This CL was automatically generated using a special-purpose AST
rewriting tool, followed by manual editing to put some comments back in
the right places and fix some bad line breaks.

The result is not perfect but it's a big step toward getting back to
sanity, and because it was automatically generated there is a decent
chance that it is correct.

Passes toolstash -cmp.

Update #14473.

Change-Id: I01c09078a6d78e2b008bc304d744b79469a38d3d
Reviewed-on: https://go-review.googlesource.com/20440Reviewed-by: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

More idiomatic naming (in particular, matches the naming used for
go/types.Signature).

Also, convert more code to use these methods and/or IterFields.
(Still more to go; only made a quick pass for low hanging fruit.)

Passes toolstash -cmp.

Change-Id: I61831bfb1ec2cd50d4c7efc6062bca4e0dcf267b
Reviewed-on: https://go-review.googlesource.com/20451Reviewed-by: Ian Lance Taylor <iant@golang.org>

Alternative to golang.org/cl/19852. This memory layout doesn't have
an easy type representation, but it is noticeably smaller than the
current funcType, and saves significant extra space.

Some notes on the layout are in reflect/type.go:

// A *rtype for each in and out parameter is stored in an array that
// directly follows the funcType (and possibly its uncommonType). So
// a function type with one method, one input, and one output is:
//
//	struct {
//		funcType
//		uncommonType
//		[2]*rtype    // [0] is in, [1] is out
//		uncommonTypeSliceContents
//	}

There are three arbitrary limits introduced by this CL:

1. No more than 65535 function input parameters.
2. No more than 32767 function output parameters.
3. reflect.FuncOf is limited to 128 parameters.

I don't think these are limits in practice, but are worth noting.

Reduces godoc binary size by 2.4%, 330KB.

For #6853.

Change-Id: I225c0a0516ebdbe92d41dfdf43f716da42dfe347
Reviewed-on: https://go-review.googlesource.com/19916Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #14662

Change-Id: I8f7d5e8d2dd8dc763e940e061b424427359246e7
Reviewed-on: https://go-review.googlesource.com/20462Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: Iaa23d27043e6a050075b40072e466623418ba977
Reviewed-on: https://go-review.googlesource.com/19878Reviewed-by: Rob Pike <r@golang.org>

Passes toolstash -cmp.

Change-Id: I325b02dcc8412ded0dc304d43377c0bdf59c66a8
Reviewed-on: https://go-review.googlesource.com/20405Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #14687

Change-Id: I51fd8842d35c82db71cc5b28c4c0550871461eb6
Reviewed-on: https://go-review.googlesource.com/20421Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Instead of a pointer on every rtype, use a bit flag to indicate that
the contents of uncommonType directly follows the rtype value when it
is needed.

This requires a bit of juggling in the compiler's rtype encoder. The
backing arrays for fields in the rtype are presently encoded directly
after the slice header. This packing requires separating the encoding
of the uncommonType slice headers from their backing arrays.

Reduces binary size of godoc by ~180KB (1.5%).
No measurable change in all.bash time.
For #6853.

Change-Id: I60205948ceb5c0abba76fdf619652da9c465a597
Reviewed-on: https://go-review.googlesource.com/19790Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Converting an and-K into a pair of shifts for K that will
fit in a one-byte argument is probably not an optimization,
and it also interferes with other patterns that we want to
see fire, like (<< (AND K)) [for small K] and bounds check
elimination for masked indices.

Turns out that on Intel, even 32-bit signed immediates beat
the shift pair; the size reduction of tool binaries is 0.09%
vs 0.07% for only the 8-bit immediates.

RLH found this one working on the new/next GC.

Change-Id: I2414a8de1dd58d680d18587577fbadb7ff4f67d9
Reviewed-on: https://go-review.googlesource.com/20410Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: David Chase <drchase@google.com>

Some cleaned up documentation, but no code changes.

Change-Id: I145398bb6d118c626ab3873ef75dbb64ebc286e9
Reviewed-on: https://go-review.googlesource.com/20404
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Don't do a substring search to test for a timeout error.

Fixes #14722 (maybe)

Change-Id: I4e18c749d6fd92c084a1b0b83a805119e1ae5ff2
Reviewed-on: https://go-review.googlesource.com/20403
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

* Simplify the nilcheck generated by
for _, e := range a {}
* No effect on the generated code because these nil checks
don't end up in the generated code.
* Useful for other analysis, e.g. it'll remove one dependecy
on the induction variable.

