Driver: Avoid a duplicate path separator and clean up code

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@206933 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/WindowsToolChain.cpp b/lib/Driver/WindowsToolChain.cpp
index a32a7bf..cd6d7e1 100644
--- a/lib/Driver/WindowsToolChain.cpp
+++ b/lib/Driver/WindowsToolChain.cpp
@@ -297,17 +297,12 @@
   // Honor %INCLUDE%. It should know essential search paths with vcvarsall.bat.
   if (const char *cl_include_dir = getenv("INCLUDE")) {
     SmallVector<StringRef, 8> Dirs;
-    StringRef(cl_include_dir).split(Dirs, ";");
-    int n = 0;
-    for (SmallVectorImpl<StringRef>::iterator I = Dirs.begin(), E = Dirs.end();
-         I != E; ++I) {
-      StringRef d = *I;
-      if (d.size() == 0)
-        continue;
-      ++n;
-      addSystemInclude(DriverArgs, CC1Args, d);
-    }
-    if (n) return;
+    StringRef(cl_include_dir)
+        .split(Dirs, ";", /*MaxSplit=*/-1, /*KeepEmpty=*/false);
+    for (StringRef Dir : Dirs)
+      addSystemInclude(DriverArgs, CC1Args, Dir);
+    if (!Dirs.empty())
+      return;
   }
 
   std::string VSDir;
@@ -316,12 +311,19 @@
   // When built with access to the proper Windows APIs, try to actually find
   // the correct include paths first.
   if (getVisualStudioDir(VSDir)) {
-    addSystemInclude(DriverArgs, CC1Args, VSDir + "\\VC\\include");
-    if (getWindowsSDKDir(WindowsSDKDir))
-      addSystemInclude(DriverArgs, CC1Args, WindowsSDKDir + "\\include");
-    else
-      addSystemInclude(DriverArgs, CC1Args,
-                       VSDir + "\\VC\\PlatformSDK\\Include");
+    SmallString<128> P;
+    P = VSDir;
+    llvm::sys::path::append(P, "VC\\include");
+    addSystemInclude(DriverArgs, CC1Args, P.str());
+    if (getWindowsSDKDir(WindowsSDKDir)) {
+      P = WindowsSDKDir;
+      llvm::sys::path::append(P, "include");
+      addSystemInclude(DriverArgs, CC1Args, P.str());
+    } else {
+      P = VSDir;
+      llvm::sys::path::append(P, "VC\\PlatformSDK\\Include");
+      addSystemInclude(DriverArgs, CC1Args, P.str());
+    }
     return;
   }