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638 lines
14 KiB
638 lines
14 KiB
package starlark
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// This file defines the bytecode interpreter.
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import (
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"fmt"
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"os"
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"go.starlark.net/internal/compile"
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"go.starlark.net/internal/spell"
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"go.starlark.net/resolve"
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"go.starlark.net/syntax"
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)
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const vmdebug = false // TODO(adonovan): use a bitfield of specific kinds of error.
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// TODO(adonovan):
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// - optimize position table.
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// - opt: record MaxIterStack during compilation and preallocate the stack.
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func (fn *Function) CallInternal(thread *Thread, args Tuple, kwargs []Tuple) (Value, error) {
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if !resolve.AllowRecursion {
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// detect recursion
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for _, fr := range thread.stack[:len(thread.stack)-1] {
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// We look for the same function code,
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// not function value, otherwise the user could
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// defeat the check by writing the Y combinator.
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if frfn, ok := fr.Callable().(*Function); ok && frfn.funcode == fn.funcode {
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return nil, fmt.Errorf("function %s called recursively", fn.Name())
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}
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}
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}
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f := fn.funcode
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fr := thread.frameAt(0)
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// Allocate space for stack and locals.
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// Logically these do not escape from this frame
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// (See https://github.com/golang/go/issues/20533.)
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//
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// This heap allocation looks expensive, but I was unable to get
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// more than 1% real time improvement in a large alloc-heavy
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// benchmark (in which this alloc was 8% of alloc-bytes)
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// by allocating space for 8 Values in each frame, or
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// by allocating stack by slicing an array held by the Thread
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// that is expanded in chunks of min(k, nspace), for k=256 or 1024.
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nlocals := len(f.Locals)
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nspace := nlocals + f.MaxStack
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space := make([]Value, nspace)
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locals := space[:nlocals:nlocals] // local variables, starting with parameters
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stack := space[nlocals:] // operand stack
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// Digest arguments and set parameters.
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err := setArgs(locals, fn, args, kwargs)
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if err != nil {
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return nil, thread.evalError(err)
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}
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fr.locals = locals
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if vmdebug {
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fmt.Printf("Entering %s @ %s\n", f.Name, f.Position(0))
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fmt.Printf("%d stack, %d locals\n", len(stack), len(locals))
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defer fmt.Println("Leaving ", f.Name)
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}
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// Spill indicated locals to cells.
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// Each cell is a separate alloc to avoid spurious liveness.
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for _, index := range f.Cells {
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locals[index] = &cell{locals[index]}
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}
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// TODO(adonovan): add static check that beneath this point
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// - there is exactly one return statement
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// - there is no redefinition of 'err'.
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var iterstack []Iterator // stack of active iterators
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sp := 0
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var pc uint32
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var result Value
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code := f.Code
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loop:
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for {
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fr.pc = pc
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op := compile.Opcode(code[pc])
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pc++
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var arg uint32
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if op >= compile.OpcodeArgMin {
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// TODO(adonovan): opt: profile this.
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// Perhaps compiling big endian would be less work to decode?
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for s := uint(0); ; s += 7 {
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b := code[pc]
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pc++
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arg |= uint32(b&0x7f) << s
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if b < 0x80 {
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break
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}
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}
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}
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if vmdebug {
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fmt.Fprintln(os.Stderr, stack[:sp]) // very verbose!
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compile.PrintOp(f, fr.pc, op, arg)
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}
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switch op {
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case compile.NOP:
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// nop
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case compile.DUP:
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stack[sp] = stack[sp-1]
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sp++
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case compile.DUP2:
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stack[sp] = stack[sp-2]
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stack[sp+1] = stack[sp-1]
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sp += 2
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case compile.POP:
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sp--
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case compile.EXCH:
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stack[sp-2], stack[sp-1] = stack[sp-1], stack[sp-2]
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case compile.EQL, compile.NEQ, compile.GT, compile.LT, compile.LE, compile.GE:
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op := syntax.Token(op-compile.EQL) + syntax.EQL
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y := stack[sp-1]
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x := stack[sp-2]
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sp -= 2
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ok, err2 := Compare(op, x, y)
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if err2 != nil {
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err = err2
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break loop
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}
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stack[sp] = Bool(ok)
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sp++
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case compile.PLUS,
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compile.MINUS,
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compile.STAR,
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compile.SLASH,
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compile.SLASHSLASH,
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compile.PERCENT,
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compile.AMP,
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compile.PIPE,
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compile.CIRCUMFLEX,
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compile.LTLT,
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compile.GTGT,
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compile.IN:
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binop := syntax.Token(op-compile.PLUS) + syntax.PLUS
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if op == compile.IN {
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binop = syntax.IN // IN token is out of order
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}
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y := stack[sp-1]
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x := stack[sp-2]
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sp -= 2
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z, err2 := Binary(binop, x, y)
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if err2 != nil {
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err = err2
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break loop
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}
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stack[sp] = z
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sp++
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case compile.UPLUS, compile.UMINUS, compile.TILDE:
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var unop syntax.Token
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if op == compile.TILDE {
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unop = syntax.TILDE
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} else {
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unop = syntax.Token(op-compile.UPLUS) + syntax.PLUS
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}
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x := stack[sp-1]
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y, err2 := Unary(unop, x)
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if err2 != nil {
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err = err2
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break loop
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}
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stack[sp-1] = y
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case compile.INPLACE_ADD:
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y := stack[sp-1]
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x := stack[sp-2]
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sp -= 2
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// It's possible that y is not Iterable but
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// nonetheless defines x+y, in which case we
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// should fall back to the general case.
