diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -1577,6 +1577,28 @@
     "_ZnwmSt11align_val_t" for aligned ``::operator::new`` and
     ``::operator::delete``. Matching malloc/realloc/free calls within a family
     can be optimized, but mismatched ones will be left alone.
+``allockind("KIND")``
+    Describes the behavior of an allocation function. The KIND string is comma
+    separated entries from the following options:
+     * "new": the function returns a new block of memory, or null if the
+       allocation fails
+     * "resize": the function returns a new block of memory or null. If the
+       result is non-null the memory contents from the start of the block up to
+       the smaller of the original allocation size and the new allocation size
+       will match that of the ``allocptr`` argument and the ``allocptr``
+       argument is invalidated, even if the function returns the same address.
+     * "free": the function frees the block of memory specified by ``allocptr``
+     * "uninitialized": Any newly-allocated memory (either a new block from 
+       a "new" function or the enlarged capacity from a "resize" function) will
+       be uninitialized.
+     * "zeroed": Any newly-allocated memory (either a new block from a "new"
+       function or the enlarged capacity from a "resize" function) will be
+       zeroed.
+     * "aligned": the function returns memory aligned according to the 
+       ``allocalign`` parameter.
+    The first three options are mutually exclusive, and the remaining options
+    describe more details of how the function behaves. The remaining options
+    are ignored for "free"-type functions.
 ``allocsize(<EltSizeParam>[, <NumEltsParam>])``
     This attribute indicates that the annotated function will always return at
     least a given number of bytes (or null). Its arguments are zero-indexed
diff --git a/llvm/include/llvm/Analysis/MemoryBuiltins.h b/llvm/include/llvm/Analysis/MemoryBuiltins.h
--- a/llvm/include/llvm/Analysis/MemoryBuiltins.h
+++ b/llvm/include/llvm/Analysis/MemoryBuiltins.h
@@ -107,6 +107,9 @@
 /// the definition of the allocalign attribute.
 Value *getAllocAlignment(const CallBase *V, const TargetLibraryInfo *TLI);
 
+/// Gets the AllocKind information for a function.
+AllocFnKind getAllocKind(const CallBase *CB, const TargetLibraryInfo *TLI);
+
 /// Return the size of the requested allocation.  With a trivial mapper, this is
 /// identical to calling getObjectSize(..., Exact).  A mapper function can be
 /// used to replace one Value* (operand to the allocation) with another.  This
diff --git a/llvm/include/llvm/AsmParser/LLParser.h b/llvm/include/llvm/AsmParser/LLParser.h
--- a/llvm/include/llvm/AsmParser/LLParser.h
+++ b/llvm/include/llvm/AsmParser/LLParser.h
@@ -274,6 +274,7 @@
                                 bool AllowParens = false);
     bool parseOptionalDerefAttrBytes(lltok::Kind AttrKind, uint64_t &Bytes);
     bool parseOptionalUWTableKind(UWTableKind &Kind);
+    bool parseAllocKind(AllocFnKind &Kind);
     bool parseScopeAndOrdering(bool IsAtomic, SyncScope::ID &SSID,
                                AtomicOrdering &Ordering);
     bool parseScope(SyncScope::ID &SSID);
diff --git a/llvm/include/llvm/Bitcode/LLVMBitCodes.h b/llvm/include/llvm/Bitcode/LLVMBitCodes.h
--- a/llvm/include/llvm/Bitcode/LLVMBitCodes.h
+++ b/llvm/include/llvm/Bitcode/LLVMBitCodes.h
@@ -684,6 +684,7 @@
   ATTR_KIND_NO_SANITIZE_BOUNDS = 79,
   ATTR_KIND_ALLOC_ALIGN = 80,
   ATTR_KIND_ALLOCATED_POINTER = 81,
+  ATTR_KIND_ALLOC_KIND = 82,
 };
 
 enum ComdatSelectionKindCodes {
diff --git a/llvm/include/llvm/IR/Attributes.h b/llvm/include/llvm/IR/Attributes.h
--- a/llvm/include/llvm/IR/Attributes.h
+++ b/llvm/include/llvm/IR/Attributes.h
@@ -43,6 +43,18 @@
 class LLVMContext;
 class Type;
 
+enum class AllocFnKind : uint64_t {
+  Unknown = 0,
+  Alloc = 1 << 0,         // Allocator function returns a new allocation
+  Resize = 1 << 1,        // Allocator function resizes the `allocptr` argument
+  Free = 1 << 2,          // Allocator function frees the `allocptr` argument
+  Uninitialized = 1 << 3, // Allocator function returns uninitialized memory
+  Zeroed = 1 << 4,        // Allocator function returns zeroed memory
+  Aligned = 1 << 5,       // Allocator function aligns allocations per the
+                          // `allocalign` argument
+  LLVM_MARK_AS_BITMASK_ENUM(/* LargestValue = */ Aligned)
+};
+
 //===----------------------------------------------------------------------===//
 /// \class
 /// Functions, function parameters, and return types can have attributes
@@ -228,6 +240,9 @@
   // Returns the unwind table kind.
   UWTableKind getUWTableKind() const;
 
