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go/test/live.go
Josh Bleecher Snyder 77a2113925 cmd/gc: evaluate concrete == interface without allocating 
Consider an interface value i of type I and concrete value c of type C.

Prior to this CL, i==c was evaluated as
	I(c) == i

Evaluating I(c) can allocate.

This CL changes the evaluation of i==c to
	x, ok := i.(C); ok && x == c

The new generated code is shorter and does not allocate directly.

If C is small, as it is in every instance in the stdlib,
the new code also uses less stack space
and makes one runtime call instead of two.

If C is very large, the original implementation is used.
The cutoff for "very large" is 1<<16,
following the stack vs heap cutoff used elsewhere.

This kind of comparison occurs in 38 places in the stdlib,
mostly in the net and os packages.

benchmark                     old ns/op     new ns/op     delta
BenchmarkEqEfaceConcrete      29.5          7.92          -73.15%
BenchmarkEqIfaceConcrete      32.1          7.90          -75.39%
BenchmarkNeEfaceConcrete      29.9          7.90          -73.58%
BenchmarkNeIfaceConcrete      35.9          7.90          -77.99%

Fixes #9370.

Change-Id: I7c4555950bcd6406ee5c613be1f2128da2c9a2b7
Reviewed-on: https://go-review.googlesource.com/2096
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
2015-02-12 22:23:38 +00:00

