Index: COFF/Driver.h
===================================================================
--- COFF/Driver.h
+++ COFF/Driver.h
@@ -103,7 +103,6 @@
   std::set<std::string> VisitedLibs;
 
   Symbol *addUndefined(StringRef Sym);
-  StringRef mangle(StringRef Sym);
 
   // Windows specific -- "main" is not the only main function in Windows.
   // You can choose one from these four -- {w,}{WinMain,main}.
Index: COFF/Driver.cpp
===================================================================
--- COFF/Driver.cpp
+++ COFF/Driver.cpp
@@ -116,6 +116,19 @@
   });
 }
 
+// Symbol names are mangled by prepending "_" on x86.
+static StringRef mangle(StringRef Sym) {
+  assert(Config->Machine != IMAGE_FILE_MACHINE_UNKNOWN);
+  if (Config->Machine == I386)
+    return Saver.save("_" + Sym);
+  return Sym;
+}
+
+static bool findUnderscoreMangle(StringRef Sym) {
+  StringRef Entry = Symtab->findMangle(mangle(Sym));
+  return !Entry.empty() && !isa<Undefined>(Symtab->find(Entry));
+}
+
 MemoryBufferRef LinkerDriver::takeBuffer(std::unique_ptr<MemoryBuffer> MB) {
   MemoryBufferRef MBRef = *MB;
   make<std::unique_ptr<MemoryBuffer>>(std::move(MB)); // take ownership
@@ -407,14 +420,6 @@
   return B;
 }
 
-// Symbol names are mangled by appending "_" prefix on x86.
-StringRef LinkerDriver::mangle(StringRef Sym) {
-  assert(Config->Machine != IMAGE_FILE_MACHINE_UNKNOWN);
-  if (Config->Machine == I386)
-    return Saver.save("_" + Sym);
-  return Sym;
-}
-
 // Windows specific -- find default entry point name.
 //
 // There are four different entry point functions for Windows executables,
@@ -427,8 +432,7 @@
   if (Config->NoDefaultLibAll) {
     for (StringRef S : {"mainCRTStartup", "wmainCRTStartup",
                         "WinMainCRTStartup", "wWinMainCRTStartup"}) {
-      StringRef Entry = Symtab->findMangle(S);
-      if (!Entry.empty() && !isa<Undefined>(Symtab->find(Entry)))
+      if (findUnderscoreMangle(S))
         return mangle(S);
     }
     return "";
@@ -442,8 +446,7 @@
       {"wWinMain", "wWinMainCRTStartup"},
   };
   for (auto E : Entries) {
-    StringRef Entry = Symtab->findMangle(mangle(E[0]));
-    if (!Entry.empty() && !isa<Undefined>(Symtab->find(Entry)))
+    if (findUnderscoreMangle(E[0]))
       return mangle(E[1]);
   }
   return "";
@@ -452,9 +455,9 @@
 WindowsSubsystem LinkerDriver::inferSubsystem() {
   if (Config->DLL)
     return IMAGE_SUBSYSTEM_WINDOWS_GUI;
-  if (Symtab->findUnderscore("main") || Symtab->findUnderscore("wmain"))
+  if (findUnderscoreMangle("main") || findUnderscoreMangle("wmain"))
     return IMAGE_SUBSYSTEM_WINDOWS_CUI;
-  if (Symtab->findUnderscore("WinMain") || Symtab->findUnderscore("wWinMain"))
+  if (findUnderscoreMangle("WinMain") || findUnderscoreMangle("wWinMain"))
     return IMAGE_SUBSYSTEM_WINDOWS_GUI;
   return IMAGE_SUBSYSTEM_UNKNOWN;
 }
Index: test/COFF/entry-inference3.test
===================================================================
--- test/COFF/entry-inference3.test
+++ test/COFF/entry-inference3.test
@@ -1,4 +1,8 @@
-# RUN: yaml2obj < %s > %t.obj
+# RUN: sed -e s/ENTRYNAME/mainCRTStartup/ %s | yaml2obj > %t.obj
+# RUN: not lld-link /out:%t.exe %t.obj /verbose /nodefaultlib > %t.log 2>&1
+# RUN: FileCheck %s < %t.log
+
+# RUN: sed -e s/ENTRYNAME/?mainCRTStartup@@YAHXZ/ %s | yaml2obj > %t.obj
 # RUN: not lld-link /out:%t.exe %t.obj /verbose /nodefaultlib > %t.log 2>&1
 # RUN: FileCheck %s < %t.log
 
