notable refactor with grok
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bs/TagEngine.bs
131
bs/TagEngine.bs
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@ -20,111 +20,84 @@ interface (TagEngine :: # -> *) numTags =
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-- on a bus for example.
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-- This implementation is FIFO based.
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mkTagEngine :: Module (TagEngine numTags)
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mkTagEngine =
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do
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let reifiedNumTags = fromInteger |> valueOf numTags
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mkTagEngine = do
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-- Constants
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let maxTagCount = fromInteger (valueOf numTags)
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-- we really only use tagUsageTracker after emptying out our
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-- `initialTagDistributor` buffer
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tagUsageTracker :: Vector numTags (Reg Bool)
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tagUsageTracker <- replicateM |> mkReg False
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-- State
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tagUsage :: Vector numTags (Reg Bool) <- replicateM (mkReg False) -- Tracks which tags are in use
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initialTagCounter <- mkReg (Just (maxTagCount - 1)) -- Distributes initial tags
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retireQueue <- mkBypassFIFO -- Queue for tags being retired
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freeTagQueue <- mkSizedFIFOF maxTagCount -- Queue of available tags
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-- Since Bluespec doesn't allow us to initialize FIFOs with values at
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-- reset, we can pretend as if the buffer within our tagFIFO is populated
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-- with sequentially incrementing values(starting from 0) on reset
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-- by having our tag engine effectively return the value of a decrementing
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-- counter initialized to (numTags - 1) for the first n tag requests made
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-- to TagEngine where `n := numTags`.
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initialTagDistributor :: (Reg (Maybe UIntLog2N(numTags)))
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initialTagDistributor <- mkReg |> Just |> reifiedNumTags - 1
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validatedTagToRetire :: FIFO UIntLog2N(numTags)
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validatedTagToRetire <- mkBypassFIFO
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updateUsageRetireTag :: RWire UIntLog2N(numTags)
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updateUsageRetireTag <- mkRWire
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updateUsageRequestTag :: RWire UIntLog2N(numTags)
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updateUsageRequestTag <- mkRWire
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tagFIFO :: FIFOF UIntLog2N(numTags)
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tagFIFO <- mkSizedFIFOF reifiedNumTags
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-- Signals
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retireSignal <- mkRWire -- Signals a tag retirement
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requestSignal <- mkRWire -- Signals a tag request
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-- Debug
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debugOnce <- mkReg True
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-- Rules
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addRules $
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rules
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"display": when (debugOnce == True) ==>
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do
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$display "tagUsageTracker : " (fshow |> readVReg tagUsageTracker)
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"debug_initial_state": when debugOnce ==> do
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$display "tagUsage: " (fshow (readVReg tagUsage))
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debugOnce := False
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"update_usage_just_retire": when
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Just tag <- updateUsageRetireTag.wget,
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Nothing <- updateUsageRequestTag.wget ==>
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do
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$display $time " tagUsageTracker after update retire: " (fshow |> readVReg tagUsageTracker)
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(select tagUsageTracker tag) := False
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"retire_tag": when True ==> do
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let tag = retireQueue.first
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$display "Retiring tag: " (fshow tag)
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retireQueue.deq
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freeTagQueue.enq tag
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retireSignal.wset tag
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"update_usage_just_request": when
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Nothing <- updateUsageRetireTag.wget,
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Just tag <- updateUsageRequestTag.wget ==>
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do
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$display $time " tagUsageTracker after update request: " (fshow |> readVReg tagUsageTracker)
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(select tagUsageTracker tag) := True
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"update_usage_request_and_retire": when
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Just retireTag <- updateUsageRetireTag.wget,
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Just requestTag <- updateUsageRequestTag.wget ==>
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do
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$display $time " tagUsageTracker after update request and retire: " (fshow |> readVReg tagUsageTracker)
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let
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tagUsageTrackerInner = readVReg tagUsageTracker
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tagUsageTracker' = update tagUsageTrackerInner requestTag True
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tagUsageTracker'' = update tagUsageTracker' retireTag False
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writeVReg tagUsageTracker tagUsageTracker''
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"retire_tags": when True ==>
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do
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let tagToRetire = validatedTagToRetire.first
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$display "firing retire_tags" (fshow tagToRetire)
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validatedTagToRetire.deq
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tagFIFO.enq tagToRetire
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updateUsageRetireTag.wset tagToRetire
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-- Combined update rules (simplified below)
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"update_usage": when True ==> do
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let mRetireTag = retireSignal.wget
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mRequestTag = requestSignal.wget
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case (mRetireTag, mRequestTag) of
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(Just retireTag, Just requestTag) -> do
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let usage = readVReg tagUsage
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usage' = update usage requestTag True
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usage'' = update usage' retireTag False
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writeVReg tagUsage usage''
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$display $time " Updated usage (request + retire): " (fshow |> readVReg tagUsage)
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(Just retireTag, Nothing) -> do
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(select tagUsage retireTag) := False
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$display $time " Updated usage (retire): " (fshow (readVReg tagUsage))
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(Nothing, Just requestTag) -> do
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(select tagUsage requestTag) := True
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$display $time " Updated usage (request): " (fshow (readVReg tagUsage))
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(Nothing, Nothing) -> action {}
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-- Interface
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return $
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interface TagEngine
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requestTag :: ActionValue UIntLog2N(numTags)
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requestTag =
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do
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case initialTagDistributor of
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requestTag = do
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case initialTagCounter of
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Just 0 -> do
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initialTagDistributor := Nothing
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updateUsageRequestTag.wset 0
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initialTagCounter := Nothing
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requestSignal.wset 0
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return 0
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Just tag -> do
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initialTagDistributor := Just |> tag - 1
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updateUsageRequestTag.wset tag
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initialTagCounter := Just (tag - 1)
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requestSignal.wset tag
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return tag
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Nothing -> do
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let tag = tagFIFO.first
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tagFIFO.deq
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updateUsageRequestTag.wset tag
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let tag = freeTagQueue.first
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freeTagQueue.deq
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requestSignal.wset tag
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return tag
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-- `retireTag` isn't guarded on tag validity(this would break Bluespec's safety model)
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-- so it is advisable that the caller of `retireTag` only attempt to retire valid tags.
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-- Internally, the tagEngine will keep a correct and consistent state since TagEngine
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-- validates tags before attempting to retire them.
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retireTag :: UIntLog2N(numTags) -> Action
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retireTag tag =
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do
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let
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tagValid = tag < reifiedNumTags
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tagInUse = readReg (select tagUsageTracker tag)
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tagValid = tag < maxTagCount
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tagInUse = readReg (select tagUsage tag)
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if (tagValid && tagInUse)
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then do
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validatedTagToRetire.enq tag
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retireQueue.enq tag
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else do
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action {}
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