Duff's device was disabled on darwin/arm64 because the darwin
linker couldn't handle a branch relocation with non-zero addend.
This is no longer the case now. The darwin linker can handle it
just fine. So enable it.
Fixes#54189.
Change-Id: Ida7ebafe6eb01db1af5bb8ae60a62491da5eabdf
Reviewed-on: https://go-review.googlesource.com/c/go/+/420894
Reviewed-by: Eric Fang <eric.fang@arm.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
When types2 type checks a method expression or method value that
selects a type parameter method, the Selection.Index is indexed based
on the method's index within the type parameter's constraint
interface.
However, with a fully-stenciled implementation, naively using the
index would result in picking a method from the corresponding type
argument's full method set, which could select a different method.
Unified IR currently avoids this because it selects methods based on
name, not index; but experimenting with index-based selection revealed
that there are no test cases that would have caught this failure case.
Change-Id: Idbc39e1ee741714203d4749e47f5bc015af25020
Reviewed-on: https://go-review.googlesource.com/c/go/+/421815
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Mark the assembly routines as not escaping their arguments.
Add a special case to NewInt that, when inlined, can do all
of its allocations (a big.Int and a [1]Word) on the stack.
Update #29951
Change-Id: I9bd38c262eb97df98c0ed9874da7daac381243ea
Reviewed-on: https://go-review.googlesource.com/c/go/+/411254
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>
We don't need a multiply when the element type is size 0 or 1.
The panic functions don't return, so we don't need any post-call
code (register restores, etc.).
Change-Id: I0dcea5df56d29d7be26554ddca966b3903c672e5
Reviewed-on: https://go-review.googlesource.com/c/go/+/419754
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Calling TypeOf to initialize variables forces any import of "reflect"
to link in the declared types of "reflect" even if they are unused.
TypeOf operates on Type and which will pull in
all transitive dependencies of Type, which includes Value as well.
Avoid this problem by declaring a rtypeOf function that
directly extracts the *rtype from an interface value
without going through Type as an intermediate type.
For a program that blank imports "reflect",
this reduces the binary size by ~34 KiB.
Updates #54097
Change-Id: I8dc7d8da8fedc48cc0dd842b69f510d17144827e
Reviewed-on: https://go-review.googlesource.com/c/go/+/419757
Run-TryBot: Joseph Tsai <joetsai@digital-static.net>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Base on gri@'s suggestion in CL 308971. "Rnd" is a bit random.
Change-Id: I4aad8b7992b31dfd26d20b3c332bc6e1e90f67db
Reviewed-on: https://go-review.googlesource.com/c/go/+/422036
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Than McIntosh <thanm@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
These are available since Go 1.7. The version used for bootstrap is Go
1.17 for Go 1.20.
For #44505
Change-Id: I497c9f617baefdeb273cd115b08b6e31bd10aad2
Reviewed-on: https://go-review.googlesource.com/c/go/+/421634
Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
There's no need for a and b to match types. The typechecker already
ensured that a and b are both slices with the same base type, or
a and b are (possibly named) []byte and string.
The optimization to treat append(b, make([], ...)) as a zeroing
slice extension doesn't fire when there's a OCONVNOP wrapping the make.
Fixes#53888
Change-Id: Ied871ed0bbb8e4a4b35d280c71acbab8103691bc
Reviewed-on: https://go-review.googlesource.com/c/go/+/418475
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Keith Randall <khr@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
Read the bitmaps one uintptr at a time instead of one byte at a time.
Performance so far:
Allocation heavy, no retention: ~30% faster in heapBitsSetType
Scan heavy, ~no allocation: ~even in scanobject
Change-Id: I40d492b50d7f89d1b4261c2de58f6d255fa5e93e
Reviewed-on: https://go-review.googlesource.com/c/go/+/407036
Reviewed-by: Keith Randall <khr@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Use just 1 bit per word to record the ptr/nonptr bitmap.
Use word-sized operations to manipulate the bitmap, so we can operate
on up to 64 ptr/nonptr bits at a time.
Use a separate bitmap, one bit per word of the ptr/nonptr bitmap,
to encode a no-more-pointers signal. Since we can check 64 ptr/nonptr
bits at once, knowing the exact last pointer location is not necessary.
This cleans up the bitmap implementation significantly, which will
hopefully make it faster. TODO: measure
As a followon CL, we should make the gcdata bitmap an array of
uintptr instead of an array of byte, so we can load 64 bits of it at once.
