In many cases the records returned by Reader.Read will only be used between calls
to Read and become garbage once a new record is read. In this case, instead of
allocating a new slice on each call to Read, we can reuse the last allocated slice
for successive calls to avoid unnecessary allocations.

This change adds a new field ReuseRecord to the Reader struct to enable this reuse.

ReuseRecord is false by default to avoid breaking existing code which dependss on
the current behaviour.

I also added 4 new benchmarks, corresponding to the existing Read benchmarks, which
set ReuseRecord to true.

Benchstat on my local machine (old is ReuseRecord = false, new is ReuseRecord = true)

name                          old time/op    new time/op    delta
Read-8                          2.75µs ± 2%    1.88µs ± 1%  -31.52%  (p=0.000 n=14+15)
ReadWithFieldsPerRecord-8       2.75µs ± 0%    1.89µs ± 1%  -31.43%  (p=0.000 n=13+13)
ReadWithoutFieldsPerRecord-8    2.77µs ± 1%    1.88µs ± 1%  -32.06%  (p=0.000 n=15+15)
ReadLargeFields-8               55.4µs ± 1%    54.2µs ± 0%   -2.07%  (p=0.000 n=15+14)

name                          old alloc/op   new alloc/op   delta
Read-8                            664B ± 0%       24B ± 0%  -96.39%  (p=0.000 n=15+15)
ReadWithFieldsPerRecord-8         664B ± 0%       24B ± 0%  -96.39%  (p=0.000 n=15+15)
ReadWithoutFieldsPerRecord-8      664B ± 0%       24B ± 0%  -96.39%  (p=0.000 n=15+15)
ReadLargeFields-8               3.94kB ± 0%    2.98kB ± 0%  -24.39%  (p=0.000 n=15+15)

name                          old allocs/op  new allocs/op  delta
Read-8                            18.0 ± 0%       8.0 ± 0%  -55.56%  (p=0.000 n=15+15)
ReadWithFieldsPerRecord-8         18.0 ± 0%       8.0 ± 0%  -55.56%  (p=0.000 n=15+15)
ReadWithoutFieldsPerRecord-8      18.0 ± 0%       8.0 ± 0%  -55.56%  (p=0.000 n=15+15)
ReadLargeFields-8                 24.0 ± 0%      12.0 ± 0%  -50.00%  (p=0.000 n=15+15)

Fixes #19721

Change-Id: I79b14128bb9bb3465f53f40f93b1b528a9da6f58
Reviewed-on: https://go-review.googlesource.com/41730Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Some large testing/build systems require some form of test discovery before
running tests.  This usually allows for analytics, history, and stats on a per
tests basis.  Typically these systems are meant used in multi-language
environments and the original source code is not known or available.

This adds a -test.list option which takes a regular expression as an
argument. Any tests, benchmarks, or examples that match that regular
expression will be printed, one per line, to stdout and then the program
will exit.

Since subtests are named/discovered at run time this will only show
top-level tests names and is a known limitation.

Fixes #17209

Change-Id: I7e607f5f4f084d623a1cae88a1f70e7d92b7f13e
Reviewed-on: https://go-review.googlesource.com/41195Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
Run-TryBot: Marcel van Lohuizen <mpvl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

The Context definition to date has not defined what Err returns
before the Done channel is closed. Define that it returns nil,
as most implementations do.

All the standard context implementations (those in package
context and in golang.org/x/net/context) return Err() == nil
when Done is not yet closed. However, some non-standard
implementations may exist that return Err() != nil in this case,
as permitted by the Context definition before this date.
Call these "errorful implementations".

Because all the standard context implementations ensure that
Err() == nil when Done is not yet closed, clients now exist that
assume Err() != nil implies Done is closed and use calling Err
as a quick short-circuit check instead of first doing a non-blocking
receive from Done and then, if that succeeds, needing to call Err.
This assumption holds for all the standard Context implementations,
so these clients work fine in practice, even though they are making
unwarranted assumptions about the Context implementations.
Call these "technically incorrect clients".

