MOV with SSE registers seems faster than REP MOVSQ if the
size being copied is less than about 2K. Previously we
didn't use MOV if the memory region is larger than 256
byte. This patch improves the performance of 257 ~ 2048
byte non-overlapping copy by using MOV.

Here is the benchmark result on Intel Xeon 3.5GHz (Nehalem).

benchmark               old ns/op    new ns/op    delta
BenchmarkMemmove16              4            4   +0.42%
BenchmarkMemmove32              5            5   -0.20%
BenchmarkMemmove64              6            6   -0.81%
BenchmarkMemmove128             7            7   -0.82%
BenchmarkMemmove256            10           10   +1.92%
BenchmarkMemmove512            29           16  -44.90%
BenchmarkMemmove1024           37           25  -31.55%
BenchmarkMemmove2048           55           44  -19.46%
BenchmarkMemmove4096           92           91   -0.76%

benchmark                old MB/s     new MB/s  speedup
BenchmarkMemmove16        3370.61      3356.88    1.00x
BenchmarkMemmove32        6368.68      6386.99    1.00x
BenchmarkMemmove64       10367.37     10462.62    1.01x
BenchmarkMemmove128      17551.16     17713.48    1.01x
BenchmarkMemmove256      24692.81     24142.99    0.98x
BenchmarkMemmove512      17428.70     31687.72    1.82x
BenchmarkMemmove1024     27401.82     40009.45    1.46x
BenchmarkMemmove2048     36884.86     45766.98    1.24x
BenchmarkMemmove4096     44295.91     44627.86    1.01x

LGTM=khr
R=golang-codereviews, gobot, khr
CC=golang-codereviews
https://golang.org/cl/90500043

Also exposes common socket option functions on Solaris.

Update #7174
Update #7175

LGTM=aram
R=golang-codereviews, aram
CC=golang-codereviews
https://golang.org/cl/107280044

LGTM=dave
R=golang-codereviews, dave
CC=golang-codereviews
https://golang.org/cl/110020050

paeth(0, x, 0) == x for any uint8 value.

LGTM=nigeltao
R=golang-codereviews, bradfitz, nigeltao
CC=golang-codereviews
https://golang.org/cl/105290049

sync.Pool is not supposed to be used everywhere, but is
a last resort.

««« original CL description
strings: use sync.Pool to cache buffer

benchmark                         old ns/op    new ns/op    delta
BenchmarkByteReplacerWriteString       3596         3094  -13.96%

benchmark                        old allocs   new allocs    delta
BenchmarkByteReplacerWriteString          1            0  -100.00%

LGTM=dvyukov
R=bradfitz, dave, dvyukov
CC=golang-codereviews
https://golang.org/cl/101330053
»»»

LGTM=dave
R=r, dave
CC=golang-codereviews
https://golang.org/cl/102610043

Fixes #8074.

The issue was not reproduceable by revision

go version devel +e0ad7e329637 Thu Jun 19 22:19:56 2014 -0700 linux/arm

But include the original test case in case the issue reopens itself.

LGTM=dvyukov
R=golang-codereviews, dvyukov
CC=golang-codereviews
https://golang.org/cl/107290043

benchmark                         old ns/op    new ns/op    delta
BenchmarkByteReplacerWriteString       3596         3094  -13.96%

benchmark                        old allocs   new allocs    delta
BenchmarkByteReplacerWriteString          1            0  -100.00%

LGTM=dvyukov
R=bradfitz, dave, dvyukov
CC=golang-codereviews
https://golang.org/cl/101330053

R=golang-codereviews
CC=golang-codereviews
https://golang.org/cl/103520044

LGTM=ruiu
R=golang-codereviews, ruiu
CC=golang-codereviews
https://golang.org/cl/109100046

LGTM=dave
R=golang-codereviews, dave
CC=golang-codereviews
https://golang.org/cl/102580043

All tests pass except one test in regexp package.

LGTM=iant
R=golang-codereviews, iant, dave
CC=golang-codereviews
https://golang.org/cl/107270043

It was built on an old, bogus revision.

