diff --git a/llvm/include/llvm/LTO/LTOCodeGenerator.h b/llvm/include/llvm/LTO/LTOCodeGenerator.h
index 820d6d5d9384..a4aace41a72d 100644
--- a/llvm/include/llvm/LTO/LTOCodeGenerator.h
+++ b/llvm/include/llvm/LTO/LTOCodeGenerator.h
@@ -53,6 +53,7 @@ namespace llvm {
   class TargetLibraryInfo;
   class TargetMachine;
   class raw_ostream;
+  class raw_pwrite_stream;
 
 //===----------------------------------------------------------------------===//
 /// C++ class which implements the opaque lto_code_gen_t type.
@@ -137,7 +138,7 @@ struct LTOCodeGenerator {
 private:
   void initializeLTOPasses();
 
-  bool compileOptimized(raw_ostream &out, std::string &errMsg);
+  bool compileOptimized(raw_pwrite_stream &out, std::string &errMsg);
   bool compileOptimizedToFile(const char **name, std::string &errMsg);
   void applyScopeRestrictions();
   void applyRestriction(GlobalValue &GV, ArrayRef<StringRef> Libcalls,
diff --git a/llvm/include/llvm/MC/MCAsmBackend.h b/llvm/include/llvm/MC/MCAsmBackend.h
index 93025cd9b1b3..ff77dc91683f 100644
--- a/llvm/include/llvm/MC/MCAsmBackend.h
+++ b/llvm/include/llvm/MC/MCAsmBackend.h
@@ -48,7 +48,7 @@ public:
 
   /// Create a new MCObjectWriter instance for use by the assembler backend to
   /// emit the final object file.
-  virtual MCObjectWriter *createObjectWriter(raw_ostream &OS) const = 0;
+  virtual MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const = 0;
 
   /// Create a new ELFObjectTargetWriter to enable non-standard
   /// ELFObjectWriters.
diff --git a/llvm/include/llvm/MC/MCELFObjectWriter.h b/llvm/include/llvm/MC/MCELFObjectWriter.h
index 9ed8e8024835..e9fef76c20f9 100644
--- a/llvm/include/llvm/MC/MCELFObjectWriter.h
+++ b/llvm/include/llvm/MC/MCELFObjectWriter.h
@@ -24,6 +24,7 @@ class MCSectionData;
 class MCSymbol;
 class MCSymbolData;
 class MCValue;
+class raw_pwrite_stream;
 
 struct ELFRelocationEntry {
   uint64_t Offset; // Where is the relocation.
@@ -130,7 +131,8 @@ public:
 /// \param OS - The stream to write to.
 /// \returns The constructed object writer.
 MCObjectWriter *createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
-                                      raw_ostream &OS, bool IsLittleEndian);
+                                      raw_pwrite_stream &OS,
+                                      bool IsLittleEndian);
 } // End llvm namespace
 
 #endif
diff --git a/llvm/include/llvm/MC/MCELFStreamer.h b/llvm/include/llvm/MC/MCELFStreamer.h
index 361c8f523f6f..6a858cda162c 100644
--- a/llvm/include/llvm/MC/MCELFStreamer.h
+++ b/llvm/include/llvm/MC/MCELFStreamer.h
@@ -29,10 +29,9 @@ class raw_ostream;
 
 class MCELFStreamer : public MCObjectStreamer {
 public:
-  MCELFStreamer(MCContext &Context, MCAsmBackend &TAB, raw_ostream &OS,
+  MCELFStreamer(MCContext &Context, MCAsmBackend &TAB, raw_pwrite_stream &OS,
                 MCCodeEmitter *Emitter)
-      : MCObjectStreamer(Context, TAB, OS, Emitter),
-        SeenIdent(false) {}
+      : MCObjectStreamer(Context, TAB, OS, Emitter), SeenIdent(false) {}
 
   ~MCELFStreamer() override;
 
@@ -116,8 +115,9 @@ private:
 };
 
 MCELFStreamer *createARMELFStreamer(MCContext &Context, MCAsmBackend &TAB,
-                                    raw_ostream &OS, MCCodeEmitter *Emitter,
-                                    bool RelaxAll, bool IsThumb);
+                                    raw_pwrite_stream &OS,
+                                    MCCodeEmitter *Emitter, bool RelaxAll,
+                                    bool IsThumb);
 
 } // end namespace llvm
 
diff --git a/llvm/include/llvm/MC/MCMachObjectWriter.h b/llvm/include/llvm/MC/MCMachObjectWriter.h
index eb2789b90f9a..bfe5d3614c0a 100644
--- a/llvm/include/llvm/MC/MCMachObjectWriter.h
+++ b/llvm/include/llvm/MC/MCMachObjectWriter.h
@@ -119,7 +119,7 @@ class MachObjectWriter : public MCObjectWriter {
   MachSymbolData *findSymbolData(const MCSymbol &Sym);
 
 public:
-  MachObjectWriter(MCMachObjectTargetWriter *MOTW, raw_ostream &OS,
+  MachObjectWriter(MCMachObjectTargetWriter *MOTW, raw_pwrite_stream &OS,
                    bool IsLittleEndian)
       : MCObjectWriter(OS, IsLittleEndian), TargetObjectWriter(MOTW) {}
 
@@ -279,7 +279,8 @@ public:
 /// \param OS - The stream to write to.
 /// \returns The constructed object writer.
 MCObjectWriter *createMachObjectWriter(MCMachObjectTargetWriter *MOTW,
-                                       raw_ostream &OS, bool IsLittleEndian);
+                                       raw_pwrite_stream &OS,
+                                       bool IsLittleEndian);
 
 } // End llvm namespace
 
diff --git a/llvm/include/llvm/MC/MCObjectStreamer.h b/llvm/include/llvm/MC/MCObjectStreamer.h
index 7ed3e115e3dc..6666a503ea8a 100644
--- a/llvm/include/llvm/MC/MCObjectStreamer.h
+++ b/llvm/include/llvm/MC/MCObjectStreamer.h
@@ -24,6 +24,7 @@ class MCFragment;
 class MCDataFragment;
 class MCAsmBackend;
 class raw_ostream;
+class raw_pwrite_stream;
 
 /// \brief Streaming object file generation interface.
 ///
@@ -45,7 +46,7 @@ class MCObjectStreamer : public MCStreamer {
   void EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) override;
 
 protected:
-  MCObjectStreamer(MCContext &Context, MCAsmBackend &TAB, raw_ostream &OS,
+  MCObjectStreamer(MCContext &Context, MCAsmBackend &TAB, raw_pwrite_stream &OS,
                    MCCodeEmitter *Emitter);
   ~MCObjectStreamer() override;
 
diff --git a/llvm/include/llvm/MC/MCObjectWriter.h b/llvm/include/llvm/MC/MCObjectWriter.h
index f0e86a7cc83d..f8e2821c4dc4 100644
--- a/llvm/include/llvm/MC/MCObjectWriter.h
+++ b/llvm/include/llvm/MC/MCObjectWriter.h
@@ -42,12 +42,12 @@ class MCObjectWriter {
   void operator=(const MCObjectWriter &) = delete;
 
 protected:
-  raw_ostream &OS;
+  raw_pwrite_stream &OS;
 
   unsigned IsLittleEndian : 1;
 
 protected: // Can only create subclasses.
-  MCObjectWriter(raw_ostream &OS, bool IsLittleEndian)
+  MCObjectWriter(raw_pwrite_stream &OS, bool IsLittleEndian)
       : OS(OS), IsLittleEndian(IsLittleEndian) {}
 
 public:
diff --git a/llvm/include/llvm/MC/MCWinCOFFObjectWriter.h b/llvm/include/llvm/MC/MCWinCOFFObjectWriter.h
index 956e43642c35..e2e95c7df710 100644
--- a/llvm/include/llvm/MC/MCWinCOFFObjectWriter.h
+++ b/llvm/include/llvm/MC/MCWinCOFFObjectWriter.h
@@ -16,6 +16,7 @@ class MCFixup;
 class MCObjectWriter;
 class MCValue;
 class raw_ostream;
+class raw_pwrite_stream;
 
   class MCWinCOFFObjectTargetWriter {
     virtual void anchor();
@@ -40,7 +41,7 @@ class raw_ostream;
   /// \param OS - The stream to write to.
   /// \returns The constructed object writer.
   MCObjectWriter *createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
-                                            raw_ostream &OS);
+                                            raw_pwrite_stream &OS);
 } // End llvm namespace
 
 #endif
diff --git a/llvm/include/llvm/MC/MCWinCOFFStreamer.h b/llvm/include/llvm/MC/MCWinCOFFStreamer.h
index 57a75cec2204..b3fee810b6b2 100644
--- a/llvm/include/llvm/MC/MCWinCOFFStreamer.h
+++ b/llvm/include/llvm/MC/MCWinCOFFStreamer.h
@@ -24,11 +24,12 @@ class MCSubtargetInfo;
 class MCSymbol;
 class StringRef;
 class raw_ostream;
+class raw_pwrite_stream;
 
 class MCWinCOFFStreamer : public MCObjectStreamer {
 public:
   MCWinCOFFStreamer(MCContext &Context, MCAsmBackend &MAB, MCCodeEmitter &CE,
-                    raw_ostream &OS);
+                    raw_pwrite_stream &OS);
 
   /// state management
   void reset() override {
diff --git a/llvm/include/llvm/Support/TargetRegistry.h b/llvm/include/llvm/Support/TargetRegistry.h
index 12e35ec10152..a4bf51f67f3c 100644
--- a/llvm/include/llvm/Support/TargetRegistry.h
+++ b/llvm/include/llvm/Support/TargetRegistry.h
@@ -50,6 +50,7 @@ namespace llvm {
   class TargetMachine;
   class TargetOptions;
   class raw_ostream;
+  class raw_pwrite_stream;
   class formatted_raw_ostream;
 
   MCStreamer *createNullStreamer(MCContext &Ctx);
@@ -61,10 +62,10 @@ namespace llvm {
 