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// errorcheck -0 -l -live -wb=0
// Copyright 2014 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.
// liveness tests with inlining disabled.
// see also live2.go.
package main
func printnl()
//go:noescape
func printpointer(**int)
//go:noescape
func printintpointer(*int)
//go:noescape
func printstringpointer(*string)
//go:noescape
func printstring(string)
//go:noescape
func printbytepointer(*byte)
func printint(int)
func f1() {
var x *int
printpointer(&x) // ERROR "live at call to printpointer: x$"
printpointer(&x) // ERROR "live at call to printpointer: x$"
}
func f2(b bool) {
if b {
printint(0) // nothing live here
return
}
var x *int
printpointer(&x) // ERROR "live at call to printpointer: x$"
printpointer(&x) // ERROR "live at call to printpointer: x$"
}
func f3(b bool) {
// Because x and y are ambiguously live, they appear
// live throughout the function, to avoid being poisoned
// in GODEBUG=gcdead=1 mode.
printint(0) // ERROR "live at call to printint: x y$"
if b == false {
printint(0) // ERROR "live at call to printint: x y$"
return
}
if b {
var x *int
printpointer(&x) // ERROR "live at call to printpointer: x y$"
printpointer(&x) // ERROR "live at call to printpointer: x y$"
} else {
var y *int
printpointer(&y) // ERROR "live at call to printpointer: x y$"
printpointer(&y) // ERROR "live at call to printpointer: x y$"
}
printint(0) // ERROR "live at call to printint: x y$" "x \(type \*int\) is ambiguously live" "y \(type \*int\) is ambiguously live"
}
// The old algorithm treated x as live on all code that
// could flow to a return statement, so it included the
// function entry and code above the declaration of x
// but would not include an indirect use of x in an infinite loop.
// Check that these cases are handled correctly.
func f4(b1, b2 bool) { // x not live here
if b2 {
printint(0) // x not live here
return
}
var z **int
x := new(int)
*x = 42
z = &x
printint(**z) // ERROR "live at call to printint: x z$"
if b2 {
printint(1) // ERROR "live at call to printint: x$"
return
}
for {
printint(**z) // ERROR "live at call to printint: x z$"
}
}
func f5(b1 bool) {
var z **int
if b1 {
x := new(int)
*x = 42
z = &x
} else {
y := new(int)
*y = 54
z = &y
}
printint(**z) // ERROR "live at call to printint: x y$" "x \(type \*int\) is ambiguously live" "y \(type \*int\) is ambiguously live"
}
// confusion about the _ result used to cause spurious "live at entry to f6: _".
func f6() (_, y string) {
y = "hello"
return
}
// confusion about addressed results used to cause "live at entry to f7: x".
func f7() (x string) {
_ = &x
x = "hello"
return
}
// ignoring block returns used to cause "live at entry to f8: x, y".
func f8() (x, y string) {
return g8()
}
func g8() (string, string)
// ignoring block assignments used to cause "live at entry to f9: x"
// issue 7205
var i9 interface{}
func f9() bool {
g8()
x := i9
return x != interface{}(99.0i) // ERROR "live at call to convT2E: x"
}
// liveness formerly confused by UNDEF followed by RET,
// leading to "live at entry to f10: ~r1" (unnamed result).
func f10() string {
panic(1)
}
// liveness formerly confused by select, thinking runtime.selectgo
// can return to next instruction; it always jumps elsewhere.
// note that you have to use at least two cases in the select
// to get a true select; smaller selects compile to optimized helper functions.
var c chan *int
var b bool
// this used to have a spurious "live at entry to f11a: ~r0"
func f11a() *int {
select { // ERROR "live at call to newselect: autotmp" "live at call to selectgo: autotmp"
case <-c: // ERROR "live at call to selectrecv: autotmp"
return nil
case <-c: // ERROR "live at call to selectrecv: autotmp"
return nil
}
}
func f11b() *int {
p := new(int)
if b {
// At this point p is dead: the code here cannot
// get to the bottom of the function.
// This used to have a spurious "live at call to printint: p".
printint(1) // nothing live here!
select { // ERROR "live at call to newselect: autotmp" "live at call to selectgo: autotmp"
case <-c: // ERROR "live at call to selectrecv: autotmp"
