Even very large Types are not very big.
The haspointer cache looks like premature optimization.
Removing them has no detectable compiler performance impact,
and it removes mutable shared state used by the backend.
Updates #15756
Change-Id: I2d2cf03f470f5eef5bcd50ff693ef6a01d481700
Reviewed-on: https://go-review.googlesource.com/38912
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Flush file content to disk before diffing files,
may cause unpredictable results on Windows.
Convert from \r\n to \n when comparing diff result.
Change-Id: Ibcd6154a2382dba1338ee5674333611aea16bb65
Reviewed-on: https://go-review.googlesource.com/36750
Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
REV/REV16/REVSH were introduced in ARMv6, they offered more efficient
byte reverse operatons.
MMUL/MMULA/MMULS were introduced in ARMv6, they simplified
a serial of mul->shift->add/sub operations into a single instruction.
RBIT was introduced in ARMv7, it inversed a 32-bit word's bit order.
MULS was introduced in ARMv7, it corresponded to MULA.
MULBB/MULABB were introduced in ARMv5TE, they performed 16-bit
multiplication (and accumulation).
Change-Id: I6365b17b3c4eaf382a657c210bb0094b423b11b8
Reviewed-on: https://go-review.googlesource.com/35565
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
CL 38147 eliminated package gc globals in formatting routines.
However, tconv still used the Type field Trecur
to avoid infinite recursion when formatting recursive
interfaces types such as (test/fixedbugs398.go):
type i1 interface {
F() interface {
i1
}
}
type i2 interface {
F() interface {
i2
}
}
This CL changes the recursion prevention to use a parameter,
and threads it through the formatting routines.
Because this fundamentally limits the embedding depth
of all types, it sets the depth limit to be much higher.
In practice, it is unlikely to impact any code at all,
one way or the other.
The remaining uses of Type.Trecur are boolean in nature.
A future CL will change Type.Trecur to be a boolean flag.
The removal of a couple of mode.Sprintf calls
makes this a very minor net performance improvement:
name old alloc/op new alloc/op delta
Template 40.0MB ± 0% 40.0MB ± 0% -0.13% (p=0.032 n=5+5)
Unicode 30.0MB ± 0% 29.9MB ± 0% ~ (p=0.310 n=5+5)
GoTypes 114MB ± 0% 113MB ± 0% -0.25% (p=0.008 n=5+5)
SSA 856MB ± 0% 855MB ± 0% -0.04% (p=0.008 n=5+5)
Flate 25.5MB ± 0% 25.4MB ± 0% -0.27% (p=0.008 n=5+5)
GoParser 31.9MB ± 0% 31.9MB ± 0% ~ (p=0.222 n=5+5)
Reflect 79.0MB ± 0% 78.6MB ± 0% -0.45% (p=0.008 n=5+5)
Tar 26.8MB ± 0% 26.7MB ± 0% -0.25% (p=0.032 n=5+5)
XML 42.4MB ± 0% 42.4MB ± 0% ~ (p=0.151 n=5+5)
name old allocs/op new allocs/op delta
Template 395k ± 0% 391k ± 0% -1.00% (p=0.008 n=5+5)
Unicode 321k ± 1% 319k ± 0% -0.56% (p=0.008 n=5+5)
GoTypes 1.16M ± 0% 1.14M ± 0% -1.61% (p=0.008 n=5+5)
SSA 7.63M ± 0% 7.60M ± 0% -0.30% (p=0.008 n=5+5)
Flate 239k ± 0% 234k ± 0% -1.94% (p=0.008 n=5+5)
GoParser 320k ± 0% 317k ± 1% -0.86% (p=0.008 n=5+5)
Reflect 1.00M ± 0% 0.98M ± 0% -2.17% (p=0.016 n=4+5)
Tar 255k ± 1% 251k ± 0% -1.35% (p=0.008 n=5+5)
XML 398k ± 0% 395k ± 0% -0.89% (p=0.008 n=5+5)
Updates #15756
Change-Id: Id23e647d347aa841f9a69d51f7d2d7d27b259239
Reviewed-on: https://go-review.googlesource.com/38797
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Right now, at least with Xcode 8.3, we invoke dsymutil and dutifully
copy what it produces back into the binary, but it has actually dropped
all the DWARF information that we wanted, because it didn't like
the look of go.o.
