diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 840272df33fd..2105ce9d669f 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -1017,7 +1017,7 @@ Currently, only the following parameter attributes are defined:
     opposed to memory, though some targets use it to distinguish between
     two different kinds of registers). Use of this attribute is
     target-specific.
-``byval``
+``byval`` or ``byval(<ty>)``
     This indicates that the pointer parameter should really be passed by
     value to the function. The attribute implies that a hidden copy of
     the pointee is made between the caller and the callee, so the callee
@@ -1029,6 +1029,9 @@ Currently, only the following parameter attributes are defined:
     ``byval`` parameters). This is not a valid attribute for return
     values.
 
+    The byval attribute also supports an optional type argument, which must be
+    the same as the pointee type of the argument.
+
     The byval attribute also supports specifying an alignment with the
     align attribute. It indicates the alignment of the stack slot to
     form and the known alignment of the pointer specified to the call
diff --git a/llvm/docs/ReleaseNotes.rst b/llvm/docs/ReleaseNotes.rst
index 95fd43940b76..60a840eccef0 100644
--- a/llvm/docs/ReleaseNotes.rst
+++ b/llvm/docs/ReleaseNotes.rst
@@ -67,6 +67,11 @@ Changes to the LLVM IR
   type is now mandatory. Specify `i8* null` to migrate from the obsoleted
   2-field form.
 
+* The ``byval`` attribute can now take a type parameter:
+  ``byval(<ty>)``. If present it must be identical to the argument's
+  pointee type. In the next release we intend to make this parameter
+  mandatory in preparation for opaque pointer types.
+
 Changes to the ARM Backend
 --------------------------
 
diff --git a/llvm/include/llvm/CodeGen/TargetLowering.h b/llvm/include/llvm/CodeGen/TargetLowering.h
index cabca9cb2210..f06e01acae30 100644
--- a/llvm/include/llvm/CodeGen/TargetLowering.h
+++ b/llvm/include/llvm/CodeGen/TargetLowering.h
@@ -188,6 +188,7 @@ public:
     bool IsSwiftSelf : 1;
     bool IsSwiftError : 1;
     uint16_t Alignment = 0;
+    Type *ByValType = nullptr;
 
     ArgListEntry()
         : IsSExt(false), IsZExt(false), IsInReg(false), IsSRet(false),
diff --git a/llvm/include/llvm/IR/Argument.h b/llvm/include/llvm/IR/Argument.h
index 7997c863b830..952fbcdffb14 100644
--- a/llvm/include/llvm/IR/Argument.h
+++ b/llvm/include/llvm/IR/Argument.h
@@ -78,6 +78,9 @@ public:
   /// If this is a byval or inalloca argument, return its alignment.
   unsigned getParamAlignment() const;
 
+  /// If this is a byval argument, return its type.
+  Type *getParamByValType() const;
+
   /// Return true if this argument has the nest attribute.
   bool hasNestAttr() const;
 
diff --git a/llvm/include/llvm/IR/Attributes.h b/llvm/include/llvm/IR/Attributes.h
index 8d7f4018e846..06cc09e1cfc7 100644
--- a/llvm/include/llvm/IR/Attributes.h
+++ b/llvm/include/llvm/IR/Attributes.h
@@ -90,6 +90,7 @@ public:
   static Attribute get(LLVMContext &Context, AttrKind Kind, uint64_t Val = 0);
   static Attribute get(LLVMContext &Context, StringRef Kind,
                        StringRef Val = StringRef());
+  static Attribute get(LLVMContext &Context, AttrKind Kind, Type *Ty);
 
   /// Return a uniquified Attribute object that has the specific
   /// alignment set.
@@ -102,6 +103,7 @@ public:
   static Attribute getWithAllocSizeArgs(LLVMContext &Context,
                                         unsigned ElemSizeArg,
                                         const Optional<unsigned> &NumElemsArg);
+  static Attribute getWithByValType(LLVMContext &Context, Type *Ty);
 
   //===--------------------------------------------------------------------===//
   // Attribute Accessors
@@ -117,6 +119,9 @@ public:
   /// attribute.
   bool isStringAttribute() const;
 
+  /// Return true if the attribute is a type attribute.
+  bool isTypeAttribute() const;
+
   /// Return true if the attribute is present.
   bool hasAttribute(AttrKind Val) const;
 
@@ -139,6 +144,10 @@ public:
   /// attribute to be a string attribute.
   StringRef getValueAsString() const;
 
+  /// Return the attribute's value as a Type. This requires the attribute to be
+  /// a type attribute.
+  Type *getValueAsType() const;
+
   /// Returns the alignment field of an attribute as a byte alignment
   /// value.
   unsigned getAlignment() const;
@@ -279,6 +288,7 @@ public:
   unsigned getStackAlignment() const;
   uint64_t getDereferenceableBytes() const;
   uint64_t getDereferenceableOrNullBytes() const;
+  Type *getByValType() const;
   std::pair<unsigned, Optional<unsigned>> getAllocSizeArgs() const;
   std::string getAsString(bool InAttrGrp = false) const;
 
@@ -598,6 +608,9 @@ public:
   /// Return the alignment for the specified function parameter.
   unsigned getParamAlignment(unsigned ArgNo) const;
 
+  /// Return the byval type for the specified function parameter.
+  Type *getParamByValType(unsigned ArgNo) const;
+
   /// Get the stack alignment.
   unsigned getStackAlignment(unsigned Index) const;
 
@@ -697,6 +710,7 @@ class AttrBuilder {
   uint64_t DerefBytes = 0;
   uint64_t DerefOrNullBytes = 0;
   uint64_t AllocSizeArgs = 0;
+  Type *ByValType = nullptr;
 
 public:
   AttrBuilder() = default;
@@ -772,6 +786,9 @@ public:
   /// dereferenceable_or_null attribute exists (zero is returned otherwise).
   uint64_t getDereferenceableOrNullBytes() const { return DerefOrNullBytes; }
 
+  /// Retrieve the byval type.
+  Type *getByValType() const { return ByValType; }
+
   /// Retrieve the allocsize args, if the allocsize attribute exists.  If it
   /// doesn't exist, pair(0, 0) is returned.
   std::pair<unsigned, Optional<unsigned>> getAllocSizeArgs() const;
@@ -796,6 +813,9 @@ public:
   AttrBuilder &addAllocSizeAttr(unsigned ElemSizeArg,
                                 const Optional<unsigned> &NumElemsArg);
 
+  /// This turns a byval type into the form used internally in Attribute.
+  AttrBuilder &addByValAttr(Type *Ty);
+
   /// Add an allocsize attribute, using the representation returned by
   /// Attribute.getIntValue().
   AttrBuilder &addAllocSizeAttrFromRawRepr(uint64_t RawAllocSizeRepr);
diff --git a/llvm/include/llvm/IR/CallSite.h b/llvm/include/llvm/IR/CallSite.h
index 183e387a422e..b47a96c5d5fa 100644
--- a/llvm/include/llvm/IR/CallSite.h
+++ b/llvm/include/llvm/IR/CallSite.h
@@ -415,6 +415,11 @@ public:
     CALLSITE_DELEGATE_GETTER(getParamAlignment(ArgNo));
   }
 
+  /// Extract the byval type for a call or parameter (nullptr=unknown).
+  Type *getParamByValType(unsigned ArgNo) const {
+    CALLSITE_DELEGATE_GETTER(getParamByValType(ArgNo));
+  }
+
   /// Extract the number of dereferenceable bytes for a call or parameter
   /// (0=unknown).
   uint64_t getDereferenceableBytes(unsigned i) const {
diff --git a/llvm/include/llvm/IR/Function.h b/llvm/include/llvm/IR/Function.h
index 613d21bc64d2..896c2189eb82 100644
--- a/llvm/include/llvm/IR/Function.h
+++ b/llvm/include/llvm/IR/Function.h
@@ -431,6 +431,11 @@ public:
     return AttributeSets.getParamAlignment(ArgNo);
   }
 
