sysUnused (e.g., madvise MADV_FREE) is only sensible to call on
physical page boundaries, so scavengelist rounds in the bounds of the
region being released to the nearest physical page boundaries.
However, if the region is smaller than a physical page and neither the
start nor end fall on a boundary, then rounding the start up to a page
boundary and the end down to a page boundary will result in end < start.
Currently, we only give up on the region if start == end, so if we
encounter end < start, we'll call madvise with a negative length and
the madvise will fail.

Issue #16644 gives a concrete example of this:

    start = 0x1285ac000
    end   = 0x1285ae000 (1 8K page)

This leads to the rounded values

    start = 0x1285b0000
    end   = 0x1285a0000

which leads to len = -65536.

Fix this by giving up on the region if end <= start, not just if
end == start.

Fixes #16644.

Change-Id: I8300db492dbadc82ac1ad878318b36bcb7c39524
Reviewed-on: https://go-review.googlesource.com/27230Reviewed-by: Keith Randall <khr@golang.org>

fixes #16493

Change-Id: I86bec2f9bd7965449c43e94733791f7cb18c5c4c
Reviewed-on: https://go-review.googlesource.com/25165Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

Callers pass strings sliced as necessary instead of giving
an offset.

Fixes #16350

Change-Id: I7ba896f6ff09e0fd0094ca6c5af5d9a81622f15e
Reviewed-on: https://go-review.googlesource.com/27206
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Change-Id: Ib8855f8125970fc7ffb271635c28d31d310fcb5b
Reviewed-on: https://go-review.googlesource.com/27192
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Instead of making a runtime call, compare types and values.

Change-Id: Id302083d5a6a5f18e04f36f304f3d290c46976ad
Reviewed-on: https://go-review.googlesource.com/26660
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

When T is a scalar, there are no runtime calls
required, which makes this a clear win.

encoding/binary:
WriteInts-8                958ns ± 3%     864ns ± 2%   -9.80%  (p=0.000 n=15+15)

This also considerably shrinks a core fmt
routine:

Before: "".(*pp).printArg t=1 size=3952 args=0x20 locals=0xf0
After:  "".(*pp).printArg t=1 size=2624 args=0x20 locals=0x98

Unfortunately, I find it very hard to get stable
numbers out of the fmt benchmarks due to thermal scaling.

Change-Id: I1278006b030253bf8e48dc7631d18985cdaa143d
Reviewed-on: https://go-review.googlesource.com/26659
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Keith Randall <khr@golang.org>

This removes some scaffolding introduced pre-1.7, introduced to
fix an export format bug, and to minimize conflicts with older
formats. The currently deployed and recognized format is "v1",
so don't worry about other versions. This is a step towards a
better scheme for internal export format versioning.

For #16244.

Change-Id: Ic7cf99dd2a24ad5484cc54aed44fa09332c2cf72
Reviewed-on: https://go-review.googlesource.com/27205Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Robert Griesemer <gri@golang.org>

Removes the encoding of this bit which was ignored but left behind
for 1.7 to minimize pre-1.7 export format changes. See the issue
for more details.

Fixes #15772.

Change-Id: I46cd7a66ad4c6003b78c64295cf3bda503ebf2dd
Reviewed-on: https://go-review.googlesource.com/27201
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

Fixes #16156

Change-Id: I6989db4fd392583a2d490339cefc525b07c11b90
Reviewed-on: https://go-review.googlesource.com/24380Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: Andrew Gerrand <adg@golang.org>

s390x took up the last available chunk of int16 opcodes.
There are RISC-V and sparc64 ports in progress out of tree,
and there will likely be other architectures.
Reduce the opcode space to allow more architectures to
fit without increasing to int32.

This is the smallest power of two that accomodates all
existing architectures. All else being equal, smaller is
better--smaller numbers are easier to generate immediates
for and easier on the eyes when debugging.

Change-Id: I4d0824b28913892fbd0579d3f90bea34e44c8946
Reviewed-on: https://go-review.googlesource.com/24223
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>

Fixes #15323.

Change-Id: I50e996e6fde6b24327cb45dd84da31deef4dcc56
Reviewed-on: https://go-review.googlesource.com/27171
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

We should check whether there is a concurrent writer at the
start of every mapiternext, not just in mapaccessK (which is
only called during certain map growth situations).

Tests turned off by default because they are inherently flaky.

Fixes #16278

Change-Id: I8b72cab1b8c59d1923bec6fa3eabc932e4e91542
Reviewed-on: https://go-review.googlesource.com/24749Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

ssaMain is no longer needed.

Change-Id: I0b77f0bcd482329d73018bd80a6e068e622e191b
Reviewed-on: https://go-review.googlesource.com/27190Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Only need to zero-extend to 32 bits and we get the top
32 bits zeroed for free.

Only the WQ change actually generates different code.
The assembler did this optimization for us in the other two cases.
But we might as well do it during SSA so -S output more closely
matches the actual generated instructions.

Change-Id: I3e4ac50dc4da124014d4e31c86e9fc539d94f7fd
Reviewed-on: https://go-review.googlesource.com/23711
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

This CL adds a safety mechanism
for changing the number of opcodes
available per architecture.

A subsequent CL will actually make the change.

Change-Id: I6332ed5514f2f153c54d11b7da0cc8a6be1c8066
Reviewed-on: https://go-review.googlesource.com/24222
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Updates #16737

Change-Id: Ia51fc9b06df43b7c6f7136e90b40362263c20081
Reviewed-on: https://go-review.googlesource.com/27126Reviewed-by: Chris Broadfoot <cbro@golang.org>

Also includes a minor golint cleanup in the tests.