Make it like the look of go.o.
DWARF is tested in other ways, but typically indirectly and not for cgo programs.
Add a direct test, and one that exercises cgo.
This detects missing dwarf information in cgo-using binaries on macOS,
at least with Xcode 8.3, and possibly earlier versions as well.
Fixes#19772.
Change-Id: I0082e52c0bc8fc4e289770ec3dc02f39fd61e743
Reviewed-on: https://go-review.googlesource.com/38855
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Now that we no longer generate dead code,
it is possible to follow block predecessors
into infinite loops with no variable definitions,
causing an infinite loop during phi insertion.
To fix that, check explicitly whether the predecessor
is dead in lookupVarOutgoing, and if so, bail.
The loop in lookupVarOutgoing is very hot code,
so I am wary of adding anything to it.
However, a long, CPU-only benchmarking run shows no
performance impact at all.
Fixes#19783
Change-Id: I8ef8d267e0b20a29b5cb0fecd7084f76c6f98e47
Reviewed-on: https://go-review.googlesource.com/38913
Reviewed-by: David Chase <drchase@google.com>
We use an "autogenerated" position in several places.
Rather than recreate it each time, make one early on and reuse it.
This removes the creation of new positions during the backend,
which was not concurrency-safe.
Updates #15756
Change-Id: Ic116b2e60f0e99de1a2ea87fe763831b50b645f8
Reviewed-on: https://go-review.googlesource.com/38915
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Without this, the load fails during kernel exec, which results in the
mysterious and completely uninformative "Killed: 9" error.
It appears that the stars (or at least the inputs) were properly aligned
with earlier versions of Xcode so that this happened accidentally.
Make it happen on purpose.
Gregory Man bisected the breakage to this change in LLVM,
which fits the theory nicely:
https://github.com/llvm-mirror/llvm/commit/9a41e59cFixes#19734.
Change-Id: Ice67a09af2de29d3c0d5e3fcde6a769580897c95
Reviewed-on: https://go-review.googlesource.com/38854
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Might as well provide a way around the mach-o munging
that doesn't require stripping all symbols.
After all, -w does mean no DWARF.
For #11887, #19734, and anyone else that needs to disable
this code path without losing the symbol table.
Change-Id: I254b7539f97fb9211fa90f446264b383e7f3980f
Reviewed-on: https://go-review.googlesource.com/38853
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This keeps the host linker from printing
ld: warning: option -s is obsolete and being ignored
Fixes#19775.
Change-Id: I18dd4e4b3f59cbf35dad770fd65e6baea5a7347f
Reviewed-on: https://go-review.googlesource.com/38851
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
The gold linker is used by default in the Android NDK, except on
arm64:
https://github.com/android-ndk/ndk/issues/148
The Go linker already forces the use of the gold linker on arm and
arm64 (CL 22141) for other reasons. However, the test.bash script in
testcshared doesn't, resulting in linker errors on android/arm64:
warning: liblog.so, needed by ./libgo.so, not found (try using -rpath or
-rpath-link)
Add -fuse-ld=gold when running testcshared on Android. Fixes the
android/arm64 builder.
Change-Id: I35ca96f01f136bae72bec56d71b7ca3f344df1ed
Reviewed-on: https://go-review.googlesource.com/38832
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
After https://golang.org/cl/31490 we break false
output dependency for CVTS.. in compiler generated code.
I've looked through asm code, which uses CVTS..
and added XOR to the only case where it affected performance.
Log-6 21.6ns ± 0% 19.9ns ± 0% -7.87% (p=0.000 n=10+10)
Change-Id: I25d9b405e3041a3839b40f9f9a52e708034bb347
Reviewed-on: https://go-review.googlesource.com/38771
Run-TryBot: Ilya Tocar <ilya.tocar@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
There is always 128 bytes available below the stackguard. Allow functions
with medium-sized stack frames to use this, potentially allowing them to
avoid growing the stack.
This change makes all architectures use the same calculation as x86.
