[SEH] Fix regression with SEH in noexpect functions

[ogoffart]

Summary

Commit 5baea0560160a693b19022c5d0ba637b6b46b2d8 set the CurCodeDecl
because it was needed to pass the assert in CodeGenFunction::EmitLValueForLambdaField,
But this was not right to do as CodeGenFunction::FinishFunction passes it to EmitEndEHSpec
and cause corruption of the EHStack.

Revert the part of the commit that changes the CurCodeDecl, and just change the assert
to allow more conditions.

[ogoffart]

As reported in https://reviews.llvm.org/D97687#2741449

[rnk]

I went ahead and implemented my suggested changes and pushed this with attribution. Thanks for the fix!

clang/lib/CodeGen/CGException.cpp

1966

I think passing GlobalDecl() here is intentional, there must have been some reason to have the helper CGF have a null function. This noexcept thing seems like one such example.

clang/lib/CodeGen/CGExpr.cpp

4188

Other uses of CurCodeDecl check it for null, so I think it makes sense to go ahead and do the same here.

clang/lib/CodeGen/CGException.cpp

const CGFunctionInfo &FnInfo =
     CGM.getTypes().arrangeBuiltinFunctionDeclaration(RetTy, Args);
 
   llvm::FunctionType *FnTy = CGM.getTypes().GetFunctionType(FnInfo);
   llvm::Function *Fn = llvm::Function::Create(
       FnTy, llvm::GlobalValue::InternalLinkage, Name.str(), &CGM.getModule());
 
   IsOutlinedSEHHelper = true;
 
   StartFunction(GlobalDecl(), RetTy, Fn, FnInfo, Args,
                 OutlinedStmt->getBeginLoc(), OutlinedStmt->getBeginLoc());
   CurSEHParent = ParentCGF.CurSEHParent;
-  CurCodeDecl = ParentCGF.CurCodeDecl;
 
   CGM.SetInternalFunctionAttributes(GlobalDecl(), CurFn, FnInfo);
   EmitCapturedLocals(ParentCGF, OutlinedStmt, IsFilter);
 }
 
 /// Create a stub filter function that will ultimately hold the code of the
 /// filter expression. The EH preparation passes in LLVM will outline the code
 /// from the main function body into this stub.

clang/lib/CodeGen/CGExpr.cpp

if (const auto *FD = dyn_cast<FunctionDecl>(ND))
     return EmitFunctionDeclLValue(*this, E, FD);
 
   llvm_unreachable("Unhandled member declaration!");
 }
 
 /// Given that we are currently emitting a lambda, emit an l-value for
 /// one of its members.
 LValue CodeGenFunction::EmitLValueForLambdaField(const FieldDecl *Field) {
+  if (CurCodeDecl) {
     assert(cast<CXXMethodDecl>(CurCodeDecl)->getParent()->isLambda());
     assert(cast<CXXMethodDecl>(CurCodeDecl)->getParent() == Field->getParent());
+  }
   QualType LambdaTagType =
     getContext().getTagDeclType(Field->getParent());
   LValue LambdaLV = MakeNaturalAlignAddrLValue(CXXABIThisValue, LambdaTagType);
   return EmitLValueForField(LambdaLV, Field);
 }
 
 /// Get the field index in the debug info. The debug info structure/union
 /// will ignore the unnamed bitfields.

clang/test/CodeGenCXX/exceptions-seh.cpp

 // CHECK: icmp eq i32 %{{.*}}, 424242
 // CHECK: zext i1 %{{.*}} to i32
 // CHECK: ret i32
 
 // CHECK-LABEL: define internal void @"?fin$0@0@use_seh_in_inline_func@@"(i8 %abnormal_termination, i8* %frame_pointer) #{{[0-9]+}}
 // CHECK: store i32 1234, i32* @my_unique_global
 
 // CHECK: attributes #[[NOINLINE]] = { {{.*noinline.*}} }
+
+void seh_in_noexcept() noexcept { __try {} __finally {} }