Index: lib/Support/GraphWriter.cpp
===================================================================
--- lib/Support/GraphWriter.cpp
+++ lib/Support/GraphWriter.cpp
@@ -189,32 +189,47 @@
     return ExecGraphViewer(ViewerPath, args, Filename, wait, ErrMsg);
   }
 
-  enum PSViewerKind { PSV_None, PSV_OSXOpen, PSV_XDGOpen, PSV_Ghostview };
-  PSViewerKind PSViewer = PSV_None;
+  enum ViewerKind {
+    PSV_None,
+    PSV_OSXOpen,
+    PSV_XDGOpen,
+    PSV_Ghostview,
+    PDFV_CmdStart
+  };
+  ViewerKind Viewer = PSV_None;
 #ifdef __APPLE__
-  if (!PSViewer && S.TryFindProgram("open", ViewerPath))
-    PSViewer = PSV_OSXOpen;
+  if (!Viewer && S.TryFindProgram("open", ViewerPath))
+    Viewer = PSV_OSXOpen;
+#endif
+  if (!Viewer && S.TryFindProgram("gv", ViewerPath))
+    Viewer = PSV_Ghostview;
+  if (!Viewer && S.TryFindProgram("xdg-open", ViewerPath))
+    Viewer = PSV_XDGOpen;
+#ifdef LLVM_ON_WIN32
+  if (!Viewer && S.TryFindProgram("cmd", ViewerPath)) {
+    Viewer = PDFV_CmdStart;
+  }
 #endif
-  if (!PSViewer && S.TryFindProgram("gv", ViewerPath))
-    PSViewer = PSV_Ghostview;
-  if (!PSViewer && S.TryFindProgram("xdg-open", ViewerPath))
-    PSViewer = PSV_XDGOpen;
 
-  // PostScript graph generator + PostScript viewer
+  // PostScript or PDF graph generator + PostScript/PDF viewer
   std::string GeneratorPath;
-  if (PSViewer &&
+  if (Viewer &&
       (S.TryFindProgram(getProgramName(program), GeneratorPath) ||
        S.TryFindProgram("dot|fdp|neato|twopi|circo", GeneratorPath))) {
-    std::string PSFilename = Filename + ".ps";
+    std::string OutputFilename =
+        Filename + (Viewer == PDFV_CmdStart ? ".pdf" : ".ps");
 
     std::vector<const char *> args;
     args.push_back(GeneratorPath.c_str());
-    args.push_back("-Tps");
+    if (Viewer == PDFV_CmdStart)
+      args.push_back("-Tpdf");
+    else
+      args.push_back("-Tps");
     args.push_back("-Nfontname=Courier");
     args.push_back("-Gsize=7.5,10");
     args.push_back(Filename.c_str());
     args.push_back("-o");
-    args.push_back(PSFilename.c_str());
+    args.push_back(OutputFilename.c_str());
     args.push_back(nullptr);
 
     errs() << "Running '" << GeneratorPath << "' program... ";
@@ -222,20 +237,30 @@
     if (ExecGraphViewer(GeneratorPath, args, Filename, wait, ErrMsg))
       return true;
 
+    std::string StartArg;
+    if (Viewer == PDFV_CmdStart)
+      StartArg =
+          (StringRef("start ") + (wait ? "/WAIT " : "") + OutputFilename).str();
+
     args.clear();
     args.push_back(ViewerPath.c_str());
-    switch (PSViewer) {
+    switch (Viewer) {
     case PSV_OSXOpen:
       args.push_back("-W");
-      args.push_back(PSFilename.c_str());
+      args.push_back(OutputFilename.c_str());
       break;
     case PSV_XDGOpen:
       wait = false;
-      args.push_back(PSFilename.c_str());
+      args.push_back(OutputFilename.c_str());
       break;
     case PSV_Ghostview:
       args.push_back("--spartan");
-      args.push_back(PSFilename.c_str());
+      args.push_back(OutputFilename.c_str());
+      break;
+    case PDFV_CmdStart:
+      args.push_back("/S");
+      args.push_back("/C");
+      args.push_back(StartArg.c_str());
       break;
     case PSV_None:
       llvm_unreachable("Invalid viewer");
@@ -243,7 +268,7 @@
     args.push_back(nullptr);
 
     ErrMsg.clear();
-    return ExecGraphViewer(ViewerPath, args, PSFilename, wait, ErrMsg);
+    return ExecGraphViewer(ViewerPath, args, OutputFilename, wait, ErrMsg);
   }
 
   // dotty