This CL presents the proposed user annotation API skeleton.
This CL bumps up the trace version to 1.11.

Design doc https://goo.gl/iqJfJ3

Implementation CLs are followed.

The API introduces three basic building blocks. Log, Span, and Task.

Log is for basic logging. When called, the message will be recorded
to the trace along with timestamp, goroutine id, and stack info.

   trace.Log(ctx, messageType message)

Span can be thought as an extension of log to record interesting
time interval during a goroutine's execution. A span is local to a
goroutine by definition.

   trace.WithSpan(ctx, "doVeryExpensiveOp", func(ctx context) {
      /* do something very expensive */
   })

Task is higher-level concept that aids tracing of complex operations
that encompass multiple goroutines or are asynchronous.
For example, an RPC request, a HTTP request, a file write, or a
batch job can be traced with a Task.

Note we chose to design the API around context.Context so it allows
easier integration with other tracing tools, often designed around
context.Context as well. Log and WithSpan APIs recognize the task
information embedded in the context and record it in the trace as
well. That allows the Go execution tracer to associate and group
the spans and log messages based on the task information.

In order to create a Task,

   ctx, end := trace.NewContext(ctx, "myTask")
   defer end()

The Go execution tracer measures the time between the task created
and the task ended for the task latency.

More discussion history in golang.org/cl/59572.

Update #16619

R=go1.11

Change-Id: I59a937048294dafd23a75cf1723c6db461b193cd
Reviewed-on: https://go-review.googlesource.com/63274Reviewed-by: Austin Clements <austin@google.com>

Updates #23834.

Change-Id: I92aca9108590a0c7de774f4fad7ded97105e3cb8
Reviewed-on: https://go-review.googlesource.com/94475Reviewed-by: Matthew Dempsky <mdempsky@google.com>

This change adds ADD/AND/OR/XOR Immediate Shifted instructions for
ppc64x so they are usable in Go asm code. These instructions were
originally present in asm9.go, but they were only usable in that
file (as -AADD, -AANDCC, -AOR, -AXOR). These old mnemonics are now
removed.

Updates #23845

Change-Id: Ifa2fac685e8bc628cb241dd446adfc3068181826
Reviewed-on: https://go-review.googlesource.com/94115Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>

Per the notice in the Go 1.10 release notes, this change drops the
support for Windows Vista or below (including Windows XP) and
simplifies the code for the sake of maintenance.

There is one exception to the above. The code related to DLL and
system calls still remains in the runtime package. The remaining code
will be refined and used for supporting upcoming Windows versions in
future.

Updates #17245
Fixes #23072

Change-Id: I9e2821721f25ef9b83dfbf85be2b7ee5d9023aa5
Reviewed-on: https://go-review.googlesource.com/94255
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

NetBSD supports the SOCK_CLOEXEC and SOCK_NONBLOCK flags to the socket
syscall since version 6.0. The same version also introduced the paccept
syscall which can be used to implement syscall.Accept4.

Follows CL 40895

Change-Id: I9e4e1829b0382744c7799f4e58929a53b4e193f7
Reviewed-on: https://go-review.googlesource.com/94295
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Benny Siegert <bsiegert@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The scanner assumed that ~ really meant ^, which may be helpful when
coming from C. But ~ is not a valid Go token, and pretending that it
should be ^ can lead to confusing error messages. Better to be upfront
about it and complain about the invalid character in the first place.

This was code "inherited" from the original yacc parser which was
derived from a C compiler. It's 10 years later and we can probably
assume that people are less confused about C and Go.

Fixes #23587.

Change-Id: I8d8f9b55b0dff009b75c1530d729bf9092c5aea6
Reviewed-on: https://go-review.googlesource.com/94160Reviewed-by: Matthew Dempsky <mdempsky@google.com>

Updating to commit 0e0e5b7254e076a62326ab7305ba49e8515f0c91
from github.com/google/pprof

Recent modifications to the vendored pprof, such as skipping
TestWebInterface to avoid starting a web browser, have all been fixed
upstream.

Change-Id: I72e11108c438e1573bf2f9216e76d157378e8d45
Reviewed-on: https://go-review.googlesource.com/93375
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Move the ELF32 and ELF64 structure definitions into their own files so
they can be reused when vDSO support is added for other architectures.

