8368893: RISC-V: crash after JDK-8352673 on fastdebug version

Reviewed-by: fyang, dzhang

Author: Hamlin Li

src/hotspot/cpu/riscv/vm_version_riscv.cpp

@@ -213,13 +213,8 @@ void VM_Version::common_initialize() {
   }
 
   if (UseRVV) {
-    if (!ext_V.enabled() && FLAG_IS_DEFAULT(UseRVV)) {
-      warning("RVV is not supported on this CPU");
-      FLAG_SET_DEFAULT(UseRVV, false);
-    } else {
-      // read vector length from vector CSR vlenb
-      _initial_vector_length = cpu_vector_length();
-    }
+    // read vector length from vector CSR vlenb
+    _initial_vector_length = cpu_vector_length();
   }
 
   // Misc Intrinsics that could depend on RVV.

src/hotspot/os_cpu/linux_riscv/vm_version_linux_riscv.cpp

@@ -100,7 +100,6 @@
 #endif
 
 uint32_t VM_Version::cpu_vector_length() {
-  assert(ext_V.enabled(), "should not call this");
   return (uint32_t)read_csr(CSR_VLENB);
 }