Re-land r228258 and make clang-cl's /EHs- disable -fexceptions again

After r228258, Clang started emitting C++ EH IR that LLVM wasn't ready
to deal with, even when exceptions were disabled with /EHs-. This time,
make /EHs- turn off -fexceptions while still emitting exceptional
constructs in functions using __try.  Since Sema rejects C++ exception
handling constructs before CodeGen, landingpads should only appear in
such functions as the result of a __try.

llvm-svn: 228329

3 files changed, 59 insertions, 36 deletions

diff --git a/clang/lib/CodeGen/CGException.cpp b/clang/lib/CodeGen/CGException.cpp
index e148227c39a..5ddd3bbb82b 100644
--- a/clang/lib/CodeGen/CGException.cpp
+++ b/clang/lib/CodeGen/CGException.cpp
@@ -128,7 +128,12 @@ namespace {
     // This function must have prototype void(void*).
     const char *CatchallRethrowFn;
 
-    static const EHPersonality &get(CodeGenModule &CGM);
+    static const EHPersonality &get(CodeGenModule &CGM,
+                                    const FunctionDecl *FD);
+    static const EHPersonality &get(CodeGenFunction &CGF) {
+      return get(CGF.CGM, dyn_cast_or_null<FunctionDecl>(CGF.CurCodeDecl));
+    }
+
     static const EHPersonality GNU_C;
     static const EHPersonality GNU_C_SJLJ;
     static const EHPersonality GNU_C_SEH;
@@ -141,6 +146,7 @@ namespace {
     static const EHPersonality GNU_CPlusPlus_SEH;
     static const EHPersonality MSVC_except_handler;
     static const EHPersonality MSVC_C_specific_handler;
+    static const EHPersonality MSVC_CxxFrameHandler3;
   };
 }
 
@@ -167,6 +173,8 @@ const EHPersonality
 EHPersonality::MSVC_except_handler = { "_except_handler3", nullptr };
 const EHPersonality
 EHPersonality::MSVC_C_specific_handler = { "__C_specific_handler", nullptr };
+const EHPersonality
+EHPersonality::MSVC_CxxFrameHandler3 = { "__CxxFrameHandler3", nullptr };
 
 /// On Win64, use libgcc's SEH personality function. We fall back to dwarf on
 /// other platforms, unless the user asked for SjLj exceptions.
@@ -239,35 +247,27 @@ static const EHPersonality &getObjCXXPersonality(const llvm::Triple &T,
   llvm_unreachable("bad runtime kind");
 }
 
-static const EHPersonality &getCPersonalityMSVC(const llvm::Triple &T,
-                                                const LangOptions &L) {
-  if (L.SjLjExceptions)
-    return EHPersonality::GNU_C_SJLJ;
-
+static const EHPersonality &getSEHPersonalityMSVC(const llvm::Triple &T) {
   if (T.getArch() == llvm::Triple::x86)
     return EHPersonality::MSVC_except_handler;
   return EHPersonality::MSVC_C_specific_handler;
 }
 
-static const EHPersonality &getCXXPersonalityMSVC(const llvm::Triple &T,
-                                                  const LangOptions &L) {
-  if (L.SjLjExceptions)
-    return EHPersonality::GNU_CPlusPlus_SJLJ;
-  // FIXME: Implement C++ exceptions.
-  return getCPersonalityMSVC(T, L);
-}
-
-const EHPersonality &EHPersonality::get(CodeGenModule &CGM) {
+const EHPersonality &EHPersonality::get(CodeGenModule &CGM,
+                                        const FunctionDecl *FD) {
   const llvm::Triple &T = CGM.getTarget().getTriple();
   const LangOptions &L = CGM.getLangOpts();
+
   // Try to pick a personality function that is compatible with MSVC if we're
   // not compiling Obj-C. Obj-C users better have an Obj-C runtime that supports
   // the GCC-style personality function.
   if (T.isWindowsMSVCEnvironment() && !L.ObjC1) {
-    if (L.CPlusPlus)
-      return getCXXPersonalityMSVC(T, L);
+    if (L.SjLjExceptions)
+      return EHPersonality::GNU_CPlusPlus_SJLJ;
+    else if (FD && FD->usesSEHTry())
+      return getSEHPersonalityMSVC(T);
     else
-      return getCPersonalityMSVC(T, L);
+      return EHPersonality::MSVC_CxxFrameHandler3;
   }
 
