Fetch: Rewrite for the 317235784th time, this time based off a block diagram on paper...

[firearm.git] / Issue.v

diff --git a/Issue.v b/Issue.v
index 7b281a30016d8dc0254a3207678ae3b895a86a04..07c709d7ae4aa9335f21122ac12e9dc3f2f47a09 100644 (file)
--- a/Issue.v
+++ b/Issue.v
@@ -12,7 +12,7 @@ module Issue(
        input [31:0] inpc,
        input [31:0] cpsr,
        
-       output reg outstall = 0,        /* stage outputs */
+       output wire outstall,   /* stage outputs */
        output reg outbubble = 1,
        output reg [31:0] outpc = 0,
        output reg [31:0] outinsn = 0
@@ -180,7 +180,7 @@ module Issue(
                `DECODE_LDRSTR:
                begin
                        use_cpsr = `COND_MATTERS(cond);
-                       use_regs = idxbit(rn) | (insn[20] /* L */ ? 0 : idxbit(rd));
+                       use_regs = idxbit(rn) | (insn[25] /* I */ ? idxbit(rm) : 0) | (insn[20] /* L */ ? 0 : idxbit(rd));
                        def_cpsr = 0;
                        def_regs = insn[20] /* L */ ? idxbit(rd) : 0;
                end
@@ -196,7 +196,7 @@ module Issue(
                        use_cpsr = `COND_MATTERS(cond);
                        use_regs = 0;
                        def_cpsr = 0;
-                       def_regs = 0;
+                       def_regs = insn[24] /* L */ ? (16'b1 << 14) : 0;
                end
                `DECODE_LDCSTC: /* Coprocessor data transfer */
                begin
@@ -265,10 +265,6 @@ module Issue(
        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;
@@ -276,37 +272,41 @@ module Issue(
                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) || stall) && !flush; /* Happens in an always @*, because it is an exception. */
-       end
        
+       wire waiting_cpsr = use_cpsr & (cpsr_inflight[0] | cpsr_inflight[1]);
+       wire waiting_regs = |(use_regs & (regs_inflight[0] | regs_inflight[1]));
+       wire waiting = waiting_cpsr | waiting_regs;
+       assign outstall = (waiting && !inbubble && !flush) || stall;
+
+       reg delayedflush = 0;
+       always @(posedge clk/* or negedge Nrst*/)
+               if (!Nrst)
+                       delayedflush <= 0;
+               else if (flush && outstall /* halp! I can't do it now, maybe later? */)
+                       delayedflush <= 1;
+               else if (!outstall /* anything has been handled this time around */)
+                       delayedflush <= 0;
+
        /* Actually do the issue. */
-       always @(posedge clk)
+       always @(posedge clk or negedge Nrst)
        begin
                if (waiting)
                        $display("ISSUE: Stalling instruction %08x because %d/%d", insn, waiting_cpsr, waiting_regs);
 
-               if(flush)
-               begin
-                       cpsr_inflight[0] = 1'b0;
-                       cpsr_inflight[1] = 1'b0;
-                       regs_inflight[0] = 16'b0;
-                       regs_inflight[1] = 16'b0;
-                       outbubble <= 1'b1;
-               end
-               else if (!stall)
+               if (!Nrst) begin
+                       cpsr_inflight[0] <= 0;
+                       cpsr_inflight[1] <= 0;
+                       regs_inflight[0] <= 0;
+                       regs_inflight[1] <= 0;
+                       outbubble <= 1;
+               end else if (!stall)
                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;
                        
-                       outbubble <= inbubble | waiting | !condition_met;
+                       outbubble <= inbubble | waiting | !condition_met | flush | delayedflush;
                        outpc <= inpc;
                        outinsn <= insn;
                end