See comment in allocate() about memory accesses.
     const uptr ClassSize = C->ClassSize;
-    C->Chunks[C->Count++] = P;
+    C->Chunks[C->Count++] =
+        Allocator->compactPtr(ClassId, reinterpret_cast<uptr>(P));
     Stats.sub(StatAllocated, ClassSize);
     Stats.add(StatFree, ClassSize);
   }
@@ -124,7 +123,7 @@
     u32 Count;
     u32 MaxCount;
     uptr ClassSize;
-    void *Chunks[2 * TransferBatch::MaxNumCached];
+    CompactPtrT Chunks[2 * TransferBatch::MaxNumCached];
   };
   PerClass PerClassArray[NumClasses];
   LocalStats Stats;
@@ -166,7 +165,8 @@
 
   NOINLINE void drain(PerClass *C, uptr ClassId) {
     const u32 Count = Min(C->MaxCount / 2, C->Count);
-    TransferBatch *B = createBatch(ClassId, C->Chunks[0]);
+    TransferBatch *B =
+        createBatch(ClassId, Allocator->decompactPtr(ClassId, C->Chunks[0]));
     if (UNLIKELY(!B))
       reportOutOfMemory(
           SizeClassAllocator::getSizeByClassId(SizeClassMap::BatchClassId));
diff --git a/primary32.h b/primary32.h
index a88a2a6..5b62c15 100644
--- a/primary32.h
+++ b/primary32.h
@@ -41,6 +41,7 @@
 
 template <typename Config> class SizeClassAllocator32 {
 public:
+  typedef typename Config::PrimaryCompactPtrT CompactPtrT;
   typedef typename Config::SizeClassMap SizeClassMap;
   // The bytemap can only track UINT8_MAX - 1 classes.
   static_assert(SizeClassMap::LargestClassId <= (UINT8_MAX - 1), "");
@@ -67,7 +68,7 @@
 
     u32 Seed;
     const u64 Time = getMonotonicTime();
-    if (UNLIKELY(!getRandom(reinterpret_cast<void *>(&Seed), sizeof(Seed))))
+    if (!getRandom(reinterpret_cast<void *>(&Seed), sizeof(Seed)))
       Seed = static_cast<u32>(
           Time ^ (reinterpret_cast<uptr>(SizeClassInfoArray) >> 6));
     for (uptr I = 0; I < NumClasses; I++) {
@@ -102,6 +103,14 @@
     PossibleRegions.unmapTestOnly();
   }
 
+  CompactPtrT compactPtr(UNUSED uptr ClassId, uptr Ptr) const {
+    return static_cast<CompactPtrT>(Ptr);
+  }
+
+  void *decompactPtr(UNUSED uptr ClassId, CompactPtrT CompactPtr) const {
+    return reinterpret_cast<void *>(static_cast<uptr>(CompactPtr));
+  }
+
   TransferBatch *popBatch(CacheT *C, uptr ClassId) {
     DCHECK_LT(ClassId, NumClasses);
     SizeClassInfo *Sci = getSizeClassInfo(ClassId);
@@ -359,17 +368,18 @@
     // Fill the transfer batches and put them in the size-class freelist. We
     // need to randomize the blocks for security purposes, so we first fill a
     // local array that we then shuffle before populating the batches.
-    void *ShuffleArray[ShuffleArraySize];
+    CompactPtrT ShuffleArray[ShuffleArraySize];
     DCHECK_LE(NumberOfBlocks, ShuffleArraySize);
 
