diff --git a/clang/test/Driver/clang-offload-bundler.c b/clang/test/Driver/clang-offload-bundler.c
index 15092dd..5411a30 100644
--- a/clang/test/Driver/clang-offload-bundler.c
+++ b/clang/test/Driver/clang-offload-bundler.c
@@ -74,10 +74,10 @@
 // CK-ERR6: error: invalid file type specified.
 
 // RUN: not clang-offload-bundler 2>&1 | FileCheck %s --check-prefix CK-ERR7
-// CK-ERR7-DAG: clang-offload-bundler: for the -type option: must be specified at least once!
-// CK-ERR7-DAG: clang-offload-bundler: for the -inputs option: must be specified at least once!
-// CK-ERR7-DAG: clang-offload-bundler: for the -outputs option: must be specified at least once!
-// CK-ERR7-DAG: clang-offload-bundler: for the -targets option: must be specified at least once!
+// CK-ERR7-DAG: clang-offload-bundler: for the --type option: must be specified at least once!
+// CK-ERR7-DAG: clang-offload-bundler: for the --inputs option: must be specified at least once!
+// CK-ERR7-DAG: clang-offload-bundler: for the --outputs option: must be specified at least once!
+// CK-ERR7-DAG: clang-offload-bundler: for the --targets option: must be specified at least once!
 
 // RUN: not clang-offload-bundler -type=i -targets=hxst-powerpcxxle-ibm-linux-gnu,openxp-pxxerpc64le-ibm-linux-gnu,xpenmp-x86_xx-pc-linux-gnu -inputs=%t.i,%t.tgt1,%t.tgt2 -outputs=%t.bundle.i 2>&1 | FileCheck %s --check-prefix CK-ERR8
 // CK-ERR8: error: invalid target 'hxst-powerpcxxle-ibm-linux-gnu', unknown offloading kind 'hxst', unknown target triple 'powerpcxxle-ibm-linux-gnu'.
diff --git a/llvm/lib/Support/CommandLine.cpp b/llvm/lib/Support/CommandLine.cpp
index 18492e2..1ca31b6 100644
--- a/llvm/lib/Support/CommandLine.cpp
+++ b/llvm/lib/Support/CommandLine.cpp
@@ -88,8 +88,37 @@
 
 //===----------------------------------------------------------------------===//
 
+static StringRef ArgPrefix = "  -";
+static StringRef ArgPrefixLong = "  --";
+static StringRef ArgHelpPrefix = " - ";
+
+static size_t argPlusPrefixesSize(StringRef ArgName) {
+  size_t Len = ArgName.size();
+  if (Len == 1)
+    return Len + ArgPrefix.size() + ArgHelpPrefix.size();
+  return Len + ArgPrefixLong.size() + ArgHelpPrefix.size();
+}
+
+static StringRef argPrefix(StringRef ArgName) {
+  if (ArgName.size() == 1)
+    return ArgPrefix;
+  return ArgPrefixLong;
+}
+
 namespace {
 
+class PrintArg {
+  StringRef ArgName;
+public:
+  PrintArg(StringRef ArgName) : ArgName(ArgName) {}
+  friend raw_ostream &operator<<(raw_ostream &OS, const PrintArg&);
+};
+
+raw_ostream &operator<<(raw_ostream &OS, const PrintArg& Arg) {
+  OS << argPrefix(Arg.ArgName) << Arg.ArgName;
+  return OS;
+}
+
 class CommandLineParser {
 public:
   // Globals for name and overview of program.  Program name is not a string to
@@ -1339,12 +1368,12 @@
     if (!Handler) {
       if (SinkOpts.empty()) {
         *Errs << ProgramName << ": Unknown command line argument '" << argv[i]
-              << "'.  Try: '" << argv[0] << " -help'\n";
+              << "'.  Try: '" << argv[0] << " --help'\n";
 
         if (NearestHandler) {
           // If we know a near match, report it as well.
-          *Errs << ProgramName << ": Did you mean '-" << NearestHandlerString
-                 << "'?\n";
+          *Errs << ProgramName << ": Did you mean '"
+                << PrintArg(NearestHandlerString) << "'?\n";
         }
 