   /// Takes ownership of \p TAB and \p CE.
   MCStreamer *createELFStreamer(MCContext &Ctx, MCAsmBackend &TAB,
-                                raw_ostream &OS, MCCodeEmitter *CE,
+                                raw_pwrite_stream &OS, MCCodeEmitter *CE,
                                 bool RelaxAll);
   MCStreamer *createMachOStreamer(MCContext &Ctx, MCAsmBackend &TAB,
-                                  raw_ostream &OS, MCCodeEmitter *CE,
+                                  raw_pwrite_stream &OS, MCCodeEmitter *CE,
                                   bool RelaxAll, bool DWARFMustBeAtTheEnd,
                                   bool LabelSections = false);
 
@@ -135,14 +136,15 @@ namespace llvm {
                                                   const MCRegisterInfo &MRI,
                                                   MCContext &Ctx);
     typedef MCStreamer *(*ELFStreamerCtorTy)(const Triple &T, MCContext &Ctx,
-                                             MCAsmBackend &TAB, raw_ostream &OS,
+                                             MCAsmBackend &TAB,
+                                             raw_pwrite_stream &OS,
                                              MCCodeEmitter *Emitter,
                                              bool RelaxAll);
     typedef MCStreamer *(*MachOStreamerCtorTy)(
-        MCContext &Ctx, MCAsmBackend &TAB, raw_ostream &OS,
+        MCContext &Ctx, MCAsmBackend &TAB, raw_pwrite_stream &OS,
         MCCodeEmitter *Emitter, bool RelaxAll, bool DWARFMustBeAtTheEnd);
     typedef MCStreamer *(*COFFStreamerCtorTy)(MCContext &Ctx, MCAsmBackend &TAB,
-                                              raw_ostream &OS,
+                                              raw_pwrite_stream &OS,
                                               MCCodeEmitter *Emitter,
                                               bool RelaxAll);
     typedef MCTargetStreamer *(*NullTargetStreamerCtorTy)(MCStreamer &S);
@@ -438,7 +440,7 @@ namespace llvm {
     /// \param Emitter The target independent assembler object.Takes ownership.
     /// \param RelaxAll Relax all fixups?
     MCStreamer *createMCObjectStreamer(const Triple &T, MCContext &Ctx,
-                                       MCAsmBackend &TAB, raw_ostream &OS,
+                                       MCAsmBackend &TAB, raw_pwrite_stream &OS,
                                        MCCodeEmitter *Emitter,
                                        const MCSubtargetInfo &STI,
                                        bool RelaxAll,
diff --git a/llvm/include/llvm/Target/TargetMachine.h b/llvm/include/llvm/Target/TargetMachine.h
index 58532180e484..2a1ce0483e10 100644
--- a/llvm/include/llvm/Target/TargetMachine.h
+++ b/llvm/include/llvm/Target/TargetMachine.h
@@ -48,6 +48,7 @@ class TargetSubtargetInfo;
 class TargetTransformInfo;
 class formatted_raw_ostream;
 class raw_ostream;
+class raw_pwrite_stream;
 class TargetLoweringObjectFile;
 
 // The old pass manager infrastructure is hidden in a legacy namespace now.
@@ -207,7 +208,7 @@ public:
   /// emitted.  Typically this will involve several steps of code generation.
   /// This method should return true if emission of this file type is not
   /// supported, or false on success.
-  virtual bool addPassesToEmitFile(PassManagerBase &, raw_ostream &,
+  virtual bool addPassesToEmitFile(PassManagerBase &, raw_pwrite_stream &,
                                    CodeGenFileType,
                                    bool /*DisableVerify*/ = true,
                                    AnalysisID /*StartAfter*/ = nullptr,
@@ -220,9 +221,8 @@ public:
   /// fills the MCContext Ctx pointer which can be used to build custom
   /// MCStreamer.
   ///
-  virtual bool addPassesToEmitMC(PassManagerBase &,
-                                 MCContext *&,
-                                 raw_ostream &,
+  virtual bool addPassesToEmitMC(PassManagerBase &, MCContext *&,
+                                 raw_pwrite_stream &,
                                  bool /*DisableVerify*/ = true) {
     return true;
   }
@@ -256,7 +256,7 @@ public:
 
   /// Add passes to the specified pass manager to get the specified file
   /// emitted.  Typically this will involve several steps of code generation.
-  bool addPassesToEmitFile(PassManagerBase &PM, raw_ostream &Out,
+  bool addPassesToEmitFile(PassManagerBase &PM, raw_pwrite_stream &Out,
                            CodeGenFileType FileType, bool DisableVerify = true,
                            AnalysisID StartAfter = nullptr,
                            AnalysisID StopAfter = nullptr) override;
@@ -266,7 +266,8 @@ public:
   /// fills the MCContext Ctx pointer which can be used to build custom
   /// MCStreamer.
   bool addPassesToEmitMC(PassManagerBase &PM, MCContext *&Ctx,
-                         raw_ostream &OS, bool DisableVerify = true) override;
+                         raw_pwrite_stream &OS,
+                         bool DisableVerify = true) override;
 };
 
 } // End llvm namespace
diff --git a/llvm/lib/CodeGen/LLVMTargetMachine.cpp b/llvm/lib/CodeGen/LLVMTargetMachine.cpp
index 5e6bfb74537d..61d68f607111 100644
--- a/llvm/lib/CodeGen/LLVMTargetMachine.cpp
+++ b/llvm/lib/CodeGen/LLVMTargetMachine.cpp
@@ -141,7 +141,7 @@ static MCContext *addPassesToGenerateCode(LLVMTargetMachine *TM,
 }
 
 bool LLVMTargetMachine::addPassesToEmitFile(
-    PassManagerBase &PM, raw_ostream &Out, CodeGenFileType FileType,
+    PassManagerBase &PM, raw_pwrite_stream &Out, CodeGenFileType FileType,
     bool DisableVerify, AnalysisID StartAfter, AnalysisID StopAfter) {
   // Add common CodeGen passes.
   MCContext *Context = addPassesToGenerateCode(this, PM, DisableVerify,
@@ -227,9 +227,8 @@ bool LLVMTargetMachine::addPassesToEmitFile(
 /// code is not supported. It fills the MCContext Ctx pointer which can be
 /// used to build custom MCStreamer.
 ///
-bool LLVMTargetMachine::addPassesToEmitMC(PassManagerBase &PM,
-                                          MCContext *&Ctx,
-                                          raw_ostream &Out,
+bool LLVMTargetMachine::addPassesToEmitMC(PassManagerBase &PM, MCContext *&Ctx,
+                                          raw_pwrite_stream &Out,
                                           bool DisableVerify) {
   // Add common CodeGen passes.
   Ctx = addPassesToGenerateCode(this, PM, DisableVerify, nullptr, nullptr);
diff --git a/llvm/lib/LTO/LTOCodeGenerator.cpp b/llvm/lib/LTO/LTOCodeGenerator.cpp
index 345b22463889..6745c5707545 100644
--- a/llvm/lib/LTO/LTOCodeGenerator.cpp
+++ b/llvm/lib/LTO/LTOCodeGenerator.cpp
@@ -566,7 +566,8 @@ bool LTOCodeGenerator::optimize(bool DisableInline,
   return true;
 }
 
-bool LTOCodeGenerator::compileOptimized(raw_ostream &out, std::string &errMsg) {
+bool LTOCodeGenerator::compileOptimized(raw_pwrite_stream &out,
+                                        std::string &errMsg) {
   if (!this->determineTarget(errMsg))
     return false;
 
diff --git a/llvm/lib/MC/ELFObjectWriter.cpp b/llvm/lib/MC/ELFObjectWriter.cpp
index b2a83993f902..2b8b8ba98d72 100644
--- a/llvm/lib/MC/ELFObjectWriter.cpp
+++ b/llvm/lib/MC/ELFObjectWriter.cpp
@@ -168,7 +168,7 @@ class ELFObjectWriter : public MCObjectWriter {
     }
 
   public:
-    ELFObjectWriter(MCELFObjectTargetWriter *MOTW, raw_ostream &OS,
+    ELFObjectWriter(MCELFObjectTargetWriter *MOTW, raw_pwrite_stream &OS,
                     bool IsLittleEndian)
         : MCObjectWriter(OS, IsLittleEndian), FWriter(IsLittleEndian),
           TargetObjectWriter(MOTW), NeedsGOT(false) {}
@@ -1711,7 +1711,7 @@ bool ELFObjectWriter::isWeak(const MCSymbolData &SD) const {
 }
 
 MCObjectWriter *llvm::createELFObjectWriter(MCELFObjectTargetWriter *MOTW,
-                                            raw_ostream &OS,
+                                            raw_pwrite_stream &OS,
                                             bool IsLittleEndian) {
   return new ELFObjectWriter(MOTW, OS, IsLittleEndian);
 }
diff --git a/llvm/lib/MC/MCELFStreamer.cpp b/llvm/lib/MC/MCELFStreamer.cpp
index 8f0691b70c80..aa0539077255 100644
--- a/llvm/lib/MC/MCELFStreamer.cpp
+++ b/llvm/lib/MC/MCELFStreamer.cpp
@@ -647,7 +647,7 @@ void MCELFStreamer::FinishImpl() {
 }
 