Change-Id: I6ee66ddfdc010ae22aea8dca48163303d93de7a9
Reviewed-on: https://go-review.googlesource.com/20307
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Make more idiomatic with a defer cleanup, which allows declaring
variables closer to their first use, rather than up front before the
first goto statement.

Also, split the legacy code generation code path into a separate
genlegacy function, analogous to the new genssa.

Passes toolstash -cmp.

Change-Id: I86c22838704f6861b75716ae64ba103b0e73b12f
Reviewed-on: https://go-review.googlesource.com/20353Reviewed-by: Dave Cheney <dave@cheney.net>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Same idea as golang.org/cl/20322.

Passes toolstash/buildall.

Change-Id: Ida5960e57ff6e1e8de75c2720f21aeae56a8e415
Reviewed-on: https://go-review.googlesource.com/20352
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: Iec323998133ef20ff962f06a46d15dd342a82f5f
Reviewed-on: https://go-review.googlesource.com/20390Reviewed-by: Ian Lance Taylor <iant@golang.org>

getgrouplist is non-standard and has slightly different semantics on
each platform.  Darwin defines the function in terms of ints instead of
gid_ts.  Solaris only recently supported the call, so stubbing out for
now.

Fixes #14696
Fixes #14709

Change-Id: I5a44538d41594909efb6f3f9610c55d638c36757
Reviewed-on: https://go-review.googlesource.com/20348
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Accidentally added in https://golang.org/cl/20242.

This is in preparation for transformation by an automated tool.

Passes toolstash -cmp.

Update #14473.

Change-Id: I28c637d220df3ccaa8e368bfbea7282a6e66662e
Reviewed-on: https://go-review.googlesource.com/20402
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Before, those C files might have been intended for the Plan 9 C compiler,
but that option was removed in Go 1.5. We can simplify the maintenance
of cgo packages now if we assume C files (and C++ and M and SWIG files)
should only be considered when cgo is enabled.

Also remove newly unnecessary build tags in runtime/cgo's C files.

Fixes #14123

Change-Id: Ia5a7fe62b9469965aa7c3547fe43c6c9292b8205
Reviewed-on: https://go-review.googlesource.com/19613Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Bug accidentally inserted in https://golang.org/cl/20210.  Doesn't seem
to make a difference, but restore original code anyhow.

Update #14473.

Change-Id: I9cf87987ff158e27c7231027819317cdde8c132c
Reviewed-on: https://go-review.googlesource.com/20401
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Trailers() returns the headers that were set by the handler after the
headers were written "to the wire" (in this case HeaderMap) and that
were also specified in a proper header called "Trailer".

Neither HeaderMap or trailerMap (used for Trailers()) are manipulated by
the handler code, instead a third stagingMap is given to the
handler. This avoid a reference kept by handler to affect the recorded
results.

If a handler just modify the header but doesn't call any Write or Flush
method from ResponseWriter (or Flusher) interface, HeaderMap will not be
updated. In this case, calling Flush in the recorder is enough to get
the HeaderMap filled.

Fixes #14531.
Fixes #8857.

Change-Id: I42842341ec3e95c7b87d7e6f178c65cd03d63cc3
Reviewed-on: https://go-review.googlesource.com/20047Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #14646.

Change-Id: I0bb82ed6d3533633cd8369ba37aa467948bbe155
Reviewed-on: https://go-review.googlesource.com/20381
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

Change-Id: I754861147838d0f6c184d8deb8a028062a1d3214
Reviewed-on: https://go-review.googlesource.com/20400Reviewed-by: Russ Cox <rsc@golang.org>

Deleting the string merging pass makes the linker 30-35% faster
but makes jujud (using the github.com/davecheney/benchjuju snapshot) 2.5% larger.
Two optimizations bring the space overhead down to 0.6%.

First, change the default alignment for string data to 1 byte.
(It was previously defaulting to larger amounts, usually pointer width.)

Second, write out the type string for T (usually a bigger expression) as "*T"[1:],
so that the type strings for T and *T share storage.

Combined, these obtain the bulk of the benefit of string merging
at essentially no cost. The remaining benefit from string merging
is not worth the excessive cost, so delete it.

