This is the first version of an introductory document that should help
developers who want to get started with this package.

I recently started poking around this part of the compiler, and was
confused by a few basic ideas such as memory arguments. I also hadn't
heard about GOSSAFUNC until another developer pointed it out. Both of
those are essential if one wants to do any non-trivial work here.

This document can of course be expanded with more pointers and tips to
better understand this package's code and behavior. Its intent is not to
cover all of its features; but it should be enough for most developers
to start playing with it without extensive compiler experience.

Change-Id: Ifd2d047fbd038ab50f4625a15c4d49932b42fd66
Reviewed-on: https://go-review.googlesource.com/99715Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

Follow the Linux Kernel 4.15
Add Arm64 minimalFeatures test

Change-Id: I1c092521ba59b1e4096c27786fa0464f9ef7d311
Reviewed-on: https://go-review.googlesource.com/103636
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: I629d89d5065271f3b92dde8b12f0e743c9bde8f0
Reviewed-on: https://go-review.googlesource.com/103595Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixed a broken link to a section in the documentation for the
test flags for the go command.

Change-Id: Ic4bdd4965aac7856dd13a2adda9d774b9bae4113
GitHub-Last-Rev: 15bda340674c268a92f43a2820eca50482940de1
GitHub-Pull-Request: golang/go#24613
Reviewed-on: https://go-review.googlesource.com/103835Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

CL 40693 added concurrent backend compilation support,
and used it for user-provided functions.
Autogenerated functions were still compiled serially.
This CL brings them into the fold.
As of this CL, when requested,
no functions are compiled serially.

There generally aren't many autogenerated functions.
When there are, this CL can help a lot,
because autogenerated functions are usually short.
Many short functions is the best case scenario
for concurrent compilation; see CL 41192.

One example of such a package comes from Dave Cheney's benchjuju:
github.com/juju/govmomi/vim25/types.
It has thousands of autogenerated functions.
This CL improves performance on the entire benchmark
by around a second on my machine at c=8, or about ~5%.

Updates #15756

Change-Id: Ia21e302b2469a9ed743df02244ec7ebde55b32f3
Reviewed-on: https://go-review.googlesource.com/41503
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

Fixes #24610

Change-Id: I76dee97db7cd77fe03e4a224f679a5efd061a2b5
Reviewed-on: https://go-review.googlesource.com/103775Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

This commit allows architectures to disable optimizations that need the
Avg* and Hmul* operations.

WebAssembly has no such operations, so using them as an optimization
but then having to emulate them with multiple instructions makes no
sense, especially since the WebAssembly compiler may do the same
optimizations internally.

Updates #18892

Change-Id: If57b59e3235482a9e0ec334a7312b3e3b5fc2b61
Reviewed-on: https://go-review.googlesource.com/103256
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

This is the first commit of a series that will add WebAssembly
as an architecture target. The design document can be found at
https://docs.google.com/document/d/131vjr4DH6JFnb-blm_uRdaC0_Nv3OUwjEY5qVCxCup4.

The GOARCH name "wasm" is the official abbreviation of WebAssembly.
The GOOS name "js" got chosen because initially the host environment
that executes WebAssembly bytecode will be web browsers and Node.js,
which both use JavaScript to embed WebAssembly. Other GOOS values
may be possible later, see:
https://github.com/WebAssembly/design/blob/master/NonWeb.md

Updates #18892

Change-Id: Ia25b4fa26bba8029c25923f48ad009fd3681933a
Reviewed-on: https://go-review.googlesource.com/102835
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: I6f5a94cd8b6e8f7201202514ac0f9c78811c43bc
Reviewed-on: https://go-review.googlesource.com/103695Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: I6bfbbce2ec5dfc7f9f99dbd82e51c2b0edacc87a
Reviewed-on: https://go-review.googlesource.com/59334
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Apply the same approach as in CL 102397.

Updates #24580

Change-Id: I65955f62a70807c87216519d03f3643a8f214dee
Reviewed-on: https://go-review.googlesource.com/103655Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

And delete them from asm_test.

Change-Id: Idfe1249052d82d15b9c30b292c78656a0bf7b48d
Reviewed-on: https://go-review.googlesource.com/103315
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

This commit adds scripts for running the WebAssembly binaries that the
Go compiler will produce.

The script go_js_wasm_exec uses Node.js to run the binaries. Adding it
to PATH will enable "go run" and "go test" to work for js/wasm
without having to manually provide the -exec flag.
See https://golang.org/cmd/go/#hdr-Compile_and_run_Go_program
for more information.

The web page wasm_exec.html is an example on how to run the same
binaries in a web browser.

Both scripts use wasm_exec.js as a shared library.

