This change adds support for VDSO on ppc64x, making it possible to
avoid a syscall in walltime and nanotime.

BenchmarkClockVDSOAndFallbackPaths/vDSO-192             20000000    66.0 ns/op
BenchmarkClockVDSOAndFallbackPaths/Fallback-192          1000000    1456 ns/op

Change-Id: I3373bd804b6f122961de3ae9d034e6ccf35748e6
Reviewed-on: https://go-review.googlesource.com/131135
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>

Some versions of Windows (Windows 10 1803) do not set file
position after TransmitFile completes. So just use Seek
to set file position before returning from sendfile.

Fixes #25722

Change-Id: I7a49be10304b5db19dda707b13ac93d338aeb190
Reviewed-on: https://go-review.googlesource.com/131976Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Yasuhiro MATSUMOTO <mattn.jp@gmail.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fence-post implications of the form "x-1 >= w && x > min ⇒ x > w"
were not correctly handling unsigned domain, by always checking signed
limits.

This bug was uncovered once we taught prove that len(x) is always
>= 0 in the signed domain.

In the code being miscompiled (s[len(s)-1]), prove checks
whether len(s)-1 >= len(s) in the unsigned domain; if it proves
that this is always false, it can remove the bound check.

Notice that len(s)-1 >= len(s) can be true for len(s) = 0 because
of the wrap-around, so this is something prove should not be
able to deduce.

But because of the bug, the gate condition for the fence-post
implication was len(s) > MinInt64 instead of len(s) > 0; that
condition would be good in the signed domain but not in the
unsigned domain. And since in CL105635 we taught prove that
len(s) >= 0, the condition incorrectly triggered
(len(s) >= 0 > MinInt64) and things were going downfall.

Fixes #27251
Fixes #27289

Change-Id: I3dbcb1955ac5a66a0dcbee500f41e8d219409be5
Reviewed-on: https://go-review.googlesource.com/132495Reviewed-by: Keith Randall <khr@golang.org>

Short variable declarations example passes an fd argument to os.Pipe call.
However, os.Pipe() takes no arguments and returns 2 Files and an error:
https://golang.org/src/os/pipe_linux.go?s=319:360#L1

Fixes: #27384

Change-Id: I0a709f51e0878c57185d901b899d209f001dfcce
Reviewed-on: https://go-review.googlesource.com/132284Reviewed-by: Robert Griesemer <gri@golang.org>

Change-Id: I0fcb5e626bf3d6891592c21b912c824743d7eaa0
Reviewed-on: https://go-review.googlesource.com/132280Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

The benchstat tool computes statistics about benchmarks, including
whether any differences are statistically significant. Recommend its use
in commit messages of performance-related changes rather than the
simpler benchcmp tool.

Change-Id: I4b35c2d892b48e60c3064489b035774792c19c30
Reviewed-on: https://go-review.googlesource.com/132515Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: I0dd843ac06f1b9987aa2fc90ae62074e668d6d4d
Reviewed-on: https://go-review.googlesource.com/132438Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: Ifd509c0c6a6ea41094b6ae1f4931414325b152fd
Reviewed-on: https://go-review.googlesource.com/132475
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Internal helper functions for type-checking type expressions were
renamed to make it clearer when they should be used:

	typExpr (w/o def) -> typ
	typExpr (w/  def) -> definedType
	typ               -> indirectType
	typExprInternal   -> typInternal

The rename emphasizes that in most cases Checker.typ should be used
to compute the types.Type from an ast.Type. If the type is defined,
definedType should be used. For composite type elements which are
not "inlined" in memory, indirectType should be used.

In the process, implicitly changed several uses of indirectType
(old: typ) to typ (old: typExpr) by not changing the respective
function call source. These implicit changes are ok in those
places because either call is fine where we are not concerned
about composite type elements. But using typ (old: typExpr) is
more efficient than using indirectType (old: typ).

