Index: lib/Driver/Driver.cpp
===================================================================
--- lib/Driver/Driver.cpp
+++ lib/Driver/Driver.cpp
@@ -932,30 +932,9 @@
 /// \brief Check whether the file referenced by Value exists in the LIB
 /// environment variable.
 static bool ExistsInLibDir(StringRef Value) {
-  llvm::Optional<std::string> OptPath = llvm::sys::Process::GetEnv("LIB");
-  if (!OptPath.hasValue())
-    return false;
-
-#ifdef LLVM_ON_WIN32
-  const StringRef PathSeparators = ";";
-#else
-  const StringRef PathSeparators = ":";
-#endif
-
-  SmallVector<StringRef, 8> LibDirs;
-  llvm::SplitString(OptPath.getValue(), LibDirs, PathSeparators);
-
-  for (const auto &LibDir : LibDirs) {
-    if (LibDir.empty())
-      continue;
-
-    SmallString<128> FilePath(LibDir);
-    llvm::sys::path::append(FilePath, Value);
-    if (llvm::sys::fs::exists(Twine(FilePath)))
-      return true;
-  }
-
-  return false;
+  llvm::Optional<std::string> FilePath =
+    llvm::sys::FindInEnvPath("LIB", Value);
+  return FilePath.hasValue();
 }
 
 /// \brief Check that the file referenced by Value exists. If it doesn't,
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -7532,30 +7532,13 @@
 // if it's available as cl.exe on the path.
 static std::string FindFallback(const char *FallbackName,
                                 const char *ClangProgramPath) {
-  llvm::Optional<std::string> OptPath = llvm::sys::Process::GetEnv("PATH");
-  if (!OptPath.hasValue())
-    return FallbackName;
+  llvm::Optional<std::string> FilePath =
+    llvm::sys::FindInEnvPath("PATH", FallbackName);
 
-#ifdef LLVM_ON_WIN32
-  const StringRef PathSeparators = ";";
-#else
-  const StringRef PathSeparators = ":";
-#endif
-
-  SmallVector<StringRef, 8> PathSegments;
-  llvm::SplitString(OptPath.getValue(), PathSegments, PathSeparators);
-
-  for (size_t i = 0, e = PathSegments.size(); i != e; ++i) {
-    const StringRef &PathSegment = PathSegments[i];
-    if (PathSegment.empty())
-      continue;
-
-    SmallString<128> FilePath(PathSegment);
-    llvm::sys::path::append(FilePath, FallbackName);
-    if (llvm::sys::fs::can_execute(Twine(FilePath)) &&
-        !llvm::sys::fs::equivalent(Twine(FilePath), ClangProgramPath))
-      return FilePath.str();
-  }
+  if (FilePath.hasValue() &&
+      llvm::sys::fs::can_execute(Twine(FilePath.getValue())) &&
+      !llvm::sys::fs::equivalent(Twine(FilePath.getValue()), ClangProgramPath))
+    return FilePath.getValue();
 
   return FallbackName;
 }