[cxx-interop] evaluate default constructor's unevaluated exception spec if needed when emitting C++ constructor call

Fixes #65891

Author: hyp

lib/IRGen/GenCall.cpp

@@ -28,6 +28,7 @@
 #include "clang/Basic/TargetInfo.h"
 #include "clang/CodeGen/CodeGenABITypes.h"
 #include "clang/CodeGen/ModuleBuilder.h"
+#include "clang/Sema/Sema.h"
 #include "llvm/IR/GlobalPtrAuthInfo.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/Support/Compiler.h"
@@ -4555,6 +4556,23 @@ bool IRGenModule::isForeignExceptionHandlingEnabled() const {
          !clangLangOpts.IgnoreExceptions;
 }
 
+bool IRGenModule::isCxxNoThrow(clang::FunctionDecl *fd, bool defaultNoThrow) {
+  auto *fpt = fd->getType()->getAs<clang::FunctionProtoType>();
+  if (!fpt)
+    return defaultNoThrow;
+  if (fpt->getExceptionSpecType() ==
+      clang::ExceptionSpecificationType::EST_Unevaluated) {
+    // Clang might not have evaluated the exception spec for
+    // a constructor, so force the evaluation of it.
+    auto &clangSema = Context.getClangModuleLoader()->getClangSema();
+    clangSema.EvaluateImplicitExceptionSpec(fd->getLocation(), fd);
+    fpt = fd->getType()->getAs<clang::FunctionProtoType>();
+    if (!fpt)
+      return defaultNoThrow;
+  }
+  return fpt->isNothrow();
+}
+
 /// Emit the epilogue for the function.
 void IRGenFunction::emitEpilogue() {
   if (EarliestIP != AllocaIP)

lib/IRGen/GenDecl.cpp

@@ -3275,11 +3275,9 @@ llvm::CallBase *swift::irgen::emitCXXConstructorCall(
     IRGenFunction &IGF, const clang::CXXConstructorDecl *ctor,
     llvm::FunctionType *ctorFnType, llvm::Constant *ctorAddress,
     llvm::ArrayRef<llvm::Value *> args) {
-  bool canThrow = IGF.IGM.isForeignExceptionHandlingEnabled();
-  if (auto *fpt = ctor->getType()->getAs<clang::FunctionProtoType>()) {
-    if (fpt->isNothrow())
-      canThrow = false;
-  }
+  bool canThrow =
+      IGF.IGM.isForeignExceptionHandlingEnabled() &&
+      !IGF.IGM.isCxxNoThrow(const_cast<clang::CXXConstructorDecl *>(ctor));
   if (!canThrow)
     return IGF.Builder.CreateCall(ctorFnType, ctorAddress, args);
   llvm::CallBase *result;

lib/IRGen/GenStruct.cpp

@@ -720,11 +720,8 @@ namespace {
       }
       bool canThrow = false;
       if (IGF.IGM.isForeignExceptionHandlingEnabled()) {
-        if (auto *fpt =
-                destructor->getType()->getAs<clang::FunctionProtoType>()) {
-          if (!fpt->isNothrow())
-            canThrow = true;
-        }
+        if (!IGF.IGM.isCxxNoThrow(destructor, /*defaultNoThrow=*/true))
+          canThrow = true;
       }
       if (canThrow) {
         IGF.createExceptionTrapScope([&](llvm::BasicBlock *invokeNormalDest,

lib/IRGen/IRGenModule.h

@@ -1826,6 +1826,9 @@ private:                                                                       \
 
   bool isForeignExceptionHandlingEnabled() const;
 
