Implement branching in fetch stage

1 files changed, 27 insertions, 6 deletions

diff --git a/rtl/core/fetch/fetch.sv b/rtl/core/fetch/fetch.sv
index e8f4832..a57c679 100644
--- a/rtl/core/fetch/fetch.sv
+++ b/rtl/core/fetch/fetch.sv
@@ -5,6 +5,7 @@ module core_fetch
 (
 	input  logic clk,
 	             stall,
+	             branch,
 	             flush,
 	             fetched,
 	input  word  fetch_data,
@@ -16,19 +17,39 @@ module core_fetch
 	             addr
 );
 
-	ptr next_pc;
+	ptr next_pc, head;
+	logic fetched_valid, do_flush, discard;
+
+	assign do_flush = branch | flush;
+	assign fetched_valid = fetched & ~discard;
 
 	core_prefetch #(.ORDER(PREFETCH_ORDER)) prefetch
 	(
+		.flush(do_flush),
+		.fetched(fetched_valid),
 		.*
 	);
 
-	always_ff @(posedge clk)
-		if(flush)
-			addr <= next_pc;
-		else if(fetched)
+	always_comb
+		if(branch)
+			head = target;
+		else if(flush)
+			head = next_pc;
+		else
+			head = {30{1'bx}};
+
+	always_ff @(posedge clk) begin
+		if(do_flush)
+			addr <= head;
+		else if(fetched_valid)
 			addr <= addr + 1;
 
-	initial addr = 0;
+		discard <= discard ? ~fetched : do_flush & fetch;
+	end
+
+	initial begin
+		addr = 0;
+		discard = 0;
+	end
 
 endmodule