Updates #18892

Change-Id: Ia4d9bea025957750baa0d0651243dc88f156f85d
Reviewed-on: https://go-review.googlesource.com/103255Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The ModeType constant is a bit-wise OR of several other values.
It is reasonable for this to change without breaking compatibility.

This fixes the failures introduced by https://golang.org/cl/103597

Change-Id: I817e351cf3d1e0115dce665c8efbce21bc36426c
Reviewed-on: https://go-review.googlesource.com/103616
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #23291.

Change-Id: I9bb3b8246968693871d4800e2cdb2c8390f4b6a6
GitHub-Last-Rev: bc3444206764016b730d770a8c71a49c214ae824
GitHub-Pull-Request: golang/go#24600
Reviewed-on: https://go-review.googlesource.com/103516Reviewed-by: Rob Pike <r@golang.org>

Map the error returned when a dial is aborted from the context package
error to the internal net package error. For example, context.Canceled
errors map to errCanceled, and context.DeadlineExceeded errors map to
poll.ErrTimeout.

Fixes #23648

Change-Id: Idf9d3d08052d540740c0b054503aaed931dc5b1e
Reviewed-on: https://go-review.googlesource.com/103518
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

There is currently no way for os.FileMode.IsRegular to report false
without being one of the following types:
	ModeDir | ModeSymlink | ModeNamedPipe | ModeSocket | ModeDevice

This makes it difficult for custom implementations of os.FileInfo to return
a Mode that is explicitly not regular without resorting to setting one
of the types listed above. However, every one of the aforementioned types
are ill-suited as a general-purpose "not regular" file type.

Thus, add a ModeIrregular to serve exactly for that purpose.
The ModeIrregular type carries no information other than the fact that the
file is not regular.

Updates #22903
Fixes #23878

Change-Id: I4f34d88f960bcb014816d8e7b5de8b1035077948
Reviewed-on: https://go-review.googlesource.com/94856Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Before this change, the smallest result Ldexp can handle was
ldexp(2, -1075), which is SmallestNonzeroFloat64.
There are some numbers below it should also be rounded to
SmallestNonzeroFloat64. The change fixes this.

Fixes #23407

Change-Id: I76f4cb005a6e9ccdd95b5e5c734079fd5d29e4aa
Reviewed-on: https://go-review.googlesource.com/87338
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

Incorporate https://code-review.googlesource.com/#/c/re2/+/3050/ from
the re2 repository. Description of that change:

    Preserve the original behaviour of \s.

    Prior to Perl 5.18, \s did not match vertical tab. Bake that into
    make_perl_groups.pl as an override so that perl_groups.cc retains
    its current definitions when rebuilt with newer versions of Perl.

This fixes make_perl_groups.pl to generate an unchanged perl_groups.go
with perl versions 5.18 and later.

Fixes #22057

Change-Id: I9a56e9660092ed6c1ff1045b4a3847de355441a7
Reviewed-on: https://go-review.googlesource.com/103517
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Pulling these operations out separately so it's easier to add
instrumentation calls.

Passes toolstash-check.

Updates #19054.

Change-Id: If6a537124a87bac2eceff1d66d9df5ebb3bf07be
Reviewed-on: https://go-review.googlesource.com/102816Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Change-Id: I99407e27e340689009af798989b33cef7cb92070
Reviewed-on: https://go-review.googlesource.com/103376
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

This change modifies the codegen test harness driver so that it no
longer modifies the environment GOOS/GOARCH, since that seems to cause
flakiness in other concurrently-running tests.

The change also enables the codegen tests in run.go.

Fixes #24538

Change-Id: I997ac1eb38eb92054efff67fe5c4d3cccc86412b
Reviewed-on: https://go-review.googlesource.com/103455
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

This resolves a long-standing regalloc TODO:
If you must evict a register, choose to evict a register
containing a rematerializable value, since that value
won't need to be spilled.

Provides very minor performance and size improvements.

