Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -770,7 +770,7 @@
 def fprofile_arcs : Flag<["-"], "fprofile-arcs">, Group<f_Group>;
 def fprofile_generate : Flag<["-"], "fprofile-generate">, Group<f_Group>;
 def framework : Separate<["-"], "framework">, Flags<[LinkerInput]>;
-def frandom_seed_EQ : Joined<["-"], "frandom-seed=">, Group<clang_ignored_f_Group>;
+def frandom_seed_EQ : Joined<["-"], "frandom-seed=">, Group<f_Group>, Flags<[CC1Option]>;
 def freg_struct_return : Flag<["-"], "freg-struct-return">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Override the default ABI to return small structs in registers">;
 def frtti : Flag<["-"], "frtti">, Group<f_Group>;
Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -3394,6 +3394,13 @@
     }
   }
 
+  // Translate -frandom-seed to seed the LLVM RNG
+  if (Args.hasArg(options::OPT_frandom_seed_EQ)) {
+    StringRef seed = Args.getLastArgValue(options::OPT_frandom_seed_EQ);
+    CmdArgs.push_back("-backend-option");
+    CmdArgs.push_back(Args.MakeArgString("-rng-seed=" + seed));
+  }
+
   if (Arg *A = Args.getLastArg(options::OPT_mrestrict_it,
                                options::OPT_mno_restrict_it)) {
     if (A->getOption().matches(options::OPT_mrestrict_it)) {
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -32,6 +32,7 @@
 #include "llvm/Support/Host.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Process.h"
+#include "llvm/Support/RandomNumberGenerator.h"
 #include "llvm/Support/system_error.h"
 #include <atomic>
 #include <memory>
@@ -1672,6 +1673,16 @@
     Opts.Triple = llvm::sys::getDefaultTargetTriple();
 }
 
+static void SaltRNG(ArgList &Args) {
+  std::vector<std::string> Inputs = Args.getAllArgValues(OPT_INPUT);
+  std::string SaltString;
+  for (std::vector<std::string>::iterator I = Inputs.begin(), E = Inputs.end();
+       I != E; ++I) {
+    SaltString += *I;
+  }
+  llvm::RandomNumberGenerator::SetSalt(SaltString);
+}
+
 bool CompilerInvocation::CreateFromArgs(CompilerInvocation &Res,
                                         const char *const *ArgBegin,
                                         const char *const *ArgEnd,
@@ -1726,6 +1737,8 @@
   ParsePreprocessorArgs(Res.getPreprocessorOpts(), *Args, FileMgr, Diags);
   ParsePreprocessorOutputArgs(Res.getPreprocessorOutputOpts(), *Args,
                               Res.getFrontendOpts().ProgramAction);
+  SaltRNG(*Args);
+
   return Success;
 }