And adds missing tests.

Fixes #14970

Change-Id: I0dba02603bc245f555498cb5dd3e0a9d87c52353
Reviewed-on: https://go-review.googlesource.com/21467Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

This code made sense before fmt switched to using sync.Pool, but a
sync.Pool clears all items on GC, so not reusing something based on
size is just a waste of memory.

Change-Id: I201312b0ee6c572ff3c0ffaf71e42623a160d23f
Reviewed-on: https://go-review.googlesource.com/21480Reviewed-by: Rob Pike <r@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Introduces the new relocation variant RV_390_DBL which indicates
that the relocation value should be shifted right by 1 (to make
it 2-byte aligned).

Change-Id: I03fa96b4759ee19330c5298c3720746622fb1a03
Reviewed-on: https://go-review.googlesource.com/20878
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Generated with eg.

Passes toolstash -cmp.

Change-Id: I3af35191e73a558080f777a4eed93bcec7dfe1f5
Reviewed-on: https://go-review.googlesource.com/21469
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Rather than specifying every field that should be cleared in Reset,
it is better to just zero the entire struct and only preserve or set the
fields that we actually care about. This ensures that the Header field
is reset for the next use.

Fixes #15077

Change-Id: I41832e506d2d64c62b700aa1986e7de24a577511
Reviewed-on: https://go-review.googlesource.com/21465
Run-TryBot: Joe Tsai <joetsai@digital-static.net>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Handle this case:
if 0 <= i && i < len(a) {
        use a[i]
}

Shaves about 5k from pkg/tools/linux_amd64/*.

Change-Id: I6675ff49aa306b0d241b074c5738e448204cd981
Reviewed-on: https://go-review.googlesource.com/21431
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #13705

Change-Id: I86c60c78ce0394f830f904c9cba83ebbf3efc046
Reviewed-on: https://go-review.googlesource.com/21328
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Changes made:
* Reader.flg is not used anywhere else other than readHeader and
does not need to be stored.
* Store Reader.digest and Writer.digest as uint32s rather than as
a hash.Hash32 and use the crc32.Update function instead. This simplifies
initialization logic since the zero value of uint32 is the initial
CRC-32 value. There are no performance detriments to doing this since
the hash.Hash32 returned by crc32 simply calls crc32.Update as well.
* s/[0:/[:/            Consistently use shorter notation for slicing.
* s/RFC1952/RFC 1952/  Consistently use RFC notation.

Change-Id: I55416a19f4836cbed943adaa3f672538ea5d166d
Reviewed-on: https://go-review.googlesource.com/21429Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Joe Tsai <joetsai@digital-static.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>

The issue was seen when inlining an exported function that contained
a fallthrough statement.

Fixes #15071

Change-Id: I1e8215ad49d57673dba7e8f8bd2ed8ad290dc452
Reviewed-on: https://go-review.googlesource.com/21452Reviewed-by: Dave Cheney <dave@cheney.net>

Updates the syscall generator for patchset 4 of https://golang.org/cl/21388.

Updates #14959

Change-Id: Icbd6df489887d3dcc076dfc73d4feb1376abaf8b
Reviewed-on: https://go-review.googlesource.com/21428Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

The IsStruct case is meant to handle cases like append(f()) where f's
result parameters are something like ([]int, int, int). However, at
this point in the compiler we've already rewritten append(f()) into
"tmp1, tmp2, tmp3 := f(); append(tmp1, tmp2, tmp3)".

As further evidence, the t.Elem() is not a valid method call for a
struct type anyway, which would trigger the Fatalf call in Type.Elem
if this code was ever hit.

Change-Id: Ia066f93df66ee3fadc9a9a0f687be7b5263af163
Reviewed-on: https://go-review.googlesource.com/21427
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Make sure that for any DLL that Go uses itself, we only look for the
DLL in the Windows System32 directory, guarding against DLL preloading
attacks.

(Unless the Windows version is ancient and LoadLibraryEx is
unavailable, in which case the user probably has bigger security
problems anyway.)

This does not change the behavior of syscall.LoadLibrary or NewLazyDLL
if the DLL name is something unused by Go itself.

This change also intentionally does not add any new API surface. Instead,
x/sys is updated with a LoadLibraryEx function and LazyDLL.Flags in:
    https://golang.org/cl/21388

Updates #14959

Change-Id: I8d29200559cc19edf8dcf41dbdd39a389cd6aeb9
Reviewed-on: https://go-review.googlesource.com/21140Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #15061.