Change-Id: Id0171b4e5cea4add8635743c881e3bf3469597af
Reviewed-on: https://go-review.googlesource.com/93995
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

Remove a branch and a stack spill.

name                old time/op  new time/op  delta
StackCopy-8         79.2ms ± 1%  79.1ms ± 2%    ~     (p=0.063 n=96+95)
StackCopyNoCache-8   121ms ± 1%   120ms ± 2%  -0.46%  (p=0.000 n=97+88)

Change-Id: Ifcbbb05d773178fad84cb11a9a6768ace69fcf24
Reviewed-on: https://go-review.googlesource.com/94029
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Change-Id: I132d3627ae301b68bf87eacb5bf41fd1ba2dcd91
Reviewed-on: https://go-review.googlesource.com/94025
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: Ic1ce2f93d6a225699e9ce5307d62cdda8f97630d
Reviewed-on: https://go-review.googlesource.com/94024
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

If copying from a slice to itself, skip the write barriers
and actual memory copies.

This happens in practice in code like this snippet from
the trim pass in the compiler, when k ends up being 0:

copy(s.Values[k:], s.Values[:m])

Change-Id: Ie6924acfd56151f874d87f1d7f1f74320b4c4f10
Reviewed-on: https://go-review.googlesource.com/94023
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

The runtime.hmap type is known at compile time.
Using new(hmap) avoids loading the hmap type from the maptype
supplied as an argument to makemap which is only known at runtime.

This change makes makemap consistent with makemap_small
by using new(hmap) instead of newobject in both functions.

Change-Id: Ia47acfda527e8a71d15a1a7a4c2b54fb923515eb
Reviewed-on: https://go-review.googlesource.com/91775
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

The runtime builtin functions that are tested in append_test.go
are defined in slice.go. Renaming the test file to slice_test.go
makes this relation explicit with a common file name prefix.

Change-Id: I2f89ec23a6077fe6b80d2161efc760df828c8cd4
Reviewed-on: https://go-review.googlesource.com/90655
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Also permit passing flags to pkg-config, as we used to.

Also change the error message to refer to https://golang.org/s/invalidflag.

Fixes #23749

Change-Id: I3fbeb4c346610e6fd55e8720e720b0a40e352ab5
Reviewed-on: https://go-review.googlesource.com/93836
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: I063b556b59ecb8a8f4a3f121c32982b90eee2d74
Reviewed-on: https://go-review.googlesource.com/94159Reviewed-by: Andrew Bonventre <andybons@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Updates #22305

Change-Id: I0e6bbd880599fc1b70d0378b746d162d4a846c65
Reviewed-on: https://go-review.googlesource.com/91556
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

1) Fix the doc string for syntax.Parse: The returned AST is
always nil if there was an error and an error handler is missing.

2) Adjust the syntax Print and Dump tests such that they print and
dump the AST even in the presence of errors.

Change-Id: If658eabdcc83f578d815070bc65d1a5f6cfaddfc
Reviewed-on: https://go-review.googlesource.com/94157Reviewed-by: Matthew Dempsky <mdempsky@google.com>

Assume that an expression that is not a function call in a defer/go
statement is indeed a function that is just missing its invocation.
Report the error but continue with a sane syntax tree.

Fixes #23586.

Change-Id: Ib45ebac57c83b3e39ae4a1b137ffa291dec5b50d
Reviewed-on: https://go-review.googlesource.com/94156Reviewed-by: Matthew Dempsky <mdempsky@google.com>

Previously, if we typechecked a statement like

    var x bool = p1.f == p2.f && p1.g == p2.g

we would correctly update the '&&' node's type from 'untyped bool' to
'bool', but the '==' nodes would stay 'untyped bool'. This is
inconsistent, and caused consistency checks during walk to fail.

This CL doesn't pass toolstash because it seems to slightly affect the
register allocator's heuristics. (Presumably 'untyped bool's were
previously making it all the way through SSA?)

Fixes #23414.

Change-Id: Ia85f8cfc69b5ba35dfeb157f4edf57612ecc3285
Reviewed-on: https://go-review.googlesource.com/94022
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

Fixes #23298

Change-Id: I107c6f3a80db83f063c0daf262c6e7f7492e4d4c
Reviewed-on: https://go-review.googlesource.com/87695
Run-TryBot: Kunpei Sakai <namusyaka@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

Also, remove parser.error method (in favor of parser.errorAt) as it's only
used twice.

This is a purely cosmetic change.

Change-Id: Idb3b8b50f1c2e4d10de2ffb1c1184ceba8f7de8a
Reviewed-on: https://go-review.googlesource.com/94030Reviewed-by: Matthew Dempsky <mdempsky@google.com>

Repeat previous fix on amd64 for s390x.
Sub-word right shifts should sign extend before shifting.