     uptr P = Region + Offset;
     for (u32 I = 0; I < NumberOfBlocks; I++, P += Size)
-      ShuffleArray[I] = reinterpret_cast<void *>(P);
+      ShuffleArray[I] = reinterpret_cast<CompactPtrT>(P);
     // No need to shuffle the batches size class.
     if (ClassId != SizeClassMap::BatchClassId)
       shuffle(ShuffleArray, NumberOfBlocks, &Sci->RandState);
     for (u32 I = 0; I < NumberOfBlocks;) {
-      TransferBatch *B = C->createBatch(ClassId, ShuffleArray[I]);
+      TransferBatch *B =
+          C->createBatch(ClassId, reinterpret_cast<void *>(ShuffleArray[I]));
       if (UNLIKELY(!B))
         return nullptr;
       const u32 N = Min(MaxCount, NumberOfBlocks - I);
@@ -435,7 +445,7 @@
     if (BlockSize < PageSize / 16U) {
       if (!Force && BytesPushed < Sci->AllocatedUser / 16U)
         return 0;
-      // We want 8x% to 9x% free bytes (the larger the bock, the lower the %).
+      // We want 8x% to 9x% free bytes (the larger the block, the lower the %).
       if ((BytesInFreeList * 100U) / Sci->AllocatedUser <
           (100U - 1U - BlockSize / 16U))
         return 0;
@@ -463,8 +473,11 @@
     auto SkipRegion = [this, First, ClassId](uptr RegionIndex) {
       return (PossibleRegions[First + RegionIndex] - 1U) != ClassId;
     };
-    releaseFreeMemoryToOS(Sci->FreeList, Base, RegionSize, NumberOfRegions,
-                          BlockSize, &Recorder, SkipRegion);
+    auto DecompactPtr = [](CompactPtrT CompactPtr) {
+      return reinterpret_cast<uptr>(CompactPtr);
+    };
+    releaseFreeMemoryToOS(Sci->FreeList, RegionSize, NumberOfRegions, BlockSize,
+                          &Recorder, DecompactPtr, SkipRegion);
     if (Recorder.getReleasedRangesCount() > 0) {
       Sci->ReleaseInfo.PushedBlocksAtLastRelease = Sci->Stats.PushedBlocks;
       Sci->ReleaseInfo.RangesReleased += Recorder.getReleasedRangesCount();
diff --git a/primary64.h b/primary64.h
index 16b1226..7b930c9 100644
--- a/primary64.h
+++ b/primary64.h
@@ -42,6 +42,8 @@
 
 template <typename Config> class SizeClassAllocator64 {
 public:
+  typedef typename Config::PrimaryCompactPtrT CompactPtrT;
+  static const uptr CompactPtrScale = Config::PrimaryCompactPtrScale;
   typedef typename Config::SizeClassMap SizeClassMap;
   typedef SizeClassAllocator64<Config> ThisT;
   typedef SizeClassAllocatorLocalCache<ThisT> CacheT;
@@ -62,7 +64,7 @@
 
     u32 Seed;
     const u64 Time = getMonotonicTime();
-    if (UNLIKELY(!getRandom(reinterpret_cast<void *>(&Seed), sizeof(Seed))))
+    if (!getRandom(reinterpret_cast<void *>(&Seed), sizeof(Seed)))
       Seed = static_cast<u32>(Time ^ (PrimaryBase >> 12));
     const uptr PageSize = getPageSizeCached();
     for (uptr I = 0; I < NumClasses; I++) {
@@ -194,6 +196,24 @@
 
   static uptr getRegionInfoArraySize() { return sizeof(RegionInfoArray); }
 
+  uptr getCompactPtrBaseByClassId(uptr ClassId) {
+    // If we are not compacting pointers, base everything off of 0.
+    if (sizeof(CompactPtrT) == sizeof(uptr) && CompactPtrScale == 0)
+      return 0;
+    return getRegionInfo(ClassId)->RegionBeg;
+  }
+
+  CompactPtrT compactPtr(uptr ClassId, uptr Ptr) {
+    DCHECK_LE(ClassId, SizeClassMap::LargestClassId);
+    return compactPtrInternal(getCompactPtrBaseByClassId(ClassId), Ptr);
+  }
+
+  void *decompactPtr(uptr ClassId, CompactPtrT CompactPtr) {
+    DCHECK_LE(ClassId, SizeClassMap::LargestClassId);
+    return reinterpret_cast<void *>(
+        decompactPtrInternal(getCompactPtrBaseByClassId(ClassId), CompactPtr));
+  }
+
   static BlockInfo findNearestBlock(const char *RegionInfoData, uptr Ptr) {
     const RegionInfo *RegionInfoArray =
         reinterpret_cast<const RegionInfo *>(RegionInfoData);
@@ -265,14 +285,14 @@
   struct UnpaddedRegionInfo {
     HybridMutex Mutex;
     SinglyLinkedList<TransferBatch> FreeList;
-    RegionStats Stats;
-    bool Exhausted;
-    u32 RandState;
     uptr RegionBeg;
+    RegionStats Stats;
+    u32 RandState;
     uptr MappedUser;    // Bytes mapped for user memory.
     uptr AllocatedUser; // Bytes allocated for user memory.
     MapPlatformData Data;
     ReleaseToOsInfo ReleaseInfo;
+    bool Exhausted;
   };
   struct RegionInfo : UnpaddedRegionInfo {
     char Padding[SCUDO_CACHE_LINE_SIZE -
@@ -294,6 +314,14 @@
     return PrimaryBase + (ClassId << Config::PrimaryRegionSizeLog);
   }
 
