Index: lib/Lex/Lexer.cpp
===================================================================
--- lib/Lex/Lexer.cpp
+++ lib/Lex/Lexer.cpp
@@ -2668,14 +2668,16 @@
 /// \brief Find the end of a version control conflict marker.
 static const char *FindConflictEnd(const char *CurPtr, const char *BufferEnd,
                                    ConflictMarkerKind CMK) {
-  const char *Terminator = CMK == CMK_Perforce ? "<<<<\n" : ">>>>>>>";
-  size_t TermLen = CMK == CMK_Perforce ? 5 : 7;
+  const char *Terminator = CMK == CMK_Perforce ? "<<<<" : ">>>>>>>";
+  size_t TermLen = CMK == CMK_Perforce ? 4 : 7;
   auto RestOfBuffer = StringRef(CurPtr, BufferEnd - CurPtr).substr(TermLen);
   size_t Pos = RestOfBuffer.find(Terminator);
   while (Pos != StringRef::npos) {
     // Must occur at start of line.
     if (Pos == 0 ||
-        (RestOfBuffer[Pos - 1] != '\r' && RestOfBuffer[Pos - 1] != '\n')) {
+        (RestOfBuffer[Pos - 1] != '\r' && RestOfBuffer[Pos - 1] != '\n') ||
+        (CMK == CMK_Perforce && Pos + 4 < RestOfBuffer.size() &&
+            RestOfBuffer[Pos + 4] != '\r' && RestOfBuffer[Pos + 4] != '\n')) {
       RestOfBuffer = RestOfBuffer.substr(Pos+TermLen);
       Pos = RestOfBuffer.find(Terminator);
       continue;
Index: test/Lexer/conflict-marker.c
===================================================================
--- test/Lexer/conflict-marker.c
+++ test/Lexer/conflict-marker.c
@@ -1,4 +1,5 @@
-// RUN: %clang_cc1 %s -verify -fsyntax-only
+// RUN: unix2dos %s | %clang_cc1 -verify -fsyntax-only
+// RUN: dos2unix %s | %clang_cc1 -verify -fsyntax-only
 
 // Test that we recover gracefully from conflict markers left in input files.
 // PR5238
Index: test/lit.cfg.py
===================================================================
--- test/lit.cfg.py
+++ test/lit.cfg.py
@@ -49,6 +49,12 @@
 
 config.substitutions.append(('%PATH%', config.environment['PATH']))
 
+if platform.system() in ['Windows']:
+    config.substitutions.append(('dos2unix', 'sed -b "s/\r$//"'))
+    config.substitutions.append(('unix2dos', 'sed -b "s/\r*$/\r/"'))
+else:
+    config.substitutions.append(('dos2unix', "sed $'s/\r$//'"))
+    config.substitutions.append(('unix2dos', "sed $'s/\r*$/\r/'"))
 
 # For each occurrence of a clang tool name, replace it with the full path to
 # the build directory holding that tool.  We explicitly specify the directories