content: {-|
  Copyright  :  (C) 2013-2016, University of Twente,
                    2016-2019, Myrtle Software Ltd,
                    2017     , Google Inc.,
                    2021-2022, QBayLogic B.V.
  License    :  BSD2 (see the file LICENSE)
  Maintainer :  QBayLogic B.V. <devops@qbaylogic.com>
  
  Block RAM primitives
  
  = Using RAMs #usingrams#
  
  We will show a rather elaborate example on how you can, and why you might want
  to use 'blockRam's. We will build a \"small\" CPU + Memory + Program ROM where
  we will slowly evolve to using 'blockRam's. Note that the code is /not/ meant as
  a de-facto standard on how to do CPU design in Clash.
  
  We start with the definition of the Instructions, Register names and machine
  codes:
  
  @
  {\-\# LANGUAGE RecordWildCards, TupleSections, DeriveAnyClass \#-\}
  
  module CPU where
  
  import Clash.Prelude
  
  type InstrAddr = Unsigned 8
  type MemAddr   = Unsigned 5
  type Value     = Signed 8
  
  data Instruction
    = Compute Operator Reg Reg Reg
    | Branch Reg Value
    | Jump Value
    | Load MemAddr Reg
    | Store Reg MemAddr
    | Nop
    deriving (Eq, Show, Generic, NFDataX)
  
  data Reg
    = Zero
    | PC
    | RegA
    | RegB
    | RegC
    | RegD
    | RegE
    deriving (Eq, Show, Enum, Generic, NFDataX)
  
  data Operator = Add | Sub | Incr | Imm | CmpGt
    deriving (Eq, Show, Generic, NFDataX)
  
  data MachCode
    = MachCode
    { inputX  :: Reg
    , inputY  :: Reg
    , result  :: Reg
    , aluCode :: Operator
    , ldReg   :: Reg
    , rdAddr  :: MemAddr
    , wrAddrM :: Maybe MemAddr
    , jmpM    :: Maybe Value
    }
  
  nullCode =
    MachCode
      { inputX = Zero
      , inputY = Zero
      , result = Zero
      , aluCode = Imm
      , ldReg = Zero
      , rdAddr = 0
      , wrAddrM = Nothing
      , jmpM = Nothing
      }
  @
  
  Next we define the CPU and its ALU:
  
  @
  cpu
    :: Vec 7 Value          -- ^ Register bank
    -> (Value,Instruction)  -- ^ (Memory output, Current instruction)
    -> ( Vec 7 Value
       , (MemAddr, Maybe (MemAddr,Value), InstrAddr)
       )
  cpu regbank (memOut, instr) =
    (regbank', (rdAddr, (,aluOut) 'Prelude.<$>' wrAddrM, bitCoerce ipntr))
   where
    -- Current instruction pointer
    ipntr = regbank 'Clash.Sized.Vector.!!' PC
  
    -- Decoder
    (MachCode {..}) = case instr of
      Compute op rx ry res -> nullCode {inputX=rx,inputY=ry,result=res,aluCode=op}
      Branch cr a          -> nullCode {inputX=cr,jmpM=Just a}
      Jump a               -> nullCode {aluCode=Incr,jmpM=Just a}
      Load a r             -> nullCode {ldReg=r,rdAddr=a}
      Store r a            -> nullCode {inputX=r,wrAddrM=Just a}
      Nop                  -> nullCode
  
    -- ALU
    regX   = regbank 'Clash.Sized.Vector.!!' inputX
    regY   = regbank 'Clash.Sized.Vector.!!' inputY
    aluOut = alu aluCode regX regY
  
    -- next instruction
    nextPC =
      case jmpM of
        Just a | aluOut /= 0 -> ipntr + a
        _                    -> ipntr + 1
  
    -- update registers
    regbank' = 'Clash.Sized.Vector.replace' Zero   0
             $ 'Clash.Sized.Vector.replace' PC     nextPC
             $ 'Clash.Sized.Vector.replace' result aluOut
             $ 'Clash.Sized.Vector.replace' ldReg  memOut
             $ regbank
  
  alu Add   x y = x + y
  alu Sub   x y = x - y
  alu Incr  x _ = x + 1
  alu Imm   x _ = x
  alu CmpGt x y = if x > y then 1 else 0
  @
  
  We initially create a memory out of simple registers:
  
