go/test/escape_calls.go

55 lines
1.4 KiB
Go
Raw Normal View History

cmd/internal/gc: improve flow of input params to output params This includes the following information in the per-function summary: outK = paramJ encoded in outK bits for paramJ outK = *paramJ encoded in outK bits for paramJ heap = paramJ EscHeap heap = *paramJ EscContentEscapes Note that (currently) if the address of a parameter is taken and returned, necessarily a heap allocation occurred to contain that reference, and the heap can never refer to stack, therefore the parameter and everything downstream from it escapes to the heap. The per-function summary information now has a tuneable number of bits (2 is probably noticeably better than 1, 3 is likely overkill, but it is now easy to check and the -m debugging output includes information that allows you to figure out if more would be better.) A new test was added to check pointer flow through struct-typed and *struct-typed parameters and returns; some of these are sensitive to the number of summary bits, and ought to yield better results with a more competent escape analysis algorithm. Another new test checks (some) correctness with array parameters, results, and operations. The old analysis inferred a piece of plan9 runtime was non-escaping by counteracting overconservative analysis with buggy analysis; with the bug fixed, the result was too conservative (and it's not easy to fix in this framework) so the source code was tweaked to get the desired result. A test was added against the discovered bug. The escape analysis was further improved splitting the "level" into 3 parts, one tracking the conventional "level" and the other two computing the highest-level-suffix-from-copy, which is used to generally model the cancelling effect of indirection applied to address-of. With the improved escape analysis enabled, it was necessary to modify one of the runtime tests because it now attempts to allocate too much on the (small, fixed-size) G0 (system) stack and this failed the test. Compiling src/std after touching src/runtime/*.go with -m logging turned on shows 420 fewer heap allocation sites (10538 vs 10968). Profiling allocations in src/html/template with for i in {1..5} ; do go tool 6g -memprofile=mastx.${i}.prof -memprofilerate=1 *.go; go tool pprof -alloc_objects -text mastx.${i}.prof ; done showed a 15% reduction in allocations performed by the compiler. Update #3753 Update #4720 Fixes #10466 Change-Id: I0fd97d5f5ac527b45f49e2218d158a6e89951432 Reviewed-on: https://go-review.googlesource.com/8202 Run-TryBot: David Chase <drchase@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Russ Cox <rsc@golang.org>
2015-03-26 20:36:15 +00:00
// errorcheck -0 -m -l
// Copyright 2015 The Go Authors. All rights reserved.
cmd/internal/gc: improve flow of input params to output params This includes the following information in the per-function summary: outK = paramJ encoded in outK bits for paramJ outK = *paramJ encoded in outK bits for paramJ heap = paramJ EscHeap heap = *paramJ EscContentEscapes Note that (currently) if the address of a parameter is taken and returned, necessarily a heap allocation occurred to contain that reference, and the heap can never refer to stack, therefore the parameter and everything downstream from it escapes to the heap. The per-function summary information now has a tuneable number of bits (2 is probably noticeably better than 1, 3 is likely overkill, but it is now easy to check and the -m debugging output includes information that allows you to figure out if more would be better.) A new test was added to check pointer flow through struct-typed and *struct-typed parameters and returns; some of these are sensitive to the number of summary bits, and ought to yield better results with a more competent escape analysis algorithm. Another new test checks (some) correctness with array parameters, results, and operations. The old analysis inferred a piece of plan9 runtime was non-escaping by counteracting overconservative analysis with buggy analysis; with the bug fixed, the result was too conservative (and it's not easy to fix in this framework) so the source code was tweaked to get the desired result. A test was added against the discovered bug. The escape analysis was further improved splitting the "level" into 3 parts, one tracking the conventional "level" and the other two computing the highest-level-suffix-from-copy, which is used to generally model the cancelling effect of indirection applied to address-of. With the improved escape analysis enabled, it was necessary to modify one of the runtime tests because it now attempts to allocate too much on the (small, fixed-size) G0 (system) stack and this failed the test. Compiling src/std after touching src/runtime/*.go with -m logging turned on shows 420 fewer heap allocation sites (10538 vs 10968). Profiling allocations in src/html/template with for i in {1..5} ; do go tool 6g -memprofile=mastx.${i}.prof -memprofilerate=1 *.go; go tool pprof -alloc_objects -text mastx.${i}.prof ; done showed a 15% reduction in allocations performed by the compiler. Update #3753 Update #4720 Fixes #10466 Change-Id: I0fd97d5f5ac527b45f49e2218d158a6e89951432 Reviewed-on: https://go-review.googlesource.com/8202 Run-TryBot: David Chase <drchase@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Russ Cox <rsc@golang.org>
2015-03-26 20:36:15 +00:00
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Test escape analysis for function parameters.
// In this test almost everything is BAD except the simplest cases
// where input directly flows to output.
package foo
func f(buf []byte) []byte { // ERROR "leaking param: buf to result ~r1 level=0$"
return buf
}
func g(*byte) string
func h(e int) {
var x [32]byte // ERROR "moved to heap: x$"
g(&f(x[:])[0]) // ERROR "&f\(x\[:\]\)\[0\] escapes to heap$" "x escapes to heap$"
}
type Node struct {
s string
left, right *Node
}
func walk(np **Node) int { // ERROR "leaking param content: np"
n := *np
w := len(n.s)
if n == nil {
return 0
}
wl := walk(&n.left) // ERROR "walk &n.left does not escape"
wr := walk(&n.right) // ERROR "walk &n.right does not escape"
if wl < wr {
n.left, n.right = n.right, n.left
wl, wr = wr, wl
}
*np = n
return w + wl + wr
}
// Test for bug where func var f used prototype's escape analysis results.
func prototype(xyz []string) {} // ERROR "prototype xyz does not escape"
func bar() {
var got [][]string
f := prototype
f = func(ss []string) { got = append(got, ss) } // ERROR "leaking param: ss" "func literal does not escape"
s := "string"
f([]string{s}) // ERROR "\[\]string literal escapes to heap"
}