Note that this is a redo of an undo of the original buggy CL 38666.
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.
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: Ic1c0e43fbf579539f459971625f69690c9ab8805
Reviewed-on: https://go-review.googlesource.com/38801
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Instead of walking the list of nodes twice,
once to find static entries to add to an array
and once to find dynamic entries to generate code for,
do the split once up front, into two slices.
Then process each slice individually.
This makes the code easier to read
and more importantly, easier to modify.
While we're here, add a TODO to avoid
using temporaries for mapassign_fast calls.
It's not an important TODO;
the generated code would be basically identical.
It would just avoid a minor amount of
pointless SSA optimization work.
Passes toolstash-check.
No measureable compiler performance impact.
Updates #19751
Change-Id: I84a8f2c22f9025c718ef34639059d7bd02a3c406
Reviewed-on: https://go-review.googlesource.com/39351
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This triggers 119 times during make.bash.
This CL reduces the time it takes for the
compiler to panic while compiling the code in #19751
from 22 minutes to 15 minutes. Yay, I guess.
Updates #19751
Change-Id: I8ca7f1ae75f89d1eb2a361d67b3055a975221734
Reviewed-on: https://go-review.googlesource.com/39294
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Old buggy hardware incorrectly executes the shift-left-K
then shift-right-K idiom for clearing K leftmost bits.
Use a right rotate instead of shift to avoid triggering the
bug.
Fixes#19809.
Change-Id: I6dc646b183c29e9d01aef944729f34388dcc687d
Reviewed-on: https://go-review.googlesource.com/39310
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
The example shouldn't rely on the existance of example_test.go. That
breaks in the playground, which is what the "run" button in
https://golang.org/pkg/go/parser/#example_ParseFile does.
Make the example self-sufficient by using a small piece of source via a
string literal instead.
Fixes#19823.
Change-Id: Ie8a3c6c5d00724e38ff727862b62e6a3621adc88
Reviewed-on: https://go-review.googlesource.com/39236
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Robert Griesemer <gri@golang.org>
In a concurrent backend, Ctxt.Lookup will need some
form of concurrency protection, which will make it
more expensive.
This CL changes the pcln table builder to track
filenames as strings rather than LSyms.
Those strings are then converted into LSyms
at the last moment, for writing the object file.
This CL removes over 85% of the calls to Ctxt.Lookup
in a run of make.bash.
Passes toolstash-check.
Updates #15756
Change-Id: I3c53deff6f16f2643169f3bdfcc7aca2ca58b0a4
Reviewed-on: https://go-review.googlesource.com/39291
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
When generating a random int8, uint8, int16, uint16, int32, uint32,
quick.Value chooses among all possible values.
But when generating a random int64 or uint64, it only chooses
values in the range [-2⁶², 2⁶²) (even for uint64).
It should, like for all the other integers, use the full range.
If it had, this would have caught #19807 earlier.
Instead it let us discover the presence of #19809.
While we are here, also make the default source of
randomness not completely deterministic.
Fixes#19808.
Change-Id: I070f852531c92b3670bd76523326c9132bfc9416
Reviewed-on: https://go-review.googlesource.com/39152
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
The header is literally
Key: Value
If the value or the key has leading or trailing spaces, those will
be lost by the round trip.
Found because testing/quick returns different values now.
Change-Id: I0f574bdbb5990689509c24309854d8f814b5efa0
Reviewed-on: https://go-review.googlesource.com/39211
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Minor cleanup.
This is the only such instance in the compiler.
Change-Id: I4e8ecde57d71867c7e1ac4d17e2154a91dd262b0
Reviewed-on: https://go-review.googlesource.com/39209
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Dave Cheney <dave@cheney.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>
No particular need for this,
but it's nice to enforce invariants
when they are available.
Change-Id: Ia6fa88dc4116f65dac2879509746e123e2c1862a
Reviewed-on: https://go-review.googlesource.com/39201
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
nodfp is a global, so modifying it is unsafe in a concurrent backend.
It is also not necessary, since the Used marks
are only relevant for nodes in fn.Dcl.
For good measure, mark nodfp as always used.
Passes toolstash-check.
