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cmd/internal/gc: extend escape analysis to pointers in slices
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Modified esc.go to allow slice literals (before append)
to be non-escaping.  Modified tests to account for changes
in escape behavior and to also test the two cases that
were previously not tested.

Also minor cleanups to debug-printing within esc.go

Allocation stats for running compiler
( cd src/html/template;
  for i in {1..5} ; do
     go tool 6g -memprofile=testzz.${i}.prof  -memprofilerate=1 *.go ;
     go tool pprof -alloc_objects -text  testzz.${i}.prof ;
     done ; )
before about 86k allocations
after  about 83k allocations

Fixes golang#8972

Change-Id: Ib61dd70dc74adb40d6f6fdda6eaa4bf7d83481de
Reviewed-on: https://go-review.googlesource.com/10118
Reviewed-by: Russ Cox <[email protected]>
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@dr2chase
dr2chase committed May 18, 2015
1 parent f0dd002 commit a21cf5b
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Showing 4 changed files with 138 additions and 71 deletions.
100 changes: 46 additions & 54 deletions src/cmd/internal/gc/esc.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -387,6 +387,19 @@ type EscState struct {
recursive bool // recursive function or group of mutually recursive functions.
}

// funcSym returns n.Nname.Sym if no nils are encountered along the way.
func funcSym(n *Node) *Sym {
if n == nil || n.Nname == nil {
return nil
}
return n.Nname.Sym
}

// curfnSym returns n.Curfn.Nname.Sym if no nils are encountered along the way.
func curfnSym(n *Node) *Sym {
return funcSym(n.Curfn)
}

func escAnalyze(all *NodeList, recursive bool) {
var es EscState
e := &es
Expand Down Expand Up @@ -428,13 +441,7 @@ func escAnalyze(all *NodeList, recursive bool) {
if Debug['m'] != 0 {
for l := e.noesc; l != nil; l = l.Next {
if l.N.Esc == EscNone {
var tmp *Sym
if l.N.Curfn != nil && l.N.Curfn.Nname != nil {
tmp = l.N.Curfn.Nname.Sym
} else {
tmp = nil
}
Warnl(int(l.N.Lineno), "%v %v does not escape", tmp, Nconv(l.N, obj.FmtShort))
Warnl(int(l.N.Lineno), "%v %v does not escape", curfnSym(l.N), Nconv(l.N, obj.FmtShort))
}
}
}
Expand Down Expand Up @@ -593,13 +600,7 @@ func esc(e *EscState, n *Node, up *Node) {
}

if Debug['m'] > 1 {
var tmp *Sym
if Curfn != nil && Curfn.Nname != nil {
tmp = Curfn.Nname.Sym
} else {
tmp = nil
}
fmt.Printf("%v:[%d] %v esc: %v\n", Ctxt.Line(int(lineno)), e.loopdepth, tmp, n)
fmt.Printf("%v:[%d] %v esc: %v\n", Ctxt.Line(int(lineno)), e.loopdepth, funcSym(Curfn), n)
}

switch n.Op {
Expand Down Expand Up @@ -629,8 +630,12 @@ func esc(e *EscState, n *Node, up *Node) {

// Everything but fixed array is a dereference.
case ORANGE:
if Isfixedarray(n.Type) && n.List != nil && n.List.Next != nil {
escassign(e, n.List.Next.N, n.Right)
if n.List != nil && n.List.Next != nil {
if Isfixedarray(n.Type) {
escassign(e, n.List.Next.N, n.Right)
} else {
escassign(e, n.List.Next.N, addDereference(n.Right))
}
}

case OSWITCH:
Expand Down Expand Up @@ -670,13 +675,7 @@ func esc(e *EscState, n *Node, up *Node) {
// b escapes as well. If we ignore such OSLICEARR, we will conclude
// that b does not escape when b contents do.
if Debug['m'] != 0 {
var tmp *Sym
if n.Curfn != nil && n.Curfn.Nname != nil {
tmp = n.Curfn.Nname.Sym
} else {
tmp = nil
}
Warnl(int(n.Lineno), "%v ignoring self-assignment to %v", tmp, Nconv(n.Left, obj.FmtShort))
Warnl(int(n.Lineno), "%v ignoring self-assignment to %v", curfnSym(n), Nconv(n.Left, obj.FmtShort))
}