+  /// Returns true if the given Clang function does not throw exceptions.
+  bool isCxxNoThrow(clang::FunctionDecl *fd, bool defaultNoThrow = false);
+
 private:
   llvm::Constant *
   getAddrOfSharedContextDescriptor(LinkEntity entity,

lib/IRGen/IRGenSIL.cpp

@@ -2780,12 +2780,10 @@ void IRGenSILFunction::visitFunctionRefBaseInst(FunctionRefBaseInst *i) {
   FunctionPointer fp =
       FunctionPointer::forDirect(fpKind, value, secondaryValue, sig, useSignature);
   // Update the foreign no-throw information if needed.
-  if (const auto *cd = fn->getClangDecl()) {
+  if (auto *cd = fn->getClangDecl()) {
     if (auto *cfd = dyn_cast<clang::FunctionDecl>(cd)) {
-      if (auto *cft = cfd->getType()->getAs<clang::FunctionProtoType>()) {
-        if (cft->isNothrow())
-          fp.setForeignNoThrow();
-      }
+      if (IGM.isCxxNoThrow(const_cast<clang::FunctionDecl *>(cfd)))
+        fp.setForeignNoThrow();
     }
     if (IGM.emittedForeignFunctionThunksWithExceptionTraps.count(fnPtr))
       fp.setForeignCallCatchesExceptionInThunk();

test/Interop/Cxx/exceptions/trap-on-exception-irgen-itanium.swift

@@ -131,6 +131,33 @@ public:
   inline ClassWithNoThrowingConstructor() noexcept {}
 };
 
+struct StructWithDefaultConstructor {
+  StructWithDefaultConstructor() = default;
+
+  int m = 0;
+};
+
+
+struct NonTrivial {
+  ~NonTrivial() {}
+};
+
+struct StructWithDefaultCopyConstructor {
+  StructWithDefaultCopyConstructor() noexcept {}
+  StructWithDefaultCopyConstructor(const StructWithDefaultCopyConstructor &) = default;
+
+  int m = 0;
+  NonTrivial _nonTrivialPoison;
+};
+
+struct StructWithDefaultDestructor {
+  StructWithDefaultDestructor() noexcept {}
+  ~StructWithDefaultDestructor() = default;
+
+  int m = 0;
+  NonTrivial _nonTrivialPoison;
+};
+
 //--- test.swift
 
 import CxxModule
@@ -227,6 +254,22 @@ func testClassWithNoThrowingConstructor() -> CInt {
   return obj.m
 }
 
+func testStructWithDefaultConstructor() -> StructWithDefaultConstructor {
+  return StructWithDefaultConstructor()
+}
+
+func testStructWithDefaultCopyConstructor() -> CInt {
+  var s = StructWithDefaultCopyConstructor()
+  let copy = s
+  return s.m
+}
+
+func testStructWithDefaultDestructor() -> CInt {
+  let s = StructWithDefaultDestructor()
+  let result = s.m
+  return result
+}
+
 let _ = testFreeFunctionNoThrowOnly()
 let _ = testFreeFunctionCalls()
 let _ = testMethodCalls()
@@ -241,6 +284,9 @@ let _ = testClassWithCopyConstructor()
 let _ = testClassWithThrowingCopyConstructor()
 let _ = testClassWithThrowingConstructor()
 let _ = testClassWithNoThrowingConstructor()
+let _ = testStructWithDefaultConstructor()
+let _ = testStructWithDefaultCopyConstructor()
+let _ = testStructWithDefaultDestructor()
 
 // CHECK: define {{.*}} @"$s4test0A23FreeFunctionNoThrowOnlys5Int32VyF"() #[[#SWIFTMETA:]] {
 // CHECK-NEXT: :
@@ -393,6 +439,18 @@ let _ = testClassWithNoThrowingConstructor()
 // CHECK-NOT: invoke
 // CHECK: }
 
+// CHECK: define {{.*}} @"$s4test0A28StructWithDefaultConstructorSo0bcdE0VyF"() #[[#SWIFTMETA]] {
+// CHECK-NOT: invoke
+// CHECK: }
+
+// CHECK: define {{.*}} @"$s4test0A32StructWithDefaultCopyConstructors5Int32VyF"() #[[#SWIFTMETA]] {
+// CHECK-NOT: invoke
+// CHECK: }
+
+// CHECK: define {{.*}} @"$s4test0A27StructWithDefaultDestructors5Int32VyF"() #[[#SWIFTMETA]] {
+// CHECK-NOT: invoke
+// CHECK: }
+
 // CHECK: i32 @__gxx_personality_v0(...)
 
 // CHECK: attributes #[[#SWIFTMETA]] = {