Semi-regular merge from tip to dev.ssa.

Two fixes:
1) Mark selectgo as not returning.  This caused problems
   because there are no VARKILL ops on the selectgo path,
   causing things to be marked live that shouldn't be.
2) Tell the amd64 assembler that addressing modes like
   name(SP)(AX*4) are ok.

Change-Id: I9ca81c76391b1a65cc47edc8610c70ff1a621913

A first pass to decompose user types (structs, maybe
arrays someday), and a second pass to decompose builtin
types (strings, interfaces, slices, complex).  David wants
this for value range analysis so he can have structs decomposed
but slices and friends will still be intact and he can deduce
things like the length of a slice is >= 0.

Change-Id: Ia2300d07663329b51ed6270cfed21d31980daa7c
Reviewed-on: https://go-review.googlesource.com/19340
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: David Chase <drchase@google.com>

Adds a test to detect the bug that slipped in earlier when partioning
by the Aux value, but not sorting by it.

Change-Id: I56d0ba76383bbc1514b3dabd295e369771c26645
Reviewed-on: https://go-review.googlesource.com/19382
Run-TryBot: Todd Neal <todd@tneal.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

ListenAndServeTLS doesn't require cert and key file names if the
server's TLSConfig has a cert configured. This code was never updated
when the GetCertificate hook was added to *tls.Config, however.

Fixes #14268

Change-Id: Ib282ebb05697edd37ed8ff105972cbd1176d900b
Reviewed-on: https://go-review.googlesource.com/19381Reviewed-by: Russ Cox <rsc@golang.org>

Fixes #14262.

Change-Id: Id590995dd4460e81f6b91bcfb3f02515a97650fe
Reviewed-on: https://go-review.googlesource.com/19361
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #14259

Change-Id: I23fedec0eb85ae28e56bc24539bc864674856130
Reviewed-on: https://go-review.googlesource.com/19318Reviewed-by: Ian Lance Taylor <iant@golang.org>

INC/DEC produces slightly faster and smaller code.

Change-Id: I329d9bdb01b90041be45e053d9df640818bf0c2d
Reviewed-on: https://go-review.googlesource.com/19238
Run-TryBot: Ilya Tocar <ilya.tocar@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

Change-Id: Id51e5c97e9653b764b809bf3424f1a6d31b6ffea
Reviewed-on: https://go-review.googlesource.com/19338
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: David Chase <drchase@google.com>

Problem was caused by use of Args[].Aux differences
in early partitioning.  This artificially separated
two equivalent expressions because sort ignores the
Aux field, hence things can end with equal things
separated by unequal things and thus the equal things
are split into more than one partition.  For example:
SliceLen(a), SliceLen(b), SliceLen(a).

Fix: don't use Args[].Aux in initial partitioning.

Left in a debugging flag and some debugging Fprintf's;
not sure if that is house style or not.  We'll probably
want to be more systematic in our naming conventions,
e.g. ssa.cse, ssa.scc, etc.

Change-Id: Ib1412539cc30d91ea542c0ac7b2f9b504108ca7f
Reviewed-on: https://go-review.googlesource.com/19316Reviewed-by: Keith Randall <khr@golang.org>

The operation where this manifested in a crash was % (only defined on integers).
However, the existing code was sloppy in that it didn't retain the integer form
after a value (e.g., 3.0) was accepted as representable in integer form (3 for
the example). We would have seen a crash in such cases for / as well except
that there was code to fix it for just that case.

Remove the special code for / and fix more generally by retaining the integer
form for all operations if applicable.

Fixes #14229.

Change-Id: I8bef769e6299839fade27c6e8b5ff29ad6521d0d
Reviewed-on: https://go-review.googlesource.com/19300Reviewed-by: Alan Donovan <adonovan@google.com>

Examine both Aux and AuxInt to form more precise initial partitions.
Restructure loop to avoid repeated type.Equal() call.  Speeds up
compilation of testdata/gen/arithConst_ssa by 25%.

Change-Id: I3cfb1d254adf0601ee69239e1885b0cf2a23575b
Reviewed-on: https://go-review.googlesource.com/19313
Run-TryBot: Todd Neal <todd@tneal.org>
Reviewed-by: Keith Randall <khr@golang.org>

Panic doesn't return, so record that we immediately exit after a panic
call.  This will help code analysis.