LGTM=minux
TBR=iant
R=iant, minux
CC=golang-codereviews
https://golang.org/cl/101370052

This requires minimal changes to the runtime hooks. In particular,
synchronization events must be done only on valid addresses now,
so I've added the additional checks to race.c.

LGTM=iant
R=iant
CC=golang-codereviews
https://golang.org/cl/101000046

benchmark                         old ns/op    new ns/op    delta
BenchmarkByteReplacerWriteString       7359         3661  -50.25%

LGTM=dave
R=golang-codereviews, dave
CC=golang-codereviews
https://golang.org/cl/102550043

Fixes #7858.

LGTM=ruiu
R=ruiu
CC=golang-codereviews
https://golang.org/cl/92720045

Single-case select with a non-nil channel is pointless.

LGTM=mikioh.mikioh
R=mikioh.mikioh
CC=golang-codereviews
https://golang.org/cl/103920044

Afterprologue check was required when did not know
about return arguments of functions and/or they were not zeroed.
Now 100% precision is required for stacks due to stack copying,
so it must work w/o afterprologue one way or another.
I can limit this change for 1.3 to merely adding a TODO,
but this check is super confusing so I don't want this knowledge to get lost.

LGTM=rsc
R=golang-codereviews, gobot, rsc, khr
CC=golang-codereviews, khr, rsc
https://golang.org/cl/96580045

LGTM=dave
R=golang-codereviews, bradfitz, dave
CC=golang-codereviews
https://golang.org/cl/109090048

Avoid unnecessary bitwise-OR operations.

benchmark                      old MB/s     new MB/s  speedup
BenchmarkEncodeToStringBase64  179.02       205.74    1.15x
BenchmarkEncodeToStringBase32  155.86       167.82    1.08x

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/109090043

Use WriteString instead of allocating a byte slice as a
buffer. This was a TODO.

benchmark               old ns/op    new ns/op    delta
BenchmarkWriteString        40139        19991  -50.20%

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/107190044

Fixes #8201.

LGTM=nigeltao
R=nigeltao
CC=golang-codereviews
https://golang.org/cl/105990046

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/102830043

requires a decoder to do its own byte buffering instead of using
bufio.Reader, due to byte stuffing.

benchmark                      old MB/s     new MB/s     speedup
BenchmarkDecodeBaseline        33.40        50.65        1.52x
BenchmarkDecodeProgressive     24.34        31.92        1.31x

On 6g, unsafe.Sizeof(huffman{}) falls from 4872 to 964 bytes, and
the decoder struct contains 8 of those.

LGTM=r
R=r, nightlyone
CC=bradfitz, couchmoney, golang-codereviews, raph
https://golang.org/cl/109050045

LGTM=minux
R=golang-codereviews, minux
CC=golang-codereviews
https://golang.org/cl/107200043

This is a clone of 101370043, which I accidentally applied to the
release branch first.
No big deal, it needed to be applied there anyway.

LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/108090043

Fixes #7694.

LGTM=nigeltao, rsc, r
R=golang-codereviews, nigeltao, rsc, r
CC=golang-codereviews
https://golang.org/cl/109000049

Storing temporary values to a slice is slower than storing
them to local variables of type byte.

benchmark                         old MB/s     new MB/s  speedup
BenchmarkEncodeToStringBase32       102.21       156.66    1.53x
BenchmarkEncodeToStringBase64       124.25       177.91    1.43x

LGTM=crawshaw
R=golang-codereviews, crawshaw, bradfitz, dave
CC=golang-codereviews
https://golang.org/cl/109820045

Fixes #8175.

LGTM=r
R=golang-codereviews, r, gobot
CC=golang-codereviews
https://golang.org/cl/103320043

Just to be more thorough.
No need to push this to 1.3; it's just a test change that
worked without any changes to the code being tested.

