diff --git a/llvm/include/llvm/Analysis/ObjCARCAnalysisUtils.h b/llvm/include/llvm/Analysis/ObjCARCAnalysisUtils.h
--- a/llvm/include/llvm/Analysis/ObjCARCAnalysisUtils.h
+++ b/llvm/include/llvm/Analysis/ObjCARCAnalysisUtils.h
@@ -151,9 +151,7 @@
     return false;
   // Special arguments can not be a valid retainable object pointer.
   if (const Argument *Arg = dyn_cast<Argument>(Op))
-    if (Arg->hasByValAttr() ||
-        Arg->hasInAllocaAttr() ||
-        Arg->hasNestAttr() ||
+    if (Arg->hasPassPointeeByValueAttr() || Arg->hasNestAttr() ||
         Arg->hasStructRetAttr())
       return false;
   // Only consider values with pointer types.
diff --git a/llvm/include/llvm/IR/Argument.h b/llvm/include/llvm/IR/Argument.h
--- a/llvm/include/llvm/IR/Argument.h
+++ b/llvm/include/llvm/IR/Argument.h
@@ -71,9 +71,9 @@
   /// Return true if this argument has the swifterror attribute.
   bool hasSwiftErrorAttr() const;
 
-  /// Return true if this argument has the byval attribute or inalloca
+  /// Return true if this argument has the byval, inalloca, or preallocated
   /// attribute. These attributes represent arguments being passed by value.
-  bool hasByValOrInAllocaAttr() const;
+  bool hasPassPointeeByValueAttr() const;
 
   /// If this is a byval or inalloca argument, return its alignment.
   /// FIXME: Remove this function once transition to Align is over.
diff --git a/llvm/include/llvm/IR/InstrTypes.h b/llvm/include/llvm/IR/InstrTypes.h
--- a/llvm/include/llvm/IR/InstrTypes.h
+++ b/llvm/include/llvm/IR/InstrTypes.h
@@ -1541,10 +1541,12 @@
     return paramHasAttr(ArgNo, Attribute::InAlloca);
   }
 
-  /// Determine whether this argument is passed by value or in an alloca.
-  bool isByValOrInAllocaArgument(unsigned ArgNo) const {
+  /// Determine whether this argument is passed by value, in an alloca, or is
+  /// preallocated.
+  bool isPassPointeeByValueArgument(unsigned ArgNo) const {
     return paramHasAttr(ArgNo, Attribute::ByVal) ||
-           paramHasAttr(ArgNo, Attribute::InAlloca);
+           paramHasAttr(ArgNo, Attribute::InAlloca) ||
+           paramHasAttr(ArgNo, Attribute::Preallocated);
   }
 
   /// Determine if there are is an inalloca argument. Only the last argument can
diff --git a/llvm/lib/Analysis/MemoryBuiltins.cpp b/llvm/lib/Analysis/MemoryBuiltins.cpp
--- a/llvm/lib/Analysis/MemoryBuiltins.cpp
+++ b/llvm/lib/Analysis/MemoryBuiltins.cpp
@@ -673,7 +673,7 @@
 
 SizeOffsetType ObjectSizeOffsetVisitor::visitArgument(Argument &A) {
   // No interprocedural analysis is done at the moment.
-  if (!A.hasByValOrInAllocaAttr()) {
+  if (!A.hasPassPointeeByValueAttr()) {
     ++ObjectVisitorArgument;
     return unknown();
   }
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -2339,7 +2339,7 @@
 
     // A byval, inalloca, or nonnull argument is never null.
     if (const Argument *A = dyn_cast<Argument>(V))
-      if (A->hasByValOrInAllocaAttr() || A->hasNonNullAttr())
+      if (A->hasPassPointeeByValueAttr() || A->hasNonNullAttr())
         return true;
 
     // A Load tagged with nonnull metadata is never null.
diff --git a/llvm/lib/IR/Function.cpp b/llvm/lib/IR/Function.cpp
--- a/llvm/lib/IR/Function.cpp
+++ b/llvm/lib/IR/Function.cpp
@@ -114,11 +114,12 @@
   return hasAttribute(Attribute::InAlloca);
 }
 
