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cmd/compile: remove some more gotos in gc

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Split typecheckrange into two, separating the bigger chunk of code that
takes care of the range expression. It had to sometimes exit early,
which was done via a goto in the larger func. This lets us simplify many
declarations and the flow of the code. While at it, also replace the
toomany int with a bool.

In the case of walkselect, split it into two funcs too since using a
defer for all the trailing work would be a bit much. It also lets us
simplify the declarations and the flow of the code, since now
walkselectcases has a narrower scope and straightforward signature.

Also replace the gotos in typecheckaste with a lineno defer.

Passes toolstash -cmp on std cmd.

Change-Id: Iacfaa0a34c987c44f180a792c473558785cf6823
Reviewed-on: https://go-review.googlesource.com/72374
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This commit is contained in:
Daniel Martí 2017-10-22 17:18:51 +01:00
parent 1722a2d79d
commit 7f88d3c121
3 changed files with 75 additions and 88 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

53
src/cmd/compile/internal/gc/range.go
View File

@ -13,14 +13,6 @@ import (
// range
func typecheckrange(n *Node) {
var toomany bool
var why string
var t1 *types.Type
var t2 *types.Type
var v1 *Node
var v2 *Node
var ls []*Node
// Typechecking order is important here:
// 0. first typecheck range expression (slice/map/chan),
// it is evaluated only once and so logically it is not part of the loop.
@ -30,15 +22,31 @@ func typecheckrange(n *Node) {
// 2. decldepth++ to denote loop body.
// 3. typecheck body.
// 4. decldepth--.
typecheckrangeExpr(n)
// second half of dance, the first half being typecheckrangeExpr
n.SetTypecheck(1)
ls := n.List.Slice()
for i1, n1 := range ls {
if n1.Typecheck() == 0 {
ls[i1] = typecheck(ls[i1], Erv|Easgn)
}
}
decldepth++
typecheckslice(n.Nbody.Slice(), Etop)
decldepth--
}
func typecheckrangeExpr(n *Node) {
n.Right = typecheck(n.Right, Erv)
t := n.Right.Type
if t == nil {
goto out
return
}
// delicate little dance. see typecheckas2
ls = n.List.Slice()
ls := n.List.Slice()
for i1, n1 := range ls {
if n1.Name == nil || n1.Name.Defn != n {
ls[i1] = typecheck(ls[i1], Erv|Easgn)
@ -50,11 +58,12 @@ func typecheckrange(n *Node) {
}
n.Type = t
toomany = false
var t1, t2 *types.Type
toomany := false
switch t.Etype {
default:
yyerrorl(n.Pos, "cannot range over %L", n.Right)
goto out
return
case TARRAY, TSLICE:
t1 = types.Types[TINT]
@ -67,7 +76,7 @@ func typecheckrange(n *Node) {
case TCHAN:
if !t.ChanDir().CanRecv() {
yyerrorl(n.Pos, "invalid operation: range %v (receive from send-only type %v)", n.Right, n.Right.Type)
goto out
return
}
t1 = t.Elem()
@ -85,11 +94,10 @@ func typecheckrange(n *Node) {
yyerrorl(n.Pos, "too many variables in range")
}
v1 = nil
var v1, v2 *Node
if n.List.Len() != 0 {
v1 = n.List.First()
}
v2 = nil
if n.List.Len() > 1 {
v2 = n.List.Second()
}
@ -105,6 +113,7 @@ func typecheckrange(n *Node) {
v2 = nil
}
var why string
if v1 != nil {
if v1.Name != nil && v1.Name.Defn == n {
v1.Type = t1
@ -122,20 +131,6 @@ func typecheckrange(n *Node) {
}
checkassign(n, v2)
}
// second half of dance
out:
n.SetTypecheck(1)
ls = n.List.Slice()
for i1, n1 := range ls {
if n1.Typecheck() == 0 {
ls[i1] = typecheck(ls[i1], Erv|Easgn)
}
}
decldepth++
typecheckslice(n.Nbody.Slice(), Etop)
decldepth--
}
func cheapComputableIndex(width int64) bool {

