These instructions are the same as BLT and BLE except that they
also branch if the 'unordered' bit is set in the condition code.

They are already used by the SSA backend. This change allows them
to be used in hand-written assembly code.

Change-Id: Ie9b5985a5e87ea22e8043567a286e09dce16a2db
Reviewed-on: https://go-review.googlesource.com/29930
Run-TryBot: Michael Munday <munday@ca.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bill O'Farrell <billotosyr@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Use the A{,G}HI instructions where possible (4 bytes instead of 6 bytes
for A{,G}FI). Also, use 32-bit operations where appropriate for
multiplication.

Change-Id: I4041781cda26be52b54e4804a9e71552310762d0
Reviewed-on: https://go-review.googlesource.com/29733
Run-TryBot: Michael Munday <munday@ca.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bill O'Farrell <billotosyr@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Use an MVC loop to copy arguments in runtime.call* rather than copying
bytes individually.

I've added the benchmark CallArgCopy to test the speed of Value.Call
for various argument sizes.

name                    old speed      new speed       delta
CallArgCopy/size=128     439MB/s ± 1%    582MB/s ± 1%   +32.41%  (p=0.000 n=10+10)
CallArgCopy/size=256     695MB/s ± 1%   1172MB/s ± 1%   +68.67%  (p=0.000 n=10+10)
CallArgCopy/size=1024    573MB/s ± 8%   4175MB/s ± 2%  +628.11%  (p=0.000 n=10+10)
CallArgCopy/size=4096   1.46GB/s ± 2%  10.19GB/s ± 1%  +600.52%  (p=0.000 n=10+10)
CallArgCopy/size=65536  1.51GB/s ± 0%  12.30GB/s ± 1%  +716.30%   (p=0.000 n=9+10)

Change-Id: I87dae4809330e7964f6cb4a9e40e5b3254dd519d
Reviewed-on: https://go-review.googlesource.com/28096
Run-TryBot: Michael Munday <munday@ca.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bill O'Farrell <billotosyr@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: I9b2e6c45f7e83543a06d0aafd08a911f7b6485fd
Reviewed-on: https://go-review.googlesource.com/29874Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

When allocating registers, before kicking out the existing value,
copy it to a spare register if there is one. So later use of this
value can be found in register instead of reload from spill. This
is very helpful for instructions of which the input and/or output
can only be in specific registers, e.g. DIV on x86, MUL/DIV on
MIPS. May also be helpful in general.

For "go build -a cmd/go" on AMD64, reduce "spilled value remains"
by 1% (not including args, which almost certainly remain).

For the code in issue #16061 on AMD64:
MaxRem-12   111µs ± 1%    94µs ± 0%  -15.38%  (p=0.008 n=5+5)

