[MC] Thread unique_ptr<MCObjectWriter> through the create.*ObjectWriter
functions.

This makes the ownership of the resulting MCObjectWriter clear, and allows us
to remove one instance of MCObjectStreamer's bizarre "holding ownership via
someone else's reference" trick.

llvm-svn: 315327
diff --git a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
index bdad2fe..2a1de24 100644
--- a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
+++ b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
@@ -204,7 +204,8 @@
   public:
     DarwinPPCAsmBackend(const Target &T) : PPCAsmBackend(T, false) { }
 
-    MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
+    std::unique_ptr<MCObjectWriter>
+    createObjectWriter(raw_pwrite_stream &OS) const override {
       bool is64 = getPointerSize() == 8;
       return createPPCMachObjectWriter(
           OS,
@@ -220,7 +221,8 @@
     ELFPPCAsmBackend(const Target &T, bool IsLittleEndian, uint8_t OSABI) :
       PPCAsmBackend(T, IsLittleEndian), OSABI(OSABI) { }
 
-    MCObjectWriter *createObjectWriter(raw_pwrite_stream &OS) const override {
+    std::unique_ptr<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 06d8462..44ee973 100644
--- a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp
+++ b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp
@@ -13,6 +13,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/MC/MCELFObjectWriter.h"
 #include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCObjectWriter.h"
 #include "llvm/MC/MCSymbolELF.h"
 #include "llvm/MC/MCValue.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -416,10 +417,9 @@
   }
 }
 
-MCObjectWriter *llvm::createPPCELFObjectWriter(raw_pwrite_stream &OS,
-                                               bool Is64Bit,
-                                               bool IsLittleEndian,
-                                               uint8_t OSABI) {
+std::unique_ptr<MCObjectWriter>
+llvm::createPPCELFObjectWriter(raw_pwrite_stream &OS, bool Is64Bit,
+                               bool IsLittleEndian, uint8_t OSABI) {
   auto MOTW = llvm::make_unique<PPCELFObjectWriter>(Is64Bit, OSABI);
   return createELFObjectWriter(std::move(MOTW), OS, IsLittleEndian);
 }
diff --git a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCTargetDesc.h b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCTargetDesc.h
index 893233e..960a576 100644
--- a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCTargetDesc.h
+++ b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCTargetDesc.h
@@ -47,12 +47,15 @@
                                   const MCTargetOptions &Options);
 
 /// Construct an PPC ELF object writer.
-MCObjectWriter *createPPCELFObjectWriter(raw_pwrite_stream &OS, bool Is64Bit,
-                                         bool IsLittleEndian, uint8_t OSABI);
+std::unique_ptr<MCObjectWriter> createPPCELFObjectWriter(raw_pwrite_stream &OS,
+                                                         bool Is64Bit,
+                                                         bool IsLittleEndian,
+                                                         uint8_t OSABI);
 /// Construct a PPC Mach-O object writer.
-MCObjectWriter *createPPCMachObjectWriter(raw_pwrite_stream &OS, bool Is64Bit,
-                                          uint32_t CPUType,
-                                          uint32_t CPUSubtype);
+std::unique_ptr<MCObjectWriter> createPPCMachObjectWriter(raw_pwrite_stream &OS,
+                                                          bool Is64Bit,
+                                                          uint32_t CPUType,
+                                                          uint32_t CPUSubtype);
 
 /// Returns true iff Val consists of one contiguous run of 1s with any number of
 /// 0s on either side.  The 1s are allowed to wrap from LSB to MSB, so
diff --git a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMachObjectWriter.cpp b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMachObjectWriter.cpp
index baa6707..4b9055e 100644
--- a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMachObjectWriter.cpp
+++ b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMachObjectWriter.cpp
@@ -374,9 +374,9 @@
   Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
 }
 
-MCObjectWriter *llvm::createPPCMachObjectWriter(raw_pwrite_stream &OS,
-                                                bool Is64Bit, uint32_t CPUType,
-                                                uint32_t CPUSubtype) {
+std::unique_ptr<MCObjectWriter>
+llvm::createPPCMachObjectWriter(raw_pwrite_stream &OS, bool Is64Bit,
+                                uint32_t CPUType, uint32_t CPUSubtype) {
   return createMachObjectWriter(
       llvm::make_unique<PPCMachObjectWriter>(Is64Bit, CPUType, CPUSubtype), OS,
       /*IsLittleEndian=*/false);