[SYCL] Implement virtual-table prohibit in SYCL device code.

According to SYCL specification, virtual tables are illegal in device code. This
accomplishes that in a couple of ways.  First, there is a code-gen
assert that will prevent emission of virtual tables always. Second, it
prevents virtual tables from being 'used', so non-SYCL kernel code
cannot cause v-tables to be emitted.  Finally, SYCL-specific functions
are checked for usage of polymorphic functions and a diagnostic is
emitted.

Signed-off-by: Vladimir Lazarev <[email protected]>

Author: vladimirlaz

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -9488,4 +9488,7 @@ def err_sycl_attribute_address_space_invalid : Error<
 def err_sycl_kernel_name_class_not_top_level : Error<
  "kernel name class and its template argument classes' declarations can only "
  "nest in a namespace: %0">;
+def err_sycl_virtual_types : Error<
+  "No class with a vtable can be used in a SYCL kernel or any code included in the kernel">;
+def note_sycl_used_here : Note<"used here">;
 } // end of sema component.

clang/lib/CodeGen/CodeGenTypes.cpp

@@ -719,6 +719,10 @@ llvm::StructType *CodeGenTypes::ConvertRecordDeclType(const RecordDecl *RD) {
     return Ty;
   }
 
+  assert((!Context.getLangOpts().SYCL || !isa<CXXRecordDecl>(RD) ||
+          !dyn_cast<CXXRecordDecl>(RD)->isPolymorphic()) &&
+         "Types with virtual functions not allowed in SYCL");
+
   // Okay, this is a definition of a type.  Compile the implementation now.
   bool InsertResult = RecordsBeingLaidOut.insert(Key).second;
   (void)InsertResult;

clang/lib/Sema/SemaDeclCXX.cpp

@@ -15013,6 +15013,10 @@ void Sema::MarkVTableUsed(SourceLocation Loc, CXXRecordDecl *Class,
     return;
   }
 
+  // No VTable usage is legal in SYCL, so don't bother marking them used.
+  if (getLangOpts().SYCL)
+    return;
+
   // Try to insert this class into the map.
   LoadExternalVTableUses();
   Class = Class->getCanonicalDecl();

clang/lib/Sema/SemaSYCL.cpp

@@ -49,27 +49,113 @@ class MarkDeviceFunction : public RecursiveASTVisitor<MarkDeviceFunction> {
   MarkDeviceFunction(Sema &S)
       : RecursiveASTVisitor<MarkDeviceFunction>(), SemaRef(S) {}
   bool VisitCallExpr(CallExpr *e) {
+    for (const auto &Arg : e->arguments())
+      CheckTypeForVirtual(Arg->getType(), Arg->getSourceRange());
+
     if (FunctionDecl *Callee = e->getDirectCallee()) {
       // Remember that all SYCL kernel functions have deferred
       // instantiation as template functions. It means that
       // all functions used by kernel have already been parsed and have
       // definitions.
+
+      CheckTypeForVirtual(Callee->getReturnType(), Callee->getSourceRange());
+
       if (FunctionDecl *Def = Callee->getDefinition()) {
         if (!Def->hasAttr<SYCLDeviceAttr>()) {
           Def->addAttr(SYCLDeviceAttr::CreateImplicit(SemaRef.Context));
           this->TraverseStmt(Def->getBody());
-          // But because parser works with top level declarations and CodeGen
-          // already saw and ignored our function without device attribute we
-          // need to add this function into SYCL kernels array to show it
-          // this function again.
           SemaRef.AddSyclKernel(Def);
         }
       }
     }
     return true;
   }
 
