diff --git a/clang/include/clang/Basic/DiagnosticDriverKinds.td b/clang/include/clang/Basic/DiagnosticDriverKinds.td
--- a/clang/include/clang/Basic/DiagnosticDriverKinds.td
+++ b/clang/include/clang/Basic/DiagnosticDriverKinds.td
@@ -19,7 +19,7 @@
 def err_drv_unsupported_opt_for_language_mode : Error<
   "unsupported option '%0' for language mode '%1'">;
 def err_drv_unsupported_option_argument : Error<
-  "unsupported argument '%1' to option '-%0'">;
+  "unsupported argument '%1' to option '%0'">;
 def err_drv_unknown_stdin_type : Error<
   "-E or -x required when input is from standard input">;
 def err_drv_unknown_stdin_type_clang_cl : Error<
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -703,7 +703,7 @@
 
   if (LTOMode == LTOK_Unknown) {
     D.Diag(diag::err_drv_unsupported_option_argument)
-        << A->getOption().getName() << A->getValue();
+        << A->getSpelling() << A->getValue();
     return LTOK_None;
   }
   return LTOMode;
@@ -735,7 +735,7 @@
   if (RT == OMPRT_Unknown) {
     if (A)
       Diag(diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << A->getValue();
+          << A->getSpelling() << A->getValue();
     else
       // FIXME: We could use a nicer diagnostic here.
       Diag(diag::err_drv_unsupported_opt) << "-fopenmp";
diff --git a/clang/lib/Driver/SanitizerArgs.cpp b/clang/lib/Driver/SanitizerArgs.cpp
--- a/clang/lib/Driver/SanitizerArgs.cpp
+++ b/clang/lib/Driver/SanitizerArgs.cpp
@@ -249,7 +249,7 @@
         SanitizerSet S;
         S.Mask = InvalidValues;
         D.Diag(diag::err_drv_unsupported_option_argument)
-            << Arg->getOption().getName() << toString(S);
+            << Arg->getSpelling() << toString(S);
       }
       TrappingKinds |= expandSanitizerGroups(Add) & ~TrapRemove;
     } else if (Arg->getOption().matches(options::OPT_fno_sanitize_trap_EQ)) {
@@ -604,7 +604,7 @@
         SetToDiagnose.Mask |= KindsToDiagnose;
         if (DiagnoseErrors)
           D.Diag(diag::err_drv_unsupported_option_argument)
-              << Arg->getOption().getName() << toString(SetToDiagnose);
+              << Arg->getSpelling() << toString(SetToDiagnose);
         DiagnosedUnrecoverableKinds |= KindsToDiagnose;
       }
       RecoverableKinds |= expandSanitizerGroups(Add);
@@ -619,7 +619,7 @@
         SetToDiagnose.Mask |= KindsToDiagnose;
         if (DiagnoseErrors)
           D.Diag(diag::err_drv_unsupported_option_argument)
-              << Arg->getOption().getName() << toString(SetToDiagnose);
+              << Arg->getSpelling() << toString(SetToDiagnose);
         DiagnosedAlwaysRecoverableKinds |= KindsToDiagnose;
       }
       RecoverableKinds &= ~expandSanitizerGroups(Remove);
@@ -951,7 +951,7 @@
       auto parsedAsanDtorKind = AsanDtorKindFromString(Arg->getValue());
       if (parsedAsanDtorKind == llvm::AsanDtorKind::Invalid && DiagnoseErrors) {
         TC.getDriver().Diag(clang::diag::err_drv_unsupported_option_argument)
-            << Arg->getOption().getName() << Arg->getValue();
+            << Arg->getSpelling() << Arg->getValue();
       }
       AsanDtorKind = parsedAsanDtorKind;
     }
@@ -964,7 +964,7 @@
               llvm::AsanDetectStackUseAfterReturnMode::Invalid &&
           DiagnoseErrors) {
         TC.getDriver().Diag(clang::diag::err_drv_unsupported_option_argument)
-            << Arg->getOption().getName() << Arg->getValue();
+            << Arg->getSpelling() << Arg->getValue();
       }
       AsanUseAfterReturn = parsedAsanUseAfterReturn;
     }
@@ -1346,7 +1346,7 @@
       Kinds |= Kind;
     else if (DiagnoseErrors)
       D.Diag(clang::diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << Value;
+          << A->getSpelling() << Value;
   }
   return Kinds;
 }
@@ -1381,7 +1381,7 @@
                 .Default(0);
     if (F == 0 && DiagnoseErrors)
       D.Diag(clang::diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << Value;
+          << A->getSpelling() << Value;
     Features |= F;
   }
   return Features;
@@ -1403,7 +1403,7 @@
                 .Default(0);
     if (F == 0 && DiagnoseErrors)
       D.Diag(clang::diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << Value;
+          << A->getSpelling() << Value;
     Features |= F;
   }
   return Features;
diff --git a/clang/lib/Driver/ToolChains/Arch/AArch64.cpp b/clang/lib/Driver/ToolChains/Arch/AArch64.cpp
--- a/clang/lib/Driver/ToolChains/Arch/AArch64.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/AArch64.cpp
@@ -274,9 +274,9 @@
     // If "-Wa,-march=" is used, 'WaMArch' will contain the argument's value,
     // while 'A' is uninitialized. Only dereference 'A' in the other case.
     if (!WaMArch.empty())
-      Diag << "march=" << WaMArch;
+      Diag << "-march=" << WaMArch;
     else
-      Diag << A->getOption().getName() << A->getValue();
+      Diag << A->getSpelling() << A->getValue();
   }
 
