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// 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
/*
* select
*/
func typecheckselect(sel *Node) {
var ncase *Node
var n *Node
def := (*Node)(nil)
lno := int(setlineno(sel))
count := 0
typechecklist(sel.Ninit, Etop)
for l := sel.List; l != nil; l = l.Next {
count++
ncase = l.N
setlineno(ncase)
if ncase.Op != OXCASE {
Fatal("typecheckselect %v", Oconv(int(ncase.Op), 0))
}
if ncase.List == nil {
// default
if def != nil {
Yyerror("multiple defaults in select (first at %v)", def.Line())
} else {
def = ncase
}
} else if ncase.List.Next != nil {
Yyerror("select cases cannot be lists")
} else {
n = typecheck(&ncase.List.N, Etop)
ncase.Left = n
ncase.List = nil
setlineno(n)
switch n.Op {
default:
Yyerror("select case must be receive, send or assign recv")
// convert x = <-c into OSELRECV(x, <-c).
// remove implicit conversions; the eventual assignment
// will reintroduce them.
case OAS:
if (n.Right.Op == OCONVNOP || n.Right.Op == OCONVIFACE) && n.Right.Implicit != 0 {
n.Right = n.Right.Left
}
if n.Right.Op != ORECV {
Yyerror("select assignment must have receive on right hand side")
break
}
n.Op = OSELRECV
// convert x, ok = <-c into OSELRECV2(x, <-c) with ntest=ok
case OAS2RECV:
if n.Rlist.N.Op != ORECV {
Yyerror("select assignment must have receive on right hand side")
break
}
n.Op = OSELRECV2
n.Left = n.List.N
n.Ntest = n.List.Next.N
n.List = nil
n.Right = n.Rlist.N
n.Rlist = nil
// convert <-c into OSELRECV(N, <-c)
case ORECV:
n = Nod(OSELRECV, nil, n)
n.Typecheck = 1
ncase.Left = n
case OSEND:
break
}
}
typechecklist(ncase.Nbody, Etop)
}
sel.Xoffset = int64(count)
lineno = int32(lno)
}
func walkselect(sel *Node) {
if sel.List == nil && sel.Xoffset != 0 {
Fatal("double walkselect") // already rewrote
}
lno := int(setlineno(sel))
i := count(sel.List)
// optimization: zero-case select
var init *NodeList
var r *Node
var n *Node
var var_ *Node
var selv *Node
var cas *Node
if i == 0 {
sel.Nbody = list1(mkcall("block", nil, nil))
goto out
}
// optimization: one-case select: single op.
// TODO(rsc): Reenable optimization once order.c can handle it.
// golang.org/issue/7672.
if i == 1 {
cas := sel.List.N
setlineno(cas)
l := cas.Ninit
if cas.Left != nil { // not default:
n := cas.Left
l = concat(l, n.Ninit)
n.Ninit = nil
var ch *Node
switch n.Op {
default:
Fatal("select %v", Oconv(int(n.Op), 0))
// ok already
case OSEND:
ch = n.Left
case OSELRECV,
OSELRECV2:
ch = n.Right.Left
if n.Op == OSELRECV || n.Ntest == nil {
if n.Left == nil {
n = n.Right
} else {
n.Op = OAS
}
break
}
if n.Left == nil {
typecheck(&nblank, Erv|Easgn)
n.Left = nblank
}
n.Op = OAS2
n.List = list(list1(n.Left), n.Ntest)
n.Rlist = list1(n.Right)
n.Right = nil
n.Left = nil
n.Ntest = nil
n.Typecheck = 0
typecheck(&n, Etop)
}
// if ch == nil { block() }; n;
a := Nod(OIF, nil, nil)
a.Ntest = Nod(OEQ, ch, nodnil())
a.Nbody = list1(mkcall("block", nil, &l))
typecheck(&a, Etop)
l = list(l, a)
l = list(l, n)
}
l = concat(l, cas.Nbody)
sel.Nbody = l
goto out
}
// convert case value arguments to addresses.
