diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp
index cda5fd0a38123..acf0e4afef27d 100644
--- a/llvm/lib/IR/AsmWriter.cpp
+++ b/llvm/lib/IR/AsmWriter.cpp
@@ -2399,6 +2399,8 @@ class AssemblyWriter {
 
   void writeAllMDNodes();
   void writeMDNode(unsigned Slot, const MDNode *Node);
+  void writeAttribute(const Attribute &Attr, bool InAttrGroup = false);
+  void writeAttributeSet(const AttributeSet &AttrSet, bool InAttrGroup = false);
   void writeAllAttributeGroups();
 
   void printTypeIdentities();
@@ -2531,8 +2533,10 @@ void AssemblyWriter::writeParamOperand(const Value *Operand,
   // Print the type
   TypePrinter.print(Operand->getType(), Out);
   // Print parameter attributes list
-  if (Attrs.hasAttributes())
-    Out << ' ' << Attrs.getAsString();
+  if (Attrs.hasAttributes()) {
+    Out << ' ';
+    writeAttributeSet(Attrs);
+  }
   Out << ' ';
   // Print the operand
   WriteAsOperandInternal(Out, Operand, &TypePrinter, &Machine, TheModule);
@@ -3462,8 +3466,10 @@ void AssemblyWriter::printFunction(const Function *F) {
       TypePrinter.print(FT->getParamType(I), Out);
 
       AttributeSet ArgAttrs = Attrs.getParamAttributes(I);
-      if (ArgAttrs.hasAttributes())
-        Out << ' ' << ArgAttrs.getAsString();
+      if (ArgAttrs.hasAttributes()) {
+        Out << ' ';
+        writeAttributeSet(ArgAttrs);
+      }
     }
   } else {
     // The arguments are meaningful here, print them in detail.
@@ -3549,8 +3555,10 @@ void AssemblyWriter::printArgument(const Argument *Arg, AttributeSet Attrs) {
   TypePrinter.print(Arg->getType(), Out);
 
   // Output parameter attributes list
-  if (Attrs.hasAttributes())
-    Out << ' ' << Attrs.getAsString();
+  if (Attrs.hasAttributes()) {
+    Out << ' ';
+    writeAttributeSet(Attrs);
+  }
 
   // Output name, if available...
   if (Arg->hasName()) {
@@ -4126,6 +4134,33 @@ void AssemblyWriter::printMDNodeBody(const MDNode *Node) {
   WriteMDNodeBodyInternal(Out, Node, &TypePrinter, &Machine, TheModule);
 }
 
+void AssemblyWriter::writeAttribute(const Attribute &Attr, bool InAttrGroup) {
+  if (!Attr.isTypeAttribute()) {
+    Out << Attr.getAsString(InAttrGroup);
+    return;
+  }
+
+  assert(Attr.hasAttribute(Attribute::ByVal) && "unexpected type attr");
+
+  Out << "byval";
+  if (Type *Ty = Attr.getValueAsType()) {
+    Out << '(';
+    TypePrinter.print(Ty, Out);
+    Out << ')';
+  }
+}
+
+void AssemblyWriter::writeAttributeSet(const AttributeSet &AttrSet,
+                                       bool InAttrGroup) {
+  bool FirstAttr = true;
+  for (const auto &Attr : AttrSet) {
+    if (!FirstAttr)
+      Out << ' ';
+    writeAttribute(Attr, InAttrGroup);
+    FirstAttr = false;
+  }
+}
+
 void AssemblyWriter::writeAllAttributeGroups() {
   std::vector<std::pair<AttributeSet, unsigned>> asVec;
   asVec.resize(Machine.as_size());
diff --git a/llvm/test/Assembler/byval-type-attr.ll b/llvm/test/Assembler/byval-type-attr.ll
index c868885d2cc54..dd195a39651c0 100644
--- a/llvm/test/Assembler/byval-type-attr.ll
+++ b/llvm/test/Assembler/byval-type-attr.ll
@@ -29,3 +29,15 @@ fail:
 declare void @baz(%named_type* byval(%named_type))
 
 declare i32 @__gxx_personality_v0(...)
+
+%0 = type opaque
+
+; CHECK: define void @anon({ %0* }* byval({ %0* }) %arg)
+; CHECK:   call void @anon_callee({ %0* }* byval({ %0* }) %arg)
+define void @anon({ %0* }* byval({ %0* }) %arg) {
+  call void @anon_callee({ %0* }* byval({ %0* }) %arg)
+  ret void
+}
+
+; CHECK: declare void @anon_callee({ %0* }* byval({ %0* }))
+declare void @anon_callee({ %0* }* byval({ %0* }))