The cache gets a 62% hit rate while compiling
the standard library.


name      old time/op    new time/op    delta
Template     449ms ± 2%     443ms ± 4%  -1.40%  (p=0.006 n=23+25)
GoTypes      1.54s ± 1%     1.50s ± 2%  -2.53%  (p=0.000 n=22+22)
Compiler     5.51s ± 1%     5.39s ± 1%  -2.29%  (p=0.000 n=23+25)

name      old alloc/op   new alloc/op   delta
Template    90.4MB ± 0%    90.0MB ± 0%  -0.45%  (p=0.000 n=25+25)
GoTypes      334MB ± 0%     331MB ± 0%  -1.05%  (p=0.000 n=25+25)
Compiler    1.12GB ± 0%    1.10GB ± 0%  -1.57%  (p=0.000 n=25+24)

name      old allocs/op  new allocs/op  delta
Template      681k ± 0%      682k ± 0%  +0.26%  (p=0.000 n=25+25)
GoTypes      2.23M ± 0%     2.23M ± 0%  +0.05%  (p=0.000 n=23+24)
Compiler     6.46M ± 0%     6.46M ± 0%  +0.02%  (p=0.000 n=24+25)


Change-Id: I2629c291892827493d7b55ec4d83f6973a2ab133
Reviewed-on: https://go-review.googlesource.com/20026Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>

(Last?) Semi-regular merge from tip to dev.ssa.

Conflicts:
	src/cmd/compile/internal/gc/closure.go
	src/cmd/compile/internal/gc/gsubr.go
	src/cmd/compile/internal/gc/lex.go
	src/cmd/compile/internal/gc/pgen.go
	src/cmd/compile/internal/gc/syntax.go
	src/cmd/compile/internal/gc/walk.go
	src/cmd/internal/obj/pass.go

Change-Id: Ib5ea8bf74d420f4902a9c6208761be9f22371ae7

It gets rewritten to an xor by the linker also.

Change-Id: Iae35130325d41bd1a09b7e971190cae6f4e17fac
Reviewed-on: https://go-review.googlesource.com/20058Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

This is a AMD64 version of CL19743.
Saves additional 1574 bytes in go binary.
This also speeds up bzip2 by 1-4%

Change-Id: I031ba423663c4e83fdefe44e5296f24143e303da
Reviewed-on: https://go-review.googlesource.com/19939
Run-TryBot: Ilya Tocar <ilya.tocar@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

Movups is 1 byte smaller than movapd that we currently use.

Change-Id: I22f771f066529352722a28543535ec43497cb9c5
Reviewed-on: https://go-review.googlesource.com/19938Reviewed-by: David Chase <drchase@google.com>

Avoid targeting a partial register with load;
ensure source of load (writebarrier) is aligned.

Better yet would be "CMPB $1,writebarrier" but that requires
wrestling with flagalloc (mem operand complicates moving
instruction around).

Didn't see a change in time for
   benchcmd -n 10 Build go build net/http

Verified that we clean the code up properly:
   0x20a8 <main.main+104>:	mov    0xc30a2(%rip),%eax
                            # 0xc5150 <runtime.writeBarrier>
   0x20ae <main.main+110>:	test   %al,%al

Change-Id: Id5fb8c260eaec27bd727cb0ae1476c60343b0986
Reviewed-on: https://go-review.googlesource.com/19998Reviewed-by: Keith Randall <khr@golang.org>

Exposed data already in sdom to avoid recreating it in prove.

Change-Id: I834c9c03ed8faeaee013e5a1b3f955908f0e0915
Reviewed-on: https://go-review.googlesource.com/19999
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alexandru Moșoi <alexandru@mosoi.ro>

* It does very simple bounds checking elimination. E.g.
removes the second check in for i := range a { a[i]++; a[i++]; }
* Improves on the following redundant expression:
return a6 || (a6 || (a6 || a4)) || (a6 || (a4 || a6 || (false || a6)))
* Linear in the number of block edges.

I patched in CL 12960 that does bounds, nil and constant propagation
to make sure this CL is not just redundant. Size of pkg/tool/linux_amd64/*
(excluding compile which is affected by this change):

With IsInBounds and IsSliceInBounds
-this -12960 92285080
+this -12960 91947416
-this +12960 91978976
+this +12960 91923088

Gain is ~110% of 12960.

