fix offset parsing and one byte loading instruction

src/Language/Wasm/Interpreter.hs

@@ -649,7 +649,7 @@ eval store FunctionInstance { funcType, moduleInstance, code = Function { localT
             MemoryInstance { memory } <- readIORef $ memInstances store ! (memaddrs moduleInstance ! 0)
             let addr = fromIntegral $ v + fromIntegral offset
             byte <- IOVector.read memory addr
-            let val = asWord32 $ if byte >= 128 then -1 * fromIntegral (v .&. 0x7F) else fromIntegral v
+            let val = asWord32 $ if byte >= 128 then -1 * fromIntegral (byte .&. 0x7F) else fromIntegral byte
             return $ Done ctx { stack = VI32 val : rest }
         step ctx@EvalCtx{ stack = (VI32 v:rest) } (I32Load16U MemArg { offset }) = do
             MemoryInstance { memory } <- readIORef $ memInstances store ! (memaddrs moduleInstance ! 0)

src/Language/Wasm/Structure.hs

@@ -75,7 +75,7 @@ data FBinOp = FAdd | FSub | FMul | FDiv | FMin | FMax | FCopySign deriving (Show
 
 data FRelOp = FEq | FNe | FLt | FGt | FLe | FGe deriving (Show, Eq)
 
-data MemArg = MemArg { align :: Natural, offset :: Natural } deriving (Show, Eq)
+data MemArg = MemArg { offset :: Natural, align :: Natural } deriving (Show, Eq)
 
 type LabelIndex = Natural
 type FuncIndex = Natural