+  // Returns the allocator function kind.
+  AllocFnKind getAllocKind() const;
+
   /// The Attribute is converted to a string of equivalent mnemonic. This
   /// is, presumably, for writing out the mnemonics for the assembly writer.
   std::string getAsString(bool InAttrGrp = false) const;
@@ -359,6 +374,7 @@
   unsigned getVScaleRangeMin() const;
   Optional<unsigned> getVScaleRangeMax() const;
   UWTableKind getUWTableKind() const;
+  AllocFnKind getAllocKind() const;
   std::string getAsString(bool InAttrGrp = false) const;
 
   /// Return true if this attribute set belongs to the LLVMContext.
@@ -850,6 +866,8 @@
   /// Get the unwind table kind requested for the function.
   UWTableKind getUWTableKind() const;
 
+  AllocFnKind getAllocKind() const;
+
   /// Return the attributes at the index as a string.
   std::string getAsString(unsigned Index, bool InAttrGrp = false) const;
 
@@ -1203,6 +1221,9 @@
   /// Attribute.
   AttrBuilder &addUWTableAttr(UWTableKind Kind);
 
+  // This turns the allocator kind into the form used internally in Attribute.
+  AttrBuilder &addAllocKindAttr(AllocFnKind Kind);
+
   ArrayRef<Attribute> attrs() const { return Attrs; }
 
   bool operator==(const AttrBuilder &B) const;
diff --git a/llvm/include/llvm/IR/Attributes.td b/llvm/include/llvm/IR/Attributes.td
--- a/llvm/include/llvm/IR/Attributes.td
+++ b/llvm/include/llvm/IR/Attributes.td
@@ -51,6 +51,9 @@
 /// aligned_alloc and aligned ::operator::new.
 def AllocAlign: EnumAttr<"allocalign", [ParamAttr]>;
 
+/// Describes behavior of an allocator function in terms of known properties.
+def AllocKind: IntAttr<"allockind", [FnAttr]>;
+
 /// Parameter is the pointer to be manipulated by the allocator function.
 def AllocatedPointer : EnumAttr<"allocptr", [ParamAttr]>;
 
diff --git a/llvm/include/llvm/Support/CodeGen.h b/llvm/include/llvm/Support/CodeGen.h
--- a/llvm/include/llvm/Support/CodeGen.h
+++ b/llvm/include/llvm/Support/CodeGen.h
@@ -14,6 +14,10 @@
 #ifndef LLVM_SUPPORT_CODEGEN_H
 #define LLVM_SUPPORT_CODEGEN_H
 
+#include <cstdint>
+
+#include "llvm/ADT/BitmaskEnum.h"
+
 namespace llvm {
 
   // Relocation model types.
@@ -103,6 +107,7 @@
     Async = 2, ///< "Asynchronous" unwind tables (instr precise)
     Default = 2,
   };
+
   } // namespace llvm
 
 #endif
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -1360,6 +1360,13 @@
     B.addUWTableAttr(Kind);
     return false;
   }
+  case Attribute::AllocKind: {
+    AllocFnKind Kind = AllocFnKind::Unknown;
+    if (parseAllocKind(Kind))
+      return true;
+    B.addAllocKindAttr(Kind);
+    return false;
+  }
   default:
     B.addAttribute(Attr);
     Lex.Lex();
@@ -2039,6 +2046,40 @@
   return parseToken(lltok::rparen, "expected ')'");
 }
 