+  /// Extract the byval type for a parameter (nullptr=unknown).
+  Type *getParamByValType(unsigned ArgNo) const {
+    return AttributeSets.getParamByValType(ArgNo);
+  }
+
   /// Extract the number of dereferenceable bytes for a call or
   /// parameter (0=unknown).
   /// @param i AttributeList index, referring to a return value or argument.
diff --git a/llvm/include/llvm/IR/InstrTypes.h b/llvm/include/llvm/IR/InstrTypes.h
index 7ffa7a6f60e8..6ce76811c0e6 100644
--- a/llvm/include/llvm/IR/InstrTypes.h
+++ b/llvm/include/llvm/IR/InstrTypes.h
@@ -1560,6 +1560,11 @@ public:
     return Attrs.getParamAlignment(ArgNo);
   }
 
+  /// Extract the byval type for a call or parameter (nullptr=unknown).
+  Type *getParamByValType(unsigned ArgNo) const {
+    return Attrs.getParamByValType(ArgNo);
+  }
+
   /// Extract the number of dereferenceable bytes for a call or
   /// parameter (0=unknown).
   uint64_t getDereferenceableBytes(unsigned i) const {
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 95646675cb27..0a9a09e644d7 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -1601,7 +1601,13 @@ bool LLParser::ParseOptionalParamAttrs(AttrBuilder &B) {
       B.addAlignmentAttr(Alignment);
       continue;
     }
-    case lltok::kw_byval:           B.addAttribute(Attribute::ByVal); break;
+    case lltok::kw_byval: {
+      Type *Ty;
+      if (ParseByValWithOptionalType(Ty))
+        return true;
+      B.addByValAttr(Ty);
+      continue;
+    }
     case lltok::kw_dereferenceable: {
       uint64_t Bytes;
       if (ParseOptionalDerefAttrBytes(lltok::kw_dereferenceable, Bytes))
@@ -2454,6 +2460,22 @@ bool LLParser::ParseParameterList(SmallVectorImpl<ParamInfo> &ArgList,
   return false;
 }
 
+/// ParseByValWithOptionalType
+///   ::= byval
+///   ::= byval(<ty>)
+bool LLParser::ParseByValWithOptionalType(Type *&Result) {
+  Result = nullptr;
+  if (!EatIfPresent(lltok::kw_byval))
+    return true;
+  if (!EatIfPresent(lltok::lparen))
+    return false;
+  if (ParseType(Result))
+    return true;
+  if (!EatIfPresent(lltok::rparen))
+    return Error(Lex.getLoc(), "expected ')'");
+  return false;
+}
+
 /// ParseOptionalOperandBundles
 ///    ::= /*empty*/
 ///    ::= '[' OperandBundle [, OperandBundle ]* ']'
diff --git a/llvm/lib/AsmParser/LLParser.h b/llvm/lib/AsmParser/LLParser.h
index ad169afb9358..ec4a61b5498d 100644
--- a/llvm/lib/AsmParser/LLParser.h
+++ b/llvm/lib/AsmParser/LLParser.h
@@ -339,6 +339,7 @@ namespace llvm {
     bool ParseFnAttributeValuePairs(AttrBuilder &B,
                                     std::vector<unsigned> &FwdRefAttrGrps,
                                     bool inAttrGrp, LocTy &BuiltinLoc);
+    bool ParseByValWithOptionalType(Type *&Result);
 
     // Module Summary Index Parsing.
     bool SkipModuleSummaryEntry();
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 134ce0367031..9f562ba82db9 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -638,6 +638,10 @@ private:
     return getFnValueByID(ValNo, Ty);
   }
 
+  /// Upgrades old-style typeless byval attributes by adding the corresponding
+  /// argument's pointee type.
+  void propagateByValTypes(CallBase *CB);
+
   /// Converts alignment exponent (i.e. power of two (or zero)) to the
   /// corresponding alignment to use. If alignment is too large, returns
   /// a corresponding error code.
@@ -1492,6 +1496,12 @@ Error BitcodeReader::parseAttributeGroupBlock() {
           if (Error Err = parseAttrKind(Record[++i], &Kind))
             return Err;
 
+          // Upgrade old-style byval attribute to one with a type, even if it's
+          // nullptr. We will have to insert the real type when we associate
+          // this AttributeList with a function.
+          if (Kind == Attribute::ByVal)
+            B.addByValAttr(nullptr);
+
           B.addAttribute(Kind);
         } else if (Record[i] == 1) { // Integer attribute
           Attribute::AttrKind Kind;
@@ -1507,9 +1517,7 @@ Error BitcodeReader::parseAttributeGroupBlock() {
             B.addDereferenceableOrNullAttr(Record[++i]);
           else if (Kind == Attribute::AllocSize)
             B.addAllocSizeAttrFromRawRepr(Record[++i]);
-        } else {                     // String attribute
-          assert((Record[i] == 3 || Record[i] == 4) &&
-                 "Invalid attribute group entry");
+        } else if (Record[i] == 3 || Record[i] == 4) { // String attribute
           bool HasValue = (Record[i++] == 4);
           SmallString<64> KindStr;
           SmallString<64> ValStr;
@@ -1527,6 +1535,15 @@ Error BitcodeReader::parseAttributeGroupBlock() {
           }
 
           B.addAttribute(KindStr.str(), ValStr.str());
+        } else {
+          assert((Record[i] == 5 || Record[i] == 6) &&
+                 "Invalid attribute group entry");
+          bool HasType = Record[i] == 6;
+          Attribute::AttrKind Kind;
+          if (Error Err = parseAttrKind(Record[++i], &Kind))
+            return Err;
+          if (Kind == Attribute::ByVal)
+            B.addByValAttr(HasType ? getTypeByID(Record[++i]) : nullptr);
         }
       }
 
@@ -3028,6 +3045,17 @@ Error BitcodeReader::parseFunctionRecord(ArrayRef<uint64_t> Record) {
   Func->setLinkage(getDecodedLinkage(RawLinkage));
   Func->setAttributes(getAttributes(Record[4]));
 
+  // Upgrade any old-style byval without a type by propagating the argument's
+  // pointee type. There should be no opaque pointers where the byval type is
+  // implicit.
+  for (auto &Arg : Func->args()) {
+    if (Arg.hasByValAttr() && !Arg.getParamByValType()) {
+      Arg.removeAttr(Attribute::ByVal);
+      Arg.addAttr(Attribute::getWithByValType(
+          Context, Arg.getType()->getPointerElementType()));
+    }
+  }
+
   unsigned Alignment;
   if (Error Err = parseAlignmentValue(Record[5], Alignment))
     return Err;
@@ -3441,6 +3469,19 @@ Error BitcodeReader::typeCheckLoadStoreInst(Type *ValType, Type *PtrType) {
   return Error::success();
 }
 
+void BitcodeReader::propagateByValTypes(CallBase *CB) {
+  for (unsigned i = 0; i < CB->getNumArgOperands(); ++i) {
+    if (CB->paramHasAttr(i, Attribute::ByVal) &&
+        !CB->getAttribute(i, Attribute::ByVal).getValueAsType()) {
+      CB->removeParamAttr(i, Attribute::ByVal);
+      CB->addParamAttr(
+          i, Attribute::getWithByValType(
+                 Context,
+                 CB->getArgOperand(i)->getType()->getPointerElementType()));
+    }
+  }
+}
+
 /// Lazily parse the specified function body block.
 Error BitcodeReader::parseFunctionBody(Function *F) {
   if (Stream.EnterSubBlock(bitc::FUNCTION_BLOCK_ID))
@@ -4256,6 +4297,8 @@ Error BitcodeReader::parseFunctionBody(Function *F) {
       cast<InvokeInst>(I)->setCallingConv(
           static_cast<CallingConv::ID>(CallingConv::MaxID & CCInfo));
       cast<InvokeInst>(I)->setAttributes(PAL);
+      propagateByValTypes(cast<CallBase>(I));
+
       break;
     }
     case bitc::FUNC_CODE_INST_RESUME: { // RESUME: [opval]
@@ -4731,6 +4774,7 @@ Error BitcodeReader::parseFunctionBody(Function *F) {
         TCK = CallInst::TCK_NoTail;
       cast<CallInst>(I)->setTailCallKind(TCK);
       cast<CallInst>(I)->setAttributes(PAL);
+      propagateByValTypes(cast<CallBase>(I));
       if (FMF.any()) {
         if (!isa<FPMathOperator>(I))
           return error("Fast-math-flags specified for call without "
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 8e1e06226bb4..d243815667fd 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -747,7 +747,7 @@ void ModuleBitcodeWriter::writeAttributeGroupTable() {
         Record.push_back(1);
         Record.push_back(getAttrKindEncoding(Attr.getKindAsEnum()));
         Record.push_back(Attr.getValueAsInt());
-      } else {
+      } else if (Attr.isStringAttribute()) {
         StringRef Kind = Attr.getKindAsString();
         StringRef Val = Attr.getValueAsString();
 
