[cxx-interop] Remove logic around applying attributes.

Removes the logic around applying attributes to C++ constructor's
indirect results.

Also fixes some commenting.

Author: zoecarver

lib/ClangImporter/ImportDecl.cpp

@@ -3522,9 +3522,6 @@ namespace {
       if (decl->getDefinition() && !decl->isBeingDefined() &&
           !decl->isDependentContext() &&
           decl->needsImplicitDefaultConstructor()) {
-        // Casting away const here should be OK because
-        // SwiftDeclConverter::Visit() is in practice called with a non-const
-        // argument.
         clang::CXXConstructorDecl *ctor =
             clangSema.DeclareImplicitDefaultConstructor(
                 const_cast<clang::CXXRecordDecl *>(decl));
@@ -3927,7 +3924,7 @@ namespace {
         FuncDecl *func =
             createFuncOrAccessor(Impl.SwiftContext, loc, accessorInfo, name,
                                  nameLoc, bodyParams, resultTy,
-                                 /*async*/ false, /*throws*/ false, dc, decl);
+                                 /*async=*/false, /*throws=*/false, dc, decl);
         result = func;
 
         if (!dc->isModuleScopeContext()) {

lib/IRGen/GenCall.cpp

@@ -338,12 +338,10 @@ llvm::CallingConv::ID irgen::expandCallingConv(IRGenModule &IGM,
 
 static void addIndirectResultAttributes(IRGenModule &IGM,
                                         llvm::AttributeList &attrs,
-                                        unsigned paramIndex, bool allowSRet,
-                                        bool noCapture = true) {
+                                        unsigned paramIndex, bool allowSRet) {
   llvm::AttrBuilder b;
   b.addAttribute(llvm::Attribute::NoAlias);
-  if (noCapture)
-    b.addAttribute(llvm::Attribute::NoCapture);
+  b.addAttribute(llvm::Attribute::NoCapture);
   if (allowSRet)
     b.addAttribute(llvm::Attribute::StructRet);
   attrs = attrs.addAttributes(IGM.getLLVMContext(),
@@ -1429,18 +1427,6 @@ void SignatureExpansion::expandExternalSignatureTypes() {
     }
   }
 
-  if (formalIndirectResult) {
-    // If the result is a formal indirect result in SIL, that means that the
-    // Clang function has an explicit output parameter (e.g. it's a C++
-    // constructor). This means:
-    // - Don't mark it `sret`, as this should only be used for C++ return
-    //   values.
-    // - The Clang function might capture the pointer, so don't specify
-    //   `nocapture`.
-    addIndirectResultAttributes(IGM, Attrs, 0, /* allowSRet = */ false,
-                                /* noCapture = */ false);
-  }
-
   if (returnInfo.isIndirect() || returnInfo.isIgnore()) {
     ResultIRType = IGM.VoidTy;
   } else {

test/Interop/Cxx/class/constructors-irgen.swift

@@ -12,23 +12,9 @@ struct UnsafePointer<T> { }
 struct UnsafeMutablePointer<T> { }
 