Go1 benchmark on AMD64:
BinaryTree17-12              2.32s ± 2%     2.30s ± 1%    ~     (p=0.421 n=5+5)
Fannkuch11-12                2.52s ± 0%     2.44s ± 0%  -3.44%  (p=0.008 n=5+5)
FmtFprintfEmpty-12          39.9ns ± 3%    39.8ns ± 0%    ~     (p=0.635 n=5+4)
FmtFprintfString-12          114ns ± 1%     113ns ± 1%    ~     (p=0.905 n=5+5)
FmtFprintfInt-12             102ns ± 6%      98ns ± 1%    ~     (p=0.087 n=5+5)
FmtFprintfIntInt-12          146ns ± 5%     147ns ± 1%    ~     (p=0.238 n=5+5)
FmtFprintfPrefixedInt-12     155ns ± 2%     151ns ± 1%  -2.58%  (p=0.008 n=5+5)
FmtFprintfFloat-12           231ns ± 1%     232ns ± 1%    ~     (p=0.286 n=5+5)
FmtManyArgs-12               657ns ± 1%     649ns ± 0%  -1.31%  (p=0.008 n=5+5)
GobDecode-12                6.35ms ± 0%    6.29ms ± 1%    ~     (p=0.056 n=5+5)
GobEncode-12                5.38ms ± 1%    5.45ms ± 1%    ~     (p=0.056 n=5+5)
Gzip-12                      209ms ± 0%     209ms ± 1%    ~     (p=0.690 n=5+5)
Gunzip-12                   31.2ms ± 1%    31.1ms ± 1%    ~     (p=0.548 n=5+5)
HTTPClientServer-12          123µs ± 4%     130µs ± 8%    ~     (p=0.151 n=5+5)
JSONEncode-12               14.0ms ± 1%    14.0ms ± 1%    ~     (p=0.421 n=5+5)
JSONDecode-12               41.2ms ± 1%    41.1ms ± 2%    ~     (p=0.421 n=5+5)
Mandelbrot200-12            3.96ms ± 1%    3.98ms ± 0%    ~     (p=0.421 n=5+5)
GoParse-12                  2.88ms ± 1%    2.88ms ± 1%    ~     (p=0.841 n=5+5)
RegexpMatchEasy0_32-12      68.0ns ± 3%    66.6ns ± 1%  -2.00%  (p=0.024 n=5+5)
RegexpMatchEasy0_1K-12       728ns ± 8%     682ns ± 1%  -6.26%  (p=0.008 n=5+5)
RegexpMatchEasy1_32-12      66.8ns ± 2%    66.0ns ± 1%    ~     (p=0.302 n=5+5)
RegexpMatchEasy1_1K-12       291ns ± 2%     288ns ± 1%    ~     (p=0.111 n=5+5)
RegexpMatchMedium_32-12      103ns ± 2%     100ns ± 0%  -2.53%  (p=0.016 n=5+4)
RegexpMatchMedium_1K-12     31.9µs ± 1%    31.3µs ± 0%  -1.75%  (p=0.008 n=5+5)
RegexpMatchHard_32-12       1.59µs ± 2%    1.59µs ± 1%    ~     (p=0.548 n=5+5)
RegexpMatchHard_1K-12       48.3µs ± 2%    47.7µs ± 1%    ~     (p=0.222 n=5+5)
Revcomp-12                   340ms ± 1%     338ms ± 1%    ~     (p=0.421 n=5+5)
Template-12                 46.3ms ± 1%    46.5ms ± 1%    ~     (p=0.690 n=5+5)
TimeParse-12                 252ns ± 1%     247ns ± 0%  -1.91%  (p=0.000 n=5+4)
TimeFormat-12                277ns ± 1%     267ns ± 0%  -3.82%  (p=0.008 n=5+5)
[Geo mean]                  48.8µs         48.3µs       -0.93%

It has very little effect on binary size and compiler speed.
compilebench:
Template       230ms ±10%      231ms ± 8%    ~             (p=0.546 n=9+9)
Unicode        123ms ± 6%      124ms ± 9%    ~           (p=0.481 n=10+10)
GoTypes        742ms ± 6%      755ms ± 3%    ~           (p=0.123 n=10+10)
Compiler       3.10s ± 3%      3.08s ± 1%    ~           (p=0.631 n=10+10)

Fixes #16061.

Change-Id: Id99cdc7a182ee10a704fa0f04e8e0d0809b2ac56
Reviewed-on: https://go-review.googlesource.com/29732
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

Change-Id: I8984eac30e5df78d4b94f19412135d3cc36969f8
Reviewed-on: https://go-review.googlesource.com/29910
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

Compression of paletted images is more efficient if they are not filtered.
This patch skips filtering for cbP8 images.
The improvements are demonstrated at https://github.com/olt/compressbench

Fixes #16196

Change-Id: Ie973aad287cacf9057e394bb01cf0e4448a77618
Reviewed-on: https://go-review.googlesource.com/29872Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Realign multi-line comments that got misaligned by the c->go
conversion.

Change-Id: I584b902e95cf588aa14febf1e0b6dfa499c303c2
Reviewed-on: https://go-review.googlesource.com/29871Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: Idffb82cdcba4985954d061bdb021217f47ff4985
Reviewed-on: https://go-review.googlesource.com/29850Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #16984

Change-Id: I3a330e82941a068ca6097985af4ab221275fd336
Reviewed-on: https://go-review.googlesource.com/29299
Run-TryBot: Adam Langley <agl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Adam Langley <agl@golang.org>

This optimizes deferproc and deferreturn in various ways.

