Fixes #4678.

TBR=gri
CC=golang-dev
https://golang.org/cl/7135059

For simplicity, only recognizes expressions of the exact form
"(x << a) | (x >> b)" where x is a variable and a and b are
integer constant expressions that add to x's bit width.

Fixes #4629.

$ cat rotate.c
unsigned int
rotate(unsigned int x)
{
        x = (x << 3) | (x >> (sizeof(x) * 8 - 3));
        return x;
}

## BEFORE
$ go tool 6c -S rotate.c
(rotate.c:2)	TEXT	rotate+0(SB),$0-8
(rotate.c:2)	MOVL	x+0(FP),!!DX
(rotate.c:4)	MOVL	DX,!!AX
(rotate.c:4)	SALL	$3,!!AX
(rotate.c:4)	MOVL	DX,!!CX
(rotate.c:4)	SHRL	$29,!!CX
(rotate.c:4)	ORL	CX,!!AX
(rotate.c:5)	RET	,!!
(rotate.c:5)	RET	,!!
(rotate.c:5)	END	,!!

## AFTER
$ go tool 6c -S rotate.c
(rotate.c:2)	TEXT	rotate+0(SB),$0-8
(rotate.c:4)	MOVL	x+0(FP),!!AX
(rotate.c:4)	ROLL	$3,!!AX
(rotate.c:5)	RET	,!!
(rotate.c:5)	RET	,!!
(rotate.c:5)	END	,!!

R=rsc, minux.ma
CC=golang-dev
https://golang.org/cl/7069056

Fixes #3719.

R=anacrolix, rsc
CC=golang-dev
https://golang.org/cl/7131052

Fixes #4653.

R=rsc, r, iant, ken, thakis
CC=golang-dev
https://golang.org/cl/7135058

If the scanned block has no typeinfo the garbage collector will attempt
to get the actual type of the block.

R=golang-dev, bradfitz, rsc
CC=golang-dev
https://golang.org/cl/7093045

The test array is too large to fit a stack frame
but can be a global.

R=golang-dev, minux.ma
CC=golang-dev
https://golang.org/cl/7127059

Fixes #4610.

R=golang-dev, remyoudompheng, rsc
CC=golang-dev, nigeltao
https://golang.org/cl/7058057

On Plan 9, only the parent of a given process can enter its wait
queue. When a Go program tries to fork-exec a child process
and subsequently waits for it to finish, the goroutines doing
these two tasks do not necessarily tie themselves to the same
(or any single) OS thread. In the case that the fork and the wait
system calls happen on different OS threads (say, due to a
goroutine being rescheduled somewhere along the way), the
wait() will either return an error or end up waiting for a
completely different child than was intended.

This change forces the fork and wait syscalls to happen in the
same goroutine and ties that goroutine to its OS thread until
the child exits. The PID of the child is recorded upon fork and
exit, and de-queued once the child's wait message has been read.
The Wait API, then, is translated into a synthetic implementation
that simply waits for the requested PID to show up in the queue
and then reads the associated stats.

R=rsc, rminnich, npe, mirtchovski, ality
CC=golang-dev
https://golang.org/cl/6545051

The test case of issue 4585 was not passing due to
miscalculation of memequal args, and the previous fix
does not handle padding at the end of a struct.

Handling of padding at end of structs also fixes the case
of [n]T where T is such a padded struct.

Fixes #4585.
(again)

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/7133059

Reference the 80386 compiler documentation now that the
documentation for the 68020 is offline.

R=golang-dev, minux.ma, rsc
CC=golang-dev
https://golang.org/cl/7127053

Reduce individual object handling by anticipating how much of them are servable.

Not a chunked transfer cache, but decent enough to make sure the bottleneck is not here.

