X-Git-Url: http://git.joshuawise.com/firearm.git/blobdiff_plain/960947a70a85ad40fe2569500806552d11f1e02d..a4c270c74d821e221d30d405bca8676963f29340:/Fetch.v diff --git a/Fetch.v b/Fetch.v index 3b6d9c5..2a9d69d 100644 --- a/Fetch.v +++ b/Fetch.v @@ -12,37 +12,49 @@ module Fetch( input [31:0] jmppc, output reg bubble = 1, output reg [31:0] insn = 0, - output reg [31:0] pc = 0); - - reg [31:0] prevpc; - reg [31:0] nextpc; - initial - prevpc = 32'hFFFFFFFC; /* ugh... the first pc we request will be this +4 */ - always @(negedge Nrst) - prevpc <= 32'hFFFFFFFC; - - always @(*) - if (!Nrst) - nextpc = 32'hFFFFFFFC; - else if (stall) /* don't change any internal state */ - nextpc = prevpc; + output reg [31:0] pc = 32'hFFFFFFFC); + + reg qjmp = 0; /* A jump has been queued up while we were waiting. */ + reg [31:0] qjmppc; + always @(posedge clk) + if ((rd_wait || stall) && jmp && !qjmp) + {qjmp,qjmppc} <= {jmp, jmppc}; + else if (!rd_wait && !stall && qjmp) /* It has already been intoed. */ + {qjmp,qjmppc} <= {1'b0, 32'hxxxxxxxx}; + + reg [31:0] reqpc; + always @(*) + if (stall) + reqpc = pc; + else if (qjmp) + reqpc = qjmppc; else if (jmp) - nextpc = jmppc; + reqpc = jmppc; else - nextpc = prevpc + 32'h4; + reqpc = pc + 4; + + assign rd_addr = reqpc; + assign rd_req = 1; + + always @(negedge Nrst) + begin + pc <= 32'hFFFFFFFC; + qjmp <= 0; + bubble <= 1; + end - assign rd_addr = pc; - assign rd_req = !stall; - always @(posedge clk) begin - if (!rd_wait || !Nrst) - prevpc <= nextpc; - if (!stall) + if (!Nrst) begin + pc <= 32'hFFFFFFFC; + qjmp <= 0; + bubble <= 1; + end else if (!stall) begin bubble <= rd_wait; insn <= rd_data; - pc <= nextpc; + if (!rd_wait) + pc <= reqpc; end end endmodule