@@ -26,7 +30,7 @@
       NumberOfLinenumbers: 0
       CheckSum:        0
       Number:          0
-  - Name:            mainCRTStartup
+  - Name:            "ENTRYNAME"
     Value:           0
     SectionNumber:   1
     SimpleType:      IMAGE_SYM_TYPE_NULL
Index: test/COFF/entry-inference332.test
===================================================================
--- test/COFF/entry-inference332.test
+++ test/COFF/entry-inference332.test
@@ -0,0 +1,39 @@
+# RUN: sed -e s/ENTRYNAME/_mainCRTStartup/ %s | yaml2obj > %t.obj
+# RUN: not lld-link /out:%t.exe %t.obj /verbose /nodefaultlib > %t.log 2>&1
+# RUN: FileCheck %s < %t.log
+
+# RUN: sed -e s/ENTRYNAME/?mainCRTStartup@@YAHXZ/ %s | yaml2obj > %t.obj
+# RUN: not lld-link /out:%t.exe %t.obj /verbose /nodefaultlib > %t.log 2>&1
+# RUN: FileCheck %s < %t.log
+
+# CHECK: Entry name inferred: _mainCRTStartup
+
+--- !COFF
+header:
+  Machine:         IMAGE_FILE_MACHINE_I386
+  Characteristics: []
+sections:
+  - Name:            .text
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+    Alignment:       4
+    SectionData:     B82A000000C3
+symbols:
+  - Name:            .text
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          6
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        0
+      Number:          0
+  - Name:            "ENTRYNAME"
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+...
Index: test/COFF/subsystem-inference32.test
===================================================================
--- test/COFF/subsystem-inference32.test
+++ test/COFF/subsystem-inference32.test
@@ -0,0 +1,74 @@
+# RUN: sed -e s/ENTRYNAME/_main/ %s | yaml2obj > %t.obj
+# RUN: lld-link /out:%t.exe %t.obj
+# RUN: llvm-readobj -file-headers %t.exe | FileCheck -check-prefix=MAIN %s
+
+# RUN: sed s/ENTRYNAME/_wmain/ %s | yaml2obj > %t.obj
+# RUN: lld-link /out:%t.exe %t.obj
+# RUN: llvm-readobj -file-headers %t.exe | FileCheck -check-prefix=WMAIN %s
+
+# RUN: sed s/ENTRYNAME/_WinMain@16/ %s | yaml2obj > %t.obj
+# RUN: lld-link /out:%t.exe %t.obj
+# RUN: llvm-readobj -file-headers %t.exe | FileCheck -check-prefix=WINMAIN %s
+
+# RUN: sed s/ENTRYNAME/_wWinMain@16/ %s | yaml2obj > %t.obj
+# RUN: lld-link /out:%t.exe %t.obj
+# RUN: llvm-readobj -file-headers %t.exe | FileCheck -check-prefix=WWINMAIN %s
+
+# MAIN:     Subsystem: IMAGE_SUBSYSTEM_WINDOWS_CUI
+# WMAIN:    Subsystem: IMAGE_SUBSYSTEM_WINDOWS_CUI
+# WINMAIN:  Subsystem: IMAGE_SUBSYSTEM_WINDOWS_GUI
+# WWINMAIN: Subsystem: IMAGE_SUBSYSTEM_WINDOWS_GUI
+
+--- !COFF
+header:
+  Machine:         IMAGE_FILE_MACHINE_I386
+  Characteristics: []
+sections:
+  - Name:            .text
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+    Alignment:       4
+    SectionData:     B82A000000C3
+symbols:
+  - Name:            .text
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          6
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        0
+      Number:          0
+  - Name:            ENTRYNAME
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+  - Name:            _mainCRTStartup
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+  - Name:            _wmainCRTStartup
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+  - Name:            _WinMainCRTStartup
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+  - Name:            _wWinMainCRTStartup
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+...