-bool Argument::hasByValOrInAllocaAttr() const {
+bool Argument::hasPassPointeeByValueAttr() const {
   if (!getType()->isPointerTy()) return false;
   AttributeList Attrs = getParent()->getAttributes();
   return Attrs.hasParamAttribute(getArgNo(), Attribute::ByVal) ||
-         Attrs.hasParamAttribute(getArgNo(), Attribute::InAlloca);
+         Attrs.hasParamAttribute(getArgNo(), Attribute::InAlloca) ||
+         Attrs.hasParamAttribute(getArgNo(), Attribute::Preallocated);
 }
 
 unsigned Argument::getParamAlignment() const {
diff --git a/llvm/lib/IR/Mangler.cpp b/llvm/lib/IR/Mangler.cpp
--- a/llvm/lib/IR/Mangler.cpp
+++ b/llvm/lib/IR/Mangler.cpp
@@ -98,7 +98,7 @@
        AI != AE; ++AI) {
     Type *Ty = AI->getType();
     // 'Dereference' type in case of byval or inalloca parameter attribute.
-    if (AI->hasByValOrInAllocaAttr())
+    if (AI->hasPassPointeeByValueAttr())
       Ty = cast<PointerType>(Ty)->getElementType();
     // Size should be aligned to pointer size.
     unsigned PtrSize = DL.getPointerSize();
diff --git a/llvm/lib/Target/ARM/ARMCallLowering.cpp b/llvm/lib/Target/ARM/ARMCallLowering.cpp
--- a/llvm/lib/Target/ARM/ARMCallLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMCallLowering.cpp
@@ -429,7 +429,7 @@
   for (auto &Arg : F.args()) {
     if (!isSupportedType(DL, TLI, Arg.getType()))
       return false;
-    if (Arg.hasByValOrInAllocaAttr())
+    if (Arg.hasPassPointeeByValueAttr())
       return false;
   }
 
diff --git a/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp b/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
--- a/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
+++ b/llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
@@ -289,7 +289,8 @@
   bool Changed = false;
 
   for (Argument &Arg : Fn.args()) {
-    if (!Arg.hasSwiftErrorAttr() && Arg.use_empty() && !Arg.hasByValOrInAllocaAttr()) {
+    if (!Arg.hasSwiftErrorAttr() && Arg.use_empty() &&
+        !Arg.hasPassPointeeByValueAttr()) {
       if (Arg.isUsedByMetadata()) {
         Arg.replaceAllUsesWith(UndefValue::get(Arg.getType()));
         Changed = true;
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -4336,7 +4336,7 @@
   // The size of ByVal or InAlloca arguments is derived from the type, so we
   // can't change to a type with a different size.  If the size were
   // passed explicitly we could avoid this check.
-  if (!Call.isByValOrInAllocaArgument(ix))
+  if (!Call.isPassPointeeByValueArgument(ix))
     return true;
 
   Type* SrcTy =
diff --git a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
--- a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -839,7 +839,7 @@
   // Treat byval or inalloca arguments the same, stores to them are dead at the
   // end of the function.
   for (Argument &AI : BB.getParent()->args())
-    if (AI.hasByValOrInAllocaAttr())
+    if (AI.hasPassPointeeByValueAttr())
       DeadStackObjects.insert(&AI);
 
   const DataLayout &DL = BB.getModule()->getDataLayout();
@@ -1549,7 +1549,7 @@
     // Treat byval or inalloca arguments the same as Allocas, stores to them are
     // dead at the end of the function.
     for (Argument &AI : F.args())
-      if (AI.hasByValOrInAllocaAttr())
+      if (AI.hasPassPointeeByValueAttr())
         State.InvisibleToCallerBeforeRet.insert(&AI);
     return State;
   }
diff --git a/llvm/lib/Transforms/Utils/InlineFunction.cpp b/llvm/lib/Transforms/Utils/InlineFunction.cpp
--- a/llvm/lib/Transforms/Utils/InlineFunction.cpp
+++ b/llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -1242,7 +1242,7 @@
   Function *CalledFunc = CB.getCalledFunction();
   for (Argument &Arg : CalledFunc->args()) {
     unsigned Align = Arg.getType()->isPointerTy() ? Arg.getParamAlignment() : 0;
-    if (Align && !Arg.hasByValOrInAllocaAttr() && !Arg.hasNUses(0)) {
+    if (Align && !Arg.hasPassPointeeByValueAttr() && !Arg.hasNUses(0)) {
       if (!DTCalculated) {
         DT.recalculate(*CB.getCaller());
         DTCalculated = true;