217 lines
7.9 KiB
Haskell
217 lines
7.9 KiB
Haskell
{-# LANGUAGE DataKinds #-}
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{-# LANGUAGE NumericUnderscores #-}
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module Decode(decode) where
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import DecodeTypes(
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RTypeFields(..), ITypeFields(..), STypeFields(..),
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BTypeFields(..), UTypeFields(..), JTypeFields(..),
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Opcode(..)
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)
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import Clash.Prelude
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import Fetch(FetchResult (Instruction, InstructionException))
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import Exceptions(Exception(..))
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import Types(Insn)
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data DecodeResult = Opcode Opcode
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| DecodeException Exception
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| InstructionException Exception
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deriving (Generic, Show, Eq, NFDataX)
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decode :: FetchResult -> DecodeResult
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decode (Instruction insn) =
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case insnToOpcode insn of
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Just opcode -> Opcode opcode
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Nothing -> DecodeException $ IllegalInstruction insn
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decode (Fetch.InstructionException exception) =
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Decode.InstructionException exception
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insnToOpcode :: Insn -> Maybe Opcode
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insnToOpcode insn =
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decodeRType insn `orElse`
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decodeIType insn `orElse`
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decodeSType insn `orElse`
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decodeBType insn `orElse`
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decodeUType insn `orElse`
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decodeJType insn
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where
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orElse :: Maybe Opcode -> Maybe Opcode -> Maybe Opcode
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orElse (Just left) _ = Just left
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orElse Nothing (Just right) = Just right
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orElse _ _ = Nothing
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decodeRType :: Insn -> Maybe Opcode
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decodeRType insn =
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case opcode of
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0b0110011 ->
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case funct3 of
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0x00 -> case funct7 of
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0x00 -> Just $ ADD (RTypeFields opcode rd funct3 rs1 rs2 funct7)
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0x20 -> Just $ SUB (RTypeFields opcode rd funct3 rs1 rs2 funct7)
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_ -> Nothing
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0x04 -> Just $ XOR (RTypeFields opcode rd funct3 rs1 rs2 funct7)
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0x06 -> Just $ OR (RTypeFields opcode rd funct3 rs1 rs2 funct7)
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0x07 -> Just $ AND (RTypeFields opcode rd funct3 rs1 rs2 funct7)
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0x01 -> Just $ SLL (RTypeFields opcode rd funct3 rs1 rs2 funct7)
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0x05 -> case funct7 of
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0x00 -> Just $ SRL (RTypeFields opcode rd funct3 rs1 rs2 funct7)
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0x20 -> Just $ SRA (RTypeFields opcode rd funct3 rs1 rs2 funct7)
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_ -> Nothing
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0x02 -> Just $ SLT (RTypeFields opcode rd funct3 rs1 rs2 funct7)
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0x03 -> Just $ SLTU (RTypeFields opcode rd funct3 rs1 rs2 funct7)
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_ -> Nothing
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_ -> Nothing
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where
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opcode = getOpcode insn
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rd = getRd insn
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funct3 = getFunct3 insn
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rs1 = getRs1 insn
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rs2 = getRs2 insn
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funct7 = getFunct7 insn
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decodeIType :: Insn -> Maybe Opcode
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decodeIType insn = case opcode of
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0b0010011 -> case funct3 of
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0x0 -> Just $ ADDI (ITypeFields opcode rd funct3 rs1 imm)
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0x4 -> Just $ XORI (ITypeFields opcode rd funct3 rs1 imm)
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0x6 -> Just $ ORI (ITypeFields opcode rd funct3 rs1 imm)
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0x7 -> Just $ ANDI (ITypeFields opcode rd funct3 rs1 imm)
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0x1 -> if slice d31 d25 (pack insn) == 0
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then Just $ SLLI (ITypeFields opcode rd funct3 rs1 imm)
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else Nothing
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0x5 -> case slice d31 d25 (pack insn) of -- Distinguish SRLI and SRAI
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0x00 -> Just $ SRLI (ITypeFields opcode rd funct3 rs1 imm)
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0x20 -> Just $ SRAI (ITypeFields opcode rd funct3 rs1 imm)
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_ -> Nothing
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0x2 -> Just $ SLTI (ITypeFields opcode rd funct3 rs1 imm)
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0x3 -> Just $ SLTIU (ITypeFields opcode rd funct3 rs1 imm)
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_ -> Nothing
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0b0000011 -> case funct3 of
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0x0 -> Just $ LB (ITypeFields opcode rd funct3 rs1 imm)
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0x1 -> Just $ LH (ITypeFields opcode rd funct3 rs1 imm)
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0x2 -> Just $ LW (ITypeFields opcode rd funct3 rs1 imm)
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0x4 -> Just $ LBU (ITypeFields opcode rd funct3 rs1 imm)
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0x5 -> Just $ LHU (ITypeFields opcode rd funct3 rs1 imm)
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_ -> Nothing
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0b1100111 -> case funct3 of
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0x0 -> Just $ JALR (ITypeFields opcode rd funct3 rs1 imm)
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_ -> Nothing
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0b1110011 -> case imm of
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0x000 -> Just $ ECALL (ITypeFields opcode rd funct3 rs1 imm)
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0x001 -> Just $ EBREAK (ITypeFields opcode rd funct3 rs1 imm)
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_ -> Nothing
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_ -> Nothing