@@ -758,6 +758,13 @@ void ModuleBitcodeWriter::writeAttributeGroupTable() {
           Record.append(Val.begin(), Val.end());
           Record.push_back(0);
         }
+      } else {
+        assert(Attr.isTypeAttribute());
+        Type *Ty = Attr.getValueAsType();
+        Record.push_back(Ty ? 6 : 5);
+        Record.push_back(getAttrKindEncoding(Attr.getKindAsEnum()));
+        if (Ty)
+          Record.push_back(VE.getTypeID(Attr.getValueAsType()));
       }
     }
 
@@ -4126,15 +4133,15 @@ void ModuleBitcodeWriter::write() {
   // Emit blockinfo, which defines the standard abbreviations etc.
   writeBlockInfo();
 
+  // Emit information describing all of the types in the module.
+  writeTypeTable();
+
   // Emit information about attribute groups.
   writeAttributeGroupTable();
 
   // Emit information about parameter attributes.
   writeAttributeTable();
 
-  // Emit information describing all of the types in the module.
-  writeTypeTable();
-
   writeComdats();
 
   // Emit top-level description of module, including target triple, inline asm,
diff --git a/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp b/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp
index 72d7000fad9d..143570fb20a8 100644
--- a/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp
+++ b/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp
@@ -949,9 +949,11 @@ void ValueEnumerator::incorporateFunction(const Function &F) {
   incorporateFunctionMetadata(F);
 
   // Adding function arguments to the value table.
-  for (const auto &I : F.args())
+  for (const auto &I : F.args()) {
     EnumerateValue(&I);
-
+    if (I.hasAttribute(Attribute::ByVal) && I.getParamByValType())
+      EnumerateType(I.getParamByValType());
+  }
   FirstFuncConstantID = Values.size();
 
   // Add all function-level constants to the value table.
diff --git a/llvm/lib/CodeGen/GlobalISel/CallLowering.cpp b/llvm/lib/CodeGen/GlobalISel/CallLowering.cpp
index f144b18aa635..93727406a087 100644
--- a/llvm/lib/CodeGen/GlobalISel/CallLowering.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/CallLowering.cpp
@@ -87,7 +87,10 @@ void CallLowering::setArgFlags(CallLowering::ArgInfo &Arg, unsigned OpIdx,
 
   if (Arg.Flags.isByVal() || Arg.Flags.isInAlloca()) {
     Type *ElementTy = cast<PointerType>(Arg.Ty)->getElementType();
-    Arg.Flags.setByValSize(DL.getTypeAllocSize(ElementTy));
+
+    auto Ty = Attrs.getAttribute(OpIdx, Attribute::ByVal).getValueAsType();
+    Arg.Flags.setByValSize(DL.getTypeAllocSize(Ty ? Ty : ElementTy));
+
     // For ByVal, alignment should be passed from FE.  BE will guess if
     // this info is not there but there are cases it cannot get right.
     unsigned FrameAlign;
diff --git a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
index 8fb1a7b5bb9c..d887ed73c441 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -1204,9 +1204,11 @@ bool FastISel::lowerCallTo(CallLoweringInfo &CLI) {
     if (Arg.IsByVal || Arg.IsInAlloca) {
       PointerType *Ty = cast<PointerType>(Arg.Ty);
       Type *ElementTy = Ty->getElementType();
-      unsigned FrameSize = DL.getTypeAllocSize(ElementTy);
-      // For ByVal, alignment should come from FE. BE will guess if this info is
-      // not there, but there are cases it cannot get right.
+      unsigned FrameSize =
+          DL.getTypeAllocSize(Arg.ByValType ? Arg.ByValType : ElementTy);
+
+      // For ByVal, alignment should come from FE. BE will guess if this info
+      // is not there, but there are cases it cannot get right.
       unsigned FrameAlign = Arg.Alignment;
       if (!FrameAlign)
         FrameAlign = TLI.getByValTypeAlignment(ElementTy, DL);
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index fe857f73b254..da06ac7a414f 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -9076,8 +9076,11 @@ TargetLowering::LowerCallTo(TargetLowering::CallLoweringInfo &CLI) const {
       if (Args[i].IsByVal || Args[i].IsInAlloca) {
         PointerType *Ty = cast<PointerType>(Args[i].Ty);
         Type *ElementTy = Ty->getElementType();
-        Flags.setByValSize(DL.getTypeAllocSize(ElementTy));
-        // For ByVal, alignment should come from FE.  BE will guess if this
+
+        unsigned FrameSize = DL.getTypeAllocSize(
+            Args[i].ByValType ? Args[i].ByValType : ElementTy);
+        Flags.setByValSize(FrameSize);
+
         // info is not there but there are cases it cannot get right.
         unsigned FrameAlign;
         if (Args[i].Alignment)
@@ -9574,9 +9577,14 @@ void SelectionDAGISel::LowerArguments(const Function &F) {
       if (Flags.isByVal() || Flags.isInAlloca()) {
         PointerType *Ty = cast<PointerType>(Arg.getType());
         Type *ElementTy = Ty->getElementType();
-        Flags.setByValSize(DL.getTypeAllocSize(ElementTy));
-        // For ByVal, alignment should be passed from FE.  BE will guess if
-        // this info is not there but there are cases it cannot get right.
+
+        // For ByVal, size and alignment should be passed from FE.  BE will
+        // guess if this info is not there but there are cases it cannot get
+        // right.
+        unsigned FrameSize = DL.getTypeAllocSize(
+            Arg.getParamByValType() ? Arg.getParamByValType() : ElementTy);
+        Flags.setByValSize(FrameSize);
+
         unsigned FrameAlign;
         if (Arg.getParamAlignment())
           FrameAlign = Arg.getParamAlignment();
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index d636e613363e..4ad578d80fab 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -112,6 +112,7 @@ void TargetLoweringBase::ArgListEntry::setAttributes(const CallBase *Call,
   IsSwiftSelf = Call->paramHasAttr(ArgIdx, Attribute::SwiftSelf);
   IsSwiftError = Call->paramHasAttr(ArgIdx, Attribute::SwiftError);
   Alignment = Call->getParamAlignment(ArgIdx);
+  ByValType = Call->getParamByValType(ArgIdx);
 }
 
 /// Generate a libcall taking the given operands as arguments and returning a
diff --git a/llvm/lib/IR/AttributeImpl.h b/llvm/lib/IR/AttributeImpl.h
index 8ebcb04a565d..f6898476382d 100644
--- a/llvm/lib/IR/AttributeImpl.h
+++ b/llvm/lib/IR/AttributeImpl.h
@@ -29,6 +29,7 @@
 namespace llvm {
 
 class LLVMContext;
+class Type;
 
 //===----------------------------------------------------------------------===//
 /// \class
@@ -41,7 +42,8 @@ protected:
   enum AttrEntryKind {
     EnumAttrEntry,
     IntAttrEntry,
-    StringAttrEntry
+    StringAttrEntry,
+    TypeAttrEntry,
   };
 
   AttributeImpl(AttrEntryKind KindID) : KindID(KindID) {}
@@ -56,6 +58,7 @@ public:
   bool isEnumAttribute() const { return KindID == EnumAttrEntry; }
   bool isIntAttribute() const { return KindID == IntAttrEntry; }
   bool isStringAttribute() const { return KindID == StringAttrEntry; }
+  bool isTypeAttribute() const { return KindID == TypeAttrEntry; }
 
   bool hasAttribute(Attribute::AttrKind A) const;
   bool hasAttribute(StringRef Kind) const;
@@ -66,16 +69,20 @@ public:
   StringRef getKindAsString() const;
   StringRef getValueAsString() const;
 
