Index: lib/Transforms/Instrumentation/GCOVProfiling.cpp
===================================================================
--- lib/Transforms/Instrumentation/GCOVProfiling.cpp
+++ lib/Transforms/Instrumentation/GCOVProfiling.cpp
@@ -118,7 +118,8 @@
   Function *insertFlush(ArrayRef<std::pair<GlobalVariable *, MDNode *>>);
   void insertIndirectCounterIncrement();
 
-  std::string mangleName(const DICompileUnit *CU, const char *NewStem);
+  enum GCovFileType { GCNO, GCDA };
+  std::string mangleName(const DICompileUnit *CU, GCovFileType NewStem);
 
   GCOVOptions Options;
 
@@ -418,24 +419,37 @@
 }
 
 std::string GCOVProfiler::mangleName(const DICompileUnit *CU,
-                                     const char *NewStem) {
+                                     GCovFileType NewStem) {
   if (NamedMDNode *GCov = M->getNamedMetadata("llvm.gcov")) {
     for (int i = 0, e = GCov->getNumOperands(); i != e; ++i) {
       MDNode *N = GCov->getOperand(i);
+      if (N->getNumOperands() == 3) {
+        // These nodes have no mangling to apply, it's stored mangled in the
+        // bitcode.
+        MDString *NotesFile = dyn_cast<MDString>(N->getOperand(0));
+        MDString *DataFile = dyn_cast<MDString>(N->getOperand(1));
+        MDNode *CompileUnit = dyn_cast<MDNode>(N->getOperand(2));
+        if (!NotesFile || !DataFile || !CompileUnit) continue;
+        if (CompileUnit == CU)
+          return NewStem == GCNO ? NotesFile->getString()
+                                 : DataFile->getString();
+      }
       if (N->getNumOperands() != 2) continue;
       MDString *GCovFile = dyn_cast<MDString>(N->getOperand(0));
       MDNode *CompileUnit = dyn_cast<MDNode>(N->getOperand(1));
       if (!GCovFile || !CompileUnit) continue;
       if (CompileUnit == CU) {
-        SmallString<128> Filename = GCovFile->getString();
-        sys::path::replace_extension(Filename, NewStem);
+        SmallString<128> Filename;
+        Filename = GCovFile->getString();
+        sys::path::replace_extension(Filename,
+                                     NewStem == GCNO ? "gcno" : "gcda");
         return Filename.str();
       }
     }
   }
 
   SmallString<128> Filename = CU->getFilename();
-  sys::path::replace_extension(Filename, NewStem);
+  sys::path::replace_extension(Filename, NewStem == GCNO ? "gcno" : "gcda");
   StringRef FName = sys::path::filename(Filename);
   SmallString<128> CurPath;
   if (sys::fs::current_path(CurPath)) return FName;
@@ -501,7 +515,7 @@
       continue;
 
     std::error_code EC;
-    raw_fd_ostream out(mangleName(CU, "gcno"), EC, sys::fs::F_None);
+    raw_fd_ostream out(mangleName(CU, GCNO), EC, sys::fs::F_None);
     std::string EdgeDestinations;
 
     unsigned FunctionIdent = 0;
@@ -849,7 +863,7 @@
       if (CU->getDWOId())
         continue;
 
-      std::string FilenameGcda = mangleName(CU, "gcda");
+      std::string FilenameGcda = mangleName(CU, GCDA);
       uint32_t CfgChecksum = FileChecksums.empty() ? 0 : FileChecksums[i];
       Builder.CreateCall(StartFile,
                          {Builder.CreateGlobalStringPtr(FilenameGcda),
Index: test/Transforms/GCOVProfiling/three-element-mdnode.ll
===================================================================
--- test/Transforms/GCOVProfiling/three-element-mdnode.ll
+++ test/Transforms/GCOVProfiling/three-element-mdnode.ll
@@ -0,0 +1,27 @@
+; RUN: echo '!9 = !{!"%T/aaa.gcno", !"%T/bbb.gcda", !0}' > %t1
+; RUN: cat %s %t1 > %t2
+; RUN: opt -insert-gcov-profiling -S -o %t3 < %t2
+; RUN: grep _Z3foov %T/aaa.gcno
+; RUN: grep bbb.gcda %t3
+; RUN: rm %T/aaa.gcno
+
+define void @_Z3foov() !dbg !5 {
+entry:
+  ret void, !dbg !8
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!10}
+!llvm.gcov = !{!9}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.3 (trunk 177323)", isOptimized: false, emissionKind: FullDebug, file: !2, enums: !3, retainedTypes: !3, globals: !3, imports:  !3)
+!1 = !DIFile(filename: "hello.cc", directory: "/home/nlewycky")
+!2 = !DIFile(filename: "hello.cc", directory: "/home/nlewycky")
+!3 = !{}
+!5 = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov", line: 1, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 1, file: !1, scope: !1, type: !6, variables: !3)
+!6 = !DISubroutineType(types: !7)
+!7 = !{null}
+!8 = !DILocation(line: 1, scope: !5)
+
+
+!10 = !{i32 1, !"Debug Info Version", i32 3}