break
Expand Down Expand Up @@ -763,7 +762,15 @@ func esc(e *EscState, n *Node, up *Node) {
for ll := n.List.Next; ll != nil; ll = ll.Next {
escassign(e, &e.theSink, ll.N) // lose track of assign to dereference
}
} else {
// append(slice1, slice2...) -- slice2 itself does not escape, but contents do.
slice2 := n.List.Next.N
escassign(e, &e.theSink, addDereference(slice2)) // lose track of assign of dereference
if Debug['m'] > 2 {
Warnl(int(n.Lineno), "%v special treatment of append(slice1, slice2...) %v", curfnSym(n), Nconv(n, obj.FmtShort))
}
}
escassign(e, &e.theSink, addDereference(n.List.N)) // The original elements are now leaked, too

case OCONV, OCONVNOP:
escassign(e, n, n.Left)
Expand All @@ -776,19 +783,15 @@ func esc(e *EscState, n *Node, up *Node) {

case OARRAYLIT:
if Isslice(n.Type) {
n.Esc = EscNone // until proven otherwise
// Slice itself is not leaked until proven otherwise
n.Esc = EscNone
e.noesc = list(e.noesc, n)
n.Escloopdepth = e.loopdepth
}

// Values make it to memory, lose track.
for ll := n.List; ll != nil; ll = ll.Next {
escassign(e, &e.theSink, ll.N.Right)
}
} else {
// Link values to array.
for ll := n.List; ll != nil; ll = ll.Next {
escassign(e, n, ll.N.Right)
}
// Link values to array/slice
for ll := n.List; ll != nil; ll = ll.Next {
escassign(e, n, ll.N.Right)
}

// Link values to struct.
Expand Down Expand Up @@ -909,14 +912,8 @@ func escassign(e *EscState, dst *Node, src *Node) {
}

if Debug['m'] > 1 {
var tmp *Sym
if Curfn != nil && Curfn.Nname != nil {
tmp = Curfn.Nname.Sym
} else {
tmp = nil
}
fmt.Printf("%v:[%d] %v escassign: %v(%v)[%v] = %v(%v)[%v]\n",
Ctxt.Line(int(lineno)), e.loopdepth, tmp,
Ctxt.Line(int(lineno)), e.loopdepth, funcSym(Curfn),
Nconv(dst, obj.FmtShort), Jconv(dst, obj.FmtShort), Oconv(int(dst.Op), 0),
Nconv(src, obj.FmtShort), Jconv(src, obj.FmtShort), Oconv(int(src.Op), 0))
}
Expand Down Expand Up @@ -1038,12 +1035,15 @@ func escassign(e *EscState, dst *Node, src *Node) {

case OAPPEND:
// Append returns first argument.
// Subsequent arguments are already leaked because they are operands to append.
escassign(e, dst, src.List.N)

case OINDEX:
// Index of array preserves input value.
if Isfixedarray(src.Left.Type) {
escassign(e, dst, src.Left)
} else {
escflows(e, dst, src)
}

// Might be pointer arithmetic, in which case
Expand Down Expand Up @@ -1510,13 +1510,7 @@ func escflood(e *EscState, dst *Node) {
}

if Debug['m'] > 1 {
var tmp *Sym
if dst.Curfn != nil && dst.Curfn.Nname != nil {
tmp = dst.Curfn.Nname.Sym
} else {
tmp = nil
}
fmt.Printf("\nescflood:%d: dst %v scope:%v[%d]\n", walkgen, Nconv(dst, obj.FmtShort), tmp, dst.Escloopdepth)
fmt.Printf("\nescflood:%d: dst %v scope:%v[%d]\n", walkgen, Nconv(dst, obj.FmtShort), curfnSym(dst), dst.Escloopdepth)
}

for l := dst.Escflowsrc; l != nil; l = l.Next {
Expand Down Expand Up @@ -1548,14 +1542,8 @@ func escwalk(e *EscState, level Level, dst *Node, src *Node) {
src.Esclevel = level