 MCStreamer *llvm::createELFStreamer(MCContext &Context, MCAsmBackend &MAB,
-                                    raw_ostream &OS, MCCodeEmitter *CE,
+                                    raw_pwrite_stream &OS, MCCodeEmitter *CE,
                                     bool RelaxAll) {
   MCELFStreamer *S = new MCELFStreamer(Context, MAB, OS, CE);
   if (RelaxAll)
diff --git a/llvm/lib/MC/MCMachOStreamer.cpp b/llvm/lib/MC/MCMachOStreamer.cpp
index d5c7101d0d55..5c78f5fc69b8 100644
--- a/llvm/lib/MC/MCMachOStreamer.cpp
+++ b/llvm/lib/MC/MCMachOStreamer.cpp
@@ -54,7 +54,7 @@ private:
   void EmitDataRegionEnd();
 
 public:
-  MCMachOStreamer(MCContext &Context, MCAsmBackend &MAB, raw_ostream &OS,
+  MCMachOStreamer(MCContext &Context, MCAsmBackend &MAB, raw_pwrite_stream &OS,
                   MCCodeEmitter *Emitter, bool DWARFMustBeAtTheEnd, bool label)
       : MCObjectStreamer(Context, MAB, OS, Emitter), LabelSections(label),
         DWARFMustBeAtTheEnd(DWARFMustBeAtTheEnd), CreatedADWARFSection(false) {}
@@ -491,7 +491,7 @@ void MCMachOStreamer::FinishImpl() {
 }
 
 MCStreamer *llvm::createMachOStreamer(MCContext &Context, MCAsmBackend &MAB,
-                                      raw_ostream &OS, MCCodeEmitter *CE,
+                                      raw_pwrite_stream &OS, MCCodeEmitter *CE,
                                       bool RelaxAll, bool DWARFMustBeAtTheEnd,
                                       bool LabelSections) {
   MCMachOStreamer *S = new MCMachOStreamer(Context, MAB, OS, CE,
diff --git a/llvm/lib/MC/MCObjectStreamer.cpp b/llvm/lib/MC/MCObjectStreamer.cpp
index bf565765c869..d254e9509b44 100644
--- a/llvm/lib/MC/MCObjectStreamer.cpp
+++ b/llvm/lib/MC/MCObjectStreamer.cpp
@@ -24,7 +24,8 @@
 using namespace llvm;
 
 MCObjectStreamer::MCObjectStreamer(MCContext &Context, MCAsmBackend &TAB,
-                                   raw_ostream &OS, MCCodeEmitter *Emitter_)
+                                   raw_pwrite_stream &OS,
+                                   MCCodeEmitter *Emitter_)
     : MCStreamer(Context),
       Assembler(new MCAssembler(Context, TAB, *Emitter_,
                                 *TAB.createObjectWriter(OS), OS)),
diff --git a/llvm/lib/MC/MachObjectWriter.cpp b/llvm/lib/MC/MachObjectWriter.cpp
index 93ff75211c43..837f5857b66c 100644
--- a/llvm/lib/MC/MachObjectWriter.cpp
+++ b/llvm/lib/MC/MachObjectWriter.cpp
@@ -1007,7 +1007,7 @@ void MachObjectWriter::WriteObject(MCAssembler &Asm,
 }
 
 MCObjectWriter *llvm::createMachObjectWriter(MCMachObjectTargetWriter *MOTW,
-                                             raw_ostream &OS,
+                                             raw_pwrite_stream &OS,
                                              bool IsLittleEndian) {
   return new MachObjectWriter(MOTW, OS, IsLittleEndian);
 }
diff --git a/llvm/lib/MC/WinCOFFObjectWriter.cpp b/llvm/lib/MC/WinCOFFObjectWriter.cpp
index da4324733f09..38bb88335dd0 100644
--- a/llvm/lib/MC/WinCOFFObjectWriter.cpp
+++ b/llvm/lib/MC/WinCOFFObjectWriter.cpp
@@ -126,7 +126,7 @@ public:
 
   bool UseBigObj;
 
-  WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_ostream &OS);
+  WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW, raw_pwrite_stream &OS);
 
   void reset() override {
     memset(&Header, 0, sizeof(Header));
@@ -258,7 +258,7 @@ size_t COFFSection::size() {
 // WinCOFFObjectWriter class implementation
 
 WinCOFFObjectWriter::WinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
-                                         raw_ostream &OS)
+                                         raw_pwrite_stream &OS)
     : MCObjectWriter(OS, true), TargetObjectWriter(MOTW) {
   memset(&Header, 0, sizeof(Header));
 
@@ -1075,6 +1075,6 @@ void MCWinCOFFObjectTargetWriter::anchor() {}
 
 MCObjectWriter *
 llvm::createWinCOFFObjectWriter(MCWinCOFFObjectTargetWriter *MOTW,
-                                raw_ostream &OS) {
+                                raw_pwrite_stream &OS) {
   return new WinCOFFObjectWriter(MOTW, OS);
 }
diff --git a/llvm/lib/MC/WinCOFFStreamer.cpp b/llvm/lib/MC/WinCOFFStreamer.cpp
index f902d2bae4de..8f9aacbb1961 100644
--- a/llvm/lib/MC/WinCOFFStreamer.cpp
+++ b/llvm/lib/MC/WinCOFFStreamer.cpp
@@ -39,7 +39,7 @@ using namespace llvm;
 
 namespace llvm {
 MCWinCOFFStreamer::MCWinCOFFStreamer(MCContext &Context, MCAsmBackend &MAB,
-                                     MCCodeEmitter &CE, raw_ostream &OS)
+                                     MCCodeEmitter &CE, raw_pwrite_stream &OS)
     : MCObjectStreamer(Context, MAB, OS, &CE), CurSymbol(nullptr) {}
 
 void MCWinCOFFStreamer::EmitInstToData(const MCInst &Inst,
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
index 84b63a0a8eba..e5eb90c6d045 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
@@ -313,7 +313,7 @@ public:
   DarwinAArch64AsmBackend(const Target &T, const MCRegisterInfo &MRI)
       : AArch64AsmBackend(T), MRI(MRI) {}
 
-  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+  MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
     return createAArch64MachObjectWriter(OS, MachO::CPU_TYPE_ARM64,
                                          MachO::CPU_SUBTYPE_ARM64_ALL);
   }
@@ -461,7 +461,7 @@ public:
   ELFAArch64AsmBackend(const Target &T, uint8_t OSABI, bool IsLittleEndian)
     : AArch64AsmBackend(T), OSABI(OSABI), IsLittleEndian(IsLittleEndian) {}
 
-  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+  MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
     return createAArch64ELFObjectWriter(OS, OSABI, IsLittleEndian);
   }
 
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFObjectWriter.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFObjectWriter.cpp
index 8696a7404c40..1f516d1db896 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFObjectWriter.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFObjectWriter.cpp
@@ -248,7 +248,7 @@ unsigned AArch64ELFObjectWriter::GetRelocType(const MCValue &Target,
   llvm_unreachable("Unimplemented fixup -> relocation");
 }
 
-MCObjectWriter *llvm::createAArch64ELFObjectWriter(raw_ostream &OS,
+MCObjectWriter *llvm::createAArch64ELFObjectWriter(raw_pwrite_stream &OS,
                                                    uint8_t OSABI,
                                                    bool IsLittleEndian) {
   MCELFObjectTargetWriter *MOTW =
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp
index 6c9af3b799b3..540d1fc8f5b7 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.cpp
@@ -89,8 +89,8 @@ class AArch64ELFStreamer : public MCELFStreamer {
 public:
   friend class AArch64TargetELFStreamer;
 
-  AArch64ELFStreamer(MCContext &Context, MCAsmBackend &TAB, raw_ostream &OS,
-                     MCCodeEmitter *Emitter)
+  AArch64ELFStreamer(MCContext &Context, MCAsmBackend &TAB,
+                     raw_pwrite_stream &OS, MCCodeEmitter *Emitter)
       : MCELFStreamer(Context, TAB, OS, Emitter), MappingSymbolCounter(0),
         LastEMS(EMS_None) {}
 
@@ -211,8 +211,8 @@ MCTargetStreamer *createAArch64AsmTargetStreamer(MCStreamer &S,
 }
 
 MCELFStreamer *createAArch64ELFStreamer(MCContext &Context, MCAsmBackend &TAB,
-                                        raw_ostream &OS, MCCodeEmitter *Emitter,
-                                        bool RelaxAll) {
+                                        raw_pwrite_stream &OS,
+                                        MCCodeEmitter *Emitter, bool RelaxAll) {
   AArch64ELFStreamer *S = new AArch64ELFStreamer(Context, TAB, OS, Emitter);
   if (RelaxAll)
     S->getAssembler().setRelaxAll(true);
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.h b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.h
index 71b05ccdc6a8..ef48203c8bc0 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.h
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64ELFStreamer.h
@@ -19,8 +19,8 @@
 namespace llvm {
 
 MCELFStreamer *createAArch64ELFStreamer(MCContext &Context, MCAsmBackend &TAB,
-                                        raw_ostream &OS, MCCodeEmitter *Emitter,
-                                        bool RelaxAll);
+                                        raw_pwrite_stream &OS,
+                                        MCCodeEmitter *Emitter, bool RelaxAll);
 }
 
 #endif
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.cpp
index 8a7273bb7494..afad674db06c 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.cpp
@@ -123,14 +123,14 @@ static MCInstPrinter *createAArch64MCInstPrinter(const Triple &T,
 }
 
 static MCStreamer *createELFStreamer(const Triple &T, MCContext &Ctx,
-                                     MCAsmBackend &TAB, raw_ostream &OS,
+                                     MCAsmBackend &TAB, raw_pwrite_stream &OS,
                                      MCCodeEmitter *Emitter, bool RelaxAll) {
   return createAArch64ELFStreamer(Ctx, TAB, OS, Emitter, RelaxAll);
 }
 
 static MCStreamer *createMachOStreamer(MCContext &Ctx, MCAsmBackend &TAB,
-                                       raw_ostream &OS, MCCodeEmitter *Emitter,
-                                       bool RelaxAll,
+                                       raw_pwrite_stream &OS,
+                                       MCCodeEmitter *Emitter, bool RelaxAll,
                                        bool DWARFMustBeAtTheEnd) {
   return createMachOStreamer(Ctx, TAB, OS, Emitter, RelaxAll,
                              DWARFMustBeAtTheEnd,
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.h b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.h
index 6c39d5e0e1af..4705bdf546ff 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.h
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCTargetDesc.h
@@ -33,6 +33,7 @@ class StringRef;
 class Target;
 class Triple;
 class raw_ostream;
+class raw_pwrite_stream;
 
 extern Target TheAArch64leTarget;
 extern Target TheAArch64beTarget;
@@ -48,10 +49,12 @@ MCAsmBackend *createAArch64beAsmBackend(const Target &T,
                                         const MCRegisterInfo &MRI, StringRef TT,
                                         StringRef CPU);
 