If a technically incorrect client encounters an errorful
implementation, the client misbehaves. Because there are few
errorful implementations, over time we expect that many clients
will end up being technically incorrect without realizing it,
leading to latent, subtle bugs. If we want to eliminate these
latent, subtle bugs, there are two ways to do this:
either make errorful implementations more common
(exposing the client bugs more often) or redefine the Context
interface so that the clients are not buggy after all.

If we make errorful implementations more common, such
as by changing the standard context implementations to
return ErrNotDone instead of nil when Err is called before
Done is closed, this will shake out essentially all of the
technically incorrect clients, forcing people to find and fix
those clients during the transition to Go 1.9.
Technically this is allowed by the compatibility policy,
but we expect there are many pieces of code assuming
that Err() != nil means done, so updating will cause real pain.

If instead we disallow errorful implementations, then they
will need to be fixed as they are discovered, but the fault
will officially lie in the errorful Context implementation,
not in the clients. Technically this is disallowed by the compatibility
policy, because these errorful implementations were "correct"
in earlier versions of Go, except that they didn't work with
common client code. We expect there are hardly any errorful
implementations, so that disallowing them will be less disruptive
and more in the spirit of the compatibility policy.

This CL takes the path of expected least disruption,
narrowing the Context interface semantics and potentially
invalidating existing implementations. A survey of the
go-corpus v0.01 turned up only five Context implementations,
all trivial and none errorful (details in #19856).
We are aware of one early Context implementation inside Google,
from before even golang.org/x/net/context existed,
that is errorful. The misbehavior of an open-source library
when passed such a context is what prompted #19856.
That context implementation would be disallowed after this CL
and would need to be corrected. We are aware of no other
affected context implementations. On the other hand, a survey
of the go-corpus v0.01 turned up many instances of client
code assuming that Err() == nil implies not done yet
(details also in #19856). On balance, narrowing Context and
thereby allowing Err() == nil checks should invalidate significantly
less code than a push to flush out all the currently technically
incorrect Err() == nil checks.

If release feedback shows that we're wrong about this balance,
we can roll back this CL and try again in Go 1.10.

Fixes #19856.

Change-Id: Id45d126fac70e1fcc42d73e5a87ca1b66935b831
Reviewed-on: https://go-review.googlesource.com/40291
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Sameer Ajmani <sameer@golang.org>

Since close errors have been cleaned up in CL 39997,
TestCloseError is failing on Plan 9, because
TCPListener.Close didn't check that the listener
has already been closed before writing the "hangup"
string to the listener control file.

This change fixes TCPListener.Close on Plan 9,
by closing poll.FD before writing the "hangup"
string.

Fixes #20128.

Change-Id: I13862b23a9055dd1be658acef7066707d98c591f
Reviewed-on: https://go-review.googlesource.com/41850
Run-TryBot: David du Colombier <0intro@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: I251ae497b0ab237d4b3fe98e397052394142d437
Reviewed-on: https://go-review.googlesource.com/41653Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

This updates sha256.block and sha512.block to use vector instructions.  While
each round must still be performed independently, this allows for the use of
the vshasigma{w,d} crypto acceleration instructions.

For crypto/sha256:

benchmark               old ns/op     new ns/op     delta
BenchmarkHash8Bytes     570           300           -47.37%
BenchmarkHash1K         7529          3018          -59.91%
BenchmarkHash8K         55308         21938         -60.33%

benchmark               old MB/s     new MB/s     speedup
BenchmarkHash8Bytes     14.01        26.58        1.90x
BenchmarkHash1K         136.00       339.23       2.49x
BenchmarkHash8K         148.11       373.40       2.52x

For crypto/sha512:

benchmark               old ns/op     new ns/op     delta
BenchmarkHash8Bytes     725           394           -45.66%
BenchmarkHash1K         5062          2107          -58.38%
BenchmarkHash8K         34711         13918         -59.90%

benchmark               old MB/s     new MB/s     speedup
BenchmarkHash8Bytes     11.03        20.29        1.84x
BenchmarkHash1K         202.28       485.84       2.40x
BenchmarkHash8K         236.00       588.56       2.49x

Fixes #20069

Change-Id: I28bffe6e9eb484a83a004116fce84acb4942abca
Reviewed-on: https://go-review.googlesource.com/41391
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Carlos Eduardo Seo <cseo@linux.vnet.ibm.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>

This may improve perormance during concurrent access
to mheap.central array from multiple CPU cores.