         ErrorParsing = true;
@@ -1378,14 +1407,14 @@
              << ": Not enough positional command line arguments specified!\n"
              << "Must specify at least " << NumPositionalRequired
              << " positional argument" << (NumPositionalRequired > 1 ? "s" : "")
-             << ": See: " << argv[0] << " -help\n";
+             << ": See: " << argv[0] << " --help\n";
 
     ErrorParsing = true;
   } else if (!HasUnlimitedPositionals &&
              PositionalVals.size() > PositionalOpts.size()) {
     *Errs << ProgramName << ": Too many positional arguments specified!\n"
           << "Can specify at most " << PositionalOpts.size()
-          << " positional arguments: See: " << argv[0] << " -help\n";
+          << " positional arguments: See: " << argv[0] << " --help\n";
     ErrorParsing = true;
 
   } else if (!ConsumeAfterOpt) {
@@ -1498,7 +1527,7 @@
   if (ArgName.empty())
     Errs << HelpStr; // Be nice for positional arguments
   else
-    Errs << GlobalParser->ProgramName << ": for the -" << ArgName;
+    Errs << GlobalParser->ProgramName << ": for the " << PrintArg(ArgName);
 
   Errs << " option: " << Message << "\n";
   return true;
@@ -1536,16 +1565,14 @@
   return O.ValueStr;
 }
 
-static StringRef ArgPrefix = "  -";
-static StringRef ArgHelpPrefix = " - ";
-static size_t ArgPrefixesSize = ArgPrefix.size() + ArgHelpPrefix.size();
-
 //===----------------------------------------------------------------------===//
 // cl::alias class implementation
 //
 
 // Return the width of the option tag for printing...
-size_t alias::getOptionWidth() const { return ArgStr.size() + ArgPrefixesSize; }
+size_t alias::getOptionWidth() const {
+  return argPlusPrefixesSize(ArgStr);
+}
 
 void Option::printHelpStr(StringRef HelpStr, size_t Indent,
                           size_t FirstLineIndentedBy) {
@@ -1561,8 +1588,8 @@
 
 // Print out the option for the alias.
 void alias::printOptionInfo(size_t GlobalWidth) const {
-  outs() << ArgPrefix << ArgStr;
-  printHelpStr(HelpStr, GlobalWidth, ArgStr.size() + ArgPrefixesSize);
+  outs() << PrintArg(ArgStr);
+  printHelpStr(HelpStr, GlobalWidth, argPlusPrefixesSize(ArgStr));
 }
 
 //===----------------------------------------------------------------------===//
@@ -1574,7 +1601,7 @@
 
 // Return the width of the option tag for printing...
 size_t basic_parser_impl::getOptionWidth(const Option &O) const {
-  size_t Len = O.ArgStr.size();
+  size_t Len = argPlusPrefixesSize(O.ArgStr);
   auto ValName = getValueName();
   if (!ValName.empty()) {
     size_t FormattingLen = 3;
@@ -1583,7 +1610,7 @@
     Len += getValueStr(O, ValName).size() + FormattingLen;
   }
 
-  return Len + ArgPrefixesSize;
+  return Len;
 }
 
 // printOptionInfo - Print out information about this option.  The
@@ -1591,7 +1618,7 @@
 //
 void basic_parser_impl::printOptionInfo(const Option &O,
                                         size_t GlobalWidth) const {
-  outs() << ArgPrefix << O.ArgStr;
+  outs() << PrintArg(O.ArgStr);
 
   auto ValName = getValueName();
   if (!ValName.empty()) {
@@ -1607,7 +1634,7 @@
 
 void basic_parser_impl::printOptionName(const Option &O,
                                         size_t GlobalWidth) const {
-  outs() << ArgPrefix << O.ArgStr;
+  outs() << PrintArg(O.ArgStr);
   outs().indent(GlobalWidth - O.ArgStr.size());
 }
 
