This CL fixes two issues:

1. Load ops were initially always lowered to unsigned loads, even
   for signed types. This was fine by itself however LoadReg ops
   (used to re-load spilled values) were lowered to signed loads
   for signed types. This meant that spills could invalidate
   optimizations that assumed the original unsigned load.

2. Types were not always being maintained correctly through rules
   designed to eliminate unnecessary zero and sign extensions.

Updates #18906 and fixes #18958 (backport of CL 36256 to 1.8).

Change-Id: Id44953b0f644cad047e8474edbd24e8a344ca9a7
Reviewed-on: https://go-review.googlesource.com/36350Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #18845

Fixes #18870 (Go 1.8 backport)

Change-Id: Icdc3e2067807781e42f2ffc94d1824aed94d3713
Reviewed-on: https://go-review.googlesource.com/35956
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
(cherry picked from commit 7d8bfdde)
Reviewed-on: https://go-review.googlesource.com/36125

Change-Id: I82c41bd1d82adda457ddb5dd08caf0647905da22
Reviewed-on: https://go-review.googlesource.com/36091Reviewed-by: Matt Layher <mdlayher@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
(cherry picked from commit de479267)
Reviewed-on: https://go-review.googlesource.com/36130

After this, we will merge some of the dev work like
type aliases and inlining into master, so any additional
changes for the Go 1.8 release will need to be cherry-picked,
not merged.

3e55059f cmd/dist: really skip the testsanitizers tests on Android
09496599 runtime: add explicit (void) in C to avoid GCC 7 problem
4cffe2b6 cmd/dist: use the target GOOS to skip the test for issue 18153
6bdb0c11 doc: update go1.8 release notes after TxOptions change
09096bd3 cmd/go: update alldocs after CL 35150
96ea0918 cmd/compile: use CMPWU for 32-bit or smaller unsigned Geq on ppc64{,le}
21a8db1c doc: document go1.7.5

Change-Id: I9e6a30c3fac43d4d4d15e93054ac00964c3ee958

The test.bash script in misc/cgo/testsanitizers use GOOS, not GOHOSTOS.
Fix the dist check from gohostos to goos accordingly.

The error was masked on the builders because they run on a darwin host
where the sanitizers tests never ran.

With this change, the Android test suite completes successfully on
Android/amd64.

Change-Id: Id7690429f78c6ac7a26fc9118d913b719b565bb2
Reviewed-on: https://go-review.googlesource.com/35959Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

This avoids errors like
    ./traceback.go:80:2: call of non-function C.f1

I filed https://gcc.gnu.org/PR79289 for the GCC problem. I think this
is a bug in GCC, and it may be fixed before the final GCC 7 release.
This CL is correct either way.

Fixes #18855.

Change-Id: I0785a7b7c5b1d0ca87b454b5eca9079f390fcbd4
Reviewed-on: https://go-review.googlesource.com/35919
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

Fixes (skips) the test on Android, where stdout/stderr are not
terminals.

Updates #18153

Change-Id: Ieca65150362a5c423747ad751e00f76f0b890746
Reviewed-on: https://go-review.googlesource.com/35957
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Missed the release notes when updating the sql API.

Fixes #18825

Change-Id: I89056d46939ad4fc99590f3434d2881f5764e1b6
Reviewed-on: https://go-review.googlesource.com/35915Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Author of CL 35150 forgot to run mkalldocs.sh to update
the autogenerated alldocs.go

Change-Id: Ib824562db6044702456a221a8c6f9af412927a98
Reviewed-on: https://go-review.googlesource.com/35952Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #18808.

Change-Id: I49b266380b9d6804c9f6563ebac9c7c0e05f37f6
Reviewed-on: https://go-review.googlesource.com/35890
Run-TryBot: Michael Munday <munday@ca.ibm.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

Change-Id: Ie306bb5355f56113356fc141f3c1a56872b39f9e
Reviewed-on: https://go-review.googlesource.com/35836Reviewed-by: Chris Broadfoot <cbro@golang.org>

Change-Id: Ic8d4e971edebba9412f2e7c3d3c29f296c4977ff
Reviewed-on: https://go-review.googlesource.com/35833Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