Change-Id: I8f48dd2e72aa62e9c32de07ae60fe552d8642782
Reviewed-on: https://go-review.googlesource.com/41550Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Moved the relevant file.close() usages close to after the
file opens and put them in defer statements, so that readers
don't have to think too much as to where the file is
being closed.

Change-Id: Ic4190b02ea2f5ac281b9ba104e0023e9f87ca8c7
Reviewed-on: https://go-review.googlesource.com/41796Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Catch all the cases where a file operation might return ErrFileClosing,
and convert to ErrClosed. Use a new method for the conversion, which
permits us to remove some KeepAlive calls.

Change-Id: I584178f297efe6cb86f3090b2341091b412f1041
Reviewed-on: https://go-review.googlesource.com/41793
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: Id5aa4a1499068bf2d3497b21d794f970b7e47fdf
Reviewed-on: https://go-review.googlesource.com/41795
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Grand savings: 6 bits.

Change-Id: I364be54cc41534689e01672ed0fe2c10a560d3d4
Reviewed-on: https://go-review.googlesource.com/41794
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Change-Id: I30c59ba84dcacc3de39c42f94484b47bb7c36eba
Reviewed-on: https://go-review.googlesource.com/41792
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Resolve import paths to get plugin symbol prefixes.

Fixes #19534

Change-Id: Ic25d83e72465ba8f6be0337218a1627b5dc702dc
Reviewed-on: https://go-review.googlesource.com/40994
Run-TryBot: Todd Neal <todd@tneal.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

The LocalAddrContext should have the network address of the actual
interface.

Fixes #18686

Change-Id: I9c401eda312f3a0e7e65b013af827aeeef3b4d3d
Reviewed-on: https://go-review.googlesource.com/35490
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Node.Walkdef is 0, 1, or 2, so it only requires two bits.
Add support for 2-bit values to bitset,
and use it for Node.Walkdef.

Class, Embedded, Typecheck, and Initorder will follow suit
in subsequent CLs.

The multi-bit flags will go at the beginning,
since that generates (marginally) more efficient code.

Change-Id: Id6e2e66e437f10aaa05b8a6e1652efb327d06128
Reviewed-on: https://go-review.googlesource.com/41791
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

It is no longer used.

Change-Id: Id64f387867a0503d13eaecda12e6606682c24595
Reviewed-on: https://go-review.googlesource.com/41790
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

In the past we returned "use of closed network connection" when using
a closed network descriptor in some way. In CL 36799 that was changed
to return "use of closed file or network connection". Because programs
have no access to a value of this error type (see issue #4373) they
resort to doing direct string comparisons (see issue #19252). This CL
restores the old error string so that we don't break programs
unnecessarily with the 1.9 release.

This adds a test to the net package for the expected string.

For symmetry check that the os package returns the expected error,
which for os already exists as os.ErrClosed.

Updates #4373.
Fixed #19252.

Change-Id: I5b83fd12cfa03501a077cad9336499b819f4a38b
Reviewed-on: https://go-review.googlesource.com/39997
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

In addition to being more compact,
this makes the code a lot clearer.

Change-Id: Ibcb70526c2e5913dcf34904fda194e3585228c3f
Reviewed-on: https://go-review.googlesource.com/41761
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

node.Likely may once have held -1/0/+1,
but it is now only 0/1.

With improved SSA heuristics,
it may someday go away entirely.

Change-Id: I6451d17fd7fb47e67fea4d39df302b6db00ea57b
Reviewed-on: https://go-review.googlesource.com/41760
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

It was added in Go 1.7. Also gofmt while at it.

