msgSend: Return nil if the dtable cannot be loaded

benchmarks/CMakeLists.txt

@@ -0,0 +1,6 @@
+find_package(benchmark REQUIRED)
+
+add_executable(objc_msgSend objc_msgSend.cpp TestClass.m)
+
+target_compile_options(objc_msgSend PRIVATE "-fobjc-runtime=gnustep-2.0")
+target_link_libraries(objc_msgSend benchmark::benchmark objc)

benchmarks/TestClass.m

@@ -0,0 +1,10 @@
+@interface TestClass
+- (int)answer;
+@end
+
+@implementation TestClass
+- (int)answer
+{
+	return 42;
+}
+@end

benchmarks/objc_msgSend.cpp

@@ -0,0 +1,23 @@
+#include <benchmark/benchmark.h>
+#include "../objc/runtime.h"
+#include <assert.h>
+
+static id testClass;
+static SEL answerSel;
+
+static void objc_msgSendSetup(const benchmark::State& state) {
+  testClass = objc_getClass("TestClass");
+  answerSel = sel_registerName("answer");
+}
+
+static void objc_msgSend(benchmark::State& state) {
+    for (auto _ : state)
+	  {
+      id a = objc_msgSend(testClass, answerSel);
+      assert((uintptr_t)a == 42);
+    }
+  }
+  // Register the function as a benchmark
+  BENCHMARK(objc_msgSend)->Setup(objc_msgSendSetup)->Repetitions(25);
+
+  BENCHMARK_MAIN();

objc_msgSend.x86-64.S

@@ -35,6 +35,8 @@
 	mov   (\receiver), %r10               # Load the dtable from the class
 1:	                                      # classLoaded
 	mov   DTABLE_OFFSET(%r10), %r10       # Load the dtable from the class into r10
+	test  %r10, %r10                      # If the dtable is nil
+	jz    4f                              # return nil
 	mov   %rax, -8(%rsp)                  # %rax contains information for variadic calls
 	mov   %rbx, -16(%rsp)                 # On the fast path, spill into the red zone
 	mov   (\sel), %eax                    # Load the selector index into %eax