diff a/src/hotspot/share/opto/matcher.hpp b/src/hotspot/share/opto/matcher.hpp
--- a/src/hotspot/share/opto/matcher.hpp
+++ b/src/hotspot/share/opto/matcher.hpp
@@ -336,10 +336,14 @@
   static const bool vector_size_supported(const BasicType bt, int size) {
     return (Matcher::max_vector_size(bt) >= size &&
             Matcher::min_vector_size(bt) <= size);
   }
 
+  static const bool supports_scalable_vector();
+  // Actual max scalable vector register length.
+  static const int scalable_vector_reg_size(const BasicType bt);
+
   // Vector ideal reg
   static const uint vector_ideal_reg(int len);
 
   // CPU supports misaligned vectors store/load.
   static const bool misaligned_vectors_ok();