X-Git-Url: http://git.joshuawise.com/firearm.git/blobdiff_plain/ae281afdd15d606536d5b445b49cbc3bafcb9b7c..2c523f8ab5b2d5e0d2a5e34f360d16439861171e:/Issue.v

diff --git a/Issue.v b/Issue.v
index 1dbdc20..fcc2c0c 100644
--- a/Issue.v
+++ b/Issue.v
@@ -2,26 +2,24 @@
 
 module Issue(
 	input clk,
-	input Nrst,
+	input Nrst,	/* XXX not used yet */
 	
 	input stall,	/* pipeline control */
-	input flush,
+	input flush,	/* XXX not used yet */
 	
 	input inbubble,	/* stage inputs */
 	input [31:0] insn,
 	input [31:0] inpc,
 	input [31:0] cpsr,
 	
-	output reg outbubble,	/* stage outputs */
-	output reg [31:0] outpc
-	/* other */
+	output reg outstall = 0,	/* stage outputs */
+	output reg outbubble = 1,
+	output reg [31:0] outpc = 0,
+	output reg [31:0] outinsn = 0
+	/* XXX other? */
 	);
 	
-	always @(posedge clk)
-	begin
-		outbubble <= inbubble;
-		outpc <= inpc;
-	end
+
 
 `ifdef COPY_PASTA_FODDER
 	/* from page 2 of ARM7TDMIvE2.pdf */
@@ -256,10 +254,47 @@ module Issue(
 		endcase
 	
 	/* Issue logic */
-	/* reg use_cpsr;
-	 * reg [15:0] use_regs;
-	 * reg def_cpsr;
-	 * reg [15:0] def_regs;
-	 */
+`define STAGE_EXECUTE   0
+`define STAGE_MEMORY    1
+/* Once it's hit writeback, it's essentially hit the regfile so you're done. */
+	reg cpsr_inflight [1:0];
+	reg [15:0] regs_inflight [1:0];
+	
+	reg waiting_cpsr;
+	reg waiting_regs;
+	wire waiting = waiting_cpsr | waiting_regs;
+	
+	initial
+	begin
+		cpsr_inflight[0] = 0;
+		cpsr_inflight[1] = 0;
+		regs_inflight[0] = 0;
+		regs_inflight[1] = 0;
+	end
+		
+	always @(*)
+	begin
+		waiting_cpsr = use_cpsr & (cpsr_inflight[0] | cpsr_inflight[1]);
+		waiting_regs = |(use_regs & (regs_inflight[0] | regs_inflight[1]));
+		
+		outstall = waiting && !inbubble;	/* Happens in an always @*, because it is an exception. */
+	end
 	
+	/* Actually do the issue. */
+	always @(posedge clk)
+	begin
+		cpsr_inflight[0] <= cpsr_inflight[1];	/* I'm not sure how well selects work with arrays, and that seems like a dumb thing to get anusulated by. */
+		cpsr_inflight[1] <= (waiting || inbubble || !condition_met) ? 0 : def_cpsr;
+		regs_inflight[0] <= regs_inflight[1];
+		regs_inflight[1] <= (waiting || inbubble || !condition_met) ? 0 : def_regs;
+		
+		if (waiting)
+		begin
+			$display("ISSUE: Stalling instruction %08x because %d/%d", insn, waiting_cpsr, waiting_regs);
+		end
+
+		outbubble <= inbubble | waiting | !condition_met;
+		outpc <= inpc;
+		outinsn <= insn;
+	end
 endmodule