78860b2a cmd/go: don't reject ./... matching top-level file outside GOPATH
2b283ced database/sql: fix race when canceling queries immediately
1cf08182 go/printer: fix format with leading comments in composite literal
b531eb30 runtime: reorder modules so main.main comes first
165cfbc4 database/sql: let tests wait for db pool to come to expected state
ea736493 doc: update gccgo docs
1db16711 doc: clarify what to do with Go 1.4 when installing from source
3717b429 doc: note that plugins are not fully baked
98842cab net/http: don't send body on redirects for 301, 302, 303 when GetBody is set
314180e7 net/http: fix a nit
aad06da2 cmd/link: mark DWARF function symbols as reachable
be9dcfec doc: mention testing.MainStart signature change
a96e117a runtime: amd64, use 4-byte ops for memmove of 4 bytes
4cce27a3 cmd/compile: fix constant propagation through s390x MOVDNE instructions
1be957d7 misc/cgo/test: pass current environment to syscall.Exec
ec654e22 misc/cgo/test: fix test when using GCC 7
256a605f cmd/compile: don't use nilcheck information until the next block
e8d5989e cmd/compile: fix compilebench -alloc
ea7d9e6a runtime: check for nil g and m in msanread

Change-Id: I61d508d4f0efe4b72e7396645c8ad6088d2bfa6e

This unwinds a small part of CL 31668: we now accept "./." in cleanImport.

Fixes #18778.

Change-Id: Ia7f1fde1cafcea3cc9e0b597a95a0e0bb410a3ed
Reviewed-on: https://go-review.googlesource.com/35646
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

Previously the following could happen, though in practice it would
be rare.

Goroutine 1:
	(*Tx).QueryContext begins a query, passing in userContext

Goroutine 2:
	(*Tx).awaitDone starts to wait on the context derived from the passed in context

Goroutine 1:
	(*Tx).grabConn returns a valid (*driverConn)
	The (*driverConn) passes to (*DB).queryConn

Goroutine 3:
	userContext is canceled

Goroutine 2:
	(*Tx).awaitDone unblocks and calls (*Tx).rollback
	(*driverConn).finalClose obtains dc.Mutex
	(*driverConn).finalClose sets dc.ci = nil

Goroutine 1:
	(*DB).queryConn obtains dc.Mutex in withLock
	ctxDriverPrepare accepts dc.ci which is now nil
	ctxCriverPrepare panics on the nil ci

The fix for this is to guard the Tx methods with a RWLock
holding it exclusivly when closing the Tx and holding a read lock
when executing a query.

Fixes #18719

Change-Id: I37aa02c37083c9793dabd28f7f934a1c5cbc05ea
Reviewed-on: https://go-review.googlesource.com/35550
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

This fix is less pervasive than it seems. The only change affecting
formatting is on printer.go:760. The remaining changes have no effect
on formatting since the value of p.level is ignored except on this
specific line.

The remaining changes are:
- renamed adjBlock to funcBody since that's how it is used
- introduced new printer field 'level' tracking the composite
  literal nesting level
- update/restore the composite literal nesting level as needed

Fixes #18782.

Change-Id: Ie833a9b5a559c4ec0f2eef2c5dc97aa263dca53a
Reviewed-on: https://go-review.googlesource.com/35811Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Modules appear in the moduledata linked list in the order they are
loaded by the dynamic loader, with one exception: the
firstmoduledata itself the module that contains the runtime.
This is not always the first module (when using -buildmode=shared,
it is typically libstd.so, the second module).

The order matters for typelinksinit, so we swap the first module
with whatever module contains the main function.

Updates #18729

This fixes the test case extracted with -linkshared, and now

	go test -linkshared encoding/...

passes. However the original issue about a plugin failure is not
yet fixed.

Change-Id: I9f399ecc3518e22e6b0a350358e90b0baa44ac96
Reviewed-on: https://go-review.googlesource.com/35644
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Slower builders were failing TestQueryContext because the cancel
and return to conn pool happens async. TestQueryContext already
uses a wait method for this reason. Use the same method for
other context tests.

Fixes #18759

Change-Id: I84cce697392b867e4ebdfadd38027a06ca14655f
Reviewed-on: https://go-review.googlesource.com/35750Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Update docs on correspondence between Go releases and GCC releases.

Update C type that corresponds to Go type `int`.

Drop out of date comments about Ubuntu and RTEMS.

Change-Id: Ic1b5ce9f242789af23ec3b7e7a64c9d257d6913e
Reviewed-on: https://go-review.googlesource.com/35631
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

You have to actually run make.bash (or make.bat).

Update #18771.

Change-Id: Ie6672a4e4abde0150c1ae57cabb1222de2c78716
Reviewed-on: https://go-review.googlesource.com/35632Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: I6341b8cce0b4a9922928f73f8b459cbb9ec25e79
Reviewed-on: https://go-review.googlesource.com/35571Reviewed-by: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>

The presence of Request.GetBody being set on a request was causing all
redirected requests to have a body, even if the redirect status didn't
warrant one.

This bug came from 307/308 support (https://golang.org/cl/29852) which
removed the line that set req.Body to nil after POST/PUT redirects.

