Index: include/llvm/Support/Allocator.h
===================================================================
--- include/llvm/Support/Allocator.h
+++ include/llvm/Support/Allocator.h
@@ -31,6 +31,10 @@
 #include <cstddef>
 #include <cstdlib>
 
+#if LLVM_ADDRESS_SANITIZER_BUILD
+#include <sanitizer/asan_interface.h>
+#endif
+
 namespace llvm {
 
 /// \brief CRTP base class providing obvious overloads for the core \c
@@ -221,6 +225,10 @@
       // Without this, MemorySanitizer messages for values originated from here
       // will point to the allocation of the entire slab.
       __msan_allocated_memory(AlignedPtr, Size);
+      // Similarly, tell ASan about this space.
+#if LLVM_ADDRESS_SANITIZER_BUILD
+      ASAN_UNPOISON_MEMORY_REGION(AlignedPtr, Size);
+#endif
       return AlignedPtr;
     }
 
@@ -228,12 +236,22 @@
     size_t PaddedSize = Size + Alignment - 1;
     if (PaddedSize > SizeThreshold) {
       void *NewSlab = Allocator.Allocate(PaddedSize, 0);
+
+      // We own the new slab and don't want anyone reading anyting other than
+      // pieces returned from this method.  So poison the whole slab.
+#if LLVM_ADDRESS_SANITIZER_BUILD
+      ASAN_POISON_MEMORY_REGION(NewSlab, PaddedSize);
+#endif
       CustomSizedSlabs.push_back(std::make_pair(NewSlab, PaddedSize));
 
       uintptr_t AlignedAddr = alignAddr(NewSlab, Alignment);
       assert(AlignedAddr + Size <= (uintptr_t)NewSlab + PaddedSize);
       char *AlignedPtr = (char*)AlignedAddr;
       __msan_allocated_memory(AlignedPtr, Size);
+      // Tell ASan about this space.
+#if LLVM_ADDRESS_SANITIZER_BUILD
+      ASAN_UNPOISON_MEMORY_REGION(AlignedPtr, Size);
+#endif
       return AlignedPtr;
     }
 
@@ -245,13 +263,23 @@
     char *AlignedPtr = (char*)AlignedAddr;
     CurPtr = AlignedPtr + Size;
     __msan_allocated_memory(AlignedPtr, Size);
+    // Similarly, tell ASan about this space.
+#if LLVM_ADDRESS_SANITIZER_BUILD
+    ASAN_UNPOISON_MEMORY_REGION(AlignedPtr, Size);
+#endif
     return AlignedPtr;
   }
 
   // Pull in base class overloads.
   using AllocatorBase<BumpPtrAllocatorImpl>::Allocate;
 
-  void Deallocate(const void * /*Ptr*/, size_t /*Size*/) {}
+  void Deallocate(const void * Ptr, size_t Size) {
+    // For speed reasons we don't want the BumpPtrAllocator itself to
+    //
+#if LLVM_ADDRESS_SANITIZER_BUILD
+    ASAN_POISON_MEMORY_REGION(Ptr, Size);
+#endif
+  }
 
   // Pull in base class overloads.
   using AllocatorBase<BumpPtrAllocatorImpl>::Deallocate;
@@ -309,6 +337,13 @@
     size_t AllocatedSlabSize = computeSlabSize(Slabs.size());
 
     void *NewSlab = Allocator.Allocate(AllocatedSlabSize, 0);
+
+    // We own the new slab and don't want anyone reading anyting other than
+    // pieces returned from this method.  So poison the whole slab.
+#if LLVM_ADDRESS_SANITIZER_BUILD
+    ASAN_POISON_MEMORY_REGION(NewSlab, AllocatedSlabSize);
+#endif
+
     Slabs.push_back(NewSlab);
     CurPtr = (char *)(NewSlab);
     End = ((char *)NewSlab) + AllocatedSlabSize;