@@ -1739,7 +1766,8 @@
 // Return the width of the option tag for printing...
 size_t generic_parser_base::getOptionWidth(const Option &O) const {
   if (O.hasArgStr()) {
-    size_t Size = O.ArgStr.size() + ArgPrefixesSize + EqValue.size();
+    size_t Size =
+        argPlusPrefixesSize(O.ArgStr) + EqValue.size();
     for (unsigned i = 0, e = getNumOptions(); i != e; ++i) {
       StringRef Name = getOption(i);
       if (!shouldPrintOption(Name, getDescription(i), O))
@@ -1767,17 +1795,18 @@
     if (O.getValueExpectedFlag() == ValueOptional) {
       for (unsigned i = 0, e = getNumOptions(); i != e; ++i) {
         if (getOption(i).empty()) {
-          outs() << ArgPrefix << O.ArgStr;
+          outs() << PrintArg(O.ArgStr);
           Option::printHelpStr(O.HelpStr, GlobalWidth,
-                               O.ArgStr.size() + ArgPrefixesSize);
+                               argPlusPrefixesSize(O.ArgStr));
           break;
         }
       }
     }
 
-    outs() << ArgPrefix << O.ArgStr << EqValue;
+    outs() << PrintArg(O.ArgStr) << EqValue;
     Option::printHelpStr(O.HelpStr, GlobalWidth,
-                         O.ArgStr.size() + EqValue.size() + ArgPrefixesSize);
+                         EqValue.size() +
+                             argPlusPrefixesSize(O.ArgStr));
     for (unsigned i = 0, e = getNumOptions(); i != e; ++i) {
       StringRef OptionName = getOption(i);
       StringRef Description = getDescription(i);
@@ -1799,8 +1828,8 @@
     if (!O.HelpStr.empty())
       outs() << "  " << O.HelpStr << '\n';
     for (unsigned i = 0, e = getNumOptions(); i != e; ++i) {
-      auto Option = getOption(i);
-      outs() << "    -" << Option;
+      StringRef Option = getOption(i);
+      outs() << "    " << PrintArg(Option);
       Option::printHelpStr(getDescription(i), GlobalWidth, Option.size() + 8);
     }
   }
@@ -1814,7 +1843,7 @@
 void generic_parser_base::printGenericOptionDiff(
     const Option &O, const GenericOptionValue &Value,
     const GenericOptionValue &Default, size_t GlobalWidth) const {
-  outs() << "  -" << O.ArgStr;
+  outs() << "  " << PrintArg(O.ArgStr);
   outs().indent(GlobalWidth - O.ArgStr.size());
 
   unsigned NumOpts = getNumOptions();
@@ -2034,7 +2063,7 @@
       printSubCommands(Subs, MaxSubLen);
       outs() << "\n";
       outs() << "  Type \"" << GlobalParser->ProgramName
-             << " <subcommand> -help\" to get more help on a specific "
+             << " <subcommand> --help\" to get more help on a specific "
                 "subcommand";
     }
 
@@ -2111,7 +2140,7 @@
              Category = SortedCategories.begin(),
              E = SortedCategories.end();
          Category != E; ++Category) {
-      // Hide empty categories for -help, but show for -help-hidden.
+      // Hide empty categories for --help, but show for --help-hidden.
       const auto &CategoryOptions = CategorizedOptions[*Category];
       bool IsEmptyCategory = CategoryOptions.empty();
       if (!ShowHidden && IsEmptyCategory)
@@ -2127,7 +2156,7 @@
       else
         outs() << "\n";
 
-      // When using -help-hidden explicitly state if the category has no
+      // When using --help-hidden explicitly state if the category has no
       // options associated with it.
       if (IsEmptyCategory) {
         outs() << "  This option category has no options.\n";
@@ -2177,11 +2206,11 @@
 static cl::OptionCategory GenericCategory("Generic Options");
 
