runtime·usleep and runtime·osyield fall back to calling an
assembly wrapper for the libc functions in the absence of a m,
so they can be called in cgo callback context.

LGTM=rsc
R=minux.ma, rsc
CC=dave, golang-codereviews
https://golang.org/cl/102620044

A temporary 512 bytes buffer is allocated for every call to
readHeader. This buffer isn't returned to the caller and it could
be reused to lower the number of memory allocations.

This CL improves it by using a pool and zeroing out the buffer before
putting it back into the pool.

benchmark                  old ns/op     new ns/op     delta
BenchmarkListFiles100k     545249903     538832687     -1.18%

benchmark                  old allocs    new allocs    delta
BenchmarkListFiles100k     2105167       2005692       -4.73%

benchmark                  old bytes     new bytes     delta
BenchmarkListFiles100k     105903472     54831527      -48.22%

This improvement is very important if your code has to deal with a lot
of tarballs which contain a lot of files.

LGTM=dsymonds
R=golang-codereviews, dave, dsymonds, bradfitz
CC=golang-codereviews
https://golang.org/cl/108240044

A temporary 512 bytes buffer is allocated for every call to
writeHeader. This buffer could be reused the lower the number
of memory allocations.

benchmark                   old ns/op     new ns/op     delta
BenchmarkWriteFiles100k     634622051     583810847     -8.01%

benchmark                   old allocs     new allocs     delta
BenchmarkWriteFiles100k     2701920        2602621        -3.68%

benchmark                   old bytes     new bytes     delta
BenchmarkWriteFiles100k     115383884     64349922      -44.23%

This change is very important if your code has to write a lot of
tarballs with a lot of files.

LGTM=dsymonds
R=golang-codereviews, dave, dsymonds
CC=golang-codereviews
https://golang.org/cl/107440043

Thanks to Cedric Staub for noting that a short session key would lead
to an out-of-bounds access when conditionally copying the too short
buffer over the random session key.

LGTM=davidben, bradfitz
R=davidben, bradfitz
CC=golang-codereviews
https://golang.org/cl/102670044

The main changes fall into a few patterns:

1. Replace #define with enum.

2. Add /*c2go */ comment giving effect of #define.
This is necessary for function-like #defines and
non-enum-able #defined constants.
(Not all compilers handle negative or large enums.)

3. Add extra braces in struct initializer.
(c2go does not implement the full rules.)

This is enough to let c2go typecheck the source tree.
There may be more changes once it is doing
other semantic analyses.

LGTM=minux, iant
R=minux, dave, iant
CC=golang-codereviews
https://golang.org/cl/106860045

LGTM=josharian
R=golang-codereviews, josharian
CC=golang-codereviews
https://golang.org/cl/110330043

LGTM=iant
R=golang-codereviews, iant, bradfitz
CC=golang-codereviews
https://golang.org/cl/107390044

Generated by a+c.

R=gobot
CC=golang-codereviews
https://golang.org/cl/111820043

Generated by a+c.

R=gobot
CC=golang-codereviews
https://golang.org/cl/107450043

A TLS slot is reserved by _rt0_.*_plan9 as an automatic and
its address (which is static on Plan 9) is saved in the
global _privates symbol. The startup linkage now is exactly
like that from Plan 9 libc, and the way we access g is
exactly as if we'd have used privalloc(2).

Aside from making the code more standard, this change
drastically simplifies it, both for 386 and for amd64, and
makes the Plan 9 code in liblink common for both 386 and
amd64.

The amd64 runtime code was cleared of nxm assumptions, and
now runs on the standard Plan 9 kernel.

Note handling fixes will follow in a separate CL.

LGTM=rsc
R=golang-codereviews, rsc, bradfitz, dave
CC=0intro, ality, golang-codereviews, jas, minux.ma, mischief
https://golang.org/cl/101510049

We restored registers correctly in the usual case where the thread
is a Go-managed thread and called runtime·sighandler, but we
failed to do so when runtime·sigtramp was called on a cgo-created
thread. In that case, runtime·sigtramp called runtime·badsignal,
a Go function, and did not restore registers after it returned

LGTM=rsc, dave
R=rsc, dave
CC=golang-codereviews, minux.ma
https://golang.org/cl/105280050

On amd64, the real time is reduced from 176.76s to 140.26s.
On ARM, the real time is reduced from 921.61s to 726.30s.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/101580043

As android and linux have significant overlap, and
because build tags are a poor way to represent an
OS target, this CL introduces an exception into
go/build: linux is treated as a synonym for android
when matching files.

http://golang.org/s/go14android
https://groups.google.com/forum/#!topic/golang-dev/P1ATVp1mun0

LGTM=rsc, minux
R=golang-codereviews, mikioh.mikioh, dave, aram, minux, gobot, rsc, aram.h, elias.naur, iant
CC=golang-codereviews, rsc
https://golang.org/cl/105270043

Move decAlloc calls a bit higher in the call tree.
Cleans code marginally, improves speed marginally.
The benchmarks are noisy but the median time from
20 consective 1-second runs improves by about 2%.

LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/105530043

3-index slices of the form s[:len(s):len(s)]
cannot be simplified to s[::len(s)].

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/108330043

TBR=rsc
R=golang-codereviews
CC=golang-codereviews
https://golang.org/cl/111770043

Fixes #7631.

LGTM=gri
R=golang-codereviews, bradfitz, gri
CC=golang-codereviews
https://golang.org/cl/101410046

Generated by a+c.