  @
  dataMem
    :: HiddenClockResetEnable dom
    => Signal dom MemAddr
    -- ^ Read address
    -> Signal dom (Maybe (MemAddr,Value))
    -- ^ (write address, data in)
    -> Signal dom Value
    -- ^ data out
  dataMem rd wrM =
    'Clash.Prelude.Mealy.mealy' dataMemT ('Clash.Sized.Vector.replicate' d32 0) (bundle (rd,wrM))
   where
    dataMemT mem (rd,wrM) = (mem',dout)
      where
        dout = mem 'Clash.Sized.Vector.!!' rd
        mem' =
          case wrM of
            Just (wr,din) -> 'Clash.Sized.Vector.replace' wr din mem
            _             -> mem
  @
  
  And then connect everything:
  
  @
  system
    :: ( KnownNat n
       , HiddenClockResetEnable dom
       )
    => Vec n Instruction
    -> Signal dom Value
  system instrs = memOut
   where
    memOut = dataMem rdAddr dout
    (rdAddr, dout, ipntr) = 'Clash.Prelude.Mealy.mealyB' cpu ('Clash.Sized.Vector.replicate' d7 0) (memOut,instr)
    instr  = 'Clash.Prelude.ROM.asyncRom' instrs 'Prelude.<$>' ipntr
  @
  
  Create a simple program that calculates the GCD of 4 and 6:
  
  @
  -- Compute GCD of 4 and 6
  prog = -- 0 := 4
         Compute Incr Zero RegA RegA :>
         replicate d3 (Compute Incr RegA Zero RegA) ++
         Store RegA 0 :>
         -- 1 := 6
         Compute Incr Zero RegA RegA :>
         replicate d5 (Compute Incr RegA Zero RegA) ++
         Store RegA 1 :>
         -- A := 4
         Load 0 RegA :>
         -- B := 6
         Load 1 RegB :>
         -- start
         Compute CmpGt RegA RegB RegC :>
         Branch RegC 4 :>
         Compute CmpGt RegB RegA RegC :>
         Branch RegC 4 :>
         Jump 5 :>
         -- (a > b)
         Compute Sub RegA RegB RegA :>
         Jump (-6) :>
         -- (b > a)
         Compute Sub RegB RegA RegB :>
         Jump (-8) :>
         -- end
         Store RegA 2 :>
         Load 2 RegC :>
         Nil
  @
  
  And test our system:
  
  @
  >>> sampleN @System 32 (system prog)
  [0,0,0,0,0,0,4,4,4,4,4,4,4,4,6,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,2]
  
  @
  
  to see that our system indeed calculates that the GCD of 6 and 4 is 2.
  
  === Improvement 1: using @asyncRam@
  
  As you can see, it's fairly straightforward to build a memory using registers
  and read ('Clash.Sized.Vector.!!') and write ('Clash.Sized.Vector.replace')
  logic. This might however not result in the most efficient hardware structure,
  especially when building an ASIC.
  
  Instead it is preferable to use the 'Clash.Prelude.RAM.asyncRam' function which
  has the potential to be translated to a more efficient structure:
  
  @
  system2
    :: ( KnownNat n
       , HiddenClockResetEnable dom  )
    => Vec n Instruction
    -> Signal dom Value
  system2 instrs = memOut
   where
    memOut = 'Clash.Prelude.RAM.asyncRam' d32 rdAddr dout
    (rdAddr,dout,ipntr) = 'Clash.Prelude.mealyB' cpu ('Clash.Sized.Vector.replicate' d7 0) (memOut,instr)
    instr  = 'Clash.Prelude.ROM.asyncRom' instrs 'Prelude.<$>' ipntr
  @
  
  Again, we can simulate our system and see that it works. This time however,
  we need to disregard the first few output samples, because the initial content of an
  'Clash.Prelude.RAM.asyncRam' is /undefined/, and consequently, the first few
  output samples are also /undefined/. We use the utility function
  'Clash.XException.printX' to conveniently filter out the undefinedness and
  replace it with the string @\"undefined\"@ in the first few leading outputs.
  