if Debug['m'] > 1 {
var tmp *Sym
if src.Curfn != nil && src.Curfn.Nname != nil {
tmp = src.Curfn.Nname.Sym
} else {
tmp = nil
}
fmt.Printf("escwalk: level:%d depth:%d %.*s op=%v %v(%v) scope:%v[%d]\n",
level, e.pdepth, e.pdepth, "\t\t\t\t\t\t\t\t\t\t", Oconv(int(src.Op), 0), Nconv(src, obj.FmtShort), Jconv(src, obj.FmtShort), tmp, src.Escloopdepth)
level, e.pdepth, e.pdepth, "\t\t\t\t\t\t\t\t\t\t", Oconv(int(src.Op), 0), Nconv(src, obj.FmtShort), Jconv(src, obj.FmtShort), curfnSym(src), src.Escloopdepth)
}

e.pdepth++
Expand Down Expand Up @@ -1657,6 +1645,10 @@ func escwalk(e *EscState, level Level, dst *Node, src *Node) {
if Isfixedarray(src.Type) {
break
}
for ll := src.List; ll != nil; ll = ll.Next {
escwalk(e, level.dec(), dst, ll.N.Right)
}

fallthrough

case ODDDARG,
Expand Down
14 changes: 7 additions & 7 deletions test/escape2.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -787,7 +787,7 @@ func foo93(c chan *int) *int { // ERROR "foo93 c does not escape$"
}

// does not leak m
func foo94(m map[*int]*int, b bool) *int { // ERROR "foo94 m does not escape$"
func foo94(m map[*int]*int, b bool) *int { // ERROR "leaking param: m to result ~r2 level=1"
for k, v := range m {
if b {
return k
Expand All @@ -802,8 +802,8 @@ func foo95(m map[*int]*int, x *int) { // ERROR "foo95 m does not escape$" "leaki
m[x] = x
}

// does not leak m
func foo96(m []*int) *int { // ERROR "foo96 m does not escape$"
// does not leak m but does leak content
func foo96(m []*int) *int { // ERROR "leaking param: m to result ~r1 level=1"
return m[0]
}

Expand All @@ -823,7 +823,7 @@ func foo99(m *[1]*int) []*int { // ERROR "leaking param: m to result ~r1 level=0
}

// does not leak m
func foo100(m []*int) *int { // ERROR "foo100 m does not escape$"
func foo100(m []*int) *int { // ERROR "leaking param: m to result ~r1 level=1"
for _, v := range m {
return v
}
Expand Down Expand Up @@ -863,8 +863,8 @@ func foo104(x []*int) { // ERROR "foo104 x does not escape$"
copy(y, x)
}

// does not leak x
func foo105(x []*int) { // ERROR "foo105 x does not escape$"
// does not leak x but does leak content
func foo105(x []*int) { // ERROR "leaking param content: x"
_ = append(y, x...)
}

Expand Down Expand Up @@ -894,7 +894,7 @@ func foo110(x *int) *int { // ERROR "leaking param: x$"
return m[nil]
}

func foo111(x *int) *int { // ERROR "leaking param: x$"
func foo111(x *int) *int { // ERROR "leaking param: x to result ~r1 level=0"
m := []*int{x} // ERROR "foo111 \[\]\*int literal does not escape$"
return m[0]
}
Expand Down
14 changes: 7 additions & 7 deletions test/escape2n.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -787,7 +787,7 @@ func foo93(c chan *int) *int { // ERROR "foo93 c does not escape$"
}

// does not leak m
func foo94(m map[*int]*int, b bool) *int { // ERROR "foo94 m does not escape$"
func foo94(m map[*int]*int, b bool) *int { // ERROR "leaking param: m to result ~r2 level=1"
for k, v := range m {
if b {
return k
Expand All @@ -802,8 +802,8 @@ func foo95(m map[*int]*int, x *int) { // ERROR "foo95 m does not escape$" "leaki
m[x] = x
}

// does not leak m
func foo96(m []*int) *int { // ERROR "foo96 m does not escape$"
// does not leak m but does leak content
func foo96(m []*int) *int { // ERROR "leaking param: m to result ~r1 level=1"
return m[0]
}