Without IsInBounds and IsSliceInBounds (older run)
-this -12960 95515512
+this -12960 95492536
-this +12960 95216920
+this +12960 95204440

Shaves 22k on its own.

* Can we handle IsInBounds better with this? In
for i := range a { a[i]++; } the bounds checking at a[i]
is not eliminated.

Change-Id: I98957427399145fb33693173fd4d5a8d71c7cc20
Reviewed-on: https://go-review.googlesource.com/19710Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Add the max arg length to opcodes and use it in zcse.  Doesn't affect
speed, but allows better checking in checkFunc and removes the need
to keep a list of zero arg opcodes up to date.

Change-Id: I157c6587154604119720ec6228b767b6e52bb5c7
Reviewed-on: https://go-review.googlesource.com/19994Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Todd Neal <todd@tneal.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #14483.

Change-Id: I0cddfe27fd8d00ba85659d0b618410e39ebf45cb
Reviewed-on: https://go-review.googlesource.com/19860Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Update #14473.

Change-Id: Iba1ecf42d9ab5a93144941439d5cc6b0b4f4a3ac
Reviewed-on: https://go-review.googlesource.com/19992Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Once upon a time fmt did use bytes.Buffer for its buffer.
The buffer write methods still mimic the bytes.Buffer signatures.
The current code depends on manipulating the buffer []bytes array directly
which makes going back to bytes.Buffer by only changing the type of buffer
impossible. Since type buffer is not exported the methods can be simplified
to the needs of fmt. This saves space and avoids unnecessary overhead.

Use WriteString instead of Write for known inputs since
WriteString is faster than Write to append the same data.
This also saves space in the binary.

Remove the add method from Printer and depending on the data to be written
use WriteRune or WriteByte directly instead.

In total makes the go binary around 4 kilobyte smaller.

name                  old time/op  new time/op  delta
SprintfEmpty-2        24.1ns ± 3%  23.8ns ± 1%  -1.14%  (p=0.000 n=20+20)
SprintfString-2        114ns ± 2%   114ns ± 4%    ~     (p=0.558 n=20+19)
SprintfInt-2           116ns ± 9%   118ns ± 7%    ~     (p=0.086 n=20+20)
SprintfIntInt-2        195ns ± 6%   193ns ± 5%    ~     (p=0.345 n=20+19)
SprintfPrefixedInt-2   251ns ±16%   241ns ± 9%  -3.69%  (p=0.024 n=20+19)
SprintfFloat-2         203ns ± 4%   205ns ± 5%    ~     (p=0.153 n=20+20)
SprintfBoolean-2       101ns ± 7%    96ns ±11%  -5.23%  (p=0.005 n=19+20)
ManyArgs-2             651ns ± 7%   628ns ± 7%  -3.44%  (p=0.002 n=20+20)
FprintInt-2            164ns ± 2%   158ns ± 2%  -3.62%  (p=0.000 n=20+18)
FprintfBytes-2         215ns ± 1%   216ns ± 1%  +0.58%  (p=0.000 n=20+20)
FprintIntNoAlloc-2     115ns ± 0%   112ns ± 0%  -2.61%  (p=0.000 n=20+20)
ScanInts-2             700µs ± 0%   702µs ± 1%  +0.38%  (p=0.000 n=18+20)
ScanRecursiveInt-2    82.7ms ± 0%  82.7ms ± 0%    ~     (p=0.820 n=20+20)

Change-Id: I0409eb170b8a26d9f4eb271f6292e5d39faf2d8b
Reviewed-on: https://go-review.googlesource.com/19955Reviewed-by: Rob Pike <r@golang.org>

The current implementations of the AppendQuote functions use quoteWith
(through Quote) for quoting the given value and appends the returned
string to the dst byte slice. quoteWith internally creates a byte slice
on each call which gets converted to a string in Quote.

This means the AppendQuote functions always allocates a new byte slice
and a string only to append them to an existing byte slice. In the case
of (Append)QuoteRune the string passed to quoteWith will also needs to
be allocated from a rune first.