88
src/cmd/compile/internal/gc/select.go
View File

@ -78,35 +78,41 @@ func typecheckselect(sel *Node) {
typecheckslice(ncase.Nbody.Slice(), Etop)
}
sel.Xoffset = int64(sel.List.Len())
lineno = lno
}
func walkselect(sel *Node) {
if sel.List.Len() == 0 && sel.Xoffset != 0 {
Fatalf("double walkselect") // already rewrote
lno := setlineno(sel)
if sel.Nbody.Len() != 0 {
Fatalf("double walkselect")
}
lno := setlineno(sel)
i := sel.List.Len()
init := sel.Ninit.Slice()
sel.Ninit.Set(nil)
init = append(init, walkselectcases(&sel.List)...)
sel.List.Set(nil)
sel.Nbody.Set(init)
walkstmtlist(sel.Nbody.Slice())
lineno = lno
}
func walkselectcases(cases *Nodes) []*Node {
n := cases.Len()
sellineno := lineno
// optimization: zero-case select
var init []*Node
var r *Node
var n *Node
var var_ *Node
var selv *Node
var chosen *Node
if i == 0 {
sel.Nbody.Set1(mkcall("block", nil, nil))
goto out
if n == 0 {
return []*Node{mkcall("block", nil, nil)}
}
// optimization: one-case select: single op.
// TODO(rsc): Reenable optimization once order.go can handle it.
// golang.org/issue/7672.
if i == 1 {
cas := sel.List.First()
if n == 1 {
cas := cases.First()
setlineno(cas)
l := cas.Ninit.Slice()
if cas.Left != nil { // not default:
@ -161,15 +167,14 @@ func walkselect(sel *Node) {
l = append(l, cas.Nbody.Slice()...)
l = append(l, nod(OBREAK, nil, nil))
sel.Nbody.Set(l)
goto out
return l
}
// convert case value arguments to addresses.
// this rewrite is used by both the general code and the next optimization.
for _, cas := range sel.List.Slice() {
for _, cas := range cases.Slice() {
setlineno(cas)
n = cas.Left
n := cas.Left
if n == nil {
continue
}
@ -197,15 +202,15 @@ func walkselect(sel *Node) {
}
// optimization: two-case select but one is default: single non-blocking op.
if i == 2 && (sel.List.First().Left == nil || sel.List.Second().Left == nil) {
if n == 2 && (cases.First().Left == nil || cases.Second().Left == nil) {
var cas *Node
var dflt *Node
if sel.List.First().Left == nil {
cas = sel.List.Second()
dflt = sel.List.First()
if cases.First().Left == nil {
cas = cases.Second()
dflt = cases.First()
} else {
dflt = sel.List.Second()
cas = sel.List.First()
dflt = cases.Second()
cas = cases.First()
}
n := cas.Left
@ -239,26 +244,24 @@ func walkselect(sel *Node) {
r.Left = typecheck(r.Left, Erv)
r.Nbody.Set(cas.Nbody.Slice())
r.Rlist.Set(append(dflt.Ninit.Slice(), dflt.Nbody.Slice()...))
sel.Nbody.Set2(r, nod(OBREAK, nil, nil))
goto out
return []*Node{r, nod(OBREAK, nil, nil)}
}
init = sel.Ninit.Slice()
sel.Ninit.Set(nil)
var init []*Node
// generate sel-struct
setlineno(sel)
selv = temp(selecttype(sel.Xoffset))
r = nod(OAS, selv, nil)
lineno = sellineno
selv := temp(selecttype(int64(n)))
r := nod(OAS, selv, nil)
r = typecheck(r, Etop)
init = append(init, r)
var_ = conv(conv(nod(OADDR, selv, nil), types.Types[TUNSAFEPTR]), types.NewPtr(types.Types[TUINT8]))
r = mkcall("newselect", nil, nil, var_, nodintconst(selv.Type.Width), nodintconst(sel.Xoffset))
var_ := conv(conv(nod(OADDR, selv, nil), types.Types[TUNSAFEPTR]), types.NewPtr(types.Types[TUINT8]))
r = mkcall("newselect", nil, nil, var_, nodintconst(selv.Type.Width), nodintconst(int64(n)))
r = typecheck(r, Etop)
init = append(init, r)
// register cases
for _, cas := range sel.List.Slice() {
for _, cas := range cases.Slice() {
setlineno(cas)
init = append(init, cas.Ninit.Slice()...)
@ -290,8 +293,8 @@ func walkselect(sel *Node) {
}
// run the select
setlineno(sel)
chosen = temp(types.Types[TINT])
lineno = sellineno
chosen := temp(types.Types[TINT])
r = nod(OAS, chosen, mkcall("selectgo", types.Types[TINT], nil, var_))
r = typecheck(r, Etop)
init = append(init, r)
@ -300,7 +303,7 @@ func walkselect(sel *Node) {
init = append(init, nod(OVARKILL, selv, nil))
// dispatch cases
for i, cas := range sel.List.Slice() {
for i, cas := range cases.Slice() {
setlineno(cas)
cond := nod(OEQ, chosen, nodintconst(int64(i)))
@ -312,12 +315,7 @@ func walkselect(sel *Node) {
init = append(init, r)
}
sel.Nbody.Set(init)
out:
sel.List.Set(nil)
walkstmtlist(sel.Nbody.Slice())
lineno = lno
return init
}
// Keep in sync with src/runtime/select.go.