+  static CompactPtrT compactPtrInternal(uptr Base, uptr Ptr) {
+    return static_cast<CompactPtrT>((Ptr - Base) >> CompactPtrScale);
+  }
+
+  static uptr decompactPtrInternal(uptr Base, CompactPtrT CompactPtr) {
+    return Base + (static_cast<uptr>(CompactPtr) << CompactPtrScale);
+  }
+
   NOINLINE TransferBatch *populateFreeList(CacheT *C, uptr ClassId,
                                            RegionInfo *Region) {
     const uptr Size = getSizeByClassId(ClassId);
@@ -303,12 +331,12 @@
     const uptr MappedUser = Region->MappedUser;
     const uptr TotalUserBytes = Region->AllocatedUser + MaxCount * Size;
     // Map more space for blocks, if necessary.
-    if (UNLIKELY(TotalUserBytes > MappedUser)) {
+    if (TotalUserBytes > MappedUser) {
       // Do the mmap for the user memory.
-      const uptr UserMapSize =
+      const uptr MapSize =
           roundUpTo(TotalUserBytes - MappedUser, MapSizeIncrement);
       const uptr RegionBase = RegionBeg - getRegionBaseByClassId(ClassId);
-      if (RegionBase + MappedUser + UserMapSize > RegionSize) {
+      if (UNLIKELY(RegionBase + MappedUser + MapSize > RegionSize)) {
         if (!Region->Exhausted) {
           Region->Exhausted = true;
           ScopedString Str(1024);
@@ -322,14 +350,15 @@
       }
       if (MappedUser == 0)
         Region->Data = Data;
-      if (!map(reinterpret_cast<void *>(RegionBeg + MappedUser), UserMapSize,
-               "scudo:primary",
-               MAP_ALLOWNOMEM | MAP_RESIZABLE |
-                   (useMemoryTagging<Config>(Options.load()) ? MAP_MEMTAG : 0),
-               &Region->Data))
+      if (UNLIKELY(!map(
+              reinterpret_cast<void *>(RegionBeg + MappedUser), MapSize,
+              "scudo:primary",
+              MAP_ALLOWNOMEM | MAP_RESIZABLE |
+                  (useMemoryTagging<Config>(Options.load()) ? MAP_MEMTAG : 0),
+              &Region->Data)))
         return nullptr;
-      Region->MappedUser += UserMapSize;
-      C->getStats().add(StatMapped, UserMapSize);
+      Region->MappedUser += MapSize;
+      C->getStats().add(StatMapped, MapSize);
     }
 
     const u32 NumberOfBlocks = Min(
@@ -339,17 +368,20 @@
 
     constexpr u32 ShuffleArraySize =
         MaxNumBatches * TransferBatch::MaxNumCached;
-    void *ShuffleArray[ShuffleArraySize];
+    CompactPtrT ShuffleArray[ShuffleArraySize];
     DCHECK_LE(NumberOfBlocks, ShuffleArraySize);
 
+    const uptr CompactPtrBase = getCompactPtrBaseByClassId(ClassId);
     uptr P = RegionBeg + Region->AllocatedUser;
     for (u32 I = 0; I < NumberOfBlocks; I++, P += Size)
-      ShuffleArray[I] = reinterpret_cast<void *>(P);
+      ShuffleArray[I] = compactPtrInternal(CompactPtrBase, P);
     // No need to shuffle the batches size class.
     if (ClassId != SizeClassMap::BatchClassId)
       shuffle(ShuffleArray, NumberOfBlocks, &Region->RandState);
     for (u32 I = 0; I < NumberOfBlocks;) {
-      TransferBatch *B = C->createBatch(ClassId, ShuffleArray[I]);
+      TransferBatch *B =
+          C->createBatch(ClassId, reinterpret_cast<void *>(decompactPtrInternal(
+                                      CompactPtrBase, ShuffleArray[I])));
       if (UNLIKELY(!B))
         return nullptr;
       const u32 N = Min(MaxCount, NumberOfBlocks - I);
@@ -409,7 +441,7 @@
     if (BlockSize < PageSize / 16U) {
       if (!Force && BytesPushed < Region->AllocatedUser / 16U)
         return 0;
-      // We want 8x% to 9x% free bytes (the larger the bock, the lower the %).
+      // We want 8x% to 9x% free bytes (the larger the block, the lower the %).
       if ((BytesInFreeList * 100U) / Region->AllocatedUser <
           (100U - 1U - BlockSize / 16U))
         return 0;
@@ -426,11 +458,14 @@
       }
     }
 
