pkg/syscall: Plan 9, 64-bit: Update error checks from sys calls.

This change updates CL 6576057 for exceptional cases where
return values from Syscall/RawSyscall functions are used.

The system calls return 32-bit integers. With the recent change
in size of `int' in Go for amd64, the type conversion was not
catching `-1' return values. This change makes the conversion
explicitly `int32'.

R=rsc, r
CC=golang-dev
http://codereview.appspot.com/6590047

Committer: Rob Pike <r@golang.org>
cmd/gc: Missing break in esc switch.

R=rsc
CC=golang-dev
http://codereview.appspot.com/6594053
cmd/go/build: Add magic data for Plan 9 binaries.

This change allows the Go build and install tools to
recognize Plan 9 i386 and amd64 binaries.

R=rsc, r, rminnich
CC=golang-dev
http://codereview.appspot.com/6575064

Committer: Russ Cox <rsc@golang.org>
A+C: add Jeff Wendling (Individual CLA)

R=golang-dev, iant
CC=golang-dev
http://codereview.appspot.com/6596050
cmd/godoc: clearer comments in FormatSelections

R=golang-dev, rsc
CC=golang-dev
http://codereview.appspot.com/6561073
math/big: avoid some allocation in Exp

benchmark                        old ns/op    new ns/op    delta
BenchmarkRSA1024Decrypt             745686       644964  -13.51%
BenchmarkRSA2048Decrypt            5517318      5049200   -8.48%
Benchmark3PrimeRSA2048Decrypt      3767386      3288048  -12.72%

R=gri
CC=gobot, golang-dev
http://codereview.appspot.com/6566043
archive/tar: fix inconsistent namespace usage in example

This fixes some example code in the tar package documentation, which
first refers to tar.NewWriter and then to Header, which is inconsistent
because NewWriter and Header are both in the tar namespace.

R=golang-dev, dsymonds
CC=golang-dev
http://codereview.appspot.com/6595050

Committer: David Symonds <dsymonds@golang.org>
cmd/5g: avoid temporary during constant binary op

This CL is an attempt to backport the abop code generation from 6g. This improves the generation of the range offset if the increment can be encoded directly via Operand2 shift encoding.

0023 (/home/dfc/src/range.go:7) BGE     ,29(APC)
0024 (/home/dfc/src/range.go:7) MOVW    0(R3),R5
0025 (/home/dfc/src/range.go:7) MOVW    $4,R1
0026 (/home/dfc/src/range.go:7) ADD     R1,R3,R3
0027 (/home/dfc/src/range.go:8) ADD     R5,R4,R4
0028 (/home/dfc/src/range.go:7) B       ,17(APC)

becomes

0023 (/home/dfc/src/range.go:7) BGE     ,28(APC)
0024 (/home/dfc/src/range.go:7) MOVW    0(R3),R0
0025 (/home/dfc/src/range.go:7) ADD     $4,R3,R3
0026 (/home/dfc/src/range.go:8) ADD     R0,R4,R4
0027 (/home/dfc/src/range.go:7) B       ,17(APC)

Benchmarks are unimpressive

dfc@qnap:~/go/test/bench/go1$ ~/go/misc/benchcmp {old,new}.txt
benchmark                 old ns/op    new ns/op    delta
BenchmarkBinaryTree17    2147483647   2147483647   +0.93%
BenchmarkFannkuch11      2147483647   2147483647   -2.52%
BenchmarkGobDecode        196135200    195842000   -0.15%
BenchmarkGobEncode         78581650     76734450   -2.35%
BenchmarkGzip            2147483647   2147483647   -0.47%
BenchmarkGunzip          1087243000   1070254000   -1.56%
BenchmarkJSONEncode      1107558000   1146077000   +3.48%
BenchmarkJSONDecode      2147483647   2147483647   -0.07%
BenchmarkMandelbrot200   2147483647   2147483647   -0.77%
BenchmarkParse             74328550     71653400   -3.60%
BenchmarkRevcomp          111123900    109325950   -1.62%
BenchmarkTemplate        2147483647   2147483647   -0.82%

benchmark                  old MB/s     new MB/s  speedup
BenchmarkGobDecode             3.91         3.92    1.00x
BenchmarkGobEncode             9.77        10.00    1.02x
BenchmarkGzip                  3.65         3.66    1.00x
BenchmarkGunzip               17.85        18.13    1.02x
BenchmarkJSONEncode            1.75         1.69    0.97x
BenchmarkJSONDecode            0.83         0.83    1.00x
BenchmarkParse                 0.78         0.81    1.04x
BenchmarkRevcomp              22.87        23.25    1.02x
BenchmarkTemplate              0.84         0.85    1.01x

R=remyoudompheng, minux.ma, rsc
CC=golang-dev
http://codereview.appspot.com/6564067
go/doc: strip example output comment from synthesized main function

R=gri
CC=gobot, golang-dev
http://codereview.appspot.com/6524047
race: gc changes
This is the first part of a bigger change that adds data race detection feature:
http://codereview.appspot.com/6456044
This change makes gc compiler instrument memory accesses when supplied with -b flag.

