arm64e: Workaround ptrauth-returns failure for swifttailcc

The current code generation will emit an autibsp after adjusting the
stack pointe for the tail call. If callee and caller argument area does
not match this would fail.

Author: aschwaighofer

lib/IRGen/GenCall.cpp

@@ -4785,8 +4785,9 @@ IRGenFunction::getFunctionPointerForResumeIntrinsic(llvm::Value *resume) {
   auto *fnTy = llvm::FunctionType::get(
       IGM.VoidTy, {IGM.Int8PtrTy},
       false /*vaargs*/);
-  auto signature =
-      Signature(fnTy, IGM.constructInitialAttributes(), IGM.SwiftAsyncCC);
+  auto signature = Signature(
+      fnTy, IGM.constructInitialAttributes(true /*disable ptrauth-returns*/),
+      IGM.SwiftAsyncCC);
   auto fnPtr = FunctionPointer(
       FunctionPointer::Kind::Function,
       Builder.CreateBitOrPointerCast(resume, fnTy->getPointerTo()),

lib/IRGen/GenDecl.cpp

@@ -2100,7 +2100,11 @@ llvm::Function *irgen::createFunction(IRGenModule &IGM,
       .to(fn, linkInfo.isForDefinition());
 
   llvm::AttrBuilder initialAttrs;
-  IGM.constructInitialFnAttributes(initialAttrs, FuncOptMode);
+  // Workaround an llvm bug that does not handle this case correctly.
+  bool disablePtrAuthReturns =
+      signature.getCallingConv() == llvm::CallingConv::SwiftTail;
+  IGM.constructInitialFnAttributes(initialAttrs, disablePtrAuthReturns,
+                                   FuncOptMode);
   // Merge initialAttrs with attrs.
   auto updatedAttrs =
     signature.getAttributes().addAttributes(IGM.getLLVMContext(),
@@ -2811,7 +2815,7 @@ llvm::Constant *swift::irgen::emitCXXConstructorThunkIfNeeded(
   thunk->setCallingConv(llvm::CallingConv::C);
 
   llvm::AttrBuilder attrBuilder;
-  IGM.constructInitialFnAttributes(attrBuilder);
+  IGM.constructInitialFnAttributes(attrBuilder, false /*disablePtrAuthReturns*/);
   attrBuilder.addAttribute(llvm::Attribute::AlwaysInline);
   llvm::AttributeList attr = signature.getAttributes().addAttributes(
       IGM.getLLVMContext(), llvm::AttributeList::FunctionIndex, attrBuilder);

lib/IRGen/GenFunc.cpp

@@ -1198,7 +1198,9 @@ static llvm::Value *emitPartialApplicationForwarder(IRGenModule &IGM,
   fwd->setAttributes(outAttrs);
   // Merge initial attributes with outAttrs.
   llvm::AttrBuilder b;
-  IGM.constructInitialFnAttributes(b);
+  bool disablePtrAuthReturns =
+      outSig.getCallingConv() == llvm::CallingConv::SwiftTail;
+  IGM.constructInitialFnAttributes(b, disablePtrAuthReturns);
   fwd->addAttributes(llvm::AttributeList::FunctionIndex, b);
 
   IRGenFunction subIGF(IGM, fwd);

lib/IRGen/GenObjC.cpp

@@ -717,7 +717,7 @@ static llvm::Function *emitObjCPartialApplicationForwarder(IRGenModule &IGM,
   fwd->setAttributes(attrs);
   // Merge initial attributes with attrs.
   llvm::AttrBuilder b;
-  IGM.constructInitialFnAttributes(b);
+  IGM.constructInitialFnAttributes(b, false /*disable ptr auth returns*/);
   fwd->addAttributes(llvm::AttributeList::FunctionIndex, b);
 
   IRGenFunction subIGF(IGM, fwd);

lib/IRGen/IRGenModule.cpp

@@ -1111,11 +1111,18 @@ void IRGenModule::setHasNoFramePointer(llvm::Function *F) {
 }
 
 /// Construct initial function attributes from options.
-void IRGenModule::constructInitialFnAttributes(llvm::AttrBuilder &Attrs,
-                                               OptimizationMode FuncOptMode) {
+void IRGenModule::constructInitialFnAttributes(
+    llvm::AttrBuilder &Attrs, bool disablePtrAuthReturns,
+    OptimizationMode FuncOptMode) {
   // Add the default attributes for the Clang configuration.
   clang::CodeGen::addDefaultFunctionDefinitionAttributes(getClangCGM(), Attrs);
 
+  // Disable `ptrauth-returns`. It does not work for swifttailcc lowering atm.
+  // The `autibsp` instruction executed before a tail call that adjust the stack
+  // will currently fail.
+  if (disablePtrAuthReturns)
+    Attrs.removeAttribute("ptrauth-returns");
+
   // Add/remove MinSize based on the appropriate setting.
   if (FuncOptMode == OptimizationMode::NotSet)
     FuncOptMode = IRGen.Opts.OptMode;
@@ -1128,9 +1135,10 @@ void IRGenModule::constructInitialFnAttributes(llvm::AttrBuilder &Attrs,
   }
 }
 
-llvm::AttributeList IRGenModule::constructInitialAttributes() {
+llvm::AttributeList
+IRGenModule::constructInitialAttributes(bool disablePtrAuthReturns) {
   llvm::AttrBuilder b;
-  constructInitialFnAttributes(b);
+  constructInitialFnAttributes(b, disablePtrAuthReturns);
   return llvm::AttributeList::get(getLLVMContext(),
                                   llvm::AttributeList::FunctionIndex, b);
 }

lib/IRGen/IRGenModule.h

@@ -1362,11 +1362,13 @@ private:                            \
   bool finalize();
 
   void constructInitialFnAttributes(llvm::AttrBuilder &Attrs,
+                                    bool disablePtrAuthReturns,
                                     OptimizationMode FuncOptMode =
                                       OptimizationMode::NotSet);
   void setHasNoFramePointer(llvm::AttrBuilder &Attrs);
   void setHasNoFramePointer(llvm::Function *F);
-  llvm::AttributeList constructInitialAttributes();
+  llvm::AttributeList
+  constructInitialAttributes(bool disablePtrAuthReturns = false);
 
   void emitProtocolDecl(ProtocolDecl *D);
   void emitEnumDecl(EnumDecl *D);