Expand All @@ -823,7 +823,7 @@ func foo99(m *[1]*int) []*int { // ERROR "leaking param: m to result ~r1 level=0
}

// does not leak m
func foo100(m []*int) *int { // ERROR "foo100 m does not escape$"
func foo100(m []*int) *int { // ERROR "leaking param: m to result ~r1 level=1"
for _, v := range m {
return v
}
Expand Down Expand Up @@ -863,8 +863,8 @@ func foo104(x []*int) { // ERROR "foo104 x does not escape$"
copy(y, x)
}

// does not leak x
func foo105(x []*int) { // ERROR "foo105 x does not escape$"
// does not leak x but does leak content
func foo105(x []*int) { // ERROR "leaking param content: x"
_ = append(y, x...)
}

Expand Down Expand Up @@ -894,7 +894,7 @@ func foo110(x *int) *int { // ERROR "leaking param: x$"
return m[nil]
}

func foo111(x *int) *int { // ERROR "leaking param: x$"
func foo111(x *int) *int { // ERROR "leaking param: x to result ~r1 level=0"
m := []*int{x} // ERROR "foo111 \[\]\*int literal does not escape$"
return m[0]
}
Expand Down
81 changes: 78 additions & 3 deletions test/escape_slice.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,11 @@

package escape

import (
"os"
"strings"
)

var sink interface{}

func slice0() {
Expand Down Expand Up @@ -71,9 +76,8 @@ func slice7() *int {
}

func slice8() {
// BAD: i should not escape here
i := 0 // ERROR "moved to heap: i"
s := []*int{&i} // ERROR "&i escapes to heap" "literal does not escape"
i := 0
s := []*int{&i} // ERROR "&i does not escape" "literal does not escape"
_ = s
}

Expand All @@ -88,3 +92,74 @@ func slice10() []*int {
s := []*int{&i} // ERROR "&i escapes to heap" "literal escapes to heap"
return s
}

func envForDir(dir string) []string { // ERROR "dir does not escape"
env := os.Environ()
return mergeEnvLists([]string{"PWD=" + dir}, env) // ERROR ".PWD=. \+ dir escapes to heap" "\[\]string literal does not escape"
}

func mergeEnvLists(in, out []string) []string { // ERROR "leaking param content: in" "leaking param content: out" "leaking param: out to result ~r2 level=0"
NextVar:
for _, inkv := range in {
k := strings.SplitAfterN(inkv, "=", 2)[0]
for i, outkv := range out {
if strings.HasPrefix(outkv, k) {
out[i] = inkv
continue NextVar
}
}
out = append(out, inkv)
}
return out
}

const (
IPv4len = 4
IPv6len = 16
)

var v4InV6Prefix = []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff}

func IPv4(a, b, c, d byte) IP {
p := make(IP, IPv6len) // ERROR "make\(IP, IPv6len\) escapes to heap"
copy(p, v4InV6Prefix)
p[12] = a
p[13] = b
p[14] = c
p[15] = d
return p
}

type IP []byte

type IPAddr struct {
IP IP
Zone string // IPv6 scoped addressing zone
}

type resolveIPAddrTest struct {
network string
litAddrOrName string
addr *IPAddr
err error
}

var resolveIPAddrTests = []resolveIPAddrTest{
{"ip", "127.0.0.1", &IPAddr{IP: IPv4(127, 0, 0, 1)}, nil},
{"ip4", "127.0.0.1", &IPAddr{IP: IPv4(127, 0, 0, 1)}, nil},
{"ip4:icmp", "127.0.0.1", &IPAddr{IP: IPv4(127, 0, 0, 1)}, nil},
}

func setupTestData() {
resolveIPAddrTests = append(resolveIPAddrTests,
[]resolveIPAddrTest{ // ERROR "\[\]resolveIPAddrTest literal does not escape"
{"ip",
"localhost",
&IPAddr{IP: IPv4(127, 0, 0, 1)}, // ERROR "&IPAddr literal escapes to heap"
nil},
{"ip4",
"localhost",
&IPAddr{IP: IPv4(127, 0, 0, 1)}, // ERROR "&IPAddr literal escapes to heap"
nil},
}...)
}

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