IR: add optional type to 'byval' function parameters

When we switch to opaque pointer types we will need some way to describe
how many bytes a 'byval' parameter should occupy on the stack. This adds
a (for now) optional extra type parameter.

If present, the type must match the pointee type of the argument.

Note to front-end maintainers: if this causes test failures, it's probably
because the "byval" attribute is printed after attributes without any parameter
after this change.

llvm-svn: 362012

13 files changed, 252 insertions, 26 deletions

diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index 95646675cb2..0a9a09e644d 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 ad169afb935..ec4a61b5498 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 134ce036703..9f562ba82db 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 8e1e06226bb..d243815667f 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 72d7000fad9..143570fb20a 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 f144b18aa63..93727406a08 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 8fb1a7b5bb9..d887ed73c44 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 fe857f73b25..da06ac7a414 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 d636e613363..4ad578d80fa 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 8ebcb04a565..f6898476382 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 0be09a05e82..839ef46b4f4 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)
diff --git a/llvm/lib/IR/Function.cpp b/llvm/lib/IR/Function.cpp
index b00deb677b3..a4a78ca4deb 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 d5c3287e713..963bf82c989 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: " +