  @
  >>> printX $ sampleN @System 32 (system2 prog)
  [undefined,undefined,undefined,undefined,undefined,undefined,4,4,4,4,4,4,4,4,6,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,2]
  
  @
  
  === Improvement 2: using @blockRam@
  
  Finally we get to using 'blockRam'. On FPGAs, 'Clash.Prelude.RAM.asyncRam' will
  be implemented in terms of LUTs, and therefore take up logic resources. FPGAs
  also have large(r) memory structures called /block RAMs/, which are preferred,
  especially as the memories we need for our application get bigger. The
  'blockRam' function will be translated to such a /block RAM/.
  
  One important aspect of block RAMs is that they have a /synchronous/ read port,
  meaning that, unlike the behavior of 'Clash.Prelude.RAM.asyncRam', given a read
  address @r@ at time @t@, the value @v@ in the RAM at address @r@ is only
  available at time @t+1@.
  
  For us that means we need to change the design of our CPU. Right now, upon a
  load instruction we generate a read address for the memory, and the value at
  that read address is immediately available to be put in the register bank.
  Because we will be using a block RAM, the value is delayed until the next cycle.
  Thus, we will need to also delay the register address to which the memory
  address is loaded:
  
  @
  cpu2
    :: (Vec 7 Value,Reg)    -- ^ (Register bank, Load reg addr)
    -> (Value,Instruction)  -- ^ (Memory output, Current instruction)
    -> ( (Vec 7 Value, Reg)
       , (MemAddr, Maybe (MemAddr,Value), InstrAddr)
       )
  cpu2 (regbank,ldRegD) (memOut,instr) =
    ((regbank', ldRegD'), (rdAddr, (,aluOut) 'Prelude.<$>' wrAddrM, bitCoerce ipntr))
   where
    -- Current instruction pointer
    ipntr = regbank 'Clash.Sized.Vector.!!' PC
  
    -- Decoder
    (MachCode {..}) = case instr of
      Compute op rx ry res -> nullCode {inputX=rx,inputY=ry,result=res,aluCode=op}
      Branch cr a          -> nullCode {inputX=cr,jmpM=Just a}
      Jump a               -> nullCode {aluCode=Incr,jmpM=Just a}
      Load a r             -> nullCode {ldReg=r,rdAddr=a}
      Store r a            -> nullCode {inputX=r,wrAddrM=Just a}
      Nop                  -> nullCode
  
    -- ALU
    regX   = regbank 'Clash.Sized.Vector.!!' inputX
    regY   = regbank 'Clash.Sized.Vector.!!' inputY
    aluOut = alu aluCode regX regY
  
    -- next instruction
    nextPC =
      case jmpM of
        Just a | aluOut /= 0 -> ipntr + a
        _                    -> ipntr + 1
  
    -- update registers
    ldRegD'  = ldReg  -- Delay the ldReg by 1 cycle
    regbank' = 'Clash.Sized.Vector.replace' Zero   0
             $ 'Clash.Sized.Vector.replace' PC     nextPC
             $ 'Clash.Sized.Vector.replace' result aluOut
             $ 'Clash.Sized.Vector.replace' ldRegD memOut
             $ regbank
  @
  
  We can now finally instantiate our system with a 'blockRam':
  
  @
  system3
    :: (KnownNat n
       , HiddenClockResetEnable dom  )
    => Vec n Instruction
    -> Signal dom Value
  system3 instrs = memOut
   where
    memOut = 'blockRam' (replicate d32 0) rdAddr dout
    (rdAddr,dout,ipntr) = 'Clash.Prelude.mealyB' cpu2 (('Clash.Sized.Vector.replicate' d7 0),Zero) (memOut,instr)
    instr  = 'Clash.Prelude.ROM.asyncRom' instrs 'Prelude.<$>' ipntr
  @
  
  We are, however, not done. We will also need to update our program. The reason
  being that values that we try to load in our registers won't be loaded into the
  register until the next cycle. This is a problem when the next instruction
  immediately depends on this memory value. In our case, this was only the case
  when we loaded the value @6@, which was stored at address @1@, into @RegB@.
  Our updated program is thus:
  