// this rewrite is used by both the general code and the next optimization.
for l := sel.List; l != nil; l = l.Next {
cas = l.N
setlineno(cas)
n = cas.Left
if n == nil {
continue
}
switch n.Op {
case OSEND:
n.Right = Nod(OADDR, n.Right, nil)
typecheck(&n.Right, Erv)
case OSELRECV,
OSELRECV2:
if n.Op == OSELRECV2 && n.Ntest == nil {
n.Op = OSELRECV
}
if n.Op == OSELRECV2 {
n.Ntest = Nod(OADDR, n.Ntest, nil)
typecheck(&n.Ntest, Erv)
}
if n.Left == nil {
n.Left = nodnil()
} else {
n.Left = Nod(OADDR, n.Left, nil)
typecheck(&n.Left, Erv)
}
}
}
// optimization: two-case select but one is default: single non-blocking op.
if i == 2 && (sel.List.N.Left == nil || sel.List.Next.N.Left == nil) {
var cas *Node
var dflt *Node
if sel.List.N.Left == nil {
cas = sel.List.Next.N
dflt = sel.List.N
} else {
dflt = sel.List.Next.N
cas = sel.List.N
}
n := cas.Left
setlineno(n)
r := Nod(OIF, nil, nil)
r.Ninit = cas.Ninit
switch n.Op {
default:
Fatal("select %v", Oconv(int(n.Op), 0))
// if selectnbsend(c, v) { body } else { default body }
case OSEND:
ch := n.Left
r.Ntest = mkcall1(chanfn("selectnbsend", 2, ch.Type), Types[TBOOL], &r.Ninit, typename(ch.Type), ch, n.Right)
// if c != nil && selectnbrecv(&v, c) { body } else { default body }
case OSELRECV:
r = Nod(OIF, nil, nil)
r.Ninit = cas.Ninit
ch := n.Right.Left
r.Ntest = mkcall1(chanfn("selectnbrecv", 2, ch.Type), Types[TBOOL], &r.Ninit, typename(ch.Type), n.Left, ch)
// if c != nil && selectnbrecv2(&v, c) { body } else { default body }
case OSELRECV2:
r = Nod(OIF, nil, nil)
r.Ninit = cas.Ninit
ch := n.Right.Left
r.Ntest = mkcall1(chanfn("selectnbrecv2", 2, ch.Type), Types[TBOOL], &r.Ninit, typename(ch.Type), n.Left, n.Ntest, ch)
}
typecheck(&r.Ntest, Erv)
r.Nbody = cas.Nbody
r.Nelse = concat(dflt.Ninit, dflt.Nbody)
sel.Nbody = list1(r)
goto out
}
init = sel.Ninit
sel.Ninit = nil
// generate sel-struct
setlineno(sel)
selv = temp(selecttype(int32(sel.Xoffset)))
r = Nod(OAS, selv, nil)
typecheck(&r, Etop)
init = list(init, r)
var_ = conv(conv(Nod(OADDR, selv, nil), Types[TUNSAFEPTR]), Ptrto(Types[TUINT8]))
r = mkcall("newselect", nil, nil, var_, Nodintconst(selv.Type.Width), Nodintconst(sel.Xoffset))
typecheck(&r, Etop)
init = list(init, r)
// register cases
for l := sel.List; l != nil; l = l.Next {
cas = l.N
setlineno(cas)
n = cas.Left
r = Nod(OIF, nil, nil)
r.Ninit = cas.Ninit
cas.Ninit = nil
if n != nil {
r.Ninit = concat(r.Ninit, n.Ninit)
n.Ninit = nil
}
if n == nil {
// selectdefault(sel *byte);
r.Ntest = mkcall("selectdefault", Types[TBOOL], &r.Ninit, var_)
} else {
switch n.Op {
default:
Fatal("select %v", Oconv(int(n.Op), 0))
// selectsend(sel *byte, hchan *chan any, elem *any) (selected bool);
case OSEND:
r.Ntest = mkcall1(chanfn("selectsend", 2, n.Left.Type), Types[TBOOL], &r.Ninit, var_, n.Left, n.Right)
// selectrecv(sel *byte, hchan *chan any, elem *any) (selected bool);
case OSELRECV:
r.Ntest = mkcall1(chanfn("selectrecv", 2, n.Right.Left.Type), Types[TBOOL], &r.Ninit, var_, n.Right.Left, n.Left)
// selectrecv2(sel *byte, hchan *chan any, elem *any, received *bool) (selected bool);
case OSELRECV2:
r.Ntest = mkcall1(chanfn("selectrecv2", 2, n.Right.Left.Type), Types[TBOOL], &r.Ninit, var_, n.Right.Left, n.Left, n.Ntest)
}
}
// selv is no longer alive after use.
