Execute: Branches allow somebody else to take precedence by not branching if outstall...

[firearm.git] / Issue.v

diff --git a/Issue.v b/Issue.v
index 8fba3088d04d4521a9fe099d336ce84b93d0df5d..1b9868da1a2b7b0236b58dc2382960961805c89f 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 */
@@ -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
@@ -282,24 +282,40 @@ 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;        /* 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
-               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;
+               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;
+                       regs_inflight[0] <= regs_inflight[1];
+                       regs_inflight[1] <= (waiting || inbubble || !condition_met) ? 0 : def_regs;
+                       
+                       outbubble <= inbubble | waiting | !condition_met;
+                       outpc <= inpc;
+                       outinsn <= insn;
+               end
        end
 endmodule