Update #23812

Change-Id: I2d770190c7d8a22310b0dbd9facb3fb05afa362a
Reviewed-on: https://go-review.googlesource.com/94028
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

It's always useful to distinguish "bool" and "string" from "untyped
bool" and "untyped string", so change typefmt to do this
unconditionally.

Also, while here, replace a bare 0 with its named constant FErr.

Fixes #23833.

Change-Id: I3fcb8d7204686937439caaaf8b3973fc236d0387
Reviewed-on: https://go-review.googlesource.com/94021
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The tag was overwritten by the code for special handling unnamed
parameters.

Fixes #23045.

Change-Id: Ie2e1db3e902a07a2bbbc2a3424cea300f0a42cc3
Reviewed-on: https://go-review.googlesource.com/82775
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

Rather than only ignoring runtime.Error panics, which are a very
narrow set of possible panic values, switch it such that the json
package only captures panic values that have been properly wrapped
in a jsonError struct. This ensures that only intentional panics
originating from the json package are captured.

Fixes #23012

Change-Id: I5e85200259edd2abb1b0512ce6cc288849151a6d
Reviewed-on: https://go-review.googlesource.com/94019
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

This avoids odd behavior where sometimes a lot of useful
errors are not reported simply because of a small syntax
error.

Tested manually with non-existing files. (We cannot easily
add an automatic test because this is a stand-alone binary
in this directory that must be built manually.)

Fixes #23593.

Change-Id: Iff90f95413bed7d1023fa0a5c9eb0414144428a9
Reviewed-on: https://go-review.googlesource.com/93815Reviewed-by: Alan Donovan <adonovan@google.com>

Constant fold Not of boolean constants.

Noticed while working on #23504.

Change-Id: I965705154ee7348a1a159fad4e029b922d3171b3
Reviewed-on: https://go-review.googlesource.com/88956
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Martin Möhrmann <moehrmann@google.com>

Updates #23489

Change-Id: Ie846ccfe4c4d9295857f5da6863ac8f2ac0f2f6a
Reviewed-on: https://go-review.googlesource.com/89935
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Updates #20923

Change-Id: Ia1210ea3dec39e5db2521aeafca24d6e731f0c93
Reviewed-on: https://go-review.googlesource.com/91657
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Per the language spec clarification in https://golang.org/cl/14727.

Updates #12576
Updates #12621

Change-Id: I1e459c3c11a571bd29582761faacaa9ca3178ba6
Reviewed-on: https://go-review.googlesource.com/91895
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Transform (ADDQconst SP) into (LEA SP), because lea is rematerializeable,
so this avoids register spill. We can't mark ADDQconst as rematerializeable,
because it clobbers flags. This makes go binary ~2kb smaller.

For reference here is generated code for function from bug report.
Before:
        CALL    "".g(SB)
        MOVBLZX (SP), AX
        LEAQ    8(SP), DI
        TESTB   AX, AX
        JEQ     15
        MOVQ    "".p(SP), SI
        DUFFCOPY        $196
        MOVQ    $0, (SP)
        PCDATA  $0, $1
        CALL    "".h(SB)
        RET
        MOVQ    DI, ""..autotmp_2-8(SP) // extra spill
        PCDATA  $0, $2
        CALL    "".g(SB)
        MOVQ    ""..autotmp_2-8(SP), DI // extra register fill
        MOVQ    "".p(SP), SI
        DUFFCOPY        $196
        MOVQ    $1, (SP)
        PCDATA  $0, $1
        CALL    "".h(SB)
        JMP     14
        END

After:
        CALL    "".g(SB)
        MOVBLZX (SP), AX
        TESTB   AX, AX
        JEQ     15
        LEAQ    8(SP), DI
        MOVQ    "".p(SP), SI
        DUFFCOPY        $196
        MOVQ    $0, (SP)
        PCDATA  $0, $1
        CALL    "".h(SB)
        RET
        PCDATA  $0, $0  // no spill
        CALL    "".g(SB)
        LEAQ    8(SP), DI // rematerialized instead
        MOVQ    "".p(SP), SI
        DUFFCOPY        $196
        MOVQ    $1, (SP)
        PCDATA  $0, $1
        CALL    "".h(SB)
        JMP     14
        END

Fixes #22947

Change-Id: I8f33b860dc6c8828373477171b172ca2ce30074f
Reviewed-on: https://go-review.googlesource.com/81815
Run-TryBot: Ilya Tocar <ilya.tocar@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Popcnt has false dependency on output register and generates
MOVQ $0, reg to break it. But recently we switched MOVQ $0, reg
encoding from xor reg, reg  to actual mov $0, reg. This CL updates
code generation for popcnt to use actual XOR.

