The check for Stringer etc. can only fire if the test is not a builtin, so avoid
the expensive check if we know there's no chance.
Also put in a fast path for pad, which saves a more modest amount.

benchmark                      old ns/op    new ns/op    delta
BenchmarkSprintfEmpty                148          152   +2.70%
BenchmarkSprintfString               585          497  -15.04%
BenchmarkSprintfInt                  441          396  -10.20%
BenchmarkSprintfIntInt               718          603  -16.02%
BenchmarkSprintfPrefixedInt          676          621   -8.14%
BenchmarkSprintfFloat               1003          953   -4.99%
BenchmarkManyArgs                   2945         2312  -21.49%
BenchmarkScanInts                1704152      1734441   +1.78%
BenchmarkScanRecursiveInt        1837397      1828920   -0.46%

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6245068

Also convert table to use tagged literal.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6258061

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6249065

Two fixes for indentation problems:

1. Properly recognize multi-line strings. These start with `, not ".

2. Don't indent a line if the beginning of the line is the end of a multi-line string. This happened for instance when inserting a closing bracket after a multi-line string.

R=sameer
CC=golang-dev
https://golang.org/cl/6157044

Fixes #3682.

R=rsc
CC=golang-dev
https://golang.org/cl/6256067

This prevents clients from seeing RSTs and missing the response
body.

TCP stacks vary. The included test failed on Darwin before but
passed on Linux.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6256066

See time/sleep_test.go for repro.

R=golang-dev, r, rsc
CC=golang-dev, patrick.allen.higgins
https://golang.org/cl/6250072

It was only being used for (*Stmt).Exec, not Query, and not for
the same two methods on *DB.

This unifies (*Stmt).Exec's old inline code into the old
subsetArgs function, renaming it in the process (changing the
old word "subset" to "driver", mostly converted earlier)

Fixes #3640

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6258045

It's sad to introduce a new macro, but rnd shows up consistently
in profiles, and the function call overwhelms the two arithmetic
instructions it performs.

R=r
CC=golang-dev
https://golang.org/cl/6260051

Moving panic out of line speeds up fannkuch almost a factor of two.
Changes to bitwhacking code affect mandelbrot badly.

R=golang-dev, bradfitz, rsc, r
CC=golang-dev
https://golang.org/cl/6258056

It's broken and seems to be exp/types's fault.

Update #3682.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6243068

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6254055

R=rsc
CC=golang-dev
https://golang.org/cl/6242067

Rename _Block to block, don't bother making it compute count.
Add benchmarks.

R=agl, agl
CC=golang-dev
https://golang.org/cl/6243053

breaks public API document style

««« original CL description
net: fix comment on FileListener

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6248054
»»»

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6242066

Fixes #3509.
Fixes #2767.

R=golang-dev, sameer
CC=golang-dev
https://golang.org/cl/6139066

Plan 9 versions for amd64 have 2 megabyte pages.
This also fixes the logic for 32-bit vs 64-bit Plan 9,
making 64-bit the default, and adds logic to generate
a symbols table.

R=golang-dev, rsc, rminnich, ality, 0intro
CC=golang-dev, john
https://golang.org/cl/6218046

The old code generated for a bounds check was
                CMP
                JLT ok
                CALL panicindex
        ok:
                ...

The new code is (once the linker finishes with it):
                CMP
                JGE panic
                ...
        panic:
                CALL panicindex

which moves the calls out of line, putting more useful
code in each cache line.  This matters especially in tight
loops, such as in Fannkuch.  The benefit is more modest
elsewhere, but real.

From test/bench/go1, amd64:

benchmark                old ns/op    new ns/op    delta
BenchmarkBinaryTree17   6096092000   6088808000   -0.12%
BenchmarkFannkuch11     6151404000   4020463000  -34.64%
BenchmarkGobDecode        28990050     28894630   -0.33%
BenchmarkGobEncode        12406310     12136730   -2.17%
BenchmarkGzip               179923       179903   -0.01%
BenchmarkGunzip              11219        11130   -0.79%
BenchmarkJSONEncode       86429350     86515900   +0.10%
BenchmarkJSONDecode      334593800    315728400   -5.64%
BenchmarkRevcomp25M     1219763000   1180767000   -3.20%
BenchmarkTemplate        492947600    483646800   -1.89%

And 386:

benchmark                old ns/op    new ns/op    delta
BenchmarkBinaryTree17   6354902000   6243000000   -1.76%
BenchmarkFannkuch11     8043769000   7326965000   -8.91%
BenchmarkGobDecode        19010800     18941230   -0.37%
BenchmarkGobEncode        14077500     13792460   -2.02%
BenchmarkGzip               194087       193619   -0.24%
BenchmarkGunzip              12495        12457   -0.30%
BenchmarkJSONEncode      125636400    125451400   -0.15%
BenchmarkJSONDecode      696648600    685032800   -1.67%
BenchmarkRevcomp25M     2058088000   2052545000   -0.27%
BenchmarkTemplate        602140000    589876800   -2.04%

To implement this, two new instruction forms:

        JLT target      // same as always
        JLT $0, target  // branch expected not taken
        JLT $1, target  // branch expected taken

The linker could also emit the prediction prefixes, but it
does not: expected taken branches are reversed so that the
expected case is not taken (as in example above), and
the default expectaton for such a jump is not taken
already.