   if (L.CPlusPlus && L.ObjC1)
@@ -354,7 +354,7 @@ void CodeGenModule::SimplifyPersonality() {
   if (!LangOpts.ObjCRuntime.isNeXTFamily())
     return;
 
-  const EHPersonality &ObjCXX = EHPersonality::get(*this);
+  const EHPersonality &ObjCXX = EHPersonality::get(*this, /*FD=*/nullptr);
   const EHPersonality &CXX =
       getCXXPersonality(getTarget().getTriple(), LangOpts);
   if (&ObjCXX == &CXX)
@@ -737,8 +737,16 @@ llvm::BasicBlock *CodeGenFunction::getInvokeDestImpl() {
   assert(EHStack.requiresLandingPad());
   assert(!EHStack.empty());
 
-  if (!CGM.getLangOpts().Exceptions)
-    return nullptr;
+  // If exceptions are disabled, there are usually no landingpads. However, when
+  // SEH is enabled, functions using SEH still get landingpads.
+  const LangOptions &LO = CGM.getLangOpts();
+  if (!LO.Exceptions) {
+    if (!LO.Borland && !LO.MicrosoftExt)
+      return nullptr;
+    const auto *FD = dyn_cast_or_null<FunctionDecl>(CurCodeDecl);
+    if (!FD || !FD->usesSEHTry())
+      return nullptr;
+  }
 
   // Check the innermost scope for a cached landing pad.  If this is
   // a non-EH cleanup, we'll check enclosing scopes in EmitLandingPad.
@@ -778,7 +786,7 @@ llvm::BasicBlock *CodeGenFunction::EmitLandingPad() {
   CGBuilderTy::InsertPoint savedIP = Builder.saveAndClearIP();
   auto DL = ApplyDebugLocation::CreateDefaultArtificial(*this, CurEHLocation);
 
-  const EHPersonality &personality = EHPersonality::get(CGM);
+  const EHPersonality &personality = EHPersonality::get(*this);
 
   // Create and configure the landing pad.
   llvm::BasicBlock *lpad = createBasicBlock("lpad");
@@ -1595,7 +1603,7 @@ llvm::BasicBlock *CodeGenFunction::getTerminateLandingPad() {
   Builder.SetInsertPoint(TerminateLandingPad);
 
   // Tell the backend that this is a landing pad.
-  const EHPersonality &Personality = EHPersonality::get(CGM);
+  const EHPersonality &Personality = EHPersonality::get(*this);
   llvm::LandingPadInst *LPadInst =
     Builder.CreateLandingPad(llvm::StructType::get(Int8PtrTy, Int32Ty, nullptr),
                              getOpaquePersonalityFn(CGM, Personality), 0);
@@ -1654,7 +1662,7 @@ llvm::BasicBlock *CodeGenFunction::getEHResumeBlock(bool isCleanup) {
   EHResumeBlock = createBasicBlock("eh.resume");
   Builder.SetInsertPoint(EHResumeBlock);
 
-  const EHPersonality &Personality = EHPersonality::get(CGM);
+  const EHPersonality &Personality = EHPersonality::get(*this);
 