22
src/cmd/compile/internal/gc/typecheck.go
View File

@ -2547,18 +2547,18 @@ func hasddd(t *types.Type) bool {
// typecheck assignment: type list = expression list
func typecheckaste(op Op, call *Node, isddd bool, tstruct *types.Type, nl Nodes, desc func() string) {
var t *types.Type
var n *Node
var n1 int
var n2 int
var i int
lno := lineno
defer func() { lineno = lno }()
if tstruct.Broke() {
goto out
return
}
n = nil
var n *Node
if nl.Len() == 1 {
n = nl.First()
if n.Type != nil && n.Type.IsFuncArgStruct() {
@ -2587,7 +2587,7 @@ func typecheckaste(op Op, call *Node, isddd bool, tstruct *types.Type, nl Nodes,
}
}
}
goto out
return
}
if i >= len(rfs) {
@ -2606,7 +2606,7 @@ func typecheckaste(op Op, call *Node, isddd bool, tstruct *types.Type, nl Nodes,
if len(rfs) > len(lfs) {
goto toomany
}
goto out
return
}
}
@ -2650,7 +2650,7 @@ func typecheckaste(op Op, call *Node, isddd bool, tstruct *types.Type, nl Nodes,
if n.Type != nil {
nl.SetIndex(i, assignconvfn(n, t, desc))
}
goto out
return
}
for ; i < nl.Len(); i++ {
@ -2660,8 +2660,7 @@ func typecheckaste(op Op, call *Node, isddd bool, tstruct *types.Type, nl Nodes,
nl.SetIndex(i, assignconvfn(n, t.Elem(), desc))
}
}
goto out
return
}
if i >= nl.Len() {
@ -2685,9 +2684,6 @@ func typecheckaste(op Op, call *Node, isddd bool, tstruct *types.Type, nl Nodes,
yyerror("invalid use of ... in %v", op)
}
}
out:
lineno = lno
return
notenough:
@ -2709,8 +2705,7 @@ notenough:
n.SetDiag(true)
}
}
goto out
return
toomany:
details := errorDetails(nl, tstruct, isddd)
@ -2719,7 +2714,6 @@ toomany:
} else {
yyerror("too many arguments to %v%s", op, details)
}
goto out
}
func errorDetails(nl Nodes, tstruct *types.Type, isddd bool) string {