Similarly for the processing of gc programs.
Change-Id: I18151b1876d9543599800dec51e2a1b19df97d49
Reviewed-on: https://go-review.googlesource.com/c/go/+/407035
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Keith Randall <khr@google.com>
Since when any user errors about out-of-bounds constants should have
been already reported by types2.
Change-Id: I81b6bfec53201bbf546c48157fc8154cdb3c6e45
Reviewed-on: https://go-review.googlesource.com/c/go/+/421876
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
This reverts commit 964f0c7a30.
Reason: cause increasing timeout in crypto/tls tests on race builders.
Change-Id: Id16d4fcd19c2ca2e89ad4d0c9d55ef1105b19c76
Reviewed-on: https://go-review.googlesource.com/c/go/+/422035
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Use the newly added atomic.Pointer[T] type for atomically
loading and storing type *T pointers. This has the advantage of
avoiding runtime type assertions required by its predecessor,
atomic.Value.
To fix build failures uncovered by TryBots (caused by "panic:
unaligned 64-bit atomic operation"), also change conn.curState to
type atomic.Uint64 so that it is 64-bit aligned.
Change-Id: I6024d12cd581adfdccc01be7eb0faa7482036614
Reviewed-on: https://go-review.googlesource.com/c/go/+/420901
Reviewed-by: Damien Neil <dneil@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
OpenBSD 7.1 onwards expose the aarch64 ISAR0 and ISAR1 registers via sysctl:
$ sysctl machdep
machdep.compatible=apple,j274
machdep.id_aa64isar0=153421459058925856
machdep.id_aa64isar1=1172796674562
Implement CPU feature detection for openbsd/arm64 based on this information.
Fixes#31746
Change-Id: If8a9b2b8fc557e1aaefbcb52f4d1bd9efc43856d
Reviewed-on: https://go-review.googlesource.com/c/go/+/421875
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Joel Sing <joel@sing.id.au>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Implement proposal #45454, providing build tags based on the
sub-architecture information in the GO$GOARCH variable
(for example, GOARM for GOARCH=arm).
For example, when GOAMD64=v2, the additional build tags
amd64.v1 and amd64.v2 are defined to be true.
Fixes#45454.
Change-Id: I7be56060d47fc61843b97fd8a78498e8202c1ee7
Reviewed-on: https://go-review.googlesource.com/c/go/+/421434
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Auto-Submit: Russ Cox <rsc@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Assumingly this appears to have been a bug in c2go, as this appeared in
https://go.dev/cl/172260043.
Change-Id: I8477ec226ffb31268b9c479af13b0fcf401dbeec
Reviewed-on: https://go-review.googlesource.com/c/go/+/418276
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>
In gcController.startCycle we just compute the initial value in a
local variable before assigning to the atomic field to avoid noisy
churn.
For #53821.
Change-Id: Ibde0ac8fd49aa6bbee3bd02fe3ffb17429abd5a9
Reviewed-on: https://go-review.googlesource.com/c/go/+/417784
Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Austin Clements <austin@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Same as CL 417555, but for cmd/compile.
Fixes#54220
Change-Id: I4cc6deaf0a87c952f636888b4ab73f81a44bfebd
Reviewed-on: https://go-review.googlesource.com/c/go/+/420975
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Keith Randall <khr@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Atomic operations are used even during STW for consistency.
For #53821.
Change-Id: Ibe7afe5cf893b1288ce24fc96b7691b1f81754ff
Reviewed-on: https://go-review.googlesource.com/c/go/+/417775
Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Current init() implementation in `encoding/gob/decode.go` checks int/uint/uintptr bit size with reflection in runtime. We could replace it with values available on compile stage. This should reduce time and allocations on binary start.
Results from GODEBUG=inittrace=1:
before:
init encoding/gob @4.4 ms, 0.21 ms clock, 43496 bytes, 652 allocs
after:
init encoding/gob @4.4 ms, 0.15 ms clock, 41672 bytes, 643 allocs
Updates #54184
Change-Id: I46dda2682fb92519da199415e29401d61edce697
Reviewed-on: https://go-review.googlesource.com/c/go/+/420455
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Rob Pike <r@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
The RType field isn't needed when performing type assertions from
non-empty interface types, because we use the ITab field instead. But
the inline body exporter didn't know to expect this.
It's possible we could use a single bool to distinguish whether
we're serializing the RType or ITab field, but using two is simpler
and seems safer.