The most important optimization is that it more carefully arranges to
prevent preemption or stack growth. Currently we do this by switching
to the system stack on every deferproc and every deferreturn. While we
need to be on the system stack for the slow path of allocating and
freeing defers, in the common case we can fit in the nosplit stack.
Hence, this change pushes the system stack switch down into the slow
paths and makes everything now exposed to the user stack nosplit. This
also eliminates the need for various acquirem/releasem pairs, since we
are now preventing preemption by preventing stack split checks.

As another smaller optimization, we special case the common cases of
zero-sized and pointer-sized defer frames to respectively skip the
copy and perform the copy in line instead of calling memmove.

This speeds up the runtime defer benchmark by 42%:

name           old time/op  new time/op  delta
Defer-4        75.1ns ± 1%  43.3ns ± 1%  -42.31%   (p=0.000 n=8+10)

In reality, this speeds up defer by about 2.2X. The two benchmarks
below compare a Lock/defer Unlock pair (DeferLock) with a Lock/Unlock
pair (NoDeferLock). NoDeferLock establishes a baseline cost, so these
two benchmarks together show that this change reduces the overhead of
defer from 61.4ns to 27.9ns.

name           old time/op  new time/op  delta
DeferLock-4    77.4ns ± 1%  43.9ns ± 1%  -43.31%  (p=0.000 n=10+10)
NoDeferLock-4  16.0ns ± 0%  15.9ns ± 0%   -0.39%    (p=0.000 n=9+8)

This also shaves 34ns off cgo calls:

name       old time/op  new time/op  delta
CgoNoop-4   122ns ± 1%  88.3ns ± 1%  -27.72%  (p=0.000 n=8+9)

Updates #14939, #16051.

Change-Id: I2baa0dea378b7e4efebbee8fca919a97d5e15f38
Reviewed-on: https://go-review.googlesource.com/29656Reviewed-by: Keith Randall <khr@golang.org>

This makes it possible to inline getcallersp. getcallersp is on the
hot path of defers, so this slightly speeds up defer:

name           old time/op  new time/op  delta
Defer-4        78.3ns ± 2%  75.1ns ± 1%  -4.00%   (p=0.000 n=9+8)

Updates #14939.

Change-Id: Icc1cc4cd2f0a81fc4c8344432d0b2e783accacdd
Reviewed-on: https://go-review.googlesource.com/29655
TryBot-Result: Gobot Gobot <gobot@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

The big documentation comment at the top of malloc.go has gotten
woefully out of date. Update it.

Change-Id: Ibdb1bdcfdd707a6dc9db79d0633a36a28882301b
Reviewed-on: https://go-review.googlesource.com/29731Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Reviewed-by: Rick Hudson <rlh@golang.org>

This documents all fields in MemStats and more clearly documents where
mstats differs from MemStats.

Fixes #15849.

Change-Id: Ie09374bcdb3a5fdd2d25fe4bba836aaae92cb1dd
Reviewed-on: https://go-review.googlesource.com/28972Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

We used to compute an estimate of the reachable heap size that was
different from the marked heap size. This ultimately caused more
problems than it solved, so we pulled it out, but memstats still has
both heap_reachable and heap_marked, and there are some leftover TODOs
about the problems with this estimate.

Clean this up by eliminating heap_reachable in favor of heap_marked
and deleting the stale TODOs.

Change-Id: I713bc20a7c90683d2b43ff63c0b21a440269cc4d
Reviewed-on: https://go-review.googlesource.com/29271
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>

Back in Go 1.4, memstats.next_gc was both the heap size at which GC
would trigger, and the size GC kept the heap under. When we switched
to concurrent GC in Go 1.5, we got somewhat confused and made this
variable the trigger heap size, while gcController.heapGoal became the
goal heap size.

memstats.next_gc is exposed to the user via MemStats.NextGC, while
gcController.heapGoal is not. This is unfortunate because 1) the heap
goal is far more useful for diagnostics, and 2) the trigger heap size
is just part of the GC trigger heuristic, which means it wouldn't be
useful to an application even if it tried to use it.