Split quoteWith into two functions (quoteWith and appendQuotedWith) and
replace the call to Quote inside AppendQuote with appendQuotedWith,
which appends directly to the byte slice passed to AppendQuote and also
avoids the []byte->string conversion.

Also introduce the 2 functions quoteRuneWith and appendQuotedRuneWith
that work the same way as quoteWith and appendQuotedWith, but take a
single rune instead of a string, to avoid allocating a new string when
appending a single rune, and use them in (Append)QuoteRune.

Also update the ToASCII and ToGraphic variants to use the new functions.

Benchmark results:

benchmark                      old ns/op     new ns/op     delta
BenchmarkQuote-8               428           503           +17.52%
BenchmarkQuoteRune-8           148           105           -29.05%
BenchmarkAppendQuote-8         435           307           -29.43%
BenchmarkAppendQuoteRune-8     158           23.5          -85.13%

benchmark                      old allocs     new allocs     delta
BenchmarkQuote-8               3              3              +0.00%
BenchmarkQuoteRune-8           3              2              -33.33%
BenchmarkAppendQuote-8         3              0              -100.00%
BenchmarkAppendQuoteRune-8     3              0              -100.00%

benchmark                      old bytes     new bytes     delta
BenchmarkQuote-8               144           144           +0.00%
BenchmarkQuoteRune-8           16            16            +0.00%
BenchmarkAppendQuote-8         144           0             -100.00%
BenchmarkAppendQuoteRune-8     16            0             -100.00%

Change-Id: I77c148d5c7242f1b0edbbeeea184878abb51a522
Reviewed-on: https://go-review.googlesource.com/18962
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

This is a followup change to #13111 for filtering out IPv6 literals and
absolute FQDNs from being as the SNI values.

Updates #13111.
Fixes #14404.

Change-Id: I09ab8d2a9153d9a92147e57ca141f2e97ddcef6e
Reviewed-on: https://go-review.googlesource.com/19704Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Move the decision if zero padding is allowed to doPrintf
where the other formatting decisions are made.

Removes some dead code for negative f.wid that was never used
due to f.wid always being positive and f.minus deciding if left
or right padding should be used.

New padding code writes directly into the buffer and is as fast
as the old version but avoids the cost of needing package init.

name              old time/op  new time/op  delta
SprintfPadding-2   246ns ± 5%   245ns ± 4%   ~     (p=0.345 n=50+47)

Change-Id: I7dfddbac8e328f4ef0cdee8fafc0d06c784b2711
Reviewed-on: https://go-review.googlesource.com/19957
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

Accidentally added in https://golang.org/cl/19968.

Change-Id: Id70917c4d1f69db149688d797c90a19557d16f72
Reviewed-on: https://go-review.googlesource.com/19985Reviewed-by: Minux Ma <minux@golang.org>

Plan 9 doesn't define main, so the INITENTRY
symbol remains with the SXREF type, which leads
Entryvalue to fail on "entry not text: main".

Fixes #14536.

Change-Id: Id9b7d61e5c2202aba3ec9cd52f5b56e0a38f7c47
Reviewed-on: https://go-review.googlesource.com/19973
Run-TryBot: David du Colombier <0intro@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

plive doesn't like the fact that we put JMPs right
after CALL ops to select{send,recv}.

Fixes SSA -N build.

Change-Id: I9b3c9e5293196094fd5a6206dd2f99784951f7a9
Reviewed-on: https://go-review.googlesource.com/19982
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

Change-Id: I6ac3d11ee8896f636235fe10c2556f93584019b5
Reviewed-on: https://go-review.googlesource.com/19984Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Split the syms array into separate basicTypes and builtinFuncs arrays.

Also, in lexfini, instead of duplicating the code from lexinit to
declare the builtin identifiers in the user package, just import them
from builtinpkg like how importdot works.

Change-Id: Ic3b3b454627a46f7bd5f290d0e31443e659d431f
Reviewed-on: https://go-review.googlesource.com/19936
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

Introduces a new types Nodes that can be used to replace NodeList.

Update #14473.

Change-Id: Id77c5dcae0cbeb898ba12dd46bd400aad408871c
Reviewed-on: https://go-review.googlesource.com/19969Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

All io.Reader that are passed to newScanState in all the standard
library tests that implement io.RuneReader also implement io.RuneScanner.