-MCObjectWriter *createAArch64ELFObjectWriter(raw_ostream &OS, uint8_t OSABI,
+MCObjectWriter *createAArch64ELFObjectWriter(raw_pwrite_stream &OS,
+                                             uint8_t OSABI,
                                              bool IsLittleEndian);
 
-MCObjectWriter *createAArch64MachObjectWriter(raw_ostream &OS, uint32_t CPUType,
+MCObjectWriter *createAArch64MachObjectWriter(raw_pwrite_stream &OS,
+                                              uint32_t CPUType,
                                               uint32_t CPUSubtype);
 
 MCTargetStreamer *createAArch64AsmTargetStreamer(MCStreamer &S,
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp
index 3e98ba33a035..61649c441426 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64MachObjectWriter.cpp
@@ -413,7 +413,7 @@ void AArch64MachObjectWriter::RecordRelocation(
   Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
 }
 
-MCObjectWriter *llvm::createAArch64MachObjectWriter(raw_ostream &OS,
+MCObjectWriter *llvm::createAArch64MachObjectWriter(raw_pwrite_stream &OS,
                                                     uint32_t CPUType,
                                                     uint32_t CPUSubtype) {
   return createMachObjectWriter(
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackendDarwin.h b/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackendDarwin.h
index 3bd7ab73839a..ebef78937b5a 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackendDarwin.h
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackendDarwin.h
@@ -23,7 +23,7 @@ public:
     HasDataInCodeSupport = true;
   }
 
-  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+  MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
     return createARMMachObjectWriter(OS, /*Is64Bit=*/false, MachO::CPU_TYPE_ARM,
                                      Subtype);
   }
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackendELF.h b/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackendELF.h
index 4efd32515426..263c4c488acb 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackendELF.h
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackendELF.h
@@ -18,7 +18,7 @@ public:
   ARMAsmBackendELF(const Target &T, StringRef TT, uint8_t OSABI, bool IsLittle)
       : ARMAsmBackend(T, TT, IsLittle), OSABI(OSABI) {}
 
-  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+  MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
     return createARMELFObjectWriter(OS, OSABI, isLittle());
   }
 };
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackendWinCOFF.h b/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackendWinCOFF.h
index 33be347b03ac..f2c435820ad6 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackendWinCOFF.h
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackendWinCOFF.h
@@ -17,7 +17,7 @@ class ARMAsmBackendWinCOFF : public ARMAsmBackend {
 public:
   ARMAsmBackendWinCOFF(const Target &T, StringRef Triple)
       : ARMAsmBackend(T, Triple, true) {}
-  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+  MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
     return createARMWinCOFFObjectWriter(OS, /*Is64Bit=*/false);
   }
 };
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
index c5d358d764f5..f4fedeef650b 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
@@ -251,7 +251,7 @@ unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target,
   return Type;
 }
 
-MCObjectWriter *llvm::createARMELFObjectWriter(raw_ostream &OS,
+MCObjectWriter *llvm::createARMELFObjectWriter(raw_pwrite_stream &OS,
                                                uint8_t OSABI,
                                                bool IsLittleEndian) {
   MCELFObjectTargetWriter *MOTW = new ARMELFObjectWriter(OSABI);
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
index b116cb80137b..e7c777e26f9b 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
@@ -472,7 +472,7 @@ class ARMELFStreamer : public MCELFStreamer {
 public:
   friend class ARMTargetELFStreamer;
 
-  ARMELFStreamer(MCContext &Context, MCAsmBackend &TAB, raw_ostream &OS,
+  ARMELFStreamer(MCContext &Context, MCAsmBackend &TAB, raw_pwrite_stream &OS,
                  MCCodeEmitter *Emitter, bool IsThumb)
       : MCELFStreamer(Context, TAB, OS, Emitter), IsThumb(IsThumb),
         MappingSymbolCounter(0), LastEMS(EMS_None) {
@@ -1382,8 +1382,9 @@ MCTargetStreamer *createARMObjectTargetStreamer(MCStreamer &S,
 }
 
 MCELFStreamer *createARMELFStreamer(MCContext &Context, MCAsmBackend &TAB,
-                                    raw_ostream &OS, MCCodeEmitter *Emitter,
-                                    bool RelaxAll, bool IsThumb) {
+                                    raw_pwrite_stream &OS,
+                                    MCCodeEmitter *Emitter, bool RelaxAll,
+                                    bool IsThumb) {
     ARMELFStreamer *S = new ARMELFStreamer(Context, TAB, OS, Emitter, IsThumb);
     // FIXME: This should eventually end up somewhere else where more
     // intelligent flag decisions can be made. For now we are just maintaining
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp
index 2ce159d407b9..daa8af24476d 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp
@@ -310,14 +310,14 @@ static MCCodeGenInfo *createARMMCCodeGenInfo(StringRef TT, Reloc::Model RM,
 }
 
 static MCStreamer *createELFStreamer(const Triple &T, MCContext &Ctx,
-                                     MCAsmBackend &MAB, raw_ostream &OS,
+                                     MCAsmBackend &MAB, raw_pwrite_stream &OS,
                                      MCCodeEmitter *Emitter, bool RelaxAll) {
   return createARMELFStreamer(Ctx, MAB, OS, Emitter, false,
                               T.getArch() == Triple::thumb);
 }
 
 static MCStreamer *createARMMachOStreamer(MCContext &Ctx, MCAsmBackend &MAB,
-                                          raw_ostream &OS,
+                                          raw_pwrite_stream &OS,
                                           MCCodeEmitter *Emitter, bool RelaxAll,
                                           bool DWARFMustBeAtTheEnd) {
   return createMachOStreamer(Ctx, MAB, OS, Emitter, false, DWARFMustBeAtTheEnd);
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.h b/llvm/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.h
index e948525eb0bb..24ca567a8124 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.h
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.h
@@ -34,6 +34,7 @@ class StringRef;
 class Target;
 class Triple;
 class raw_ostream;
+class raw_pwrite_stream;
 
 extern Target TheARMLETarget, TheThumbLETarget;
 extern Target TheARMBETarget, TheThumbBETarget;
@@ -82,20 +83,21 @@ MCAsmBackend *createThumbBEAsmBackend(const Target &T, const MCRegisterInfo &MRI
 // Construct a PE/COFF machine code streamer which will generate a PE/COFF
 // object file.
 MCStreamer *createARMWinCOFFStreamer(MCContext &Context, MCAsmBackend &MAB,
-                                     raw_ostream &OS, MCCodeEmitter *Emitter,
-                                     bool RelaxAll);
+                                     raw_pwrite_stream &OS,
+                                     MCCodeEmitter *Emitter, bool RelaxAll);
 
 /// Construct an ELF Mach-O object writer.
-MCObjectWriter *createARMELFObjectWriter(raw_ostream &OS, uint8_t OSABI,
+MCObjectWriter *createARMELFObjectWriter(raw_pwrite_stream &OS, uint8_t OSABI,
                                          bool IsLittleEndian);
 
 /// Construct an ARM Mach-O object writer.
-MCObjectWriter *createARMMachObjectWriter(raw_ostream &OS, bool Is64Bit,
+MCObjectWriter *createARMMachObjectWriter(raw_pwrite_stream &OS, bool Is64Bit,
                                           uint32_t CPUType,
                                           uint32_t CPUSubtype);
 
 /// Construct an ARM PE/COFF object writer.
-MCObjectWriter *createARMWinCOFFObjectWriter(raw_ostream &OS, bool Is64Bit);
+MCObjectWriter *createARMWinCOFFObjectWriter(raw_pwrite_stream &OS,
+                                             bool Is64Bit);
 
 /// Construct ARM Mach-O relocation info.
 MCRelocationInfo *createARMMachORelocationInfo(MCContext &Ctx);
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp
index 5364328c3ca0..b1f9b5879187 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp
@@ -472,8 +472,8 @@ void ARMMachObjectWriter::RecordRelocation(MachObjectWriter *Writer,
   Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
 }
 
-MCObjectWriter *llvm::createARMMachObjectWriter(raw_ostream &OS, bool Is64Bit,
-                                                uint32_t CPUType,
+MCObjectWriter *llvm::createARMMachObjectWriter(raw_pwrite_stream &OS,
+                                                bool Is64Bit, uint32_t CPUType,
                                                 uint32_t CPUSubtype) {
   return createMachObjectWriter(new ARMMachObjectWriter(Is64Bit,
                                                         CPUType,
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMWinCOFFObjectWriter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMWinCOFFObjectWriter.cpp
index 41feaf407c6a..166c04b41a77 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMWinCOFFObjectWriter.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMWinCOFFObjectWriter.cpp
@@ -82,7 +82,8 @@ bool ARMWinCOFFObjectWriter::recordRelocation(const MCFixup &Fixup) const {
 }
 
 namespace llvm {
-MCObjectWriter *createARMWinCOFFObjectWriter(raw_ostream &OS, bool Is64Bit) {
+MCObjectWriter *createARMWinCOFFObjectWriter(raw_pwrite_stream &OS,
+                                             bool Is64Bit) {
   MCWinCOFFObjectTargetWriter *MOTW = new ARMWinCOFFObjectWriter(Is64Bit);
   return createWinCOFFObjectWriter(MOTW, OS);
 }
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMWinCOFFStreamer.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMWinCOFFStreamer.cpp
index dc707dc6bdc6..b993b1be4847 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMWinCOFFStreamer.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMWinCOFFStreamer.cpp
@@ -16,8 +16,8 @@ namespace {
 class ARMWinCOFFStreamer : public MCWinCOFFStreamer {
 public:
   ARMWinCOFFStreamer(MCContext &C, MCAsmBackend &AB, MCCodeEmitter &CE,
-                     raw_ostream &OS)
-    : MCWinCOFFStreamer(C, AB, CE, OS) { }
+                     raw_pwrite_stream &OS)
+      : MCWinCOFFStreamer(C, AB, CE, OS) {}
 
   void EmitAssemblerFlag(MCAssemblerFlag Flag) override;
   void EmitThumbFunc(MCSymbol *Symbol) override;
@@ -38,7 +38,8 @@ void ARMWinCOFFStreamer::EmitThumbFunc(MCSymbol *Symbol) {
 }
 