Change-Id: I4ad14d5357c5f94b6f1c33173de575c4cd05c703
Reviewed-on: https://go-review.googlesource.com/130595Reviewed-by: Alan Donovan <adonovan@google.com>

Now that most of the type-checker is using the object-coloring mechanism
to detect cycles, remove the explicit path parameter from the functions
that don't rely on it anymore.

Some of the syntactic-based resolver code (for aliases, interfaces)
still use an explicit path; leaving those unchanged for now.

The function cycle was moved from typexpr.go (where it is not used
anymore) to resolver.go (where it's still used). It has not changed.

Fixes #25773.

Change-Id: I2100adc8d66d5da9de9277dee94a1f08e5a88487
Reviewed-on: https://go-review.googlesource.com/130476Reviewed-by: Alan Donovan <adonovan@google.com>

For Go 1.11, cycle tracking of global (package-level) objects was changed
to use a Checker-level object path rather than relying on the explicit
path parameter that is passed around to some (but not all) type-checker
functions.

This change now uses the same mechanism for the detection of local
type cycles (local non-type objects cannot create cycles by definition
of the spec).

As a result, local alias cycles are now correctly detected as well
(issue #27106).

The path parameter that is explicitly passed around to some type-checker
methods is still present and will be removed in a follow-up CL.

Also:
- removed useCycleMarking flag and respective dead code
- added a couple more tests
- improved documentation

Fixes #27106.
Updates #25773.

Change-Id: I7cbf304bceb43a8d52e6483dcd0fa9ef7e1ea71c
Reviewed-on: https://go-review.googlesource.com/130455
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>

Previously, pattern matching was good enough to achieve good performance
for the RotateLeft* functions, but the inlining cost for them was much
too high. Make RotateLeft* intrinsic on amd64 as a stop-gap for now to
reduce inlining costs.

This should be done (or at least looked at) for other architectures
as well.

Updates golang/go#17566

Change-Id: I6a106ff00b6c4e3f490650af3e083ed2be00c819
Reviewed-on: https://go-review.googlesource.com/132435
Run-TryBot: Andrew Bonventre <andybons@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

The sentence in the docs for SystemCertPool that states that mutations
to a returned pool do not affect any other pool is ambiguous as to who
the any other pools are, because pools can be created in multiple ways
that have nothing to do with the system certificate pool. Also the use
of the word 'the' instead of 'a' early in the sentence implies there is
only one shared pool ever returned.

Fixes #27385

Change-Id: I43adbfca26fdd66c4adbf06eb85361139a1dea93
GitHub-Last-Rev: 2f1ba09fa403d31d2d543dca15727c6c2f896ec7
GitHub-Pull-Request: golang/go#27388
Reviewed-on: https://go-review.googlesource.com/132378Reviewed-by: Filippo Valsorda <filippo@golang.org>

"someting" is misspelled and the error handling both clobbers the
error that occurs and distracts from the point of the example, which
is to demonstrate how Printf works. It's better to just panic with the
error.

Change-Id: I5fb0a4a1a8b4772cbe0302582fa878d95e3a4060
Reviewed-on: https://go-review.googlesource.com/132376Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Instead of calling run synchronously, we pass it through bgrun
and immediately wait for it to finish. This pushes all jobs
to execute through the bgwork channel and therefore causes
them to exit cleanly in case of a compiler error.

Fixes #25981

Change-Id: I789a85d23fabf32d144ab85a3c9f53546cb7765a
Reviewed-on: https://go-review.googlesource.com/127776
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

The type-checker currently crashes when checking code such as:

	_ = map[string][...]int{"": {1, 2, 3}}

In this case, the type checker reports an error for map[string][...]int,
then proceeds to type-check the values of the map literal using a hint
type of [...]int. When type-checking the inner composite (array) literal,
the length of the open array type is computed from the elements,
then the array type is recorded, but the literal has no explicit type
syntax against which to record the type, so this code causes the
type-checker to panic. Add a nil check before calling
check.recordTypeAndValue to avoid that.

