[clang][cli] Squash exception model in LangOptions into one member

[jansvoboda11]

Summary

This squashes multiple members in LangOptions into one. This is leveraged in a follow-up patch that implements marshalling of related command-line options.

Depends on D93214.

[dexonsmith]

LGTM.

clang/include/clang/Basic/LangOptions.h

 #include "clang/Basic/CommentOptions.h"
 #include "clang/Basic/LLVM.h"
 #include "clang/Basic/ObjCRuntime.h"
 #include "clang/Basic/Sanitizers.h"
 #include "clang/Basic/Visibility.h"
 #include "llvm/ADT/FloatingPointMode.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Triple.h"
+#include "llvm/MC/MCTargetOptions.h"
 #include <string>
 #include <vector>
 
 namespace clang {
 
 /// Bitfields of LangOptions, split out from LangOptions in order to ensure that
 /// this large collection of bitfields is a trivial class type.
 class LangOptionsBase {
enum FPExceptionModeKind {
     /// Assume that floating-point exceptions are masked.
     FPE_Ignore,
     /// Transformations do not cause new exceptions but may hide some.
     FPE_MayTrap,
     /// Strictly preserve the floating-point exception semantics.
     FPE_Strict
   };
 
+  /// Possible exception handling behavior.
+  using ExceptionHandlingKind = llvm::ExceptionHandling;
+
   enum class LaxVectorConversionKind {
     /// Permit no implicit vector bitcasts.
     None,
     /// Permit vector bitcasts between integer vectors with different numbers
     /// of elements but the same total bit-width.
     Integer,
     /// Permit vector bitcasts between all vectors with the same total
     /// bit-width.
bool isSignReturnAddressWithAKey() const {
     return getSignReturnAddressKey() == SignReturnAddressKeyKind::AKey;
   }
 
   /// Check if leaf functions are also signed.
   bool isSignReturnAddressScopeAll() const {
     return getSignReturnAddressScope() == SignReturnAddressScopeKind::All;
   }
 
-  bool hasSjLjExceptions() const { return SjLjExceptions; }
-  bool hasSEHExceptions() const { return SEHExceptions; }
-  bool hasDWARFExceptions() const { return DWARFExceptions; }
-  bool hasWasmExceptions() const { return WasmExceptions; }
+  bool hasSjLjExceptions() const {
+    return getExceptionHandling() == llvm::ExceptionHandling::SjLj;
+  }
+
+  bool hasSEHExceptions() const {
+    return getExceptionHandling() == llvm::ExceptionHandling::WinEH;
+  }
+
+  bool hasDWARFExceptions() const {
+    return getExceptionHandling() == llvm::ExceptionHandling::DwarfCFI;
+  }
+
+  bool hasWasmExceptions() const {
+    return getExceptionHandling() == llvm::ExceptionHandling::Wasm;
+  }
 };
 
 /// Floating point control options
 class FPOptionsOverride;
 class FPOptions {
 public:
   // We start by defining the layout.
   using storage_type = uint16_t;

clang/include/clang/Basic/LangOptions.def

 ENUM_LANGOPT(LaxVectorConversions, LaxVectorConversionKind, 2,
              LaxVectorConversionKind::All, "lax vector conversions")
 LANGOPT(ConvergentFunctions, 1, 1, "Assume convergent functions")
 LANGOPT(AltiVec           , 1, 0, "AltiVec-style vector initializers")
 LANGOPT(ZVector           , 1, 0, "System z vector extensions")
 LANGOPT(Exceptions        , 1, 0, "exception handling")
 LANGOPT(ObjCExceptions    , 1, 0, "Objective-C exceptions")
 LANGOPT(CXXExceptions     , 1, 0, "C++ exceptions")
-LANGOPT(DWARFExceptions   , 1, 0, "dwarf exception handling")
-LANGOPT(SjLjExceptions    , 1, 0, "setjmp-longjump exception handling")
-LANGOPT(SEHExceptions     , 1, 0, "SEH .xdata exception handling")
-LANGOPT(WasmExceptions    , 1, 0, "WebAssembly exception handling")
+ENUM_LANGOPT(ExceptionHandling, ExceptionHandlingKind, 3,
+             ExceptionHandlingKind::None, "exception handling")
 LANGOPT(IgnoreExceptions  , 1, 0, "ignore exceptions")
 LANGOPT(ExternCNoUnwind   , 1, 0, "Assume extern C functions don't unwind")
 LANGOPT(TraditionalCPP    , 1, 0, "traditional CPP emulation")
 LANGOPT(RTTI              , 1, 1, "run-time type information")
 LANGOPT(RTTIData          , 1, 1, "emit run-time type information data")
 LANGOPT(MSBitfields       , 1, 0, "Microsoft-compatible structure layout")
 LANGOPT(Freestanding, 1, 0, "freestanding implementation")
 LANGOPT(NoBuiltin         , 1, 0, "disable builtin functions")

clang/lib/Frontend/CompilerInvocation.cpp

Arg *A = Args.getLastArg(
       options::OPT_fdwarf_exceptions, options::OPT_fwasm_exceptions);
   if (A) {
     const Option &Opt = A->getOption();
     llvm::Triple T(TargetOpts.Triple);
     if (T.isWindowsMSVCEnvironment())
       Diags.Report(diag::err_fe_invalid_exception_model)
           << Opt.getName() << T.str();
 
-    Opts.SjLjExceptions = Opt.matches(options::OPT_fsjlj_exceptions);
-    Opts.SEHExceptions = Opt.matches(options::OPT_fseh_exceptions);
-    Opts.DWARFExceptions = Opt.matches(options::OPT_fdwarf_exceptions);
-    Opts.WasmExceptions = Opt.matches(options::OPT_fwasm_exceptions);
+    if (Opt.matches(options::OPT_fsjlj_exceptions))
+      Opts.setExceptionHandling(llvm::ExceptionHandling::SjLj);
+    else if (Opt.matches(options::OPT_fseh_exceptions))
+      Opts.setExceptionHandling(llvm::ExceptionHandling::WinEH);
+    else if (Opt.matches(options::OPT_fdwarf_exceptions))
+      Opts.setExceptionHandling(llvm::ExceptionHandling::DwarfCFI);
+    else if (Opt.matches(options::OPT_fwasm_exceptions))
+      Opts.setExceptionHandling(llvm::ExceptionHandling::Wasm);
   }
 
   Opts.ExternCNoUnwind = Args.hasArg(OPT_fexternc_nounwind);
   Opts.TraditionalCPP = Args.hasArg(OPT_traditional_cpp);
 
   Opts.RTTI = Opts.CPlusPlus && !Args.hasArg(OPT_fno_rtti);
   Opts.RTTIData = Opts.RTTI && !Args.hasArg(OPT_fno_rtti_data);
   Opts.Blocks = Args.hasArg(OPT_fblocks) || (Opts.OpenCL