Change-Id: Idb65fb44e2f2a4365dceea3f833aeb51a8d12333
Reviewed-on: https://go-review.googlesource.com/41692
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Updates #18243

Change-Id: I1fe0af65dbd52c3e8e0a245e4cbbdfca100971b4
Reviewed-on: https://go-review.googlesource.com/41759
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

This updates the bundled http2 package from git rev
5602c733f70afc6dcec6766be0d5034d4c4f14de of the x/net repo for:

  http2: Use NO_ERROR instead of CANCEL when responding before the request is finished
  https://golang.org/cl/40630

  http2: enforce write deadline per stream
  https://golang.org/cl/34727

Updates golang/go#19948
Fixes golang/go#18437

Change-Id: I14500476e91551fa8f27a1aeb8ae3cac9600b74c
Reviewed-on: https://go-review.googlesource.com/41753Reviewed-by: Kale Blankenship <kale@lemnisys.com>
Reviewed-by: Tom Bergan <tombergan@google.com>
Run-TryBot: Kale Blankenship <kale@lemnisys.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Updates golang_org/x/net/route to rev da118f7 for:
- route: don't fail test when at least one version of INET protocols is available

Updates #19298.
Updates #19967.

Change-Id: I46948f1bd4ac6e6afd424623233f90e2b6b954c6
Reviewed-on: https://go-review.googlesource.com/41652
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Updates golang_org/x/net/lif to rev a25ba90 for:
- lif: don't fail test when at least one version of INET protocols is available

Updates #19967.

Change-Id: I4b946a4c6eee7938193688ecbfc4a9d69d88c94e
Reviewed-on: https://go-review.googlesource.com/41651
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Change-Id: I34547b057605bb9e1e2227c41867589348560244
Reviewed-on: https://go-review.googlesource.com/41513
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Cleanup CL https://golang.org/cl/41691 broke the plan9 build by removing
a use of a package but not removing the package import.

Trybots don't check that. I filed #20119 for that.

Change-Id: Ia030e6924665dfb871ca964455b899d51b0200c2
Reviewed-on: https://go-review.googlesource.com/41752Reviewed-by: David du Colombier <0intro@gmail.com>

In an effort to at least understand the complete set of things not
working on Alpine Linux, I've been trying to get the build passing
again, even with tests disabled.

The race detector is broken on Alpine. That is #14481 (and #9918).
So disable those tests for now.

Also, internal linking with PIE doesn't work on Alpine yet.
That is #18243. So disable that test for now.

With this CL, all.bash almost passes. There's some cgo test failing
still, but there's no bug yet, so that can be a separate CL.

Change-Id: I3ffbb0e787ed54cb82f298b6bd5bf3ccfbc82622
Reviewed-on: https://go-review.googlesource.com/41678
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Version 4 generated with toolchain at commit 51012314.
Version 5 generated with toolchain at commit a6b16e00.

Change-Id: If11ec8b3357f0f71776c15665e4d5228b3842ff7
Reviewed-on: https://go-review.googlesource.com/41710
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Use -64 instead of 0 as the magic "new file"
line delta, since it is much less common.

Use a new path encoding that breaks up paths
into /-separated components, allowing
reuse of the component strings, and making
many re-used paths a single byte to encode.

Bump the export version to 5.

Fixes #20080

name        old export-bytes  new export-bytes  delta
Template          19.1k ± 0%        17.4k ± 0%  -8.74%  (p=0.008 n=5+5)
Unicode           4.47k ± 0%        4.42k ± 0%  -0.96%  (p=0.008 n=5+5)
GoTypes           29.9k ± 0%        27.6k ± 0%  -7.41%  (p=0.008 n=5+5)
Compiler          71.4k ± 0%        65.4k ± 0%  -8.45%  (p=0.008 n=5+5)
SSA               67.8k ± 0%        65.6k ± 0%  -3.38%  (p=0.008 n=5+5)
Flate             4.99k ± 0%        4.79k ± 0%  -3.91%  (p=0.008 n=5+5)
GoParser          8.77k ± 0%        7.97k ± 0%  -9.14%  (p=0.008 n=5+5)
Reflect           6.27k ± 0%        6.13k ± 0%  -2.22%  (p=0.008 n=5+5)
Tar               9.46k ± 0%        8.82k ± 0%  -6.69%  (p=0.008 n=5+5)
XML               16.0k ± 0%        14.9k ± 0%  -6.69%  (p=0.008 n=5+5)
[Geo mean]        14.8k             14.0k       -5.80%

Change-Id: Iea0c8c62e61dbab3cfd14ee121e34845c85f00d2
Reviewed-on: https://go-review.googlesource.com/41619
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

isifacemethod accessed thisT without checking if it was initialized,
opening the possibility for a bug during type checking. Give better
name, move it to package types, and provide accessor instead.