Updates #22467

Change-Id: Ic4453ba485b7b88ede2a89f209365eda9e032abc
Reviewed-on: https://go-review.googlesource.com/132355Reviewed-by: Alan Donovan <adonovan@google.com>

Refactor TestSplice/readerAtEOF to handle cases where we disable
splice on older kernels better.

If splice is disabled, net.splice and poll.Splice do not get to
observe EOF on the reader, because poll.Splice returns immediately
with EINVAL. The test fails unexpectedly, because the splice operation
is reported as not handled.

This change refactors the test to handle the aforementioned case
correctly, by not calling net.splice directly, but using a higher
level check.

Fixes #27355.

Change-Id: I0d5606b4775213f2dbbb84ef82ddfc3bab662a31
Reviewed-on: https://go-review.googlesource.com/132096
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: Idc4aa53e443b89eeba496d00f6b409268e29ec21
Reviewed-on: https://go-review.googlesource.com/132241
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The errors package has an example for Errorf, but the fmt
package does not. Copy the Errorf example from errors to
fmt. Move existing Stringer example into separate file, so as
not to break the assumption that the entire file will be
presented as the example.

Change-Id: I8a210a69362017fa08615a8c3feccdeee8427e22
Reviewed-on: https://go-review.googlesource.com/132239Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: I8e55e9397eb6844b5856f8bde9c26185c446a80e
Reviewed-on: https://go-review.googlesource.com/132238Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: I7ba55e3f6ebbaae41188316a66a40f994c037ad9
Reviewed-on: https://go-review.googlesource.com/132240
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: Ide50aba940727a7b32cd33dea5315050f1a34717
Reviewed-on: https://go-review.googlesource.com/132237
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: Id0e2fb2abad5b776ac0ed76e55e36c6b774b5b7a
Reviewed-on: https://go-review.googlesource.com/132278
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Signed-off-by: Venil Noronha <veniln@vmware.com>

Change-Id: Ie5f50bc31db1eee11582b70b0e25c726090d4037
Reviewed-on: https://go-review.googlesource.com/132236
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: I65c3bda498562fdf39994ec1cadce7947e2d84b5
Reviewed-on: https://go-review.googlesource.com/132277
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

runtime.wbBufFlush must not modify its arguments, because the
argument slots are also used as spill slots in runtime.gcWriteBarrier.
So, GOEXPERIMENT=clobberdead must not clobber them.

Updates #27326.

Change-Id: Id02bb22a45201eecee748d89e7bdb3df7e4940e4
Reviewed-on: https://go-review.googlesource.com/131957Reviewed-by: Keith Randall <khr@golang.org>

We now have safepoints at nearly all the instructions. When
GOEXPERIMENT=clobberdead is on, it inserts clobbers nearly at
every instruction. Currently this doesn't work. (Maybe the stack
maps at non-call safepoints are still imprecise. I haven't
investigated.) For now, only use call-based safepoints if the
experiment is on.

Updates #27326.

Change-Id: I72cda9b422d9637cc5738e681502035af7a5c02d
Reviewed-on: https://go-review.googlesource.com/131956Reviewed-by: Keith Randall <khr@golang.org>

The current implementation crashes when someone writes a panic outside of
a function, which makes sense since that is broken code. This fix allows
one to type-check broken code.

Updates #22467

Change-Id: I81b90dbd918162a20c60a821340898eaf02e648d
Reviewed-on: https://go-review.googlesource.com/132235Reviewed-by: Alan Donovan <adonovan@google.com>

Change-Id: Icded6c786b7b185d5aff055f34e0cfe9e521826a
Reviewed-on: https://go-review.googlesource.com/132176
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The sym.Symbol 'ElfType' field is used only for symbols corresponding
to things in imported shared libraries, hence is not needed in the
common case. Relocate it to sym.AuxSymbol so as to shrink the main
Symbol struct.

