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go/test/escape_closure.go
Matthew Dempsky ff47dd1d66 cmd/compile/internal/escape: optimize indirect closure calls
This CL extends escape analysis in two ways.

First, we already optimize directly called closures. For example,
given:

	var x int  // already stack allocated today
	p := func() *int { return &x }()

we don't need to move x to the heap, because we can statically track
where &x flows. This CL extends the same idea to work for indirectly
called closures too, as long as we know everywhere that they're
called. For example:

	var x int  // stack allocated after this CL
	f := func() *int { return &x }
	p := f()

This will allow a subsequent CL to move the generation of go/defer
wrappers earlier.

Second, this CL adds tracking to detect when pointer values flow to
the pointee operand of an indirect assignment statement (i.e., flows
to p in "*p = x") or to builtins that modify memory (append, copy,
clear). This isn't utilized in the current CL, but a subsequent CL
will make use of it to better optimize string->[]byte conversions.

Updates #2205.

Change-Id: I610f9c531e135129c947684833e288ce64406f35
Reviewed-on: https://go-review.googlesource.com/c/go/+/520259
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
2023-08-17 16:36:09 +00:00

194 lines
4.6 KiB
Go

// errorcheck -0 -m -l
// Copyright 2015 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.
// Test escape analysis for closure arguments.
package escape
var sink interface{}
func ClosureCallArgs0() {
x := 0
func(p *int) { // ERROR "p does not escape" "func literal does not escape"
*p = 1
}(&x)
}
func ClosureCallArgs1() {
x := 0
for {
func(p *int) { // ERROR "p does not escape" "func literal does not escape"
*p = 1
}(&x)
}
}
func ClosureCallArgs2() {
for {
x := 0
func(p *int) { // ERROR "p does not escape" "func literal does not escape"
*p = 1
}(&x)
}
}
func ClosureCallArgs3() {
x := 0 // ERROR "moved to heap: x"
func(p *int) { // ERROR "leaking param: p" "func literal does not escape"
sink = p
}(&x)
}
func ClosureCallArgs4() {
x := 0
_ = func(p *int) *int { // ERROR "leaking param: p to result ~r0" "func literal does not escape"
return p
}(&x)
}
func ClosureCallArgs5() {
x := 0 // ERROR "moved to heap: x"
// TODO(mdempsky): We get "leaking param: p" here because the new escape analysis pass
// can tell that p flows directly to sink, but it's a little weird. Re-evaluate.
sink = func(p *int) *int { // ERROR "leaking param: p" "func literal does not escape"
return p
}(&x)
}
func ClosureCallArgs6() {
x := 0 // ERROR "moved to heap: x"
func(p *int) { // ERROR "moved to heap: p" "func literal does not escape"
sink = &p
}(&x)
}
func ClosureCallArgs7() {
var pp *int
for {
x := 0 // ERROR "moved to heap: x"
func(p *int) { // ERROR "leaking param: p" "func literal does not escape"
pp = p
}(&x)
}
_ = pp
}
func ClosureCallArgs8() {
x := 0
defer func(p *int) { // ERROR "p does not escape" "func literal does not escape"
*p = 1
}(&x)
}
func ClosureCallArgs9() {
// BAD: x should not leak
x := 0 // ERROR "moved to heap: x"
for {
defer func(p *int) { // ERROR "func literal escapes to heap" "p does not escape"
*p = 1
}(&x)
}
}
func ClosureCallArgs10() {
for {
x := 0 // ERROR "moved to heap: x"
defer func(p *int) { // ERROR "func literal escapes to heap" "p does not escape"
*p = 1
}(&x)
}
}
func ClosureCallArgs11() {
x := 0 // ERROR "moved to heap: x"
defer func(p *int) { // ERROR "leaking param: p" "func literal does not escape"
sink = p
}(&x)
}
func ClosureCallArgs12() {
x := 0
defer func(p *int) *int { // ERROR "leaking param: p to result ~r0" "func literal does not escape"
return p
}(&x)
}
func ClosureCallArgs13() {
x := 0 // ERROR "moved to heap: x"
defer func(p *int) { // ERROR "moved to heap: p" "func literal does not escape"
sink = &p
}(&x)
}
func ClosureCallArgs14() {
x := 0
p := &x
_ = func(p **int) *int { // ERROR "leaking param: p to result ~r0 level=1" "func literal does not escape"
return *p
}(&p)
}
func ClosureCallArgs15() {
x := 0 // ERROR "moved to heap: x"
p := &x
sink = func(p **int) *int { // ERROR "leaking param content: p" "func literal does not escape"
return *p
}(&p)
}
func ClosureLeak1(s string) string { // ERROR "s does not escape"
t := s + "YYYY" // ERROR "escapes to heap"
return ClosureLeak1a(t) // ERROR "... argument does not escape"
}
// See #14409 -- returning part of captured var leaks it.
func ClosureLeak1a(a ...string) string { // ERROR "leaking param: a to result ~r0 level=1$"
return func() string { // ERROR "func literal does not escape"
return a[0]
}()
}
func ClosureLeak2(s string) string { // ERROR "s does not escape"
t := s + "YYYY" // ERROR "escapes to heap"
c := ClosureLeak2a(t) // ERROR "... argument does not escape"
return c
}
func ClosureLeak2a(a ...string) string { // ERROR "leaking param content: a"
return ClosureLeak2b(func() string { // ERROR "func literal does not escape"
return a[0]
})
}
func ClosureLeak2b(f func() string) string { // ERROR "f does not escape"
return f()
}
func ClosureIndirect() {
f := func(p *int) {} // ERROR "p does not escape" "func literal does not escape"
f(new(int)) // ERROR "new\(int\) does not escape"
g := f
g(new(int)) // ERROR "new\(int\) does not escape"
h := nopFunc
h(new(int)) // ERROR "new\(int\) does not escape"
}
func nopFunc(p *int) {} // ERROR "p does not escape"
func ClosureIndirect2() {
f := func(p *int) *int { return p } // ERROR "leaking param: p to result ~r0 level=0" "func literal does not escape"
f(new(int)) // ERROR "new\(int\) does not escape"
g := f
g(new(int)) // ERROR "new\(int\) does not escape"
h := nopFunc2
h(new(int)) // ERROR "new\(int\) does not escape"
}
func nopFunc2(p *int) *int { return p } // ERROR "leaking param: p to result ~r0 level=0"