Change-Id: I71f69f398d1c5f3a884bbd044786f1a5600d0fae
Reviewed-on: https://go-review.googlesource.com/21398
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

gorename -from '"cmd/compile/internal/gc".Node.Int' -to 'Int64'

Change-Id: I2fe3bf9a26ae6b0600d990d0c981e4b8b53020a4
Reviewed-on: https://go-review.googlesource.com/21426Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Replace isideal(t) with t.IsUntyped().
Replace Istype(t, k) with t.IsKind(k).
Replace isnilinter(t) with t.IsEmptyInterface().

Also replace a lot of t.IsKind(TFOO) with t.IsFoo().

Replacements prepared mechanically with gofmt -w -r.

Passes toolstash -cmp.

Change-Id: Iba48058f3cc863e15af14277b5ff5e729e67e043
Reviewed-on: https://go-review.googlesource.com/21424Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>

This removes all access to Type.Bound
from outside type.go.

Update sinit to make a new type rather than
copy and mutate.

Update bimport to create a new slice type
instead of mutating TDDDFIELD.
These are rare, so the extra allocs are nominal.

I’m not happy about having a setter,
but it appears the most practical route
forward at the moment, and it only has a few uses.

Passes toolstash -cmp.

Change-Id: I174f07c8f336afc656904bde4bdbde4f3ef0db96
Reviewed-on: https://go-review.googlesource.com/21423
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Generated by eg.

Passes toolstash -cmp.

Change-Id: I7516c211ca9aacf824f74894671dc62d31763b01
Reviewed-on: https://go-review.googlesource.com/21422
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

This eliminates all direct reads of Type.Bound
outside type.go.

Change-Id: I0a9a72539f8f4c0de7f5e05e1821936bf7db5eb7
Reviewed-on: https://go-review.googlesource.com/21421
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Add AlgKind enum type to represent AFOO values.

Add IsComparable, IsRegularMemory, IncomparableField helper methods to
codify common higher-level idioms.

Passes toolstash -cmp.

Change-Id: I54c544953997a8ccc72396b3058897edcbbea392
Reviewed-on: https://go-review.googlesource.com/21420
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes a problem when using the external linker on Solaris.  The Solaris
external linker still doesn't work due to issue #14957.

The problem is, for example, with `go test cmd/objdump`:

        objdump_test.go:71: go build fmthello.go: exit status 2
                # command-line-arguments
                /var/gcc/iant/go/pkg/tool/solaris_amd64/link: running gcc failed: exit status 1
                Undefined                       first referenced
                 symbol                             in file
                x_cgo_callers                       /tmp/go-link-355600608/go.o
                ld: fatal: symbol referencing errors
                collect2: error: ld returned 1 exit status

Change-Id: I54917cfd5c288ee77ea25c439489bd2c9124fe73
Reviewed-on: https://go-review.googlesource.com/21392
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

This change exposes a facility to create new struct types from a slice of
reflect.StructFields.

- reflect: first stab at implementing StructOf
- reflect: tests for StructOf

StructOf creates new struct types in the form of structTypeWithMethods
to accomodate the GC (especially the uncommonType.methods slice field.)

Creating struct types with embedded interfaces with unexported methods
is not supported yet and will panic.
Creating struct types with non-ASCII field names or types is not yet
supported (see #15064.)

Binaries' sizes for linux_amd64:

old=tip (0104a31b)

            old bytes     new bytes     delta
bin/go      9911336       9915456       +0.04%
reflect     781704        830048        +6.18%

Updates #5748.
Updates #15064.

Change-Id: I3b8fd4fadd6ce3b1b922e284f0ae72a3a8e3ce44
Reviewed-on: https://go-review.googlesource.com/9251Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>

Change-Id: I41722ee605ea76a6b52e8a7e1e10f2293cef1a7a
Reviewed-on: https://go-review.googlesource.com/21371Reviewed-by: David Crawshaw <crawshaw@golang.org>

There are 5293 loop in the main go repository.
A survey of the top most common for loops:

     18 for __k__ := 0; i < len(sa.Addr); i++ {
     19 for __k__ := 0; ; i++ {
     19 for __k__ := 0; i < 16; i++ {
     25 for __k__ := 0; i < length; i++ {
     30 for __k__ := 0; i < 8; i++ {
     49 for __k__ := 0; i < len(s); i++ {
     67 for __k__ := 0; i < n; i++ {
    376 for __k__ := range __slice__ {
    685 for __k__, __v__ := range __slice__ {
   2074 for __, __v__ := range __slice__ {

The algorithm to find induction variables handles all cases
with an upper limit. It currently doesn't find related induction
variables such as c * ind or c + ind.

