handled tag engine edge case

bs/TagEngine.bs

@@ -7,6 +7,7 @@ import Vector
 import Util
 import FIFO
 import FIFOF
+import SpecialFIFOs
 
 #define UIntLog2N(n) (UInt (TLog n))
 
@@ -37,8 +38,14 @@ mkTagEngine =
         initialTagDistributor :: (Reg (Maybe UIntLog2N(numTags)))
         initialTagDistributor <- mkReg |> Just |> reifiedNumTags - 1
 
-        retireTag ::  Wire UIntLog2N(numTags)
+        validatedTagToRetire ::  FIFO UIntLog2N(numTags)
-        retireTag <- mkWire
+        validatedTagToRetire <- mkBypassFIFO
+
+        updateUsageRetireTag ::  RWire UIntLog2N(numTags)
+        updateUsageRetireTag <- mkRWire
+
+        updateUsageRequestTag ::  RWire UIntLog2N(numTags)
+        updateUsageRequestTag <- mkRWire
 
         tagFIFO ::  FIFOF UIntLog2N(numTags)
         tagFIFO <- mkSizedFIFOF reifiedNumTags
@@ -52,11 +59,38 @@ mkTagEngine =
                         $display "tagUsageTracker : " (fshow |> readVReg tagUsageTracker)
                         debugOnce := False
 
+                "update_usage_just_retire": when
+                                        Just tag <- updateUsageRetireTag.wget,
+                                        Nothing  <- updateUsageRequestTag.wget ==>
+                    do
+                        $display $time " tagUsageTracker after update retire: " (fshow |> readVReg tagUsageTracker)
+                        (select tagUsageTracker tag) := False
+
+                "update_usage_just_request": when
+                                        Nothing <- updateUsageRetireTag.wget,
+                                        Just tag  <- updateUsageRequestTag.wget ==>
+                    do
+                        $display $time " tagUsageTracker after update request: " (fshow |> readVReg tagUsageTracker)
+                        (select tagUsageTracker tag) := True
+
+                "update_usage_request_and_retire": when
+                                        Just retireTag  <- updateUsageRetireTag.wget,
+                                        Just requestTag <- updateUsageRequestTag.wget ==>
+                    do
+                        $display $time " tagUsageTracker after update request and retire: " (fshow |> readVReg tagUsageTracker)
+                        let
+                            tagUsageTrackerInner = readVReg tagUsageTracker
+                            tagUsageTracker'  = update tagUsageTrackerInner requestTag True
+                            tagUsageTracker'' = update tagUsageTracker' retireTag False
+                        writeVReg tagUsageTracker tagUsageTracker''
+
                 "retire_tags": when True ==>
                     do
-                        $display "firing retire_tags" (fshow retireTag)
+                        let tagToRetire = validatedTagToRetire.first
-                        tagFIFO.enq retireTag
+                        $display "firing retire_tags" (fshow tagToRetire)
-                        (select tagUsageTracker retireTag) := False
+                        validatedTagToRetire.deq
+                        tagFIFO.enq tagToRetire
+                        updateUsageRetireTag.wset tagToRetire
 
         return $
           interface TagEngine
@@ -67,15 +101,16 @@ mkTagEngine =
                     case initialTagDistributor of
                         Just 0 -> do
                             initialTagDistributor := Nothing
-                            (select tagUsageTracker 0) := True
+                            updateUsageRequestTag.wset 0
                             return 0
                         Just tag -> do
                             initialTagDistributor := Just |> tag - 1
-                            (select tagUsageTracker tag) := True
+                            updateUsageRequestTag.wset tag
                             return tag
                         Nothing -> do
                             let tag = tagFIFO.first
                             tagFIFO.deq
+                            updateUsageRequestTag.wset tag
                             return tag
 
             -- `retireTag` isn't guarded on tag validity(this would break Bluespec's safety model)
@@ -90,6 +125,6 @@ mkTagEngine =
                         tagInUse = readReg (select tagUsageTracker tag)
                     if (tagValid && tagInUse)
                         then do
-                            retireTag := tag
+                            validatedTagToRetire.enq tag
                         else do
                             action {}

bs/Tests/TagEngineTester.bs

@@ -6,7 +6,6 @@ import ActionSeq
 mkTagEngineTester :: Module Empty
 mkTagEngineTester = do
   tagEngine :: TagEngine 5 <- mkTagEngine
-  count            :: Reg (UInt 32) <- mkReg 0;
   runOnce :: Reg Bool <- mkReg False
 
   s :: ActionSeq
@@ -16,13 +15,13 @@ mkTagEngineTester = do
       requestTagAction =
         do
           tag <- tagEngine.requestTag
-          $display "got tag : " (fshow tag)
+          $display $time " got tag : " (fshow tag)
 
       retireTagAction :: UInt 3 -> Action
       retireTagAction tag =
         do
           res <- tagEngine.retireTag tag
-          $display "retiring tag : " (fshow tag) " " (fshow res)
+          $display $time " retiring tag : " (fshow tag) " " (fshow res)
           action {}
 
     in
@@ -55,10 +54,10 @@ mkTagEngineTester = do
 
   addRules $
     rules
-      "counter": when True ==>
+      -- "counter": when True ==>
-        do
+      --   do
-          count := count + 1
+      --     count := count + 1
-          $display "count : " (fshow count)
+      --     $display "count : " (fshow count)
       "testIncrement": when (runOnce == False) ==>
         do
           s.start