Index: include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
===================================================================
--- include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
+++ include/llvm/CodeGen/TargetLoweringObjectFileImpl.h
@@ -147,6 +147,10 @@
                            SectionKind Kind, Mangler &Mang,
                            const TargetMachine &TM) const override;
 
+  void getNameWithPrefix(SmallVectorImpl<char> &OutName, const GlobalValue *GV,
+                         bool CannotUsePrivateLabel, Mangler &Mang,
+                         const TargetMachine &TM) const override;
+
   const MCSection *
   getSectionForJumpTable(const Function &F, Mangler &Mang,
                          const TargetMachine &TM) const override;
Index: include/llvm/IR/DataLayout.h
===================================================================
--- include/llvm/IR/DataLayout.h
+++ include/llvm/IR/DataLayout.h
@@ -108,7 +108,14 @@
 
   unsigned StackNaturalAlign;
 
-  enum ManglingModeT { MM_None, MM_ELF, MM_MachO, MM_WINCOFF, MM_Mips };
+  enum ManglingModeT {
+    MM_None,
+    MM_ELF,
+    MM_MachO,
+    MM_WinCOFF,
+    MM_WinCOFFX86,
+    MM_Mips
+  };
   ManglingModeT ManglingMode;
 
   SmallVector<unsigned char, 8> LegalIntWidths;
@@ -244,7 +251,7 @@
   unsigned getStackAlignment() const { return StackNaturalAlign; }
 
   bool hasMicrosoftFastStdCallMangling() const {
-    return ManglingMode == MM_WINCOFF;
+    return ManglingMode == MM_WinCOFFX86;
   }
 
   bool hasLinkerPrivateGlobalPrefix() const { return ManglingMode == MM_MachO; }
@@ -252,7 +259,7 @@
   const char *getLinkerPrivateGlobalPrefix() const {
     if (ManglingMode == MM_MachO)
       return "l";
-    return getPrivateGlobalPrefix();
+    return "";
   }
 
   char getGlobalPrefix() const {
@@ -260,9 +267,10 @@
     case MM_None:
     case MM_ELF:
     case MM_Mips:
+    case MM_WinCOFF:
       return '\0';
     case MM_MachO:
-    case MM_WINCOFF:
+    case MM_WinCOFFX86:
       return '_';
     }
     llvm_unreachable("invalid mangling mode");
@@ -277,7 +285,8 @@
     case MM_Mips:
       return "$";
     case MM_MachO:
-    case MM_WINCOFF:
+    case MM_WinCOFF:
+    case MM_WinCOFFX86:
       return "L";
     }
     llvm_unreachable("invalid mangling mode");
Index: include/llvm/Target/TargetLoweringObjectFile.h
===================================================================
--- include/llvm/Target/TargetLoweringObjectFile.h
+++ include/llvm/Target/TargetLoweringObjectFile.h
@@ -101,6 +101,11 @@
     return SectionForGlobal(GV, getKindForGlobal(GV, TM), Mang, TM);
   }
 
+  virtual void getNameWithPrefix(SmallVectorImpl<char> &OutName,
+                                 const GlobalValue *GV,
+                                 bool CannotUsePrivateLabel, Mangler &Mang,
+                                 const TargetMachine &TM) const;
+
   virtual const MCSection *
   getSectionForJumpTable(const Function &F, Mangler &Mang,
                          const TargetMachine &TM) const;
Index: lib/CodeGen/TargetLoweringObjectFileImpl.cpp
===================================================================
--- lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -927,6 +927,11 @@
       StringRef COMDATSymName = Sym->getName();
       return getContext().getCOFFSection(Name, Characteristics, Kind,
                                          COMDATSymName, Selection);
+    } else {
+      SmallString<256> TmpData;
+      getNameWithPrefix(TmpData, GV, /*CannotUsePrivateLabel=*/true, Mang, TM);
+      return getContext().getCOFFSection(Name, Characteristics, Kind, TmpData,
+                                         Selection);
     }
   }
 