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where
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opcode = getOpcode insn
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rd = getRd insn
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funct3 = getFunct3 insn
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rs1 = getRs1 insn
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imm = getImm12 insn
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decodeSType :: Insn -> Maybe Opcode
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decodeSType insn =
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case opcode of
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0b0100011 -> case funct3 of
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0x0 -> Just $ SB (STypeFields opcode funct3 rs1 rs2 imm12) -- Store Byte
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0x1 -> Just $ SH (STypeFields opcode funct3 rs1 rs2 imm12) -- Store Halfword
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0x2 -> Just $ SW (STypeFields opcode funct3 rs1 rs2 imm12) -- Store Word
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_ -> Nothing
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_ -> Nothing
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where
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opcode = getOpcode insn
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funct3 = getFunct3 insn
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rs1 = getRs1 insn
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rs2 = getRs2 insn
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imm12 = getImm12SType insn
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decodeBType :: Insn -> Maybe Opcode
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decodeBType insn =
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case opcode of
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0b1100011 -> case funct3 of
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0x0 -> Just $ BEQ (BTypeFields opcode funct3 rs1 rs2 imm13) -- Branch if equal
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0x1 -> Just $ BNE (BTypeFields opcode funct3 rs1 rs2 imm13) -- Branch if not equal
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0x4 -> Just $ BLT (BTypeFields opcode funct3 rs1 rs2 imm13) -- Branch if less than
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0x5 -> Just $ BGE (BTypeFields opcode funct3 rs1 rs2 imm13) -- Branch if greater or equal
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0x6 -> Just $ BLTU (BTypeFields opcode funct3 rs1 rs2 imm13) -- Branch if less than (unsigned)
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0x7 -> Just $ BGEU (BTypeFields opcode funct3 rs1 rs2 imm13) -- Branch if greater or equal (unsigned)
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_ -> Nothing
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_ -> Nothing
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where
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opcode = getOpcode insn
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funct3 = getFunct3 insn
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rs1 = getRs1 insn
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rs2 = getRs2 insn
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imm13 = getImm13BType insn
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decodeUType :: Insn -> Maybe Opcode
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decodeUType insn = case opcode of
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0b0110111 -> Just $ LUI (UTypeFields opcode rd imm20) -- LUI
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0b0010111 -> Just $ AUIPC (UTypeFields opcode rd imm20) -- AUIPC
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_ -> Nothing
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where
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opcode = getOpcode insn
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rd = getRd insn
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imm20 = getImm20UType insn
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getImm21JType :: Insn -> Unsigned 21
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getImm21JType instr = bitCoerce $ imm20 ++# imm10_1 ++# imm11 ++# imm19_12 ++# zero
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where
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imm20 = slice d31 d31 (pack instr) -- imm[20]
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imm10_1 = slice d30 d21 (pack instr) -- imm[10:1]
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imm11 = slice d20 d20 (pack instr) -- imm[11]
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imm19_12 = slice d19 d12 (pack instr) -- imm[19:12]
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zero = 0 :: BitVector 1 -- LSB always zero for J-type
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decodeJType :: Insn -> Maybe Opcode
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decodeJType insn =
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case opcode of
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0b1101111 -> Just $ JAL (JTypeFields opcode rd imm21) -- JAL
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_ -> Nothing
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where
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opcode = getOpcode insn
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rd = getRd insn
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imm21 = getImm21JType insn
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getOpcode :: Insn -> Unsigned 7
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getOpcode instr = bitCoerce $ slice d6 d0 (pack instr)
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getImm12 :: Insn -> Unsigned 12
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getImm12 instr = bitCoerce $ slice d31 d20 (pack instr)
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getImm12SType :: Insn -> Unsigned 12
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getImm12SType instr = bitCoerce $ immediateUpper ++# immediateLower
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where
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immediateUpper = (slice d31 d25 (pack instr))
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immediateLower = (slice d11 d7 (pack instr))
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getImm20UType :: Insn -> Unsigned 20
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getImm20UType instr = bitCoerce $ slice d31 d12 (pack instr)
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getImm13BType :: Insn -> Unsigned 13
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getImm13BType instr = bitCoerce $ imm12 ++# imm10_5 ++# imm4_1 ++# imm11 ++# zero
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where
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imm12 = slice d31 d31 (pack instr) -- imm[12]
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imm10_5 = slice d30 d25 (pack instr) -- imm[10:5]
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imm4_1 = slice d11 d8 (pack instr) -- imm[4:1]
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imm11 = slice d7 d7 (pack instr) -- imm[11]
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zero = 0 :: BitVector 1 -- LSB always zero for B-type
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getFunct3 :: Insn -> Unsigned 3
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getFunct3 instr = bitCoerce $ slice d14 d12 (pack instr)
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getFunct7 :: Insn -> Unsigned 7
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getFunct7 instr = bitCoerce $ slice d31 d25 (pack instr)
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getRd :: Insn -> Unsigned 5
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getRd instr = bitCoerce $ slice d11 d7 (pack instr)
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getRs2 :: Insn -> Unsigned 5
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getRs2 instr = bitCoerce $ slice d24 d20 (pack instr)
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getRs1 :: Insn -> Unsigned 5
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getRs1 instr = bitCoerce $ slice d19 d15 (pack instr)
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