Fixes#54302.
Change-Id: I9ddac72784fb2241fee0a0dee30493d868a2c259
Reviewed-on: https://go-review.googlesource.com/c/go/+/421755
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Sometimes when implementing a Formatter it's helpful to use the fmt
package without invoking the formatter. This new function, FormatString,
makes that easier in some cases by recreating the original formatting
directive (such as "%3.2f") that caused Formatter.Format to be
called.
The original Formatter interface is probably not what we would
design today, but we're stuck with it. FormatString, although it
takes a State as an argument, compensates by making Formatter a
little more flexible.
The State does not include the verb so (unlike in the issue), we
must provide it explicitly in the call to FormatString. Doing it there
minimizes allocations by returning the complete format string.
Fixes#51668
Updates #51195
Change-Id: Ie31c8256515864b2f460df45fbd231286b8b7a28
Reviewed-on: https://go-review.googlesource.com/c/go/+/400875
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Russ Cox <rsc@golang.org>
CL 421334 updated most of golang.org/x dependencies at the start of
the Go 1.20 development cycle. This CL updates x/net and x/tools as
well, now that go.dev/issue/54259 is resolved.
For #36905.
Updates #54259.
Change-Id: Ie422b71cba060a4774076eebf3b499cda1150367
Reviewed-on: https://go-review.googlesource.com/c/go/+/421461
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Also don't run on all the other tiny slow boxes we have.
Should fix the remaining ppc64le broken builders.
For #44505 (or at least somehow provoked by it).
Change-Id: I72e8086cb641f3f7da3a872140a752bf328eec1f
Reviewed-on: https://go-review.googlesource.com/c/go/+/421438
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Nothing seems to break, not even the noopt builder.
For #51256 (the conversation there is headed toward additional changes).
Change-Id: Icb7ca451159a74f351c25d2cefb32c773b9bb017
Reviewed-on: https://go-review.googlesource.com/c/go/+/416859
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
It has been superceded by golang.org/x/build/cmd/genbootstrap.
Change-Id: Ifc00cd1de769bf807a0f6df643897c2f2339a073
Reviewed-on: https://go-review.googlesource.com/c/go/+/419116
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
The setting of the path for the dynamic loader when building for
linux/ppc64le ELF v2 was incorrectly set to the path for
PPC64 ELF v1. This has not caused issues in the common cases
because this string can be set based on the default GO_LDSO setting.
It does result in an incorrect value when cross compiling binaries
with -buildmode=pie.
Updates #53813
Change-Id: I84de1c97b42e0434760b76a57c5a05e055fbb730
Reviewed-on: https://go-review.googlesource.com/c/go/+/417614
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
For a type definition like `type I interface{ M() }`, the go/types API
traditionally sets `M`'s receiver parameter type to `I`, whereas
Unified IR was (intentionally) leaving it as `interface{ M() }`.
I still think `interface{ M() }` is the more consistent and
semantically correct type to use in this scenario, but I concede that
users want `I` instead, as evidenced by existing tooling and tests.
Updates #49906.
Change-Id: I74ba5e8b08e4e98ed9dc49f72b7834d5b552058b
Reviewed-on: https://go-review.googlesource.com/c/go/+/421355
Reviewed-by: David Chase <drchase@google.com>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Merge List:
+ 2022-08-04 85d87b9c75 all: update vendored golang.org/x dependencies for Go 1.20 development
+ 2022-08-04 fb1bfd4d37 all: remove pre-Go 1.17 workarounds
+ 2022-08-04 44ff9bff0c runtime: clean up panic and deadlock lock ranks
+ 2022-08-04 f42dc0de74 runtime: make the lock rank DAG make more sense
+ 2022-08-04 d29a0282e9 runtime: add mayAcquire annotation for finlock
+ 2022-08-04 c5be4ed7df runtime: add missing trace lock edges