return nil
case <-c: // ERROR "live at call to selectrecv: autotmp"
return nil
}
}
println(*p)
return nil
}
func f11c() *int {
p := new(int)
if b {
// Unlike previous, the cases in this select fall through,
// so we can get to the println, so p is not dead.
printint(1) // ERROR "live at call to printint: p"
select { // ERROR "live at call to newselect: autotmp.* p" "live at call to selectgo: autotmp.* p"
case <-c: // ERROR "live at call to selectrecv: autotmp.* p"
case <-c: // ERROR "live at call to selectrecv: autotmp.* p"
}
}
println(*p)
return nil
}
// similarly, select{} does not fall through.
// this used to have a spurious "live at entry to f12: ~r0".
func f12() *int {
if b {
select {}
} else {
return nil
}
}
// incorrectly placed VARDEF annotations can cause missing liveness annotations.
// this used to be missing the fact that s is live during the call to g13 (because it is
// needed for the call to h13).
func f13() {
s := "hello"
s = h13(s, g13(s)) // ERROR "live at call to g13: s"
}
func g13(string) string
func h13(string, string) string
// more incorrectly placed VARDEF.
func f14() {
x := g14()
printstringpointer(&x) // ERROR "live at call to printstringpointer: x"
}
func g14() string
func f15() {
var x string
_ = &x
x = g15() // ERROR "live at call to g15: x"
printstring(x) // ERROR "live at call to printstring: x"
}
func g15() string
// Checking that various temporaries do not persist or cause
// ambiguously live values that must be zeroed.
// The exact temporary names are inconsequential but we are
// trying to check that there is only one at any given site,
// and also that none show up in "ambiguously live" messages.
var m map[string]int
func f16() {
if b {
delete(m, "hi") // ERROR "live at call to mapdelete: autotmp_[0-9]+$"
}
delete(m, "hi") // ERROR "live at call to mapdelete: autotmp_[0-9]+$"
delete(m, "hi") // ERROR "live at call to mapdelete: autotmp_[0-9]+$"
}
var m2s map[string]*byte
var m2 map[[2]string]*byte
var x2 [2]string
var bp *byte
func f17a() {
// value temporary only
if b {
m2[x2] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+$"
}
m2[x2] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+$"
m2[x2] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+$"
}
func f17b() {
// key temporary only
if b {
m2s["x"] = bp // ERROR "live at call to mapassign1: autotmp_[0-9]+$"
}
m2s["x"] = bp // ERROR "live at call to mapassign1: autotmp_[0-9]+$"
m2s["x"] = bp // ERROR "live at call to mapassign1: autotmp_[0-9]+$"
}
func f17c() {
// key and value temporaries
if b {
m2s["x"] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+ autotmp_[0-9]+$"
}
m2s["x"] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+ autotmp_[0-9]+$"
m2s["x"] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+ autotmp_[0-9]+$"
}
func g18() [2]string
func f18() {
// key temporary for mapaccess.
// temporary introduced by orderexpr.
var z *byte
if b {
z = m2[g18()] // ERROR "live at call to mapaccess1: autotmp_[0-9]+$"
}
z = m2[g18()] // ERROR "live at call to mapaccess1: autotmp_[0-9]+$"
z = m2[g18()] // ERROR "live at call to mapaccess1: autotmp_[0-9]+$"
printbytepointer(z)
}
var ch chan *byte
func f19() {
// dest temporary for channel receive.
var z *byte
if b {
z = <-ch // ERROR "live at call to chanrecv1: autotmp_[0-9]+$"
}
z = <-ch // ERROR "live at call to chanrecv1: autotmp_[0-9]+$"
z = <-ch // ERROR "live at call to chanrecv1: autotmp_[0-9]+$"
printbytepointer(z)
}
func f20() {
// src temporary for channel send
if b {
ch <- nil // ERROR "live at call to chansend1: autotmp_[0-9]+$"
}
ch <- nil // ERROR "live at call to chansend1: autotmp_[0-9]+$"
ch <- nil // ERROR "live at call to chansend1: autotmp_[0-9]+$"
}
func f21() {
// key temporary for mapaccess using array literal key.
var z *byte
if b {
z = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess1: autotmp_[0-9]+$"
}
z = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess1: autotmp_[0-9]+$"
z = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess1: autotmp_[0-9]+$"
printbytepointer(z)
}
func f23() {
