From c5ad62aaed34c2dc4d0816c274407696fcd46412 Mon Sep 17 00:00:00 2001
From: Yehowshua Immanuel <yehowshua@yehowshuaimmanuel.com>
Date: Sun, 23 Mar 2025 08:12:24 -0400
Subject: [PATCH] Greatly simpliflied tag engine to use stack implementation.
 Having trouble guarding on interface argument...

---
 bs/TagEngine.bs | 96 +++++++++++++++++--------------------------------
 bs/Util.bs      |  2 ++
 2 files changed, 35 insertions(+), 63 deletions(-)

diff --git a/bs/TagEngine.bs b/bs/TagEngine.bs
index 456cf28..2900822 100644
--- a/bs/TagEngine.bs
+++ b/bs/TagEngine.bs
@@ -7,55 +7,23 @@ import Util
 
 #define UIntLog2N(n) (UInt (TLog n))
 
-data Tag numTags
-    = Next UIntLog2N(numTags)
-    | Freed
-    | Tail
-    deriving (Bits, Eq, FShow)
-
-data TagPtr numTags
-    = SomeTagPtr UIntLog2N(numTags)
-    | None
-    deriving (Bits, Eq, FShow)
-
 interface (TagEngine :: # -> *) numTags =
     requestTag :: ActionValue UIntLog2N(numTags)
     retireTag  :: UIntLog2N(numTags) -> Action
 
-instance FShow (Reg (Tag numTags)) where
-    fshow value = fshow (readReg value)
-
-initTagNext :: Integer -> Module(Reg (Tag numTags))
-initTagNext i = do
-    t :: Reg (Tag numTags)
-    t <- mkReg (Next (fromInteger i))
-    return t
-
-initTagTail :: Module(Reg (Tag numTags))
-initTagTail = do
-    t :: Reg (Tag numTags)
-    t <- mkReg Tail
-    return t
-
-initTagVec :: Module(Vector numTags (Reg (Tag numTags)))
-initTagVec =
-    let
-        lastIdx :: Integer = (fromInteger |> valueOf numTags) - 1
-        initByIdx currIdx =
-            if (currIdx < lastIdx)
-                then initTagNext (currIdx + 1)
-                else initTagTail
-    in
-        mapM initByIdx genVector
-
 mkTagEngine :: Module (TagEngine numTags)
 mkTagEngine =
     do
-        tagVec :: Vector numTags (Reg (Tag numTags))
-        tagVec <- initTagVec
+        let reifiedNumTags = fromInteger |> valueOf numTags
 
-        head :: Reg(TagPtr(numTags)) <- mkReg(SomeTagPtr(0))
-        tail :: Reg(TagPtr(numTags)) <- mkReg(SomeTagPtr(lastIdx))
+        freeStackVec :: Vector numTags (Reg UIntLog2N(numTags))
+        freeStackVec <- mapM (\i -> mkReg |> fromInteger i) genVector
+
+        inUseVec :: Vector numTags (Reg Bool)
+        inUseVec <- replicateM |> mkReg False
+
+        stackPtr :: (Reg (Maybe(UIntLog2N(numTags))))
+        stackPtr <- mkReg |> Just |> reifiedNumTags - 1
 
         debugOnce <- mkReg True
 
@@ -63,35 +31,37 @@ mkTagEngine =
             rules
                 "display": when (debugOnce == True) ==>
                     do
-                        $display (fshow tagVec)
+                        $display "freeStackVec : " (fshow |> readVReg freeStackVec)
+                        $display "inUseVec : " (fshow |> readVReg inUseVec)
+                        $display "stackPtr : " (fshow stackPtr)
                         debugOnce := False
 
         counter <- mkReg(0 :: UIntLog2N(numTags))
         return $
           interface TagEngine
+
             requestTag :: ActionValue UIntLog2N(numTags)
             requestTag =
                 do
-                    let currHeadPtr :: UIntLog2N(numTags) =
-                            case head of
-                                SomeTagPtr ptr -> ptr
-                                -- we technically will never hit this arm
-                                -- due to when guard `SomeTagPtr ptr <- head`
-                                None -> 0
-                    let currHead :: (Reg (Tag numTags)) = (select tagVec currHeadPtr)
-                    let nextHeadPtr :: UIntLog2N(numTags) =
-                            case currHead of
-                                Next ptr -> ptr
-                                -- TODO : handle tail correctly
-                                Tail -> 0
-                    currHead := Freed
-                    head := SomeTagPtr(nextHeadPtr)
-                    return nextHeadPtr
+                    stackPtr := 
+                        if sampledStackPtr == 0
+                            then Nothing
+                            else Just |> sampledStackPtr - 1
+                    (select inUseVec sampledStackPtr) := True
+                    return |> readReg (select freeStackVec sampledStackPtr)
                 when
-                    SomeTagPtr ptr <- head
+                    Just sampledStackPtr <- stackPtr
+
             retireTag :: UIntLog2N(numTags) -> Action
-            retireTag tag = do
-                -- placeholder
-                counter := 0
-    where
-        lastIdx :: UIntLog2N(numTags) = (fromInteger |> valueOf numTags) - 1
+            retireTag tag = 
+                do
+                    let nextStackPtrUint = 
+                            case stackPtr of
+                                Nothing -> 0
+                                Just n -> n + 1
+                    (select inUseVec tag) := False
+                    (select freeStackVec nextStackPtrUint) := tag
+                    stackPtr := Just nextStackPtrUint
+                -- when
+                --     tag < (reifiedNumTags - 1),
+                --     readReg (select inUseVec tag)
diff --git a/bs/Util.bs b/bs/Util.bs
index 49ac04e..b2ea119 100644
--- a/bs/Util.bs
+++ b/bs/Util.bs
@@ -1,5 +1,7 @@
 package Util((|>), simulate_for) where
 
+infixr 0 |>
+
 (|>) :: (a -> b) -> a -> b
 f |> x = f x;