LGTM=crawshaw
R=golang-codereviews, crawshaw
CC=golang-codereviews
https://golang.org/cl/109080045

LGTM=bradfitz
R=adg, rsc, bradfitz
CC=golang-codereviews
https://golang.org/cl/102470045

genericReplacer.lookup is called for each byte of an input
string. In many (most?) cases, lookup will fail for the first
byte, and it will return immediately. Adding a fast path for
that case seems worth it.

Benchmark on my Xeon 3.5GHz Linux box:

benchmark                        old ns/op    new ns/op    delta
BenchmarkGenericNoMatch               2691          774  -71.24%
BenchmarkGenericMatch1                7920         8151   +2.92%
BenchmarkGenericMatch2               52336        39927  -23.71%
BenchmarkSingleMaxSkipping            1575         1575   +0.00%
BenchmarkSingleLongSuffixFail         1429         1429   +0.00%
BenchmarkSingleMatch                 56228        55444   -1.39%
BenchmarkByteByteNoMatch               568          568   +0.00%
BenchmarkByteByteMatch                 977          972   -0.51%
BenchmarkByteStringMatch              1669         1687   +1.08%
BenchmarkHTMLEscapeNew                 422          422   +0.00%
BenchmarkHTMLEscapeOld                 692          670   -3.18%
BenchmarkByteByteReplaces             8492         8474   -0.21%
BenchmarkByteByteMap                  2817         2808   -0.32%

LGTM=rsc
R=golang-codereviews, bradfitz, dave, rsc
CC=golang-codereviews
https://golang.org/cl/79200044

Make assembly govet-clean.
Clean up fixes for CL 93380044.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/107160047

Bug was introduced recently. Add more tests, fix the bugs.
Suppress + sign when not required in zero padding.
Do not zero pad infinities.
All old tests still pass.
This time for sure!
Fixes #8217.

LGTM=rsc
R=golang-codereviews, dan.kortschak, rsc
CC=golang-codereviews
https://golang.org/cl/103480043

LGTM=adonovan
R=adonovan, ruiu
CC=golang-codereviews
https://golang.org/cl/107160048

Using flet to replace kill-region with delete-region was a hack,
flet is now (GNU Emacs 24.3) deprecated and at least two people
have reported an issue where using go--delete-whole-line would
permanently break their kill ring. While that issue is probably
caused by faulty third party code (possibly prelude), it's easier
to write a clean implementation than to tweak the hack.

LGTM=ruiu, adonovan
R=adonovan, ruiu
CC=adg, golang-codereviews
https://golang.org/cl/106010043

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/105300044

Null terminate string.  Make it endian-agnostic.

TBR=bradfitz
R=golang-codereviews
CC=golang-codereviews
https://golang.org/cl/106060044

No functional changes.

Generating shorter functions improves compilation time. On my laptop, this test's running time goes from 5.5s to 1.5s; the wall clock time to run all tests goes down 1s. On Raspberry Pi, this CL cuts 50s off the wall clock time to run all tests.

Fixes #7503.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/72590045

Fixes #8207.

LGTM=gordon.klaus, bradfitz
R=golang-codereviews, wandakkelly, gordon.klaus, bradfitz
CC=golang-codereviews
https://golang.org/cl/106010046

The go:nosplit change wasn't the problem, reinstating.

««« original CL description
undo CL 93380044 / 7f0999348917

Partial undo, just of go:nosplit annotation.  Somehow it
is breaking the windows builders.

TBR=bradfitz

««« original CL description
runtime: implement string ops in Go

Also implement go:nosplit annotation.  Not really needed
for now, but we'll definitely need it for other conversions.

benchmark                 old ns/op     new ns/op     delta
BenchmarkRuneIterate      534           474           -11.24%
BenchmarkRuneIterate2     535           470           -12.15%

LGTM=bradfitz
R=golang-codereviews, dave, bradfitz, minux
CC=golang-codereviews
https://golang.org/cl/93380044
»»»

TBR=bradfitz
CC=golang-codereviews
https://golang.org/cl/105260044
»»»

TBR=bradfitz
R=bradfitz, golang-codereviews
CC=golang-codereviews
https://golang.org/cl/103490043