RISC-V: Elimilate warning in class vcreate

The following is the content of class vcreate:
class vcreate : public function_base
{
public:
  gimple *fold (gimple_folder &f) const override
  {
    ....
  }

  rtx expand (function_expander &e) const override
  {
    return NULL_RTX;
  }
};

The warning caused is:
./riscv-gcc/gcc/config/riscv/riscv-vector-builtins-bases.cc:1719:34:
  warning: unused parameter 'e' [-Wunused-parameter]
  rtx expand (function_expander &e) const override
                                 ^

gcc/ChangeLog:

	* config/riscv/riscv-vector-builtins-bases.cc: remove unused
		parameter e and replace NULL_RTX with gcc_unreachable.

1 files changed, 2 insertions, 2 deletions

diff --git a/gcc/config/riscv/riscv-vector-builtins-bases.cc b/gcc/config/riscv/riscv-vector-builtins-bases.cc
index be3df2c..ee218a0 100644
--- a/gcc/config/riscv/riscv-vector-builtins-bases.cc
+++ b/gcc/config/riscv/riscv-vector-builtins-bases.cc
@@ -1856,9 +1856,9 @@ public:
     return clobber;
   }
 
-  rtx expand (function_expander &e) const override
+  rtx expand (function_expander &) const override
   {
-    return NULL_RTX;
+    gcc_unreachable ();
   }
 };