Fold the comparison when the SHR result is small.

Useful for:
- murmur mix like hashing where higher bits are desirable, i.e. hash = uint32(i * C) >> 18
- integer log2 via DeBruijn sequence: http://graphics.stanford.edu/~seander/bithacks.html#IntegerLogDeBruijn

Change-Id: If70ae18cb86f4cc83ab6213f88ced03cc4986156
Reviewed-on: https://go-review.googlesource.com/21514
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

The test for profiling of channel blocking is timing dependent,
and in particular the blockSelectRecvAsync case can fail on a
slow builder (plan9_arm) when many tests are run in parallel.
The child goroutine sleeps for a fixed period so the parent
can be observed to block in a select call reading from the
child; but if the OS process running the parent goroutine is
delayed long enough, the child may wake again before the
parent has reached the blocking point.  By repeating the test
three times, the likelihood of a blocking event is increased.

Fixes #15096

Change-Id: I2ddb9576a83408d06b51ded682bf8e71e53ce59e
Reviewed-on: https://go-review.googlesource.com/21604Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Merge the remaining lfstack{Pack,Unpack} implemetations into one file.

unsafe.Sizeof(uintptr(0)) == 4 is a constant comparison so this branch
folds away at compile time.

Dmitry confirmed that the upper 17 bits of an address will be zero for a
user mode pointer, so there is no need to sign extend on amd64 during
unpack, so we can reuse the same implementation as all othe 64 bit
archs.

Change-Id: I99f589416d8b181ccde5364c9c2e78e4a5efc7f1
Reviewed-on: https://go-review.googlesource.com/21597
Run-TryBot: Dave Cheney <dave@cheney.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>

Change-Id: I2da012ed996c669db513a462f014c6f3ffa396ee
Reviewed-on: https://go-review.googlesource.com/21646Reviewed-by: Mikio Hara <mikioh.mikioh@gmail.com>

API could still be made more Go-ey.

Updates #15165.

Change-Id: I514ffceffa43c293ae5d7e5f1e9193fda0098865
Reviewed-on: https://go-review.googlesource.com/21644Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

RIP architecture characters.

Change-Id: I36f53afdc311b14b9459ff3821bd6df54a057ded
Reviewed-on: https://go-review.googlesource.com/21628Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Dave Cheney <dave@cheney.net>

Change-Id: I858054b72847f4f27a1ebbdaff82820a28c03743
Reviewed-on: https://go-review.googlesource.com/21627Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Two of these error messages are already dead code: cmd/compile.main
and cmd/link.main already switch on $GOARCH, ensuring it must be a
prefix of the sys.Arch.Family.

The error message about uncompiled Go source files can be just be
simplified: anyone who's manually constructing Go object file archives
probably knows what tool to use to compile Go source files.

Change-Id: Ia4a67c0a1d1158379c127c91e909226d3367f3c2
Reviewed-on: https://go-review.googlesource.com/21626
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Information about CPU architectures (e.g., name, family, byte
ordering, pointer and register size) is currently redundantly
scattered around the source tree. Instead consolidate the basic
information into a single new package cmd/internal/sys.

Also, introduce new sys.I386, sys.AMD64, etc. names for the constants
'8', '6', etc. and replace most uses of the latter. The notable
exceptions are a couple of error messages that still refer to the old
char-based toolchain names and function reltype in cmd/link.

Passes toolstash/buildall.

Change-Id: I8a6f0cbd49577ec1672a98addebc45f767e36461
Reviewed-on: https://go-review.googlesource.com/21623Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

So that all Go processes do not die on startup on a system with >256 CPUs.

I tested this by hacking osinit to set ncpu to 1000.

Updates #15131

Change-Id: I52e061a0de97be41d684dd8b748fa9087d6f1aef
Reviewed-on: https://go-review.googlesource.com/21599Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

This updates dwarf.go to generate debug information as symbols
instead of directly writing to the output file. This should make
it easier to move generation of some of the debug info into the compiler.