+bool LLParser::parseAllocKind(AllocFnKind &Kind) {
+  Lex.Lex();
+  LocTy ParenLoc = Lex.getLoc();
+  if (!EatIfPresent(lltok::lparen))
+    return error(ParenLoc, "expected '('");
+  LocTy KindLoc = Lex.getLoc();
+  std::string Arg;
+  if (parseStringConstant(Arg))
+    return error(KindLoc, "expected allockind value");
+  for (StringRef A : llvm::split(Arg, ",")) {
+    if (A == "alloc") {
+      Kind |= AllocFnKind::Alloc;
+    } else if (A == "resize") {
+      Kind |= AllocFnKind::Resize;
+    } else if (A == "free") {
+      Kind |= AllocFnKind::Free;
+    } else if (A == "uninitialized") {
+      Kind |= AllocFnKind::Uninitialized;
+    } else if (A == "zeroed") {
+      Kind |= AllocFnKind::Zeroed;
+    } else if (A == "aligned") {
+      Kind |= AllocFnKind::Aligned;
+    } else {
+      return error(KindLoc, Twine("unknown allockind ") + A);
+    }
+  }
+  ParenLoc = Lex.getLoc();
+  if (!EatIfPresent(lltok::rparen))
+    return error(ParenLoc, "expected ')'");
+  if (Kind == AllocFnKind::Unknown)
+    return error(KindLoc, "expected allockind value");
+  return false;
+}
+
 /// parseOptionalCommaAlign
 ///   ::=
 ///   ::= ',' align 4
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -1536,6 +1536,8 @@
     return Attribute::DereferenceableOrNull;
   case bitc::ATTR_KIND_ALLOC_ALIGN:
     return Attribute::AllocAlign;
+  case bitc::ATTR_KIND_ALLOC_KIND:
+    return Attribute::AllocKind;
   case bitc::ATTR_KIND_ALLOC_SIZE:
     return Attribute::AllocSize;
   case bitc::ATTR_KIND_ALLOCATED_POINTER:
@@ -1736,6 +1738,8 @@
             B.addVScaleRangeAttrFromRawRepr(Record[++i]);
           else if (Kind == Attribute::UWTable)
             B.addUWTableAttr(UWTableKind(Record[++i]));
+          else if (Kind == Attribute::AllocKind)
+            B.addAllocKindAttr(static_cast<AllocFnKind>(Record[++i]));
         } else if (Record[i] == 3 || Record[i] == 4) { // String attribute
           bool HasValue = (Record[i++] == 4);
           SmallString<64> KindStr;
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -649,6 +649,8 @@
     return bitc::ATTR_KIND_MIN_SIZE;
   case Attribute::AllocatedPointer:
     return bitc::ATTR_KIND_ALLOCATED_POINTER;
+  case Attribute::AllocKind:
+    return bitc::ATTR_KIND_ALLOC_KIND;
   case Attribute::Naked:
     return bitc::ATTR_KIND_NAKED;
   case Attribute::Nest:
diff --git a/llvm/lib/IR/AttributeImpl.h b/llvm/lib/IR/AttributeImpl.h
--- a/llvm/lib/IR/AttributeImpl.h
+++ b/llvm/lib/IR/AttributeImpl.h
@@ -256,6 +256,7 @@
   unsigned getVScaleRangeMin() const;
   Optional<unsigned> getVScaleRangeMax() const;
   UWTableKind getUWTableKind() const;
+  AllocFnKind getAllocKind() const;
   std::string getAsString(bool InAttrGrp) const;
   Type *getAttributeType(Attribute::AttrKind Kind) const;
 
diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -376,6 +376,12 @@
   return UWTableKind(pImpl->getValueAsInt());
 }
 
+AllocFnKind Attribute::getAllocKind() const {
+  assert(hasAttribute(Attribute::AllocKind) &&
+         "Trying to get allockind value from non-allockind attribute");
+  return AllocFnKind(pImpl->getValueAsInt());
+}
+
 std::string Attribute::getAsString(bool InAttrGrp) const {
   if (!pImpl) return {};
 
@@ -447,6 +453,32 @@
     }
   }
 
+  if (hasAttribute(Attribute::AllocKind)) {
+    AllocFnKind Kind = getAllocKind();
+    SmallVector<std::string> parts;
+    if ((Kind & AllocFnKind::Alloc) != AllocFnKind::Unknown) {
+      parts.push_back("alloc");
+    }
+    if ((Kind & AllocFnKind::Resize) != AllocFnKind::Unknown) {
+      parts.push_back("resize");
+    }
+    if ((Kind & AllocFnKind::Free) != AllocFnKind::Unknown) {
+      parts.push_back("free");
+    }
+    if ((Kind & AllocFnKind::Uninitialized) != AllocFnKind::Unknown) {
+      parts.push_back("uninitialized");
+    }
+    if ((Kind & AllocFnKind::Zeroed) != AllocFnKind::Unknown) {
+      parts.push_back("zeroed");
+    }
+    if ((Kind & AllocFnKind::Aligned) != AllocFnKind::Unknown) {
+      parts.push_back("aligned");
+    }
+    return ("allockind(\"" +
+            Twine(llvm::join(parts.begin(), parts.end(), ",")) + "\")")
+        .str();
+  }
+
   // Convert target-dependent attributes to strings of the form:
   //
   //   "kind"
@@ -735,6 +767,10 @@
   return SetNode ? SetNode->getUWTableKind() : UWTableKind::None;
 }
 