+  Type *getValueAsType() const;
+
   /// Used when sorting the attributes.
   bool operator<(const AttributeImpl &AI) const;
 
   void Profile(FoldingSetNodeID &ID) const {
     if (isEnumAttribute())
-      Profile(ID, getKindAsEnum(), 0);
+      Profile(ID, getKindAsEnum(), static_cast<uint64_t>(0));
     else if (isIntAttribute())
       Profile(ID, getKindAsEnum(), getValueAsInt());
-    else
+    else if (isStringAttribute())
       Profile(ID, getKindAsString(), getValueAsString());
+    else
+      Profile(ID, getKindAsEnum(), getValueAsType());
   }
 
   static void Profile(FoldingSetNodeID &ID, Attribute::AttrKind Kind,
@@ -88,6 +95,12 @@ public:
     ID.AddString(Kind);
     if (!Values.empty()) ID.AddString(Values);
   }
+
+  static void Profile(FoldingSetNodeID &ID, Attribute::AttrKind Kind,
+                      Type *Ty) {
+    ID.AddInteger(Kind);
+    ID.AddPointer(Ty);
+  }
 };
 
 //===----------------------------------------------------------------------===//
@@ -145,6 +158,18 @@ public:
   StringRef getStringValue() const { return Val; }
 };
 
+class TypeAttributeImpl : public EnumAttributeImpl {
+  virtual void anchor();
+
+  Type *Ty;
+
+public:
+  TypeAttributeImpl(Attribute::AttrKind Kind, Type *Ty)
+      : EnumAttributeImpl(TypeAttrEntry, Kind), Ty(Ty) {}
+
+  Type *getTypeValue() const { return Ty; }
+};
+
 //===----------------------------------------------------------------------===//
 /// \class
 /// This class represents a group of attributes that apply to one
@@ -189,6 +214,7 @@ public:
   uint64_t getDereferenceableOrNullBytes() const;
   std::pair<unsigned, Optional<unsigned>> getAllocSizeArgs() const;
   std::string getAsString(bool InAttrGrp) const;
+  Type *getByValType() const;
 
   using iterator = const Attribute *;
 
diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
index 0be09a05e82a..67d35def9ffd 100644
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -121,6 +121,27 @@ Attribute Attribute::get(LLVMContext &Context, StringRef Kind, StringRef Val) {
   return Attribute(PA);
 }
 
+Attribute Attribute::get(LLVMContext &Context, Attribute::AttrKind Kind,
+                         Type *Ty) {
+  LLVMContextImpl *pImpl = Context.pImpl;
+  FoldingSetNodeID ID;
+  ID.AddInteger(Kind);
+  ID.AddPointer(Ty);
+
+  void *InsertPoint;
+  AttributeImpl *PA = pImpl->AttrsSet.FindNodeOrInsertPos(ID, InsertPoint);
+
+  if (!PA) {
+    // If we didn't find any existing attributes of the same shape then create a
+    // new one and insert it.
+    PA = new TypeAttributeImpl(Kind, Ty);
+    pImpl->AttrsSet.InsertNode(PA, InsertPoint);
+  }
+
+  // Return the Attribute that we found or created.
+  return Attribute(PA);
+}
+
 Attribute Attribute::getWithAlignment(LLVMContext &Context, uint64_t Align) {
   assert(isPowerOf2_32(Align) && "Alignment must be a power of two.");
   assert(Align <= 0x40000000 && "Alignment too large.");
@@ -146,6 +167,10 @@ Attribute Attribute::getWithDereferenceableOrNullBytes(LLVMContext &Context,
   return get(Context, DereferenceableOrNull, Bytes);
 }
 
+Attribute Attribute::getWithByValType(LLVMContext &Context, Type *Ty) {
+  return get(Context, ByVal, Ty);
+}
+
 Attribute
 Attribute::getWithAllocSizeArgs(LLVMContext &Context, unsigned ElemSizeArg,
                                 const Optional<unsigned> &NumElemsArg) {
@@ -170,9 +195,13 @@ bool Attribute::isStringAttribute() const {
   return pImpl && pImpl->isStringAttribute();
 }
 
+bool Attribute::isTypeAttribute() const {
+  return pImpl && pImpl->isTypeAttribute();
+}
+
 Attribute::AttrKind Attribute::getKindAsEnum() const {
   if (!pImpl) return None;
-  assert((isEnumAttribute() || isIntAttribute()) &&
+  assert((isEnumAttribute() || isIntAttribute() || isTypeAttribute()) &&
          "Invalid attribute type to get the kind as an enum!");
   return pImpl->getKindAsEnum();
 }
@@ -198,6 +227,14 @@ StringRef Attribute::getValueAsString() const {
   return pImpl->getValueAsString();
 }
 
+Type *Attribute::getValueAsType() const {
+  if (!pImpl) return {};
+  assert(isTypeAttribute() &&
+         "Invalid attribute type to get the value as a type!");
+  return pImpl->getValueAsType();
+}
+
+
 bool Attribute::hasAttribute(AttrKind Kind) const {
   return (pImpl && pImpl->hasAttribute(Kind)) || (!pImpl && Kind == None);
 }
@@ -252,8 +289,6 @@ std::string Attribute::getAsString(bool InAttrGrp) const {
     return "argmemonly";
   if (hasAttribute(Attribute::Builtin))
     return "builtin";
-  if (hasAttribute(Attribute::ByVal))
-    return "byval";
   if (hasAttribute(Attribute::Convergent))
     return "convergent";
   if (hasAttribute(Attribute::SwiftError))
@@ -353,6 +388,19 @@ std::string Attribute::getAsString(bool InAttrGrp) const {
   if (hasAttribute(Attribute::ImmArg))
     return "immarg";
 
+  if (hasAttribute(Attribute::ByVal)) {
+    std::string Result;
+    Result += "byval";
+    if (Type *Ty = getValueAsType()) {
+      raw_string_ostream OS(Result);
+      Result += '(';
+      Ty->print(OS, false, true);
+      OS.flush();
+      Result += ')';
+    }
+    return Result;
+  }
+
   // FIXME: These should be output like this:
   //
   //   align=4
@@ -451,6 +499,8 @@ void IntAttributeImpl::anchor() {}
 
 void StringAttributeImpl::anchor() {}
 
+void TypeAttributeImpl::anchor() {}
+
 bool AttributeImpl::hasAttribute(Attribute::AttrKind A) const {
   if (isStringAttribute()) return false;
   return getKindAsEnum() == A;
@@ -462,7 +512,7 @@ bool AttributeImpl::hasAttribute(StringRef Kind) const {
 }
 
 Attribute::AttrKind AttributeImpl::getKindAsEnum() const {
-  assert(isEnumAttribute() || isIntAttribute());
+  assert(isEnumAttribute() || isIntAttribute() || isTypeAttribute());
   return static_cast<const EnumAttributeImpl *>(this)->getEnumKind();
 }
 
@@ -481,6 +531,11 @@ StringRef AttributeImpl::getValueAsString() const {
   return static_cast<const StringAttributeImpl *>(this)->getStringValue();
 }
 
+Type *AttributeImpl::getValueAsType() const {
+  assert(isTypeAttribute());
+  return static_cast<const TypeAttributeImpl *>(this)->getTypeValue();
+}
+
 bool AttributeImpl::operator<(const AttributeImpl &AI) const {
   // This sorts the attributes with Attribute::AttrKinds coming first (sorted
   // relative to their enum value) and then strings.
@@ -488,10 +543,23 @@ bool AttributeImpl::operator<(const AttributeImpl &AI) const {
     if (AI.isEnumAttribute()) return getKindAsEnum() < AI.getKindAsEnum();
     if (AI.isIntAttribute()) return true;
     if (AI.isStringAttribute()) return true;
+    if (AI.isTypeAttribute()) return true;
+  }
+
+  if (isTypeAttribute()) {
+    if (AI.isEnumAttribute()) return false;
+    if (AI.isTypeAttribute()) {
+      assert(getKindAsEnum() != AI.getKindAsEnum() &&
+             "Comparison of types would be unstable");
+      return getKindAsEnum() < AI.getKindAsEnum();
+    }
+    if (AI.isIntAttribute()) return true;
+    if (AI.isStringAttribute()) return true;
   }
 
   if (isIntAttribute()) {
     if (AI.isEnumAttribute()) return false;
+    if (AI.isTypeAttribute()) return false;
     if (AI.isIntAttribute()) {
       if (getKindAsEnum() == AI.getKindAsEnum())
         return getValueAsInt() < AI.getValueAsInt();
@@ -500,7 +568,9 @@ bool AttributeImpl::operator<(const AttributeImpl &AI) const {
     if (AI.isStringAttribute()) return true;
   }
 
