skylark: Index | Files

package compile

import ""

The compile package defines the Skylark bytecode compiler. It is an internal package of the Skylark interpreter and is not directly accessible to clients.

The compiler generates byte code with optional uint32 operands for a virtual machine with the following components:

- a program counter, which is an index into the byte code array.
- an operand stack, whose maximum size is computed for each function by the compiler.
- an stack of active iterators.
- an array of local variables.
  The number of local variables and their indices are computed by the resolver.
- an array of free variables, for nested functions.
  As with locals, these are computed by the resolver.
- an array of global variables, shared among all functions in the same module.
  All elements are initially nil.
- two maps of predeclared and universal identifiers.

A line number table maps each program counter value to a source position; these source positions do not currently record column information.

Operands, logically uint32s, are encoded using little-endian 7-bit varints, the top bit indicating that more bytes follow.


Package Files

compile.go serial.go


const Version = 3

Increment this to force recompilation of saved bytecode files.

func PrintOp Uses

func PrintOp(fn *Funcode, pc uint32, op Opcode, arg uint32)

PrintOp prints an instruction. It is provided for debugging.

type Funcode Uses

type Funcode struct {
    Prog *Program
    Pos  syntax.Position // position of def or lambda token
    Name string          // name of this function
    Code []byte          // the byte code

    Locals                []Ident // for error messages and tracing
    Freevars              []Ident // for tracing
    MaxStack              int
    NumParams             int
    HasVarargs, HasKwargs bool
    // contains filtered or unexported fields

A Funcode is the code of a compiled Skylark function.

Funcodes are serialized by the gobFunc function, which must be updated whenever this declaration is changed.

func Expr Uses

func Expr(expr syntax.Expr, locals []*syntax.Ident) *Funcode

Expr compiles an expression to a program consisting of a single toplevel function.

func (*Funcode) Position Uses

func (fn *Funcode) Position(pc uint32) syntax.Position

type Ident Uses

type Ident struct {
    Name string
    Pos  syntax.Position

An Ident is the name and position of an identifier.

type Opcode Uses

type Opcode uint8
const (
    NOP Opcode = iota // - NOP -

    // stack operations
    DUP  //   x DUP x x
    DUP2 // x y DUP2 x y x y
    POP  //   x POP -
    EXCH // x y EXCH y x

    // binary comparisons
    // (order must match Token)

    // binary arithmetic
    // (order must match Token)


    // unary operators
    UPLUS  // x UPLUS x
    UMINUS // x UMINUS -x
    TILDE  // x TILDE ~x

    NONE  // - NONE None
    TRUE  // - TRUE True
    FALSE // - FALSE False

    ITERPUSH    //       iterable ITERPUSH -     [pushes the iterator stack]
    ITERPOP     //              - ITERPOP -      [pops the iterator stack]
    NOT         //          value NOT bool
    RETURN      //          value RETURN -
    SETINDEX    //        a i new SETINDEX -
    INDEX       //            a i INDEX elem
    SETDICT     // dict key value SETDICT -
    SETDICTUNIQ // dict key value SETDICTUNIQ -
    APPEND      //      list elem APPEND -
    SLICE       //   x lo hi step SLICE slice
    INPLACE_ADD //            x y INPLACE_ADD z      where z is x+y or x.extend(y)
    MAKEDICT    //              - MAKEDICT dict

    // control flow
    JMP     //            - JMP<addr>     -
    CJMP    //         cond CJMP<addr>    -
    ITERJMP //            - ITERJMP<addr> elem   (and fall through) [acts on topmost iterator]

    CONSTANT    //                - CONSTANT<constant>  value
    MAKETUPLE   //        x1 ... xn MAKETUPLE<n>        tuple
    MAKELIST    //        x1 ... xn MAKELIST<n>         list
    MAKEFUNC    //      args kwargs MAKEFUNC<func>      fn
    LOAD        //  from1 ... fromN module LOAD<n>      v1 ... vN
    SETLOCAL    //            value SETLOCAL<local>     -
    SETGLOBAL   //            value SETGLOBAL<global>   -
    LOCAL       //                - LOCAL<local>        value
    FREE        //                - FREE<freevar>       value
    GLOBAL      //                - GLOBAL<global>      value
    PREDECLARED //                - PREDECLARED<name>   value
    UNIVERSAL   //                - UNIVERSAL<name>     value
    ATTR        //                x ATTR<name>          y           y =
    SETFIELD    //              x y SETFIELD<name>      -  = y
    UNPACK      //         iterable UNPACK<n>           vn ... v1

    // n>>8 is #positional args and n&0xff is #named args (pairs).
    CALL        // fn positional named                CALL<n>        result
    CALL_VAR    // fn positional named *args          CALL_VAR<n>    result
    CALL_KW     // fn positional named       **kwargs CALL_KW<n>     result
    CALL_VAR_KW // fn positional named *args **kwargs CALL_VAR_KW<n> result

    OpcodeArgMin = JMP
    OpcodeMax    = CALL_VAR_KW

"x DUP x x" is a "stack picture" that describes the state of the stack before and after execution of the instruction.

OP<index> indicates an immediate operand that is an index into the specified table: locals, names, freevars, constants.

func (Opcode) String Uses

func (op Opcode) String() string

type Program Uses

type Program struct {
    Loads     []Ident       // name (really, string) and position of each load stmt
    Names     []string      // names of attributes and predeclared variables
    Constants []interface{} // = string | int64 | float64 | *big.Int
    Functions []*Funcode
    Globals   []Ident  // for error messages and tracing
    Toplevel  *Funcode // module initialization function

A Program is a Skylark file in executable form.

Programs are serialized by the gobProgram function, which must be updated whenever this declaration is changed.

func File Uses

func File(stmts []syntax.Stmt, locals, globals []*syntax.Ident) *Program

File compiles the statements of a file into a program.

func ReadProgram Uses

func ReadProgram(in io.Reader) (*Program, error)

ReadProgram reads a compiled Skylark program from in.

func (*Program) Write Uses

func (prog *Program) Write(out io.Writer) error

Write writes a compiled Skylark program to out.

Package compile imports 10 packages (graph) and is imported by 2 packages. Updated 2018-11-07. Refresh now. Tools for package owners.