Change-Id: I29ffc408252a4ba4ef1de218fa154397786c9be6
Reviewed-on: https://go-review.googlesource.com/41673Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

This comment is very useful but still refers to the C implementation.
Adapting it for Go is fairly straightforward though.

Change-Id: Ib6dde25f3a18acbce76bb3cffdc29f5ccf43c1f7
Reviewed-on: https://go-review.googlesource.com/41696Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The assembler reordered the operands of some instructions to put the
first operand into From3. Unfortunately this meant that when the
instructions were printed the operands were in a different order than
the assembler would expect as input. For example, 'MVC $8, (R1), (R2)'
would be printed as 'MVC (R1), $8, (R2)'.

Originally this was done to ensure that From contained the source
memory operand. The current compiler no longer requires this and so
this CL simply makes all instructions use the standard order for
operands: From, Reg, From3 and finally To.

Fixes #18295

Change-Id: Ib2b5ec29c647ca7a995eb03dc78f82d99618b092
Reviewed-on: https://go-review.googlesource.com/40299
Run-TryBot: Michael Munday <munday@ca.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

Breaks are implicit, and since there is no outer loop this one could not
mean a loop break that was missing a label.

Change-Id: Ie91018db1825aa8285c1aa55c9d28fc7ec7148af
Reviewed-on: https://go-review.googlesource.com/39691
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Mostly unnecessary *testing.T arguments.

Found with github.com/mvdan/unparam.

Change-Id: Ifb955cb88f2ce8784ee4172f4f94d860fa36ae9a
Reviewed-on: https://go-review.googlesource.com/41691
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Now that the os package uses internal/poll on Unix and Windows systems,
it can rely on internal/poll reference counting to ensure that the
file descriptor is not closed until all I/O is complete.

That was already working. This CL completes the job by not trying to
modify the Sysfd field when it might still be used by the I/O routines.

Fixes #7970

Change-Id: I7a3daa1a6b07b7345bdce6f0cd7164bd4eaee952
Reviewed-on: https://go-review.googlesource.com/41674Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

This change adds a better asm implementation of addVV for ppc64x, with speedups
up to nearly 3x in the best cases.

benchmark                   old ns/op     new ns/op     delta
BenchmarkAddVV/1-8          7.33          5.81          -20.74%
BenchmarkAddVV/2-8          8.72          6.49          -25.57%
BenchmarkAddVV/3-8          10.5          7.08          -32.57%
BenchmarkAddVV/4-8          12.7          7.57          -40.39%
BenchmarkAddVV/5-8          14.3          8.06          -43.64%
BenchmarkAddVV/10-8         27.6          11.1          -59.78%
BenchmarkAddVV/100-8        218           82.4          -62.20%
BenchmarkAddVV/1000-8       2064          718           -65.21%
BenchmarkAddVV/10000-8      20536         7153          -65.17%
BenchmarkAddVV/100000-8     211004        72403         -65.69%

benchmark                   old MB/s     new MB/s     speedup
BenchmarkAddVV/1-8          8729.74      11006.26     1.26x
BenchmarkAddVV/2-8          14683.65     19707.55     1.34x
BenchmarkAddVV/3-8          18226.96     27103.63     1.49x
BenchmarkAddVV/4-8          20204.50     33805.81     1.67x
BenchmarkAddVV/5-8          22348.64     39694.06     1.78x
BenchmarkAddVV/10-8         23212.74     57631.08     2.48x
BenchmarkAddVV/100-8        29300.07     77629.53     2.65x
BenchmarkAddVV/1000-8       31000.56     89094.54     2.87x
BenchmarkAddVV/10000-8      31163.61     89469.16     2.87x
BenchmarkAddVV/100000-8     30331.16     88393.73     2.91x

It also adds the use of CTR for the loop counter in subVV, instead of
manually updating the loop counter. This is slightly faster.