+  assert(isStringAttribute());
   if (AI.isEnumAttribute()) return false;
+  if (AI.isTypeAttribute()) return false;
   if (AI.isIntAttribute()) return false;
   if (getKindAsString() == AI.getKindAsString())
     return getValueAsString() < AI.getValueAsString();
@@ -608,6 +678,10 @@ uint64_t AttributeSet::getDereferenceableOrNullBytes() const {
   return SetNode ? SetNode->getDereferenceableOrNullBytes() : 0;
 }
 
+Type *AttributeSet::getByValType() const {
+  return SetNode ? SetNode->getByValType() : nullptr;
+}
+
 std::pair<unsigned, Optional<unsigned>> AttributeSet::getAllocSizeArgs() const {
   return SetNode ? SetNode->getAllocSizeArgs()
                  : std::pair<unsigned, Optional<unsigned>>(0, 0);
@@ -691,6 +765,9 @@ AttributeSetNode *AttributeSetNode::get(LLVMContext &C, const AttrBuilder &B) {
 
     Attribute Attr;
     switch (Kind) {
+    case Attribute::ByVal:
+      Attr = Attribute::getWithByValType(C, B.getByValType());
+      break;
     case Attribute::Alignment:
       Attr = Attribute::getWithAlignment(C, B.getAlignment());
       break;
@@ -760,6 +837,13 @@ unsigned AttributeSetNode::getStackAlignment() const {
   return 0;
 }
 
+Type *AttributeSetNode::getByValType() const {
+  for (const auto I : *this)
+    if (I.hasAttribute(Attribute::ByVal))
+      return I.getValueAsType();
+  return 0;
+}
+
 uint64_t AttributeSetNode::getDereferenceableBytes() const {
   for (const auto I : *this)
     if (I.hasAttribute(Attribute::Dereferenceable))
@@ -1258,6 +1342,11 @@ unsigned AttributeList::getParamAlignment(unsigned ArgNo) const {
   return getAttributes(ArgNo + FirstArgIndex).getAlignment();
 }
 
+Type *AttributeList::getParamByValType(unsigned Index) const {
+  return getAttributes(Index+FirstArgIndex).getByValType();
+}
+
+
 unsigned AttributeList::getStackAlignment(unsigned Index) const {
   return getAttributes(Index).getStackAlignment();
 }
@@ -1336,6 +1425,7 @@ void AttrBuilder::clear() {
   TargetDepAttrs.clear();
   Alignment = StackAlignment = DerefBytes = DerefOrNullBytes = 0;
   AllocSizeArgs = 0;
+  ByValType = nullptr;
 }
 
 AttrBuilder &AttrBuilder::addAttribute(Attribute::AttrKind Val) {
@@ -1360,6 +1450,8 @@ AttrBuilder &AttrBuilder::addAttribute(Attribute Attr) {
     Alignment = Attr.getAlignment();
   else if (Kind == Attribute::StackAlignment)
     StackAlignment = Attr.getStackAlignment();
+  else if (Kind == Attribute::ByVal)
+    ByValType = Attr.getValueAsType();
   else if (Kind == Attribute::Dereferenceable)
     DerefBytes = Attr.getDereferenceableBytes();
   else if (Kind == Attribute::DereferenceableOrNull)
@@ -1382,6 +1474,8 @@ AttrBuilder &AttrBuilder::removeAttribute(Attribute::AttrKind Val) {
     Alignment = 0;
   else if (Val == Attribute::StackAlignment)
     StackAlignment = 0;
+  else if (Val == Attribute::ByVal)
+    ByValType = nullptr;
   else if (Val == Attribute::Dereferenceable)
     DerefBytes = 0;
   else if (Val == Attribute::DereferenceableOrNull)
@@ -1464,6 +1558,12 @@ AttrBuilder &AttrBuilder::addAllocSizeAttrFromRawRepr(uint64_t RawArgs) {
   return *this;
 }
 
+AttrBuilder &AttrBuilder::addByValAttr(Type *Ty) {
+  Attrs[Attribute::ByVal] = true;
+  ByValType = Ty;
+  return *this;
+}
+
 AttrBuilder &AttrBuilder::merge(const AttrBuilder &B) {
   // FIXME: What if both have alignments, but they don't match?!
   if (!Alignment)
@@ -1481,6 +1581,9 @@ AttrBuilder &AttrBuilder::merge(const AttrBuilder &B) {
   if (!AllocSizeArgs)
     AllocSizeArgs = B.AllocSizeArgs;
 
+  if (!ByValType)
+    ByValType = B.ByValType;
+
   Attrs |= B.Attrs;
 
   for (auto I : B.td_attrs())
@@ -1506,6 +1609,9 @@ AttrBuilder &AttrBuilder::remove(const AttrBuilder &B) {
   if (B.AllocSizeArgs)
     AllocSizeArgs = 0;
 
+  if (B.ByValType)
+    ByValType = nullptr;
+
   Attrs &= ~B.Attrs;
 
   for (auto I : B.td_attrs())
@@ -1565,7 +1671,7 @@ bool AttrBuilder::operator==(const AttrBuilder &B) {
       return false;
 
   return Alignment == B.Alignment && StackAlignment == B.StackAlignment &&
-         DerefBytes == B.DerefBytes;
+         DerefBytes == B.DerefBytes && ByValType == B.ByValType;
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/llvm/lib/IR/Function.cpp b/llvm/lib/IR/Function.cpp
index b00deb677b31..a4a78ca4deb9 100644
--- a/llvm/lib/IR/Function.cpp
+++ b/llvm/lib/IR/Function.cpp
@@ -113,6 +113,11 @@ unsigned Argument::getParamAlignment() const {
   return getParent()->getParamAlignment(getArgNo());
 }
 
+Type *Argument::getParamByValType() const {
+  assert(getType()->isPointerTy() && "Only pointers have byval types");
+  return getParent()->getParamByValType(getArgNo());
+}
+
 uint64_t Argument::getDereferenceableBytes() const {
   assert(getType()->isPointerTy() &&
          "Only pointers have dereferenceable bytes");
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
index d5c3287e7134..963bf82c9898 100644
--- a/llvm/lib/IR/Verifier.cpp
+++ b/llvm/lib/IR/Verifier.cpp
@@ -1695,6 +1695,11 @@ void Verifier::verifyParameterAttrs(AttributeSet Attrs, Type *Ty,
          "'noinline and alwaysinline' are incompatible!",
          V);
 
+  if (Attrs.hasAttribute(Attribute::ByVal) && Attrs.getByValType()) {
+    Assert(Attrs.getByValType() == cast<PointerType>(Ty)->getElementType(),
+           "Attribute 'byval' type does not match parameter!");
+  }
+
   AttrBuilder IncompatibleAttrs = AttributeFuncs::typeIncompatible(Ty);
   Assert(!AttrBuilder(Attrs).overlaps(IncompatibleAttrs),
          "Wrong types for attribute: " +
diff --git a/llvm/lib/Linker/IRMover.cpp b/llvm/lib/Linker/IRMover.cpp
index 7635092dd434..37515d93ed50 100644
--- a/llvm/lib/Linker/IRMover.cpp
+++ b/llvm/lib/Linker/IRMover.cpp
@@ -489,6 +489,10 @@ class IRLinker {
   void linkAliasBody(GlobalAlias &Dst, GlobalAlias &Src);
   Error linkGlobalValueBody(GlobalValue &Dst, GlobalValue &Src);
 
+  /// Replace all types in the source AttributeList with the
+  /// corresponding destination type.
+  AttributeList mapAttributeTypes(LLVMContext &C, AttributeList Attrs);
+
   /// Functions that take care of cloning a specific global value type
   /// into the destination module.
   GlobalVariable *copyGlobalVariableProto(const GlobalVariable *SGVar);
@@ -628,6 +632,21 @@ GlobalVariable *IRLinker::copyGlobalVariableProto(const GlobalVariable *SGVar) {
   return NewDGV;
 }
 