  @
  prog2 = -- 0 := 4
         Compute Incr Zero RegA RegA :>
         replicate d3 (Compute Incr RegA Zero RegA) ++
         Store RegA 0 :>
         -- 1 := 6
         Compute Incr Zero RegA RegA :>
         replicate d5 (Compute Incr RegA Zero RegA) ++
         Store RegA 1 :>
         -- A := 4
         Load 0 RegA :>
         -- B := 6
         Load 1 RegB :>
         Nop :> -- Extra NOP
         -- start
         Compute CmpGt RegA RegB RegC :>
         Branch RegC 4 :>
         Compute CmpGt RegB RegA RegC :>
         Branch RegC 4 :>
         Jump 5 :>
         -- (a > b)
         Compute Sub RegA RegB RegA :>
         Jump (-6) :>
         -- (b > a)
         Compute Sub RegB RegA RegB :>
         Jump (-8) :>
         -- end
         Store RegA 2 :>
         Load 2 RegC :>
         Nil
  @
  
  When we simulate our system we see that it works. This time again,
  we need to disregard the first sample, because the initial output of a
  'blockRam' is /undefined/. We use the utility function 'Clash.XException.printX'
  to conveniently filter out the undefinedness and replace it with the string @\"undefined\"@.
  
  @
  >>> printX $ sampleN @System 34 (system3 prog2)
  [undefined,0,0,0,0,0,0,4,4,4,4,4,4,4,4,6,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,2]
  
  @
  
  This concludes the short introduction to using 'blockRam'.
  
  -}
  
  {-# LANGUAGE CPP #-}
  {-# LANGUAGE FlexibleContexts #-}
  {-# LANGUAGE NoGeneralizedNewtypeDeriving #-}
  {-# LANGUAGE NoImplicitPrelude #-}
  {-# LANGUAGE GADTs #-}
  {-# LANGUAGE ScopedTypeVariables #-}
  
  {-# LANGUAGE Safe #-}
  
  {-# OPTIONS_HADDOCK show-extensions #-}
  
  module Clash.Prelude.BlockRam
    ( -- * BlockRAM synchronized to the system clock
      blockRam
    , blockRamPow2
    , blockRamU
    , blockRam1
    , E.ResetStrategy(..)
      -- ** Read/Write conflict resolution
    , readNew
      -- * True dual-port block RAM
      -- $tdpbram
    , trueDualPortBlockRam
    , E.RamOp(..)
    )
  where
  
  import           Prelude                 (Enum, Maybe, Eq)
  
  import           GHC.TypeLits            (KnownNat, type (^), type (<=))
  import           GHC.Stack               (HasCallStack, withFrozenCallStack)
  
  import qualified Clash.Explicit.BlockRam as E
  import           Clash.Promoted.Nat      (SNat)
  import           Clash.Signal
  import           Clash.Sized.Index       (Index)
  import           Clash.Sized.Unsigned    (Unsigned)
  import           Clash.Sized.Vector      (Vec)
  import           Clash.XException        (NFDataX)
  
  {- $tdpbram
  A true dual-port block RAM has two fully independent, fully functional access
  ports: port A and port B. Either port can do both RAM reads and writes. These
  two ports can even be on distinct clock domains, but the memory itself is shared
  between the ports. This also makes a true dual-port block RAM suitable as a
  component in a domain crossing circuit (but it needs additional logic for it to
  be safe, see e.g. 'Clash.Explicit.Synchronizer.asyncFIFOSynchronizer').
  
  A version with explicit clocks can be found in "Clash.Explicit.BlockRam".
  -}
  
  {- $setup
  >>> import Clash.Prelude as C
  >>> import qualified Data.List as L
  >>> :set -XDataKinds -XRecordWildCards -XTupleSections -XTypeApplications -XFlexibleContexts
  >>> :set -XDeriveAnyClass -XDeriveGeneric
  >>> type InstrAddr = Unsigned 8
  >>> type MemAddr = Unsigned 5
  >>> type Value = Signed 8
  >>> :{
  data Reg
    = Zero
    | PC
    | RegA
    | RegB
    | RegC
    | RegD
    | RegE
    deriving (Eq,Show,Enum,C.Generic,NFDataX)
  :}
  
  >>> :{
  data Operator = Add | Sub | Incr | Imm | CmpGt
    deriving (Eq, Show, Generic, NFDataX)
  :}
  
  >>> :{
  data Instruction
    = Compute Operator Reg Reg Reg
    | Branch Reg Value
    | Jump Value
    | Load MemAddr Reg
    | Store Reg MemAddr
    | Nop
    deriving (Eq, Show, Generic, NFDataX)
  :}
  
