[CodeGen][UBSan] Handle sugared QualTypes correctly in

getUBSanFunctionTypeHash.

getUBSanFunctionTypeHash checks if a Type is a FunctionNoPrototype
by calling isa<FunctionNoProtoType>(). This does not work correctly when
the Type is wrapped in a sugar type such as an AttributedType. This
patch fixes this by using isFunctionNoProtoType() function which removes
sugar and returns the expected result.

The added test is a sanity check that the compiler no longer crashes
during compilation. It also compares the hash with and without the
function attribute for both FunctionNoProtoType and FunctionProtoType.
The hash remains the same for FunctionNoProtoType even with the addition
of an attribute.

rdar://113144087

Differential Revision: https://reviews.llvm.org/D157445

clang/lib/CodeGen/CodeGenFunction.cpp

@@ -572,7 +572,7 @@ llvm::ConstantInt *
 CodeGenFunction::getUBSanFunctionTypeHash(QualType Ty) const {
   // Remove any (C++17) exception specifications, to allow calling e.g. a
   // noexcept function through a non-noexcept pointer.
-  if (!isa<FunctionNoProtoType>(Ty))
+  if (!Ty->isFunctionNoProtoType())
     Ty = getContext().getFunctionTypeWithExceptionSpec(Ty, EST_None);
   std::string Mangled;
   llvm::raw_string_ostream Out(Mangled);

clang/test/CodeGen/ubsan-function-attributed.c

@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -S -triple x86_64 -std=c17 -fsanitize=function %s -o - | FileCheck %s --check-prefixes=CHECK
+
+// CHECK: .long	248076293
+void __attribute__((ms_abi)) f(void) {}
+
+// CHECK: .long	905068220
+void g(void) {}
+
+// CHECK: .long	1717976574
+void __attribute__((ms_abi)) f_no_prototype() {}
+
+// CHECK: .long	1717976574
+void g_no_prototype() {}