JDK-8284563 adds an `assert(VM_Version::supports_sve()`in `get_current_sve_vector_length()` on aarch64/linux if the processor supports SME but not SVE(2). This makes compilation of debug builds fail.

int VM_Version::get_current_sve_vector_length() {
  assert(VM_Version::supports_sve(), "should not call this");
  return prctl(PR_SVE_GET_VL);
}

This seems to be unintended, because the caller checks whether the call fails, and automatically disables SVE use, i.e.

  if (UseSVE > 0) {
    int vl = get_current_sve_vector_length(); // Fails here.
    if (vl < 0) { // Checks here.
      warning("Unable to get SVE vector length on this system. "
              "Disabling SVE. Specify -XX:UseSVE=0 to shun this warning.");
      FLAG_SET_DEFAULT(UseSVE, 0);
 
If the assert() were intentional, the whole check after the call would not make sense.

Can be reproduced using a VM emulating Apple processors.

May either be a wrong assert, or wrong detection of SVE(2).