Mac OSX, median of 10 runs:

benchmark                 old ns/op    new ns/op    delta
BenchmarkBinaryTree17    5358937333   4892813012   -8.70%
BenchmarkFannkuch11      3257752475   3315436116   +1.77%
BenchmarkGobDecode         23277349     23001114   -1.19%
BenchmarkGobEncode         14367327     14262925   -0.73%
BenchmarkGzip             441045541    440451719   -0.13%
BenchmarkGunzip           139117663    139622494   +0.36%
BenchmarkJSONEncode        45715854     45687802   -0.06%
BenchmarkJSONDecode       103949570    106530032   +2.48%
BenchmarkMandelbrot200      4542462      4548290   +0.13%
BenchmarkParse              7790558      7557540   -2.99%
BenchmarkRevcomp          831436684    832510381   +0.13%
BenchmarkTemplate         133789824    133007337   -0.58%

benchmark                  old MB/s     new MB/s  speedup
BenchmarkGobDecode            32.82        33.33    1.02x
BenchmarkGobEncode            53.42        53.86    1.01x
BenchmarkGzip                 43.70        44.01    1.01x
BenchmarkGunzip              139.09       139.14    1.00x
BenchmarkJSONEncode           42.69        42.56    1.00x
BenchmarkJSONDecode           18.78        17.91    0.95x
BenchmarkParse                 7.37         7.67    1.04x
BenchmarkRevcomp             306.83       305.70    1.00x
BenchmarkTemplate             14.57        14.56    1.00x

R=rsc, dvyukov
CC=golang-dev
https://golang.org/cl/7005055

Fixes #4666.

R=golang-dev, daniel.morsing, rsc
CC=golang-dev
https://golang.org/cl/7141047

Update #4629.

$ cat shift2.c
unsigned int
shift(unsigned int x, unsigned int y)
{
        x = (x << 3);
        y = (y << 5);
        x = (x << 7);
        y = (y << 9);
        return x ^ y;
}

## BEFORE
$ go tool 6c -S shift2.c
(shift2.c:2)	TEXT	shift+0(SB),$0-8
(shift2.c:4)	MOVL	x+0(FP),!!AX
(shift2.c:4)	SALL	$3,!!AX
(shift2.c:4)	MOVL	AX,!!DX
(shift2.c:5)	MOVL	y+4(FP),!!AX
(shift2.c:5)	SALL	$5,!!AX
(shift2.c:5)	MOVL	AX,!!CX
(shift2.c:6)	MOVL	DX,!!AX
(shift2.c:6)	SALL	$7,!!AX
(shift2.c:6)	MOVL	AX,!!DX
(shift2.c:7)	MOVL	CX,!!AX
(shift2.c:7)	SALL	$9,!!AX
(shift2.c:7)	MOVL	AX,!!CX
(shift2.c:8)	MOVL	DX,!!AX
(shift2.c:8)	XORL	CX,!!AX
(shift2.c:8)	RET	,!!
(shift2.c:8)	RET	,!!
(shift2.c:8)	END	,!!

## AFTER
$ go tool 6c -S shift2.c
(shift2.c:2)	TEXT	shift+0(SB),$0-8
(shift2.c:4)	MOVL	x+0(FP),!!AX
(shift2.c:4)	SALL	$3,!!AX
(shift2.c:5)	MOVL	y+4(FP),!!CX
(shift2.c:5)	SALL	$5,!!CX
(shift2.c:6)	SALL	$7,!!AX
(shift2.c:7)	SALL	$9,!!CX
(shift2.c:8)	XORL	CX,!!AX
(shift2.c:8)	RET	,!!
(shift2.c:8)	RET	,!!
(shift2.c:8)	END	,!!

R=rsc, minux.ma, dave, nigeltao
CC=golang-dev
https://golang.org/cl/7066055

Names beginning with a dot are ignored by optimizers.

R=rsc, lvd, golang-dev, dave
CC=golang-dev
https://golang.org/cl/7098049

Fixes #4665.

R=golang-dev, minux.ma
CC=golang-dev
https://golang.org/cl/7132057

R=rsc
CC=golang-dev
https://golang.org/cl/7101046

R=golang-dev, seed, rsc
CC=golang-dev
https://golang.org/cl/7069053

sse2 is a more precise description of the requirement,
and it matches what people will see in, for example
        grep sse2 /proc/cpuinfo # linux
        sysctl hw.optional.sse2 # os x