Do not check on each call ScanState's UnreadRune that the used RuneReader
also implements the UnreadRune method by using a private interface.
Instead require the used Reader to implement the public RuneScanner
interface.

The extra implementation logic for UnreadRune is removed from ScanState.
Instead the readRune wrapper is extended to implement UnreadRune for the
RuneScanner interface. If the Reader passed to newScanstate does not
implement RuneScanner the readRune wrapper is used to implement the
missing functionality.

Note that a RuneReader that does not implement RuneScanner will also
be wrapped by runeRead which was not the case before.
Performance with the readRune wrapper is better than without before.

Add benchmark to compare performance with and without using the
readRune wrapper.

name                             old time/op  new time/op  delta
ScanInts-2                        704µs ± 0%   615µs ± 1%  -12.73%  (p=0.000 n=20+20)
ScanRecursiveInt-2               82.6ms ± 0%  51.4ms ± 0%  -37.71%  (p=0.000 n=20+20)
ScanRecursiveIntReaderWrapper-2  85.1ms ± 0%  52.4ms ± 0%  -38.36%  (p=0.000 n=20+20)

Change-Id: I8c6e85db9b87a8171caab12f020b6e256b498e81
Reviewed-on: https://go-review.googlesource.com/19895
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

Pull all alg-related code into its own file.
subr.go is a Hobbesian Leviathan.

100% code movement. Cleanup and improvements to follow.

Change-Id: Ib9c8f66563fdda90c6e8cf646d366a9487a4648d
Reviewed-on: https://go-review.googlesource.com/19980Reviewed-by: Dave Cheney <dave@cheney.net>
Run-TryBot: Dave Cheney <dave@cheney.net>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

While here, merge LINC and LDEC into LINCOP.

Fixes #13244.

Change-Id: I8ea426f986d60d35c3b1a80c056a7aa49d22d802
Reviewed-on: https://go-review.googlesource.com/19928Reviewed-by: Robert Griesemer <gri@golang.org>

Save a few bytes in Func.

Passes toolstash -cmp.

Update #14473.

Change-Id: I824fa7d5cb2d93f6f59938ccd86114abcbea0043
Reviewed-on: https://go-review.googlesource.com/19968Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Passes toolstash -cmp.

Update #14473.

Change-Id: I7285175b1992a29033fdc9e81d6f30545e5cc30d
Reviewed-on: https://go-review.googlesource.com/19967Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The old implementation assumed that all memory runs
were terminated by non-memory fields.
This isn't necessarily so.
They might be terminated by padding or blank fields.

For example, given

type T struct {
	a int64
	b byte
	c, d, e int64
}

the old implementation did a memory comparison on a+b, on c, and on d+e.

Instead, check for memory runs at the beginning of every round.
This now generates a memory comparison on a+b and on c+d+e.

Also, delete some now-dead code.

Change-Id: I66bffb111420adf6919bd708e4fb3a1e1f07fadd
Reviewed-on: https://go-review.googlesource.com/19841Reviewed-by: David Crawshaw <crawshaw@golang.org>

Passes toolstash -cmp.

Change-Id: Ifae69e5ba673f01da3dfc1fd30cdc51873481623
Reviewed-on: https://go-review.googlesource.com/19840Reviewed-by: David Crawshaw <crawshaw@golang.org>

By using a Pragma bit set (8 bits) rather than 8 booleans, also
reduce Func type size by 8 bytes (208B -> 200B on 64bit platforms,
116B -> 108B on 32bit platforms).

Change-Id: Ibb7e1f8c418a0b5bc6ff813cbdde7bc6f0013b5a
Reviewed-on: https://go-review.googlesource.com/19966Reviewed-by: Dave Cheney <dave@cheney.net>

Instead add a dedicated keywords map for use in lexer.ident and drop
Sym's Lexical field.

Change-Id: Ia668e65499035ff7167fabbbd0cd027102b21231
Reviewed-on: https://go-review.googlesource.com/19935Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

If a general comment contains multiple newline characters, we can't
simply unread one and then re-lex it via the general whitespace lexing
phase, because then we'll reset lineno to the line before the "*/"
marker, rather than keeping it where we found the "/*" marker.