Change-Id: I2afb1a7c686ae5a933e50903b31ea4106e4cd0a0
Reviewed-on: https://go-review.googlesource.com/38734
Reviewed-by: Cherry Zhang <cherryyz@google.com>
By overwhelming popular demand, exclude vendored packages from ... matches,
by making ... never match the "vendor" element above a vendored package.
go help packages now reads:
An import path is a pattern if it includes one or more "..." wildcards,
each of which can match any string, including the empty string and
strings containing slashes. Such a pattern expands to all package
directories found in the GOPATH trees with names matching the
patterns.
To make common patterns more convenient, there are two special cases.
First, /... at the end of the pattern can match an empty string,
so that net/... matches both net and packages in its subdirectories, like net/http.
Second, any slash-separted pattern element containing a wildcard never
participates in a match of the "vendor" element in the path of a vendored
package, so that ./... does not match packages in subdirectories of
./vendor or ./mycode/vendor, but ./vendor/... and ./mycode/vendor/... do.
Note, however, that a directory named vendor that itself contains code
is not a vendored package: cmd/vendor would be a command named vendor,
and the pattern cmd/... matches it.
Fixes#19090.
Change-Id: I985bf9571100da316c19fbfd19bb1e534a3c9e5f
Reviewed-on: https://go-review.googlesource.com/38745
Reviewed-by: Alan Donovan <adonovan@google.com>
This reverts commit 041ecb697f.
Reason for revert: Not working on S390x and some 386 archs.
I have a guess why the S390x is failing. No clue on the 386 yet.
Revert until I can figure it out.
Change-Id: I64f1ce78fa6d1037ebe7ee2a8a8107cb4c1db70c
Reviewed-on: https://go-review.googlesource.com/38790
Reviewed-by: Keith Randall <khr@golang.org>
rsc.io/toolstash is gone; use rsc.io/pprof_mac_fix.
This fixes a bug in the test. It turns out the code being tested here
is also broken, so the test still doesn't pass after this CL (filed #19769).
Change-Id: Ieb725c321d7fab600708e133ae28f531e55521ad
Reviewed-on: https://go-review.googlesource.com/38743
Reviewed-by: Alan Donovan <adonovan@google.com>
The uintptr-typed Data field in reflect.SliceHeader and
reflect.StringHeader needs special treatment because it is
really a pointer. Add the special treatment in walk for
bug #19168 to escape analysis.
Includes extra debugging that was helpful.
Fixes#19743.
Change-Id: I6dab5002f0d436c3b2a7cdc0156e4fc48a43d6fe
Reviewed-on: https://go-review.googlesource.com/38738
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Previously, an inlined call to wg.Done() in package main would have the
following incorrect symbol name:
main.(*sync.WaitGroup).Done
This change modifies methodname to return the correct symbol name:
sync.(*WaitGroup).Done
This fix was suggested by @mdempsky.
Fixes#19467.
Change-Id: I0117838679ac5353789299c618ff8c326712d94d
Reviewed-on: https://go-review.googlesource.com/37866
Reviewed-by: Austin Clements <austin@google.com>
The `skip` argument passed to runtime.Caller and runtime.Callers should
be interpreted as the number of logical calls to skip (rather than the
number of physical stack frames to skip). This changes runtime.Callers
to skip inlined calls in addition to physical stack frames.
The result value of runtime.Callers is a slice of program counters
([]uintptr) representing physical stack frames. If the `skip` parameter
to runtime.Callers skips part-way into a physical frame, there is no
convenient way to encode that in the resulting slice. To avoid changing
the API in an incompatible way, our solution is to store the number of
skipped logical calls of the first frame in the _second_ uintptr
returned by runtime.Callers. Since this number is a small integer, we
encode it as a valid PC value into a small symbol called:
runtime.skipPleaseUseCallersFrames
For example, if f() calls g(), g() calls `runtime.Callers(2, pcs)`, and
g() is inlined into f, then the frame for f will be partially skipped,
resulting in the following slice:
pcs = []uintptr{pc_in_f, runtime.skipPleaseUseCallersFrames+1, ...}
We store the skip PC in pcs[1] instead of pcs[0] so that `pcs[i:]` will
truncate the captured stack trace rather than grow it for all i.
Updates #19348.
Change-Id: I1c56f89ac48c29e6f52a5d085567c6d77d499cf1
Reviewed-on: https://go-review.googlesource.com/37854
Run-TryBot: David Lazar <lazard@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Previously, we could not run tests with -l=4 on NaCl since the buildrun
action is not supported on NaCl. This lets us run tests with build flags
on NaCl.