Change-Id: I4d1f67494f97b6aee130c43ff4e44307b2b0f149
Reviewed-on: https://go-review.googlesource.com/19303
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>

Change-Id: I630d4d2d8a914d6c07f22351a56d5e44a937123e
Reviewed-on: https://go-review.googlesource.com/19245Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The test sends two HTTP/1.1 pipelined requests.  The first is
completedly by the second, and as such triggers an immediate call to the
CloseNotify channel.  The second calls the CloseNotify channel after the
overall connection is closed.

The test was passing fine on gc because the code would enter the select
loop before running the handler, so the send on gotReq would always be
seen first.  On gccgo the code would sometimes enter the select loop
after the handler had already finished, meaning that the select could
choose between gotReq and sawClose.  If it picked sawClose, it would
never close the overall connection, and the httptest server would hang.
The same hang could be induced with gc by adding a time.Sleep
immediately before the select loop.

Deflake the test by 1) don't close the overall connection until both
requests have been seen; 2) don't exit the loop until both closes have
been seen.

Fixes #14231.

Change-Id: I9d20c309125422ce60ac545f78bcfa337aec1c7d
Reviewed-on: https://go-review.googlesource.com/19281Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

The frontend does this for 32 bits and below, but SSA needs
to do it for 64 bits.  The algorithms are all copied from
cgen.go:cgen_div.

Speeds up TimeFormat substantially: ~40% slower to ~10% slower.

Change-Id: I023ea2eb6040df98ccd9105e15ca6ea695610a7a
Reviewed-on: https://go-review.googlesource.com/19302
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Todd Neal <todd@tneal.org>

Change-Id: I93201fa4152f2d60b3eedb8d321a152819033121
Reviewed-on: https://go-review.googlesource.com/19270Reviewed-by: Ian Lance Taylor <iant@golang.org>

Use just a single write barrier flag test, even if there
are multiple pointer fields in a struct.

This helps move more of the wb-specific code (like the LEA
needed to materialize the write address) into the unlikely path.

Change-Id: Ic7a67145904369c4ff031e464d51267d71281c8f
Reviewed-on: https://go-review.googlesource.com/19085
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

Updates x/net/http2 to git rev 493a262 for https://golang.org/cl/19223

Fixes #14227

Change-Id: I626122811138fb3d88e4eea83f8da3fdcf91e0dc
Reviewed-on: https://go-review.googlesource.com/19250Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Change-Id: Ifb8eba1929c79ee7a8cae2191613c55a3b8f74e5
Reviewed-on: https://go-review.googlesource.com/19236Reviewed-by: Todd Neal <todd@tneal.org>

Updates #14227

Change-Id: If39f11471ecd307c9483f64e73f9c89fe906ae71
Reviewed-on: https://go-review.googlesource.com/19222Reviewed-by: Andrew Gerrand <adg@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

If the output register is one of the input registers,
we can use a real add instead of LEA.

Change-Id: Ide58f1536afb077c0b939d3a8c7555807fd1c5e3
Reviewed-on: https://go-review.googlesource.com/19234Reviewed-by: Alexandru Moșoi <alexandru@mosoi.ro>

When using a stack-allocated buffer for the result, don't
expose the uninitialized portion of it by restricting its
capacity to its length.

The other option is to zero the portion between len and cap.
That seems like more work, but might be worth it if the caller
then appends some stuff to the result.  But this close to 1.6,
I'm inclined to do the simplest fix possible.

Fixes #14232

Change-Id: I21c50d3cda02fd2df4d60ba5e2cfe2efe272f333
Reviewed-on: https://go-review.googlesource.com/19231Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

The plan9.bell-labs.com site has fallen into disrepair.
We'll instead use the site maintained by contributor David du Colombier.

Fixes #14233

Change-Id: I0c702e5d3b091cccd42b288ea32f34d507a4733d
Reviewed-on: https://go-review.googlesource.com/19240Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: David du Colombier <0intro@gmail.com>

* Enclose each rule's code in a for with no condition
* The loop is ran at most once because it's always terminated by a return.
* Use break when matching condition fails
* Drop rule hashes
* Shaves about 3 lines of code per rule

The binary size is not afected.

Change-Id: I27c3e40dc8cae98dcd50739342dc38db2ef9c247
Reviewed-on: https://go-review.googlesource.com/19220Reviewed-by: Keith Randall <khr@golang.org>

Mostly indexed loads.  A few more LEA cases.