R=golang-dev, dsymonds, iant
CC=golang-dev
https://golang.org/cl/7057050

Decode as much as possible of a Huffman symbol in a single table
lookup (much like the zlib implementation), filling more bits
(conservatively, so we don't consume past the end of the stream)
when the code prefix indicates more bits are needed. This
results in about a 50% performance gain in speed benchmarks.
The following set is benchcmp done on a retina MacBook Pro:

benchmark                            old MB/s     new MB/s  speedup
BenchmarkDecodeDigitsSpeed1e4           28.41        42.79    1.51x
BenchmarkDecodeDigitsSpeed1e5           30.18        47.62    1.58x
BenchmarkDecodeDigitsSpeed1e6           30.81        48.14    1.56x
BenchmarkDecodeDigitsDefault1e4         30.28        44.61    1.47x
BenchmarkDecodeDigitsDefault1e5         32.18        51.94    1.61x
BenchmarkDecodeDigitsDefault1e6         35.57        53.28    1.50x
BenchmarkDecodeDigitsCompress1e4        30.39        44.83    1.48x
BenchmarkDecodeDigitsCompress1e5        33.05        51.64    1.56x
BenchmarkDecodeDigitsCompress1e6        35.69        53.04    1.49x
BenchmarkDecodeTwainSpeed1e4            25.90        43.04    1.66x
BenchmarkDecodeTwainSpeed1e5            29.97        48.19    1.61x
BenchmarkDecodeTwainSpeed1e6            31.36        49.43    1.58x
BenchmarkDecodeTwainDefault1e4          28.79        45.02    1.56x
BenchmarkDecodeTwainDefault1e5          37.12        55.65    1.50x
BenchmarkDecodeTwainDefault1e6          39.28        58.16    1.48x
BenchmarkDecodeTwainCompress1e4         28.64        44.90    1.57x
BenchmarkDecodeTwainCompress1e5         37.40        55.98    1.50x
BenchmarkDecodeTwainCompress1e6         39.35        58.06    1.48x

R=rsc, dave, minux.ma, bradfitz, nigeltao
CC=golang-dev
https://golang.org/cl/6872063

People keep not reading all the way to the bottom of the doc
and not running hg mail.

R=golang-dev, minux.ma
CC=golang-dev
https://golang.org/cl/7137057

Fixes #4585.

R=rsc, golang-dev
CC=golang-dev
https://golang.org/cl/7142052

R=golang-dev, minux.ma
CC=golang-dev
https://golang.org/cl/7139057

for slow windows-386 builder

R=golang-dev, dave, rsc
CC=golang-dev
https://golang.org/cl/7128053

This code is obsolete and unmaintained.

R=bradfitz
CC=golang-dev
https://golang.org/cl/7135056

R=golang-dev
CC=golang-dev
https://golang.org/cl/7132050

This was never documented or properly implemented.

Fixes #3528.

R=mikesamuel, rsc
CC=golang-dev
https://golang.org/cl/7142048

Fixes #4670.

R=rsc
CC=golang-dev
https://golang.org/cl/7148043

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/7132049

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/7128048

Fixes #4598.

R=golang-dev, dsymonds, r
CC=golang-dev
https://golang.org/cl/7102050

R=mdempsky, iant, r, gri, rsc, ken
CC=golang-dev
https://golang.org/cl/7100046

so that http://golang.org/pkg/runtime?m=all works.

R=bradfitz
CC=golang-dev
https://golang.org/cl/7094046

Fixes #4650.

R=golang-dev, bradfitz, alex.brainman
CC=golang-dev
https://golang.org/cl/7085048

Calling it will show memory allocation statistics for that
single benchmark (if -test.benchmem is not provided)

R=golang-dev, rsc, kevlar, bradfitz
CC=golang-dev
https://golang.org/cl/7027046

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/7131045

Fixes #4412.

R=adg, rsc, rogpeppe, andrewdg, bradfitz
CC=golang-dev
https://golang.org/cl/7086050

I think that the parser is complete enough to take that warning out.
It passes the test suite.
There may be incompatible API changes, but being in the exp directory
is warning enough for that.

R=nigeltao
CC=golang-dev
https://golang.org/cl/7131050

Rewrote existing code to prevent similar mistakes.

R=adonovan
CC=golang-dev
https://golang.org/cl/7129046

R=bradfitz
CC=golang-dev
https://golang.org/cl/7132045

We need to wait for the handler to actually finish running,
not almost be done running.

This was always a bug, but now that handler output is buffered
it shows up easily on GOMAXPROCS >1 systems.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/7109043