Change-Id: I2a4dd5320f810ae25cfd8ea8ca7c9700e5dbd369
Reviewed-on: https://go-review.googlesource.com/35633
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>

Change-Id: I31fa5f906ad2e8dc475dbbeb91f568f91e16861b
Reviewed-on: https://go-review.googlesource.com/35514
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Otherwise we don't emit any required ELF relocations when doing an
external link, because elfrelocsect skips unreachable symbols.

Fixes #18745.

Change-Id: Ia3583c41bb6c5ebb7579abd26ed8689370311cd6
Reviewed-on: https://go-review.googlesource.com/35590
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

Fixes #18766

Change-Id: Ic0f72f3b7bbccd0546692993c4ed414f8c88c1c6
Reviewed-on: https://go-review.googlesource.com/35573Reviewed-by: Russ Cox <rsc@golang.org>

memmove used to use 2 2-byte load/store pairs to move 4 bytes.
When the result is loaded with a single 4-byte load, it caused
a store to load fowarding stall.  To avoid the stall,
special case memmove to use 4 byte ops for the 4 byte copy case.

We already have a special case for 8-byte copies.
386 already specializes 4-byte copies.
I'll do 2-byte copies also, but not for 1.8.

benchmark                 old ns/op     new ns/op     delta
BenchmarkIssue18740-8     7567          4799          -36.58%

3-byte copies get a bit slower.  Other copies are unchanged.
name         old time/op   new time/op   delta
Memmove/3-8   4.76ns ± 5%   5.26ns ± 3%  +10.50%  (p=0.000 n=10+10)

Fixes #18740

Change-Id: Iec82cbac0ecfee80fa3c8fc83828f9a1819c3c74
Reviewed-on: https://go-review.googlesource.com/35567
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

The constant propagation rules selected the wrong operand to
propagate. So MOVDNE (move if not equal) propagated operands as if
it were a MOVDEQ (move if equal).

Fixes #18735.

Change-Id: I87ac469172f9df7d5aabaf7106e2936ce54ae202
Reviewed-on: https://go-review.googlesource.com/35498
Run-TryBot: Michael Munday <munday@ca.ibm.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

This is needed for typical tests with gccgo, as it passes the
LD_LIBRARY_PATH environment variable to the new program.

Change-Id: I9bf4b0dbdff63f5449c7fcb8124eaeab10ed7f34
Reviewed-on: https://go-review.googlesource.com/35481
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

With GCC 7 (not yet released), cgo fails with errors like

./sigaltstack.go:65:8: call of non-function C.restoreSignalStack

I do not know precisely why. Explicitly declaring that there are no
arguments to the static function is a simple fix for the debug info.

Change-Id: Id96e1cb1e55ee37a9f1f5ad243d7ee33e71584ac
Reviewed-on: https://go-review.googlesource.com/35480
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

When nilcheck runs, the values in a block are not in any particular
order.  So any facts derived from examining the blocks shouldn't be
used until we reach the next block.

This is suboptimal as it won't eliminate nil checks within a block.
But it's probably a better fix for now as it is a much smaller change
than other strategies for fixing this bug.

nilptr3.go changes are mostly because for this pattern:
  _ = *p
  _ = *p
either nil check is fine to keep, and this CL changes which one
the compiler tends to keep.
There are a few regressions from code like this:
  _ = *p
  f()
  _ = *p
For this pattern, after this CL we issue 2 nil checks instead of one.
(For the curious, this happens because intra-block nil check
 elimination now falls to CSE, not nilcheck proper.  The former
 pattern has two nil checks with the same store argument.  The latter
 pattern has two nil checks with different store arguments.)

Fixes #18725

Change-Id: I3721b494c8bc9ba1142dc5c4361ea55c66920ac8
Reviewed-on: https://go-review.googlesource.com/35485Reviewed-by: Cherry Zhang <cherryyz@google.com>

pprof.WriteHeapProfile is shorthand for
pprof.Lookup("heap").WriteTo(f, 0).
The second parameter is debug.
If it is non-zero, pprof writes legacy-format
pprof output, which compilebench can parse.

Fixes #18641

Change-Id: Ica69adeb9809e9b5933aed943dcf4a07910e43fc
Reviewed-on: https://go-review.googlesource.com/35484
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

fixes #18707.