842 out of 22954 bound checks are removed for src/make.bash.
1957 out of 42952 bounds checks are removed for src/all.bash.

Things to do in follow-up CLs:
* Find the associated pointer for `for _, v := range a {}`
* Drop the NilChecks on the pointer.
* Replace the implicit induction variable by a loop over the pointer

Generated garbage can be reduced if we share the sdom between passes.

% benchstat old.txt new.txt
name       old time/op     new time/op     delta
Template       337ms ± 3%      333ms ± 3%    ~             (p=0.258 n=9+9)
GoTypes        1.11s ± 2%      1.10s ± 2%    ~           (p=0.912 n=10+10)
Compiler       5.25s ± 1%      5.29s ± 2%    ~             (p=0.077 n=9+9)
MakeBash       33.5s ± 1%      34.1s ± 2%  +1.85%          (p=0.011 n=9+9)

name       old alloc/op    new alloc/op    delta
Template      63.6MB ± 0%     63.9MB ± 0%  +0.52%         (p=0.000 n=10+9)
GoTypes        218MB ± 0%      219MB ± 0%  +0.59%         (p=0.000 n=10+9)
Compiler       978MB ± 0%      985MB ± 0%  +0.69%        (p=0.000 n=10+10)

name       old allocs/op   new allocs/op   delta
Template        582k ± 0%       583k ± 0%  +0.10%        (p=0.000 n=10+10)
GoTypes        1.78M ± 0%      1.78M ± 0%  +0.12%        (p=0.000 n=10+10)
Compiler       7.68M ± 0%      7.69M ± 0%  +0.05%        (p=0.000 n=10+10)

name       old text-bytes  new text-bytes  delta
HelloSize       581k ± 0%       581k ± 0%  -0.08%        (p=0.000 n=10+10)
CmdGoSize      6.40M ± 0%      6.39M ± 0%  -0.08%        (p=0.000 n=10+10)

name       old data-bytes  new data-bytes  delta
HelloSize      3.66k ± 0%      3.66k ± 0%    ~     (all samples are equal)
CmdGoSize       134k ± 0%       134k ± 0%    ~     (all samples are equal)

name       old bss-bytes   new bss-bytes   delta
HelloSize       126k ± 0%       126k ± 0%    ~     (all samples are equal)
CmdGoSize       149k ± 0%       149k ± 0%    ~     (all samples are equal)

name       old exe-bytes   new exe-bytes   delta
HelloSize       947k ± 0%       946k ± 0%  -0.01%        (p=0.000 n=10+10)
CmdGoSize      9.92M ± 0%      9.91M ± 0%  -0.06%        (p=0.000 n=10+10)

Change-Id: Ie74bdff46fd602db41bb457333d3a762a0c3dc4d
Reviewed-on: https://go-review.googlesource.com/20517Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>

The new function runtime.SetCgoTraceback may be used to register stack
traceback and symbolizer functions, written in C, to do a stack
traceback from cgo code.

There is a sample implementation of runtime.SetCgoSymbolizer at
github.com/ianlancetaylor/cgosymbolizer.  Just importing that package is
sufficient to get symbolic C backtraces.

Currently only supported on linux/amd64.

Change-Id: If96ee2eb41c6c7379d407b9561b87557bfe47341
Reviewed-on: https://go-review.googlesource.com/17761Reviewed-by: Austin Clements <austin@google.com>

Added a debug flag "-d closure" to explain compilation of
closures (should this be done some other way? Should we
rewrite the "-m" flag to "-d escapes"?)  Used this to
discover that cause was an OXXX node in the captured vars
list, and in turn noticed that OXXX nodes are explicitly
ignored in all other processing of captured variables.

Couldn't figure out a reproducer, did verify that this OXXX
was not caused by an unnamed return value (which is one use
of these).  Verified lack of heap allocation by examining -S
output.