Change-Id: I103370c7b823b4ff46f47df97e802da0dc2bc7c3
Reviewed-on: https://go-review.googlesource.com/38170
Run-TryBot: David Lazar <lazard@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
The aLongTimeAgo time value in net and net/http is used to cancel
in-flight read and writes. It was set to time.Unix(233431200, 0)
which seemed like far enough in the past.
But Raspberry Pis, lacking a real time clock, had to spoil the fun and
boot in 1970 at the Unix epoch time, breaking assumptions in net and
net/http.
So change aLongTimeAgo to time.Unix(1, 0), which seems like the
earliest safe value. I don't trust subsecond values on all operating
systems, and I don't trust the Unix zero time. The Raspberry Pis do
advance their clock at least. And the reported problem was that Hijack
on a ResponseWriter hung forever, waiting for the connection read
operation to finish. So now, even if kernel + userspace boots in under
a second (unlikely), the Hijack will just have to wait for up to a
second.
Fixes#19747
Change-Id: Id59430de2e7b5b5117d4903a788863e9d344e53a
Reviewed-on: https://go-review.googlesource.com/38785
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
We have lots of rewrite rules that vary only in the fact that
we have 2 versions for the 2 different orderings of various
commuting ops. For example:
(ADDL x (MOVLconst [c])) -> (ADDLconst [c] x)
(ADDL (MOVLconst [c]) x) -> (ADDLconst [c] x)
It can get unwieldly quickly, especially when there is more than
one commuting op in a rule.
Our existing "fix" for this problem is to have rules that
canonicalize the operations first. For example:
(Eq64 x (Const64 <t> [c])) && x.Op != OpConst64 -> (Eq64 (Const64 <t> [c]) x)
Subsequent rules can then assume if there is a constant arg to Eq64,
it will be the first one. This fix kinda works, but it is fragile and
only works when we remember to include the required extra rules.
The fundamental problem is that the rule matcher doesn't
know anything about commuting ops. This CL fixes that fact.
We already have information about which ops commute. (The register
allocator takes advantage of commutivity.) The rule generator now
automatically generates multiple rules for a single source rule when
there are commutative ops in the rule. We can now drop all of our
almost-duplicate source-level rules and the canonicalization rules.
I have some CLs in progress that will be a lot less verbose when
the rule generator handles commutivity for me.
I had to reorganize the load-combining rules a bit. The 8-way OR rules
generated 128 different reorderings, which was causing the generator
to put too much code in the rewrite*.go files (the big ones were going
from 25K lines to 132K lines). Instead I reorganized the rules to
combine pairs of loads at a time. The generated rule files are now
actually a bit (5%) smaller.
[Note to reviewers: check these carefully. Most of the other rule
changes are trivial.]
Make.bash times are ~unchanged.
Compiler benchmarks are not observably different. Probably because
we don't spend much compiler time in rule matching anyway.
I've also done a pass over all of our ops adding commutative markings
for ops which hadn't had them previously.
Fixes#18292
Change-Id: I999b1307272e91965b66754576019dedcbe7527a
Reviewed-on: https://go-review.googlesource.com/38666
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
reflect.callReflect heap-allocates a stack frame and then constructs
pointers to the arguments and result areas of that frame. However, if
there are no results, the results pointer will point past the end of
the frame allocation. If there are also no arguments, the arguments
pointer will also point past the end of the frame allocation. If the
GC observes either these pointers, it may panic.
Fix this by not constructing these pointers if these areas of the
frame are empty.
This adds a test of calling no-argument/no-result methods via reflect,
since nothing in std did this before. However, it's quite difficult to
demonstrate the actual failure because it depends on both exact
allocation patterns and on GC scanning the goroutine's stack while
inside one of the typedmemmovepartial calls.
I also audited other uses of typedmemmovepartial and
memclrNoHeapPointers in reflect, since these are the most susceptible
to this. These appear to be the only two cases that can construct
out-of-bounds arguments to these functions.
Fixes#19724.
Change-Id: I4b83c596b5625dc4ad0567b1e281bad4faef972b
Reviewed-on: https://go-review.googlesource.com/38736
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
"go env" prints Go environment information as a shell script format by
default but it's difficult for some tools (e.g. editor packages) to
interpret it.