  >>> :{
  data MachCode
    = MachCode
    { inputX  :: Reg
    , inputY  :: Reg
    , result  :: Reg
    , aluCode :: Operator
    , ldReg   :: Reg
    , rdAddr  :: MemAddr
    , wrAddrM :: Maybe MemAddr
    , jmpM    :: Maybe Value
    }
  :}
  
  >>> :{
  nullCode = MachCode { inputX = Zero, inputY = Zero, result = Zero, aluCode = Imm
                      , ldReg = Zero, rdAddr = 0, wrAddrM = Nothing
                      , jmpM = Nothing
                      }
  :}
  
  >>> :{
  alu Add   x y = x + y
  alu Sub   x y = x - y
  alu Incr  x _ = x + 1
  alu Imm   x _ = x
  alu CmpGt x y = if x > y then 1 else 0
  :}
  
  >>> :{
  let cpu :: Vec 7 Value          -- ^ Register bank
          -> (Value,Instruction)  -- ^ (Memory output, Current instruction)
          -> ( Vec 7 Value
             , (MemAddr,Maybe (MemAddr,Value),InstrAddr)
             )
      cpu regbank (memOut,instr) = (regbank',(rdAddr,(,aluOut) <$> wrAddrM,bitCoerce ipntr))
        where
          -- Current instruction pointer
          ipntr = regbank C.!! PC
          -- Decoder
          (MachCode {..}) = case instr of
            Compute op rx ry res -> nullCode {inputX=rx,inputY=ry,result=res,aluCode=op}
            Branch cr a          -> nullCode {inputX=cr,jmpM=Just a}
            Jump a               -> nullCode {aluCode=Incr,jmpM=Just a}
            Load a r             -> nullCode {ldReg=r,rdAddr=a}
            Store r a            -> nullCode {inputX=r,wrAddrM=Just a}
            Nop                  -> nullCode
          -- ALU
          regX   = regbank C.!! inputX
          regY   = regbank C.!! inputY
          aluOut = alu aluCode regX regY
          -- next instruction
          nextPC = case jmpM of
                     Just a | aluOut /= 0 -> ipntr + a
                     _                    -> ipntr + 1
          -- update registers
          regbank' = replace Zero   0
                   $ replace PC     nextPC
                   $ replace result aluOut
                   $ replace ldReg  memOut
                   $ regbank
  :}
  
  >>> :{
  let dataMem
        :: HiddenClockResetEnable dom
        => Signal dom MemAddr
        -> Signal dom (Maybe (MemAddr,Value))
        -> Signal dom Value
      dataMem rd wrM = mealy dataMemT (C.replicate d32 0) (bundle (rd,wrM))
        where
          dataMemT mem (rd,wrM) = (mem',dout)
            where
              dout = mem C.!! rd
              mem' = case wrM of
                       Just (wr,din) -> replace wr din mem
                       Nothing       -> mem
  :}
  
  >>> :{
  let system
        :: (KnownNat n, HiddenClockResetEnable dom )
        => Vec n Instruction
        -> Signal dom Value
      system instrs = memOut
        where
          memOut = dataMem rdAddr dout
          (rdAddr,dout,ipntr) = mealyB cpu (C.replicate d7 0) (memOut,instr)
          instr  = asyncRom instrs <$> ipntr
  :}
  
  >>> :{
  -- Compute GCD of 4 and 6
  prog = -- 0 := 4
         Compute Incr Zero RegA RegA :>
         C.replicate d3 (Compute Incr RegA Zero RegA) C.++
         Store RegA 0 :>
         -- 1 := 6
         Compute Incr Zero RegA RegA :>
         C.replicate d5 (Compute Incr RegA Zero RegA) C.++
         Store RegA 1 :>
         -- A := 4
         Load 0 RegA :>
         -- B := 6
         Load 1 RegB :>
         -- start
         Compute CmpGt RegA RegB RegC :>
         Branch RegC 4 :>
         Compute CmpGt RegB RegA RegC :>
         Branch RegC 4 :>
         Jump 5 :>
         -- (a > b)
         Compute Sub RegA RegB RegA :>
         Jump (-6) :>
         -- (b > a)
         Compute Sub RegB RegA RegB :>
         Jump (-8) :>
         -- end
         Store RegA 2 :>
         Load 2 RegC :>
         Nil
  :}
  
