// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package gc
import (
"cmd/compile/internal/syntax"
"cmd/compile/internal/types"
"fmt"
)
func (p *noder) funcLit(expr *syntax.FuncLit) *Node {
xtype := p.typeExpr(expr.Type)
ntype := p.typeExpr(expr.Type)
xfunc := p.nod(expr, ODCLFUNC, nil, nil)
xfunc.Func.SetIsHiddenClosure(Curfn != nil)
xfunc.Func.Nname = newfuncnamel(p.pos(expr), nblank.Sym) // filled in by typecheckclosure
xfunc.Func.Nname.Name.Param.Ntype = xtype
xfunc.Func.Nname.Name.Defn = xfunc
clo := p.nod(expr, OCLOSURE, nil, nil)
clo.Func.Ntype = ntype
xfunc.Func.Closure = clo
clo.Func.Closure = xfunc
p.funcBody(xfunc, expr.Body)
// closure-specific variables are hanging off the
// ordinary ones in the symbol table; see oldname.
// unhook them.
// make the list of pointers for the closure call.
for _, v := range xfunc.Func.Cvars.Slice() {
// Unlink from v1; see comment in syntax.go type Param for these fields.
v1 := v.Name.Defn
v1.Name.Param.Innermost = v.Name.Param.Outer
// If the closure usage of v is not dense,
// we need to make it dense; now that we're out
// of the function in which v appeared,
// look up v.Sym in the enclosing function
// and keep it around for use in the compiled code.
//
// That is, suppose we just finished parsing the innermost
// closure f4 in this code:
//
// func f() {
// v := 1
// func() { // f2
// use(v)
// func() { // f3
// func() { // f4
// use(v)
// }()
// }()
// }()
// }
//
// At this point v.Outer is f2's v; there is no f3's v.
// To construct the closure f4 from within f3,
// we need to use f3's v and in this case we need to create f3's v.
// We are now in the context of f3, so calling oldname(v.Sym)
// obtains f3's v, creating it if necessary (as it is in the example).
//
// capturevars will decide whether to use v directly or &v.
v.Name.Param.Outer = oldname(v.Sym)
}
return clo
}
func typecheckclosure(clo *Node, top int) {
xfunc := clo.Func.Closure
clo.Func.Ntype = typecheck(clo.Func.Ntype, Etype)
clo.Type = clo.Func.Ntype.Type
clo.Func.Top = top
// Do not typecheck xfunc twice, otherwise, we will end up pushing
// xfunc to xtop multiple times, causing initLSym called twice.
// See #30709
if xfunc.Typecheck() == 1 {
return
}
for _, ln := range xfunc.Func.Cvars.Slice() {
n := ln.Name.Defn
if !n.Name.Captured() {
n.Name.SetCaptured(true)
if n.Name.Decldepth == 0 {
Fatalf("typecheckclosure: var %S does not have decldepth assigned", n)
}
// Ignore assignments to the variable in straightline code
// preceding the first capturing by a closure.
if n.Name.Decldepth == decldepth {
n.SetAssigned(false)
}
}
}
xfunc.Func.Nname.Sym = closurename(Curfn)
disableExport(xfunc.Func.Nname.Sym)
declare(xfunc.Func.Nname, PFUNC)
xfunc = typecheck(xfunc, ctxStmt)
// Type check the body now, but only if we're inside a function.
// At top level (in a variable initialization: curfn==nil) we're not
// ready to type check code yet; we'll check it later, because the
// underlying closure function we create is added to xtop.
if Curfn != nil && clo.Type != nil {
oldfn := Curfn
Curfn = xfunc
olddd := decldepth
decldepth = 1
typecheckslice(xfunc.Nbody.Slice(), ctxStmt)
decldepth = olddd
Curfn = oldfn
}
xtop = append(xtop, xfunc)
}
// globClosgen is like Func.Closgen, but for the global scope.
var globClosgen int
// closurename generates a new unique name for a closure within
// outerfunc.
func closurename(outerfunc *Node) *types.Sym {
outer := "glob."
prefix := "func"
gen := &globClosgen
if outerfunc != nil {
if outerfunc.Func.Closure != nil {
prefix = ""
}
outer = outerfunc.funcname()
// There may be multiple functions named "_". In those
// cases, we can't use their individual Closgens as it
// would lead to name clashes.
if !outerfunc.Func.Nname.isBlank() {
gen = &outerfunc.Func.Closgen
}
}
*gen++
return lookup(fmt.Sprintf("%s.%s%d", outer, prefix, *gen))
}
// capturevarscomplete is set to true when the capturevars phase is done.
var capturevarscomplete bool
// capturevars is called in a separate phase after all typechecking is done.