R=golang-dev, gri, r, dave
CC=golang-dev
https://golang.org/cl/6248049

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6260049

Implement the (3-per-family) Noah's Ark clause (i.e. don't put
more than three identical elements on the list of active formatting
elements.

Also, when running tests, sort attributes by name before dumping
them.

Pass 4 additional tests with Noah's Ark clause (including one
that needs attributes to be sorted).

Pass 5 additional, unrelated tests because of sorting attributes.

R=nigeltao, rsc
CC=golang-dev
https://golang.org/cl/6247056

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6248054

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6256059

R=golang-dev, dsymonds, r
CC=golang-dev
https://golang.org/cl/6242062

CanonicalHeaderKey didn't allocate, but it did use unnecessary
CPU in the hot path, deciding it didn't need to allocate.

I considered using constants for all these common header keys
but I didn't think it would be prettier. "Content-Length" looks
better than contentLength or hdrContentLength, etc.

R=golang-dev, dave
CC=golang-dev
https://golang.org/cl/6255053

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6248053

Fixes #3535

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/6245060

Comment on cache keys above connectMethod says "http to proxy, http
anywhere after that", however in reality target address was always
included, which prevented http requests to different target
addresses to reuse the same http proxy connection.

R=golang-dev, r, rsc, bradfitz
CC=golang-dev
https://golang.org/cl/5901064

Fixes #3623.

R=golang-dev, bsiegert, rsc
CC=golang-dev
https://golang.org/cl/6218072

CL 5956051 introduced too many call != nil checks, so
attempt to improve this by splitting logic into three
distinct parts.

R=r
CC=golang-dev
https://golang.org/cl/6248048

image/png benchmarks:
benchmark                       old ns/op    new ns/op    delta
BenchmarkPaeth                         10            7  -29.21%
BenchmarkDecodeGray               2381745      2241620   -5.88%
BenchmarkDecodeNRGBAGradient      9535555      8835100   -7.35%
BenchmarkDecodeNRGBAOpaque        8189590      7611865   -7.05%
BenchmarkDecodePaletted           1300688      1301940   +0.10%
BenchmarkDecodeRGB                6760146      6317082   -6.55%
BenchmarkEncodePaletted           6048596      6122666   +1.22%
BenchmarkEncodeRGBOpaque         18891140     19474230   +3.09%
BenchmarkEncodeRGBA              78945350     78552600   -0.50%

Wall time for Denis Cheremisov's PNG-decoding program given in
https://groups.google.com/group/golang-nuts/browse_thread/thread/22aa8a05040fdd49
Before: 2.25s
After:  2.27s
Delta:  +1%

The same program, but with a different PNG input file
(http://upload.wikimedia.org/wikipedia/commons/4/47/PNG_transparency_demonstration_1.png)
and only 100 iterations instead of 1000
Before: 4.78s
After:  4.42s
Delta:  -8%

R=rsc
CC=golang-dev
https://golang.org/cl/6242056

Ken pointed out that CL 5998043 was ugly code.
This should be better.

Fixes #3501.

R=ken2
CC=golang-dev
https://golang.org/cl/6258049

for expr1, expr2 = range slice
was assigning to expr1 and expr2 in sequence
instead of in parallel.  Now it assigns in parallel,
as it should.  This matters for things like
for i, x[i] = range slice.

Fixes #3464.

R=ken2
CC=golang-dev
https://golang.org/cl/6252048

This is from CL 5451105 but was dropped from that CL.
See also CL 6137051.

The only change compared to 5451105 is to check for
h != nil in reflect·mapiterinit; allowing use of nil maps
must have happened after that original CL.

Fixes #3573.

R=golang-dev, dave, r
CC=golang-dev
https://golang.org/cl/6215078

Fixes #3299

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6250056

Remove redundant checks for integration points.

Ignore null bytes in text.

Don't break out of foreign content for a <font> tag unless it
has a color, face, or size attribute.

Check for MathML text integration points when breaking out of
foreign content.

Pass two new tests.

R=nigeltao
CC=golang-dev
https://golang.org/cl/6256045

The bulk of the gains come from hoisting the modulo ops outside of
the inner loop.

Reducing the digest type from 8 bytes to 4 bytes gains another 1% on
the hash/adler32 micro-benchmark.

Benchmarks for $GOOS,$GOARCH = linux,amd64 below.

hash/adler32 benchmark:
benchmark             old ns/op    new ns/op    delta
BenchmarkAdler32KB         1660         1364  -17.83%

image/png benchmark:
benchmark                       old ns/op    new ns/op    delta
BenchmarkDecodeGray               2466909      2425539   -1.68%
BenchmarkDecodeNRGBAGradient      9884500      9751705   -1.34%
BenchmarkDecodeNRGBAOpaque        8511615      8379800   -1.55%
BenchmarkDecodePaletted           1366683      1330677   -2.63%
BenchmarkDecodeRGB                6987496      6884974   -1.47%
BenchmarkEncodePaletted           6292408      6040052   -4.01%
BenchmarkEncodeRGBOpaque         19780680     19178440   -3.04%
BenchmarkEncodeRGBA              80738600     79076800   -2.06%

Wall time for Denis Cheremisov's PNG-decoding program given in
https://groups.google.com/group/golang-nuts/browse_thread/thread/22aa8a05040fdd49
Before: 2.44s
After:  2.26s
Delta:  -7%

R=rsc
CC=golang-dev
https://golang.org/cl/6251044

Fixes #3580.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6252047

Fixes #3639.

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/6243045

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6257050