Updates #15756
Change-Id: I5320459f5eced2898615a17b395a10c1064bcaf5
Reviewed-on: https://go-review.googlesource.com/39200
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Dupok symbols may be defined in multiple packages. Its associated
package is chosen sort of arbitrarily (the first containing package
that the linker loads). Canonicalize its package to the package
with which it will be laid down in text, which is the first package
in dependency order that defines the symbol. So later passes (for
example, trampoline insertion pass) know that the dupok symbol
is laid down along with the package.
Fixes#19764.
Change-Id: I7cbc7474ff3016d5069c8b7be04af934abab8bc3
Reviewed-on: https://go-review.googlesource.com/39150
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
Reviewed-by: David Chase <drchase@google.com>
Each architecture's Rconv function is only used inside its
respective package, so it does not need to be exported.
Change-Id: Ifbd629964d7a9edd66501d7cdf4750621d66d646
Reviewed-on: https://go-review.googlesource.com/39110
Run-TryBot: Dave Cheney <dave@cheney.net>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This change makes it possible to retrieve the size of a file part
without having to Seek to determine file-size.
Resolves#19501
Change-Id: I7b9994c4cf41c9b06a046eb7046f8952ae1f15e9
Reviewed-on: https://go-review.googlesource.com/39223
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
For #13560.
Change-Id: I884e63f89d0756ca87b8c2092b4fd8360f791a2f
Reviewed-on: https://go-review.googlesource.com/39171
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Follow-up to review comments on CL 39193.
Change-Id: I7649af9d70ad73e039061a7a66fea416a7476192
Reviewed-on: https://go-review.googlesource.com/39199
Reviewed-by: Robert Griesemer <gri@golang.org>
A few gc.Node ops may be shared across functions.
The compiler is (mostly) already careful to avoid mutating them.
However, from a concurrency perspective, replacing (say)
an empty list with an empty list still counts as a mutation.
One place this occurs is orderinit. Avoid it.
This requires fixing one spot where shared nodes were mutated.
It doesn't result in any functional or performance changes.
Passes toolstash-check.
Updates #15756
Change-Id: I63c93b31baeeac62d7574804acb6b7f2bc9d14a9
Reviewed-on: https://go-review.googlesource.com/39196
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Round uses r+r < d to decide whether the remainder is
above or below half of d (to decide whether to round up or down).
This is wrong when r+r wraps negative, because it looks < d
but is really > d.
No one will ever care about rounding to a multiple of
d > 2⁶² (about 146 years), but might as well get it right.
Fixes#19807.
Change-Id: I1b55a742dc36e02a7465bc778bf5dd74fe71f7c0
Reviewed-on: https://go-review.googlesource.com/39151
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
The node in typenamesym requires neither
a position nor a curfn.
Passes toolstash-check.
Updates #15756
Change-Id: I6d39a8961e5578fe5924aaceb29045b6de2699df
Reviewed-on: https://go-review.googlesource.com/39194
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
newnamel is newname but with no dependency on lineno or Curfn.
This makes it suitable for use in a concurrent back end.
Use it now to make tempAt global-free.
The decision to push the assignment to n.Name.Curfn
to the caller of newnamel is based on mdempsky's
comments in #19683 that he'd like to do that
for callers of newname as well.
Passes toolstash-check. No compiler performance impact.
Updates #19683
Updates #15756
Change-Id: Idc461a1716916d268c9ff323129830d9a6e4a4d9
Reviewed-on: https://go-review.googlesource.com/39191
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Convert yyerrors into Fatals.
Remove the goto.
Move variable declaration closer to use.
Unify printing strings a bit.
Convert an int param into a bool.
Passes toolstash-check. No compiler performance impact.
Change-Id: I9017681417b785cf8693d18b124ac4f1ff37f2b5
Reviewed-on: https://go-review.googlesource.com/39170
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
The names never occur more than once,
so interning the results is counterproductive.
The impact is not very big, but neither is the fix.
name old time/op new time/op delta
Unicode 90.2ms ± 3% 88.3ms ± 5% -2.10% (p=0.000 n=94+98)
Change-Id: I1e3a24433db4ae0c9a6e98166568941824ff0779
Reviewed-on: https://go-review.googlesource.com/39193
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Also: Fix (testdata/gen/) copyGen.go, zeroGen.go, and arithConstGen.go
to actually match (testdata/) copy.go, zero.go, and arithConst.go, all
of which were manually edited in https://go-review.googlesource.com/20823
and https://go-review.googlesource.com/22748 despite the 'do not edit'
(or perhaps because it was missing in the case of arithConst.go).