-    auto SkipRegion = [](UNUSED uptr RegionIndex) { return false; };
     ReleaseRecorder Recorder(Region->RegionBeg, &Region->Data);
-    releaseFreeMemoryToOS(Region->FreeList, Region->RegionBeg,
-                          Region->AllocatedUser, 1U, BlockSize, &Recorder,
-                          SkipRegion);
+    const uptr CompactPtrBase = getCompactPtrBaseByClassId(ClassId);
+    auto DecompactPtr = [CompactPtrBase](CompactPtrT CompactPtr) {
+      return decompactPtrInternal(CompactPtrBase, CompactPtr);
+    };
+    auto SkipRegion = [](UNUSED uptr RegionIndex) { return false; };
+    releaseFreeMemoryToOS(Region->FreeList, Region->AllocatedUser, 1U,
+                          BlockSize, &Recorder, DecompactPtr, SkipRegion);
 
     if (Recorder.getReleasedRangesCount() > 0) {
       Region->ReleaseInfo.PushedBlocksAtLastRelease =
diff --git a/release.h b/release.h
index 5c11da2..a47ae2e 100644
--- a/release.h
+++ b/release.h
@@ -17,17 +17,19 @@
 
 class ReleaseRecorder {
 public:
-  ReleaseRecorder(uptr BaseAddress, MapPlatformData *Data = nullptr)
-      : BaseAddress(BaseAddress), Data(Data) {}
+  ReleaseRecorder(uptr Base, MapPlatformData *Data = nullptr)
+      : Base(Base), Data(Data) {}
 
   uptr getReleasedRangesCount() const { return ReleasedRangesCount; }
 
   uptr getReleasedBytes() const { return ReleasedBytes; }
 
+  uptr getBase() const { return Base; }
+
   // Releases [From, To) range of pages back to OS.
   void releasePageRangeToOS(uptr From, uptr To) {
     const uptr Size = To - From;
-    releasePagesToOS(BaseAddress, From, Size, Data);
+    releasePagesToOS(Base, From, Size, Data);
     ReleasedRangesCount++;
     ReleasedBytes += Size;
   }
@@ -35,7 +37,7 @@
 private:
   uptr ReleasedRangesCount = 0;
   uptr ReleasedBytes = 0;
-  uptr BaseAddress = 0;
+  uptr Base = 0;
   MapPlatformData *Data = nullptr;
 };
 
@@ -179,11 +181,13 @@
   uptr CurrentRangeStatePage = 0;
 };
 
-template <class TransferBatchT, class ReleaseRecorderT, typename SkipRegionT>
+template <class TransferBatchT, class ReleaseRecorderT, typename DecompactPtrT,
+          typename SkipRegionT>
 NOINLINE void
-releaseFreeMemoryToOS(const IntrusiveList<TransferBatchT> &FreeList, uptr Base,
+releaseFreeMemoryToOS(const IntrusiveList<TransferBatchT> &FreeList,
                       uptr RegionSize, uptr NumberOfRegions, uptr BlockSize,
-                      ReleaseRecorderT *Recorder, SkipRegionT SkipRegion) {
+                      ReleaseRecorderT *Recorder, DecompactPtrT DecompactPtr,
+                      SkipRegionT SkipRegion) {
   const uptr PageSize = getPageSizeCached();
 
