mirror of
https://github.com/golang/go
synced 2024-11-20 03:24:41 -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>
68 lines
1.2 KiB
Go
68 lines
1.2 KiB
Go
// Copyright 2009 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.
|
|
|
|
package runtime
|
|
|
|
import "unsafe"
|
|
|
|
//go:nosplit
|
|
func findnull(s *byte) int {
|
|
if s == nil {
|
|
return 0
|
|
}
|
|
p := (*[_MaxMem/2 - 1]byte)(unsafe.Pointer(s))
|
|
l := 0
|
|
for p[l] != 0 {
|
|
l++
|
|
}
|
|
return l
|
|
}
|
|
|
|
func findnullw(s *uint16) int {
|
|
if s == nil {
|
|
return 0
|
|
}
|
|
p := (*[_MaxMem/2/2 - 1]uint16)(unsafe.Pointer(s))
|
|
l := 0
|
|
for p[l] != 0 {
|
|
l++
|
|
}
|
|
return l
|
|
}
|
|
|
|
var maxstring uintptr = 256 // a hint for print
|
|
|
|
//go:nosplit
|
|
func gostringnocopy(str *byte) string {
|
|
ss := stringStruct{str: unsafe.Pointer(str), len: findnull(str)}
|
|
s := *(*string)(unsafe.Pointer(&ss))
|
|
for {
|
|
ms := maxstring
|
|
if uintptr(len(s)) <= ms || casuintptr(&maxstring, ms, uintptr(len(s))) {
|
|
break
|
|
}
|
|
}
|
|
return s
|
|
}
|
|
|
|
func gostringw(strw *uint16) string {
|
|
var buf [8]byte
|
|
str := (*[_MaxMem/2/2 - 1]uint16)(unsafe.Pointer(strw))
|
|
n1 := 0
|
|
for i := 0; str[i] != 0; i++ {
|
|
n1 += runetochar(buf[:], rune(str[i]))
|
|
}
|
|
s, b := rawstring(n1 + 4)
|
|
n2 := 0
|
|
for i := 0; str[i] != 0; i++ {
|
|
// check for race
|
|
if n2 >= n1 {
|
|
break
|
|
}
|
|
n2 += runetochar(b[n2:], rune(str[i]))
|
|
}
|
|
b[n2] = 0 // for luck
|
|
return s[:n2]
|
|
}
|