diff --git a/llvm/include/llvm/Object/ArchiveWriter.h b/llvm/include/llvm/Object/ArchiveWriter.h
--- a/llvm/include/llvm/Object/ArchiveWriter.h
+++ b/llvm/include/llvm/Object/ArchiveWriter.h
@@ -39,6 +39,12 @@
                    bool WriteSymtab, object::Archive::Kind Kind,
                    bool Deterministic, bool Thin,
                    std::unique_ptr<MemoryBuffer> OldArchiveBuf = nullptr);
+
+Expected<std::unique_ptr<MemoryBuffer>>
+writeArchiveToBuffer(StringRef ArcName, ArrayRef<NewArchiveMember> NewMembers,
+                     bool WriteSymtab, object::Archive::Kind Kind,
+                     bool Deterministic, bool Thin,
+                     std::unique_ptr<MemoryBuffer> OldArchiveBuf = nullptr);
 }
 
 #endif
diff --git a/llvm/lib/Object/ArchiveWriter.cpp b/llvm/lib/Object/ArchiveWriter.cpp
--- a/llvm/lib/Object/ArchiveWriter.cpp
+++ b/llvm/lib/Object/ArchiveWriter.cpp
@@ -26,6 +26,7 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/Path.h"
+#include "llvm/Support/SmallVectorMemoryBuffer.h"
 #include "llvm/Support/ToolOutputFile.h"
 #include "llvm/Support/raw_ostream.h"
 
@@ -552,10 +553,11 @@
   return std::string(Relative.str());
 }
 
-Error writeArchive(StringRef ArcName, ArrayRef<NewArchiveMember> NewMembers,
-                   bool WriteSymtab, object::Archive::Kind Kind,
-                   bool Deterministic, bool Thin,
-                   std::unique_ptr<MemoryBuffer> OldArchiveBuf) {
+static Error
+writeTemporaryArchive(raw_ostream &Out, StringRef ArcName,
+                      ArrayRef<NewArchiveMember> NewMembers, bool WriteSymtab,
+                      object::Archive::Kind Kind, bool Deterministic, bool Thin,
+                      std::unique_ptr<MemoryBuffer> OldArchiveBuf) {
   assert((!Thin || !isBSDLike(Kind)) && "Only the gnu format has a thin mode");
 
   SmallString<0> SymNamesBuf;
@@ -608,12 +610,6 @@
     }
   }
 
-  Expected<sys::fs::TempFile> Temp =
-      sys::fs::TempFile::create(ArcName + ".temp-archive-%%%%%%%.a");
-  if (!Temp)
-    return Temp.takeError();
-
-  raw_fd_ostream Out(Temp->FD, false);
   if (Thin)
     Out << "!<thin>\n";
   else
@@ -639,7 +635,41 @@
   // closed before we attempt to rename.
   OldArchiveBuf.reset();
 
+  return Error::success();
+}
+
+Error writeArchive(StringRef ArcName, ArrayRef<NewArchiveMember> NewMembers,
+                   bool WriteSymtab, object::Archive::Kind Kind,
+                   bool Deterministic, bool Thin,
+                   std::unique_ptr<MemoryBuffer> OldArchiveBuf) {
+  Expected<sys::fs::TempFile> Temp =
+      sys::fs::TempFile::create(ArcName + ".temp-archive-%%%%%%%.a");
+  if (!Temp)
+    return Temp.takeError();
+  raw_fd_ostream Out(Temp->FD, false);
+
+  if (Error E =
+          writeTemporaryArchive(Out, ArcName, NewMembers, WriteSymtab, Kind,
+                                Deterministic, Thin, std::move(OldArchiveBuf)))
+    return E;
   return Temp->keep(ArcName);
 }
 
+Expected<std::unique_ptr<MemoryBuffer>>
+writeArchiveToBuffer(StringRef ArcName, ArrayRef<NewArchiveMember> NewMembers,
+                     bool WriteSymtab, object::Archive::Kind Kind,
+                     bool Deterministic, bool Thin,
+                     std::unique_ptr<MemoryBuffer> OldArchiveBuf) {
+  SmallVector<char, 0> ArchiveBufferVector;
+  raw_svector_ostream ArchiveStream(ArchiveBufferVector);
+
+  if (Error E = writeTemporaryArchive(ArchiveStream, ArcName, NewMembers,
+                                      WriteSymtab, Kind, Deterministic, Thin,
+                                      std::move(OldArchiveBuf)))
+    return std::move(E);
+
+  return std::make_unique<SmallVectorMemoryBuffer>(
+      std::move(ArchiveBufferVector));
+}
+
 } // namespace llvm