   // This can always be a call because we necessarily didn't find
   // anything on the EH stack which needs our help.
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index d24375b3d78..8634ed604c6 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -4877,10 +4877,10 @@ void Clang::AddClangCLArgs(const ArgList &Args, ArgStringList &CmdArgs) const {
   const Driver &D = getToolChain().getDriver();
   EHFlags EH = parseClangCLEHFlags(D, Args);
   // FIXME: Do something with NoExceptC.
-  if (EH.Synch || EH.Asynch)
+  if (EH.Synch || EH.Asynch) {
     CmdArgs.push_back("-fcxx-exceptions");
-  // Always add -fexceptions to allow SEH __try.
-  CmdArgs.push_back("-fexceptions");
+    CmdArgs.push_back("-fexceptions");
+  }
 
   // /EP should expand to -E -P.
   if (Args.hasArg(options::OPT__SLASH_EP)) {
diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index d17cf227011..4761c32f78d 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -3303,11 +3303,12 @@ StmtResult Sema::ActOnCXXTryBlock(SourceLocation TryLoc, Stmt *TryBlock,
   if (getCurScope() && getCurScope()->isOpenMPSimdDirectiveScope())
     Diag(TryLoc, diag::err_omp_simd_region_cannot_use_stmt) << "try";
 
+  sema::FunctionScopeInfo *FSI = getCurFunction();
+
   // C++ try is incompatible with SEH __try.
-  if (!getLangOpts().Borland && getCurFunction()->FirstSEHTryLoc.isValid()) {
+  if (!getLangOpts().Borland && FSI->FirstSEHTryLoc.isValid()) {
     Diag(TryLoc, diag::err_mixing_cxx_try_seh_try);
-    Diag(getCurFunction()->FirstSEHTryLoc, diag::note_conflicting_try_here)
-        << "'__try'";
+    Diag(FSI->FirstSEHTryLoc, diag::note_conflicting_try_here) << "'__try'";
   }
 
   const unsigned NumHandlers = Handlers.size();
@@ -3352,7 +3353,7 @@ StmtResult Sema::ActOnCXXTryBlock(SourceLocation TryLoc, Stmt *TryBlock,
     }
   }
 
-  getCurFunction()->setHasCXXTry(TryLoc);
+  FSI->setHasCXXTry(TryLoc);
 
   // FIXME: We should detect handlers that cannot catch anything because an
   // earlier handler catches a superclass. Need to find a method that is not
@@ -3367,15 +3368,29 @@ StmtResult Sema::ActOnSEHTryBlock(bool IsCXXTry, SourceLocation TryLoc,
                                   Stmt *TryBlock, Stmt *Handler) {
   assert(TryBlock && Handler);
 
+  sema::FunctionScopeInfo *FSI = getCurFunction();
+
   // SEH __try is incompatible with C++ try. Borland appears to support this,
   // however.
-  if (!getLangOpts().Borland && getCurFunction()->FirstCXXTryLoc.isValid()) {
-    Diag(TryLoc, diag::err_mixing_cxx_try_seh_try);
-    Diag(getCurFunction()->FirstCXXTryLoc, diag::note_conflicting_try_here)
-        << "'try'";
+  if (!getLangOpts().Borland) {
+    if (FSI->FirstCXXTryLoc.isValid()) {
+      Diag(TryLoc, diag::err_mixing_cxx_try_seh_try);
+      Diag(FSI->FirstCXXTryLoc, diag::note_conflicting_try_here) << "'try'";
+    }
   }
 
-  getCurFunction()->setHasSEHTry(TryLoc);
+  FSI->setHasSEHTry(TryLoc);
+
+  // Reject __try in Obj-C methods, blocks, and captured decls, since we don't
+  // track if they use SEH.
+  DeclContext *DC = CurContext;
+  while (DC && !DC->isFunctionOrMethod())
+    DC = DC->getParent();
+  FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(DC);
+  if (FD)
+    FD->setUsesSEHTry(true);
+  else
+    Diag(TryLoc, diag::err_seh_try_outside_functions);
 
   return SEHTryStmt::Create(Context, IsCXXTry, TryLoc, TryBlock, Handler);
 }