@@ -948,6 +953,17 @@
   return DataSection;
 }
 
+void TargetLoweringObjectFileCOFF::getNameWithPrefix(
+    SmallVectorImpl<char> &OutName, const GlobalValue *GV,
+    bool CannotUsePrivateLabel, Mangler &Mang, const TargetMachine &TM) const {
+  if (GV->hasPrivateLinkage() &&
+      ((isa<Function>(GV) && TM.getFunctionSections()) ||
+       (isa<GlobalVariable>(GV) && TM.getDataSections())))
+    CannotUsePrivateLabel = true;
+
+  Mang.getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
+}
+
 const MCSection *TargetLoweringObjectFileCOFF::getSectionForJumpTable(
     const Function &F, Mangler &Mang, const TargetMachine &TM) const {
   // If the function can be removed, produce a unique section so that
Index: lib/IR/DataLayout.cpp
===================================================================
--- lib/IR/DataLayout.cpp
+++ lib/IR/DataLayout.cpp
@@ -150,8 +150,8 @@
 const char *DataLayout::getManglingComponent(const Triple &T) {
   if (T.isOSBinFormatMachO())
     return "-m:o";
-  if (T.isOSWindows() && T.getArch() == Triple::x86 && T.isOSBinFormatCOFF())
-    return "-m:w";
+  if (T.isOSWindows() && T.isOSBinFormatCOFF())
+    return T.getArch() == Triple::x86 ? "-m:x" : "-m:w";
   return "-m:e";
 }
 
@@ -359,7 +359,10 @@
         ManglingMode = MM_Mips;
         break;
       case 'w':
-        ManglingMode = MM_WINCOFF;
+        ManglingMode = MM_WinCOFF;
+        break;
+      case 'x':
+        ManglingMode = MM_WinCOFFX86;
         break;
       }
       break;
Index: lib/Target/TargetLoweringObjectFile.cpp
===================================================================
--- lib/Target/TargetLoweringObjectFile.cpp
+++ lib/Target/TargetLoweringObjectFile.cpp
@@ -343,3 +343,9 @@
   // null return could mean 'no location' & we should just do that here.
   return MCSymbolRefExpr::Create(Sym, *Ctx);
 }
+
+void TargetLoweringObjectFile::getNameWithPrefix(
+    SmallVectorImpl<char> &OutName, const GlobalValue *GV,
+    bool CannotUsePrivateLabel, Mangler &Mang, const TargetMachine &TM) const {
+  Mang.getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
+}
Index: lib/Target/TargetMachine.cpp
===================================================================
--- lib/Target/TargetMachine.cpp
+++ lib/Target/TargetMachine.cpp
@@ -175,7 +175,7 @@
   const TargetLoweringObjectFile *TLOF = getObjFileLowering();
   const MCSection *TheSection = TLOF->SectionForGlobal(GV, GVKind, Mang, *this);
   bool CannotUsePrivateLabel = !canUsePrivateLabel(*AsmInfo, *TheSection);
-  Mang.getNameWithPrefix(Name, GV, CannotUsePrivateLabel);
+  TLOF->getNameWithPrefix(Name, GV, CannotUsePrivateLabel, Mang, *this);
 }
 
 MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV, Mangler &Mang) const {
Index: test/CodeGen/ARM/Windows/long-calls.ll
===================================================================
--- test/CodeGen/ARM/Windows/long-calls.ll
+++ test/CodeGen/ARM/Windows/long-calls.ll
@@ -10,7 +10,7 @@
 }
 
 ; CHECK-LABEL: caller
-; CHECK: ldr [[REG:r[0-9]+]], [[CPI:.LCPI[_0-9]+]]
+; CHECK: ldr [[REG:r[0-9]+]], [[CPI:LCPI[_0-9]+]]
 ; CHECK: bx [[REG]]
 ; CHECK: .align 2
 ; CHECK: [[CPI]]:
Index: test/CodeGen/X86/fastcall-correct-mangling.ll
===================================================================
--- test/CodeGen/X86/fastcall-correct-mangling.ll
+++ test/CodeGen/X86/fastcall-correct-mangling.ll
@@ -28,6 +28,6 @@
 define private x86_fastcallcc void @dontCrash() {
 ; The name is fairly arbitrary since it is private. Just don't crash.
 ; CHECK32-LABEL: {{^}}L@dontCrash@0:
-; CHECK64-LABEL: {{^}}.LdontCrash:
+; CHECK64-LABEL: {{^}}LdontCrash:
   ret void
 }
Index: test/CodeGen/X86/global-sections.ll
===================================================================
--- test/CodeGen/X86/global-sections.ll
+++ test/CodeGen/X86/global-sections.ll
@@ -275,8 +275,8 @@
 ; LINUX-SECTIONS:        .asciz  "foo"
 ; LINUX-SECTIONS:        .size   .LG14, 4
 
-; WIN32-SECTIONS:        .section        .rdata,"dr"
-; WIN32-SECTIONS: L_G14:
+; WIN32-SECTIONS:        .section        .rdata,"dr",one_only,_G14
+; WIN32-SECTIONS: _G14:
 ; WIN32-SECTIONS:        .asciz  "foo"
 
 ; cannot be merged on MachO, but can on other formats.