Also, for processing imports, call importfile before advancing the
lexer with p.next(), so that lineno reflects the line where we found
the import path, and not the token afterwards.

Fixes #14520.

Change-Id: I785a2d83d632280113d4b757de0d57c88ba2caf4
Reviewed-on: https://go-review.googlesource.com/19934Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

The new TestDashS was leaving a dreg "test" file in
cmd/compile/internal/gc.  Create it in the temporary directory instead.

Also change path.Join to filepath.Join throughout global_test.go.

Change-Id: Ib7707fada2b3ab5e8abc2ba74e4c402821c1408b
Reviewed-on: https://go-review.googlesource.com/19965
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

A slice uses less memory than a NodeList, and has better memory locality
when walking the list.

This uncovered a tricky case involving closures: the escape analysis
pass when run on a closure was appending to the Dcl list of the OCLOSURE
rather than the ODCLFUNC.  This happened to work because they shared the
same NodeList.  Fixed with a change to addrescapes, and a check to
Tempname to catch any recurrences.

This removes the last use of the listsort function outside of tests.
I'll send a separate CL to remove it.

Unfortunately, while this passes all tests, it does not pass toolstash
-cmp.  The problem is that cmpstackvarlt does not fully determine the
sort order, and the change from listsort to sort.Sort, while generally
desirable, produces a different ordering.  I could stage this by first
making cmpstackvarlt fully determined, but no matter what toolstash -cmp
is going to break at some point.

In my casual testing the compiler is 2.2% faster.

Update #14473.

Change-Id: I367d66daa4ec73ed95c14c66ccda3a2133ad95d5
Reviewed-on: https://go-review.googlesource.com/19919Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The Go toolchain stopped creating them before Go 1.3, so no point in
worrying about them today.

History:

- Git commit 250a0919 added cmd/ar, which wrote Plan 9 __.SYMDEF
entries into archive files.

- golang.org/cl/6500117 renamed __.SYMDEF to __.GOSYMDEF.  (Notably,
the commit message suggests users need to use Go nm to read symbols,
but even back then the toolchain did nothing with __.(GO)?SYMDEF files
except skip over them.)

- golang.org/cl/42880043 added the -pack flag to cmd/gc to directly
produce archives by the Go compiler, and did not write __.GOSYMDEF
entries.

- golang.org/cl/52310044 rewrote cmd/pack in Go, and removed support
for producing __.GOSYMDEF entries.

Change-Id: I255edf40d0d3690e3447e488039fcdef73c6d6b1
Reviewed-on: https://go-review.googlesource.com/19924
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Atomic load/store/add/swap routines, as for other ARM platforms, but with DMB inserted
for load/store (assuming that "atomic" also implies acquire/release memory ordering).

Change-Id: I70a283d8f0ae61a66432998ce59eac76fd940c67
Reviewed-on: https://go-review.googlesource.com/18965Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Change-Id: Ie915dc2fc32a31d31f566ac931ccecb506559645
Reviewed-on: https://go-review.googlesource.com/19888Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

This change adds support in testing/quick to generate maps and slices
in additional states:

  (1.) nil maps

  (2.) nil slices

  (3.) empty slice occupancy: `len(s) == 0 && s != nil`

  (4.) partial slice occupancy: `len(s) < cap(s) && s != nil`

  (5.) full slice occupancy: `len(s) == cap(s) && s != nil`

Prior to this, only #5 was ever generated, thereby not sufficiently
exercising all of the fuzzable code path outcomes.

This change depends on https://go-review.googlesource.com/#/c/17499/.

Change-Id: I9343c475cefbd72ffc5237281826465c25872206
Reviewed-on: https://go-review.googlesource.com/16470Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Implementation closely follows plan9_386 version.

Change-Id: Ifb76e001fb5664e6a23541cf4768d7f11b2be68b
Reviewed-on: https://go-review.googlesource.com/18967Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Go already supports Linux's getrandom, which is a slightly modified
version of getentropy.

getentropy was added in OpenBSD 5.6. All supported versions of OpenBSD
include it so, unlike with Linux and getrandom, we don't need to test
for its presence.

Fixes #13785.

Change-Id: Ib536b96675f257cd8c5de1e3a36165e15c9abac9
Reviewed-on: https://go-review.googlesource.com/18219
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>