runtime: use 16 bit barriers on riscv

Author: nickwanninger

runtime/core/barrier.cpp

@@ -11,6 +11,7 @@
 #define UNW_LOCAL_ONLY
 #include <libunwind.h>
 #include <alaska/StackMapParser.h>
+#include <alaska/config.h>
 
 
 #include <dlfcn.h>
@@ -74,6 +75,9 @@ using inst_t = uint16_t;
 #ifdef __aarch64__
 using inst_t = uint32_t;
 #endif
+#ifdef __riscv
+using inst_t = uint16_t;
+#endif
 
 struct PatchPoint {
   inst_t* pc;
@@ -619,6 +623,12 @@ void parse_stack_map(uint8_t* t) {
       p.inst_sig = 0x00000000;  // udf #0
 #endif
 
+
+#ifdef __riscv
+      p.inst_nop = 0x0001;  // nop
+      p.inst_sig = 0x0000;  // unimp
+#endif
+
       patchPoints.push(p);
     }
     if (record.getID() == 'PATC') {