 MCStreamer *llvm::createARMWinCOFFStreamer(MCContext &Context,
-                                           MCAsmBackend &MAB, raw_ostream &OS,
+                                           MCAsmBackend &MAB,
+                                           raw_pwrite_stream &OS,
                                            MCCodeEmitter *Emitter,
                                            bool RelaxAll) {
   return new ARMWinCOFFStreamer(Context, MAB, *Emitter, OS);
diff --git a/llvm/lib/Target/CppBackend/CPPBackend.cpp b/llvm/lib/Target/CppBackend/CPPBackend.cpp
index 8a9437b75fff..0cb0beac8c12 100644
--- a/llvm/lib/Target/CppBackend/CPPBackend.cpp
+++ b/llvm/lib/Target/CppBackend/CPPBackend.cpp
@@ -2149,11 +2149,9 @@ char CppWriter::ID = 0;
 //                       External Interface declaration
 //===----------------------------------------------------------------------===//
 
-bool CPPTargetMachine::addPassesToEmitFile(PassManagerBase &PM, raw_ostream &o,
-                                           CodeGenFileType FileType,
-                                           bool DisableVerify,
-                                           AnalysisID StartAfter,
-                                           AnalysisID StopAfter) {
+bool CPPTargetMachine::addPassesToEmitFile(
+    PassManagerBase &PM, raw_pwrite_stream &o, CodeGenFileType FileType,
+    bool DisableVerify, AnalysisID StartAfter, AnalysisID StopAfter) {
   if (FileType != TargetMachine::CGFT_AssemblyFile)
     return true;
   auto FOut = llvm::make_unique<formatted_raw_ostream>(o);
diff --git a/llvm/lib/Target/CppBackend/CPPTargetMachine.h b/llvm/lib/Target/CppBackend/CPPTargetMachine.h
index 04f81e9e9665..02d705e2d8f3 100644
--- a/llvm/lib/Target/CppBackend/CPPTargetMachine.h
+++ b/llvm/lib/Target/CppBackend/CPPTargetMachine.h
@@ -29,7 +29,7 @@ struct CPPTargetMachine : public TargetMachine {
       : TargetMachine(T, "", TT, CPU, FS, Options) {}
 
 public:
-  bool addPassesToEmitFile(PassManagerBase &PM, raw_ostream &Out,
+  bool addPassesToEmitFile(PassManagerBase &PM, raw_pwrite_stream &Out,
                            CodeGenFileType FileType, bool DisableVerify,
                            AnalysisID StartAfter,
                            AnalysisID StopAfter) override;
diff --git a/llvm/lib/Target/Hexagon/MCTargetDesc/HexagonAsmBackend.cpp b/llvm/lib/Target/Hexagon/MCTargetDesc/HexagonAsmBackend.cpp
index bdccf880d65f..155aa9ef9557 100644
--- a/llvm/lib/Target/Hexagon/MCTargetDesc/HexagonAsmBackend.cpp
+++ b/llvm/lib/Target/Hexagon/MCTargetDesc/HexagonAsmBackend.cpp
@@ -57,7 +57,7 @@ public:
   ELFHexagonAsmBackend(Target const &T, uint8_t OSABI)
       : HexagonAsmBackend(T), OSABI(OSABI) {}
 
-  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+  MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
     StringRef CPU("HexagonV4");
     return createHexagonELFObjectWriter(OS, OSABI, CPU);
   }
diff --git a/llvm/lib/Target/Hexagon/MCTargetDesc/HexagonELFObjectWriter.cpp b/llvm/lib/Target/Hexagon/MCTargetDesc/HexagonELFObjectWriter.cpp
index 3ac0a7cc6c10..fde935b2758b 100644
--- a/llvm/lib/Target/Hexagon/MCTargetDesc/HexagonELFObjectWriter.cpp
+++ b/llvm/lib/Target/Hexagon/MCTargetDesc/HexagonELFObjectWriter.cpp
@@ -55,7 +55,7 @@ unsigned HexagonELFObjectWriter::GetRelocType(MCValue const &/*Target*/,
   return Type;
 }
 
-MCObjectWriter *llvm::createHexagonELFObjectWriter(raw_ostream &OS,
+MCObjectWriter *llvm::createHexagonELFObjectWriter(raw_pwrite_stream &OS,
                                                    uint8_t OSABI,
                                                    StringRef CPU) {
   MCELFObjectTargetWriter *MOTW = new HexagonELFObjectWriter(OSABI, CPU);
diff --git a/llvm/lib/Target/Hexagon/MCTargetDesc/HexagonMCTargetDesc.h b/llvm/lib/Target/Hexagon/MCTargetDesc/HexagonMCTargetDesc.h
index 17072d9970b9..de63fd271aea 100644
--- a/llvm/lib/Target/Hexagon/MCTargetDesc/HexagonMCTargetDesc.h
+++ b/llvm/lib/Target/Hexagon/MCTargetDesc/HexagonMCTargetDesc.h
@@ -27,6 +27,7 @@ class MCSubtargetInfo;
 class Target;
 class StringRef;
 class raw_ostream;
+class raw_pwrite_stream;
 
 extern Target TheHexagonTarget;
 
@@ -40,8 +41,8 @@ MCAsmBackend *createHexagonAsmBackend(Target const &T,
                                       MCRegisterInfo const &MRI, StringRef TT,
                                       StringRef CPU);
 
-MCObjectWriter *createHexagonELFObjectWriter(raw_ostream &OS, uint8_t OSABI,
-                                             StringRef CPU);
+MCObjectWriter *createHexagonELFObjectWriter(raw_pwrite_stream &OS,
+                                             uint8_t OSABI, StringRef CPU);
 
 } // End llvm namespace
 
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp b/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
index acf6f2163ed8..dbcd867b402b 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
@@ -155,7 +155,8 @@ static unsigned adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
   return Value;
 }
 
-MCObjectWriter *MipsAsmBackend::createObjectWriter(raw_ostream &OS) const {
+MCObjectWriter *
+MipsAsmBackend::createObjectWriter(raw_pwrite_stream &OS) const {
   return createMipsELFObjectWriter(OS,
     MCELFObjectTargetWriter::getOSABI(OSType), IsLittle, Is64Bit);
 }
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.h b/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.h
index 243b73d216ce..b3d5a4964f86 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.h
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.h
@@ -36,7 +36,7 @@ public:
                  bool Is64Bit)
       : MCAsmBackend(), OSType(OSType), IsLittle(IsLittle), Is64Bit(Is64Bit) {}
 
-  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override;
+  MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override;
 
   void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
                   uint64_t Value, bool IsPCRel) const override;
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp b/llvm/lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp
index 039d1fd3323a..8d9e3e31105e 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp
@@ -444,7 +444,8 @@ MipsELFObjectWriter::needsRelocateWithSymbol(const MCSymbolData &SD,
   }
 }
 
-MCObjectWriter *llvm::createMipsELFObjectWriter(raw_ostream &OS, uint8_t OSABI,
+MCObjectWriter *llvm::createMipsELFObjectWriter(raw_pwrite_stream &OS,
+                                                uint8_t OSABI,
                                                 bool IsLittleEndian,
                                                 bool Is64Bit) {
   MCELFObjectTargetWriter *MOTW =
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsELFStreamer.cpp b/llvm/lib/Target/Mips/MCTargetDesc/MipsELFStreamer.cpp
index 93f60dfb083e..8eb29074a225 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsELFStreamer.cpp
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsELFStreamer.cpp
@@ -70,7 +70,8 @@ void MipsELFStreamer::EmitMipsOptionRecords() {
 }
 
 MCELFStreamer *llvm::createMipsELFStreamer(MCContext &Context,
-                                           MCAsmBackend &MAB, raw_ostream &OS,
+                                           MCAsmBackend &MAB,
+                                           raw_pwrite_stream &OS,
                                            MCCodeEmitter *Emitter,
                                            bool RelaxAll) {
   return new MipsELFStreamer(Context, MAB, OS, Emitter);
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsELFStreamer.h b/llvm/lib/Target/Mips/MCTargetDesc/MipsELFStreamer.h
index 6b834c6be918..68ff751dd14f 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsELFStreamer.h
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsELFStreamer.h
@@ -33,7 +33,7 @@ class MipsELFStreamer : public MCELFStreamer {
 
 
 public:
-  MipsELFStreamer(MCContext &Context, MCAsmBackend &MAB, raw_ostream &OS,
+  MipsELFStreamer(MCContext &Context, MCAsmBackend &MAB, raw_pwrite_stream &OS,
                   MCCodeEmitter *Emitter)
       : MCELFStreamer(Context, MAB, OS, Emitter) {
 
@@ -68,7 +68,7 @@ public:
 };
 
 MCELFStreamer *createMipsELFStreamer(MCContext &Context, MCAsmBackend &MAB,
-                                     raw_ostream &OS, MCCodeEmitter *Emitter,
-                                     bool RelaxAll);
+                                     raw_pwrite_stream &OS,
+                                     MCCodeEmitter *Emitter, bool RelaxAll);
 } // namespace llvm.
 #endif
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsMCNaCl.h b/llvm/lib/Target/Mips/MCTargetDesc/MipsMCNaCl.h
index e6b5be796014..687b800c2409 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsMCNaCl.h
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsMCNaCl.h
@@ -23,9 +23,8 @@ bool baseRegNeedsLoadStoreMask(unsigned Reg);
 
