lj_auditlog.c: Log strings referenced as IR constants

The main motivation is to support decoding HREFK constant hashtable
key names.

src/lj_auditlog.c

@@ -158,10 +158,21 @@ static void log_jit_State(jit_State *J)
 
 static void log_GCtrace(GCtrace *T)
 {
+  IRRef ref;
   log_mem("MCode[]", T->mcode, T->szmcode);
   log_mem("SnapShot[]", T->snap, T->nsnap * sizeof(*T->snap));
   log_mem("SnapEntry[]", T->snapmap, T->nsnapmap * sizeof(*T->snapmap));
   log_mem("IRIns[]", &T->ir[T->nk], (T->nins - T->nk + 1) * sizeof(IRIns));
+  for (ref = T->nk; ref < REF_TRUE; ref++) {
+    IRIns *ir = &T->ir[ref];
+    if (ir->o == IR_KGC) {
+      GCobj *o = ir_kgc(ir);
+      /* Log referenced string constants. For e.g. HREFK table keys. */
+      if (o->gch.gct == ~LJ_TSTR) {
+        log_GCobj(o);
+      }
+    }
+  }
   log_mem("GCtrace", T, sizeof(*T));
 }