[win][x64] Unwind v2 3/n: Add support for emitting unwind v2 information (equivalent to MSVC /d2epilogunwind)

clang/include/clang/Basic/CodeGenOptions.def

@@ -483,6 +483,9 @@ CODEGENOPT(StaticClosure, 1, 0)
 /// Assume that UAVs/SRVs may alias
 CODEGENOPT(ResMayAlias, 1, 0)
 
+/// Enables unwind v2 (epilog) information for x64 Windows.
+CODEGENOPT(WinX64EHUnwindV2, 1, 0)
+
 /// FIXME: Make DebugOptions its own top-level .def file.
 #include "DebugOptions.def"
 

clang/include/clang/Driver/Options.td

@@ -2167,6 +2167,11 @@ defm assume_nothrow_exception_dtor: BoolFOption<"assume-nothrow-exception-dtor",
   LangOpts<"AssumeNothrowExceptionDtor">, DefaultFalse,
   PosFlag<SetTrue, [], [ClangOption, CC1Option], "Assume that exception objects' destructors are non-throwing">,
   NegFlag<SetFalse>>;
+defm winx64_eh_unwindv2 : BoolFOption<"winx64-eh-unwindv2",
+  CodeGenOpts<"WinX64EHUnwindV2">, DefaultFalse,
+  PosFlag<SetTrue, [], [ClangOption, CC1Option], "Enable">,
+  NegFlag<SetFalse, [], [ClangOption], "Disable">,
+  BothFlags<[], [ClangOption], " unwind v2 (epilog) information for x64 Windows">>;
 def fexcess_precision_EQ : Joined<["-"], "fexcess-precision=">, Group<f_Group>,
   Visibility<[ClangOption, CLOption]>,
   HelpText<"Allows control over excess precision on targets where native "
@@ -8935,6 +8940,8 @@ def _SLASH_M_Group : OptionGroup<"</M group>">, Group<cl_compile_Group>;
 def _SLASH_volatile_Group : OptionGroup<"</volatile group>">,
   Group<cl_compile_Group>;
 
+def _SLASH_d2epilogunwind : CLFlag<"d2epilogunwind">,
+  HelpText<"Enable unwind v2 (epilog) information for x64 Windows">;
 def _SLASH_EH : CLJoined<"EH">, HelpText<"Set exception handling model">;
 def _SLASH_EP : CLFlag<"EP">,
   HelpText<"Disable linemarker output and preprocess to stdout">;

clang/lib/CodeGen/CodeGenModule.cpp

@@ -1307,6 +1307,10 @@ void CodeGenModule::Release() {
     getModule().addModuleFlag(llvm::Module::Warning, "import-call-optimization",
                               1);
 
+  // Enable unwind v2 (epilog).
+  if (CodeGenOpts.WinX64EHUnwindV2)
+    getModule().addModuleFlag(llvm::Module::Warning, "winx64-eh-unwindv2", 1);
+
   // Indicate whether this Module was compiled with -fopenmp
   if (getLangOpts().OpenMP && !getLangOpts().OpenMPSimd)
     getModule().addModuleFlag(llvm::Module::Max, "openmp", LangOpts.OpenMP);

clang/lib/Driver/ToolChains/Clang.cpp

@@ -7503,6 +7503,10 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     }
   }
 
+  // Unwind v2 (epilog) information for x64 Windows.
+  Args.addOptInFlag(CmdArgs, options::OPT_fwinx64_eh_unwindv2,
+                    options::OPT_fno_winx64_eh_unwindv2);
+
   // C++ "sane" operator new.
   Args.addOptOutFlag(CmdArgs, options::OPT_fassume_sane_operator_new,
                      options::OPT_fno_assume_sane_operator_new);
@@ -8548,6 +8552,10 @@ void Clang::AddClangCLArgs(const ArgList &Args, types::ID InputType,
   if (Args.hasArg(options::OPT__SLASH_kernel))
     CmdArgs.push_back("-fms-kernel");
 
