[ORC] Add an ExecutorAddr::toPtr overload for function types.

In the common case of converting an ExecutorAddr to a function pointer type,
this eliminates the need for the '(*)' boilerplate to explicitly specify a
function pointer. E.g.:

auto *F = A.toPtr<int(*)()>();

can now be written as

auto *F = A.toPtr<int()>();

Author: lhames

llvm/include/llvm/ExecutionEngine/Orc/Shared/ExecutorAddress.h

@@ -43,13 +43,22 @@ class ExecutorAddr {
 
   /// Cast this ExecutorAddr to a pointer of the given type.
   /// Warning: This should only be used when JITing in-process.
-  template <typename T> T toPtr() const {
-    static_assert(std::is_pointer<T>::value, "T must be a pointer type");
+  template <typename T>
+  std::enable_if_t<std::is_pointer<T>::value, T> toPtr() const {
     uintptr_t IntPtr = static_cast<uintptr_t>(Addr);
     assert(IntPtr == Addr && "ExecutorAddr value out of range for uintptr_t");
     return reinterpret_cast<T>(IntPtr);
   }
 
+  /// Cast this ExecutorAddr to a pointer of the given function type.
+  /// Warning: This should only be used when JITing in-process.
+  template <typename T>
+  std::enable_if_t<std::is_function<T>::value, T *> toPtr() const {
+    uintptr_t IntPtr = static_cast<uintptr_t>(Addr);
+    assert(IntPtr == Addr && "ExecutorAddr value out of range for uintptr_t");
+    return reinterpret_cast<T *>(IntPtr);
+  }
+
   uint64_t getValue() const { return Addr; }
   void setValue(uint64_t Addr) { this->Addr = Addr; }
   bool isNull() const { return Addr == 0; }

llvm/unittests/ExecutionEngine/Orc/ExecutorAddressTest.cpp

@@ -47,6 +47,17 @@ TEST(ExecutorAddrTest, PtrConversion) {
   EXPECT_EQ(XPtr, &X);
 }
 
+static void F() {}
+
+TEST(ExecutorAddrTest, PtrConversionWithFunctionType) {
+  // Test that function types (as opposed to function pointer types) can be
+  // used with toPtr.
+  auto FAddr = ExecutorAddr::fromPtr(F);
+  void (*FPtr)() = FAddr.toPtr<void()>();
+
+  EXPECT_EQ(FPtr, &F);
+}
+
 TEST(ExecutorAddrTest, AddrRanges) {
   ExecutorAddr A0(0), A1(1), A2(2), A3(3);
   ExecutorAddrRange R0(A0, A1), R1(A1, A2), R2(A2, A3), R3(A0, A2), R4(A1, A3);