For #13560.
Change-Id: I366e1b521e51885e0d318ae848760e5e14ccd488
Reviewed-on: https://go-review.googlesource.com/39172
Reviewed-by: Rob Pike <r@golang.org>
Prior to this CL, the SSA backend reported violations
of the //go:nowritebarrier annotation immediately.
This necessitated emitting errors during SSA compilation,
which is not compatible with a concurrent backend.
Instead, check for such violations later.
We already save the data required to do a late check
for violations of the //go:nowritebarrierrec annotation.
Use the same data, and check //go:nowritebarrier at the same time.
One downside to doing this is that now only a single
violation will be reported per function.
Given that this is for the runtime only,
and violations are rare, this seems an acceptable cost.
While we are here, remove several 'nerrors != 0' checks
that are rendered pointless.
Updates #15756Fixes#19250 (as much as it ever can be)
Change-Id: Ia44c4ad5b6fd6f804d9f88d9571cec8d23665cb3
Reviewed-on: https://go-review.googlesource.com/38973
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
We don't support stack frames over 2GB.
Rather than detect this during backend compilation,
check for it at the end of compilation.
This is arguably a more accurate check anyway,
since it takes into account the full frame,
including local stack, arguments, and arch-specific
rounding, although it's unlikely anyone would ever notice.
Also, rather than reporting the error right away,
take note of it and report it later, at the top level.
This is not relevant now, but it will help with making
the backend concurrent, as the append to the list of
oversized functions can be cheaply protected by a plain mutex.
Updates #15756
Updates #19250
Change-Id: Id3fa21906616d62e9dc66e27a17fd5f83304e96e
Reviewed-on: https://go-review.googlesource.com/38972
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
By checking GOARM in ssa/gen/ARM.rules, each intermediate operator
can be implemented via different instruction serials.
It is up to the user to choose between compitability and efficiency.
The Bswap32(x) is optimized to REV(x) when GOARM >= 6.
The CTZ(x) is optimized to CLZ(RBIT x) when GOARM == 7.
Change-Id: Ie9ee645fa39333fa79ad84ed4d1cefac30422814
Reviewed-on: https://go-review.googlesource.com/35610
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Starting in go1.9, the minimum processor requirement for ppc64 is POWER8. So it
may now use the same divWW implementation as ppc64le.
Updates #19074
Change-Id: If1a85f175cda89eee06a1024ccd468da6124c844
Reviewed-on: https://go-review.googlesource.com/39010
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
User defined numeric types such as "type Int int64" have
been able to be scanned into without a custom scanner by
using the reflect scan code path used to convert between
various numeric types. Add in a path for string types
for symmetry and least surprise.
Fixes#18101
Change-Id: I00553bcf021ffe6d95047eca0067ee94b54ff501
Reviewed-on: https://go-review.googlesource.com/39031
Run-TryBot: Daniel Theophanes <kardianos@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Rather than using arm64.Rconv directly in the archArm64 constructor
use the generic obj.Rconv helper. This removes the only use of
arm64.Rconv outside the arm64 package itself.
Change-Id: I99e9e7156b52cd26dc134f610f764ec794264e2c
Reviewed-on: https://go-review.googlesource.com/38756
Run-TryBot: Dave Cheney <dave@cheney.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
TestUnshareMountNameSpace fails on arm64 due to permission problems.
Skip that test for now when permission problems are encountered, so we
don't regress elsewhere in the meantime.
Updates #19698
Change-Id: I9058928afa474b813652c9489f343b8957160a6c
Reviewed-on: https://go-review.googlesource.com/39052
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Currently runtime.GC() triggers a STW GC. For common uses in tests and
benchmarks, it doesn't matter whether it's STW or concurrent, but for
uses in servers for things like collecting heap profiles and
controlling memory footprint, this pause can be a bit problem for
latency.
This changes runtime.GC() to trigger a concurrent GC. In order to
remain as close as possible to its current meaning, we define it to
always perform a full mark/sweep GC cycle before returning (even if
that means it has to finish up a cycle we're in the middle of first)
and to publish the heap profile as of the triggered mark termination.