Assembly:
(runtime/mgc.go:1371) PCDATA $0, $2
(runtime/mgc.go:1371) CALL "".notewakeup(SB)
(runtime/mgc.go:1377) LEAQ "".gcBgMarkWorker.func1·f(SB), AX
(runtime/mgc.go:1404) MOVQ AX, (SP)
(runtime/mgc.go:1404) MOVQ "".autotmp_2242+88(SP), CX
(runtime/mgc.go:1404) MOVQ CX, 8(SP)
(runtime/mgc.go:1404) LEAQ go.string."GC worker (idle)"(SB), AX
(runtime/mgc.go:1404) MOVQ AX, 16(SP)
(runtime/mgc.go:1404) MOVQ $16, 24(SP)
(runtime/mgc.go:1404) MOVB $20, 32(SP)
(runtime/mgc.go:1404) MOVQ $0, 40(SP)
(runtime/mgc.go:1404) PCDATA $0, $2
(runtime/mgc.go:1404) CALL "".gopark(SB)

Added a check for compiling_runtime to ensure that this is
caught in the future.  Added a test to test the check.
Verified that 1.5.3 did NOT reject the test case when
compiled with -+ flag, so this is not a recently added bug.

Cause of bug is two-part -- there was no leaking closure
detection ever, and instead it relied on capture-of-variables
to trigger compiling_runtime test, but closures improved in
1.5.3 so that mere capture of a value did not also capture
the variable, which thus allowed closures to escape, as well
as this case where the escape was spurious.  In
fixedbugs/issue14999.go, compare messages for f and g;
1.5.3 would reject g, but not f.  1.4 rejects both because
1.4 heap-allocates parameter x for both.

Fixes #14999.

Change-Id: I40bcdd27056810628e96763a44f2acddd503aee1
Reviewed-on: https://go-review.googlesource.com/21322
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Change-Id: Iba82a5bd3846f7ab038cc10ec72ff6bcd2c0b484
Reviewed-on: https://go-review.googlesource.com/21377
Run-TryBot: Dave Cheney <dave@cheney.net>
Reviewed-by: Dave Cheney <dave@cheney.net>

Fix build error on darwin/{arm,arm64} caused by a62ae9f6.

Change-Id: I7da4d147a529b11b3e71352a9276a57595ec4b05
Reviewed-on: https://go-review.googlesource.com/21356
Run-TryBot: Dave Cheney <dave@cheney.net>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Also cleans up return parameter stutter and missing periods.

Change-Id: I47f5c230227ddfd1b105d5e06842f89ffea50760
Reviewed-on: https://go-review.googlesource.com/21362Reviewed-by: Andrew Gerrand <adg@golang.org>

Issue #8633 (and #9134) noted that we didn't document the rules about
closing the Response.Body when Client.Do returned both a non-nil
*Response and a non-nil error (which can only happen when the user's
CheckRedirect returns an error).

In the process of investigating, I cleaned this code up a bunch, but
no user-visible behavior should have changed, except perhaps some
better error messages in some cases.

It turns out it's always been the case that when a CheckRedirect error
occurs, the Response.Body is already closed. Document that.

And the new code makes that more obvious too.

Fixes #8633

Change-Id: Ibc40cc786ad7fc4e0cf470d66bb559c3b931684d
Reviewed-on: https://go-review.googlesource.com/21364
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Andrew Gerrand <adg@golang.org>

The change in 20907 fixed varexpr but broke aliased.  After that change,
a reference to a field in a struct would not be seen as aliasing itself.
Before that change, it would, but only because all fields in a struct
aliased everything.

This CL changes the compiler to consider all references to a field as
aliasing all other fields in that struct.  This is imperfect--a
reference to one field does not alias another field--but is a simple fix
for the immediate problem.  A better fix would require tracking the
specific fields as well.

Fixes #15042.

Change-Id: I5c95c0dd7b0699e53022fce9bae2e8f50d6d1d04
Reviewed-on: https://go-review.googlesource.com/21390
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

... when the backend can't be reached.

Fixes #9864

Change-Id: I9e4814824943060e0101b6236d6dfd8d7822b4c7
Reviewed-on: https://go-review.googlesource.com/21363Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Updates x/net/http2 to git rev 31df19d6 for changes since Go 1.6.

The main change was https://go-review.googlesource.com/19726 (move
merging of HEADERS and CONTINUATION into Framer), but there were a few
garbage reduction changes too.

Change-Id: I882443d20749f8638f637a2835efe92538c95d31
Reviewed-on: https://go-review.googlesource.com/21365
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Andrew Gerrand <adg@golang.org>

The default is 10MB, like http2, but can be configured with a new
field http.Transport.MaxResponseHeaderBytes.

Fixes #9115

Change-Id: I01808ac631ce4794ef2b0dfc391ed51cf951ceb1
Reviewed-on: https://go-review.googlesource.com/21329
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Andrew Gerrand <adg@golang.org>

ANDQConst show up occassionally because of right shifting lowering.
ORs and XORs are already folded properly during generic.