r.Nbody = list(r.Nbody, Nod(OVARKILL, selv, nil))
r.Nbody = concat(r.Nbody, cas.Nbody)
r.Nbody = list(r.Nbody, Nod(OBREAK, nil, nil))
init = list(init, r)
}
// run the select
setlineno(sel)
init = list(init, mkcall("selectgo", nil, nil, var_))
sel.Nbody = init
out:
sel.List = nil
walkstmtlist(sel.Nbody)
lineno = int32(lno)
}
// Keep in sync with src/runtime/chan.h.
func selecttype(size int32) *Type {
// TODO(dvyukov): it's possible to generate SudoG and Scase only once
// and then cache; and also cache Select per size.
sudog := Nod(OTSTRUCT, nil, nil)
sudog.List = list(sudog.List, Nod(ODCLFIELD, newname(Lookup("g")), typenod(Ptrto(Types[TUINT8]))))
sudog.List = list(sudog.List, Nod(ODCLFIELD, newname(Lookup("selectdone")), typenod(Ptrto(Types[TUINT8]))))
sudog.List = list(sudog.List, Nod(ODCLFIELD, newname(Lookup("next")), typenod(Ptrto(Types[TUINT8]))))
sudog.List = list(sudog.List, Nod(ODCLFIELD, newname(Lookup("prev")), typenod(Ptrto(Types[TUINT8]))))
sudog.List = list(sudog.List, Nod(ODCLFIELD, newname(Lookup("elem")), typenod(Ptrto(Types[TUINT8]))))
sudog.List = list(sudog.List, Nod(ODCLFIELD, newname(Lookup("releasetime")), typenod(Types[TUINT64])))
sudog.List = list(sudog.List, Nod(ODCLFIELD, newname(Lookup("nrelease")), typenod(Types[TINT32])))
sudog.List = list(sudog.List, Nod(ODCLFIELD, newname(Lookup("waitlink")), typenod(Ptrto(Types[TUINT8]))))
typecheck(&sudog, Etype)
sudog.Type.Noalg = 1
sudog.Type.Local = 1
scase := Nod(OTSTRUCT, nil, nil)
scase.List = list(scase.List, Nod(ODCLFIELD, newname(Lookup("elem")), typenod(Ptrto(Types[TUINT8]))))
scase.List = list(scase.List, Nod(ODCLFIELD, newname(Lookup("chan")), typenod(Ptrto(Types[TUINT8]))))
scase.List = list(scase.List, Nod(ODCLFIELD, newname(Lookup("pc")), typenod(Types[TUINTPTR])))
scase.List = list(scase.List, Nod(ODCLFIELD, newname(Lookup("kind")), typenod(Types[TUINT16])))
scase.List = list(scase.List, Nod(ODCLFIELD, newname(Lookup("so")), typenod(Types[TUINT16])))
scase.List = list(scase.List, Nod(ODCLFIELD, newname(Lookup("receivedp")), typenod(Ptrto(Types[TUINT8]))))
scase.List = list(scase.List, Nod(ODCLFIELD, newname(Lookup("releasetime")), typenod(Types[TUINT64])))
typecheck(&scase, Etype)
scase.Type.Noalg = 1
scase.Type.Local = 1
sel := Nod(OTSTRUCT, nil, nil)
sel.List = list(sel.List, Nod(ODCLFIELD, newname(Lookup("tcase")), typenod(Types[TUINT16])))
sel.List = list(sel.List, Nod(ODCLFIELD, newname(Lookup("ncase")), typenod(Types[TUINT16])))
sel.List = list(sel.List, Nod(ODCLFIELD, newname(Lookup("pollorder")), typenod(Ptrto(Types[TUINT8]))))
sel.List = list(sel.List, Nod(ODCLFIELD, newname(Lookup("lockorder")), typenod(Ptrto(Types[TUINT8]))))
arr := Nod(OTARRAY, Nodintconst(int64(size)), scase)
sel.List = list(sel.List, Nod(ODCLFIELD, newname(Lookup("scase")), arr))
arr = Nod(OTARRAY, Nodintconst(int64(size)), typenod(Ptrto(Types[TUINT8])))
sel.List = list(sel.List, Nod(ODCLFIELD, newname(Lookup("lockorderarr")), arr))
arr = Nod(OTARRAY, Nodintconst(int64(size)), typenod(Types[TUINT16]))
sel.List = list(sel.List, Nod(ODCLFIELD, newname(Lookup("pollorderarr")), arr))
typecheck(&sel, Etype)
sel.Type.Noalg = 1
sel.Type.Local = 1
return sel.Type
}