// It decides whether each variable captured by a closure should be captured
// by value or by reference.
// We use value capturing for values <= 128 bytes that are never reassigned
// after capturing (effectively constant).
func capturevars(xfunc *Node) {
lno := lineno
lineno = xfunc.Pos
clo := xfunc.Func.Closure
cvars := xfunc.Func.Cvars.Slice()
out := cvars[:0]
for _, v := range cvars {
if v.Type == nil {
// If v.Type is nil, it means v looked like it
// was going to be used in the closure, but
// isn't. This happens in struct literals like
// s{f: x} where we can't distinguish whether
// f is a field identifier or expression until
// resolving s.
continue
}
out = append(out, v)
// type check the & of closed variables outside the closure,
// so that the outer frame also grabs them and knows they escape.
dowidth(v.Type)
outer := v.Name.Param.Outer
outermost := v.Name.Defn
// out parameters will be assigned to implicitly upon return.
if outermost.Class() != PPARAMOUT && !outermost.Addrtaken() && !outermost.Assigned() && v.Type.Width <= 128 {
v.Name.SetByval(true)
} else {
outermost.SetAddrtaken(true)
outer = nod(OADDR, outer, nil)
}
if Debug['m'] > 1 {
var name *types.Sym
if v.Name.Curfn != nil && v.Name.Curfn.Func.Nname != nil {
name = v.Name.Curfn.Func.Nname.Sym
}
how := "ref"
if v.Name.Byval() {
how = "value"
}
Warnl(v.Pos, "%v capturing by %s: %v (addr=%v assign=%v width=%d)", name, how, v.Sym, outermost.Addrtaken(), outermost.Assigned(), int32(v.Type.Width))
}
outer = typecheck(outer, ctxExpr)
clo.Func.Enter.Append(outer)
}
xfunc.Func.Cvars.Set(out)
lineno = lno
}
// transformclosure is called in a separate phase after escape analysis.
// It transform closure bodies to properly reference captured variables.
func transformclosure(xfunc *Node) {
lno := lineno
lineno = xfunc.Pos
clo := xfunc.Func.Closure
if clo.Func.Top&ctxCallee != 0 {
// If the closure is directly called, we transform it to a plain function call
// with variables passed as args. This avoids allocation of a closure object.
// Here we do only a part of the transformation. Walk of OCALLFUNC(OCLOSURE)
// will complete the transformation later.
// For illustration, the following closure:
// func(a int) {
// println(byval)
// byref++
// }(42)
// becomes:
// func(byval int, &byref *int, a int) {
// println(byval)
// (*&byref)++
// }(byval, &byref, 42)
// f is ONAME of the actual function.
f := xfunc.Func.Nname
// We are going to insert captured variables before input args.
var params []*types.Field
var decls []*Node
for _, v := range xfunc.Func.Cvars.Slice() {
if !v.Name.Byval() {
// If v of type T is captured by reference,
// we introduce function param &v *T
// and v remains PAUTOHEAP with &v heapaddr
// (accesses will implicitly deref &v).
addr := newname(lookup("&" + v.Sym.Name))
addr.Type = types.NewPtr(v.Type)
v.Name.Param.Heapaddr = addr
v = addr
}
v.SetClass(PPARAM)
decls = append(decls, v)
fld := types.NewField()
fld.Nname = asTypesNode(v)
fld.Type = v.Type
fld.Sym = v.Sym
params = append(params, fld)
}
if len(params) > 0 {
// Prepend params and decls.
f.Type.Params().SetFields(append(params, f.Type.Params().FieldSlice()...))
xfunc.Func.Dcl = append(decls, xfunc.Func.Dcl...)
}
dowidth(f.Type)
xfunc.Type = f.Type // update type of ODCLFUNC
} else {
// The closure is not called, so it is going to stay as closure.
var body []*Node
offset := int64(Widthptr)
for _, v := range xfunc.Func.Cvars.Slice() {
// cv refers to the field inside of closure OSTRUCTLIT.
cv := nod(OCLOSUREVAR, nil, nil)
cv.Type = v.Type
if !v.Name.Byval() {
cv.Type = types.NewPtr(v.Type)
}
offset = Rnd(offset, int64(cv.Type.Align))
cv.Xoffset = offset
offset += cv.Type.Width
if v.Name.Byval() && v.Type.Width <= int64(2*Widthptr) {
// If it is a small variable captured by value, downgrade it to PAUTO.