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var z Value
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if xlist, ok := x.(*List); ok {
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if yiter, ok := y.(Iterable); ok {
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if err = xlist.checkMutable("apply += to"); err != nil {
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break loop
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}
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listExtend(xlist, yiter)
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z = xlist
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}
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}
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if z == nil {
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z, err = Binary(syntax.PLUS, x, y)
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if err != nil {
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break loop
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}
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}
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stack[sp] = z
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sp++
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case compile.NONE:
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stack[sp] = None
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sp++
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case compile.TRUE:
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stack[sp] = True
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sp++
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case compile.FALSE:
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stack[sp] = False
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sp++
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case compile.MANDATORY:
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stack[sp] = mandatory{}
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sp++
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case compile.JMP:
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pc = arg
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case compile.CALL, compile.CALL_VAR, compile.CALL_KW, compile.CALL_VAR_KW:
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var kwargs Value
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if op == compile.CALL_KW || op == compile.CALL_VAR_KW {
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kwargs = stack[sp-1]
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sp--
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}
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var args Value
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if op == compile.CALL_VAR || op == compile.CALL_VAR_KW {
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args = stack[sp-1]
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sp--
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}
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// named args (pairs)
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var kvpairs []Tuple
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if nkvpairs := int(arg & 0xff); nkvpairs > 0 {
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kvpairs = make([]Tuple, 0, nkvpairs)
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kvpairsAlloc := make(Tuple, 2*nkvpairs) // allocate a single backing array
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sp -= 2 * nkvpairs
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for i := 0; i < nkvpairs; i++ {
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pair := kvpairsAlloc[:2:2]
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kvpairsAlloc = kvpairsAlloc[2:]
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pair[0] = stack[sp+2*i] // name
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pair[1] = stack[sp+2*i+1] // value
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kvpairs = append(kvpairs, pair)
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}
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}
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if kwargs != nil {
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// Add key/value items from **kwargs dictionary.
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dict, ok := kwargs.(IterableMapping)
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if !ok {
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err = fmt.Errorf("argument after ** must be a mapping, not %s", kwargs.Type())
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break loop
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}
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items := dict.Items()
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for _, item := range items {
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if _, ok := item[0].(String); !ok {
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err = fmt.Errorf("keywords must be strings, not %s", item[0].Type())
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break loop
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}
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}
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if len(kvpairs) == 0 {
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kvpairs = items
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} else {
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kvpairs = append(kvpairs, items...)
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}
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}
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// positional args
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var positional Tuple
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if npos := int(arg >> 8); npos > 0 {
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positional = make(Tuple, npos)
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sp -= npos
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copy(positional, stack[sp:])
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}
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if args != nil {
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// Add elements from *args sequence.