+  // Unwind v2 (epilog) information for x64 Windows.
+  if (Args.hasArg(options::OPT__SLASH_d2epilogunwind))
+    CmdArgs.push_back("-fwinx64-eh-unwindv2");
+
   for (const Arg *A : Args.filtered(options::OPT__SLASH_guard)) {
     StringRef GuardArgs = A->getValue();
     // The only valid options are "cf", "cf,nochecks", "cf-", "ehcont" and

clang/test/CodeGen/epilog-unwind.c

@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -emit-llvm %s -o - | FileCheck %s -check-prefix=DISABLED
+// RUN: %clang_cc1 -fwinx64-eh-unwindv2 -emit-llvm %s -o - | FileCheck %s -check-prefix=ENABLED
+// RUN: %clang -fwinx64-eh-unwindv2 -S -emit-llvm %s -o - | FileCheck %s -check-prefix=ENABLED
+// RUN: %clang -fno-winx64-eh-unwindv2 -S -emit-llvm %s -o - | FileCheck %s -check-prefix=DISABLED
+
+void f(void) {}
+
+// ENABLED: !"winx64-eh-unwindv2", i32 1}
+// DISABLED-NOT: "winx64-eh-unwindv2"

clang/test/Driver/cl-options.c

@@ -820,4 +820,7 @@
 // RUN: %clang_cl -vctoolsdir "" /arm64EC /c -target x86_64-pc-windows-msvc  -### -- %s 2>&1 | FileCheck --check-prefix=ARM64EC_OVERRIDE %s
 // ARM64EC_OVERRIDE: warning: /arm64EC has been overridden by specified target: x86_64-pc-windows-msvc; option ignored
 
+// RUN: %clang_cl /d2epilogunwind /c -### -- %s 2>&1 | FileCheck %s --check-prefix=EPILOGUNWIND
+// EPILOGUNWIND: -fwinx64-eh-unwindv2
+
 void f(void) { }

llvm/include/llvm/MC/MCStreamer.h

@@ -255,11 +255,8 @@ class MCStreamer {
   bool AllowAutoPadding = false;
 
 protected:
-  // True if we are processing SEH directives in an epilogue.
-  bool InEpilogCFI = false;
-
   // Symbol of the current epilog for which we are processing SEH directives.
-  MCSymbol *CurrentEpilog = nullptr;
+  WinEH::FrameInfo::Epilog *CurrentWinEpilog = nullptr;
 
   MCFragment *CurFrag = nullptr;
 
@@ -342,9 +339,11 @@ class MCStreamer {
     return WinFrameInfos;
   }
 
-  MCSymbol *getCurrentEpilog() const { return CurrentEpilog; }
+  WinEH::FrameInfo::Epilog *getCurrentWinEpilog() const {
+    return CurrentWinEpilog;
+  }
 
-  bool isInEpilogCFI() const { return InEpilogCFI; }
+  bool isInEpilogCFI() const { return CurrentWinEpilog; }
 
   void generateCompactUnwindEncodings(MCAsmBackend *MAB);
 
@@ -1026,6 +1025,8 @@ class MCStreamer {
   virtual void emitWinCFIEndProlog(SMLoc Loc = SMLoc());
   virtual void emitWinCFIBeginEpilogue(SMLoc Loc = SMLoc());
   virtual void emitWinCFIEndEpilogue(SMLoc Loc = SMLoc());
+  virtual void emitWinCFIUnwindV2Start(SMLoc Loc = SMLoc());
+  virtual void emitWinCFIUnwindVersion(uint8_t Version, SMLoc Loc = SMLoc());
   virtual void emitWinEHHandler(const MCSymbol *Sym, bool Unwind, bool Except,
                                 SMLoc Loc = SMLoc());
   virtual void emitWinEHHandlerData(SMLoc Loc = SMLoc());

llvm/include/llvm/MC/MCWinEH.h

@@ -10,6 +10,7 @@
 #define LLVM_MC_MCWINEH_H
 
 #include "llvm/ADT/MapVector.h"
+#include "llvm/Support/SMLoc.h"
 #include <vector>
 
 namespace llvm {
@@ -42,6 +43,7 @@ struct FrameInfo {
   const MCSymbol *FuncletOrFuncEnd = nullptr;
   const MCSymbol *ExceptionHandler = nullptr;
   const MCSymbol *Function = nullptr;
+  SMLoc FunctionLoc;
   const MCSymbol *PrologEnd = nullptr;
   const MCSymbol *Symbol = nullptr;
   MCSection *TextSection = nullptr;
@@ -52,14 +54,19 @@ struct FrameInfo {
   bool HandlesExceptions = false;
   bool EmitAttempted = false;
   bool Fragment = false;
+  constexpr static uint8_t DefaultVersion = 1;
+  uint8_t Version = DefaultVersion;
 