name                     old time/op    new time/op    delta
BinaryTree17-8              2.20s ± 3%     2.18s ± 2%  -0.77%  (p=0.000 n=45+49)
Fannkuch11-8                2.14s ± 2%     2.15s ± 2%  +0.73%  (p=0.000 n=43+44)
FmtFprintfEmpty-8          30.6ns ± 4%    30.2ns ± 3%  -1.14%  (p=0.000 n=50+48)
FmtFprintfString-8         54.5ns ± 6%    53.6ns ± 5%  -1.64%  (p=0.001 n=50+48)
FmtFprintfInt-8            58.0ns ± 7%    57.6ns ± 4%    ~     (p=0.220 n=50+50)
FmtFprintfIntInt-8         85.3ns ± 2%    84.8ns ± 3%  -0.62%  (p=0.001 n=44+47)
FmtFprintfPrefixedInt-8    93.9ns ± 6%    93.6ns ± 5%    ~     (p=0.706 n=50+48)
FmtFprintfFloat-8           178ns ± 4%     177ns ± 4%    ~     (p=0.107 n=49+50)
FmtManyArgs-8               376ns ± 4%     374ns ± 3%  -0.58%  (p=0.013 n=45+50)
GobDecode-8                4.77ms ± 2%    4.76ms ± 3%    ~     (p=0.059 n=47+46)
GobEncode-8                4.04ms ± 2%    3.99ms ± 3%  -1.13%  (p=0.000 n=49+49)
Gzip-8                      177ms ± 2%     180ms ± 3%  +1.43%  (p=0.000 n=48+48)
Gunzip-8                   28.5ms ± 6%    28.3ms ± 5%    ~     (p=0.104 n=50+49)
HTTPClientServer-8         72.1µs ± 1%    72.0µs ± 1%  -0.15%  (p=0.042 n=48+42)
JSONEncode-8               9.81ms ± 5%   10.03ms ± 6%  +2.29%  (p=0.000 n=50+49)
JSONDecode-8               39.2ms ± 3%    39.3ms ± 2%    ~     (p=0.095 n=49+49)
Mandelbrot200-8            3.48ms ± 2%    3.46ms ± 2%  -0.80%  (p=0.000 n=47+48)
GoParse-8                  2.54ms ± 3%    2.51ms ± 3%  -1.35%  (p=0.000 n=49+49)
RegexpMatchEasy0_32-8      66.0ns ± 7%    65.7ns ± 8%    ~     (p=0.331 n=50+50)
RegexpMatchEasy0_1K-8       155ns ± 4%     154ns ± 4%    ~     (p=0.986 n=49+50)
RegexpMatchEasy1_32-8      62.6ns ± 8%    62.2ns ± 5%    ~     (p=0.395 n=50+49)
RegexpMatchEasy1_1K-8       260ns ± 5%     255ns ± 3%  -1.92%  (p=0.000 n=49+49)
RegexpMatchMedium_32-8     92.9ns ± 2%    91.8ns ± 2%  -1.25%  (p=0.000 n=46+48)
RegexpMatchMedium_1K-8     27.7µs ± 3%    27.0µs ± 2%  -2.59%  (p=0.000 n=49+49)
RegexpMatchHard_32-8       1.23µs ± 4%    1.21µs ± 2%  -2.16%  (p=0.000 n=49+44)
RegexpMatchHard_1K-8       36.4µs ± 2%    35.7µs ± 2%  -1.87%  (p=0.000 n=48+49)
Revcomp-8                   274ms ± 2%     276ms ± 3%  +0.70%  (p=0.034 n=45+48)
Template-8                 45.1ms ± 8%    45.1ms ± 8%    ~     (p=0.643 n=50+50)
TimeParse-8                 223ns ± 2%     223ns ± 2%    ~     (p=0.401 n=47+47)
TimeFormat-8                245ns ± 2%     246ns ± 3%    ~     (p=0.758 n=49+50)
[Geo mean]                 36.5µs         36.3µs       -0.54%


name        old object-bytes  new object-bytes  delta
Template          480kB ± 0%        480kB ± 0%    ~     (all equal)
Unicode           214kB ± 0%        214kB ± 0%    ~     (all equal)
GoTypes          1.54MB ± 0%       1.54MB ± 0%  -0.03%  (p=0.008 n=5+5)
Compiler         5.75MB ± 0%       5.75MB ± 0%    ~     (all equal)
SSA              14.6MB ± 0%       14.6MB ± 0%  -0.01%  (p=0.008 n=5+5)
Flate             300kB ± 0%        300kB ± 0%  -0.01%  (p=0.008 n=5+5)
GoParser          366kB ± 0%        366kB ± 0%    ~     (all equal)
Reflect          1.20MB ± 0%       1.20MB ± 0%    ~     (all equal)
Tar               413kB ± 0%        413kB ± 0%    ~     (all equal)
XML               529kB ± 0%        528kB ± 0%  -0.13%  (p=0.008 n=5+5)
[Geo mean]        909kB             909kB       -0.02%


Change-Id: I46d37a55197683a98913f35801dc2b0d609653c8
Reviewed-on: https://go-review.googlesource.com/103240
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

The existing behaviour of go generate is to pass GOPACKAGE=p
to all package files, including XTest files. This however is
incorrect as the package name for the XTest files is p_test.

Fixes #24594

Change-Id: I96b6e5777ec511cdcf1a6267a43f4d8c544c4af3
Reviewed-on: https://go-review.googlesource.com/103415
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Mostly same as golang.org/cl/102156, except the parts that
deal with different data types.

