first commit

hs/Fetch.hs

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+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE NumericUnderscores #-}
+
+module Fetch(fetchInstruction) where
+
+import Clash.Prelude
+import Types(Mem, Addr, FullWord)
+import Util(endianSwapWord)
+
+data Insn = Instruction FullWord
+          | Misaligned Addr
+
+fetchInstruction :: KnownNat n => Mem n -> Addr -> Insn
+fetchInstruction mem addr =
+  let
+    isWordAligned = addr .&. 3 == 0
+    addrWordAligned = addr `shiftR` 2
+    insn = mem !! addrWordAligned
+    -- TODO : check if instruction is word aligned and create type
+    -- to capture if its not.
+  in
+    case isWordAligned of
+      True -> Instruction insn
+      False -> Misaligned addr