   if (Args.getLastArg(options::OPT_mgeneral_regs_only)) {
@@ -330,7 +330,7 @@
           continue;
         }
         D.Diag(diag::err_drv_unsupported_option_argument)
-            << A->getOption().getName() << Scope;
+            << A->getSpelling() << Scope;
         break;
       }
     }
diff --git a/clang/lib/Driver/ToolChains/Arch/ARM.cpp b/clang/lib/Driver/ToolChains/Arch/ARM.cpp
--- a/clang/lib/Driver/ToolChains/Arch/ARM.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/ARM.cpp
@@ -122,7 +122,7 @@
       (Split.second.size() && !DecodeARMFeatures(D, Split.second, CPUName,
                                                  ArchKind, Features, ArgFPUID)))
     D.Diag(clang::diag::err_drv_unsupported_option_argument)
-        << A->getOption().getName() << A->getValue();
+        << A->getSpelling() << A->getValue();
 }
 
 // Check -mcpu=. Needs ArchName to handle -mcpu=generic.
@@ -139,7 +139,7 @@
       (Split.second.size() &&
        !DecodeARMFeatures(D, Split.second, CPU, ArchKind, Features, ArgFPUID)))
     D.Diag(clang::diag::err_drv_unsupported_option_argument)
-        << A->getOption().getName() << A->getValue();
+        << A->getSpelling() << A->getValue();
 }
 
 bool arm::useAAPCSForMachO(const llvm::Triple &T) {
@@ -879,7 +879,7 @@
           continue;
         }
         D.Diag(diag::err_drv_unsupported_option_argument)
-            << A->getOption().getName() << Scope;
+            << A->getSpelling() << Scope;
         break;
       }
     }
diff --git a/clang/lib/Driver/ToolChains/Arch/Mips.cpp b/clang/lib/Driver/ToolChains/Arch/Mips.cpp
--- a/clang/lib/Driver/ToolChains/Arch/Mips.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/Mips.cpp
@@ -306,7 +306,7 @@
       }
     } else
       D.Diag(diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << Val;
+          << A->getSpelling() << Val;
   }
 
   if (Arg *A = Args.getLastArg(options::OPT_mabs_EQ)) {
@@ -327,7 +327,7 @@
       }
     } else {
       D.Diag(diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << Val;
+          << A->getSpelling() << Val;
     }
   }
 
diff --git a/clang/lib/Driver/ToolChains/Arch/RISCV.cpp b/clang/lib/Driver/ToolChains/Arch/RISCV.cpp
--- a/clang/lib/Driver/ToolChains/Arch/RISCV.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/RISCV.cpp
@@ -73,7 +73,7 @@
       CPU = llvm::sys::getHostCPUName();
     if (!getRISCFeaturesFromMcpu(Triple, CPU, Features))
       D.Diag(clang::diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << CPU;
+          << A->getSpelling() << CPU;
   }
 