Change-Id: I2f9134679555029c641264ce5333d70e167c65f7
Reviewed-on: https://go-review.googlesource.com/21375Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Very common, cuts about 70k from pkg/tools/linux_amd64/* binaries.

Change-Id: Ied0c049e56e56a56810c781435d79027fbcaf274
Reviewed-on: https://go-review.googlesource.com/21374Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>

In a number of places the code was joining filepaths explicitly with
"/", instead of using filepath.Join. This may cause problems on Windows
(or other) platforms.

This is in support of https://go-review.googlesource.com/#/c/18057

Change-Id: Ieb1334f35ddb2e125be690afcdadff8d7b0ace10
Reviewed-on: https://go-review.googlesource.com/21369Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Rather than checking the block final bit on the next invocation
of nextBlock, we check it at the termination of the current block.
This ensures that we return (n, io.EOF) instead of (0, io.EOF)
more frequently for most streams.

However, there are certain situations where an eager io.EOF is not done:
1) We previously returned from Read because the write buffer of the internal
dictionary was full, and it just so happens that there is no more data
remaining in the stream.
2) There exists a [non-final, empty, raw block] after all blocks that
actually contain uncompressed data. We cannot return io.EOF eagerly here
since it would break flushing semantics.

Both situations happen infrequently, but it is still important to note that
this change does *not* guarantee that flate will *always* return (n, io.EOF).

Furthermore, this CL makes no changes to the pattern of ReadByte calls
to the underlying io.ByteReader.

Below is the motivation for this change, pulling the text from
@bradfitz's CL/21290:

net/http and other things work better when io.Reader implementations
return (n, io.EOF) at the end, instead of (n, nil) followed by (0,
io.EOF). Both are legal, but the standard library has been moving
towards n+io.EOF.

An investigation of net/http connection re-use in
https://github.com/google/go-github/pull/317 revealed that with gzip
compression + http/1.1 chunking, the net/http package was not
automatically reusing the underlying TCP connections when the final
EOF bytes were already read off the wire. The net/http package only
reuses the connection if the underlying Readers (many of them nested
in this case) all eagerly return io.EOF.

Previous related CLs:
    https://golang.org/cl/76400046 - tls.Reader
    https://golang.org/cl/58240043 - http chunked reader

In addition to net/http, this behavior also helps things like
ioutil.ReadAll (see comments about performance improvements in
https://codereview.appspot.com/49570044)

Updates #14867
Updates google/go-github#317

Change-Id: I637c45552efb561d34b13ed918b73c660f668378
Reviewed-on: https://go-review.googlesource.com/21302
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Compound AUTO types weren't named previously.  That was because live
variable analysis (plive.go) doesn't handle spilling to compound types.
It can't handle them because there is no valid place to put VARDEFs when
regalloc is spilling compound types.

compound types = multiword builtin types: complex, string, slice, and
interface.

Instead, we split named AUTOs into individual one-word variables.  For
example, a string s gets split into a byte ptr s.ptr and an integer
s.len.  Those two variables can be spilled to / restored from
independently.  As a result, live variable analysis can handle them
because they are one-word objects.

This CL will change how AUTOs are described in DWARF information.
Consider the code:

func f(s string, i int) int {
    x := s[i:i+5]
    g()
    return lookup(x)
}

The old compiler would spill x to two consecutive slots on the stack,
both named x (at offsets 0 and 8).  The new compiler spills the pointer
of x to a slot named x.ptr.  It doesn't spill x.len at all, as it is a
constant (5) and can be rematerialized for the call to lookup.

So compound objects may not be spilled in their entirety, and even if
they are they won't necessarily be contiguous.  Such is the price of
optimization.

Re-enable live variable analysis tests.  One test remains disabled, it
fails because of #14904.

Change-Id: I8ef2b5ab91e43a0d2136bfc231c05d100ec0b801
Reviewed-on: https://go-review.googlesource.com/21233
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

The conventional name for a sync.Mutex is "mu".

These "lk" names date back to a time before conventions.

Change-Id: Iee57f9f4423d04269e1125b5d82455c453aac26f
Reviewed-on: https://go-review.googlesource.com/21361
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

For idx1 ops, SP can appear in the index slot.
Swap SP into the base register slot so we can encode
the instruction.

Fixes #15053

Change-Id: I19000cc9d6c86c7611743481e6e2cb78b1ef04eb
Reviewed-on: https://go-review.googlesource.com/21384
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>