Change-Id: Ic4b05cad384fd057972d46a5618ed5c3039d7460
Reviewed-on: https://go-review.googlesource.com/41010
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>

As discussion in issue #18293, "MOVW $Imm-16, Reg" was introduced in
ARMv7. It directly encoded the 16-bit immediate into the instruction
instead of put it in the constant pool.

This patch makes the arm assembler choose this form of MOVW if available.

Besides 4 bytes are saved in the constant pool, the go1 benchmark test
also shows a slight improvement.

name                     old time/op    new time/op    delta
BinaryTree17-4              42.7s ± 1%     42.7s ± 1%    ~     (p=0.304 n=50+50)
Fannkuch11-4                24.8s ± 1%     24.8s ± 0%    ~     (p=0.757 n=50+49)
FmtFprintfEmpty-4           875ns ± 1%     873ns ± 2%    ~     (p=0.066 n=44+46)
FmtFprintfString-4         1.43µs ± 1%    1.45µs ± 1%  +1.68%  (p=0.000 n=44+44)
FmtFprintfInt-4            1.52µs ± 1%    1.52µs ± 1%  +0.26%  (p=0.009 n=41+45)
FmtFprintfIntInt-4         2.19µs ± 1%    2.20µs ± 1%  +0.76%  (p=0.000 n=43+46)
FmtFprintfPrefixedInt-4    2.56µs ± 2%    2.53µs ± 1%  -1.03%  (p=0.000 n=45+44)
FmtFprintfFloat-4          4.41µs ± 1%    4.39µs ± 1%  -0.52%  (p=0.000 n=44+44)
FmtManyArgs-4              9.02µs ± 2%    9.04µs ± 1%  +0.27%  (p=0.000 n=46+44)
GobDecode-4                 106ms ± 1%     106ms ± 1%    ~     (p=0.310 n=45+43)
GobEncode-4                88.1ms ± 2%    88.0ms ± 2%    ~     (p=0.648 n=49+50)
Gzip-4                      4.31s ± 1%     4.27s ± 1%  -1.01%  (p=0.000 n=50+50)
Gunzip-4                    618ms ± 1%     608ms ± 1%  -1.65%  (p=0.000 n=45+47)
HTTPClientServer-4          689µs ± 6%     692µs ± 4%  +0.52%  (p=0.038 n=50+47)
JSONEncode-4                282ms ± 2%     280ms ± 1%  -0.75%  (p=0.000 n=46+43)
JSONDecode-4                945ms ± 2%     940ms ± 1%  -0.47%  (p=0.000 n=47+47)
Mandelbrot200-4            49.4ms ± 1%    49.3ms ± 1%    ~     (p=0.163 n=45+45)
GoParse-4                  46.0ms ± 3%    45.5ms ± 2%  -0.95%  (p=0.000 n=49+40)
RegexpMatchEasy0_32-4      1.29µs ± 1%    1.28µs ± 1%  -0.14%  (p=0.005 n=38+45)
RegexpMatchEasy0_1K-4      7.92µs ± 8%    7.75µs ± 6%  -2.12%  (p=0.000 n=47+50)
RegexpMatchEasy1_32-4      1.31µs ± 1%    1.31µs ± 0%    ~     (p=0.282 n=45+48)
RegexpMatchEasy1_1K-4      10.4µs ± 5%    10.4µs ± 3%    ~     (p=0.771 n=50+49)
RegexpMatchMedium_32-4     2.06µs ± 1%    2.07µs ± 1%  +0.35%  (p=0.001 n=44+49)
RegexpMatchMedium_1K-4      533µs ± 1%     532µs ± 1%    ~     (p=0.710 n=43+47)
RegexpMatchHard_32-4       29.7µs ± 1%    29.6µs ± 1%  -0.34%  (p=0.002 n=43+46)
RegexpMatchHard_1K-4        893µs ± 2%     885µs ± 1%  -0.85%  (p=0.000 n=50+45)
Revcomp-4                  85.6ms ± 4%    85.5ms ± 2%    ~     (p=0.683 n=50+50)
Template-4                  1.05s ± 3%     1.04s ± 1%  -1.06%  (p=0.000 n=50+44)
TimeParse-4                7.19µs ± 2%    7.11µs ± 2%  -1.10%  (p=0.000 n=48+46)
TimeFormat-4               13.4µs ± 1%    13.5µs ± 1%    ~     (p=0.056 n=46+49)
[Geo mean]                  747µs          745µs       -0.28%