  >>> :{
  let system2
        :: ( KnownNat n
           , HiddenClockResetEnable dom  )
        => Vec n Instruction
        -> Signal dom Value
      system2 instrs = memOut
        where
          memOut = asyncRam d32 rdAddr dout
          (rdAddr,dout,ipntr) = mealyB cpu (C.replicate d7 0) (memOut,instr)
          instr  = asyncRom instrs <$> ipntr
  :}
  
  >>> :{
  let cpu2
        :: (Vec 7 Value,Reg)
        -- ^ (Register bank, Load reg addr)
        -> (Value,Instruction)
        -- ^ (Memory output, Current instruction)
        -> ( (Vec 7 Value,Reg)
           , (MemAddr, Maybe (MemAddr, Value), InstrAddr)
           )
      cpu2 (regbank,ldRegD) (memOut,instr) =
        ((regbank', ldRegD'), (rdAddr, (,aluOut) <$> wrAddrM, bitCoerce ipntr))
       where
        -- Current instruction pointer
        ipntr = regbank C.!! PC
        -- Decoder
        (MachCode {..}) = case instr of
          Compute op rx ry res -> nullCode {inputX=rx,inputY=ry,result=res,aluCode=op}
          Branch cr a          -> nullCode {inputX=cr,jmpM=Just a}
          Jump a               -> nullCode {aluCode=Incr,jmpM=Just a}
          Load a r             -> nullCode {ldReg=r,rdAddr=a}
          Store r a            -> nullCode {inputX=r,wrAddrM=Just a}
          Nop                  -> nullCode
        -- ALU
        regX   = regbank C.!! inputX
        regY   = regbank C.!! inputY
        aluOut = alu aluCode regX regY
        -- next instruction
        nextPC =
          case jmpM of
            Just a | aluOut /= 0 -> ipntr + a
            _                    -> ipntr + 1
        -- update registers
        ldRegD'  = ldReg -- Delay the ldReg by 1 cycle
        regbank' = replace Zero   0
                 $ replace PC     nextPC
                 $ replace result aluOut
                 $ replace ldRegD memOut
                 $ regbank
  :}
  
  >>> :{
  let system3
        :: ( KnownNat n
           , HiddenClockResetEnable dom  )
        => Vec n Instruction
        -> Signal dom Value
      system3 instrs = memOut
        where
          memOut = blockRam (C.replicate d32 0) rdAddr dout
          (rdAddr,dout,ipntr) = mealyB cpu2 ((C.replicate d7 0),Zero) (memOut,instr)
          instr  = asyncRom instrs <$> ipntr
  :}
  
  >>> :{
  prog2 = -- 0 := 4
         Compute Incr Zero RegA RegA :>
         C.replicate d3 (Compute Incr RegA Zero RegA) C.++
         Store RegA 0 :>
         -- 1 := 6
         Compute Incr Zero RegA RegA :>
         C.replicate d5 (Compute Incr RegA Zero RegA) C.++
         Store RegA 1 :>
         -- A := 4
         Load 0 RegA :>
         -- B := 6
         Load 1 RegB :>
         Nop :> -- Extra NOP
         -- start
         Compute CmpGt RegA RegB RegC :>
         Branch RegC 4 :>
         Compute CmpGt RegB RegA RegC :>
         Branch RegC 4 :>
         Jump 5 :>
         -- (a > b)
         Compute Sub RegA RegB RegA :>
         Jump (-6) :>
         -- (b > a)
         Compute Sub RegB RegA RegB :>
         Jump (-8) :>
         -- end
         Store RegA 2 :>
         Load 2 RegC :>
         Nil
  :}
  