// key temporary for two-result map access using array literal key.
var z *byte
var ok bool
if b {
z, ok = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess2: autotmp_[0-9]+$"
}
z, ok = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess2: autotmp_[0-9]+$"
z, ok = m2[[2]string{"x", "y"}] // ERROR "live at call to mapaccess2: autotmp_[0-9]+$"
printbytepointer(z)
print(ok)
}
func f24() {
// key temporary for map access using array literal key.
// value temporary too.
if b {
m2[[2]string{"x", "y"}] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+ autotmp_[0-9]+$"
}
m2[[2]string{"x", "y"}] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+ autotmp_[0-9]+$"
m2[[2]string{"x", "y"}] = nil // ERROR "live at call to mapassign1: autotmp_[0-9]+ autotmp_[0-9]+$"
}
// defer should not cause spurious ambiguously live variables
func f25(b bool) {
defer g25()
if b {
return
}
var x string
_ = &x
x = g15() // ERROR "live at call to g15: x"
printstring(x) // ERROR "live at call to printstring: x"
} // ERROR "live at call to deferreturn: x"
func g25()
// non-escaping ... slices passed to function call should die on return,
// so that the temporaries do not stack and do not cause ambiguously
// live variables.
func f26(b bool) {
if b {
print26((*int)(nil), (*int)(nil), (*int)(nil)) // ERROR "live at call to print26: autotmp_[0-9]+$"
}
print26((*int)(nil), (*int)(nil), (*int)(nil)) // ERROR "live at call to print26: autotmp_[0-9]+$"
print26((*int)(nil), (*int)(nil), (*int)(nil)) // ERROR "live at call to print26: autotmp_[0-9]+$"
printnl()
}
//go:noescape
func print26(...interface{})
// non-escaping closures passed to function call should die on return
func f27(b bool) {
x := 0
if b {
call27(func() { x++ }) // ERROR "live at call to call27: autotmp_[0-9]+$"
}
call27(func() { x++ }) // ERROR "live at call to call27: autotmp_[0-9]+$"
call27(func() { x++ }) // ERROR "live at call to call27: autotmp_[0-9]+$"
printnl()
}
// but defer does escape to later execution in the function
func f27defer(b bool) {
x := 0
if b {
defer call27(func() { x++ }) // ERROR "live at call to deferproc: autotmp_[0-9]+$" "live at call to deferreturn: autotmp_[0-9]+$"
}
defer call27(func() { x++ }) // ERROR "live at call to deferproc: autotmp_[0-9]+ autotmp_[0-9]+$" "live at call to deferreturn: autotmp_[0-9]+ autotmp_[0-9]+$" "ambiguously live"
printnl() // ERROR "live at call to printnl: autotmp_[0-9]+ autotmp_[0-9]+$"
} // ERROR "live at call to deferreturn: autotmp_[0-9]+ autotmp_[0-9]+$"
// and newproc (go) escapes to the heap
func f27go(b bool) {
x := 0
if b {
go call27(func() { x++ }) // ERROR "live at call to newobject: &x" "live at call to newproc: &x$"
}
go call27(func() { x++ }) // ERROR "live at call to newobject: &x"
printnl()
}
//go:noescape
func call27(func())
// concatstring slice should die on return
var s1, s2, s3, s4, s5, s6, s7, s8, s9, s10 string
func f28(b bool) {
if b {
printstring(s1 + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9 + s10) // ERROR "live at call to concatstrings: autotmp_[0-9]+$" "live at call to printstring: autotmp_[0-9]+$"
}
printstring(s1 + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9 + s10) // ERROR "live at call to concatstrings: autotmp_[0-9]+$" "live at call to printstring: autotmp_[0-9]+$"
printstring(s1 + s2 + s3 + s4 + s5 + s6 + s7 + s8 + s9 + s10) // ERROR "live at call to concatstrings: autotmp_[0-9]+$" "live at call to printstring: autotmp_[0-9]+$"
}
// map iterator should die on end of range loop
func f29(b bool) {
if b {
for k := range m { // ERROR "live at call to mapiterinit: autotmp_[0-9]+$" "live at call to mapiternext: autotmp_[0-9]+$"
printstring(k) // ERROR "live at call to printstring: autotmp_[0-9]+$"
}
}
for k := range m { // ERROR "live at call to mapiterinit: autotmp_[0-9]+$" "live at call to mapiternext: autotmp_[0-9]+$"
printstring(k) // ERROR "live at call to printstring: autotmp_[0-9]+$"
}
for k := range m { // ERROR "live at call to mapiterinit: autotmp_[0-9]+$" "live at call to mapiternext: autotmp_[0-9]+$"
printstring(k) // ERROR "live at call to printstring: autotmp_[0-9]+$"
}
}