The -json flag prints the environment in JSON format which
can be easily interpreted by a lot of tools.
$ go env -json
{
"CC": "gcc",
"CGO_CFLAGS": "-g -O2",
"CGO_CPPFLAGS": "",
"CGO_CXXFLAGS": "-g -O2",
"CGO_ENABLED": "1",
"CGO_FFLAGS": "-g -O2",
"CGO_LDFLAGS": "-g -O2",
"CXX": "g++",
"GCCGO": "gccgo",
"GOARCH": "amd64",
"GOBIN": "/home/haya14busa/go/bin",
"GOEXE": "",
"GOGCCFLAGS": "-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build498013955=/tmp/go-build -gno-record-gcc-switches",
"GOHOSTARCH": "amd64",
"GOHOSTOS": "linux",
"GOOS": "linux",
"GOPATH": "/home/haya14busa",
"GORACE": "",
"GOROOT": "/home/haya14busa/src/go.googlesource.com/go",
"GOTOOLDIR": "/home/haya14busa/src/go.googlesource.com/go/pkg/tool/linux_amd64",
"PKG_CONFIG": "pkg-config"
}
Also, it supports arguments with -json flag.
$ go env -json GOROOT GOPATH GOBIN
{
"GOBIN": "/home/haya14busa/go/bin",
"GOPATH": "/home/haya14busa",
"GOROOT": "/home/haya14busa/src/go.googlesource.com/go"
}
Fixes#12567
Change-Id: I75db3780f14a8ab8c7fa58cc3c9cc488ef7b66a1
Reviewed-on: https://go-review.googlesource.com/38757
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Gccgo crashed compiling a function that returned multiple zero-sized values.
Change-Id: I499112cc310e4a4f649962f4d2bc9fee95dee1b6
Reviewed-on: https://go-review.googlesource.com/38772
Reviewed-by: Than McIntosh <thanm@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This was cherry-picked to 1.8 as CL 38587, but on master issue was fixed
by CL 37661. Add still relevant part (test) and close issue, since test passes.
Fixes#19201
Change-Id: I6415792e2c465dc6d9bd6583ba1e54b107bcf5cc
Reviewed-on: https://go-review.googlesource.com/37376
Run-TryBot: Ilya Tocar <ilya.tocar@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
It is currently possible in the compiler to create a struct type,
calculate the widths of types that depend on it,
and then alter the struct type.
transformclosure has local protection against this.
Protect against it at a deeper level.
This is preparation to call dowidth automatically,
rather than explicitly.
This is a re-roll of CL 38469.
Change-Id: Ic5b4baa250618504611fc57cbf51ab01d1eddf80
Reviewed-on: https://go-review.googlesource.com/38534
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Prior to this CL, Type.Width != 0 was the mark
of a Type whose Width had been calculated.
As a result, dowidth always recalculated
the width of struct{}.
This, combined with the prohibition on calculating
the width of a FuncArgsStruct and the use of
struct{} as a function argument,
meant that there were circumstances in which
it was forbidden to call dowidth on a type.
This inhibits refactoring to call dowidth automatically,
rather than explicitly.
Instead add a helper method, Type.WidthCalculated,
and implement as Type.Align > 0.
Type.Width is not a good candidate for tracking
whether the width has been calculated;
0 is a value type width, and Width is subject to
too much magic value game-playing.
For good measure, add a test for #11354.
Change-Id: Ie9a9fb5d924e7a2010c1904ae5e38ed4a38eaeb2
Reviewed-on: https://go-review.googlesource.com/38468
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
It is explicitly assigned in each of the
assemblers as needed.
I plan to remove Cursym entirely eventually,
but this is a helpful intermediate step.
Passes toolstash-check -all.
Updates #15756
Change-Id: Id7ddefae2def439af44d03053886ca8cc935731f
Reviewed-on: https://go-review.googlesource.com/38727
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
It is insufficiently canonical;
see the discussion at issue 19719.
Fixes#19719
Change-Id: I0559ff3b1b39d7bc4b446d104f36fdf8ce3da50e
Reviewed-on: https://go-review.googlesource.com/38722
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
