-- Computes the minimum size (in bytes) of instructions

MODULE {InstrSize} {instrSize, branchInstrSize} {}

INCLUDE "ByteCodeAst.ag"
INCLUDE "PrettyInstr.ag"

import
{
import Data.ByteString.Lazy(ByteString,pack)
import ByteCode
import Data.Bits
import Data.Word
import Codec.Binary.UTF8.String
}

{
branchInstrSize :: Int
branchInstrSize = 4
}

WRAPPER Instruction

{
-- | Computes the minimum length of an instruction (in bytes)
instrSize :: Instruction -> Int
instrSize instr = size where
  inh  = Inh_Instruction {}
  sem  = sem_Instruction instr
  syn  = wrap_Instruction sem inh
  size = output_Syn_Instruction syn
}

ATTR InstructionLike DebugType CaseOffsets [ | | output : Int ]
SEM CaseOffsets | Nil       lhs.output = 0
SEM Instruction | Virtual   lhs.output = 0

-- Give a different interpretation to the pretty-printing instructions
{
infixr 3 ##
(##) :: Int -> Int -> Int
(##) = (+)

u8 :: Word8 -> Int
u8 _ = 1

s24 :: Word32 -> Int
s24 _ = 3

u30 :: Word32 -> Int
u30 w =  1 + tl where
  r = shiftR w 7
  tl | r > 0     = u30 r
     | otherwise = 0

u30size :: Int -> Int
u30size = u30 . fromIntegral
}

SEM Instruction
  | LookupSwitch
      loc.newOffset = 0  -- doesnt matter
  | IfEq IfFalse IfGe IfGt IfLe IfLt IfNGe IfNGt IfNLe IfNLt IfNe IfStrictEq IfStrictNe IfTrue Jump
      loc.newOffset = 0  -- doesnt matter

SEM CaseOffsets | Cons
  loc.newOffset = 0  -- doesnt matter