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iter := Iterate(args)
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if iter == nil {
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err = fmt.Errorf("argument after * must be iterable, not %s", args.Type())
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break loop
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}
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var elem Value
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for iter.Next(&elem) {
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positional = append(positional, elem)
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}
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iter.Done()
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}
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function := stack[sp-1]
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if vmdebug {
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fmt.Printf("VM call %s args=%s kwargs=%s @%s\n",
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function, positional, kvpairs, f.Position(fr.pc))
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}
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thread.endProfSpan()
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z, err2 := Call(thread, function, positional, kvpairs)
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thread.beginProfSpan()
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if err2 != nil {
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err = err2
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break loop
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}
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if vmdebug {
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fmt.Printf("Resuming %s @ %s\n", f.Name, f.Position(0))
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}
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stack[sp-1] = z
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case compile.ITERPUSH:
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x := stack[sp-1]
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sp--
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iter := Iterate(x)
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if iter == nil {
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err = fmt.Errorf("%s value is not iterable", x.Type())
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break loop
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}
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iterstack = append(iterstack, iter)
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case compile.ITERJMP:
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iter := iterstack[len(iterstack)-1]
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if iter.Next(&stack[sp]) {
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sp++
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} else {
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pc = arg
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}
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case compile.ITERPOP:
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n := len(iterstack) - 1
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iterstack[n].Done()
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iterstack = iterstack[:n]
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case compile.NOT:
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stack[sp-1] = !stack[sp-1].Truth()
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case compile.RETURN:
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result = stack[sp-1]
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break loop
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case compile.SETINDEX:
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z := stack[sp-1]
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y := stack[sp-2]
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x := stack[sp-3]
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sp -= 3
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err = setIndex(x, y, z)
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if err != nil {
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break loop
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}
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case compile.INDEX:
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y := stack[sp-1]
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x := stack[sp-2]
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sp -= 2
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z, err2 := getIndex(x, y)
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if err2 != nil {
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err = err2
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break loop
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}
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stack[sp] = z
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sp++
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case compile.ATTR:
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x := stack[sp-1]
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name := f.Prog.Names[arg]
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y, err2 := getAttr(x, name)
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if err2 != nil {
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err = err2
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break loop
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}
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stack[sp-1] = y
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case compile.SETFIELD:
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y := stack[sp-1]
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x := stack[sp-2]
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sp -= 2
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name := f.Prog.Names[arg]
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if err2 := setField(x, name, y); err2 != nil {
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err = err2
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break loop
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}
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case compile.MAKEDICT:
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stack[sp] = new(Dict)
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sp++
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case compile.SETDICT, compile.SETDICTUNIQ:
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dict := stack[sp-3].(*Dict)
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k := stack[sp-2]
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v := stack[sp-1]
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sp -= 3
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oldlen := dict.Len()
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if err2 := dict.SetKey(k, v); err2 != nil {
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err = err2
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break loop
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}
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if op == compile.SETDICTUNIQ && dict.Len() == oldlen {
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err = fmt.Errorf("duplicate key: %v", k)
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break loop
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}
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case compile.APPEND:
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elem := stack[sp-1]
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list := stack[sp-2].(*List)
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sp -= 2
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list.elems = append(list.elems, elem)
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case compile.SLICE:
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x := stack[sp-4]
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lo := stack[sp-3]
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hi := stack[sp-2]
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step := stack[sp-1]
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sp -= 4
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res, err2 := slice(x, lo, hi, step)
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if err2 != nil {
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err = err2
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break loop
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}
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stack[sp] = res
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sp++
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case compile.UNPACK:
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n := int(arg)
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iterable := stack[sp-1]
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sp--
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iter := Iterate(iterable)
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if iter == nil {
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err = fmt.Errorf("got %s in sequence assignment", iterable.Type())
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break loop
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}
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i := 0
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sp += n
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for i < n && iter.Next(&stack[sp-1-i]) {
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i++
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}
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var dummy Value
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if iter.Next(&dummy) {
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// NB: Len may return -1 here in obscure cases.