Change-Id: Ibc4efef01197799f66d10bfead22faf8ac00473c
Reviewed-on: https://go-review.googlesource.com/35452
Run-TryBot: Bryan Mills <bcmills@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Change-Id: Ifcf2e13b962aa10280df8ca76cb21b37e3533f8f
Reviewed-on: https://go-review.googlesource.com/35475
Run-TryBot: Chris Broadfoot <cbro@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

6593d865 go/ast: fix Object's doc comment about Data
c1730ae4 runtime: force workers out before checking mark roots
d10eddcb testing: make parallel t.Run safe again
2c8b70ea crypto/x509: revert SystemCertPool implementation for Windows
fcfd9185 doc/go1.8: document Plan 9 requirements
81a61a96 runtime: for plugins, don't add duplicate itabs
f674537c README.md: update and simplify
d8711919 cmd/go: fix bug help message
48d8edb5 crypto/tls: disable CBC cipher suites with SHA-256 by default
92ecd789 cmd/compile: add ZeroWB case in writebarrier
787125ab doc: 2017 is the Year of the Gopher
5b708a6b cmd/compile: lvalues are only required for == when calling runtime fns
e83d5067 vendor/golang_org/x/crypto/poly1305: revendor to pick up fix for #18673
76f981c8 net/http: skip TestServerHijackGetsBackgroundByte on Plan 9
e395e324 net/http: skip TestServerHijackGetsBackgroundByte_big on Plan 9
6a3c6c0d net/http: add another hijack-after-background-read test
467109bf all: test adjustments for the iOS builder
b2a3b54b net/http: make sure Hijack's bufio.Reader includes pre-read background byte
593ea3b3 cmd/go, misc: rework cwd handling for iOS tests
0642b8a2 syscall: export Fsid.X__val on s390x
4601eae6 doc/gdb: mention GOTRACEBACK=crash
4c4c5fc7 misc/cgo/testplugin: test that types and itabs are unique
22689c44 reflect: keep makeFuncImpl live across makeFuncStub
9cf06ed6 cmd/link: only exclude C-only symbols on darwin
9c3630f5 compress/flate: avoid large stack growth in fillDeflate
4f0aac52 cmd/go: add comment about SIGUSR2 on iOS
333f764d cmd/go, misc: switch from breakpoint to SIGUSR2
39e31d5e doc/go1.8: update timezone database version
08da8201 misc/cgo/testshared: test that types and itabs are unique
fdde7ba2 runtime: avoid clobbering C callee-save register in cgoSigtramp
f65abf6d cmd/compile: hide testdclstack behind debug flag
641ef2a7 compress/gzip: skip TestGZIPFilesHaveZeroMTimes on non-builders
0724aa81 crypto/dsa: gofmt
ac055429 net/http: deflake TestRetryIdempotentRequestsOnError
b842c9aa doc: remove inline styles

Change-Id: I642c056732fe1e8081e9d73e086e38ea0b2568cc

The doc comment about the Data field of go/ast.Object reflects its old
behavior, from when the go/types typechecker depended on ast.Objects.

Since when the doc was written, the behavior has changed in
https://golang.org/cl/7058060 and https://golang.org/cl/7096048 .

Fixes #18631

Change-Id: I10fc3e31cfbf7b303eec44150df917f6eb285f90
Reviewed-on: https://go-review.googlesource.com/35075Reviewed-by: Robert Griesemer <gri@golang.org>

Currently we check that all roots are marked as soon as gcMarkDone
decides to transition from mark 1 to mark 2. However, issue #16083
indicates that there may be a race where we try to complete mark 1
while a worker is still scanning a stack, causing the root mark check
to fail.

We don't yet understand this race, but as a simple mitigation, move
the root check to after gcMarkDone performs a ragged barrier, which
will force any remaining workers to finish their current job.

Updates #16083. This may "fix" it, but it would be better to
understand and fix the underlying race.

Change-Id: I1af9ce67bd87ade7bc2a067295d79c28cd11abd2
Reviewed-on: https://go-review.googlesource.com/35353
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>

Fixes #18603.

Change-Id: I5760c0a9f862200b7e943058a672eb559ac1b9d9
Reviewed-on: https://go-review.googlesource.com/35354
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Updates #18609

Change-Id: I8306135660f52cf625bed4c7f53f632e527617de
Reviewed-on: https://go-review.googlesource.com/35265
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Quentin Smith <quentin@golang.org>

Fixes #18610.

Change-Id: I19da4d59a1b6293c9a4722aa696e2cb58d982a15
Reviewed-on: https://go-review.googlesource.com/35333Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

We already do this for shared libraries. Do it for plugins also.
Suggestions on how to test this would be welcome.

I'd like to get this in for 1.8.  It could lead to mysterious
hangs when using plugins.

Fixes #18676

Change-Id: I03209b096149090b9ba171c834c5e59087ed0f92
Reviewed-on: https://go-review.googlesource.com/35117Reviewed-by: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>