We never noticed this mess because MemStats.NextGC is practically
undocumented. Now that we're trying to document MemStats, it became
clear that this field had diverged from its original usefulness.

Clean up this mess by shuffling things back around so that next_gc is
the goal heap size and the new (unexposed) memstats.gc_trigger field
is the trigger heap size. This eliminates gcController.heapGoal.

Updates #15849.

Change-Id: I2cbbd43b1d78bdf613cb43f53488bd63913189b7
Reviewed-on: https://go-review.googlesource.com/29270
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Reviewed-by: Rick Hudson <rlh@golang.org>

Fixes #17222.

Change-Id: Iffffc8cbb8627d06afa9066246b68fa2da4600e3
Reviewed-on: https://go-review.googlesource.com/29810Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

Fixes #16963.

Change-Id: Iaadf0da4ee9cc97146c5e6ac2d93de9ae6893880
Reviewed-on: https://go-review.googlesource.com/29790Reviewed-by: Matthew Dempsky <mdempsky@google.com>

Change-Id: I2cbb13eb85876ad05a52cbd498a9b86e7a28899c
Reviewed-on: https://go-review.googlesource.com/29772
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #17221

Change-Id: Idaa2af6b8646651ea72195671d1a4b5c370a5a22
Reviewed-on: https://go-review.googlesource.com/29711Reviewed-by: Robert Griesemer <gri@golang.org>

All the variants that sets the new signal mask in minit do the same
thing, so merge them. This requires an OS-specific sigdelset function;
the function already exists for linux, and is now added for other OS's.

Change-Id: Ie96f6f02e2cf09c43005085985a078bd9581f670
Reviewed-on: https://go-review.googlesource.com/29771
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Added rules for compare double and word immediate,
including those that use invertflags to cope with
flipped operands.

Change-Id: I594430a210e076e52299a2cc6ab074dbb04a02bd
Reviewed-on: https://go-review.googlesource.com/29763
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>

Fixes #16439
Updates #16679

Change-Id: Idff4b313f29351866b1a649786501adee85fd580
Reviewed-on: https://go-review.googlesource.com/29011
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

Combine the various versions of sigtrampgo into a single function in
signal_unix.go. This requires defining a fixsigcode method on sigctxt
for all operating systems; it only does something on Darwin. This also
requires changing the darwin/amd64 signal handler to call sigreturn
itself, rather than relying on sigtrampgo to call sigreturn for it. We
can then drop the Darwin sigreturn function, as it is no longer used.

Change-Id: I5a0b9d2d2c141957e151b41e694efeb20e4b4b9a
Reviewed-on: https://go-review.googlesource.com/29761
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

There's no load-signed-byte on PPC, so MOVB
causes the assembler to macro-expand in a
useless sign extension.

Fixes #17211.

Change-Id: Ibcd73aea4c94ba6df0a998b0091e45508113be2a
Reviewed-on: https://go-review.googlesource.com/29762
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Munday <munday@ca.ibm.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

When processing a fallthrough, the casebody function in swt.go
checks that the last statement has indeed Op == OXFALL (not-processed
fallthrough) before setting it to OFALL (processed fallthrough).

Unfortunately, sometimes the fallthrough statement won't be in the
last node. For example, in

case 0:
	 return func() int {return 1}()
	 fallthrough

the compiler generates

autotmp_0 = (func literal)(); return autotmp_0; fallthrough; <node VARKILL>

with an OVARKILL node in the last position. casebody will find that
last.Op != OXFALL, won't mark the fallthrough as processed, and the
fallthrough line will cause a "fallthrough statement out of place" error.

To fix this, we change casebody so that it searches for the fallthrough
statement backwards in the statements list, without assuming that it'll
be in the last position.