Change-Id: Id2358988bfb689865ab4d68f82716f0676336df4
Reviewed-on: https://go-review.googlesource.com/20679Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Includes assembly implementations of Sqrt and Dim.

Change-Id: I57472e8d31e2ee74bcebf9f8e818f765eb9b8abf
Reviewed-on: https://go-review.googlesource.com/20936Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Change-Id: I4ffb79d8cb08b0b44f59757fb7f0ec3ed1e4479f
Reviewed-on: https://go-review.googlesource.com/21624Reviewed-by: Matthew Dempsky <mdempsky@google.com>

Relatively few types are ever used as map keys,
so tracking this separately is a net win.

Passes toolstash -cmp.

name       old alloc/op     new alloc/op     delta
Template       55.9MB ± 0%      55.5MB ± 0%  -0.71%        (p=0.000 n=10+10)
Unicode        37.8MB ± 0%      37.7MB ± 0%  -0.27%        (p=0.000 n=10+10)
GoTypes         180MB ± 0%       179MB ± 0%  -0.52%         (p=0.000 n=7+10)
Compiler        806MB ± 0%       803MB ± 0%  -0.41%        (p=0.000 n=10+10)

CPU and number of allocs are unchanged.

Change-Id: I6d60d74a4866995a231dfed3dd5792d75d904292
Reviewed-on: https://go-review.googlesource.com/21622Reviewed-by: Matthew Dempsky <mdempsky@google.com>

This function is present in the strings package but missing from bytes,
and we would like to keep the two packages consistent.

Add it to bytes, and copy the test over as well.

Fixes #15140

Change-Id: I5dbd28da83a9fe741885794ed15f2af2f826cb3c
Reviewed-on: https://go-review.googlesource.com/21562Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

None of the two places that call lfstackUnpack use the second argument.
This simplifies a followup CL that merges the lfstack{Pack,Unpack}
implementations.

Change-Id: I3c93f6259da99e113d94f8c8027584da79c1ac2c
Reviewed-on: https://go-review.googlesource.com/21595
Run-TryBot: Dave Cheney <dave@cheney.net>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Where possible replace ANDQ with MOV?ZX.
Takes care that we don't regress wrt bounds checking,
for example [1000]int{}[i&255].

According to "Intel 64 and IA-32 Architectures Optimization Reference
Manual" Section: "3.5.1.13 Zero-Latency MOV Instructions"
MOV?ZX instructions have zero latency on newer processors.

Updates #15105

Change-Id: I63539fdbc5812d5563aa1ebc49eca035bd307997
Reviewed-on: https://go-review.googlesource.com/21508Reviewed-by: Айнар Гарипов <gugl.zadolbal@gmail.com>
Reviewed-by: David Chase <drchase@google.com>

Fixes #13783.

Change-Id: I0122c1f0cf4075acabf5f58241bded1835699dc1
Reviewed-on: https://go-review.googlesource.com/19725Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Flaky tests are a distraction and cover up real problems.

File bugs instead and mark them as flaky.

This moves the net/http flaky test flagging mechanism to internal/testenv.

Updates #15156
Updates #15157
Updates #15158

Change-Id: I0e561cd2a09c0dec369cd4ed93bc5a2b40233dfe
Reviewed-on: https://go-review.googlesource.com/21614Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

Many of Type's fields are etype-specific.
This CL organizes them into their own auxiliary types,
duplicating a few fields as necessary,
and adds an Extra field to hold them.
It also sorts the remaining fields for better struct packing.
It also improves documentation for most fields.

This reduces the size of Type at the cost of some extra allocations.
There's no CPU impact; memory impact below.
It also makes the natural structure of Type clearer.

Passes toolstash -cmp on all architectures.

Ideas for future work in this vein:

(1) Width and Align probably only need to be
stored for Struct and Array types.
The refactoring to accomplish this would hopefully
also eliminate TFUNCARGS and TCHANARGS entirely.