   int LastFrameInst = -1;
   const FrameInfo *ChainedParent = nullptr;
   std::vector<Instruction> Instructions;
   struct Epilog {
     std::vector<Instruction> Instructions;
     unsigned Condition;
-    MCSymbol *End;
+    const MCSymbol *Start = nullptr;
+    const MCSymbol *End = nullptr;
+    const MCSymbol *UnwindV2Start = nullptr;
+    SMLoc Loc;
   };
   MapVector<MCSymbol *, Epilog> EpilogMap;
 

llvm/lib/MC/MCAsmStreamer.cpp

@@ -391,6 +391,8 @@ class MCAsmStreamer final : public MCStreamer {
   void emitWinCFIEndProlog(SMLoc Loc) override;
   void emitWinCFIBeginEpilogue(SMLoc Loc) override;
   void emitWinCFIEndEpilogue(SMLoc Loc) override;
+  void emitWinCFIUnwindV2Start(SMLoc Loc) override;
+  void emitWinCFIUnwindVersion(uint8_t Version, SMLoc Loc) override;
 
   void emitWinEHHandler(const MCSymbol *Sym, bool Unwind, bool Except,
                         SMLoc Loc) override;
@@ -2305,6 +2307,20 @@ void MCAsmStreamer::emitWinCFIEndEpilogue(SMLoc Loc) {
   EmitEOL();
 }
 
+void MCAsmStreamer::emitWinCFIUnwindV2Start(SMLoc Loc) {
+  MCStreamer::emitWinCFIUnwindV2Start(Loc);
+
+  OS << "\t.seh_unwindv2start";
+  EmitEOL();
+}
+
+void MCAsmStreamer::emitWinCFIUnwindVersion(uint8_t Version, SMLoc Loc) {
+  MCStreamer::emitWinCFIUnwindVersion(Version, Loc);
+
+  OS << "\t.seh_unwindversion " << (unsigned)Version;
+  EmitEOL();
+}
+
 void MCAsmStreamer::emitCGProfileEntry(const MCSymbolRefExpr *From,
                                        const MCSymbolRefExpr *To,
                                        uint64_t Count) {

llvm/lib/MC/MCParser/COFFAsmParser.cpp

@@ -96,6 +96,10 @@ class COFFAsmParser : public MCAsmParserExtension {
         ".seh_startepilogue");
     addDirectiveHandler<&COFFAsmParser::ParseSEHDirectiveEndEpilog>(
         ".seh_endepilogue");
+    addDirectiveHandler<&COFFAsmParser::ParseSEHDirectiveUnwindV2Start>(
+        ".seh_unwindv2start");
+    addDirectiveHandler<&COFFAsmParser::ParseSEHDirectiveUnwindVersion>(
+        ".seh_unwindversion");
   }
 
   bool parseSectionDirectiveText(StringRef, SMLoc) {
@@ -147,6 +151,8 @@ class COFFAsmParser : public MCAsmParserExtension {
   bool parseSEHDirectiveEndProlog(StringRef, SMLoc);
   bool ParseSEHDirectiveBeginEpilog(StringRef, SMLoc);
   bool ParseSEHDirectiveEndEpilog(StringRef, SMLoc);
+  bool ParseSEHDirectiveUnwindV2Start(StringRef, SMLoc);
+  bool ParseSEHDirectiveUnwindVersion(StringRef, SMLoc);
 
   bool parseAtUnwindOrAtExcept(bool &unwind, bool &except);
   bool parseDirectiveSymbolAttribute(StringRef Directive, SMLoc);
@@ -774,6 +780,28 @@ bool COFFAsmParser::ParseSEHDirectiveEndEpilog(StringRef, SMLoc Loc) {
   return false;
 }
 