Fixes #13262

Change-Id: I366c6caa7fd7442d365bd7a08cc66a552212d9b2
Reviewed-on: https://go-review.googlesource.com/22921
Run-TryBot: Quentin Smith <quentin@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Quentin Smith <quentin@golang.org>

Change all Unix systems to use stackt for the alternate signal
stack (some were using sigaltstackt). Add OS-specific setSignalstackSP
function to handle different types for ss_sp field, and unify all
OS-specific signalstack functions into one. Unify handling of alternate
signal stack in OS-specific minit and sigtrampgo functions via new
functions minitSignalstack and setGsignalStack.

Change-Id: Idc316dc69b1dd725717acdf61a1cd8b9f33ed174
Reviewed-on: https://go-review.googlesource.com/29757
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Updates #13994
Updates #16840

Change-Id: Ia3cad5c211e0c688a945ed6b6277c2552592774c
Reviewed-on: https://go-review.googlesource.com/29760
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

To prevent slice growths with append operations.

Change-Id: Icdb745b23cc44dfaf3e16746b94c06997f814e15
Reviewed-on: https://go-review.googlesource.com/23784Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Change-Id: I894a8f49d29dbb6f9265e4b3df5767318b225460
Signed-off-by: Antonio Murdaca <runcom@redhat.com>
Reviewed-on: https://go-review.googlesource.com/24492Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #16678

Change-Id: I48c2825d4fef55a75d2f99640a7079c56fce39db
Reviewed-on: https://go-review.googlesource.com/28370Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Add a method to expose the handler to allow it to be installed at a
non-standard location or used with a different ServeMux.

fixes #15030

Change-Id: If778ad6fcc200f124a05c0a493511e364fca6078
Reviewed-on: https://go-review.googlesource.com/24722Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Implement a comment by Ralph Corderoy on CL 29754.

Change-Id: I22bbede211ddcb8a057f16b4f47d335a156cc8d2
Reviewed-on: https://go-review.googlesource.com/29756
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: Iba541045b4878405834c637095627631b6559a35
Reviewed-on: https://go-review.googlesource.com/29754
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Currently raceSymbolizeCode uses funcline, which is internal runtime
function which crashes on incorrect PCs. Use FileLine instead,
it is public and does not crash on invalid data.

Note: FileLine returns "?" file on failure. That string is not NUL-terminated,
so we need to additionally check what FileLine returns.

Fixes #17190

Change-Id: Ic6fbd4f0e68ddd52e9b2dd25e625b50adcb69a98
Reviewed-on: https://go-review.googlesource.com/29714
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Don't write line info for types, we don't have it.
Otherwise types look like:

type _Ctype_struct_cb struct {
//line :1
      on_test *[0]byte
//line :1
}

Which is not useful. Moreover we never override source info,
so subsequent source code uses the same source info.
Moreover, empty file name makes compile emit no source debug info at all.

Update #17190

Change-Id: I7ae6fa4964520d7665743d340419b787df0b51e8
Reviewed-on: https://go-review.googlesource.com/29713
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

PC passed to racegostart is expected to be a return PC
of the go statement. Race runtime will subtract 1 from the PC
before symbolization. Passing start PC of a function is wrong.
Add sys.PCQuantum to the function start PC.

Update #17190

Change-Id: Ia504c49e79af84ed4ea360c2aea472b370ea8bf5
Reviewed-on: https://go-review.googlesource.com/29712
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

This sentence is partially guilty why httptrace is considered as an
http.Client tracing package. Removing the mention.

Updates #17152.

Change-Id: I69f78a6e10817db933f44e464a949ae896e44ec6
Reviewed-on: https://go-review.googlesource.com/29755Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Replace all the Unix sighandler functions with a single instance.
Push the relatively small amount of processor-specific code into five
methods on sigctxt: sigpc, sigsp, siglr, fault, preparePanic.
(Some processors already had a fault method.)

Change-Id: Ib459412ff8f7e0f5ad06bfd43eb827c8b196fc32
Reviewed-on: https://go-review.googlesource.com/29752
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

Fixes #17164

Change-Id: I3e626d92293c1379e2922276f033fdee6f48dda3
Reviewed-on: https://go-review.googlesource.com/29753Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>