Updates #26186

Change-Id: I803efc561c31a0ca1d93eca434fda1c862a7b2c5
Reviewed-on: https://go-review.googlesource.com/125479Reviewed-by: Ian Lance Taylor <iant@golang.org>

The sym.Symbol 'Plt' and 'Got' field are used only with cgo and/or
external linking and are not needed for most symbols. Relocate them to
sym.AuxSymbol so as to shrink the main Symbol struct.

Updates #26186

Change-Id: I170d628a760be300a0c1f738f0998970e91ce3d6
Reviewed-on: https://go-review.googlesource.com/125478Reviewed-by: Ian Lance Taylor <iant@golang.org>

The sym.Symbol 'Localentry' field is used only with cgo and/or
external linking on MachoPPC. Relocate it to sym.AuxSymbol since it is
infrequently used, so as to shrink the main Symbol struct.

Updates #26186

Change-Id: I5872aa3f059270c2a091016d235a1a732695e411
Reviewed-on: https://go-review.googlesource.com/125477Reviewed-by: Ian Lance Taylor <iant@golang.org>

Create a new "AuxSymbol" struct into which 'cold' or 'infrequently
set' symbol fields are located. Move the Extname field from the
main Symbol struct to AuxSymbol.

Updates #26186

Change-Id: I9e795fb0cc48f978e2818475fa073ed9f2db202d
Reviewed-on: https://go-review.googlesource.com/125476Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

The 120->124 change in https://go-review.googlesource.com/c/go/+/61511/21/test/nosplit.go#143
looks accidental. Change back to 120.

Change-Id: I1690a8ae2d32756ba05544d2ed1baabfa64e1704
Reviewed-on: https://go-review.googlesource.com/131958
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The system call geteuid can not work properly on android, which
causes a test case failed on rooted android/arm.

This CL disables the test case on android.

Fixes #27364

Change-Id: Ibfd33ef8cc1dfe8822c8be4280eae12ee30929c1
Reviewed-on: https://go-review.googlesource.com/132175
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>

Fixes issue #27359

Change-Id: I048fbd88a08e8b17fcda3872ee4c78935d5075d8
GitHub-Last-Rev: a0751eca094d68e9bf005abeb6616eb5b0050190
GitHub-Pull-Request: golang/go#27359
Reviewed-on: https://go-review.googlesource.com/132117Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Nil check is special in that it has no use but we must keep it.
Count it as a use of the auto.

Fixes #27278.

Change-Id: I857c3d0db2ebdca1bc342b4993c0dac5c01e067f
Reviewed-on: https://go-review.googlesource.com/131955
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Fixes #26638.

Change-Id: I3c18d1298d99af8ea8c00916303efd2b5a5effc7
Reviewed-on: https://go-review.googlesource.com/126336Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

bytes.NewBuffer's documentation says it can be used to set the initial
size of the buffer. The current wording is:

> It can also be used to size the internal buffer for writing.

This may led users to believe that the buffer (its backing array) is
fixed in size and won't grow, which isn't true (subsequent Write calls
will expand the backing array as needed).

Change the doc to make it clearer that NewBuffer just sets the initial
size of the buffer.

Fixes #27242

Change-Id: I2a8cb5bee02ca2c1657ef59e2cf1434c7a9bd397
Reviewed-on: https://go-review.googlesource.com/132035Reviewed-by: Dominik Honnef <dominik@honnef.co>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

lexRawQuote already uses the next method, which keeps track of newlines
on a character by character basis. Adding up newlines in emit again
results in the newlines being counted twice, which can mean bad position
information in error messages.

Fix that, and add a test.

Fixes #27319.

Change-Id: Id803be065c541412dc808d388bc6d8a86a0de41e
Reviewed-on: https://go-review.googlesource.com/131996
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>