# vmdef

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This module contains the type definitions for the new evaluation engine. An instruction is 1-3 int32s in memory, it is a register based VM.

# Imports

ast, idents, options, modulegraphs, lineinfos

# Types

    PCtx = ref TCtx

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    PEvalContext = PCtx

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    PProc = ref object
      blocks*: seq[TBlock]
      sym*: PSym
      regInfo*: seq[tuple[inUse: bool, kind: TSlotKind]]

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    Profiler = object
      tEnter*: float
      tos*: PStackFrame

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    PStackFrame = ref TStackFrame

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    TBlock = object
      label*: PSym
      fixups*: seq[TPosition]

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    TCtx = object of TPassContext
      code*: seq[TInstr]
      debug*: seq[TLineInfo]
      globals*: PNode
      constants*: PNode
      contstantTab*: TNodeTable
      types*: seq[PType]
      currentExceptionA*, currentExceptionB*: PNode
      exceptionInstr*: int
      prc*: PProc
      module*: PSym
      callsite*: PNode
      mode*: TEvalMode
      features*: TSandboxFlags
      traceActive*: bool
      loopIterations*, callDepth*: int
      comesFromHeuristic*: TLineInfo
      callbacks*: seq[VmCallback]
      callbackIndex*: Table[string, int]
      errorFlag*: string
      cache*: IdentCache
      config*: ConfigRef
      graph*: ModuleGraph
      oldErrorCount*: int
      profiler*: Profiler
      templInstCounter*: ref int
      vmstateDiff*: seq[(PSym, PNode)]
      procToCodePos*: Table[int, VmProcInfo]
      cannotEval*: bool
      locals*: IntSet

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    TDest = range[-1 .. 65535'u64.int]

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    TEvalMode = enum
      emRepl,                   ## evaluate because in REPL mode
      emConst,                  ## evaluate for 'const' according to spec
      emOptimize,               ## evaluate for optimization purposes (same as
                                 ## emConst?)
      emStaticExpr,             ## evaluate for enforced compile time eval
                                 ## ('static' context)
      emStaticStmt               ## 'static' as an expression

  reason for evaluation Source Edit

    TFullReg = object
      case kind*: TRegisterKind
      of rkNone:
        nil
      of rkInt:
        intVal*: BiggestInt
      of rkFloat:
        floatVal*: BiggestFloat
      of rkNode:
        node*: PNode
      of rkRegisterAddr:
        regAddr*: ptr TFullReg
      of rkNodeAddr:
        nodeAddr*: ptr PNode

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    TInstr = distinct TInstrType

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    TInstrType = uint64

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    TOpcode = enum
      opcEof, opcRet, opcYldYoid, opcYldVal, opcAsgnInt, opcAsgnFloat, opcAsgnRef,
      opcAsgnComplex, opcCastIntToFloat32, opcCastIntToFloat64, opcCastFloatToInt32,
      opcCastFloatToInt64, opcCastPtrToInt, opcCastIntToPtr, opcFastAsgnComplex,
      opcNodeToReg, opcLdArr, opcLdArrAddr, opcWrArr, opcLdObj, opcLdObjAddr,
      opcWrObj, opcAddrReg, opcAddrNode, opcLdDeref, opcWrDeref, opcWrStrIdx,
      opcLdStrIdx, opcLdStrIdxAddr, opcSlice, opcAddInt, opcAddImmInt, opcSubInt,
      opcSubImmInt, opcLenSeq, opcLenStr, opcLenCstring, opcIncl, opcInclRange,
      opcExcl, opcCard, opcMulInt, opcDivInt, opcModInt, opcAddFloat, opcSubFloat,
      opcMulFloat, opcDivFloat, opcShrInt, opcShlInt, opcAshrInt, opcBitandInt,
      opcBitorInt, opcBitxorInt, opcAddu, opcSubu, opcMulu, opcDivu, opcModu,
      opcEqInt, opcLeInt, opcLtInt, opcEqFloat, opcLeFloat, opcLtFloat, opcLeu,
      opcLtu, opcEqRef, opcEqNimNode, opcSameNodeType, opcXor, opcNot,
      opcUnaryMinusInt, opcUnaryMinusFloat, opcBitnotInt, opcEqStr, opcEqCString,
      opcLeStr, opcLtStr, opcEqSet, opcLeSet, opcLtSet, opcMulSet, opcPlusSet,
      opcMinusSet, opcXorSet, opcConcatStr, opcContainsSet, opcRepr, opcSetLenStr,
      opcSetLenSeq, opcIsNil, opcOf, opcIs, opcParseFloat, opcConv, opcCast,
      opcQuit, opcInvalidField, opcNarrowS, opcNarrowU, opcNarrowR, opcSignExtend,
      opcAddStrCh, opcAddStrStr, opcAddSeqElem, opcRangeChck, opcNAdd,
      opcNAddMultiple, opcNKind, opcNSymKind, opcNIntVal, opcNFloatVal, opcNSymbol,
      opcNIdent, opcNGetType, opcNStrVal, opcNSigHash, opcNGetSize, opcNSetIntVal,
      opcNSetFloatVal, opcNSetSymbol, opcNSetIdent, opcNSetStrVal, opcNNewNimNode,
      opcNCopyNimNode, opcNCopyNimTree, opcNDel, opcGenSym, opcNccValue, opcNccInc,
      opcNcsAdd, opcNcsIncl, opcNcsLen, opcNcsAt, opcNctPut, opcNctLen, opcNctGet,
      opcNctHasNext, opcNctNext, opcNodeId, opcSlurp, opcGorge, opcParseExprToAst,
      opcParseStmtToAst, opcQueryErrorFlag, opcNError, opcNWarning, opcNHint,
      opcNGetLineInfo, opcNCopyLineInfo, opcNSetLineInfoLine, opcNSetLineInfoColumn,
      opcNSetLineInfoFile, opcEqIdent, opcStrToIdent, opcGetImpl, opcGetImplTransf,
      opcEcho, opcIndCall, opcIndCallAsgn, opcRaise, opcNChild, opcNSetChild,
      opcCallSite, opcNewStr, opcTJmp, opcFJmp, opcJmp, opcJmpBack, opcBranch,
      opcTry, opcExcept, opcFinally, opcFinallyEnd, opcNew, opcNewSeq, opcLdNull,
      opcLdNullReg, opcLdConst, opcAsgnConst, opcLdGlobal, opcLdGlobalAddr,
      opcLdGlobalDerefFFI, opcLdGlobalAddrDerefFFI, opcLdImmInt, opcNBindSym,
      opcNDynBindSym, opcSetType, opcTypeTrait, opcSymOwner, opcSymIsInstantiationOf