(2) Maplineno is sparsely used and could probably better be
stored in a separate map[*Type]int32, with mapqueue updated
to store both a Node and a line number.

(3) The Printed field may be removable once the old (non-binary)
importer/exported has been removed.

(4) StructType's fields field could be changed from *[]*Field to []*Field,
which would remove a common allocation.

(5) I believe that Type.Nod can be moved to ForwardType. Separate CL.

name       old alloc/op     new alloc/op     delta
Template       57.9MB ± 0%      55.9MB ± 0%  -3.43%        (p=0.000 n=50+50)
Unicode        38.3MB ± 0%      37.8MB ± 0%  -1.39%        (p=0.000 n=50+50)
GoTypes         185MB ± 0%       180MB ± 0%  -2.56%        (p=0.000 n=50+50)
Compiler        824MB ± 0%       806MB ± 0%  -2.19%        (p=0.000 n=50+50)

name       old allocs/op    new allocs/op    delta
Template         486k ± 0%        497k ± 0%  +2.25%        (p=0.000 n=50+50)
Unicode          377k ± 0%        379k ± 0%  +0.55%        (p=0.000 n=50+50)
GoTypes         1.39M ± 0%       1.42M ± 0%  +1.63%        (p=0.000 n=50+50)
Compiler        5.52M ± 0%       5.57M ± 0%  +0.84%        (p=0.000 n=47+50)

Change-Id: I828488eeb74902b013d5ae4cf844de0b6c0dfc87
Reviewed-on: https://go-review.googlesource.com/21611Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Test goprint.go sometimes failed on a slow builder (plan9_arm)
because of timing dependency.  Instead of sleeping for a fixed
time to allow the child goroutine to finish, wait explicitly for
child termination by calling runtime.NumGoroutine until the
returned value is 1.

Fixes #15097

Change-Id: Ib3ef5ec3c8277083c774542f48bcd4ff2f79efde
Reviewed-on: https://go-review.googlesource.com/21603Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

allow for more than 0.00s.

Fixes #15149

Change-Id: I1d428a9b3c9bb3d1db8682c53b86e44cecc1dde1
Reviewed-on: https://go-review.googlesource.com/21602Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Marcel van Lohuizen <mpvl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

A dot-import cannot possibly introduce a `len` function since that
function would not be exported (it's lowercase). Furthermore, the
existing code already (incorrectly) assumed that there was no other
`len` function in another file of the package. Since this has been
an ok assumption for years, let's leave it, but remove the dot-import
restriction.

Fixes #15153.

Change-Id: I18fbb27acc5a5668833b4b4aead0cca540862b52
Reviewed-on: https://go-review.googlesource.com/21613Reviewed-by: Alan Donovan <adonovan@google.com>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

- Automatically determine the first argument to check.
- Skip checking matching non-variadic functions.
- Skip checking matching functions accepting non-interface{}
  variadic arguments.
- Removed fragile 'magic' code for special cases such as math.Log
  and error interface.

Fixes #15067
Fixes #15099

Change-Id: Ib313557f18b12b36daa493f4b02c598b9503b55b
Reviewed-on: https://go-review.googlesource.com/21513
Run-TryBot: Rob Pike <r@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

We already have variables to track whether the target platform is
64-bit vs 32-bit or RELA vs REL, so no point in repeating the list of
obscure architecture characters everywhere.

Passes toolstash/buildall.

Change-Id: I6a07f74188ac592ef229a7c65848a9ba93013cdb
Reviewed-on: https://go-review.googlesource.com/21569
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

This broke T.Run

Change-Id: I12c8fe3612f3fa2caa83049c1c7003056daf2b0c
Reviewed-on: https://go-review.googlesource.com/21600
Run-TryBot: Marcel van Lohuizen <mpvl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: Ie4c4ff4167ee45ae93a8b764fb6197f402e7994d
Reviewed-on: https://go-review.googlesource.com/21593Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #15118

Change-Id: Iad56ed412535c8ac0a01c4bd7769fd3d37688ac9
Reviewed-on: https://go-review.googlesource.com/21526
Run-TryBot: Rob Pike <r@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

Even with -D_POSIX_PTHREAD_SEMANTICS, Solaris seems to not define
getgrnam_r in a POSIX compatible way.

