e203 riscv中复位代码

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/ The rst_flag is the synced version of rst_n
//    * rst_n is asserted
// The rst_flag will be clear when
//    * rst_n is de-asserted
  wire reset_flag_r;
  sirv_gnrl_dffrs #(1) reset_flag_dffrs (1'b0, reset_flag_r, clk, rst_n);
//
// The reset_req valid is set when
//    * Currently reset_flag is asserting
// The reset_req valid is clear when
//    * Currently reset_req is asserting
//    * Currently the flush can be accepted by IFU
  wire reset_req_r;
  wire reset_req_set = (~reset_req_r) & reset_flag_r;
  wire reset_req_clr = reset_req_r & ifu_req_hsked;
  wire reset_req_ena = reset_req_set | reset_req_clr;
  wire reset_req_nxt = reset_req_set | (~reset_req_clr);

  sirv_gnrl_dfflr #(1) reset_req_dfflr (reset_req_ena, reset_req_nxt, reset_req_r, clk, rst_n);

  wire ifu_reset_req = reset_req_r;

这是取指模块e203_ifu_ifetch.v中的一段代码，没见过这种写法，不理解复位信号为什么这样处理？