Issue: Add logic to defer a flush if need be (i.e., we're stalled at the time and...

[firearm.git] / Issue.v

diff --git a/Issue.v b/Issue.v
index c3e579155bf09c9019a42d4df130291c9c2cf01e..7815a0813d30faa74013db39911d5e5d448e6d65 100644 (file)
--- a/Issue.v
+++ b/Issue.v
@@ -167,7 +167,7 @@ module Issue(
                                                (idxbit(rs) | idxbit(rm)) :
                                                (idxbit(rm)))) |
                                (((alu_opc != `ALU_MOV) && (alu_opc != `ALU_MVN)) ? idxbit(rn) : 0);
-                       def_cpsr = insn[20] /* S */ | alu_is_logical(alu_opc);
+                       def_cpsr = insn[20] /* S */;
                        def_regs = alu_flags_only(alu_opc) ? 0 : idxbit(rd);
                end
                `DECODE_LDRSTR_UNDEFINED:       /* Undefined. I hate ARM */
@@ -282,16 +282,31 @@ module Issue(
                waiting_cpsr = use_cpsr & (cpsr_inflight[0] | cpsr_inflight[1]);
                waiting_regs = |(use_regs & (regs_inflight[0] | regs_inflight[1]));
                
-               outstall = (waiting && !inbubble) || stall;     /* Happens in an always @*, because it is an exception. */
+               outstall = (waiting && !inbubble && !flush) || stall;   /* Happens in an always @*, because it is an exception. */
        end
+
+       reg delayedflush = 0;
+       always @(posedge clk)
+               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)
        begin
                if (waiting)
                        $display("ISSUE: Stalling instruction %08x because %d/%d", insn, waiting_cpsr, waiting_regs);
-       
-               if (!stall)
+
+               if((flush || delayedflush) && !outstall)
+               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)
                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;