// copy of array of pointers should die at end of range loop
var ptrarr [10]*int
func f30(b bool) {
// two live temps during print(p):
// the copy of ptrarr and the internal iterator pointer.
if b {
for _, p := range ptrarr {
printintpointer(p) // ERROR "live at call to printintpointer: autotmp_[0-9]+ autotmp_[0-9]+$"
}
}
for _, p := range ptrarr {
printintpointer(p) // ERROR "live at call to printintpointer: autotmp_[0-9]+ autotmp_[0-9]+$"
}
for _, p := range ptrarr {
printintpointer(p) // ERROR "live at call to printintpointer: autotmp_[0-9]+ autotmp_[0-9]+$"
}
}
// conversion to interface should not leave temporary behind
func f31(b1, b2, b3 bool) {
if b1 {
g31("a") // ERROR "live at call to convT2E: autotmp_[0-9]+$" "live at call to g31: autotmp_[0-9]+$"
}
if b2 {
h31("b") // ERROR "live at call to newobject: autotmp_[0-9]+$" "live at call to convT2E: autotmp_[0-9]+ autotmp_[0-9]+$" "live at call to h31: autotmp_[0-9]+$"
}
if b3 {
panic("asdf") // ERROR "live at call to convT2E: autotmp_[0-9]+$" "live at call to gopanic: autotmp_[0-9]+$"
}
print(b3)
}
func g31(interface{})
func h31(...interface{})
// non-escaping partial functions passed to function call should die on return
type T32 int
func (t *T32) Inc() { // ERROR "live at entry"
*t++
}
var t32 T32
func f32(b bool) {
if b {
call32(t32.Inc) // ERROR "live at call to call32: autotmp_[0-9]+$"
}
call32(t32.Inc) // ERROR "live at call to call32: autotmp_[0-9]+$"
call32(t32.Inc) // ERROR "live at call to call32: autotmp_[0-9]+$"
}
//go:noescape
func call32(func())
// temporaries introduced during if conditions and && || expressions
// should die once the condition has been acted upon.
var m33 map[interface{}]int
func f33() {
if m33[nil] == 0 { // ERROR "live at call to mapaccess1: autotmp_[0-9]+$"
printnl()
return
} else {
printnl()
}
printnl()
}
func f34() {
if m33[nil] == 0 { // ERROR "live at call to mapaccess1: autotmp_[0-9]+$"
printnl()
return
}
printnl()
}
func f35() {
if m33[nil] == 0 && m33[nil] == 0 { // ERROR "live at call to mapaccess1: autotmp_[0-9]+$"
printnl()
return
}
printnl()
}
func f36() {
if m33[nil] == 0 || m33[nil] == 0 { // ERROR "live at call to mapaccess1: autotmp_[0-9]+$"
printnl()
return
}
printnl()
}
func f37() {
if (m33[nil] == 0 || m33[nil] == 0) && m33[nil] == 0 { // ERROR "live at call to mapaccess1: autotmp_[0-9]+$"
printnl()
return
}
printnl()
}
// select temps should disappear in the case bodies
var c38 chan string
func fc38() chan string
func fi38(int) *string
func fb38() *bool
func f38(b bool) {
// we don't care what temps are printed on the lines with output.
// we care that the println lines have no live variables
// and therefore no output.
if b {
select { // ERROR "live at call"
case <-fc38(): // ERROR "live at call"
printnl()
case fc38() <- *fi38(1): // ERROR "live at call"
printnl()
case *fi38(2) = <-fc38(): // ERROR "live at call"
printnl()
case *fi38(3), *fb38() = <-fc38(): // ERROR "live at call"
printnl()
}
printnl()
}
printnl()
}
// issue 8097: mishandling of x = x during return.
func f39() (x []int) {
x = []int{1}
printnl() // ERROR "live at call to printnl: x"
return x
}
func f39a() (x []int) {
x = []int{1}
printnl() // ERROR "live at call to printnl: x"
return
}
func f39b() (x [10]*int) {
x = [10]*int{}
x[0] = new(int) // ERROR "live at call to newobject: x"
printnl() // ERROR "live at call to printnl: x"
return x
}
func f39c() (x [10]*int) {
x = [10]*int{}
x[0] = new(int) // ERROR "live at call to newobject: x"
printnl() // ERROR "live at call to printnl: x"
return
}
// issue 8142: lost 'addrtaken' bit on inlined variables.
// no inlining in this test, so just checking that non-inlined works.
type T40 struct {
m map[int]int
}
func newT40() *T40 {
ret := T40{}
ret.m = make(map[int]int) // ERROR "live at call to makemap: &ret"
return &ret
}
func bad40() {
t := newT40()
_ = t
printnl()
}
func good40() {
ret := T40{}
ret.m = make(map[int]int) // ERROR "live at call to makemap: autotmp_.* ret"
t := &ret
printnl() // ERROR "live at call to printnl: autotmp_.* ret"
_ = t
}
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