+AttributeList IRLinker::mapAttributeTypes(LLVMContext &C, AttributeList Attrs) {
+  for (unsigned i = 0; i < Attrs.getNumAttrSets(); ++i) {
+    if (Attrs.hasAttribute(i, Attribute::ByVal)) {
+      Type *Ty = Attrs.getAttribute(i, Attribute::ByVal).getValueAsType();
+      if (!Ty)
+        continue;
+
+      Attrs = Attrs.removeAttribute(C, i, Attribute::ByVal);
+      Attrs = Attrs.addAttribute(
+          C, i, Attribute::getWithByValType(C, TypeMap.get(Ty)));
+    }
+  }
+  return Attrs;
+}
+
 /// Link the function in the source module into the destination module if
 /// needed, setting up mapping information.
 Function *IRLinker::copyFunctionProto(const Function *SF) {
@@ -637,6 +656,7 @@ Function *IRLinker::copyFunctionProto(const Function *SF) {
       Function::Create(TypeMap.get(SF->getFunctionType()),
                        GlobalValue::ExternalLinkage, SF->getName(), &DstM);
   F->copyAttributesFrom(SF);
+  F->setAttributes(mapAttributeTypes(F->getContext(), F->getAttributes()));
   return F;
 }
 
diff --git a/llvm/lib/Transforms/Utils/ValueMapper.cpp b/llvm/lib/Transforms/Utils/ValueMapper.cpp
index 1710f97d2340..fbc3407c301f 100644
--- a/llvm/lib/Transforms/Utils/ValueMapper.cpp
+++ b/llvm/lib/Transforms/Utils/ValueMapper.cpp
@@ -913,6 +913,21 @@ void Mapper::remapInstruction(Instruction *I) {
       Tys.push_back(TypeMapper->remapType(Ty));
     CS.mutateFunctionType(FunctionType::get(
         TypeMapper->remapType(I->getType()), Tys, FTy->isVarArg()));
+
+    LLVMContext &C = CS->getContext();
+    AttributeList Attrs = CS.getAttributes();
+    for (unsigned i = 0; i < Attrs.getNumAttrSets(); ++i) {
+      if (Attrs.hasAttribute(i, Attribute::ByVal)) {
+        Type *Ty = Attrs.getAttribute(i, Attribute::ByVal).getValueAsType();
+        if (!Ty)
+          continue;
+
+        Attrs = Attrs.removeAttribute(C, i, Attribute::ByVal);
+        Attrs = Attrs.addAttribute(
+            C, i, Attribute::getWithByValType(C, TypeMapper->remapType(Ty)));
+      }
+    }
+    CS.setAttributes(Attrs);
     return;
   }
   if (auto *AI = dyn_cast<AllocaInst>(I))
diff --git a/llvm/test/Assembler/byval-type-attr.ll b/llvm/test/Assembler/byval-type-attr.ll
new file mode 100644
index 000000000000..eb17a30db3b2
--- /dev/null
+++ b/llvm/test/Assembler/byval-type-attr.ll
@@ -0,0 +1,31 @@
+; RUN: llvm-as < %s | llvm-dis | llvm-as | llvm-dis | FileCheck %s
+
+; CHECK: define void @foo(i32* byval(i32) align 4)
+define void @foo(i32* byval(i32) align 4) {
+  ret void
+}
+
+; CHECK: define void @bar({ i32*, i8 }* byval({ i32*, i8 }) align 4)
+define void @bar({i32*, i8}* byval({i32*, i8}) align 4) {
+  ret void
+}
+
+define void @caller({ i32*, i8 }* %ptr) personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
+; CHECK: call void @bar({ i32*, i8 }* byval({ i32*, i8 }) %ptr)
+; CHECK: invoke void @bar({ i32*, i8 }* byval({ i32*, i8 }) %ptr)
+  call void @bar({i32*, i8}* byval %ptr)
+  invoke void @bar({i32*, i8}* byval %ptr) to label %success unwind label %fail
+
+success:
+  ret void
+
+fail:
+  landingpad { i8*, i32 } cleanup
+  ret void
+}
+
+; CHECK: declare void @baz([8 x i8]* byval([8 x i8]))
+%named_type = type [8 x i8]
+declare void @baz(%named_type* byval(%named_type))
+
+declare i32 @__gxx_personality_v0(...)
diff --git a/llvm/test/Assembler/invalid-byval-type1.ll b/llvm/test/Assembler/invalid-byval-type1.ll
new file mode 100644
index 000000000000..236790e11428
--- /dev/null
+++ b/llvm/test/Assembler/invalid-byval-type1.ll
@@ -0,0 +1,4 @@
+; RUN: not llvm-as %s -o /dev/null 2>&1 | FileCheck %s
+
+; CHECK: Attribute 'byval' type does not match parameter!
+declare void @foo(i32* byval(i8))
diff --git a/llvm/test/Assembler/invalid-byval-type2.ll b/llvm/test/Assembler/invalid-byval-type2.ll
new file mode 100644
index 000000000000..3ca0d5e7c4c2
--- /dev/null
+++ b/llvm/test/Assembler/invalid-byval-type2.ll
@@ -0,0 +1,4 @@
+; RUN: not llvm-as %s -o /dev/null 2>&1 | FileCheck %s
+
+; CHECK: error: void type only allowed for function results
+declare void @foo(i32* byval(void))
diff --git a/llvm/test/Assembler/invalid-byval-type3.ll b/llvm/test/Assembler/invalid-byval-type3.ll
new file mode 100644
index 000000000000..4626dd71c5b5
--- /dev/null
+++ b/llvm/test/Assembler/invalid-byval-type3.ll
@@ -0,0 +1,4 @@
+; RUN: not llvm-as %s -o /dev/null 2>&1 | FileCheck %s
+
+; CHECK: Attributes 'byval' and 'inalloca' do not support unsized types!
+declare void @foo(void()* byval(void()))
diff --git a/llvm/test/Bitcode/Inputs/byval-upgrade.bc b/llvm/test/Bitcode/Inputs/byval-upgrade.bc
new file mode 100644
index 000000000000..e0da41f78e77
Binary files /dev/null and b/llvm/test/Bitcode/Inputs/byval-upgrade.bc differ
diff --git a/llvm/test/Bitcode/attributes-3.3.ll b/llvm/test/Bitcode/attributes-3.3.ll
index b564425c3738..f1b37d199122 100644
--- a/llvm/test/Bitcode/attributes-3.3.ll
+++ b/llvm/test/Bitcode/attributes-3.3.ll
@@ -48,7 +48,7 @@ define void @f7(i8* noalias)
 }
 
 define void @f8(i8* byval)
-; CHECK: define void @f8(i8* byval)
+; CHECK: define void @f8(i8* byval(i8))
 {
         ret void;
 }
diff --git a/llvm/test/Bitcode/attributes.ll b/llvm/test/Bitcode/attributes.ll
index de3cf8dd4d73..6f149c0d3bf7 100644
--- a/llvm/test/Bitcode/attributes.ll
+++ b/llvm/test/Bitcode/attributes.ll
@@ -45,7 +45,7 @@ define void @f7(i8* noalias)
 }
 