name                     old speed      new speed      delta
GobDecode-4              7.23MB/s ± 1%  7.22MB/s ± 1%    ~     (p=0.062 n=45+39)
GobEncode-4              8.71MB/s ± 2%  8.72MB/s ± 2%    ~     (p=0.656 n=49+50)
Gzip-4                   4.50MB/s ± 1%  4.55MB/s ± 1%  +1.03%  (p=0.000 n=50+50)
Gunzip-4                 31.4MB/s ± 1%  31.9MB/s ± 1%  +1.67%  (p=0.000 n=45+47)
JSONEncode-4             6.89MB/s ± 2%  6.94MB/s ± 1%  +0.76%  (p=0.000 n=46+43)
JSONDecode-4             2.05MB/s ± 2%  2.06MB/s ± 2%  +0.32%  (p=0.017 n=47+50)
GoParse-4                1.26MB/s ± 3%  1.27MB/s ± 1%  +0.68%  (p=0.000 n=50+48)
RegexpMatchEasy0_32-4    24.9MB/s ± 1%  24.9MB/s ± 1%  +0.13%  (p=0.004 n=38+45)
RegexpMatchEasy0_1K-4     129MB/s ± 7%   132MB/s ± 6%  +2.34%  (p=0.000 n=46+50)
RegexpMatchEasy1_32-4    24.5MB/s ± 1%  24.4MB/s ± 1%    ~     (p=0.252 n=45+48)
RegexpMatchEasy1_1K-4    98.8MB/s ± 4%  98.7MB/s ± 3%    ~     (p=0.771 n=50+49)
RegexpMatchMedium_32-4    485kB/s ± 3%   480kB/s ± 0%  -0.95%  (p=0.000 n=50+38)
RegexpMatchMedium_1K-4   1.92MB/s ± 1%  1.92MB/s ± 1%    ~     (p=0.129 n=43+47)
RegexpMatchHard_32-4     1.08MB/s ± 2%  1.08MB/s ± 1%  +0.38%  (p=0.017 n=46+46)
RegexpMatchHard_1K-4     1.15MB/s ± 2%  1.16MB/s ± 1%  +0.67%  (p=0.001 n=50+49)
Revcomp-4                29.7MB/s ± 4%  29.7MB/s ± 2%    ~     (p=0.682 n=50+50)
Template-4               1.85MB/s ± 3%  1.87MB/s ± 1%  +1.04%  (p=0.000 n=50+44)
[Geo mean]               6.56MB/s       6.60MB/s       +0.47%


Change-Id: Ic2cca90133c27a08d9f1a23c65b0eed5fbd02684
Reviewed-on: https://go-review.googlesource.com/41190
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

s/arm64/amd64/ in previous typo CL 41628

Updates #19938
Updates #18243

Change-Id: I282244ee3c94535f229a87b6246382385ff64428
Reviewed-on: https://go-review.googlesource.com/41675Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Reduces cmd/go by 4464 bytes on amd64.

Removes the duplicate detection of AVX support and
presence of Intel processors.

Change-Id: I4670189951a63760fae217708f68d65e94a30dc5
Reviewed-on: https://go-review.googlesource.com/41570Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Updates #19938
Updates #18243

Change-Id: Ib6e704c0a5d596bdfaa6493902d2528bec55bf16
Reviewed-on: https://go-review.googlesource.com/41628Reviewed-by: Ian Lance Taylor <iant@golang.org>