Change-Id: I4c1fc11e85758b53ba2679165fa55614ec54b27d
Reviewed-on: https://go-review.googlesource.com/82516
Run-TryBot: Ilya Tocar <ilya.tocar@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Because getStackOffset is a function pointer, the compiler assumes that
its arguments escape. Pass a value instead to avoid heap allocations.

Change-Id: Ib94e5941847f134cd00e873040a4d7fcf15ced26
Reviewed-on: https://go-review.googlesource.com/92397
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

Not a big improvement, but does help edge cases like the SSA package.
Change-Id: I40e531110b97efd5f45955be477fd0f4faa8d545
Reviewed-on: https://go-review.googlesource.com/92396
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

Using bits.TrailingZeroes instead of iterating over each bit is a small
but easy win for the common case of only one or two registers being set.

I copied in the implementation for use with pre-1.9 bootstraps.

Change-Id: Ieaa768554d7d5239a5617fbf34f1ee0b32ce1de5
Reviewed-on: https://go-review.googlesource.com/92395
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

Put everything that showed up in the allocation profile into the cache,
and reuse it across functions.

After this CL, the overhead of enabling location lists is getting
pretty close to the desired 5%:

compilecmp -all -beforeflags -dwarflocationlists=0 -afterflags -dwarflocationlists=1 -n 30 4ebad42292b6a4090faf37753dd768d2965e38c4 4ebad42292b6a4090faf37753dd768d2965e38c4
compilecmp  -dwarflocationlists=0 4ebad42292b6a4090faf37753dd768d2965e38c4  -dwarflocationlists=1 4ebad42292b6a4090faf37753dd768d2965e38c4
benchstat -geomean  /tmp/869550129 /tmp/143495132
completed   30 of   30, estimated time remaining 0s (eta 3:24PM)
name        old time/op       new time/op       delta
Template          199ms ± 4%        209ms ± 6%   +5.17%  (p=0.000 n=29+30)
Unicode          99.2ms ± 8%      100.5ms ± 6%     ~     (p=0.112 n=30+30)
GoTypes           642ms ± 3%        684ms ± 3%   +6.54%  (p=0.000 n=29+30)
SSA               8.00s ± 1%        8.71s ± 1%   +8.78%  (p=0.000 n=29+29)
Flate             129ms ± 7%        134ms ± 5%   +3.77%  (p=0.000 n=30+30)
GoParser          157ms ± 4%        164ms ± 5%   +4.35%  (p=0.000 n=29+30)
Reflect           428ms ± 3%        450ms ± 4%   +5.09%  (p=0.000 n=30+30)
Tar               195ms ± 5%        204ms ± 8%   +4.78%  (p=0.000 n=30+30)
XML               228ms ± 4%        241ms ± 4%   +5.62%  (p=0.000 n=30+29)
StdCmd            15.4s ± 1%        16.7s ± 1%   +8.29%  (p=0.000 n=29+29)
[Geo mean]        476ms             502ms        +5.35%

name        old user-time/op  new user-time/op  delta
Template          294ms ±18%        304ms ±15%     ~     (p=0.242 n=29+29)
Unicode           182ms ±27%        172ms ±28%     ~     (p=0.104 n=30+30)
GoTypes           957ms ±15%       1016ms ±12%   +6.16%  (p=0.000 n=30+30)
SSA               13.3s ± 5%        14.3s ± 3%   +7.32%  (p=0.000 n=30+28)
Flate             188ms ±17%        193ms ±17%     ~     (p=0.288 n=28+29)
GoParser          232ms ±16%        238ms ±13%     ~     (p=0.065 n=30+29)
Reflect           585ms ±13%        620ms ±10%   +5.88%  (p=0.000 n=30+30)
Tar               298ms ±21%        332ms ±23%  +11.32%  (p=0.000 n=30+30)
XML               329ms ±17%        343ms ±12%   +4.18%  (p=0.032 n=30+30)
[Geo mean]        492ms             513ms        +4.13%

name        old alloc/op      new alloc/op      delta
Template         38.3MB ± 0%       40.3MB ± 0%   +5.29%  (p=0.000 n=30+30)
Unicode          29.3MB ± 0%       29.6MB ± 0%   +1.28%  (p=0.000 n=30+29)
GoTypes           110MB ± 0%        118MB ± 0%   +6.97%  (p=0.000 n=29+30)
SSA              1.48GB ± 0%       1.61GB ± 0%   +9.06%  (p=0.000 n=30+30)
Flate            24.8MB ± 0%       26.0MB ± 0%   +4.99%  (p=0.000 n=29+30)
GoParser         30.9MB ± 0%       32.2MB ± 0%   +4.20%  (p=0.000 n=30+30)
Reflect          76.8MB ± 0%       80.6MB ± 0%   +4.97%  (p=0.000 n=30+30)
Tar              39.6MB ± 0%       41.7MB ± 0%   +5.22%  (p=0.000 n=29+30)
XML              42.0MB ± 0%       45.4MB ± 0%   +8.22%  (p=0.000 n=29+30)
[Geo mean]       63.9MB            67.5MB        +5.56%