R=rsc, nigeltao, lvd
CC=golang-dev
http://codereview.appspot.com/6497074
cmd/8g: do not take the address of string/slice for &s[i]

A similar change was made in 6g recently.

LEALs in cmd/go: 31440 before, 27867 after.

benchmark                 old ns/op    new ns/op    delta
BenchmarkBinaryTree17    7065794000   6723617000   -4.84%
BenchmarkFannkuch11      7767395000   7477945000   -3.73%
BenchmarkGobDecode         34708140     34857820   +0.43%
BenchmarkGobEncode         10998780     10960060   -0.35%
BenchmarkGzip            1603630000   1471052000   -8.27%
BenchmarkGunzip           242573900    240650400   -0.79%
BenchmarkJSONEncode       120842200    117966100   -2.38%
BenchmarkJSONDecode       247254900    249103100   +0.75%
BenchmarkMandelbrot200     29237330     29241790   +0.02%
BenchmarkParse              8111320      8096865   -0.18%
BenchmarkRevcomp         2595780000   2694153000   +3.79%
BenchmarkTemplate         276679600    264497000   -4.40%

benchmark                              old ns/op    new ns/op    delta
BenchmarkAppendFloatDecimal                  429          416   -3.03%
BenchmarkAppendFloat                         780          740   -5.13%
BenchmarkAppendFloatExp                      746          700   -6.17%
BenchmarkAppendFloatNegExp                   752          694   -7.71%
BenchmarkAppendFloatBig                     1228         1108   -9.77%
BenchmarkAppendFloat32Integer                457          416   -8.97%
BenchmarkAppendFloat32ExactFraction          662          631   -4.68%
BenchmarkAppendFloat32Point                  771          735   -4.67%
BenchmarkAppendFloat32Exp                    722          672   -6.93%
BenchmarkAppendFloat32NegExp                 724          659   -8.98%
BenchmarkAppendFloat64Fixed1                 429          400   -6.76%
BenchmarkAppendFloat64Fixed2                 463          442   -4.54%

Update issue 1914.

R=golang-dev, daniel.morsing, rsc
CC=golang-dev
http://codereview.appspot.com/6574043
codereview.py: suggest installing Mercurial from official website

Continuation of http://codereview.appspot.com/6499053/

R=golang-dev, minux.ma
CC=golang-dev
http://codereview.appspot.com/6584059

Committer: Rob Pike <r@golang.org>
go/parser: correctly parse <-chan T(x) as <-(chan T)(x)

Fixes issue 4110.

R=iant
CC=golang-dev
http://codereview.appspot.com/6597069
os/user : use username as fullname if all else fails (on windows)

Fixes issue 4113.

R=golang-dev, alex.brainman
CC=golang-dev
http://codereview.appspot.com/6545054

Committer: Alex Brainman <alex.brainman@gmail.com>
go/ast: track position of <- for channel types

This is a backward-compatible API change.

Without the correct <- position information,
certain channel types have incorrect position
information.

R=iant, iant
CC=golang-dev
http://codereview.appspot.com/6585063
text/template: better error messages during execution,
They now show the correct name, the byte offset on the line, and context for the failed evaluation.
Before:
        template: three:7: error calling index: index out of range: 5
After:
        template: top:7:20: executing "three" at <index "hi" $>: error calling index: index out of range: 5
Here top is the template that was parsed to create the set, and the error appears with the action
starting at byte 20 of line 7 of "top", inside the template called "three", evaluating the expression
<index "hi" $>.

Also fix a bug in index: it didn't work on strings. Ouch.

Also fix bug in error for index: was showing type of index not slice.
The real previous error was:
        template: three:7: error calling index: can't index item of type int
The html/template package's errors can be improved by building on this;
I'll do that in a separate pass.

Extends the API for text/template/parse but only by addition of a field and method. The
old API still works.

Fixes issue 3188.

R=golang-dev, dsymonds
CC=golang-dev
http://codereview.appspot.com/6576058