+AllocFnKind AttributeSet::getAllocKind() const {
+  return SetNode ? SetNode->getAllocKind() : AllocFnKind::Unknown;
+}
+
 std::string AttributeSet::getAsString(bool InAttrGrp) const {
   return SetNode ? SetNode->getAsString(InAttrGrp) : "";
 }
@@ -907,6 +943,12 @@
   return UWTableKind::None;
 }
 
+AllocFnKind AttributeSetNode::getAllocKind() const {
+  if (auto A = findEnumAttribute(Attribute::AllocKind))
+    return A->getAllocKind();
+  return AllocFnKind::Unknown;
+}
+
 std::string AttributeSetNode::getAsString(bool InAttrGrp) const {
   std::string Str;
   for (iterator I = begin(), E = end(); I != E; ++I) {
@@ -1463,6 +1505,10 @@
   return getFnAttrs().getUWTableKind();
 }
 
+AllocFnKind AttributeList::getAllocKind() const {
+  return getFnAttrs().getAllocKind();
+}
+
 std::string AttributeList::getAsString(unsigned Index, bool InAttrGrp) const {
   return getAttributes(Index).getAsString(InAttrGrp);
 }
@@ -1690,6 +1736,10 @@
   return addRawIntAttr(Attribute::UWTable, uint64_t(Kind));
 }
 
+AttrBuilder &AttrBuilder::addAllocKindAttr(AllocFnKind Kind) {
+  return addRawIntAttr(Attribute::AllocKind, static_cast<uint64_t>(Kind));
+}
+
 Type *AttrBuilder::getTypeAttr(Attribute::AttrKind Kind) const {
   assert(Attribute::isTypeAttrKind(Kind) && "Not a type attribute");
   Attribute A = getAttribute(Kind);
diff --git a/llvm/lib/Transforms/Utils/CodeExtractor.cpp b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
--- a/llvm/lib/Transforms/Utils/CodeExtractor.cpp
+++ b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
@@ -920,6 +920,7 @@
       case Attribute::StackAlignment:
       case Attribute::WillReturn:
       case Attribute::WriteOnly:
+      case Attribute::AllocKind:
         continue;
       // Those attributes should be safe to propagate to the extracted function.
       case Attribute::AlwaysInline:
diff --git a/llvm/test/Assembler/allockind-missing.ll b/llvm/test/Assembler/allockind-missing.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Assembler/allockind-missing.ll
@@ -0,0 +1,4 @@
+; RUN: not llvm-as %s -o /dev/null 2>&1 | FileCheck %s
+
+declare void @f0() allockind()
+; CHECK: :[[#@LINE-1]]:30: error: expected allockind value
diff --git a/llvm/test/Assembler/allockind.ll b/llvm/test/Assembler/allockind.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/Assembler/allockind.ll
@@ -0,0 +1,7 @@
+; RUN: not llvm-as %s -o /dev/null 2>&1 | FileCheck %s
+
+declare void @f0() allockind("free")
+declare void @f1() allockind("alloc,aligned,uninitialized")
+declare void @f2() allockind("resize,zeroed,aligned")
+declare void @f3() allockind("fjord")
+; CHECK: :[[#@LINE-1]]:30: error: unknown allockind fjord
diff --git a/llvm/test/Bitcode/compatibility.ll b/llvm/test/Bitcode/compatibility.ll
--- a/llvm/test/Bitcode/compatibility.ll
+++ b/llvm/test/Bitcode/compatibility.ll
@@ -1514,7 +1514,7 @@
   ; CHECK: select <2 x i1> <i1 true, i1 false>, <2 x i8> <i8 2, i8 3>, <2 x i8> <i8 3, i8 2>
 
   call void @f.nobuiltin() builtin
-  ; CHECK: call void @f.nobuiltin() #49
+  ; CHECK: call void @f.nobuiltin() #50
 
   call fastcc noalias i32* @f.noalias() noinline
   ; CHECK: call fastcc noalias i32* @f.noalias() #12
@@ -1937,6 +1937,9 @@
 declare void @f.nosanitize_bounds() nosanitize_bounds
 ; CHECK: declare void @f.nosanitize_bounds() #48
 
+declare void @f.allockind() allockind("alloc,uninitialized")
+; CHECK: declare void @f.allockind() #49
+
 ; CHECK: attributes #0 = { alignstack=4 }
 ; CHECK: attributes #1 = { alignstack=8 }
 ; CHECK: attributes #2 = { alwaysinline }
@@ -1986,7 +1989,8 @@
 ; CHECK: attributes #46 = { allocsize(0) }
 ; CHECK: attributes #47 = { allocsize(1,0) }
 ; CHECK: attributes #48 = { nosanitize_bounds }
-; CHECK: attributes #49 = { builtin }
+; CHECK: attributes #49 = { allockind("alloc,uninitialized") }
+; CHECK: attributes #50 = { builtin }
 
 ;; Metadata