 // Define uncategorized help printers.
-// -help-list is hidden by default because if Option categories are being used
-// then -help behaves the same as -help-list.
+// --help-list is hidden by default because if Option categories are being used
+// then --help behaves the same as --help-list.
 static cl::opt<HelpPrinter, true, parser<bool>> HLOp(
     "help-list",
-    cl::desc("Display list of available options (-help-list-hidden for more)"),
+    cl::desc("Display list of available options (--help-list-hidden for more)"),
     cl::location(UncategorizedNormalPrinter), cl::Hidden, cl::ValueDisallowed,
     cl::cat(GenericCategory), cl::sub(*AllSubCommands));
 
@@ -2195,11 +2224,11 @@
 // behaviour at runtime depending on whether one or more Option categories have
 // been declared.
 static cl::opt<HelpPrinterWrapper, true, parser<bool>>
-    HOp("help", cl::desc("Display available options (-help-hidden for more)"),
+    HOp("help", cl::desc("Display available options (--help-hidden for more)"),
         cl::location(WrappedNormalPrinter), cl::ValueDisallowed,
         cl::cat(GenericCategory), cl::sub(*AllSubCommands));
 
-static cl::alias HOpA("h", cl::desc("Alias for -help"), cl::aliasopt(HOp),
+static cl::alias HOpA("h", cl::desc("Alias for --help"), cl::aliasopt(HOp),
                       cl::DefaultOption);
 
 static cl::opt<HelpPrinterWrapper, true, parser<bool>>
@@ -2226,7 +2255,7 @@
   // registered then it is useful to show the categorized help instead of
   // uncategorized help.
   if (GlobalParser->RegisteredOptionCategories.size() > 1) {
-    // unhide -help-list option so user can have uncategorized output if they
+    // unhide --help-list option so user can have uncategorized output if they
     // want it.
     HLOp.setHiddenFlag(NotHidden);
 
diff --git a/llvm/test/FileCheck/dump-input-enable.txt b/llvm/test/FileCheck/dump-input-enable.txt
index 45592dd..8c8a807 100644
--- a/llvm/test/FileCheck/dump-input-enable.txt
+++ b/llvm/test/FileCheck/dump-input-enable.txt
@@ -26,7 +26,7 @@
 ; RUN: not FileCheck -dump-input=foobar 2>&1 \
 ; RUN: | FileCheck %s -match-full-lines -check-prefix=BADVAL
 
-BADVAL: {{F|f}}ile{{C|c}}heck{{.*}}: for the -dump-input option: Cannot find option named 'foobar'!
+BADVAL: {{F|f}}ile{{C|c}}heck{{.*}}: for the --dump-input option: Cannot find option named 'foobar'!
 
 ;--------------------------------------------------
 ; Check -dump-input=help.
diff --git a/llvm/test/Support/check-default-options.txt b/llvm/test/Support/check-default-options.txt
index a8870ba..6f2bff9 100644
--- a/llvm/test/Support/check-default-options.txt
+++ b/llvm/test/Support/check-default-options.txt
@@ -8,11 +8,11 @@
 
 # CHECK-OBJDUMP: -h  - Alias for --section-headers
 # CHECK-READOBJ: -h  - Alias for --file-headers
-# CHECK-TBLGEN:  -h  - Alias for -help
-# CHECK-OPT-RPT: -h  - Alias for -help
+# CHECK-TBLGEN:  -h  - Alias for --help
+# CHECK-OPT-RPT: -h  - Alias for --help
 # CHECK-DWARF:   -h  - Alias for -help
 