   // Handle features corresponding to "-ffixed-X" options
diff --git a/clang/lib/Driver/ToolChains/Arch/X86.cpp b/clang/lib/Driver/ToolChains/Arch/X86.cpp
--- a/clang/lib/Driver/ToolChains/Arch/X86.cpp
+++ b/clang/lib/Driver/ToolChains/Arch/X86.cpp
@@ -255,7 +255,7 @@
       Features.push_back("+harden-sls-ijmp");
     } else if (Scope != "none") {
       D.Diag(diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << Scope;
+          << A->getSpelling() << Scope;
     }
   }
 }
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -958,7 +958,7 @@
       CmdArgs.push_back("-fprofile-update=atomic");
     else if (Val != "single")
       D.Diag(diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << Val;
+          << A->getSpelling() << Val;
   } else if (SanArgs.needsTsanRt()) {
     CmdArgs.push_back("-fprofile-update=atomic");
   }
@@ -1141,7 +1141,7 @@
       }
     } else {
       D.Diag(diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << Value;
+          << A->getSpelling() << Value;
     }
   }
 }
@@ -1673,7 +1673,7 @@
     Scope = A->getValue();
     if (Scope != "none" && Scope != "non-leaf" && Scope != "all")
       D.Diag(diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << Scope;
+          << A->getSpelling() << Scope;
     Key = "a_key";
     IndirectBranches = false;
   } else {
@@ -1681,7 +1681,7 @@
     llvm::ARM::ParsedBranchProtection PBP;
     if (!llvm::ARM::parseBranchProtection(A->getValue(), PBP, DiagMsg))
       D.Diag(diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << DiagMsg;
+          << A->getSpelling() << DiagMsg;
     if (!isAArch64 && PBP.Key == "b_key")
       D.Diag(diag::warn_unsupported_branch_protection)
           << "b-key" << A->getAsString(Args);
@@ -1902,7 +1902,7 @@
     } else if (!Val.equals("scalable"))
       // Handle the unsupported values passed to msve-vector-bits.
       D.Diag(diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << Val;
+          << A->getSpelling() << Val;
   }
 
   AddAAPCSVolatileBitfieldArgs(Args, CmdArgs);
@@ -2059,7 +2059,7 @@
         CmdArgs.push_back(Args.MakeArgString("-mips-compact-branches=" + Val));
       } else
         D.Diag(diag::err_drv_unsupported_option_argument)
-            << A->getOption().getName() << Val;
+            << A->getSpelling() << Val;
     } else
       D.Diag(diag::warn_target_unsupported_compact_branches) << CPUName;
   }
@@ -2294,7 +2294,7 @@
       CmdArgs.push_back(Args.MakeArgString("-inline-asm=" + Value));
     } else {
       D.Diag(diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << Value;
+          << A->getSpelling() << Value;
     }
   } else if (D.IsCLMode()) {
     CmdArgs.push_back("-mllvm");
@@ -2377,7 +2377,7 @@
       if (Mregparm != 4) {
         getToolChain().getDriver().Diag(
             diag::err_drv_unsupported_option_argument)
-            << A->getOption().getName() << Value;
+            << A->getSpelling() << Value;
       }
     }
   }
@@ -2558,7 +2558,7 @@
         ImplicitIt = A->getValue();
         if (!CheckARMImplicitITArg(ImplicitIt))
           D.Diag(diag::err_drv_unsupported_option_argument)
-              << A->getOption().getName() << ImplicitIt;
+              << A->getSpelling() << ImplicitIt;
         continue;
       default:
         break;
@@ -2721,7 +2721,7 @@
         D.PrintVersion(C, llvm::outs());
       } else {
         D.Diag(diag::err_drv_unsupported_option_argument)
-            << A->getOption().getName() << Value;
+            << A->getSpelling() << Value;
       }
     }
   }
@@ -2855,7 +2855,7 @@
         TrappingMath = true;
       } else
         D.Diag(diag::err_drv_unsupported_option_argument)
-            << A->getOption().getName() << Val;
+            << A->getSpelling() << Val;
       break;
       }
     }
@@ -2942,7 +2942,7 @@
         LastSeenFfpContractOption = Val;
       } else
         D.Diag(diag::err_drv_unsupported_option_argument)
-           << A->getOption().getName() << Val;
+            << A->getSpelling() << Val;
       break;
     }
 
@@ -2970,7 +2970,7 @@
         TrappingMath = TrappingMathPresent = true;
       } else
         D.Diag(diag::err_drv_unsupported_option_argument)
-            << A->getOption().getName() << Val;
+            << A->getSpelling() << Val;
       break;
     }
 
@@ -2982,7 +2982,7 @@
         FPEvalMethod = Val;
       else
         D.Diag(diag::err_drv_unsupported_option_argument)
-            << A->getOption().getName() << Val;
+            << A->getSpelling() << Val;
       break;
     }
 
@@ -3436,7 +3436,7 @@
         TrivialAutoVarInit = Val;
       else
         D.Diag(diag::err_drv_unsupported_option_argument)
-            << A->getOption().getName() << Val;
+            << A->getSpelling() << Val;
       break;
     }
     }
@@ -4094,7 +4094,7 @@
     return DwarfFissionKind::Single;
 
