mirror of
https://github.com/golang/go
synced 2024-11-05 16:46:10 -07:00
7fbb1b36c3
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>
45 lines
1.0 KiB
Go
45 lines
1.0 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 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
|
|
}
|