   // Figure out the number of chunks per page and whether we can take a fast
@@ -236,9 +240,8 @@
     // Each chunk affects one page only.
     for (const auto &It : FreeList) {
       for (u32 I = 0; I < It.getCount(); I++) {
-        const uptr P = reinterpret_cast<uptr>(It.get(I)) - Base;
-        // This takes care of P < Base and P >= Base + RoundedSize.
-        if (UNLIKELY(P >= RoundedSize))
+        const uptr P = DecompactPtr(It.get(I)) - Recorder->getBase();
+        if (P >= RoundedSize)
           continue;
         const uptr RegionIndex = NumberOfRegions == 1U ? 0 : P / RegionSize;
         const uptr PInRegion = P - RegionIndex * RegionSize;
@@ -251,9 +254,8 @@
     const uptr LastBlockInRegion = ((RegionSize / BlockSize) - 1U) * BlockSize;
     for (const auto &It : FreeList) {
       for (u32 I = 0; I < It.getCount(); I++) {
-        const uptr P = reinterpret_cast<uptr>(It.get(I)) - Base;
-        // This takes care of P < Base and P >= Base + RoundedSize.
-        if (UNLIKELY(P >= RoundedSize))
+        const uptr P = DecompactPtr(It.get(I)) - Recorder->getBase();
+        if (P >= RoundedSize)
           continue;
         const uptr RegionIndex = NumberOfRegions == 1U ? 0 : P / RegionSize;
         uptr PInRegion = P - RegionIndex * RegionSize;
diff --git a/size_class_map.h b/size_class_map.h
index 5ed8e28..7b8bf74 100644
--- a/size_class_map.h
+++ b/size_class_map.h
@@ -168,13 +168,24 @@
   }
 };
 
+struct DefaultSizeClassConfig {
+  static const uptr NumBits = 3;
+  static const uptr MinSizeLog = 5;
+  static const uptr MidSizeLog = 8;
+  static const uptr MaxSizeLog = 17;
+  static const u32 MaxNumCachedHint = 10;
+  static const uptr MaxBytesCachedLog = 10;
+};
+
+typedef FixedSizeClassMap<DefaultSizeClassConfig> DefaultSizeClassMap;
+
 struct AndroidSizeClassConfig {
 #if SCUDO_WORDSIZE == 64U
   static const uptr NumBits = 7;
   static const uptr MinSizeLog = 4;
   static const uptr MidSizeLog = 6;
   static const uptr MaxSizeLog = 16;
-  static const u32 MaxNumCachedHint = 14;
+  static const u32 MaxNumCachedHint = 13;
   static const uptr MaxBytesCachedLog = 13;
 
   static constexpr u32 Classes[] = {
@@ -208,31 +219,20 @@
 
 typedef TableSizeClassMap<AndroidSizeClassConfig> AndroidSizeClassMap;
 
-struct DefaultSizeClassConfig {
-  static const uptr NumBits = 3;
-  static const uptr MinSizeLog = 5;
-  static const uptr MidSizeLog = 8;
-  static const uptr MaxSizeLog = 17;
-  static const u32 MaxNumCachedHint = 8;
-  static const uptr MaxBytesCachedLog = 10;
-};
-
-typedef FixedSizeClassMap<DefaultSizeClassConfig> DefaultSizeClassMap;
-
 struct SvelteSizeClassConfig {
 #if SCUDO_WORDSIZE == 64U
   static const uptr NumBits = 4;
   static const uptr MinSizeLog = 4;
   static const uptr MidSizeLog = 8;
   static const uptr MaxSizeLog = 14;
-  static const u32 MaxNumCachedHint = 4;
+  static const u32 MaxNumCachedHint = 13;
   static const uptr MaxBytesCachedLog = 10;
 #else
   static const uptr NumBits = 4;
   static const uptr MinSizeLog = 3;
   static const uptr MidSizeLog = 7;
   static const uptr MaxSizeLog = 14;
-  static const u32 MaxNumCachedHint = 5;
+  static const u32 MaxNumCachedHint = 14;
   static const uptr MaxBytesCachedLog = 10;
 #endif
 };
diff --git a/tests/combined_test.cpp b/tests/combined_test.cpp
index d1bdd27..a6c6d82 100644
--- a/tests/combined_test.cpp
+++ b/tests/combined_test.cpp
@@ -399,6 +399,8 @@
   static const scudo::uptr PrimaryRegionSizeLog = DeathRegionSizeLog;
   static const scudo::s32 PrimaryMinReleaseToOsIntervalMs = INT32_MIN;
   static const scudo::s32 PrimaryMaxReleaseToOsIntervalMs = INT32_MAX;
+  typedef scudo::uptr PrimaryCompactPtrT;
+  static const scudo::uptr PrimaryCompactPtrScale = 0;
 