As penance for making the jujud binary 0.6% larger,
the next CL in this sequence trims the reflect functype
information enough to make the jujud binary overall 0.75% smaller
(that is, that CL has a net -1.35% effect).

For #6853.
Fixes #14648.

Change-Id: I3fdd74c85410930c36bb66160ca4174ed540fc6e
Reviewed-on: https://go-review.googlesource.com/20334Reviewed-by: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>

cmd/link is clearly the way forward.
The original rationale for cmd/newlink was that it would be a clean Go reimplementation.
But when push came to shove, cmd/link got converted from C instead,
and all the work on build modes and the like is in cmd/link now.
Cleaning up cmd/link is likely a much better plan.

This directory is something to delete from releases and the
testdata is something that breaks every time the .6 format changes.
Fix both problems by just deleting it outright.

Change-Id: Ib00fecda258ba685f1752725971182af9d4459eb
Reviewed-on: https://go-review.googlesource.com/20380
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Passes toolstash -cmp.

Update #14473.

Change-Id: I717ebd948dfc8faf8b9ef5aa02c67484af618d18
Reviewed-on: https://go-review.googlesource.com/20359Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

benchstat master2 arg3b
name      old time/op    new time/op    delta
Template     441ms ± 4%     444ms ± 6%    ~     (p=0.335 n=22+25)
GoTypes      1.51s ± 2%     1.51s ± 2%    ~     (p=0.129 n=25+21)
Compiler     5.59s ± 1%     5.56s ± 2%  -0.65%  (p=0.001 n=24+21)

name      old alloc/op   new alloc/op   delta
Template    85.6MB ± 0%    85.3MB ± 0%  -0.40%  (p=0.000 n=25+24)
GoTypes      307MB ± 0%     305MB ± 0%  -0.38%  (p=0.000 n=25+25)
Compiler    1.06GB ± 0%    1.05GB ± 0%  -0.43%  (p=0.000 n=25+25)

name      old allocs/op  new allocs/op  delta
Template     1.10M ± 0%     1.09M ± 0%  -1.04%  (p=0.000 n=25+25)
GoTypes      3.36M ± 0%     3.32M ± 0%  -1.13%  (p=0.000 n=25+24)
Compiler     13.0M ± 0%     12.9M ± 0%  -1.12%  (p=0.000 n=25+25)

Change-Id: I1280b846e895c00b95bb6664958a7765bd819610
Reviewed-on: https://go-review.googlesource.com/20296Reviewed-by: Keith Randall <khr@golang.org>

Also, add more failure output to debug why linux/mips64le and
linux/ppc64 are failing. They should be working. I suspect their
builder test envs are missing something.

Change-Id: I97273fe72c4e3009db400394636d0da1ef147485
Reviewed-on: https://go-review.googlesource.com/20358
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

This adds "slicing by 8" optimization to Castagnoli tables which will
speed up CRC32 calculation on systems without asssembler,
which are all but AMD64.

In my tests, it is faster to use "slicing by 8" for sizes all down to
16 bytes, so the switchover point has been adjusted.

There are no benchmarks for small sizes, so I have added one for 40 bytes,
as well as one for bigger sizes (32KB).

Castagnoli, No assembler, 40 Byte payload: (before, after)
BenchmarkCastagnoli40B-4   10000000     161 ns/op         246.94 MB/s
BenchmarkCastagnoli40B-4   20000000     100 ns/op         398.01 MB/s

Castagnoli, No assembler, 32KB payload: (before, after)
BenchmarkCastagnoli32KB-4     10000     115426 ns/op      283.89 MB/s
BenchmarkCastagnoli32KB-4     30000     45171 ns/op       725.41 MB/s

IEEE, No assembler, 1KB payload: (before, after)
BenchmarkCrc1KB-4       500000     3604 ns/op         284.10 MB/s
BenchmarkCrc1KB-4      1000000     1463 ns/op         699.79 MB/s

Compared:
benchmark                     old ns/op     new ns/op     delta
BenchmarkCastagnoli40B-4      161           100           -37.89%
BenchmarkCastagnoli32KB-4     115426        45171         -60.87%
BenchmarkCrc1KB-4             3604          1463          -59.41%

benchmark                     old MB/s     new MB/s     speedup
BenchmarkCastagnoli40B-4      246.94       398.01       1.61x
BenchmarkCastagnoli32KB-4     283.89       725.41       2.56x
BenchmarkCrc1KB-4             284.10       699.79       2.46x