 # llvm-dwarfdump declares `-h` option and prints special help in that case,
 # which is weird, but makes for a good test, i.e., shows the default `-h`
 # wasn't used.
-# CHECK-DWARF-H-NOT: -help-list  - Display list of available options (-help-list-hidden for more)
+# CHECK-DWARF-H-NOT: --help-list  - Display list of available options (--help-list-hidden for more)
diff --git a/llvm/unittests/Support/CommandLineTest.cpp b/llvm/unittests/Support/CommandLineTest.cpp
index 5ce6541..e528f51 100644
--- a/llvm/unittests/Support/CommandLineTest.cpp
+++ b/llvm/unittests/Support/CommandLineTest.cpp
@@ -1042,7 +1042,7 @@
 
       StackOption<OptionValue> TestOption(Opt, cl::desc(HelpText),
                                           OptionAttributes...);
-      printOptionInfo(TestOption, 25);
+      printOptionInfo(TestOption, 26);
       outs().flush();
     }
     auto Buffer = MemoryBuffer::getFile(File.FilePath);
@@ -1069,8 +1069,8 @@
               cl::values(clEnumValN(OptionValue::Val, "v1", "desc1")));
 
   // clang-format off
-  EXPECT_EQ(Output, ("  -" + Opt + "=<value> - " + HelpText + "\n"
-                     "    =v1                -   desc1\n")
+  EXPECT_EQ(Output, ("  --" + Opt + "=<value> - " + HelpText + "\n"
+                     "    =v1                 -   desc1\n")
                         .str());
   // clang-format on
 }
@@ -1082,9 +1082,9 @@
 
   // clang-format off
   EXPECT_EQ(Output,
-            ("  -" + Opt + "         - " + HelpText + "\n"
-             "  -" + Opt + "=<value> - " + HelpText + "\n"
-             "    =v1                -   desc1\n")
+            ("  --" + Opt + "         - " + HelpText + "\n"
+             "  --" + Opt + "=<value> - " + HelpText + "\n"
+             "    =v1                 -   desc1\n")
                 .str());
   // clang-format on
 }
@@ -1095,10 +1095,10 @@
                                     clEnumValN(OptionValue::Val, "", "desc2")));
 
   // clang-format off
-  EXPECT_EQ(Output, ("  -" + Opt + "         - " + HelpText + "\n"
-                     "  -" + Opt + "=<value> - " + HelpText + "\n"
-                     "    =v1                -   desc1\n"
-                     "    =<empty>           -   desc2\n")
+  EXPECT_EQ(Output, ("  --" + Opt + "         - " + HelpText + "\n"
+                     "  --" + Opt + "=<value> - " + HelpText + "\n"
+                     "    =v1                 -   desc1\n"
+                     "    =<empty>            -   desc2\n")
                         .str());
   // clang-format on
 }
@@ -1109,8 +1109,8 @@
                                     clEnumValN(OptionValue::Val, "", "")));
 
   // clang-format off
-  EXPECT_EQ(Output, ("  -" + Opt + "=<value> - " + HelpText + "\n"
-                     "    =v1                -   desc1\n"
+  EXPECT_EQ(Output, ("  --" + Opt + "=<value> - " + HelpText + "\n"
+                     "    =v1                 -   desc1\n"
                      "    =<empty>\n")
                         .str());
   // clang-format on
@@ -1122,7 +1122,7 @@
 
   // clang-format off
   EXPECT_EQ(Output,
-            ("  -" + Opt + "=<value> - " + HelpText + "\n"
+            ("  --" + Opt + "=<value> - " + HelpText + "\n"
              "    =v1\n").str());
   // clang-format on
 }
@@ -1147,7 +1147,7 @@
 
 TEST_F(GetOptionWidthTest, GetOptionWidthArgNameLonger) {
   StringRef ArgName("a-long-argument-name");
-  size_t ExpectedStrSize = ("  -" + ArgName + "=<value> - ").str().size();
+  size_t ExpectedStrSize = ("  --" + ArgName + "=<value> - ").str().size();
   EXPECT_EQ(
       runTest(ArgName, cl::values(clEnumValN(OptionValue::Val, "v", "help"))),
       ExpectedStrSize);