Index: clang/include/clang/Driver/Driver.h
===================================================================
--- clang/include/clang/Driver/Driver.h
+++ clang/include/clang/Driver/Driver.h
@@ -247,6 +247,9 @@
   /// stored in it, and will clean them up when torn down.
   mutable llvm::StringMap<std::unique_ptr<ToolChain>> ToolChains;
 
+  /// Number of parallel jobs.
+  unsigned NumParallelJobs;
+
 private:
   /// TranslateInputArgs - Create a new derived argument list from the input
   /// arguments, after applying the standard argument translations.
@@ -549,6 +552,12 @@
   /// Get the specific kind of LTO being performed.
   LTOKind getLTOMode() const { return LTOMode; }
 
+  /// Get the number of parallel jobs.
+  unsigned getNumberOfParallelJobs() const { return NumParallelJobs; }
+
+  /// Set the number of parallel jobs.
+  void setNumberOfParallelJobs(unsigned N) { NumParallelJobs = N; }
+
 private:
 
   /// Tries to load options from configuration file.
Index: clang/include/clang/Driver/Job.h
===================================================================
--- clang/include/clang/Driver/Job.h
+++ clang/include/clang/Driver/Job.h
@@ -73,6 +73,9 @@
   /// See Command::setEnvironment
   std::vector<const char *> Environment;
 
+  /// Dependent actions
+  llvm::SmallVector<const Action *, 4> DependentActions;
+
   /// When a response file is needed, we try to put most arguments in an
   /// exclusive file, while others remains as regular command line arguments.
   /// This functions fills a vector with the regular command line arguments,
@@ -130,6 +133,10 @@
 
   /// Set whether to print the input filenames when executing.
   void setPrintInputFilenames(bool P) { PrintInputFilenames = P; }
+
+  const llvm::SmallVector<const Action *, 4> &getDependentActions() const {
+    return DependentActions;
+  }
 };
 
 /// Like Command, but with a fallback which is executed in case
Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -401,6 +401,8 @@
 def Ofast : Joined<["-"], "Ofast">, Group<O_Group>, Flags<[CC1Option]>;
 def P : Flag<["-"], "P">, Flags<[CC1Option]>, Group<Preprocessor_Group>,
   HelpText<"Disable linemarker output in -E mode">;
+def parallel_jobs_EQ : Joined<["-"], "parallel-jobs=">, Flags<[DriverOption]>,
+  HelpText<"Number of parallel jobs">;
 def Qy : Flag<["-"], "Qy">, Flags<[CC1Option]>,
   HelpText<"Emit metadata containing compiler name and version">;
 def Qn : Flag<["-"], "Qn">, Flags<[CC1Option]>,
Index: clang/lib/Driver/Compilation.cpp
===================================================================
--- clang/lib/Driver/Compilation.cpp
+++ clang/lib/Driver/Compilation.cpp
@@ -15,6 +15,7 @@
 #include "clang/Driver/Options.h"
 #include "clang/Driver/ToolChain.h"
 #include "clang/Driver/Util.h"
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
@@ -25,8 +26,11 @@
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cassert>
+#include <functional>
+#include <mutex>
 #include <string>
 #include <system_error>
+#include <thread>
 #include <utility>
 
 using namespace clang;
@@ -220,22 +224,134 @@
   return !ActionFailed(&C.getSource(), FailingCommands);
 }
 
+namespace {
+class JobScheduler {
+public:
+  enum JobState { JS_WAIT, JS_RUN, JS_DONE, JS_FAIL };
+  JobScheduler(const JobList &Jobs, size_t NJobs = 1)
+      : Jobs(Jobs), NumJobs(NJobs) {
+#if !LLVM_ENABLE_THREADS
+    NumJobs = 1;
+#endif
+    for (auto &Job : Jobs) {
+      JState[&Job] = JS_WAIT;
+      for (const auto *AI : Job.getDependentActions()) {
+        for (const auto *CI : ActToCmds[AI]) {
+          DependentCmds[&Job].push_back(CI);
+        }
+      }
+      for (const auto *CI : ActToCmds[&Job.getSource()]) {
+        DependentCmds[&Job].push_back(CI);
+      }
+      ActToCmds[&Job.getSource()].push_back(&Job);
+    }
+  }
+  /// \return true if all jobs are done. Otherwise, \p Next contains the
+  /// the next job ready to be executed if it is not null pointer. Otherwise
+  /// all jobs are running or waiting.
+  bool IsDone(const Command *&Next) {
+    std::lock_guard<std::mutex> lock(Mutex);
+    Next = nullptr;
+    unsigned Done = 0;
+    unsigned Running = 0;
+    for (auto &Cmd : Jobs) {
+      switch (JState[&Cmd]) {
+      case JS_RUN:
+        ++Running;
+        break;
+      case JS_DONE:
+      case JS_FAIL:
+        ++Done;
+        break;
+      case JS_WAIT: {
+        bool InputsReady = true;
+        for (const auto *CI : DependentCmds[&Cmd]) {
+          if (JState[CI] == JS_FAIL) {
+            JState[&Cmd] = JS_FAIL;
+            ++Done;
+            InputsReady = false;
+            break;
+          }
+          if (JState[CI] != JS_DONE) {
+            InputsReady = false;
+            break;
+          }
+        }
+        if (!Next && InputsReady) {
+          Next = &Cmd;
+        }
+        break;
+      }
+      }
+    }
+    if (Running >= NumJobs)
+      Next = nullptr;
+    return Done == Jobs.size();
+  }
+
+  void setJobState(const Command *Cmd, JobState JS) {
+    std::lock_guard<std::mutex> lock(Mutex);
+    JState[Cmd] = JS;
+  }
+
+  void launch(std::function<void()> Work) {
+#if LLVM_ENABLE_THREADS
+    if (NumJobs == 1) {
+      Work();
+      return;
+    }
+    std::thread Th(Work);
+    Th.detach();
+#else
+    Work();
+#endif
+  }
+
+private:
+  std::mutex Mutex;
+  const JobList &Jobs;
+  llvm::DenseMap<const Command *, JobState> JState;
+  llvm::DenseMap<const Action *, llvm::SmallVector<const Command *, 4>>
+      ActToCmds;
+  llvm::DenseMap<const Command *, llvm::SmallVector<const Command *, 4>>
+      DependentCmds;
+  size_t NumJobs; // Number of parallel jobs to run
+};
+} // namespace
 void Compilation::ExecuteJobs(const JobList &Jobs,
                               FailingCommandList &FailingCommands) const {
   // According to UNIX standard, driver need to continue compiling all the
   // inputs on the command line even one of them failed.
   // In all but CLMode, execute all the jobs unless the necessary inputs for the
   // job is missing due to previous failures.
-  for (const auto &Job : Jobs) {
-    if (!InputsOk(Job, FailingCommands))
+  JobScheduler JS(Jobs, getDriver().getNumberOfParallelJobs());
+
+  const Command *Next = nullptr;
+  while (!JS.IsDone(Next)) {
+    if (!Next) {
+      std::this_thread::yield();
       continue;
-    const Command *FailingCommand = nullptr;
-    if (int Res = ExecuteCommand(Job, FailingCommand)) {
-      FailingCommands.push_back(std::make_pair(Res, FailingCommand));
+    }
+
+    if (!InputsOk(*Next, FailingCommands)) {
+      JS.setJobState(Next, JobScheduler::JS_FAIL);
       // Bail as soon as one command fails in cl driver mode.
       if (TheDriver.IsCLMode())
         return;
+      continue;
     }
+
+    JS.setJobState(Next, JobScheduler::JS_RUN);
+    auto Work = [&, Next]() {
+      const Command *FailingCommand = nullptr;
+      if (int Res = ExecuteCommand(*Next, FailingCommand)) {
+        JS.setJobState(Next, JobScheduler::JS_FAIL);
+        FailingCommands.push_back(std::make_pair(Res, FailingCommand));
+      } else {
+        JS.setJobState(Next, JobScheduler::JS_DONE);
+      }
+    };
+    JS.launch(Work);
   }
 }
 