R=gobot, rsc
CC=golang-codereviews
https://golang.org/cl/106340043

LGTM=rsc
R=rsc, minux
CC=golang-codereviews
https://golang.org/cl/105480043

CC=golang-codereviews
https://golang.org/cl/101590043

We are not the right people to support editor plugins, and the profusion
of editors in this CL demonstrates the unreality of pretending to do so.
People are free to create and advertise their own repos with support.

For discussion: https://groups.google.com/forum/#!topic/golang-dev/SA7fD470FxU

LGTM=rminnich, kamil.kisiel, gri, rsc, dave, josharian, ruiu
R=golang-codereviews, rminnich, kamil.kisiel, gri, rsc, dominik.honnef, dave, josharian, ruiu, ajstarks
CC=golang-codereviews
https://golang.org/cl/105470043

There is no reason to generate different code for cap and len.

Fixes #8025.
Fixes #8026.

LGTM=rsc
R=rsc, iant, khr
CC=golang-codereviews
https://golang.org/cl/93570044

Breaks windows and race detector.
TBR=rsc

««« original CL description
runtime: stack allocator, separate from mallocgc

In order to move malloc to Go, we need to have a
separate stack allocator.  If we run out of stack
during malloc, malloc will not be available
to allocate a new stack.

Stacks are the last remaining FlagNoGC objects in the
GC heap.  Once they are out, we can get rid of the
distinction between the allocated/blockboundary bits.
(This will be in a separate change.)

Fixes #7468
Fixes #7424

LGTM=rsc, dvyukov
R=golang-codereviews, dvyukov, khr, dave, rsc
CC=golang-codereviews
https://golang.org/cl/104200047
»»»

TBR=rsc
CC=golang-codereviews
https://golang.org/cl/101570044

In order to move malloc to Go, we need to have a
separate stack allocator.  If we run out of stack
during malloc, malloc will not be available
to allocate a new stack.

Stacks are the last remaining FlagNoGC objects in the
GC heap.  Once they are out, we can get rid of the
distinction between the allocated/blockboundary bits.
(This will be in a separate change.)

Fixes #7468
Fixes #7424

LGTM=rsc, dvyukov
R=golang-codereviews, dvyukov, khr, dave, rsc
CC=golang-codereviews
https://golang.org/cl/104200047

LGTM=minux
R=golang-codereviews, minux
CC=golang-codereviews
https://golang.org/cl/109220046

The old code's structure needed to track indirections because of the
use of unsafe. That is no longer necessary, so we can remove all
that tracking. The code cleans up considerably but is a little slower.
We may be able to recover that performance drop. I believe the
code quality improvement is worthwhile regardless.

BenchmarkEndToEndPipe           5610          5780          +3.03%
BenchmarkEndToEndByteBuffer     3156          3222          +2.09%

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/103700043

If the actual types of two reflect values are
the same and the values are structs, they must
have the same number of fields.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/108280043

CC=golang-codereviews
https://golang.org/cl/103690043

This removes a major unsafe thorn in our side, a perennial obstacle
to clean garbage collection.
Not coincidentally: In cleaning this up, several bugs were found,
including code that reached inside by-value interfaces to create
pointers for pointer-receiver methods. Unsafe code is just as
advertised.

Performance of course suffers, but not too badly. The Pipe number
is more indicative, since it's doing I/O that simulates a network
connection. Plus these are end-to-end, so each end suffers
only half of this pain.

The edit is pretty much a line-by-line conversion, with a few
simplifications and a couple of new tests. There may be more
performance to gain.

BenchmarkEndToEndByteBuffer     2493          3033          +21.66%
BenchmarkEndToEndPipe           4953          5597          +13.00%

Fixes #5159.

LGTM=rsc
R=rsc
CC=golang-codereviews, khr
https://golang.org/cl/102680045

Fix copy paste error pointed out by rsc, https://golang.org/cl/107290043/diff/60001/test/fixedbugs/issue8074.go#newcode7

LGTM=ruiu, r
R=golang-codereviews, ruiu, r
CC=golang-codereviews
https://golang.org/cl/106210047

Fixes #8299.

R=golang-codereviews
CC=golang-codereviews, khr, rsc
https://golang.org/cl/103640044

LGTM=r
R=golang-codereviews, bradfitz, r
CC=golang-codereviews
https://golang.org/cl/109220044

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/101510047

The only text that describes the accepted format is in the package doc,
which is far away from these functions. The other flag types don't need
this explicitness because they are more obvious.

LGTM=r
R=r
CC=golang-codereviews
https://golang.org/cl/101550043

R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/110080045

Remove GC bitmap backward scanning.
This was already done once in https://golang.org/cl/5530074/
Still makes GC a bit faster.
On the garbage benchmark, before:
        gc-pause-one=237345195
        gc-pause-total=4746903
        cputime=32427775
        time=32458208
after:
        gc-pause-one=235484019
        gc-pause-total=4709680
        cputime=31861965
        time=31877772
Also prepares mgc0.c for future changes.

R=golang-codereviews, khr, khr
CC=golang-codereviews, rsc
https://golang.org/cl/105380043

newproc takes two extra pointers, not two extra registers.
On amd64p32 (nacl) they are different.

We diagnosed this before the 1.3 cut but the tree was frozen.
I believe this is causing the random problems on the builder.

Fixes #8199.

TBR=r
CC=golang-codereviews
https://golang.org/cl/102710043

Include these files in the build,
even though they don't get executed.

LGTM=r
R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/108180043

LGTM=r
R=golang-codereviews, bradfitz, r
CC=golang-codereviews
https://golang.org/cl/102640046

LGTM=0intro, aram
R=rsc, 0intro, aram
CC=golang-codereviews
https://golang.org/cl/109240044