+ 2022-08-04 2b8a9a484f runtime: generate the lock ranking from a DAG description
+ 2022-08-04 ddfd639408 runtime: delete unused lock ranks
+ 2022-08-04 426ea5702b internal/dag: add a Graph type and make node order deterministic
+ 2022-08-04 d37cc9a8cd go/build, internal/dag: lift DAG parser into an internal package
+ 2022-08-04 ab0a94c6d3 cmd/dist: require Go 1.17 for building Go
+ 2022-08-04 1e3c19f3fe runtime: support riscv64 SV57 mode
+ 2022-08-03 f28fa952b5 make.bat, make.rc: show bootstrap toolchain version
+ 2022-08-03 87384801dc cmd/asm: update package doc to describe "-p" option
+ 2022-08-03 c6a2dada0d net: disable TestIPv6WriteMsgUDPAddrPortTargetAddrIPVersion [sic] on DragonflyBSD
+ 2022-08-02 29b9a328d2 runtime: trivial replacements of g in remaining files
+ 2022-08-02 c647264619 runtime: trivial replacements of g in signal_unix.go
+ 2022-08-02 399f50c9d7 runtime: tricky replacements of g in traceback.go
+ 2022-08-02 4509e951ec runtime: tricky replacements of g in proc.go
+ 2022-08-02 4400238ec8 runtime: trivial replacements of _g_ in remaining files
+ 2022-08-02 5999a28de8 runtime: trivial replacements of _g_ in os files
+ 2022-08-02 0e18cf6d09 runtime: trivial replacements of _g_ in GC files
+ 2022-08-02 4358a53a97 runtime: trivial replacements of _g_ in proc.go
+ 2022-08-02 b486518964 runtime: tricky replacements of _g_ in os3_solaris.go
+ 2022-08-02 54a0ab3f7b runtime: tricky replacements of _g_ in os3_plan9.go
+ 2022-08-02 4240ff764b runtime: tricky replacements of _g_ in signal_windows.go
+ 2022-08-02 8666d89ca8 runtime: tricky replacements of _g_ in signal_unix.go
+ 2022-08-02 74cee276fe runtime: tricky replacements of _g_ in trace.go
+ 2022-08-02 222799fde6 runtime: tricky replacements of _g_ in mgc.go
+ 2022-08-02 e9d7f54a1a runtime: tricky replacements of _g_ in proc.go
+ 2022-08-02 5e8d261918 runtime: rename _p_ to pp
+ 2022-08-02 0ad2ec6596 runtime: clean up dopanic_m
+ 2022-08-02 7e952962df runtime: clean up canpanic
+ 2022-08-02 9dbc0f3556 runtime: fix outdated g.m comment in traceback.go
+ 2022-08-02 d723df76da internal/goversion: update Version to 1.20
+ 2022-08-02 1b7e71e8ae all: disable tests that fail on Alpine
+ 2022-08-01 f2a9f3e2e0 test: improve generic type assertion test
+ 2022-08-01 27038b70f8 cmd/compile: fix wrong dict pass condition for type assertions
+ 2022-08-01 e99f53fed9 doc: move Go 1.19 release notes to x/website
+ 2022-08-01 8b13a073a1 doc: mention removal of cmd/compile's -importmap and -installsuffix flags
+ 2022-08-01 e95fd4c238 doc/go1.19: fix typo: EM_LONGARCH -> EM_LOONGARCH
+ 2022-08-01 dee3efd9f8 doc/go1.19: fix a few links that were missing trailing slashes
+ 2022-07-30 f32519e5fb runtime: fix typos
+ 2022-07-29 9a2001a8cc cmd/dist: always pass -short=true with -quick
+ 2022-07-28 5c8ec89cb5 doc/go1.19: minor adjustments and links
+ 2022-07-28 417be37048 doc/go1.19: improve the loong64 release notes
+ 2022-07-28 027855e8d8 os/exec: add GODEBUG setting to opt out of ErrDot changes
Change-Id: Idc0fbe93978c0dff7600b90a2c3ecc067fd9f5f2
Go 1.20 development is just beginning. This is a time to update all
golang.org/x/... module versions that contribute packages to the std
and cmd modules in the standard library to latest master versions.
This CL holds back some of the available updates to the x/net module
due to go.dev/issue/54259. It'll be updated in a later separate pass.
x/tools is also held back a bit to avoid pulling in too new of x/net.
For #36905.
For #53812.
Updates #54259.
Change-Id: Iaefe6a343a02cc5ceb85c15125882d64dd372627
Reviewed-on: https://go-review.googlesource.com/c/go/+/421334
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
The Go bootstrap toolchain requirement is now Go 1.17.
We can finally delete all these pre-Go 1.17 workarounds.
For #44505.
Change-Id: I59d4dff1cde23da022892b5b6a116eb3dbad9ce4
Reviewed-on: https://go-review.googlesource.com/c/go/+/420903
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