Index: clang/lib/Driver/Driver.cpp
===================================================================
--- clang/lib/Driver/Driver.cpp
+++ clang/lib/Driver/Driver.cpp
@@ -38,13 +38,14 @@
 #include "ToolChains/NaCl.h"
 #include "ToolChains/NetBSD.h"
 #include "ToolChains/OpenBSD.h"
-#include "ToolChains/PS4CPU.h"
 #include "ToolChains/PPCLinux.h"
+#include "ToolChains/PS4CPU.h"
 #include "ToolChains/RISCVToolchain.h"
 #include "ToolChains/Solaris.h"
 #include "ToolChains/TCE.h"
 #include "ToolChains/WebAssembly.h"
 #include "ToolChains/XCore.h"
+#include "clang/Basic/OptionUtils.h"
 #include "clang/Basic/Version.h"
 #include "clang/Config/config.h"
 #include "clang/Driver/Action.h"
@@ -55,6 +56,7 @@
 #include "clang/Driver/SanitizerArgs.h"
 #include "clang/Driver/Tool.h"
 #include "clang/Driver/ToolChain.h"
+#include "clang/Driver/Util.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallSet.h"
@@ -130,7 +132,7 @@
       CCLogDiagnostics(false), CCGenDiagnostics(false),
       TargetTriple(TargetTriple), CCCGenericGCCName(""), Saver(Alloc),
       CheckInputsExist(true), GenReproducer(false),
-      SuppressMissingInputWarning(false) {
+      SuppressMissingInputWarning(false), NumParallelJobs(1) {
 
   // Provide a sane fallback if no VFS is specified.
   if (!this->VFS)
@@ -1103,6 +1105,9 @@
       BitcodeEmbed = static_cast<BitcodeEmbedMode>(Model);
   }
 
+  setNumberOfParallelJobs(
+      getLastArgIntValue(Args, options::OPT_parallel_jobs_EQ, 1, Diags));
+
   std::unique_ptr<llvm::opt::InputArgList> UArgs =
       std::make_unique<InputArgList>(std::move(Args));
 
Index: clang/lib/Driver/Job.cpp
===================================================================
--- clang/lib/Driver/Job.cpp
+++ clang/lib/Driver/Job.cpp
@@ -39,9 +39,11 @@
                  ArrayRef<InputInfo> Inputs)
     : Source(Source), Creator(Creator), Executable(Executable),
       Arguments(Arguments) {
-  for (const auto &II : Inputs)
+  for (const auto &II : Inputs) {
     if (II.isFilename())
       InputFilenames.push_back(II.getFilename());
+    DependentActions.push_back(II.getAction());
+  }
 }
 
 /// Check if the compiler flag in question should be skipped when
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -6483,7 +6483,7 @@
   C.addCommand(std::make_unique<Command>(
       JA, *this,
       TCArgs.MakeArgString(getToolChain().GetProgramPath(getShortName())),
-      CmdArgs, None));
+      CmdArgs, Inputs));
 }
 
 void OffloadBundler::ConstructJobMultipleOutputs(
@@ -6549,7 +6549,7 @@
   C.addCommand(std::make_unique<Command>(
       JA, *this,
       TCArgs.MakeArgString(getToolChain().GetProgramPath(getShortName())),
-      CmdArgs, None));
+      CmdArgs, Inputs));
 }
 
 void OffloadWrapper::ConstructJob(Compilation &C, const JobAction &JA,