+bool COFFAsmParser::ParseSEHDirectiveUnwindV2Start(StringRef, SMLoc Loc) {
+  Lex();
+  getStreamer().emitWinCFIUnwindV2Start(Loc);
+  return false;
+}
+
+bool COFFAsmParser::ParseSEHDirectiveUnwindVersion(StringRef, SMLoc Loc) {
+  int64_t Version;
+  if (getParser().parseIntToken(Version, "expected unwind version number"))
+    return true;
+
+  if ((Version < 1) || (Version > UINT8_MAX))
+    return Error(Loc, "invalid unwind version");
+
+  if (getLexer().isNot(AsmToken::EndOfStatement))
+    return TokError("unexpected token in directive");
+
+  Lex();
+  getStreamer().emitWinCFIUnwindVersion(Version, Loc);
+  return false;
+}
+
 bool COFFAsmParser::parseAtUnwindOrAtExcept(bool &unwind, bool &except) {
   StringRef identifier;
   if (getLexer().isNot(AsmToken::At) && getLexer().isNot(AsmToken::Percent))

llvm/lib/MC/MCStreamer.cpp

@@ -743,6 +743,7 @@ void MCStreamer::emitWinCFIStartProc(const MCSymbol *Symbol, SMLoc Loc) {
       std::make_unique<WinEH::FrameInfo>(Symbol, StartProc));
   CurrentWinFrameInfo = WinFrameInfos.back().get();
   CurrentWinFrameInfo->TextSection = getCurrentSectionOnly();
+  CurrentWinFrameInfo->FunctionLoc = Loc;
 }
 
 void MCStreamer::emitWinCFIEndProc(SMLoc Loc) {
@@ -1000,23 +1001,63 @@ void MCStreamer::emitWinCFIBeginEpilogue(SMLoc Loc) {
              "(.seh_endprologue) in " +
                  CurFrame->Function->getName());
 
-  InEpilogCFI = true;
-  CurrentEpilog = emitCFILabel();
+  MCSymbol *Label = emitCFILabel();
+  CurrentWinEpilog =
+      &CurFrame->EpilogMap.insert_or_assign(Label, WinEH::FrameInfo::Epilog())
+           .first->second;
+  CurrentWinEpilog->Start = Label;
+  CurrentWinEpilog->Loc = Loc;
 }
 
 void MCStreamer::emitWinCFIEndEpilogue(SMLoc Loc) {
   WinEH::FrameInfo *CurFrame = EnsureValidWinFrameInfo(Loc);
   if (!CurFrame)
     return;
 
-  if (!InEpilogCFI)
+  if (!CurrentWinEpilog)
     return getContext().reportError(Loc, "Stray .seh_endepilogue in " +
                                              CurFrame->Function->getName());
 
-  InEpilogCFI = false;
+  if ((CurFrame->Version >= 2) && !CurrentWinEpilog->UnwindV2Start)
+    return getContext().reportError(Loc, "Missing .seh_unwindv2start in " +
+                                             CurFrame->Function->getName());
+
+  CurrentWinEpilog->End = emitCFILabel();
+  CurrentWinEpilog = nullptr;
+}
+
+void MCStreamer::emitWinCFIUnwindV2Start(SMLoc Loc) {
+  WinEH::FrameInfo *CurFrame = EnsureValidWinFrameInfo(Loc);
+  if (!CurFrame)
+    return;
+
+  if (!CurrentWinEpilog)
+    return getContext().reportError(Loc, "Stray .seh_unwindv2start in " +
+                                             CurFrame->Function->getName());
+
+  if (CurrentWinEpilog->UnwindV2Start)
+    return getContext().reportError(Loc, "Duplicate .seh_unwindv2start in " +
+                                             CurFrame->Function->getName());
+
   MCSymbol *Label = emitCFILabel();
-  CurFrame->EpilogMap[CurrentEpilog].End = Label;
-  CurrentEpilog = nullptr;
+  CurrentWinEpilog->UnwindV2Start = Label;
+}
+
+void MCStreamer::emitWinCFIUnwindVersion(uint8_t Version, SMLoc Loc) {
+  WinEH::FrameInfo *CurFrame = EnsureValidWinFrameInfo(Loc);
+  if (!CurFrame)
+    return;
+
+  if (CurFrame->Version != WinEH::FrameInfo::DefaultVersion)
+    return getContext().reportError(Loc, "Duplicate .seh_unwindversion in " +
+                                             CurFrame->Function->getName());
+
+  if (Version != 2)
+    return getContext().reportError(
+        Loc, "Unsupported version specified in .seh_unwindversion in " +
+                 CurFrame->Function->getName());
+
+  CurFrame->Version = Version;
 }
 
 void MCStreamer::emitCOFFSafeSEH(MCSymbol const *Symbol) {}