   typedef scudo::MapAllocatorNoCache SecondaryCache;
   template <class A> using TSDRegistryT = scudo::TSDRegistrySharedT<A, 1U, 1U>;
diff --git a/tests/primary_test.cpp b/tests/primary_test.cpp
index eed6431..38bf671 100644
--- a/tests/primary_test.cpp
+++ b/tests/primary_test.cpp
@@ -58,6 +58,8 @@
   static const scudo::s32 PrimaryMinReleaseToOsIntervalMs = INT32_MIN;
   static const scudo::s32 PrimaryMaxReleaseToOsIntervalMs = INT32_MAX;
   static const bool MaySupportMemoryTagging = false;
+  typedef scudo::uptr PrimaryCompactPtrT;
+  static const scudo::uptr PrimaryCompactPtrScale = 0;
 };
 
 template <typename SizeClassMapT> struct TestConfig2 {
@@ -66,6 +68,8 @@
   static const scudo::s32 PrimaryMinReleaseToOsIntervalMs = INT32_MIN;
   static const scudo::s32 PrimaryMaxReleaseToOsIntervalMs = INT32_MAX;
   static const bool MaySupportMemoryTagging = false;
+  typedef scudo::uptr PrimaryCompactPtrT;
+  static const scudo::uptr PrimaryCompactPtrScale = 0;
 };
 
 template <typename SizeClassMapT> struct TestConfig3 {
@@ -74,6 +78,8 @@
   static const scudo::s32 PrimaryMinReleaseToOsIntervalMs = INT32_MIN;
   static const scudo::s32 PrimaryMaxReleaseToOsIntervalMs = INT32_MAX;
   static const bool MaySupportMemoryTagging = true;
+  typedef scudo::uptr PrimaryCompactPtrT;
+  static const scudo::uptr PrimaryCompactPtrScale = 0;
 };
 
 TEST(ScudoPrimaryTest, BasicPrimary) {
@@ -91,6 +97,8 @@
   static const scudo::s32 PrimaryMinReleaseToOsIntervalMs = INT32_MIN;
   static const scudo::s32 PrimaryMaxReleaseToOsIntervalMs = INT32_MAX;
   static const bool MaySupportMemoryTagging = false;
+  typedef scudo::uptr PrimaryCompactPtrT;
+  static const scudo::uptr PrimaryCompactPtrScale = 0;
 };
 
 // The 64-bit SizeClassAllocator can be easily OOM'd with small region sizes.
@@ -115,7 +123,7 @@
       break;
     }
     for (scudo::u32 J = 0; J < B->getCount(); J++)
-      memset(B->get(J), 'B', Size);
+      memset(Allocator.decompactPtr(ClassId, B->get(J)), 'B', Size);
     Batches.push_back(B);
   }
   while (!Batches.empty()) {
diff --git a/tests/release_test.cpp b/tests/release_test.cpp
index 9e991a7..04c0289 100644
--- a/tests/release_test.cpp
+++ b/tests/release_test.cpp
@@ -124,6 +124,8 @@
     for (scudo::uptr I = From; I < To; I += PageSize)
       ReportedPages.insert(I);
   }
+
+  scudo::uptr getBase() const { return 0; }
 };
 
 // Simplified version of a TransferBatch.
@@ -191,9 +193,10 @@
 
     // Release the memory.
     auto SkipRegion = [](UNUSED scudo::uptr RegionIndex) { return false; };
+    auto DecompactPtr = [](scudo::uptr P) { return P; };
     ReleasedPagesRecorder Recorder;
-    releaseFreeMemoryToOS(FreeList, 0, MaxBlocks * BlockSize, 1U, BlockSize,
-                          &Recorder, SkipRegion);
+    releaseFreeMemoryToOS(FreeList, MaxBlocks * BlockSize, 1U, BlockSize,
+                          &Recorder, DecompactPtr, SkipRegion);
 
     // Verify that there are no released pages touched by used chunks and all
     // ranges of free chunks big enough to contain the entire memory pages had