JVM_FindClassFromClass checks if the incoming "from" parameter could be null. This check is unnecessary and confusing, as subsequent code uses "from" without a null check.

https://github.com/openjdk/jdk/blob/80ab094a75a6474c33214e3347e08ea7b9177ec8/src/hotspot/share/prims/jvm.cpp#L834-L836

  Klass* from_class = (from_class_oop == nullptr)
                           ? (Klass*)nullptr
                           : java_lang_Class::as_Klass(from_class_oop);
  oop class_loader = nullptr;
  if (from_class != nullptr) {
     ....

However, JVM_FindClassFromClass() is called only from load_class_local() with context->class:

https://github.com/openjdk/jdk/blob/80ab094a75a6474c33214e3347e08ea7b9177ec8/src/java.base/share/native/libverify/check_code.c#L567-L568

static jclass load_class_local(context_type *context,const char *classname)
{
    jclass cb = JVM_FindClassFromClass(context->env, classname,
                                 JNI_FALSE, context->class);

context->class is set only in a single location, VerifyClassForMajorVersion():

https://github.com/openjdk/jdk/blob/80ab094a75a6474c33214e3347e08ea7b9177ec8/src/java.base/share/native/libverify/check_code.c#L770-L790


JNIEXPORT jboolean
VerifyClassForMajorVersion(JNIEnv *env, jclass cb, char *buffer, jint len,
                           jint major_version)
{
    [...]
    memset(context, 0, sizeof(context_type));
    [...]
    context->class = cb;


VerifyClassForMajorVersion() has only a single caller, Verifier::inference_verify(), which never passes a null class in the "cb" parameter:

https://github.com/openjdk/jdk/blob/80ab094a75a6474c33214e3347e08ea7b9177ec8/src/hotspot/share/classfile/verifier.cpp#L322

Symbol* Verifier::inference_verify(
    InstanceKlass* klass, char* message, size_t message_len, TRAPS) {
   [...]
  jclass cls = (jclass) JNIHandles::make_local(thread, klass->java_mirror());
   [...]
    result = (*verify_func)(env, cls, message, (int)message_len, klass->major_version());