 define void @f8(i8* byval)
-; CHECK: define void @f8(i8* byval)
+; CHECK: define void @f8(i8* byval(i8))
 {
         ret void;
 }
diff --git a/llvm/test/Bitcode/byval-upgrade.test b/llvm/test/Bitcode/byval-upgrade.test
new file mode 100644
index 000000000000..1012bf728830
--- /dev/null
+++ b/llvm/test/Bitcode/byval-upgrade.test
@@ -0,0 +1,7 @@
+RUN: llvm-dis %p/Inputs/byval-upgrade.bc -o - | FileCheck %s
+
+Make sure we upgrade old-stile IntAttribute byval records to a fully typed
+version correctly.
+
+CHECK: call void @bar({ i32*, i8 }* byval({ i32*, i8 }) %ptr)
+CHECK: invoke void @bar({ i32*, i8 }* byval({ i32*, i8 }) %ptr)
diff --git a/llvm/test/Bitcode/compatibility-3.6.ll b/llvm/test/Bitcode/compatibility-3.6.ll
index e9313dfba870..322c95b02d1f 100644
--- a/llvm/test/Bitcode/compatibility-3.6.ll
+++ b/llvm/test/Bitcode/compatibility-3.6.ll
@@ -404,7 +404,7 @@ declare void @f.param.signext(i8 signext)
 declare void @f.param.inreg(i8 inreg)
 ; CHECK: declare void @f.param.inreg(i8 inreg)
 declare void @f.param.byval({ i8, i8 }* byval)
-; CHECK: declare void @f.param.byval({ i8, i8 }* byval)
+; CHECK: declare void @f.param.byval({ i8, i8 }* byval({ i8, i8 }))
 declare void @f.param.inalloca(i8* inalloca)
 ; CHECK: declare void @f.param.inalloca(i8* inalloca)
 declare void @f.param.sret(i8* sret)
diff --git a/llvm/test/Bitcode/compatibility-3.7.ll b/llvm/test/Bitcode/compatibility-3.7.ll
index 82fc99055357..e8260741373d 100644
--- a/llvm/test/Bitcode/compatibility-3.7.ll
+++ b/llvm/test/Bitcode/compatibility-3.7.ll
@@ -410,7 +410,7 @@ declare void @f.param.signext(i8 signext)
 declare void @f.param.inreg(i8 inreg)
 ; CHECK: declare void @f.param.inreg(i8 inreg)
 declare void @f.param.byval({ i8, i8 }* byval)
-; CHECK: declare void @f.param.byval({ i8, i8 }* byval)
+; CHECK: declare void @f.param.byval({ i8, i8 }* byval({ i8, i8 }))
 declare void @f.param.inalloca(i8* inalloca)
 ; CHECK: declare void @f.param.inalloca(i8* inalloca)
 declare void @f.param.sret(i8* sret)
diff --git a/llvm/test/Bitcode/compatibility-3.8.ll b/llvm/test/Bitcode/compatibility-3.8.ll
index 2e70a380d10e..c8d826191559 100644
--- a/llvm/test/Bitcode/compatibility-3.8.ll
+++ b/llvm/test/Bitcode/compatibility-3.8.ll
@@ -435,7 +435,7 @@ declare void @f.param.signext(i8 signext)
 declare void @f.param.inreg(i8 inreg)
 ; CHECK: declare void @f.param.inreg(i8 inreg)
 declare void @f.param.byval({ i8, i8 }* byval)
-; CHECK: declare void @f.param.byval({ i8, i8 }* byval)
+; CHECK: declare void @f.param.byval({ i8, i8 }* byval({ i8, i8 }))
 declare void @f.param.inalloca(i8* inalloca)
 ; CHECK: declare void @f.param.inalloca(i8* inalloca)
 declare void @f.param.sret(i8* sret)
diff --git a/llvm/test/Bitcode/compatibility-3.9.ll b/llvm/test/Bitcode/compatibility-3.9.ll
index 7c84daa7d3c4..f031e54a9f21 100644
--- a/llvm/test/Bitcode/compatibility-3.9.ll
+++ b/llvm/test/Bitcode/compatibility-3.9.ll
@@ -504,7 +504,7 @@ declare void @f.param.signext(i8 signext)
 declare void @f.param.inreg(i8 inreg)
 ; CHECK: declare void @f.param.inreg(i8 inreg)
 declare void @f.param.byval({ i8, i8 }* byval)
-; CHECK: declare void @f.param.byval({ i8, i8 }* byval)
+; CHECK: declare void @f.param.byval({ i8, i8 }* byval({ i8, i8 }))
 declare void @f.param.inalloca(i8* inalloca)
 ; CHECK: declare void @f.param.inalloca(i8* inalloca)
 declare void @f.param.sret(i8* sret)
diff --git a/llvm/test/Bitcode/compatibility-4.0.ll b/llvm/test/Bitcode/compatibility-4.0.ll
index 9e34d48c95f7..8020df45da6a 100644
--- a/llvm/test/Bitcode/compatibility-4.0.ll
+++ b/llvm/test/Bitcode/compatibility-4.0.ll
@@ -504,7 +504,7 @@ declare void @f.param.signext(i8 signext)
 declare void @f.param.inreg(i8 inreg)
 ; CHECK: declare void @f.param.inreg(i8 inreg)
 declare void @f.param.byval({ i8, i8 }* byval)
-; CHECK: declare void @f.param.byval({ i8, i8 }* byval)
+; CHECK: declare void @f.param.byval({ i8, i8 }* byval({ i8, i8 }))
 declare void @f.param.inalloca(i8* inalloca)
 ; CHECK: declare void @f.param.inalloca(i8* inalloca)
 declare void @f.param.sret(i8* sret)
diff --git a/llvm/test/Bitcode/compatibility-5.0.ll b/llvm/test/Bitcode/compatibility-5.0.ll
index a4b3fca82b7b..3b32d668af55 100644
--- a/llvm/test/Bitcode/compatibility-5.0.ll
+++ b/llvm/test/Bitcode/compatibility-5.0.ll
@@ -508,7 +508,7 @@ declare void @f.param.signext(i8 signext)
 declare void @f.param.inreg(i8 inreg)
 ; CHECK: declare void @f.param.inreg(i8 inreg)
 declare void @f.param.byval({ i8, i8 }* byval)
-; CHECK: declare void @f.param.byval({ i8, i8 }* byval)
+; CHECK: declare void @f.param.byval({ i8, i8 }* byval({ i8, i8 }))
 declare void @f.param.inalloca(i8* inalloca)
 ; CHECK: declare void @f.param.inalloca(i8* inalloca)
 declare void @f.param.sret(i8* sret)
diff --git a/llvm/test/Bitcode/compatibility-6.0.ll b/llvm/test/Bitcode/compatibility-6.0.ll
index 097e19ecb7ff..3b08c4a72311 100644
--- a/llvm/test/Bitcode/compatibility-6.0.ll
+++ b/llvm/test/Bitcode/compatibility-6.0.ll
@@ -515,7 +515,7 @@ declare void @f.param.signext(i8 signext)
 declare void @f.param.inreg(i8 inreg)
 ; CHECK: declare void @f.param.inreg(i8 inreg)
 declare void @f.param.byval({ i8, i8 }* byval)
-; CHECK: declare void @f.param.byval({ i8, i8 }* byval)
+; CHECK: declare void @f.param.byval({ i8, i8 }* byval({ i8, i8 }))
 declare void @f.param.inalloca(i8* inalloca)
 ; CHECK: declare void @f.param.inalloca(i8* inalloca)
 declare void @f.param.sret(i8* sret)
diff --git a/llvm/test/Bitcode/compatibility.ll b/llvm/test/Bitcode/compatibility.ll
index 06b81fa14a81..991bde69b61d 100644
--- a/llvm/test/Bitcode/compatibility.ll
+++ b/llvm/test/Bitcode/compatibility.ll
@@ -529,7 +529,7 @@ declare void @f.param.signext(i8 signext)
 declare void @f.param.inreg(i8 inreg)
 ; CHECK: declare void @f.param.inreg(i8 inreg)
 declare void @f.param.byval({ i8, i8 }* byval)
-; CHECK: declare void @f.param.byval({ i8, i8 }* byval)
+; CHECK: declare void @f.param.byval({ i8, i8 }* byval({ i8, i8 }))
 declare void @f.param.inalloca(i8* inalloca)
 ; CHECK: declare void @f.param.inalloca(i8* inalloca)
 declare void @f.param.sret(i8* sret)
@@ -1735,6 +1735,15 @@ define i8** @constexpr() {
 declare void @llvm.test.immarg.intrinsic(i32 immarg)
 ; CHECK: declare void @llvm.test.immarg.intrinsic(i32 immarg)
 