v.SetClass(PAUTO)
xfunc.Func.Dcl = append(xfunc.Func.Dcl, v)
body = append(body, nod(OAS, v, cv))
} else {
// Declare variable holding addresses taken from closure
// and initialize in entry prologue.
addr := newname(lookup("&" + v.Sym.Name))
addr.Type = types.NewPtr(v.Type)
addr.SetClass(PAUTO)
addr.Name.SetUsed(true)
addr.Name.Curfn = xfunc
xfunc.Func.Dcl = append(xfunc.Func.Dcl, addr)
v.Name.Param.Heapaddr = addr
if v.Name.Byval() {
cv = nod(OADDR, cv, nil)
}
body = append(body, nod(OAS, addr, cv))
}
}
if len(body) > 0 {
typecheckslice(body, ctxStmt)
xfunc.Func.Enter.Set(body)
xfunc.Func.SetNeedctxt(true)
}
}
lineno = lno
}
// hasemptycvars reports whether closure clo has an
// empty list of captured vars.
func hasemptycvars(clo *Node) bool {
xfunc := clo.Func.Closure
return xfunc.Func.Cvars.Len() == 0
}
// closuredebugruntimecheck applies boilerplate checks for debug flags
// and compiling runtime
func closuredebugruntimecheck(clo *Node) {
if Debug_closure > 0 {
xfunc := clo.Func.Closure
if clo.Esc == EscHeap {
Warnl(clo.Pos, "heap closure, captured vars = %v", xfunc.Func.Cvars)
} else {
Warnl(clo.Pos, "stack closure, captured vars = %v", xfunc.Func.Cvars)
}
}
if compiling_runtime && clo.Esc == EscHeap {
yyerrorl(clo.Pos, "heap-allocated closure, not allowed in runtime.")
}
}
// closureType returns the struct type used to hold all the information
// needed in the closure for clo (clo must be a OCLOSURE node).
// The address of a variable of the returned type can be cast to a func.
func closureType(clo *Node) *types.Type {
// Create closure in the form of a composite literal.
// supposing the closure captures an int i and a string s
// and has one float64 argument and no results,
// the generated code looks like:
//
// clos = &struct{.F uintptr; i *int; s *string}{func.1, &i, &s}
//
// The use of the struct provides type information to the garbage
// collector so that it can walk the closure. We could use (in this case)
// [3]unsafe.Pointer instead, but that would leave the gc in the dark.
// The information appears in the binary in the form of type descriptors;
// the struct is unnamed so that closures in multiple packages with the
// same struct type can share the descriptor.
fields := []*Node{
namedfield(".F", types.Types[TUINTPTR]),
}
for _, v := range clo.Func.Closure.Func.Cvars.Slice() {
typ := v.Type
if !v.Name.Byval() {
typ = types.NewPtr(typ)
}
fields = append(fields, symfield(v.Sym, typ))
}
typ := tostruct(fields)
typ.SetNoalg(true)
return typ
}
func walkclosure(clo *Node, init *Nodes) *Node {
xfunc := clo.Func.Closure
// If no closure vars, don't bother wrapping.
if hasemptycvars(clo) {
if Debug_closure > 0 {
Warnl(clo.Pos, "closure converted to global")
}
return xfunc.Func.Nname
}
closuredebugruntimecheck(clo)
typ := closureType(clo)
clos := nod(OCOMPLIT, nil, nod(ODEREF, typenod(typ), nil))
clos.Esc = clo.Esc
clos.Right.SetImplicit(true)
clos.List.Set(append([]*Node{nod(OCFUNC, xfunc.Func.Nname, nil)}, clo.Func.Enter.Slice()...))
// Force type conversion from *struct to the func type.
clos = convnop(clos, clo.Type)
// typecheck will insert a PTRLIT node under CONVNOP,
// tag it with escape analysis result.
clos.Left.Esc = clo.Esc
// non-escaping temp to use, if any.
if x := prealloc[clo]; x != nil {
if !types.Identical(typ, x.Type) {
panic("closure type does not match order's assigned type")
}
clos.Left.Right = x
delete(prealloc, clo)
}
return walkexpr(clos, init)
}
func typecheckpartialcall(fn *Node, sym *types.Sym) {
switch fn.Op {
case ODOTINTER, ODOTMETH:
break
default:
Fatalf("invalid typecheckpartialcall")
}
// Create top-level function.