 public func createHasVirtualBase() -> HasVirtualBase {
-  // - The `this` parameter should carry a `noalias` attribute, as it is
-  //   guaranteed that nothing will alias the object before it has been fully
-  //   constructed. Note that this doesn't apply on ABIs (Itanium ARM,
-  //   Microsoft x64) where we insert an (inlined) thunk; in this case, we're
-  //   getting the attributes of the constructor that was generated by Clang,
-  //   which doesn't insert these attributes.
-  //
-  // - The `this` parameter should _not_ carry an `sret` attribute because the
-  //   constructor doesn't return the constructed object as a return value.
-  //
-  // - The `this` parameter should _not_ carry a `nocapture` attribute (unlike
-  //   Swift constructors that return their result indirectly) because the C++
-  //   constructor has explicit access to `this` and may capture it.
-  //
   // ITANIUM_X64: define swiftcc void @"$ss20createHasVirtualBaseSo0bcD0VyF"(%TSo14HasVirtualBaseV* noalias nocapture sret %0)
   // ITANIUM_X64-NOT: define
-  // ITANIUM_X64: call void @_ZN14HasVirtualBaseC1E7ArgType(%struct.HasVirtualBase* noalias %{{[0-9]+}}, i32 %{{[0-9]+}})
+  // ITANIUM_X64: call void @_ZN14HasVirtualBaseC1E7ArgType(%struct.HasVirtualBase* %{{[0-9]+}}, i32 %{{[0-9]+}})
   //
   // ITANIUM_ARM: define protected swiftcc void @"$ss20createHasVirtualBaseSo0bcD0VyF"(%TSo14HasVirtualBaseV* noalias nocapture sret %0)
   // To verify that the thunk is inlined, make sure there's no intervening
@@ -48,7 +34,7 @@ public func createHasVirtualBase() -> HasVirtualBase {
 public func createImplicitDefaultConstructor() -> ImplicitDefaultConstructor {
   // ITANIUM_X64: define swiftcc i32 @"$ss32createImplicitDefaultConstructorSo0bcD0VyF"()
   // ITANIUM_X64-NOT: define
-  // ITANIUM_X64: call void @_ZN26ImplicitDefaultConstructorC1Ev(%struct.ImplicitDefaultConstructor* noalias %{{[0-9]+}})
+  // ITANIUM_X64: call void @_ZN26ImplicitDefaultConstructorC1Ev(%struct.ImplicitDefaultConstructor* %{{[0-9]+}})
   //
   // ITANIUM_ARM: define protected swiftcc i32 @"$ss32createImplicitDefaultConstructorSo0bcD0VyF"()
   // ITANIUM_ARM-NOT: define
@@ -66,7 +52,7 @@ public func createStructWithSubobjectCopyConstructorAndValue() {
   // ITANIUM_X64-LABEL: define swiftcc void @"$ss48createStructWithSubobjectCopyConstructorAndValueyyF"()
   // ITANIUM_X64: [[MEMBER:%.*]] = alloca %TSo33StructWithCopyConstructorAndValueV
   // ITANIUM_X64: [[MEMBER_AS_STRUCT:%.*]] = bitcast %TSo33StructWithCopyConstructorAndValueV* %member to %struct.StructWithCopyConstructorAndValue*
-  // ITANIUM_X64: void @_ZN33StructWithCopyConstructorAndValueC1Ev(%struct.StructWithCopyConstructorAndValue* noalias [[MEMBER_AS_STRUCT]])
+  // ITANIUM_X64: void @_ZN33StructWithCopyConstructorAndValueC1Ev(%struct.StructWithCopyConstructorAndValue* [[MEMBER_AS_STRUCT]])
   // ITANIUM_X64: call %TSo33StructWithCopyConstructorAndValueV* @"$sSo33StructWithCopyConstructorAndValueVWOc"(%TSo33StructWithCopyConstructorAndValueV* [[MEMBER]], %TSo33StructWithCopyConstructorAndValueV* [[TMP:%.*]])
   // ITANIUM_X64: [[OBJ_MEMBER:%.*]] = getelementptr inbounds %TSo42StructWithSubobjectCopyConstructorAndValueV, %TSo42StructWithSubobjectCopyConstructorAndValueV* %obj, i32 0, i32 0
   // ITANIUM_X64: call %TSo33StructWithCopyConstructorAndValueV* @"$sSo33StructWithCopyConstructorAndValueVWOb"(%TSo33StructWithCopyConstructorAndValueV* [[TMP]], %TSo33StructWithCopyConstructorAndValueV* [[OBJ_MEMBER]])

test/Interop/Cxx/class/constructors-objc-irgen.swift

@@ -11,6 +11,6 @@ public func createConstructorWithNSArrayParam() -> ConstructorWithNSArrayParam {
   // CHECK: [[VAR:%[0-9]+]] = alloca %TSo27ConstructorWithNSArrayParamV, align 1
   // CHECK: %{{[0-9]+}} = call swiftcc %TSo7NSArrayC* @"$sSa10FoundationE19_bridgeToObjectiveCSo7NSArrayCyF"(%swift.bridge* %{{[0-9]+}}, %swift.type* getelementptr inbounds (%swift.full_type, %swift.full_type* @"$sypN", i32 0, i32 1))
   // CHECK: [[CAST_VAR:%[0-9]+]] = bitcast %TSo27ConstructorWithNSArrayParamV* [[VAR]] to %struct.ConstructorWithNSArrayParam*
-  // CHECK: call void @_ZN27ConstructorWithNSArrayParamC1EP7NSArray(%struct.ConstructorWithNSArrayParam* noalias [[CAST_VAR]], [[VAR]]* %{{[0-9]+}})
+  // CHECK: call void @_ZN27ConstructorWithNSArrayParamC1EP7NSArray(%struct.ConstructorWithNSArrayParam* [[CAST_VAR]], [[VAR]]* %{{[0-9]+}})
   return ConstructorWithNSArrayParam([])
 }