 // This function creates an MCELFStreamer for Mips NaCl.
 MCELFStreamer *createMipsNaClELFStreamer(MCContext &Context, MCAsmBackend &TAB,
-                                         raw_ostream &OS,
-                                         MCCodeEmitter *Emitter,
-                                         bool RelaxAll);
+                                         raw_pwrite_stream &OS,
+                                         MCCodeEmitter *Emitter, bool RelaxAll);
 }
 
 #endif
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsMCTargetDesc.cpp b/llvm/lib/Target/Mips/MCTargetDesc/MipsMCTargetDesc.cpp
index f115a418dc03..a75d27d4b214 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsMCTargetDesc.cpp
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsMCTargetDesc.cpp
@@ -106,7 +106,7 @@ static MCInstPrinter *createMipsMCInstPrinter(const Triple &T,
 }
 
 static MCStreamer *createMCStreamer(const Triple &T, MCContext &Context,
-                                    MCAsmBackend &MAB, raw_ostream &OS,
+                                    MCAsmBackend &MAB, raw_pwrite_stream &OS,
                                     MCCodeEmitter *Emitter, bool RelaxAll) {
   MCStreamer *S;
   if (!T.isOSNaCl())
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsMCTargetDesc.h b/llvm/lib/Target/Mips/MCTargetDesc/MipsMCTargetDesc.h
index 92f394aa4111..577a8b3ea3bb 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsMCTargetDesc.h
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsMCTargetDesc.h
@@ -27,6 +27,7 @@ class MCSubtargetInfo;
 class StringRef;
 class Target;
 class raw_ostream;
+class raw_pwrite_stream;
 
 extern Target TheMipsTarget;
 extern Target TheMipselTarget;
@@ -53,7 +54,7 @@ MCAsmBackend *createMipsAsmBackendEL64(const Target &T,
                                        const MCRegisterInfo &MRI, StringRef TT,
                                        StringRef CPU);
 
-MCObjectWriter *createMipsELFObjectWriter(raw_ostream &OS, uint8_t OSABI,
+MCObjectWriter *createMipsELFObjectWriter(raw_pwrite_stream &OS, uint8_t OSABI,
                                           bool IsLittleEndian, bool Is64Bit);
 
 namespace MIPS_MC {
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsNaClELFStreamer.cpp b/llvm/lib/Target/Mips/MCTargetDesc/MipsNaClELFStreamer.cpp
index ec98027b7c33..35348aa9e35a 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsNaClELFStreamer.cpp
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsNaClELFStreamer.cpp
@@ -36,8 +36,8 @@ const unsigned LoadStoreStackMaskReg = Mips::T7;
 
 class MipsNaClELFStreamer : public MipsELFStreamer {
 public:
-  MipsNaClELFStreamer(MCContext &Context, MCAsmBackend &TAB, raw_ostream &OS,
-                      MCCodeEmitter *Emitter)
+  MipsNaClELFStreamer(MCContext &Context, MCAsmBackend &TAB,
+                      raw_pwrite_stream &OS, MCCodeEmitter *Emitter)
       : MipsELFStreamer(Context, TAB, OS, Emitter), PendingCall(false) {}
 
   ~MipsNaClELFStreamer() override {}
@@ -252,7 +252,7 @@ bool baseRegNeedsLoadStoreMask(unsigned Reg) {
 }
 
 MCELFStreamer *createMipsNaClELFStreamer(MCContext &Context, MCAsmBackend &TAB,
-                                         raw_ostream &OS,
+                                         raw_pwrite_stream &OS,
                                          MCCodeEmitter *Emitter,
                                          bool RelaxAll) {
   MipsNaClELFStreamer *S = new MipsNaClELFStreamer(Context, TAB, OS, Emitter);
diff --git a/llvm/lib/Target/NVPTX/NVPTXTargetMachine.h b/llvm/lib/Target/NVPTX/NVPTXTargetMachine.h
index b8df5affe5ba..2cd10e87f620 100644
--- a/llvm/lib/Target/NVPTX/NVPTXTargetMachine.h
+++ b/llvm/lib/Target/NVPTX/NVPTXTargetMachine.h
@@ -52,7 +52,7 @@ public:
   TargetPassConfig *createPassConfig(PassManagerBase &PM) override;
 
   // Emission of machine code through MCJIT is not supported.
-  bool addPassesToEmitMC(PassManagerBase &, MCContext *&, raw_ostream &,
+  bool addPassesToEmitMC(PassManagerBase &, MCContext *&, raw_pwrite_stream &,
                          bool = true) override {
     return true;
   }
diff --git a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
index bea88a2ff2c6..420c5c809a58 100644
--- a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
+++ b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
@@ -208,7 +208,7 @@ namespace {
   public:
     DarwinPPCAsmBackend(const Target &T) : PPCAsmBackend(T, false) { }
 
-    MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+    MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
       bool is64 = getPointerSize() == 8;
       return createPPCMachObjectWriter(
           OS,
@@ -224,8 +224,7 @@ namespace {
     ELFPPCAsmBackend(const Target &T, bool IsLittleEndian, uint8_t OSABI) :
       PPCAsmBackend(T, IsLittleEndian), OSABI(OSABI) { }
 
-
-    MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+    MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
       bool is64 = getPointerSize() == 8;
       return createPPCELFObjectWriter(OS, is64, isLittleEndian(), OSABI);
     }
diff --git a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp
index b5f5f5a181cb..3e3489fc46aa 100644
--- a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp
+++ b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp
@@ -412,7 +412,8 @@ bool PPCELFObjectWriter::needsRelocateWithSymbol(const MCSymbolData &SD,
   }
 }
 
-MCObjectWriter *llvm::createPPCELFObjectWriter(raw_ostream &OS, bool Is64Bit,
+MCObjectWriter *llvm::createPPCELFObjectWriter(raw_pwrite_stream &OS,
+                                               bool Is64Bit,
                                                bool IsLittleEndian,
                                                uint8_t OSABI) {
   MCELFObjectTargetWriter *MOTW = new PPCELFObjectWriter(Is64Bit, OSABI);
diff --git a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCTargetDesc.h b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCTargetDesc.h
index 8ff7e6c6f295..5f2117c88e46 100644
--- a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCTargetDesc.h
+++ b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCTargetDesc.h
@@ -30,6 +30,7 @@ class MCRegisterInfo;
 class MCSubtargetInfo;
 class Target;
 class StringRef;
+class raw_pwrite_stream;
 class raw_ostream;
 
 extern Target ThePPC32Target;
@@ -44,12 +45,10 @@ MCAsmBackend *createPPCAsmBackend(const Target &T, const MCRegisterInfo &MRI,
                                   StringRef TT, StringRef CPU);
 
 /// Construct an PPC ELF object writer.
-MCObjectWriter *createPPCELFObjectWriter(raw_ostream &OS,
-                                         bool Is64Bit,
-                                         bool IsLittleEndian,
-                                         uint8_t OSABI);
+MCObjectWriter *createPPCELFObjectWriter(raw_pwrite_stream &OS, bool Is64Bit,
+                                         bool IsLittleEndian, uint8_t OSABI);
 /// Construct a PPC Mach-O object writer.
-MCObjectWriter *createPPCMachObjectWriter(raw_ostream &OS, bool Is64Bit,
+MCObjectWriter *createPPCMachObjectWriter(raw_pwrite_stream &OS, bool Is64Bit,
                                           uint32_t CPUType,
                                           uint32_t CPUSubtype);
 
diff --git a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMachObjectWriter.cpp b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMachObjectWriter.cpp
index f7259b9a098c..44e69b7565d1 100644
--- a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMachObjectWriter.cpp
+++ b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMachObjectWriter.cpp
@@ -378,8 +378,8 @@ void PPCMachObjectWriter::RecordPPCRelocation(
   Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
 }
 
-MCObjectWriter *llvm::createPPCMachObjectWriter(raw_ostream &OS, bool Is64Bit,
-                                                uint32_t CPUType,
+MCObjectWriter *llvm::createPPCMachObjectWriter(raw_pwrite_stream &OS,
+                                                bool Is64Bit, uint32_t CPUType,
                                                 uint32_t CPUSubtype) {
   return createMachObjectWriter(
       new PPCMachObjectWriter(Is64Bit, CPUType, CPUSubtype), OS,
diff --git a/llvm/lib/Target/R600/MCTargetDesc/AMDGPUAsmBackend.cpp b/llvm/lib/Target/R600/MCTargetDesc/AMDGPUAsmBackend.cpp
index d0c634fb7e42..f33e692ac3cd 100644
--- a/llvm/lib/Target/R600/MCTargetDesc/AMDGPUAsmBackend.cpp
+++ b/llvm/lib/Target/R600/MCTargetDesc/AMDGPUAsmBackend.cpp
@@ -24,7 +24,7 @@ namespace {
 
 class AMDGPUMCObjectWriter : public MCObjectWriter {
 public:
-  AMDGPUMCObjectWriter(raw_ostream &OS) : MCObjectWriter(OS, true) { }
+  AMDGPUMCObjectWriter(raw_pwrite_stream &OS) : MCObjectWriter(OS, true) {}
   void ExecutePostLayoutBinding(MCAssembler &Asm,
                                 const MCAsmLayout &Layout) override {
     //XXX: Implement if necessary.
@@ -131,7 +131,7 @@ class ELFAMDGPUAsmBackend : public AMDGPUAsmBackend {
 public:
   ELFAMDGPUAsmBackend(const Target &T) : AMDGPUAsmBackend(T) { }
 