While it must perform a full cycle, simultaneous runtime.GC() calls
can be consolidated into a single full cycle.
Fixes#18216.
Change-Id: I9088cc5deef4ab6bcf0245ed1982a852a01c44b5
Reviewed-on: https://go-review.googlesource.com/37520
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
sweepone returns ^uintptr(0) when there are no more spans to *start*
sweeping, but there may be spans being swept concurrently at the time
and there's currently no efficient way to tell when the sweeper is
done sweeping all the spans.
We'll need this for concurrent runtime.GC(), so add a count of the
number of active sweepone calls to make it possible to block until
sweeping is truly done.
This is also useful for more accurately printing the gcpacertrace,
since that should be printed after all of the sweeping stats are in
(currently we can print it slightly too early).
For #18216.
Change-Id: I06e6240c9e7b40aca6fd7b788bb6962107c10a0f
Reviewed-on: https://go-review.googlesource.com/37716
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Forced GCs don't provide good information about how to adjust the GC
trigger. Currently we avoid adjusting the trigger on forced GC because
forced GC is also STW and we don't adjust the trigger on STW GC.
However, this will become a problem when forced GC is concurrent.
Fix this by skipping trigger adjustment if the GC was user-forced.
For #18216.
Change-Id: I03dfdad12ecd3cfeca4573140a0768abb29aac5e
Reviewed-on: https://go-review.googlesource.com/38951
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently gcMode != gcBackgroundMode implies this was a user-forced GC
cycle. This is no longer going to be true when we make runtime.GC()
trigger a concurrent GC, so replace this with an explicit
work.userForced bit.
For #18216.
Change-Id: If7d71bbca78b5f0b35641b070f9d457f5c9a52bd
Reviewed-on: https://go-review.googlesource.com/37519
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently freeOSMemory calls gcStart directly, but we really just want
it to behave like runtime.GC() and then perform a scavenge, so make it
call runtime.GC() rather than gcStart.
For #18216.
Change-Id: I548ec007afc788e87d383532a443a10d92105937
Reviewed-on: https://go-review.googlesource.com/37518
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Now that the gcMode is no longer involved in the GC trigger condition,
we can simplify the triggering of forced GCs. By making the trigger
condition for forced GCs true even if gcphase is not _GCoff, we don't
need any special case path in gcStart to ensure that forced GCs don't
get consolidated.
Change-Id: I6067a13d76e40ff2eef8fade6fc14adb0cb58ee5
Reviewed-on: https://go-review.googlesource.com/37517
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently the GC triggering condition is an awkward combination of the
gcMode (whether or not it's gcBackgroundMode) and a boolean
"forceTrigger" flag.
Replace this with a new gcTrigger type that represents the range of
transition predicates we need. This has several advantages:
1. We can remove the awkward logic that affects the trigger behavior
based on the gcMode. Now gcMode purely controls whether to run a
STW GC or not and the gcTrigger controls whether this is a forced
GC that cannot be consolidated with other GC cycles.
2. We can lift the time-based triggering logic in sysmon to just
another type of GC trigger and move the logic to the trigger test.
3. This sets us up to have a cycle count-based trigger, which we'll
use to make runtime.GC trigger concurrent GC with the desired
consolidation properties.
For #18216.
Change-Id: If9cd49349579a548800f5022ae47b8128004bbfc
Reviewed-on: https://go-review.googlesource.com/37516
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Currently sysmon triggers periodic GC if GC is not currently running
and it's been long enough since the last GC. This misses some
important conditions; for example, whether GC is enabled at all by
GOGC. As a result, if GOGC is off, once we pass the timeout for
periodic GC, sysmon will attempt to trigger a GC every 10ms. This GC
will be a no-op because gcStart will check all of the appropriate
conditions and do nothing, but it still goes through the motions of
waking the forcegc goroutine and printing a gctrace line.
Fix this by making sysmon call gcShouldStart to check *all* of the
appropriate transition conditions before attempting to trigger a
periodic GC.
Fixes#19247.
Change-Id: Icee5521ce175e8419f934723849853d53773af31
Reviewed-on: https://go-review.googlesource.com/37515
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