Change-Id: I061b858b73898725e3bf175ed022c2e3e55fc485
Reviewed-on: https://go-review.googlesource.com/103158Reviewed-by: Andrew Bonventre <andybons@golang.org>

Using go test -c makes you responsible for managing and merging the
coverage profile yourself.

Fixes #24588

Change-Id: I2037a91ceb904f9f35d76c7b5e5fae6bcbed4e46
Reviewed-on: https://go-review.googlesource.com/103395
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: If56bd72917a9cbf5920ae8b5a36dc67f10959b94
Reviewed-on: https://go-review.googlesource.com/103175
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>

Decode AT_PAGESZ to determine physPageSize on dragonfly.

Change-Id: I7236d7cbe43433f16dffddad19c1655bc0c7f31d
Reviewed-on: https://go-review.googlesource.com/103257
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

The escape_because.go test file (which tests the "because" escape
explainations printed by `-m -m`) cointains a machine-generated list
of all the escape reasons seen in the escape tests.

The list appears to be outdated; moreove a new escape reason was added
in CL 102895. This change re-generates the list.

Change-Id: Idc721c6bbfe9516895b5cf1e6d09b77deda5a3dd
Reviewed-on: https://go-review.googlesource.com/103375Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #23164

Change-Id: I6e8c6443f3ef91df71e117cce1cfa1faba647dd7
Reviewed-on: https://go-review.googlesource.com/87337Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

-race sets a hard cap of 8,192, which is easily hit while testing.

Fixes #23611

Change-Id: I0f720ec39c82c2194a485d437d6373f4bdc8a9c1
Reviewed-on: https://go-review.googlesource.com/103160Reviewed-by: Rob Pike <r@golang.org>

Change-Id: I7c0716711a2cadd347fdf242c792b109539f7355
Reviewed-on: https://go-review.googlesource.com/103163Reviewed-by: Andrew Bonventre <andybons@golang.org>

Change-Id: Idf88d289bac9603d852a9d19eb4b764f8589f8d9
Reviewed-on: https://go-review.googlesource.com/103159Reviewed-by: Andrew Bonventre <andybons@golang.org>

Fixes #23264

Change-Id: Ib6c343dc8e32949c6de72cb628cace2e8fabc302
Reviewed-on: https://go-review.googlesource.com/103236
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

In general use of these magic methods must be documented so that
users understand what will happen.

Fixes #23289

Change-Id: Ic46915eee1d3b7e57d8d1886834ddfb2e8e66e62
Reviewed-on: https://go-review.googlesource.com/103238Reviewed-by: Rob Pike <r@golang.org>

Change-Id: I8f12b188d2e13555e1d7634b9cc0319fc737cb1d
Reviewed-on: https://go-review.googlesource.com/103216Reviewed-by: Ian Lance Taylor <iant@golang.org>

Change-Id: Ibba5d4fd8124db9b1e4e50b8f37366f8dd23f47e
Reviewed-on: https://go-review.googlesource.com/103217Reviewed-by: Ian Lance Taylor <iant@golang.org>

A very small number of old browsers consider content as HTML
even when it is explicitly stated in the Content-Type header
that it is not. If content served is based on user-supplied
input, then an XSS is possible. Introduce three mitigations:

+ Don't reflect user input in error strings
+ Set a Content-Disposition header when requesting a resource
  that should never be displayed in a browser window
+ Set X-Content-Type-Options: nosniff on all responses

Change-Id: I81c9d6736e0439ebd1db99cd7fb701cc56d24805
Reviewed-on: https://go-review.googlesource.com/102318
Run-TryBot: Andrew Bonventre <andybons@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #24225

Change-Id: I876ac1b9d3615283f7b88cfa0b965ef81a57f056
Reviewed-on: https://go-review.googlesource.com/102955Reviewed-by: Rob Pike <r@golang.org>

When snapshotting the execution time stats of a goroutine
we take into account the intermediate values kepts in the GDesc's
gdesc field. At the end of goroutine analysis, we go through all
goroutines and replace the GExecutionStat with the new snapshot.
Here the mistake was that we replaced the GExecutionStat with
the value that reflects the intermediate values, but did clear
the intermediate values. So, when the following finalizeActiveSpans
runs, it trieds to add the intermediate values again (double-counting)
when taking a snapshot.

Fix the issue by using the finalized GExecutionStat instead of
recomputing the snapshot. While we are here, refactor the finalization
logic so it can be used when processing GoEnd, GoStop events.

Change-Id: Ibdb342214c29b65d4ea37e52b1f8b83f1fb20143
Reviewed-on: https://go-review.googlesource.com/103157Reviewed-by: Peter Weinberger <pjw@google.com>