8294087: RISC-V: RVC: Fix a potential alignment issue and add more alignment assertions for the patchable calls/nops

Reviewed-by: shade, fjiang, fyang

src/hotspot/cpu/riscv/macroAssembler_riscv.hpp

@@ -30,6 +30,7 @@
 #include "asm/assembler.hpp"
 #include "code/vmreg.hpp"
 #include "metaprogramming/enableIf.hpp"
+#include "nativeInst_riscv.hpp"
 #include "oops/compressedOops.hpp"
 #include "utilities/powerOfTwo.hpp"
 
@@ -49,6 +50,9 @@ class MacroAssembler: public Assembler {
 
   // Alignment
   int align(int modulus, int extra_offset = 0);
+  static inline void assert_alignment(address pc, int alignment = NativeInstruction::instruction_size) {
+    assert(is_aligned(pc, alignment), "bad alignment");
+  }
 
   // Stack frame creation/removal
   // Note that SP must be updated to the right place before saving/restoring RA and FP