9 files changed, 106 insertions, 2 deletions
diff --git a/clang/docs/ClangCommandLineReference.rst b/clang/docs/ClangCommandLineReference.rst
index 30ac27f95f9..bad91ff830d 100644
--- a/clang/docs/ClangCommandLineReference.rst
+++ b/clang/docs/ClangCommandLineReference.rst
@@ -610,6 +610,10 @@ C++ standard library to use
 
 Generate code for the given target
 
+.. option:: --print-supported-cpus
+
+Print supported cpu models for the given target
+
 .. option:: -time
 
 Time individual commands
diff --git a/clang/docs/CommandGuide/clang.rst b/clang/docs/CommandGuide/clang.rst
index 84e0dddb8e1..1ed11c77ad0 100644
--- a/clang/docs/CommandGuide/clang.rst
+++ b/clang/docs/CommandGuide/clang.rst
@@ -324,6 +324,12 @@ number of cross compilers, or may only support a native target.
   When building for iPhone OS, specify the minimum version supported by your
   application.
 
+.. option:: --print-supported-cpus
+
+  Print out a list of supported processors for the given target (specified 
+  through --target=<architecture> or -arch <architecture>). If no target is 
+  specified, the system default target will be used.
+
 .. option:: -march=<cpu>
 
   Specify that Clang should generate code for a specific processor family
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 65c1721daa8..07d1c220c79 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -2632,6 +2632,10 @@ def : Separate<["--"], "no-system-header-prefix">, Alias<no_system_header_prefix
 def s : Flag<["-"], "s">, Group<Link_Group>;
 def target : Joined<["--"], "target=">, Flags<[DriverOption, CoreOption]>,
   HelpText<"Generate code for the given target">;
+def _print_supported_cpus : Flag<["-", "--"], "print-supported-cpus">,
+  Group<CompileOnly_Group>, Flags<[CC1Option, CoreOption]>,
+  HelpText<"Print supported cpu models for the given target (if target is not specified,"
+           " it will print the supported cpus for the default target)">;
 def gcc_toolchain : Joined<["--"], "gcc-toolchain=">, Flags<[DriverOption]>,
   HelpText<"Use the gcc toolchain at the given directory">;
 def time : Flag<["-"], "time">,
diff --git a/clang/include/clang/Frontend/FrontendOptions.h b/clang/include/clang/Frontend/FrontendOptions.h
index 1bbd0489674..66fbe6ae6ca 100644
--- a/clang/include/clang/Frontend/FrontendOptions.h
+++ b/clang/include/clang/Frontend/FrontendOptions.h
@@ -260,6 +260,9 @@ public:
   /// Show timers for individual actions.
   unsigned ShowTimers : 1;
 
+  /// print the supported cpus for the current target
+  unsigned PrintSupportedCPUs : 1;
+
   /// Output time trace profile.
   unsigned TimeTrace : 1;
 
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 17552b28763..3bda71597e3 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -1671,7 +1671,8 @@ bool Driver::HandleImmediateArgs(const Compilation &C) {
   }
 
   if (C.getArgs().hasArg(options::OPT_v) ||
-      C.getArgs().hasArg(options::OPT__HASH_HASH_HASH)) {
+      C.getArgs().hasArg(options::OPT__HASH_HASH_HASH) ||
+      C.getArgs().hasArg(options::OPT__print_supported_cpus)) {
     PrintVersion(C, llvm::errs());
     SuppressMissingInputWarning = true;
   }
@@ -3375,6 +3376,17 @@ void Driver::BuildActions(Compilation &C, DerivedArgList &Args,
     Args.ClaimAllArgs(options::OPT_cl_compile_Group);
   }
 
+  // If the use specify --print-supported-cpus, clang will only print out
+  // supported cpu names without doing compilation.
+  if (Arg *A = Args.getLastArg(options::OPT__print_supported_cpus)) {
+    Actions.clear();
+    // the compilation now has only two phases: Input and Compile
+    // use the --prints-supported-cpus flag as the dummy input to cc1
+    Action *InputAc = C.MakeAction<InputAction>(*A, types::TY_C);
+    Actions.push_back(
+        C.MakeAction<PrecompileJobAction>(InputAc, types::TY_Nothing));
+  }
+
   // Claim ignored clang-cl options.
   Args.ClaimAllArgs(options::OPT_cl_ignored_Group);
 
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 5596e4b6a3c..7ba08c6acad 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1752,6 +1752,7 @@ static InputKind ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
   Opts.ShowHelp = Args.hasArg(OPT_help);
   Opts.ShowStats = Args.hasArg(OPT_print_stats);
   Opts.ShowTimers = Args.hasArg(OPT_ftime_report);
+  Opts.PrintSupportedCPUs = Args.hasArg(OPT__print_supported_cpus);
   Opts.TimeTrace = Args.hasArg(OPT_ftime_trace);
   Opts.ShowVersion = Args.hasArg(OPT_version);
   Opts.ASTMergeFiles = Args.getAllArgValues(OPT_ast_merge);
diff --git a/clang/test/Driver/print-supported-cpus.c b/clang/test/Driver/print-supported-cpus.c
new file mode 100644
index 00000000000..a6b9a71c627
--- /dev/null
+++ b/clang/test/Driver/print-supported-cpus.c
@@ -0,0 +1,16 @@
+// Test that the --print-supported-cpus flag works
+
+// RUN: %clang --target=x86_64-unknown-linux-gnu \
+// RUN:   --print-supported-cpus 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=CHECK-X86
+// CHECK-X86: Target: x86_64-unknown-linux-gnu
+// CHECK-X86: corei7
+// CHECK-X86: Use -mcpu or -mtune to specify the target's processor.
+
+// RUN: %clang --target=arm-unknown-linux-android \
+// RUN:   --print-supported-cpus 2>&1 \
+// RUN:   | FileCheck %s --check-prefix=CHECK-ARM
+// CHECK-ARM: Target: arm-unknown-linux-android
+// CHECK-ARM: cortex-a73
+// CHECK-ARM: cortex-a75
+// CHECK-ARM: Use -mcpu or -mtune to specify the target's processor.
diff --git a/clang/tools/driver/cc1_main.cpp b/clang/tools/driver/cc1_main.cpp
index 2ed27c22708..01a42489333 100644
--- a/clang/tools/driver/cc1_main.cpp
+++ b/clang/tools/driver/cc1_main.cpp
@@ -13,6 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Basic/Stack.h"
+#include "clang/Basic/TargetOptions.h"
 #include "clang/CodeGen/ObjectFilePCHContainerOperations.h"
 #include "clang/Config/config.h"
 #include "clang/Driver/DriverDiagnostic.h"
@@ -36,10 +37,12 @@
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Signals.h"
+#include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/TargetSelect.h"
 #include "llvm/Support/TimeProfiler.h"
 #include "llvm/Support/Timer.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetMachine.h"
 #include <cstdio>
 
