diff options
-rw-r--r-- | include/llvm/Support/Casting.h | 13 | ||||
-rw-r--r-- | unittests/Support/Casting.cpp | 51 |
2 files changed, 63 insertions, 1 deletions
diff --git a/include/llvm/Support/Casting.h b/include/llvm/Support/Casting.h index d35febbe6d..0c71882a77 100644 --- a/include/llvm/Support/Casting.h +++ b/include/llvm/Support/Casting.h @@ -15,6 +15,7 @@ #ifndef LLVM_SUPPORT_CASTING_H #define LLVM_SUPPORT_CASTING_H +#include "llvm/Support/type_traits.h" #include <cassert> namespace llvm { @@ -44,13 +45,23 @@ template<typename From> struct simplify_type<const From> { // The core of the implementation of isa<X> is here; To and From should be // the names of classes. This template can be specialized to customize the // implementation of isa<> without rewriting it from scratch. -template <typename To, typename From> +template <typename To, typename From, typename Enabler = void> struct isa_impl { static inline bool doit(const From &Val) { return To::classof(&Val); } }; +/// \brief Always allow upcasts, and perform no dynamic check for them. +template <typename To, typename From> +struct isa_impl<To, From, + typename llvm::enable_if_c< + llvm::is_base_of<To, From>::value + >::type + > { + static inline bool doit(const From &) { return true; } +}; + template <typename To, typename From> struct isa_impl_cl { static inline bool doit(const From &Val) { return isa_impl<To, From>::doit(Val); diff --git a/unittests/Support/Casting.cpp b/unittests/Support/Casting.cpp index dc0205f325..ad564aa366 100644 --- a/unittests/Support/Casting.cpp +++ b/unittests/Support/Casting.cpp @@ -153,3 +153,54 @@ const bar *B2 = &B; } // anonymous namespace bar *llvm::fub() { return 0; } + +namespace { +namespace inferred_upcasting { +// This test case verifies correct behavior of inferred upcasts when the +// types are statically known to be OK to upcast. This is the case when, +// for example, Derived inherits from Base, and we do `isa<Base>(Derived)`. + +// Note: This test will actually fail to compile without inferred +// upcasting. + +class Base { +public: + // No classof. We are testing that the upcast is inferred. + Base() {} +}; + +class Derived : public Base { +public: + Derived() {} +}; + +// Even with no explicit classof() in Base, we should still be able to cast +// Derived to its base class. +TEST(CastingTest, UpcastIsInferred) { + Derived D; + EXPECT_TRUE(isa<Base>(D)); + Base *BP = dyn_cast<Base>(&D); + EXPECT_TRUE(BP != NULL); +} + + +// This test verifies that the inferred upcast takes precedence over an +// explicitly written one. This is important because it verifies that the +// dynamic check gets optimized away. +class UseInferredUpcast { +public: + int Dummy; + static bool classof(const UseInferredUpcast *) { + return false; + } +}; + +TEST(CastingTest, InferredUpcastTakesPrecedence) { + UseInferredUpcast UIU; + // Since the explicit classof() returns false, this will fail if the + // explicit one is used. + EXPECT_TRUE(isa<UseInferredUpcast>(&UIU)); +} + +} // end namespace inferred_upcasting +} // end anonymous namespace |