-  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+  MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
     return createAMDGPUELFObjectWriter(OS);
   }
 };
diff --git a/llvm/lib/Target/R600/MCTargetDesc/AMDGPUELFObjectWriter.cpp b/llvm/lib/Target/R600/MCTargetDesc/AMDGPUELFObjectWriter.cpp
index 5fb94d5914d4..59f45ff02d88 100644
--- a/llvm/lib/Target/R600/MCTargetDesc/AMDGPUELFObjectWriter.cpp
+++ b/llvm/lib/Target/R600/MCTargetDesc/AMDGPUELFObjectWriter.cpp
@@ -33,7 +33,7 @@ protected:
 AMDGPUELFObjectWriter::AMDGPUELFObjectWriter()
   : MCELFObjectTargetWriter(false, 0, 0, false) { }
 
-MCObjectWriter *llvm::createAMDGPUELFObjectWriter(raw_ostream &OS) {
+MCObjectWriter *llvm::createAMDGPUELFObjectWriter(raw_pwrite_stream &OS) {
   MCELFObjectTargetWriter *MOTW = new AMDGPUELFObjectWriter();
   return createELFObjectWriter(MOTW, OS, true);
 }
diff --git a/llvm/lib/Target/R600/MCTargetDesc/AMDGPUMCTargetDesc.h b/llvm/lib/Target/R600/MCTargetDesc/AMDGPUMCTargetDesc.h
index 23f019662e8d..9a7548e9fbf8 100644
--- a/llvm/lib/Target/R600/MCTargetDesc/AMDGPUMCTargetDesc.h
+++ b/llvm/lib/Target/R600/MCTargetDesc/AMDGPUMCTargetDesc.h
@@ -28,6 +28,7 @@ class MCObjectWriter;
 class MCRegisterInfo;
 class MCSubtargetInfo;
 class Target;
+class raw_pwrite_stream;
 class raw_ostream;
 
 extern Target TheAMDGPUTarget;
@@ -44,7 +45,7 @@ MCCodeEmitter *createSIMCCodeEmitter(const MCInstrInfo &MCII,
 MCAsmBackend *createAMDGPUAsmBackend(const Target &T, const MCRegisterInfo &MRI,
                                      StringRef TT, StringRef CPU);
 
-MCObjectWriter *createAMDGPUELFObjectWriter(raw_ostream &OS);
+MCObjectWriter *createAMDGPUELFObjectWriter(raw_pwrite_stream &OS);
 } // End llvm namespace
 
 #define GET_REGINFO_ENUM
diff --git a/llvm/lib/Target/Sparc/MCTargetDesc/SparcAsmBackend.cpp b/llvm/lib/Target/Sparc/MCTargetDesc/SparcAsmBackend.cpp
index dcd81e3d6249..4abb6b8d25da 100644
--- a/llvm/lib/Target/Sparc/MCTargetDesc/SparcAsmBackend.cpp
+++ b/llvm/lib/Target/Sparc/MCTargetDesc/SparcAsmBackend.cpp
@@ -244,7 +244,7 @@ namespace {
 
     }
 
-    MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+    MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
       uint8_t OSABI = MCELFObjectTargetWriter::getOSABI(OSType);
       return createSparcELFObjectWriter(OS, is64Bit(), OSABI);
     }
diff --git a/llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp b/llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp
index 2fefd0cd3b55..98ba7e6a631b 100644
--- a/llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp
+++ b/llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp
@@ -105,8 +105,8 @@ unsigned SparcELFObjectWriter::GetRelocType(const MCValue &Target,
   return ELF::R_SPARC_NONE;
 }
 
-MCObjectWriter *llvm::createSparcELFObjectWriter(raw_ostream &OS, bool Is64Bit,
-                                                 uint8_t OSABI) {
+MCObjectWriter *llvm::createSparcELFObjectWriter(raw_pwrite_stream &OS,
+                                                 bool Is64Bit, uint8_t OSABI) {
   MCELFObjectTargetWriter *MOTW = new SparcELFObjectWriter(Is64Bit, OSABI);
   return createELFObjectWriter(MOTW, OS,  /*IsLittleEndian=*/false);
 }
diff --git a/llvm/lib/Target/Sparc/MCTargetDesc/SparcMCTargetDesc.h b/llvm/lib/Target/Sparc/MCTargetDesc/SparcMCTargetDesc.h
index d2ec991b84c6..5f38b12403eb 100644
--- a/llvm/lib/Target/Sparc/MCTargetDesc/SparcMCTargetDesc.h
+++ b/llvm/lib/Target/Sparc/MCTargetDesc/SparcMCTargetDesc.h
@@ -26,6 +26,7 @@ class MCRegisterInfo;
 class MCSubtargetInfo;
 class Target;
 class StringRef;
+class raw_pwrite_stream;
 class raw_ostream;
 
 extern Target TheSparcTarget;
@@ -38,8 +39,7 @@ MCAsmBackend *createSparcAsmBackend(const Target &T,
                                     const MCRegisterInfo &MRI,
                                     StringRef TT,
                                     StringRef CPU);
-MCObjectWriter *createSparcELFObjectWriter(raw_ostream &OS,
-                                           bool Is64Bit,
+MCObjectWriter *createSparcELFObjectWriter(raw_pwrite_stream &OS, bool Is64Bit,
                                            uint8_t OSABI);
 } // End llvm namespace
 
diff --git a/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCAsmBackend.cpp b/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCAsmBackend.cpp
index b79b1d8f0795..1c3887ab5456 100644
--- a/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCAsmBackend.cpp
+++ b/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCAsmBackend.cpp
@@ -62,7 +62,7 @@ public:
     llvm_unreachable("SystemZ does do not have assembler relaxation");
   }
   bool writeNopData(uint64_t Count, MCObjectWriter *OW) const override;
-  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+  MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
     return createSystemZObjectWriter(OS, OSABI);
   }
 };
diff --git a/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCObjectWriter.cpp b/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCObjectWriter.cpp
index 35e7e97fecc0..ee1af023769e 100644
--- a/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCObjectWriter.cpp
+++ b/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCObjectWriter.cpp
@@ -152,7 +152,7 @@ unsigned SystemZObjectWriter::GetRelocType(const MCValue &Target,
   }
 }
 
-MCObjectWriter *llvm::createSystemZObjectWriter(raw_ostream &OS,
+MCObjectWriter *llvm::createSystemZObjectWriter(raw_pwrite_stream &OS,
                                                 uint8_t OSABI) {
   MCELFObjectTargetWriter *MOTW = new SystemZObjectWriter(OSABI);
   return createELFObjectWriter(MOTW, OS, /*IsLittleEndian=*/false);
diff --git a/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCTargetDesc.h b/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCTargetDesc.h
index 962c95060498..2b2647bae946 100644
--- a/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCTargetDesc.h
+++ b/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCTargetDesc.h
@@ -23,6 +23,7 @@ class MCRegisterInfo;
 class MCSubtargetInfo;
 class StringRef;
 class Target;
+class raw_pwrite_stream;
 class raw_ostream;
 
 extern Target TheSystemZTarget;
@@ -77,7 +78,7 @@ MCAsmBackend *createSystemZMCAsmBackend(const Target &T,
                                         const MCRegisterInfo &MRI,
                                         StringRef TT, StringRef CPU);
 
-MCObjectWriter *createSystemZObjectWriter(raw_ostream &OS, uint8_t OSABI);
+MCObjectWriter *createSystemZObjectWriter(raw_pwrite_stream &OS, uint8_t OSABI);
 } // end namespace llvm
 
 // Defines symbolic names for SystemZ registers.
diff --git a/llvm/lib/Target/TargetMachineC.cpp b/llvm/lib/Target/TargetMachineC.cpp
index afba80f0f050..1a5bf163bd9f 100644
--- a/llvm/lib/Target/TargetMachineC.cpp
+++ b/llvm/lib/Target/TargetMachineC.cpp
@@ -183,7 +183,7 @@ void LLVMSetTargetMachineAsmVerbosity(LLVMTargetMachineRef T,
 }
 
 static LLVMBool LLVMTargetMachineEmit(LLVMTargetMachineRef T, LLVMModuleRef M,
-                                      raw_ostream &OS,
+                                      raw_pwrite_stream &OS,
                                       LLVMCodeGenFileType codegen,
                                       char **ErrorMessage) {
   TargetMachine* TM = unwrap(T);
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
index a400d466e3d7..b84c98355031 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
@@ -360,7 +360,7 @@ public:
   ELFX86_32AsmBackend(const Target &T, uint8_t OSABI, StringRef CPU)
     : ELFX86AsmBackend(T, OSABI, CPU) {}
 
-  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+  MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
     return createX86ELFObjectWriter(OS, /*IsELF64*/ false, OSABI, ELF::EM_386);
   }
 };
@@ -370,7 +370,7 @@ public:
   ELFX86_X32AsmBackend(const Target &T, uint8_t OSABI, StringRef CPU)
       : ELFX86AsmBackend(T, OSABI, CPU) {}
 
-  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+  MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
     return createX86ELFObjectWriter(OS, /*IsELF64*/ false, OSABI,
                                     ELF::EM_X86_64);
   }
@@ -381,7 +381,7 @@ public:
   ELFX86_64AsmBackend(const Target &T, uint8_t OSABI, StringRef CPU)
     : ELFX86AsmBackend(T, OSABI, CPU) {}
 
-  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+  MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
     return createX86ELFObjectWriter(OS, /*IsELF64*/ true, OSABI, ELF::EM_X86_64);
   }
 };
@@ -395,7 +395,7 @@ public:
     , Is64Bit(is64Bit) {
   }
 
-  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+  MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
     return createX86WinCOFFObjectWriter(OS, Is64Bit);
   }
 };
@@ -752,7 +752,7 @@ public:
                          StringRef CPU)
       : DarwinX86AsmBackend(T, MRI, CPU, false) {}
 
-  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+  MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
     return createX86MachObjectWriter(OS, /*Is64Bit=*/false,
                                      MachO::CPU_TYPE_I386,
                                      MachO::CPU_SUBTYPE_I386_ALL);
@@ -772,7 +772,7 @@ public:
                          StringRef CPU, MachO::CPUSubTypeX86 st)
       : DarwinX86AsmBackend(T, MRI, CPU, true), Subtype(st) {}
 