Change-Id: Idc1d447ed0dd6e906cd48e70307a95e77f61cf5f
Reviewed-on: https://go-review.googlesource.com/19172Reviewed-by: Todd Neal <todd@tneal.org>
Run-TryBot: Keith Randall <khr@golang.org>

LEAQ symbol+100(SB), AX

Under dynamic link, rewrites to

MOVQ symbol@GOT(SB), AX
ADDQ $100, AX

but ADDQ clobbers flags, whereas the original LEAQ (when not dynamic
linking) doesn't.

Use LEAQ instead of ADDQ to add that constant in so we preserve flags.

Change-Id: Ibb055403d94a4c5163e1c7d2f45da633ffd0b6a3
Reviewed-on: https://go-review.googlesource.com/19230Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Shaves about 3 lines per generated rule.

Change-Id: I94adc94ab79f90ac5fd033f896ece3b1eddf0f3d
Reviewed-on: https://go-review.googlesource.com/19197Reviewed-by: Keith Randall <khr@golang.org>

Add rewrite rules to optimize constant shifts.

Fixes #10637

Change-Id: I74b724d3e81aeb7098c696d02c050f7fdfd5b523
Reviewed-on: https://go-review.googlesource.com/19106Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Todd Neal <todd@tneal.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Removes approx. one assignment per rule.

Change-Id: Ie9f0a7082ae12c4447ff6b4d40678cd92bdbb6f2
Reviewed-on: https://go-review.googlesource.com/19194Reviewed-by: Keith Randall <khr@golang.org>

* Simplify comparisons of form a + const1 == const2 or a + const1 != const2.
* Canonicalize Eq, Neq, Add, Sub to have a constant as first argument.
Needed for the above new rules and helps constant folding.

Change-Id: I8078702a5daa706da57106073a3e9f640a67f486
Reviewed-on: https://go-review.googlesource.com/19192Reviewed-by: Keith Randall <khr@golang.org>

Modify the simple domCheck to use the sparse tree code.  This
speeds up compilation of one of the generated test cases from
1m48s to 17s.

Change-Id: If577410ee77b54918147a66917a8e3721297ee0a
Reviewed-on: https://go-review.googlesource.com/19187
Run-TryBot: Todd Neal <todd@tneal.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Update #14063.

Change-Id: Id13456deb15c90a8af282b77d78ff5cdbd1de8bf
Reviewed-on: https://go-review.googlesource.com/19208
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #14219.

Change-Id: Id398dcfe6e9978d7eefddcdaaaa2256c16237cf3
Reviewed-on: https://go-review.googlesource.com/19207
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>

Change-Id: I1738e3af7de0972c54d74325d80781059d0796d8
Reviewed-on: https://go-review.googlesource.com/19186
Run-TryBot: Todd Neal <todd@tneal.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

libcurl sends this (despite never being standardized), and the Google
GFE rejects it with a 400 bad request (but only when over http2?).

So nuke it.

Change-Id: I3fc95523d50f33a0e23bb26b9195f70ab0aed0f4
Reviewed-on: https://go-review.googlesource.com/19184Reviewed-by: Chris Broadfoot <cbro@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>

Previous flakes:
https://build.golang.org/log/223365dedb6b6aa0cfdf5afd0a50fd433a16bade
https://build.golang.org/log/edbea4cd3f24e707ef2ae8378559bb0fcc453c22

Dmitry says in email about this:

> The stack trace points to it pretty clearly. Done can indeed unblock
> Wait first and then panic. I guess we need to recover after first
> Done as well.

And it looks like TestWaitGroupMisuse2 was already hardened against
this.  Do the same in TestWaitGroupMisuse3.

Change-Id: I317800c7e46f13c97873f0873c759a489dd5f47d
Reviewed-on: https://go-review.googlesource.com/19183Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

The loading of zversion.go was expecting it to be in
package runtime, but it moved to runtime/internal/sys.
Worse, the load was not checking the error.

Update the path, check the error, add a test.

Fixes #14176.

Change-Id: I203c40afe1448875581415d5e42c29f09b14545d
Reviewed-on: https://go-review.googlesource.com/19180
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #14201.

Change-Id: Ib61f8c00cae72463f59b90ae199fbdc1e7422a79
Reviewed-on: https://go-review.googlesource.com/19174
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

Fixes #14202

Change-Id: Ia6dccecb1b9b3f6c0838c99090e6ddf1ad43303c
Reviewed-on: https://go-review.googlesource.com/19175
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

Fixes #14171.

Change-Id: Ie75c1cfd88801618308d472bc04e7fc648c95e0c
Reviewed-on: https://go-review.googlesource.com/19150Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>