Add trace stitching.

src/lj_dispatch.c

@@ -42,6 +42,12 @@ LJ_STATIC_ASSERT(GG_NUM_ASMFF == FF_NUM_ASMFUNC);
 #include <math.h>
 LJ_FUNCA_NORET void LJ_FASTCALL lj_ffh_coroutine_wrap_err(lua_State *L,
 							  lua_State *co);
+#if !LJ_HASJIT
+#define lj_dispatch_stitch	lj_dispatch_ins
+#endif
+#if !LJ_HASPROFILE
+#define lj_dispatch_profile	lj_dispatch_ins
+#endif
 
 #define GOTFUNC(name)	(ASMFunction)name,
 static const ASMFunction dispatch_got[] = {
@@ -511,6 +517,23 @@ out:
   return makeasmfunc(lj_bc_ofs[op]);  /* Return static dispatch target. */
 }
 
+#if LJ_HASJIT
+/* Stitch a new trace. */
+void LJ_FASTCALL lj_dispatch_stitch(jit_State *J, const BCIns *pc)
+{
+  ERRNO_SAVE
+  lua_State *L = J->L;
+  void *cf = cframe_raw(L->cframe);
+  const BCIns *oldpc = cframe_pc(cf);
+  setcframe_pc(cf, pc);
+  /* Before dispatch, have to bias PC by 1. */
+  L->top = L->base + cur_topslot(curr_proto(L), pc+1, cframe_multres_n(cf));
+  lj_trace_stitch(J, pc-1);  /* Point to the CALL instruction. */
+  setcframe_pc(cf, oldpc);
+  ERRNO_RESTORE
+}
+#endif
+
 #if LJ_HASPROFILE
 /* Profile dispatch. */
 void LJ_FASTCALL lj_dispatch_profile(lua_State *L, const BCIns *pc)