+; byval attribute with type
+%named_type = type [8 x i8]
+declare void @byval_type(i32* byval(i32) align 2)
+declare void @byval_type2({ i8, i8* }* byval({ i8, i8* }))
+declare void @byval_named_type(%named_type* byval(%named_type))
+; CHECK: declare void @byval_type(i32* byval(i32) align 2)
+; CHECK: declare void @byval_type2({ i8, i8* }* byval({ i8, i8* }))
+; CHECK: declare void @byval_named_type([8 x i8]* byval([8 x i8]))
+
 ; CHECK: attributes #0 = { alignstack=4 }
 ; CHECK: attributes #1 = { alignstack=8 }
 ; CHECK: attributes #2 = { alwaysinline }
diff --git a/llvm/test/Bitcode/highLevelStructure.3.2.ll b/llvm/test/Bitcode/highLevelStructure.3.2.ll
index 749b157cffc3..91d6ee4ac257 100644
--- a/llvm/test/Bitcode/highLevelStructure.3.2.ll
+++ b/llvm/test/Bitcode/highLevelStructure.3.2.ll
@@ -41,7 +41,7 @@ declare void @ParamAttr3(i8* sret)
 declare void @ParamAttr4(i8 signext)
 ; CHECK: declare void @ParamAttr5(i8* inreg)
 declare void @ParamAttr5(i8* inreg)
-; CHECK: declare void @ParamAttr6(i8* byval)
+; CHECK: declare void @ParamAttr6(i8* byval(i8))
 declare void @ParamAttr6(i8* byval)
 ; CHECK: declare void @ParamAttr7(i8* noalias)
 declare void @ParamAttr7(i8* noalias)
@@ -51,7 +51,7 @@ declare void @ParamAttr8(i8* nocapture)
 declare void @ParamAttr9(i8* nest noalias nocapture)
 ; CHECK: declare void @ParamAttr10{{[(i8* sret noalias nocapture) | (i8* noalias nocapture sret)]}}
 declare void @ParamAttr10(i8* sret noalias nocapture)
-;CHECK: declare void @ParamAttr11{{[(i8* byval noalias nocapture) | (i8* noalias nocapture byval)]}}
+;CHECK: declare void @ParamAttr11{{[(i8* byval(i8) noalias nocapture) | (i8* noalias nocapture byval(i8))]}}
 declare void @ParamAttr11(i8* byval noalias nocapture)
 ;CHECK: declare void @ParamAttr12{{[(i8* inreg noalias nocapture) | (i8* noalias nocapture inreg)]}}
 declare void @ParamAttr12(i8* inreg noalias nocapture)
diff --git a/llvm/test/CodeGen/AArch64/byval-type.ll b/llvm/test/CodeGen/AArch64/byval-type.ll
new file mode 100644
index 000000000000..0c2e2dc471dd
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/byval-type.ll
@@ -0,0 +1,37 @@
+; RUN: llc -mtriple=aarch64-linux-gnu %s -o - | FileCheck %s
+
+define i8 @byval_match(i8* byval(i8) align 1, i8* byval %ptr) {
+; CHECK-LABEL: byval_match:
+; CHECK: ldrb w0, [sp, #8]
+  %res = load i8, i8* %ptr
+  ret i8 %res
+}
+
+define void @caller_match(i8* %p0, i8* %p1) {
+; CHECK-LABEL: caller_match:
+; CHECK: ldrb [[P1:w[0-9]+]], [x1]
+; CHECK: strb [[P1]], [sp, #8]
+; CHECK: ldrb [[P0:w[0-9]+]], [x0]
+; CHECK: strb [[P0]], [sp]
+; CHECK: bl byval_match
+  call i8 @byval_match(i8* byval(i8) align 1 %p0, i8* byval %p1)
+  ret void
+}
+
+define i8 @byval_large([3 x i64]* byval([3 x i64]) align 8, i8* byval %ptr) {
+; CHECK-LABEL: byval_large:
+; CHECK: ldrb w0, [sp, #24]
+  %res = load i8, i8* %ptr
+  ret i8 %res
+}
+
+define void @caller_large([3 x i64]* %p0, i8* %p1) {
+; CHECK-LABEL: caller_large:
+; CHECK: ldr [[P0HI:x[0-9]+]], [x0, #16]
+; CHECK: ldr [[P0LO:q[0-9]+]], [x0]
+; CHECK: str [[P0HI]], [sp, #16]
+; CHECK: str [[P0LO]], [sp]
+; CHECK: bl byval_large
+  call i8 @byval_large([3 x i64]* byval([3 x i64]) align 8 %p0, i8* byval %p1)
+  ret void
+}
diff --git a/llvm/test/Linker/Inputs/byval-types-1.ll b/llvm/test/Linker/Inputs/byval-types-1.ll
new file mode 100644
index 000000000000..3da8b91f619e
--- /dev/null
+++ b/llvm/test/Linker/Inputs/byval-types-1.ll
@@ -0,0 +1,8 @@
+%struct = type {i32, i8}
+
+declare void @baz(%struct* byval(%struct))
+
+define void @foo(%struct* byval(%struct) %a) {
+  call void @baz(%struct* byval(%struct) %a)
+  ret void
+}
diff --git a/llvm/test/Linker/byval-types.ll b/llvm/test/Linker/byval-types.ll
new file mode 100644
index 000000000000..d6bd4aa0c7b9
--- /dev/null
+++ b/llvm/test/Linker/byval-types.ll
@@ -0,0 +1,17 @@
+; RUN: llvm-link %s %p/Inputs/byval-types-1.ll -S | FileCheck %s
+
+%struct = type {i32, i8}
+
+declare void @foo(%struct* byval(%struct) %a)
+
+define void @bar() {
+  %ptr = alloca %struct
+; CHECK: call void @foo(%struct* byval(%struct) %ptr)
+  call void @foo(%struct* byval(%struct) %ptr)
+  ret void
+}
+
+; CHECK: define void @foo(%struct* byval(%struct) %a)
+; CHECK-NEXT:   call void @baz(%struct* byval(%struct) %a)
+
+; CHECK: declare void @baz(%struct* byval(%struct))
diff --git a/llvm/test/Transforms/Inline/byval-tail-call.ll b/llvm/test/Transforms/Inline/byval-tail-call.ll
index 8aafe7943f4e..be495f1bcd37 100644
--- a/llvm/test/Transforms/Inline/byval-tail-call.ll
+++ b/llvm/test/Transforms/Inline/byval-tail-call.ll
@@ -56,7 +56,7 @@ define void @foobar(i32* %x) {
 ; CHECK: %[[POS:.*]] = alloca i32
 ; CHECK: %[[VAL:.*]] = load i32, i32* %x
 ; CHECK: store i32 %[[VAL]], i32* %[[POS]]
-; CHECK: tail call void @ext2(i32* byval nonnull %[[POS]]
+; CHECK: tail call void @ext2(i32* nonnull byval %[[POS]]
 ; CHECK: ret void
   tail call void @bar2(i32* byval %x)
   ret void
@@ -67,7 +67,7 @@ define void @barfoo() {
 ; CHECK: %[[POS:.*]] = alloca i32
 ; CHECK: %[[VAL:.*]] = load i32, i32* %x
 ; CHECK: store i32 %[[VAL]], i32* %[[POS]]
-; CHECK: tail call void @ext2(i32* byval nonnull %[[POS]]
+; CHECK: tail call void @ext2(i32* nonnull byval %[[POS]]
 ; CHECK: ret void
   %x = alloca i32
   tail call void @bar2(i32* byval %x)
diff --git a/llvm/unittests/IR/AttributesTest.cpp b/llvm/unittests/IR/AttributesTest.cpp
index e0be2343a144..06da35aca573 100644
--- a/llvm/unittests/IR/AttributesTest.cpp
+++ b/llvm/unittests/IR/AttributesTest.cpp
@@ -8,6 +8,7 @@
 
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/DerivedTypes.h"
 #include "gtest/gtest.h"
 using namespace llvm;
 
@@ -40,6 +41,10 @@ TEST(Attributes, Ordering) {
   EXPECT_TRUE(Align4 < Deref5);
   EXPECT_TRUE(Align5 < Deref4);
 
+  Attribute ByVal = Attribute::get(C, Attribute::ByVal, Type::getInt32Ty(C));
+  EXPECT_FALSE(ByVal < Attribute::get(C, Attribute::ZExt));
+  EXPECT_TRUE(ByVal < Align4);
+
   AttributeList ASs[] = {AttributeList::get(C, 2, Attribute::ZExt),
                          AttributeList::get(C, 1, Attribute::SExt)};
 
@@ -166,4 +171,19 @@ TEST(Attributes, OverflowGet) {
   EXPECT_EQ(2U, AL.getNumAttrSets());
 }
 
+TEST(Attributes, StringRepresentation) {
+  LLVMContext C;
+  StructType *Ty = StructType::create(Type::getInt32Ty(C), "mystruct");
+
+  // Insufficiently careful printing can result in byval(%mystruct = { i32 })
+  Attribute A = Attribute::getWithByValType(C, Ty);
+  EXPECT_EQ(A.getAsString(), "byval(%mystruct)");
+
+  A = Attribute::getWithByValType(C, nullptr);
+  EXPECT_EQ(A.getAsString(), "byval");
+
+  A = Attribute::getWithByValType(C, Type::getInt32Ty(C));
+  EXPECT_EQ(A.getAsString(), "byval(i32)");
+}
+
 } // end anonymous namespace