+  bool VisitCXXConstructExpr(CXXConstructExpr *E) {
+    for (const auto &Arg : E->arguments())
+      CheckTypeForVirtual(Arg->getType(), Arg->getSourceRange());
+
+    CXXConstructorDecl *Ctor = E->getConstructor();
+
+    if (FunctionDecl *Def = Ctor->getDefinition()) {
+      Def->addAttr(SYCLDeviceAttr::CreateImplicit(SemaRef.Context));
+      this->TraverseStmt(Def->getBody());
+      SemaRef.AddSyclKernel(Def);
+    }
+
+    const auto *ConstructedType = Ctor->getParent();
+    if (ConstructedType->hasUserDeclaredDestructor()) {
+      CXXDestructorDecl *Dtor = ConstructedType->getDestructor();
+
+      if (FunctionDecl *Def = Dtor->getDefinition()) {
+        Def->addAttr(SYCLDeviceAttr::CreateImplicit(SemaRef.Context));
+        this->TraverseStmt(Def->getBody());
+        SemaRef.AddSyclKernel(Def);
+      }
+    }
+    return true;
+  }
+
+  bool VisitTypedefNameDecl(TypedefNameDecl *TD) {
+    CheckTypeForVirtual(TD->getUnderlyingType(), TD->getLocation());
+    return true;
+  }
+
+  bool VisitRecordDecl(RecordDecl *RD) {
+    CheckTypeForVirtual(QualType{RD->getTypeForDecl(), 0}, RD->getLocation());
+    return true;
+  }
+
+  bool VisitParmVarDecl(VarDecl *VD) {
+    CheckTypeForVirtual(VD->getType(), VD->getLocation());
+    return true;
+  }
+
+  bool VisitVarDecl(VarDecl *VD) {
+    CheckTypeForVirtual(VD->getType(), VD->getLocation());
+    return true;
+  }
+
+  bool VisitDeclRefExpr(DeclRefExpr *E) {
+    CheckTypeForVirtual(E->getType(), E->getSourceRange());
+    return true;
+  }
+
 private:
+  bool CheckTypeForVirtual(QualType Ty, SourceRange Loc) {
+    while (Ty->isAnyPointerType() || Ty->isArrayType())
+      Ty = QualType{Ty->getPointeeOrArrayElementType(), 0};
+
+    if (const auto *CRD = Ty->getAsCXXRecordDecl()) {
+      if (CRD->isPolymorphic()) {
+        SemaRef.Diag(CRD->getLocation(), diag::err_sycl_virtual_types);
+        SemaRef.Diag(Loc.getBegin(), diag::note_sycl_used_here);
+        return false;
+      }
+
+      for (const auto &Field : CRD->fields()) {
+        if (!CheckTypeForVirtual(Field->getType(), Field->getSourceRange())) {
+          SemaRef.Diag(Loc.getBegin(), diag::note_sycl_used_here);
+          return false;
+        }
+      }
+    } else if (const auto *RD = Ty->getAsRecordDecl()) {
+      for (const auto &Field : RD->fields()) {
+        if (!CheckTypeForVirtual(Field->getType(), Field->getSourceRange())) {
+          SemaRef.Diag(Loc.getBegin(), diag::note_sycl_used_here);
+          return false;
+        }
+      }
+    } else if (const auto *FPTy = dyn_cast<FunctionProtoType>(Ty)) {
+      for (const auto &ParamTy : FPTy->param_types())
+        if (!CheckTypeForVirtual(ParamTy, Loc))
+          return false;
+      return CheckTypeForVirtual(FPTy->getReturnType(), Loc);
+    } else if (const auto *FTy = dyn_cast<FunctionType>(Ty)) {
+      return CheckTypeForVirtual(FTy->getReturnType(), Loc);
+    }
+    return true;
+  }
   Sema &SemaRef;
 };
 

clang/test/SemaSYCL/no-vtables.cpp

@@ -0,0 +1,30 @@
+// RUN: %clang_cc1 -fsycl-is-device -verify -fsyntax-only -x c++ -emit-llvm-only %s
+// expected-no-diagnostics
+// Should never fail, since the type is never used in kernel code.
+
+struct Base {
+  virtual void f(){}
+};
+
+struct Inherit : Base {
+  virtual void f() override {}
+};
+
+void always_uses() {
+  Inherit u;
+}
+
+void usage() {
+}
+
+
+template <typename name, typename Func>
+__attribute__((sycl_kernel)) void kernel_single_task(Func kernelFunc) {
+  kernelFunc();
+}
+int main() {
+  always_uses();
+  kernel_single_task<class fake_kernel>([]() { usage(); });
+  return 0;
+}
+