   D.Diag(diag::err_drv_unsupported_option_argument)
-      << Arg->getOption().getName() << Arg->getValue();
+      << Arg->getSpelling() << Arg->getValue();
   return DwarfFissionKind::None;
 }
 
@@ -7879,7 +7879,7 @@
       CmdArgs.push_back(Args.MakeArgString("-x86-asm-syntax=" + Value));
     } else {
       getToolChain().getDriver().Diag(diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << Value;
+          << A->getSpelling() << Value;
     }
   }
 }
diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -296,7 +296,7 @@
       CmdArgs.push_back(Args.MakeArgString("--compress-debug-sections=" + V));
     else
       TC.getDriver().Diag(diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << V;
+          << A->getSpelling() << V;
   }
 }
 
diff --git a/clang/lib/Driver/ToolChains/Flang.cpp b/clang/lib/Driver/ToolChains/Flang.cpp
--- a/clang/lib/Driver/ToolChains/Flang.cpp
+++ b/clang/lib/Driver/ToolChains/Flang.cpp
@@ -104,7 +104,7 @@
       // Clang's "fast-honor-pragmas" option is not supported because it is
       // non-standard
       D.Diag(diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << Val;
+          << A->getSpelling() << Val;
   }
 
   for (const Arg *A : Args) {
diff --git a/clang/lib/Driver/ToolChains/Gnu.cpp b/clang/lib/Driver/ToolChains/Gnu.cpp
--- a/clang/lib/Driver/ToolChains/Gnu.cpp
+++ b/clang/lib/Driver/ToolChains/Gnu.cpp
@@ -729,7 +729,7 @@
             Args.MakeArgString("--compress-debug-sections=" + Twine(Value)));
       } else {
         D.Diag(diag::err_drv_unsupported_option_argument)
-            << A->getOption().getName() << Value;
+            << A->getSpelling() << Value;
       }
     }
   }
diff --git a/clang/lib/Driver/ToolChains/Hexagon.cpp b/clang/lib/Driver/ToolChains/Hexagon.cpp
--- a/clang/lib/Driver/ToolChains/Hexagon.cpp
+++ b/clang/lib/Driver/ToolChains/Hexagon.cpp
@@ -40,7 +40,7 @@
     StringRef Val = A->getValue();
     if (!Val.equals_insensitive("64b") && !Val.equals_insensitive("128b"))
       D.Diag(diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << Val;
+          << A->getSpelling() << Val;
   }
 }
 
diff --git a/clang/lib/Driver/ToolChains/MSP430.cpp b/clang/lib/Driver/ToolChains/MSP430.cpp
--- a/clang/lib/Driver/ToolChains/MSP430.cpp
+++ b/clang/lib/Driver/ToolChains/MSP430.cpp
@@ -101,7 +101,7 @@
     Features.push_back("+hwmultf5");
   } else {
     D.Diag(clang::diag::err_drv_unsupported_option_argument)
-        << HWMultArg->getOption().getName() << HWMult;
+        << HWMultArg->getSpelling() << HWMult;
   }
 }
 
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1711,7 +1711,7 @@
     StringRef Value = A->getValue();
     if (Value != "simple" && Value != "mangled")
       Diags.Report(diag::err_drv_unsupported_option_argument)
-          << A->getOption().getName() << A->getValue();
+          << A->getSpelling() << A->getValue();
     Opts.setDebugSimpleTemplateNames(
         StringRef(A->getValue()) == "simple"
             ? codegenoptions::DebugTemplateNamesKind::Simple
diff --git a/clang/test/Driver/mingw-cfguard.c b/clang/test/Driver/mingw-cfguard.c
--- a/clang/test/Driver/mingw-cfguard.c
+++ b/clang/test/Driver/mingw-cfguard.c
@@ -25,4 +25,4 @@
 // GUARD_NOCHECKS-NOT: "--no-guard-cf"
 
 // RUN: %clang --target=x86_64-w64-windows-gnu -### %s -mguard=xxx 2>&1 | FileCheck -check-prefix=GUARD_UNKNOWN %s
-// GUARD_UNKNOWN: error: unsupported argument 'xxx' to option '--mguard='
+// GUARD_UNKNOWN: error: unsupported argument 'xxx' to option '-mguard='
diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -688,7 +688,7 @@
       fpContractMode = LangOptions::FPM_Fast;
     else {
       diags.Report(clang::diag::err_drv_unsupported_option_argument)
-          << a->getOption().getName() << val;
+          << a->getSpelling() << val;
       return false;
     }