  Source Edit

    TPosition = distinct int

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    TRegister = range[0 .. 65535'u64.int]

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    TRegisterKind = enum
      rkNone, rkNode, rkInt, rkFloat, rkRegisterAddr, rkNodeAddr

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    TSandboxFlag = enum
      allowCast,                ## allow unsafe language feature: 'cast'
      allowInfiniteLoops,       ## allow endless loops
      allowInfiniteRecursion     ## allow infinite recursion

  what the evaluation engine should allow Source Edit

    TSandboxFlags = set[TSandboxFlag]

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    TSlotKind = enum
      slotEmpty, slotFixedVar, slotFixedLet, slotTempUnknown, slotTempInt,
      slotTempFloat, slotTempStr, slotTempComplex, slotTempPerm

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    TStackFrame {.acyclic.} = object
      prc*: PSym
      slots*: seq[TFullReg]
      next*: PStackFrame
      comesFrom*: int
      safePoints*: seq[int]

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    VmArgs = object
      ra*, rb*, rc*: Natural = 0
      slots*: ptr UncheckedArray[TFullReg]
      currentException*: PNode
      currentLineInfo*: TLineInfo

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    VmCallback = proc (args: VmArgs) {.closure.}

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    VmProcInfo = object
      pc*: int32
      usedRegisters*: int32

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# Consts

    byteExcess = 128

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    firstABxInstr = opcTJmp

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    largeInstrs = {opcConv, opcCast, opcNewSeq, opcOf}

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    nimNodeFlag = 16

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    NoVmProcInfo = (pc: 0, usedRegisters: -1)

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    regAMask = 65535'u64

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    regAShift = 8'u64

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    regBMask = 65535'u64

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    regBShift = 24'u64

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    regBxMask = 16777215'u64

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    regBxMax = 8388607

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    regBxMin = -8388607

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    regBxShift = 24'u64

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    regCMask = 65535'u64

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    regCShift = 40'u64

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    regOMask = 255'u64

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    regOShift = 0'u

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    relativeJumps = {opcTJmp, opcFJmp, opcJmp, opcJmpBack}

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    slotSomeTemp = slotTempUnknown

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    wordExcess = 8388608

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# Procs

    proc newCtx(module: PSym; cache: IdentCache; g: ModuleGraph; idgen: IdGenerator): PCtx {.
        ...raises: [], tags: [], forbids: [].}

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    proc refresh(c: PCtx; module: PSym; idgen: IdGenerator) {....raises: [], tags: [],
        forbids: [].}

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    proc registerCallback(c: PCtx; name: string; callback: VmCallback): int {.
        discardable, ...raises: [], tags: [], forbids: [].}

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# Templates

    template jmpDiff(x: TInstr): int

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    template opcode(x: TInstr): TOpcode

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    template regA(x: TInstr): TRegister

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    template regB(x: TInstr): TRegister

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    template regBx(x: TInstr): int

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    template regC(x: TInstr): TRegister

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