Issue: Add logic to defer a flush if need be (i.e., we're stalled at the time and...
authorJoshua Wise <joshua@rebirth.joshuawise.com>
Wed, 14 Jan 2009 07:13:25 +0000 (02:13 -0500)
committerJoshua Wise <joshua@rebirth.joshuawise.com>
Wed, 14 Jan 2009 07:13:25 +0000 (02:13 -0500)
Issue.v

diff --git a/Issue.v b/Issue.v
index 7b281a3..7815a08 100644 (file)
--- a/Issue.v
+++ b/Issue.v
@@ -282,8 +282,15 @@ 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) && !flush; /* 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)
@@ -291,7 +298,7 @@ module Issue(
                if (waiting)
                        $display("ISSUE: Stalling instruction %08x because %d/%d", insn, waiting_cpsr, waiting_regs);
 
-               if(flush)
+               if((flush || delayedflush) && !outstall)
                begin
                        cpsr_inflight[0] = 1'b0;
                        cpsr_inflight[1] = 1'b0;
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