 #ifdef CLANG_HAVE_RLIMITS
@@ -166,6 +169,23 @@ static void ensureSufficientStack() {
 static void ensureSufficientStack() {}
 #endif
 
+/// print supported cpus of the given target
+int PrintSupportedCPUs(std::string TargetStr) {
+  std::string Error;
+  const llvm::Target *TheTarget =
+      llvm::TargetRegistry::lookupTarget(TargetStr, Error);
+  if (!TheTarget) {
+    llvm::errs() << Error;
+    return 1;
+  }
+
+  // the target machine will handle the mcpu printing
+  llvm::TargetOptions Options;
+  std::unique_ptr<llvm::TargetMachine> TheTargetMachine(
+      TheTarget->createTargetMachine(TargetStr, "", "+cpuHelp", Options, None));
+  return 0;
+}
+
 int cc1_main(ArrayRef<const char *> Argv, const char *Argv0, void *MainAddr) {
   ensureSufficientStack();
 
@@ -199,6 +219,11 @@ int cc1_main(ArrayRef<const char *> Argv, const char *Argv0, void *MainAddr) {
   if (Clang->getFrontendOpts().TimeTrace)
     llvm::timeTraceProfilerInitialize();
 
+  // --print-supported-cpus takes priority over the actual compilation
+  if (Clang->getFrontendOpts().PrintSupportedCPUs) {
+    return PrintSupportedCPUs(Clang->getTargetOpts().Triple);
+  }
+
   // Infer the builtin include path if unspecified.
   if (Clang->getHeaderSearchOpts().UseBuiltinIncludes &&
       Clang->getHeaderSearchOpts().ResourceDir.empty())
diff --git a/llvm/lib/MC/MCSubtargetInfo.cpp b/llvm/lib/MC/MCSubtargetInfo.cpp
index 9b73800978c..9b0272cab0b 100644
--- a/llvm/lib/MC/MCSubtargetInfo.cpp
+++ b/llvm/lib/MC/MCSubtargetInfo.cpp
@@ -92,9 +92,16 @@ static size_t getLongestEntryLength(ArrayRef<T> Table) {
   return MaxLen;
 }
 
-/// Display help for feature choices.
+/// Display help for feature and mcpu choices.
 static void Help(ArrayRef<SubtargetSubTypeKV> CPUTable,
                  ArrayRef<SubtargetFeatureKV> FeatTable) {
+  // the static variable ensures that the help information only gets
+  // printed once even though a target machine creates multiple subtargets
+  static bool PrintOnce = false;
+  if (PrintOnce) {
+    return;
+  }
+
   // Determine the length of the longest CPU and Feature entries.
   unsigned MaxCPULen  = getLongestEntryLength(CPUTable);
   unsigned MaxFeatLen = getLongestEntryLength(FeatTable);
@@ -114,6 +121,30 @@ static void Help(ArrayRef<SubtargetSubTypeKV> CPUTable,
 
   errs() << "Use +feature to enable a feature, or -feature to disable it.\n"
             "For example, llc -mcpu=mycpu -mattr=+feature1,-feature2\n";
+
+  PrintOnce = true;
+}
+
+/// Display help for mcpu choices only
+static void cpuHelp(ArrayRef<SubtargetSubTypeKV> CPUTable) {
+  // the static variable ensures that the help information only gets
+  // printed once even though a target machine creates multiple subtargets
+  static bool PrintOnce = false;
+  if (PrintOnce) {
+    return;
+  }
+
+  // Print the CPU table.
+  errs() << "Available CPUs for this target:\n\n";
+  for (auto &CPU : CPUTable)
+    errs() << "\t" << CPU.Key << "\n";
+  errs() << '\n';
+
+  errs() << "Use -mcpu or -mtune to specify the target's processor.\n"
+            "For example, clang --target=aarch64-unknown-linux-gui "
+            "-mcpu=cortex-a35\n";
+
+  PrintOnce = true;
 }
 
 static FeatureBitset getFeatures(StringRef CPU, StringRef FS,
@@ -154,6 +185,8 @@ static FeatureBitset getFeatures(StringRef CPU, StringRef FS,
     // Check for help
     if (Feature == "+help")
       Help(ProcDesc, ProcFeatures);
+    else if (Feature == "+cpuHelp")
+      cpuHelp(ProcDesc);
     else
       ApplyFeatureFlag(Bits, Feature, ProcFeatures);
   }