Change-Id: I303e4ec84e8d4dafd057d64c0e43deb2b498e968
Reviewed-on: https://go-review.googlesource.com/19335
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

name      old time/op    new time/op    delta
Template     441ms ± 4%     446ms ± 4%  +1.23%  (p=0.048 n=22+25)
GoTypes      1.51s ± 2%     1.51s ± 2%    ~     (p=0.224 n=25+25)
Compiler     5.59s ± 1%     5.57s ± 2%  -0.38%  (p=0.019 n=24+24)

name      old alloc/op   new alloc/op   delta
Template    85.6MB ± 0%    85.6MB ± 0%  -0.11%  (p=0.000 n=25+24)
GoTypes      307MB ± 0%     305MB ± 0%  -0.45%  (p=0.000 n=25+25)
Compiler    1.06GB ± 0%    1.06GB ± 0%  -0.34%  (p=0.000 n=25+25)

name      old allocs/op  new allocs/op  delta
Template     1.10M ± 0%     1.10M ± 0%  -0.03%  (p=0.001 n=25+24)
GoTypes      3.36M ± 0%     3.35M ± 0%  -0.13%  (p=0.000 n=25+25)
Compiler     13.0M ± 0%     13.0M ± 0%  -0.12%  (p=0.000 n=25+24)

Change-Id: I7fc18acbc3b1588aececef9692e24a0bd3dba974
Reviewed-on: https://go-review.googlesource.com/20295
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Change-Id: Ifa09bccb8482a6141d0aa862cef674fade30e2eb
Reviewed-on: https://go-review.googlesource.com/20355Reviewed-by: David Crawshaw <crawshaw@golang.org>

Passes toolstash -cmp.

Change-Id: Ie4675e6f713c3bbb90556f5347cbd7268a9c1a5d
Reviewed-on: https://go-review.googlesource.com/20357
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Passes toolstash -cmp.

Update #14473.

Change-Id: I2620374b79c61b1e48467b98afe2d7d3beef878b
Reviewed-on: https://go-review.googlesource.com/20354Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Without SSA:

$ go build -a -gcflags='-S -ssa=0' runtime 2>&1 | grep 'TEXT.*""\.init(SB)'
        0x0000 00000 ($GOROOT/src/runtime/write_err.go:14)        TEXT    "".init(SB), $88-0

With SSA, before this CL:

$ go build -a -gcflags='-S -ssa=1' runtime 2>&1 | grep 'TEXT.*""\.init(SB)'
        0x0000 00000 ($GOROOT/src/runtime/traceback.go:608)       TEXT    "".init(SB), $152-0

With SSA, after this CL:

$ go build -a -gcflags='-S -ssa=1' runtime 2>&1 | grep 'TEXT.*""\.init(SB)'
        0x0000 00000 ($GOROOT/src/runtime/write_err.go:14)        TEXT    "".init(SB), $152-0

Change-Id: Ida3541e03a1af6ffc753ee5c3abeb653459edbf6
Reviewed-on: https://go-review.googlesource.com/20321
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

The existing implementation deals with absolute relocations in __TEXT
for darwin/amd64 in build-mode c-shared, but it ignores c-archive.
This results in issues when trying to use a c-archive in an iOS
app on the 64-bit simulator. This patch adds c-archive to the
handling of this issue.

Fixes #14217

Change-Id: I2e4d5193caa531171ad22fd0cd420a8bfb4646a6
Reviewed-on: https://go-review.googlesource.com/19206Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Passes toolstash/buildall.

Fixes #14692.

Change-Id: I4352678d8251309f2b8b7793674c550fac948006
Reviewed-on: https://go-review.googlesource.com/20350Reviewed-by: Dave Cheney <dave@cheney.net>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

This adds a heap-based proper priority queue to the
scheduler which made a relatively easy to test quite a few
heuristics that "ought to work well".  For go tools
themselves (which may not be representative) the heuristic
that works best is (1) in line-number-order, then (2) from
more to fewer args, then (3) in variable ID order.  Trying
to improve this with information about use at end of
blocks turned out to be fruitless -- all of my naive
attempts at using that information turned out worse than
ignoring it.  I can confirm that the stores-early heuristic
tends to help; removing it makes the results slightly worse.