  -}
  
  -- | Create a block RAM with space for @n@ elements
  --
  -- * __NB__: Read value is delayed by 1 cycle
  -- * __NB__: Initial output value is /undefined/, reading it will throw an
  -- 'Clash.XException.XException'
  --
  -- === See also:
  --
  -- * See "Clash.Prelude.BlockRam#usingrams" for more information on how to use a
  -- Block RAM.
  -- * Use the adapter 'readNew' for obtaining write-before-read semantics like this: @'readNew' ('blockRam' inits) rd wrM@.
  -- * A large 'Vec' for the initial content may be too inefficient, depending
  -- on how it is constructed. See 'Clash.Prelude.BlockRam.File.blockRamFile' and
  -- 'Clash.Prelude.BlockRam.Blob.blockRamBlob' for different approaches that
  -- scale well.
  --
  -- === __Example__
  -- @
  -- bram40
  --   :: 'HiddenClock' dom
  --   => 'Signal' dom ('Unsigned' 6)
  --   -> 'Signal' dom (Maybe ('Unsigned' 6, 'Clash.Sized.BitVector.Bit'))
  --   -> 'Signal' dom 'Clash.Sized.BitVector.Bit'
  -- bram40 = 'blockRam' ('Clash.Sized.Vector.replicate' d40 1)
  -- @
  blockRam
    :: ( HasCallStack
       , HiddenClock dom
       , HiddenEnable dom
       , NFDataX a
       , Enum addr
       , NFDataX addr )
    => Vec n a
    -- ^ Initial content of the BRAM, also determines the size, @n@, of the BRAM
    --
    -- __NB__: __MUST__ be a constant
    -> Signal dom addr
    -- ^ Read address @r@
    -> Signal dom (Maybe (addr, a))
     -- ^ (write address @w@, value to write)
    -> Signal dom a
    -- ^ Value of the BRAM at address @r@ from the previous clock cycle
  blockRam = \cnt rd wrM -> withFrozenCallStack
    (hideEnable (hideClock E.blockRam) cnt rd wrM)
  {-# INLINE blockRam #-}
  
  -- | A version of 'blockRam' that has no default values set. May be cleared to
  -- an arbitrary state using a reset function.
  blockRamU
     :: forall n dom a r addr
     . ( HasCallStack
       , HiddenClockResetEnable dom
       , NFDataX a
       , Enum addr
       , NFDataX addr
       , 1 <= n )
    => E.ResetStrategy r (Index n -> a)
    -- ^ Whether to clear BRAM on asserted reset ('Clash.Explicit.BlockRam.ClearOnReset')
    -- or not ('Clash.Explicit.BlockRam.NoClearOnReset'). The reset needs to be
    -- asserted for at least /n/ cycles to clear the BRAM.
    -> SNat n
    -- ^ Number of elements in BRAM
    -> Signal dom addr
    -- ^ Read address @r@
    -> Signal dom (Maybe (addr, a))
    -- ^ (write address @w@, value to write)
    -> Signal dom a
    -- ^ Value of the BRAM at address @r@ from the previous clock cycle
  blockRamU =
    \rstStrategy cnt rd wrM -> withFrozenCallStack
      (hideClockResetEnable E.blockRamU) rstStrategy cnt rd wrM
  {-# INLINE blockRamU #-}
  
  -- | A version of 'blockRam' that is initialized with the same value on all
  -- memory positions
  blockRam1
     :: forall n dom a r addr
     . ( HasCallStack
       , HiddenClockResetEnable dom
       , NFDataX a
       , Enum addr
       , NFDataX addr
       , 1 <= n )
    => E.ResetStrategy r ()
    -- ^ Whether to clear BRAM on asserted reset ('Clash.Explicit.BlockRam.ClearOnReset')
    -- or not ('Clash.Explicit.BlockRam.NoClearOnReset'). The reset needs to be
    -- asserted for at least /n/ cycles to clear the BRAM.
    -> SNat n
    -- ^ Number of elements in BRAM
    -> a
    -- ^ Initial content of the BRAM (replicated /n/ times)
    -> Signal dom addr
    -- ^ Read address @r@
    -> Signal dom (Maybe (addr, a))
    -- ^ (write address @w@, value to write)
    -> Signal dom a
    -- ^ Value of the BRAM at address @r@ from the previous clock cycle
  blockRam1 =
    \rstStrategy cnt initValue rd wrM -> withFrozenCallStack
      (hideClockResetEnable E.blockRam1) rstStrategy cnt initValue rd wrM
  {-# INLINE blockRam1 #-}
  