Fixes #14967

Change-Id: I78cb7e5b30b2d8b860e336060a0a06f4720c0475
Reviewed-on: https://go-review.googlesource.com/21385Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #15076

Change-Id: I5ce8f6253245d8cc1f862a1bf618775f557f955d
Reviewed-on: https://go-review.googlesource.com/21610Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

No point in doing anything for x=x assignments.
In addition, skipping these assignments prevents generating:
    VARDEF x
    COPY x -> x
which is bad because x is incorrectly considered
dead before the vardef.

Fixes #14904

Change-Id: I6817055ec20bcc34a9648617e0439505ee355f82
Reviewed-on: https://go-review.googlesource.com/21470Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Dave Cheney <dave@cheney.net>

Merge all the 64bit lfstack impls into one file, adjust build tags to
match.

Merge all the comments on the various lfstack implementations for
posterity.

lfstack_amd64.go can probably be merged, but it is slightly different so
that will happen in a followup.

Change-Id: I5362d5e127daa81c9cb9d4fa8a0cc5c5e5c2707c
Reviewed-on: https://go-review.googlesource.com/21591
Run-TryBot: Dave Cheney <dave@cheney.net>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>

Change-Id: I463ca59f486b2842f67f151a55f530ee10663830
Reviewed-on: https://go-review.googlesource.com/21568
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Dave Cheney <dave@cheney.net>
Reviewed-by: Minux Ma <minux@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Change-Id: I11172f3d0e28f17b812e67a4db9cfe513b8e1974
Reviewed-on: https://go-review.googlesource.com/21565Reviewed-by: Minux Ma <minux@golang.org>

A future CL will rename os1_windows.go to os_windows.go.

Change-Id: I223e76002dd1e9c9d1798fb0beac02c7d3bf4812
Reviewed-on: https://go-review.googlesource.com/21564
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>

Change-Id: Ib79ad4a890994ad64edb1feb79bd242d26b5b08a
Reviewed-on: https://go-review.googlesource.com/20945Reviewed-by: Minux Ma <minux@golang.org>
Run-TryBot: Michael Munday <munday@ca.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #15147.

Change-Id: Ibfe46c747dea987787a51eb0c95ccd8c5f24f366
Reviewed-on: https://go-review.googlesource.com/21580
Run-TryBot: Minux Ma <minux@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: I1f975130179cf26af67e82664310b93d43e87a75
Reviewed-on: https://go-review.googlesource.com/20944Reviewed-by: Minux Ma <minux@golang.org>
Run-TryBot: Michael Munday <munday@ca.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

ReadAtSizer is a common abstraction for a stateless,
concurrently-readable fixed number of bytes.

This interface has existed in various codebases for over 3 years (previously
usually named SizeReaderAt). It is used inside Google in dl.google.com
(mentioned in https://talks.golang.org/2013/oscon-dl.slide) and other
packages. It is used in Camlistore, in Juju, in the Google API Go client, in
github.com/nightlyone/views, and 33 other pages of Github search results.

It is implemented by io.SectionReader, bytes.Reader, strings.Reader, etc.

Time to finally promote this interface to the standard library and give it a
standard name, blessing it as best practice.

Updates #7263
Updates #14889

Change-Id: Id28c0cafa7d2d37e8887c54708b5daf1b11c83ea
Reviewed-on: https://go-review.googlesource.com/21492Reviewed-by: Rob Pike <r@golang.org>

Change-Id: I938f61763c3256a876d62aeb54ef8c25cc4fc90e
Reviewed-on: https://go-review.googlesource.com/21567Reviewed-by: Minux Ma <minux@golang.org>