My metric is code size reduction, which I take to mean fewer
spills from register allocation.  It's not uniform.
Here's the endpoints for "vet" from one set of pretty-good
heuristics (this is representative at least).

-2208 time.parse 13472 15680 -14.081633%
-1514 runtime.pclntab 1002058 1003572 -0.150861%
-352 time.Time.AppendFormat 9952 10304 -3.416149%
-112 runtime.runGCProg 1984 2096 -5.343511%
-64 regexp/syntax.(*parser).factor 7264 7328 -0.873362%
-44 go.string.alldata 238630 238674 -0.018435%

48 math/big.(*Float).round 1376 1328 3.614458%
48 text/tabwriter.(*Writer).writeLines 1232 1184 4.054054%
48 math/big.shr 832 784 6.122449%
88 go.func.* 75174 75086 0.117199%
96 time.Date 1968 1872 5.128205%

Overall there appears to be an 0.1% decrease in text size.
No timings yet, and given the distribution of size reductions
it might make sense to wait on those.

addr2line  text (code) = -4392 bytes (-0.156273%)
api  text (code) = -5502 bytes (-0.147644%)
asm  text (code) = -5254 bytes (-0.187810%)
cgo  text (code) = -4886 bytes (-0.148846%)
compile  text (code) = -1577 bytes (-0.019346%) * changed
cover  text (code) = -5236 bytes (-0.137992%)
dist  text (code) = -5015 bytes (-0.167829%)
doc  text (code) = -5180 bytes (-0.182121%)
fix  text (code) = -5000 bytes (-0.215148%)
link  text (code) = -5092 bytes (-0.152712%)
newlink  text (code) = -5204 bytes (-0.196986%)
nm  text (code) = -4398 bytes (-0.156018%)
objdump  text (code) = -4582 bytes (-0.155046%)
pack  text (code) = -4503 bytes (-0.294287%)
pprof  text (code) = -6314 bytes (-0.085177%)
trace  text (code) = -5856 bytes (-0.097818%)
vet  text (code) = -5696 bytes (-0.117334%)
yacc  text (code) = -4971 bytes (-0.213817%)

This leaves me sorely tempted to look into a "real" scheduler
to try to do a better job, but I think it might make more
sense to look into getting loop information into the
register allocator instead.

Fixes #14577.

Change-Id: I5238b83284ce76dea1eb94084a8cd47277db6827
Reviewed-on: https://go-review.googlesource.com/20240
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

When the pointer offset is non-zero in the small loads, we need to add the offset
when converting to the larger load.

Fixes #14694

Change-Id: I5ba8bcb3b9ce26c7fae0c4951500b9ef0fed54cd
Reviewed-on: https://go-review.googlesource.com/20333Reviewed-by: Keith Randall <khr@golang.org>

Fixes #14486.
Related to #14485.

Change-Id: I2dd77b0337aebfe885ae828483deeaacb500b12a
Reviewed-on: https://go-review.googlesource.com/20340Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Currently, package obj reserves a range of 1<<12 opcodes for each
target architecture.  E.g., mips64 has [6<<12, 7<<12).

However, because mips.ABEQ and mips.ALAST are both within that range,
the expression mips.ABEQ+mips.ALAST in turn falls (far) outside that
range around 12<<12, meaning it could theoretically collide with
another arch's opcodes.

More practically, it's a problem because 12<<12 overflows an int16,
which hampers fixing #14692.  (We could also just switch to uint16 to
avoid the overflow, but that still leaves the first problem.)

As a workaround, use Michael Hudson-Doyle's solution from
https://golang.org/cl/20182 and use negative values for these variant
instructions.

Passes toolstash -cmp for GOARCH=arm and GOARCH=mips64.

Updates #14692.

Change-Id: Iad797d10652360109fa4db19d4d1edb6529fc2c0
Reviewed-on: https://go-review.googlesource.com/20345
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

This is needed now for subrepos to be able to conditionally use
API symbols found only after Go 1.6.

Change-Id: Ie7d9301332aa1739b585d93f8025424ae72a2430
Reviewed-on: https://go-review.googlesource.com/20344Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>