xfunc := makepartialcall(fn, fn.Type, sym)
fn.Func = xfunc.Func
fn.Right = newname(sym)
fn.Op = OCALLPART
fn.Type = xfunc.Type
}
func makepartialcall(fn *Node, t0 *types.Type, meth *types.Sym) *Node {
rcvrtype := fn.Left.Type
sym := methodSymSuffix(rcvrtype, meth, "-fm")
if sym.Uniq() {
return asNode(sym.Def)
}
sym.SetUniq(true)
savecurfn := Curfn
saveLineNo := lineno
Curfn = nil
// Set line number equal to the line number where the method is declared.
var m *types.Field
if lookdot0(meth, rcvrtype, &m, false) == 1 && m.Pos.IsKnown() {
lineno = m.Pos
}
// Note: !m.Pos.IsKnown() happens for method expressions where
// the method is implicitly declared. The Error method of the
// built-in error type is one such method. We leave the line
// number at the use of the method expression in this
// case. See issue 29389.
tfn := nod(OTFUNC, nil, nil)
tfn.List.Set(structargs(t0.Params(), true))
tfn.Rlist.Set(structargs(t0.Results(), false))
disableExport(sym)
xfunc := dclfunc(sym, tfn)
xfunc.Func.SetDupok(true)
xfunc.Func.SetNeedctxt(true)
tfn.Type.SetPkg(t0.Pkg())
// Declare and initialize variable holding receiver.
cv := nod(OCLOSUREVAR, nil, nil)
cv.Type = rcvrtype
cv.Xoffset = Rnd(int64(Widthptr), int64(cv.Type.Align))
ptr := newname(lookup(".this"))
declare(ptr, PAUTO)
ptr.Name.SetUsed(true)
var body []*Node
if rcvrtype.IsPtr() || rcvrtype.IsInterface() {
ptr.Type = rcvrtype
body = append(body, nod(OAS, ptr, cv))
} else {
ptr.Type = types.NewPtr(rcvrtype)
body = append(body, nod(OAS, ptr, nod(OADDR, cv, nil)))
}
call := nod(OCALL, nodSym(OXDOT, ptr, meth), nil)
call.List.Set(paramNnames(tfn.Type))
call.SetIsDDD(tfn.Type.IsVariadic())
if t0.NumResults() != 0 {
n := nod(ORETURN, nil, nil)
n.List.Set1(call)
call = n
}
body = append(body, call)
xfunc.Nbody.Set(body)
funcbody()
xfunc = typecheck(xfunc, ctxStmt)
sym.Def = asTypesNode(xfunc)
xtop = append(xtop, xfunc)
Curfn = savecurfn
lineno = saveLineNo
return xfunc
}
// partialCallType returns the struct type used to hold all the information
// needed in the closure for n (n must be a OCALLPART node).
// The address of a variable of the returned type can be cast to a func.
func partialCallType(n *Node) *types.Type {
t := tostruct([]*Node{
namedfield("F", types.Types[TUINTPTR]),
namedfield("R", n.Left.Type),
})
t.SetNoalg(true)
return t
}
func walkpartialcall(n *Node, init *Nodes) *Node {
// Create closure in the form of a composite literal.
// For x.M with receiver (x) type T, the generated code looks like:
//
// clos = &struct{F uintptr; R T}{M.T·f, x}
//
// Like walkclosure above.
if n.Left.Type.IsInterface() {
// Trigger panic for method on nil interface now.
// Otherwise it happens in the wrapper and is confusing.
n.Left = cheapexpr(n.Left, init)
n.Left = walkexpr(n.Left, nil)
tab := nod(OITAB, n.Left, nil)
tab = typecheck(tab, ctxExpr)
c := nod(OCHECKNIL, tab, nil)
c.SetTypecheck(1)
init.Append(c)
}
typ := partialCallType(n)
clos := nod(OCOMPLIT, nil, nod(ODEREF, typenod(typ), nil))
clos.Esc = n.Esc
clos.Right.SetImplicit(true)
clos.List.Set2(nod(OCFUNC, n.Func.Nname, nil), n.Left)
// Force type conversion from *struct to the func type.
clos = convnop(clos, n.Type)
// The typecheck inside convnop will insert a PTRLIT node under CONVNOP.
// Tag it with escape analysis result.
clos.Left.Esc = n.Esc
// non-escaping temp to use, if any.
if x := prealloc[n]; x != nil {
if !types.Identical(typ, x.Type) {
panic("partial call type does not match order's assigned type")
}
clos.Left.Right = x
delete(prealloc, n)
}
return walkexpr(clos, init)
}
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