name        old allocs/op     new allocs/op     delta
Template           383k ± 0%         405k ± 0%   +5.69%  (p=0.000 n=30+30)
Unicode            343k ± 0%         346k ± 0%   +0.98%  (p=0.000 n=30+27)
GoTypes           1.15M ± 0%        1.22M ± 0%   +6.17%  (p=0.000 n=29+29)
SSA               12.2M ± 0%        13.2M ± 0%   +8.15%  (p=0.000 n=30+30)
Flate              234k ± 0%         249k ± 0%   +6.44%  (p=0.000 n=30+30)
GoParser           315k ± 0%         332k ± 0%   +5.31%  (p=0.000 n=30+28)
Reflect            972k ± 0%        1010k ± 0%   +3.89%  (p=0.000 n=30+30)
Tar                394k ± 0%         415k ± 0%   +5.35%  (p=0.000 n=28+30)
XML                404k ± 0%         429k ± 0%   +6.31%  (p=0.000 n=29+29)
[Geo mean]         651k              686k        +5.35%

Change-Id: Ia005a8d6b33ce9f8091322f004376a3d6e5c1a94
Reviewed-on: https://go-review.googlesource.com/89357
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

Completely redesign and reimplement location list generation to be more
efficient, and hopefully not too hard to understand.

RegKills are gone. Instead of using the regalloc's liveness
calculations, redo them using the Ops' clobber information. Besides
saving a lot of Values, this avoids adding RegKills to blocks that would
be empty otherwise, which was messing up optimizations. This does mean
that it's much harder to tell whether the generation process is buggy
(there's nothing to cross-check it with), and there may be disagreements
with GC liveness. But the performance gain is significant, and it's nice
not to be messing with earlier compiler phases.

The intermediate representations are gone. Instead of producing
ssa.BlockDebugs, then dwarf.LocationLists, and then finally real
location lists, go directly from the SSA to a (mostly) real location
list. Because the SSA analysis happens before assembly, it stores
encoded block/value IDs where PCs would normally go. It would be easier
to do the SSA analysis after assembly, but I didn't want to retain the
SSA just for that.

Generation proceeds in two phases: first, it traverses the function in
CFG order, storing the state of the block at the beginning and end. End
states are used to produce the start states of the successor blocks. In
the second phase, it traverses in program text order and produces the
location lists. The processing in the second phase is redundant, but
much cheaper than storing the intermediate representation. It might be
possible to combine the two phases somewhat to take advantage of cases
where the CFG matches the block layout, but I haven't tried.

Location lists are finalized by adding a base address selection entry,
translating each encoded block/value ID to a real PC, and adding the
terminating zero entry. This probably won't work on OSX, where dsymutil
will choke on the base address selection. I tried emitting CU-relative
relocations for each address, and it was *very* bad for performance --
it uses more memory storing all the relocations than it does for the
actual location list bytes. I think I'm going to end up synthesizing the
relocations in the linker only on OSX, but TBD.

TestNexting needs updating: with more optimizations working, the
debugger doesn't stop on the continue (line 88) any more, and the test's
duplicate suppression kicks in. Also, dx and dy live a little longer
now, but they have the correct values.

Change-Id: Ie772dfe23a4e389ca573624fac4d05401ae32307
Reviewed-on: https://go-review.googlesource.com/89356
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

We're trying to enable location lists by default, and it's easier to do
that if we don't have to worry about scope tracking at the same time.
We can evaluate their performance impact separately.

However, that does mean that "err" is ambiguous in the test case, so
rename it to err2 for now.

Change-Id: I24f119016185c52b7d9affc74207f6a5b450fb6f
Reviewed-on: https://go-review.googlesource.com/89355
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

By default futexes are permitted in shared memory regions, which
requires the kernel to translate the memory address. Since our futexes
are never in shared memory, set FUTEX_PRIVATE_FLAG, which makes futex
operations slightly more efficient.

Change-Id: I2a82365ed27d5cd8d53c5382ebaca1a720a80952
Reviewed-on: https://go-review.googlesource.com/80144Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>