82 lines
3 KiB
Haskell
82 lines
3 KiB
Haskell
package TagEngine(
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TagEngine(..),
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Util.BasicResult(..),
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mkTagEngine) where
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import Vector
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import Util
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#define UIntLog2N(n) (UInt (TLog n))
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interface (TagEngine :: # -> *) numTags =
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requestTag :: ActionValue UIntLog2N(numTags)
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retireTag :: UIntLog2N(numTags) -> ActionValue BasicResult
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-- The tag engine returns a tag that is unique for the duration of
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-- the lifetime of the tag. Useful when you need to tag transactions
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-- on a bus for example.
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-- This implementation is stack 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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freeStackVec :: Vector numTags (Reg UIntLog2N(numTags))
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freeStackVec <- mapM (\i -> mkReg |> fromInteger i) genVector
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inUseVec :: Vector numTags (Reg Bool)
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inUseVec <- replicateM |> mkReg False
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stackPtr :: (Reg (Maybe(UIntLog2N(numTags))))
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stackPtr <- mkReg |> Just |> reifiedNumTags - 1
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debugOnce <- mkReg True
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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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$display "freeStackVec : " (fshow |> readVReg freeStackVec)
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$display "inUseVec : " (fshow |> readVReg inUseVec)
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$display "stackPtr : " (fshow stackPtr)
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debugOnce := False
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counter <- mkReg(0 :: UIntLog2N(numTags))
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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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stackPtr :=
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if sampledStackPtr == 0
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then Nothing
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else Just |> sampledStackPtr - 1
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(select inUseVec sampledStackPtr) := True
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return |> readReg (select freeStackVec sampledStackPtr)
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when
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Just sampledStackPtr <- stackPtr
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-- retireTag isn't guarded so its up to external module to only attempt to
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-- retire valid tags... At any rate, we can notify the requestor of failures
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-- to retire tags - although the requestor can merely ignore this
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-- notification.
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retireTag :: UIntLog2N(numTags) -> ActionValue BasicResult
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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 inUseVec tag)
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nextStackPtrUint =
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case stackPtr of
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Nothing -> 0
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Just n -> n + 1
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if (tagValid && tagInUse)
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then do
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(select inUseVec tag) := False
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(select freeStackVec nextStackPtrUint) := tag
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stackPtr := Just nextStackPtrUint
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return Success
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else do
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return Failure
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