clang/test/SemaSYCL/no-vtables2.cpp

@@ -0,0 +1,49 @@
+// RUN: %clang_cc1 -fsycl-is-device -Wno-return-type -verify -fsyntax-only -x c++ -emit-llvm-only %s
+
+struct Base {
+  virtual void f() const {}
+};
+
+// expected-error@+1 9{{No class with a vtable can be used in a SYCL kernel or any code included in the kernel}}
+struct Inherit : Base {
+  virtual void f() const override {}
+};
+
+Inherit always_uses() {
+  Inherit u;
+}
+
+static constexpr Inherit IH;
+
+// expected-note@+1{{used here}}
+Inherit *usage_child(){}
+
+  // expected-note@+1{{used here}}
+Inherit usage() {
+  // expected-note@+1{{used here}}
+  Inherit u;
+  // expected-note@+1{{used here}}
+  Inherit *u_ptr;
+
+  // expected-note@+1{{used here}}
+  using foo = Inherit;
+  // expected-note@+1{{used here}}
+  typedef Inherit bar;
+  // expected-note@+1{{used here}}
+  IH.f();
+
+  // expected-note@+1{{used here}}
+  usage_child();
+}
+
+
+template <typename name, typename Func>
+__attribute__((sycl_kernel)) void kernel_single_task(Func kernelFunc) {
+  kernelFunc();
+}
+int main() {
+  // expected-note@+1{{used here}}
+  kernel_single_task<class fake_kernel>([]() { usage(); });
+  return 0;
+}
+

clang/test/SemaSYCL/no-vtables3.cpp

@@ -0,0 +1,42 @@
+// RUN: %clang_cc1 -fsycl-is-device -Wno-return-type -verify -fsyntax-only -x c++ -emit-llvm-only %s
+
+struct Base {
+  virtual void f() const {}
+};
+
+// expected-error@+1 3{{No class with a vtable can be used in a SYCL kernel or any code included in the kernel}}
+struct Inherit : Base {
+  virtual void f() const override {}
+};
+
+struct Wrapper{
+  Wrapper() {
+    // expected-note@+1{{used here}}
+    Inherit IH;
+  }
+
+  void Func() {
+    // expected-note@+1{{used here}}
+    Inherit IH;
+  }
+
+  ~Wrapper() {
+  // expected-note@+1{{used here}}
+    Inherit IH;
+  }
+};
+
+void usage() {
+  Wrapper WR;
+  WR.Func();
+}
+
+template <typename name, typename Func>
+__attribute__((sycl_kernel)) void kernel_single_task(Func kernelFunc) {
+  kernelFunc();
+}
+int main() {
+  kernel_single_task<class fake_kernel>([]() { usage(); });
+  return 0;
+}
+

clang/test/SemaSYCL/no-vtables4.cpp

@@ -0,0 +1,30 @@
+// RUN: %clang_cc1 -fsycl-is-device -Wno-return-type -verify -fsyntax-only -x c++ -emit-llvm-only %s
+
+struct Base {
+  virtual void f() const {}
+};
+
+// expected-error@+1{{No class with a vtable can be used in a SYCL kernel or any code included in the kernel}}
+struct Inherit : Base {
+  virtual void f() const override {}
+};
+
+struct Wrapper{
+  // expected-note@+1{{used here}}
+  Inherit I;
+};
+
+void usage() {
+  // expected-note@+1{{used here}}
+  Wrapper WR;
+}
+
+template <typename name, typename Func>
+__attribute__((sycl_kernel)) void kernel_single_task(Func kernelFunc) {
+  kernelFunc();
+}
+int main() {
+  kernel_single_task<class fake_kernel>([]() { usage(); });
+  return 0;
+}
+