  -- | Create a block RAM with space for 2^@n@ elements
  --
  -- * __NB__: Read value is delayed by 1 cycle
  -- * __NB__: Initial output value is /undefined/, reading it will throw an
  -- 'Clash.XException.XException'
  --
  -- === See also:
  --
  -- * See "Clash.Prelude.BlockRam#usingrams" for more information on how to use a
  -- block RAM.
  -- * Use the adapter 'readNew' for obtaining write-before-read semantics like this: @'readNew' ('blockRamPow2' inits) rd wrM@.
  -- * A large 'Vec' for the initial content may be too inefficient, depending
  -- on how it is constructed. See 'Clash.Prelude.BlockRam.File.blockRamFilePow2'
  -- and 'Clash.Prelude.BlockRam.Blob.blockRamBlobPow2' for different approaches
  -- that scale well.
  --
  -- === __Example__
  -- @
  -- bram32
  --   :: 'HiddenClock' dom
  --   => 'Signal' dom ('Unsigned' 5)
  --   -> 'Signal' dom (Maybe ('Unsigned' 5, 'Clash.Sized.BitVector.Bit'))
  --   -> 'Signal' dom 'Clash.Sized.BitVector.Bit'
  -- bram32 = 'blockRamPow2' ('Clash.Sized.Vector.replicate' d32 1)
  -- @
  blockRamPow2
    :: ( HasCallStack
       , HiddenClock dom
       , HiddenEnable dom
       , NFDataX a
       , KnownNat n
       )
    => Vec (2^n) a
    -- ^ Initial content of the BRAM
    --
    -- __NB__: __MUST__ be a constant.
    -> Signal dom (Unsigned n)
    -- ^ Read address @r@
    -> Signal dom (Maybe (Unsigned n, a))
    -- ^ (write address @w@, value to write)
    -> Signal dom a
    -- ^ Value of the @blockRAM@ at address @r@ from the previous clock
    -- cycle
  blockRamPow2 = \cnt rd wrM -> withFrozenCallStack
    (hideEnable (hideClock E.blockRamPow2) cnt rd wrM)
  {-# INLINE blockRamPow2 #-}
  
  {- | Create a read-after-write block RAM from a read-before-write one
  
  #if __GLASGOW_HASKELL__ >= 908
  >>> :t readNew (blockRam (0 :> 1 :> Nil))
  readNew (blockRam (0 :> 1 :> Nil))
    :: ...
       ...
       ... =>
       Signal dom addr -> Signal dom (Maybe (addr, a)) -> Signal dom a
  
  #elif __GLASGOW_HASKELL__ >= 902
  >>> :t readNew (blockRam (0 :> 1 :> Nil))
  readNew (blockRam (0 :> 1 :> Nil))
    :: ...
       ... =>
       Signal dom addr -> Signal dom (Maybe (addr, a)) -> Signal dom a
  
  #else
  >>> :t readNew (blockRam (0 :> 1 :> Nil))
  readNew (blockRam (0 :> 1 :> Nil))
    :: ...
       ...
       ...
       ...
       ... =>
       Signal dom addr -> Signal dom (Maybe (addr, a)) -> Signal dom a
  
  #endif
  -}
  readNew
    :: ( HiddenClockResetEnable dom
       , NFDataX a
       , Eq addr )
    => (Signal dom addr -> Signal dom (Maybe (addr, a)) -> Signal dom a)
    -- ^ The BRAM component
    -> Signal dom addr
    -- ^ Read address @r@
    -> Signal dom (Maybe (addr, a))
    -- ^ (Write address @w@, value to write)
    -> Signal dom a
    -- ^ Value of the BRAM at address @r@ from the previous clock cycle
  readNew = hideClockResetEnable E.readNew
  {-# INLINE readNew #-}
  
  -- | Produces vendor-agnostic HDL that will be inferred as a true dual-port
  -- block RAM
  --
  -- Any value that is being written on a particular port is also the
  -- value that will be read on that port, i.e. the same-port read/write behavior
  -- is: WriteFirst. For mixed-port read/write, when port A writes to the address
  -- port B reads from, the output of port B is undefined, and vice versa.
  trueDualPortBlockRam ::
    forall nAddrs dom a .
    ( HasCallStack
    , KnownNat nAddrs
    , HiddenClock dom
    , NFDataX a
    )
    => Signal dom (E.RamOp nAddrs a)
    -- ^ RAM operation for port A
    -> Signal dom (E.RamOp nAddrs a)
    -- ^ RAM operation for port B
    -> (Signal dom a, Signal dom a)
    -- ^ Outputs data on /next/ cycle. When writing, the data written
    -- will be echoed. When reading, the read data is returned.
  trueDualPortBlockRam inA inB = E.trueDualPortBlockRam hasClock hasClock inA inB
  