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err = fmt.Errorf("too many values to unpack (got %d, want %d)", Len(iterable), n)
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break loop
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}
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iter.Done()
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if i < n {
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err = fmt.Errorf("too few values to unpack (got %d, want %d)", i, n)
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break loop
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}
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case compile.CJMP:
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if stack[sp-1].Truth() {
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pc = arg
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}
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sp--
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case compile.CONSTANT:
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stack[sp] = fn.module.constants[arg]
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sp++
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case compile.MAKETUPLE:
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n := int(arg)
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tuple := make(Tuple, n)
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sp -= n
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copy(tuple, stack[sp:])
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stack[sp] = tuple
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sp++
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case compile.MAKELIST:
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n := int(arg)
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elems := make([]Value, n)
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sp -= n
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copy(elems, stack[sp:])
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stack[sp] = NewList(elems)
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sp++
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case compile.MAKEFUNC:
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funcode := f.Prog.Functions[arg]
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tuple := stack[sp-1].(Tuple)
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n := len(tuple) - len(funcode.Freevars)
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defaults := tuple[:n:n]
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freevars := tuple[n:]
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stack[sp-1] = &Function{
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funcode: funcode,
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module: fn.module,
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defaults: defaults,
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freevars: freevars,
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}
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case compile.LOAD:
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n := int(arg)
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module := string(stack[sp-1].(String))
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sp--
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if thread.Load == nil {
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err = fmt.Errorf("load not implemented by this application")
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break loop
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}
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thread.endProfSpan()
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dict, err2 := thread.Load(thread, module)
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thread.beginProfSpan()
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if err2 != nil {
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err = wrappedError{
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msg: fmt.Sprintf("cannot load %s: %v", module, err2),
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cause: err2,
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}
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break loop
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}
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for i := 0; i < n; i++ {
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from := string(stack[sp-1-i].(String))
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v, ok := dict[from]
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if !ok {
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err = fmt.Errorf("load: name %s not found in module %s", from, module)
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if n := spell.Nearest(from, dict.Keys()); n != "" {
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err = fmt.Errorf("%s (did you mean %s?)", err, n)
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}
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break loop
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}
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stack[sp-1-i] = v
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}
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case compile.SETLOCAL:
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locals[arg] = stack[sp-1]
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sp--
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case compile.SETCELL:
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x := stack[sp-2]
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y := stack[sp-1]
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sp -= 2
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y.(*cell).v = x
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case compile.SETGLOBAL:
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fn.module.globals[arg] = stack[sp-1]
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sp--
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case compile.LOCAL:
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x := locals[arg]
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if x == nil {
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err = fmt.Errorf("local variable %s referenced before assignment", f.Locals[arg].Name)
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break loop
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}
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stack[sp] = x
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sp++
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case compile.FREE:
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stack[sp] = fn.freevars[arg]
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sp++
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case compile.CELL:
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x := stack[sp-1]
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stack[sp-1] = x.(*cell).v
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case compile.GLOBAL:
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x := fn.module.globals[arg]
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if x == nil {
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err = fmt.Errorf("global variable %s referenced before assignment", f.Prog.Globals[arg].Name)
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break loop
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}
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stack[sp] = x
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sp++
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case compile.PREDECLARED:
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name := f.Prog.Names[arg]
|
|
x := fn.module.predeclared[name]
|
|
if x == nil {
|
|
err = fmt.Errorf("internal error: predeclared variable %s is uninitialized", name)
|
|
break loop
|
|
}
|
|
stack[sp] = x
|
|
sp++
|
|
|
|
case compile.UNIVERSAL:
|
|
stack[sp] = Universe[f.Prog.Names[arg]]
|
|
sp++
|
|
|
|
default:
|
|
err = fmt.Errorf("unimplemented: %s", op)
|
|
break loop
|
|
}
|
|
}
|
|
|
|
// ITERPOP the rest of the iterator stack.
|
|
for _, iter := range iterstack {
|
|
iter.Done()
|
|
}
|
|
|
|
fr.locals = nil
|
|
|
|
return result, err
|
|
}
|
|
|
|
type wrappedError struct {
|
|
msg string
|
|
cause error
|
|
}
|
|
|
|
func (e wrappedError) Error() string {
|
|
return e.msg
|
|
}
|
|
|
|
// Implements the xerrors.Wrapper interface
|
|
// https://godoc.org/golang.org/x/xerrors#Wrapper
|
|
func (e wrappedError) Unwrap() error {
|
|
return e.cause
|
|
}
|
|
|
|
// mandatory is a sentinel value used in a function's defaults tuple
|
|
// to indicate that a (keyword-only) parameter is mandatory.
|
|
type mandatory struct{}
|
|
|
|
func (mandatory) String() string { return "mandatory" }
|
|
func (mandatory) Type() string { return "mandatory" }
|
|
func (mandatory) Freeze() {} // immutable
|
|
func (mandatory) Truth() Bool { return False }
|
|
func (mandatory) Hash() (uint32, error) { return 0, nil }
|
|
|
|
// A cell is a box containing a Value.
|
|
// Local variables marked as cells hold their value indirectly
|
|
// so that they may be shared by outer and inner nested functions.
|
|
// Cells are always accessed using indirect CELL/SETCELL instructions.
|
|
// The FreeVars tuple contains only cells.
|
|
// The FREE instruction always yields a cell.
|
|
type cell struct{ v Value }
|
|
|
|
func (c *cell) String() string { return "cell" }
|
|
func (c *cell) Type() string { return "cell" }
|
|
func (c *cell) Freeze() {
|
|
if c.v != nil {
|
|
c.v.Freeze()
|
|
}
|
|
}
|
|
func (c *cell) Truth() Bool { panic("unreachable") }
|
|
func (c *cell) Hash() (uint32, error) { panic("unreachable") }
|