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

Author: dpaoliello

clang/include/clang/Basic/CodeGenOptions.def

@@ -476,6 +476,9 @@ CODEGENOPT(ImportCallOptimization, 1, 0)
 /// (BlocksRuntime) on Windows.
 CODEGENOPT(StaticClosure, 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

@@ -7659,6 +7659,10 @@ def import_call_optimization : Flag<["-"], "import-call-optimization">,
              "by the Windows kernel to enable import call optimization">,
     MarshallingInfoFlag<CodeGenOpts<"ImportCallOptimization">>;
 
+def epilog_unwind : Flag<["-"], "winx64-eh-unwindv2">,
+  HelpText<"Enable unwind v2 (epilog) information for x64 Windows">,
+  MarshallingInfoFlag<CodeGenOpts<"WinX64EHUnwindV2">>;
+
 } // let Visibility = [CC1Option]
 
 //===----------------------------------------------------------------------===//
@@ -8771,6 +8775,8 @@ 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

@@ -1303,6 +1303,10 @@ 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

@@ -8529,6 +8529,9 @@ void Clang::AddClangCLArgs(const ArgList &Args, types::ID InputType,
   if (Args.hasArg(options::OPT__SLASH_kernel))
     CmdArgs.push_back("-fms-kernel");
 
+  if (Args.hasArg(options::OPT__SLASH_d2epilogunwind))
+    CmdArgs.push_back("-winx64-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 +1,5 @@
+// RUN: %clang_cc1 -winx64-eh-unwindv2 -emit-llvm %s -o - | FileCheck %s
+
+void f(void) {}
+
+// CHECK: !"winx64-eh-unwindv2", i32 1}

clang/test/Driver/cl-options.c

@@ -817,4 +817,7 @@
 // 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: -winx64-eh-unwindv2
+
 void f(void) { }

llvm/include/llvm/MC/MCStreamer.h

@@ -259,7 +259,7 @@ class MCStreamer {
   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;
 
@@ -342,7 +342,9 @@ class MCStreamer {
     return WinFrameInfos;
   }
 
-  MCSymbol *getCurrentEpilog() const { return CurrentEpilog; }
+  WinEH::FrameInfo::Epilog *getCurrentWinEpilog() const {
+    return CurrentWinEpilog;
+  }
 
   bool isInEpilogCFI() const { return InEpilogCFI; }
 
@@ -1026,6 +1028,8 @@ 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 +10,8 @@
 #define LLVM_MC_MCWINEH_H
 
 #include "llvm/ADT/MapVector.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Support/SMLoc.h"
 #include <vector>
 
 namespace llvm {
@@ -42,6 +44,7 @@ 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;
@@ -52,16 +55,21 @@ 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;
+  std::vector<Epilog> Epilogs;
 
   // For splitting unwind info of large functions
   struct Segment {
@@ -70,7 +78,7 @@ struct FrameInfo {
     bool HasProlog;
     MCSymbol *Symbol = nullptr;
     // Map an Epilog's symbol to its offset within the function.
-    MapVector<MCSymbol *, int64_t> Epilogs;
+    MapVector<const MCSymbol *, int64_t> Epilogs;
 
     Segment(int64_t Offset, int64_t Length, bool HasProlog = false)
         : Offset(Offset), Length(Length), HasProlog(HasProlog) {}
@@ -89,11 +97,21 @@ struct FrameInfo {
   bool empty() const {
     if (!Instructions.empty())
       return false;
-    for (const auto &E : EpilogMap)
-      if (!E.second.Instructions.empty())
+    for (const auto &E : Epilogs)
+      if (!E.Instructions.empty())
         return false;
     return true;
   }
+
+  auto findEpilog(const MCSymbol *Start) const {
+    return llvm::find_if(Epilogs,
+                         [Start](const Epilog &E) { return E.Start == Start; });
+  }
+
+  auto findEpilog(const MCSymbol *Start) {
+    return llvm::find_if(Epilogs,
+                         [Start](Epilog &E) { return E.Start == Start; });
+  }
 };
 
 class UnwindEmitter {

llvm/lib/MC/MCAsmStreamer.cpp

@@ -390,6 +390,8 @@ 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;
@@ -2304,6 +2306,20 @@ 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);
@@ -767,6 +773,28 @@ 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) {
@@ -1001,7 +1002,10 @@ void MCStreamer::emitWinCFIBeginEpilogue(SMLoc Loc) {
                  CurFrame->Function->getName());
 
   InEpilogCFI = true;
-  CurrentEpilog = emitCFILabel();
+  CurFrame->Epilogs.push_back(WinEH::FrameInfo::Epilog());
+  CurrentWinEpilog = &CurFrame->Epilogs.back();
+  CurrentWinEpilog->Start = emitCFILabel();
+  CurrentWinEpilog->Loc = Loc;
 }
 
 void MCStreamer::emitWinCFIEndEpilogue(SMLoc Loc) {
@@ -1013,10 +1017,50 @@ void MCStreamer::emitWinCFIEndEpilogue(SMLoc Loc) {
     return getContext().reportError(Loc, "Stray .seh_endepilogue in " +
                                              CurFrame->Function->getName());
 
+  assert(CurrentWinEpilog);
+  if ((CurFrame->Version >= 2) && !CurrentWinEpilog->UnwindV2Start)
+    return getContext().reportError(Loc, "Missing .seh_unwindv2start in " +
+                                             CurFrame->Function->getName());
+
   InEpilogCFI = false;
   MCSymbol *Label = emitCFILabel();
-  CurFrame->EpilogMap[CurrentEpilog].End = Label;
-  CurrentEpilog = nullptr;
+  CurrentWinEpilog->End = Label;
+  CurrentWinEpilog = nullptr;
+}
+
+void MCStreamer::emitWinCFIUnwindV2Start(SMLoc Loc) {
+  WinEH::FrameInfo *CurFrame = EnsureValidWinFrameInfo(Loc);
+  if (!CurFrame)
+    return;
+
+  if (!InEpilogCFI)
+    return getContext().reportError(Loc, "Stray .seh_unwindv2start in " +
+                                             CurFrame->Function->getName());
+
+  assert(CurrentWinEpilog);
+  if (CurrentWinEpilog->UnwindV2Start)
+    return getContext().reportError(Loc, "Duplicate .seh_unwindv2start in " +
+                                             CurFrame->Function->getName());
+
+  MCSymbol *Label = emitCFILabel();
+  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) {}