-  MCObjectWriter *createObjectWriter(raw_ostream &OS) const override {
+  MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
     return createX86MachObjectWriter(OS, /*Is64Bit=*/true,
                                      MachO::CPU_TYPE_X86_64, Subtype);
   }
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
index 4b4d839931b1..45088835cfb9 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86ELFObjectWriter.cpp
@@ -249,8 +249,8 @@ unsigned X86ELFObjectWriter::GetRelocType(const MCValue &Target,
   return getRelocType32(Modifier, getType32(Type), IsPCRel);
 }
 
-MCObjectWriter *llvm::createX86ELFObjectWriter(raw_ostream &OS, bool IsELF64,
-                                               uint8_t OSABI,
+MCObjectWriter *llvm::createX86ELFObjectWriter(raw_pwrite_stream &OS,
+                                               bool IsELF64, uint8_t OSABI,
                                                uint16_t EMachine) {
   MCELFObjectTargetWriter *MOTW =
     new X86ELFObjectWriter(IsELF64, OSABI, EMachine);
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.h b/llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.h
index ec30d9975c97..dcdae1dbc469 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.h
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.h
@@ -31,6 +31,7 @@ class Target;
 class Triple;
 class StringRef;
 class raw_ostream;
+class raw_pwrite_stream;
 
 extern Target TheX86_32Target, TheX86_64Target;
 
@@ -77,19 +78,20 @@ MCAsmBackend *createX86_64AsmBackend(const Target &T, const MCRegisterInfo &MRI,
 ///
 /// Takes ownership of \p AB and \p CE.
 MCStreamer *createX86WinCOFFStreamer(MCContext &C, MCAsmBackend &AB,
-                                     raw_ostream &OS, MCCodeEmitter *CE,
+                                     raw_pwrite_stream &OS, MCCodeEmitter *CE,
                                      bool RelaxAll);
 
 /// Construct an X86 Mach-O object writer.
-MCObjectWriter *createX86MachObjectWriter(raw_ostream &OS, bool Is64Bit,
+MCObjectWriter *createX86MachObjectWriter(raw_pwrite_stream &OS, bool Is64Bit,
                                           uint32_t CPUType,
                                           uint32_t CPUSubtype);
 
 /// Construct an X86 ELF object writer.
-MCObjectWriter *createX86ELFObjectWriter(raw_ostream &OS, bool IsELF64,
+MCObjectWriter *createX86ELFObjectWriter(raw_pwrite_stream &OS, bool IsELF64,
                                          uint8_t OSABI, uint16_t EMachine);
 /// Construct an X86 Win COFF object writer.
-MCObjectWriter *createX86WinCOFFObjectWriter(raw_ostream &OS, bool Is64Bit);
+MCObjectWriter *createX86WinCOFFObjectWriter(raw_pwrite_stream &OS,
+                                             bool Is64Bit);
 
 /// Construct X86-64 Mach-O relocation info.
 MCRelocationInfo *createX86_64MachORelocationInfo(MCContext &Ctx);
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
index 2c1230fe6e8a..38539cd7bee5 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp
@@ -575,8 +575,8 @@ void X86MachObjectWriter::RecordX86Relocation(MachObjectWriter *Writer,
   Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
 }
 
-MCObjectWriter *llvm::createX86MachObjectWriter(raw_ostream &OS, bool Is64Bit,
-                                                uint32_t CPUType,
+MCObjectWriter *llvm::createX86MachObjectWriter(raw_pwrite_stream &OS,
+                                                bool Is64Bit, uint32_t CPUType,
                                                 uint32_t CPUSubtype) {
   return createMachObjectWriter(new X86MachObjectWriter(Is64Bit,
                                                         CPUType,
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFObjectWriter.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFObjectWriter.cpp
index 50392877ba61..bd1bc9943b6d 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFObjectWriter.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFObjectWriter.cpp
@@ -90,7 +90,7 @@ unsigned X86WinCOFFObjectWriter::getRelocType(const MCValue &Target,
     llvm_unreachable("Unsupported COFF machine type.");
 }
 
-MCObjectWriter *llvm::createX86WinCOFFObjectWriter(raw_ostream &OS,
+MCObjectWriter *llvm::createX86WinCOFFObjectWriter(raw_pwrite_stream &OS,
                                                    bool Is64Bit) {
   MCWinCOFFObjectTargetWriter *MOTW = new X86WinCOFFObjectWriter(Is64Bit);
   return createWinCOFFObjectWriter(MOTW, OS);
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFStreamer.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFStreamer.cpp
index 5690efe22aff..92f42b68ae51 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFStreamer.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86WinCOFFStreamer.cpp
@@ -18,8 +18,8 @@ class X86WinCOFFStreamer : public MCWinCOFFStreamer {
   Win64EH::UnwindEmitter EHStreamer;
 public:
   X86WinCOFFStreamer(MCContext &C, MCAsmBackend &AB, MCCodeEmitter *CE,
-                     raw_ostream &OS)
-    : MCWinCOFFStreamer(C, AB, *CE, OS) { }
+                     raw_pwrite_stream &OS)
+      : MCWinCOFFStreamer(C, AB, *CE, OS) {}
 
   void EmitWinEHHandlerData() override;
   void EmitWindowsUnwindTables() override;
@@ -49,8 +49,8 @@ void X86WinCOFFStreamer::FinishImpl() {
 }
 
 MCStreamer *llvm::createX86WinCOFFStreamer(MCContext &C, MCAsmBackend &AB,
-                                           raw_ostream &OS, MCCodeEmitter *CE,
-                                           bool RelaxAll) {
+                                           raw_pwrite_stream &OS,
+                                           MCCodeEmitter *CE, bool RelaxAll) {
   X86WinCOFFStreamer *S = new X86WinCOFFStreamer(C, AB, CE, OS);
   S->getAssembler().setRelaxAll(RelaxAll);
   return S;
diff --git a/llvm/tools/llc/llc.cpp b/llvm/tools/llc/llc.cpp
index c20adfd9021f..ab50f2a78024 100644
--- a/llvm/tools/llc/llc.cpp
+++ b/llvm/tools/llc/llc.cpp
@@ -335,6 +335,14 @@ static int compileModule(char **argv, LLVMContext &Context) {
              << ": warning: ignoring -mc-relax-all because filetype != obj";
 
   {
+    raw_pwrite_stream *OS = &Out->os();
+    std::unique_ptr<buffer_ostream> BOS;
+    if (FileType != TargetMachine::CGFT_AssemblyFile &&
+        !Out->os().supportsSeeking()) {
+      BOS = make_unique<buffer_ostream>(*OS);
+      OS = BOS.get();
+    }
+
     AnalysisID StartAfterID = nullptr;
     AnalysisID StopAfterID = nullptr;
     const PassRegistry *PR = PassRegistry::getPassRegistry();
@@ -356,8 +364,8 @@ static int compileModule(char **argv, LLVMContext &Context) {
     }
 
     // Ask the target to add backend passes as necessary.
-    if (Target->addPassesToEmitFile(PM, Out->os(), FileType, NoVerify,
-                                    StartAfterID, StopAfterID)) {
+    if (Target->addPassesToEmitFile(PM, *OS, FileType, NoVerify, StartAfterID,
+                                    StopAfterID)) {
       errs() << argv[0] << ": target does not support generation of this"
              << " file type!\n";
       return 1;
diff --git a/llvm/tools/llvm-mc/llvm-mc.cpp b/llvm/tools/llvm-mc/llvm-mc.cpp
index 58fe233fce15..6a8b49373df5 100644
--- a/llvm/tools/llvm-mc/llvm-mc.cpp
+++ b/llvm/tools/llvm-mc/llvm-mc.cpp
@@ -439,6 +439,8 @@ int main(int argc, char **argv) {
   if (!Out)
     return 1;
 
+  std::unique_ptr<buffer_ostream> BOS;
+  raw_pwrite_stream *OS = &Out->os();
   std::unique_ptr<MCStreamer> Str;
 
   std::unique_ptr<MCInstrInfo> MCII(TheTarget->createMCInstrInfo());
@@ -460,7 +462,7 @@ int main(int argc, char **argv) {
       CE = TheTarget->createMCCodeEmitter(*MCII, *MRI, Ctx);
       MAB = TheTarget->createMCAsmBackend(*MRI, TripleName, MCPU);
     }
-    auto FOut = llvm::make_unique<formatted_raw_ostream>(Out->os());
+    auto FOut = llvm::make_unique<formatted_raw_ostream>(*OS);
     Str.reset(TheTarget->createAsmStreamer(
         Ctx, std::move(FOut), /*asmverbose*/ true,
         /*useDwarfDirectory*/ true, IP, CE, MAB, ShowInst));
@@ -469,10 +471,16 @@ int main(int argc, char **argv) {
     Str.reset(TheTarget->createNullStreamer(Ctx));
   } else {
     assert(FileType == OFT_ObjectFile && "Invalid file type!");
+
+    if (!Out->os().supportsSeeking()) {
+      BOS = make_unique<buffer_ostream>(Out->os());
+      OS = BOS.get();
+    }
+
     MCCodeEmitter *CE = TheTarget->createMCCodeEmitter(*MCII, *MRI, Ctx);
     MCAsmBackend *MAB = TheTarget->createMCAsmBackend(*MRI, TripleName, MCPU);
-    Str.reset(TheTarget->createMCObjectStreamer(TheTriple, Ctx, *MAB, Out->os(),
-                                                CE, *STI, RelaxAll,
+    Str.reset(TheTarget->createMCObjectStreamer(TheTriple, Ctx, *MAB, *OS, CE,
+                                                *STI, RelaxAll,
                                                 /*DWARFMustBeAtTheEnd*/ false));
     if (NoExecStack)
       Str->InitSections(true);