luaK_reserveregs
luaK_reserveregs(fs, 1);
luaK_reserveregs(fs, 1);
luaK_reserveregs(fs, 1);
luaK_reserveregs(fs, 2); /* function and 'self' produced by op_self */
LUAI_FUNC void luaK_reserveregs (FuncState *fs, int n);
luaK_reserveregs(fs, 1);
luaK_reserveregs(fs, nvars);
luaK_reserveregs(fs, 1);
if (extra > 1) luaK_reserveregs(fs, extra-1);
luaK_reserveregs(fs, extra);
luaK_reserveregs(fs, fs->nactvar); /* reserve register for parameters */