Change-Id: I8c0fc81479e635e7cca18d5c48c28b654afa59d8
Reviewed-on: https://go-review.googlesource.com/25380Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #16719.

Change-Id: I20550628814e3454f17d6f8ae8b66cce17f09859
Reviewed-on: https://go-review.googlesource.com/27118Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #16306

Change-Id: If8e2f411fe9a5a5c198f10765fee7261ba8feaf2
Reviewed-on: https://go-review.googlesource.com/24836
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

This only triggers a few places in the stdlib,
but it helps a lot when it does.

Before:

runtime.mapassign1 t=1 size=2400 args=0x20 locals=0xe0

After:

runtime.mapassign1 t=1 size=2352 args=0x20 locals=0xd8

name           old time/op  new time/op  delta
MapPop100-8    19.8µs ±11%  18.4µs ± 9%  -7.16%  (p=0.000 n=20+19)
MapPop1000-8    367µs ±17%   335µs ±11%  -8.63%  (p=0.000 n=19+19)
MapPop10000-8  7.29ms ±15%  6.86ms ±12%  -5.84%  (p=0.020 n=20+20)

Change-Id: I9faf32f95a6ba6a6d5d0818eab32cc271e01d10a
Reviewed-on: https://go-review.googlesource.com/26666
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

The frontend rewriting lowers them to runtime calls on 386. It
matches explicitly uint32, but missed uint.

Fixes #16738.

Change-Id: Iece7a45edf74615baca052a53273c208f057636d
Reviewed-on: https://go-review.googlesource.com/27085
Run-TryBot: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Might as well tell the runtime how large the map is going to be.
This avoids grow work and allocations while the map is being built.

Will wait for 1.8.

Fixes #15880
Fixes #16279

Change-Id: I377e3e5ec1e2e76ea2a50cc00810adda20ad0e79
Reviewed-on: https://go-review.googlesource.com/23558
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

Update #16415

Change-Id: I83e0966931ada2f1ed02304685bb45effdd71268
Reviewed-on: https://go-review.googlesource.com/26665
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

This CL teaches SSA to recognize code of the form

// b is a boolean value, i is an int of some flavor
if b {
	i = 1
} else {
	i = 0
}

and use b's underlying 0/1 representation for i
instead of generating jumps.

Unfortunately, it does not work on the obvious code:

func bool2int(b bool) int {
	if b {
		return 1
	}
	return 0
}

This is left for future work.
Note that the existing phiopt optimizations also don't work for:

func neg(b bool) bool {
	if b {
		return false
	}
	return true
}

In the meantime, runtime authors and the like can use:

func bool2int(b bool) int {
	var i int
	if b {
		i = 1
	} else {
		i = 0
	}
	return i
}

This compiles to:

"".bool2int t=1 size=16 args=0x10 locals=0x0
	0x0000 00000 (x.go:25)	TEXT	"".bool2int(SB), $0-16
	0x0000 00000 (x.go:25)	FUNCDATA	$0, gclocals·23e8278e2b69a3a75fa59b23c49ed6ad(SB)
	0x0000 00000 (x.go:25)	FUNCDATA	$1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
	0x0000 00000 (x.go:32)	MOVBLZX	"".b+8(FP), AX
	0x0005 00005 (x.go:32)	MOVBQZX	AL, AX
	0x0008 00008 (x.go:32)	MOVQ	AX, "".~r1+16(FP)
	0x000d 00013 (x.go:32)	RET

The extraneous MOVBQZX is #15300.

This optimization also helps range and slice.
The compiler must protect against pointers pointing
to the end of a slice/string. It does this by increasing
a pointer by either 0 or 1 * elemsize, based on a condition.
This CL optimizes away a jump in that code.

This CL triggers 382 times while compiling the standard library.

Updating code to utilize this optimization is left for future CLs.

Updates #6011

Change-Id: Ia7c1185f8aa223c543f91a3cd6d4a2a09c691c70
Reviewed-on: https://go-review.googlesource.com/22711
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

For #16369.

Change-Id: I4c9f5a66b95558adcc1bcface164b9b2b4382d2f
Reviewed-on: https://go-review.googlesource.com/24979Reviewed-by: Alan Donovan <adonovan@google.com>

Fixes #16722

Change-Id: I50a0e69d3e79d13bc1860cd983267c3db087a4b8
Reviewed-on: https://go-review.googlesource.com/27119Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Don't fold constant factors into a multiply
beyond the capacity of a MULQ instruction (32 bits).

Fixes #16733

Change-Id: Idc213c6cb06f7c94008a8cf9e60a9e77d085fd89
Reviewed-on: https://go-review.googlesource.com/27160
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

We already inlined

_, ok = e.(T)
_, ok = i.(E)
_, ok = e.(E)

The only ok-only variants not inlined are now

_, ok = i.(I)
_, ok = e.(I)

These call getitab, so are non-trivial.

Change-Id: Ie45fd8933ee179a679b92ce925079b94cff0ee12
Reviewed-on: https://go-review.googlesource.com/26658
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Now that assembler opcodes have their own type, they can have a true
stringer, rather than explicit calls to Aconv, which makes for nicer
format strings.

Change-Id: Ic77f5f8ac38b4e519dcaa08c93e7b732226f7bfe
Reviewed-on: https://go-review.googlesource.com/25045
Run-TryBot: Michael Pratt <mpratt@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

Pick up a bunch of changes and fixes.

Change-Id: If4101f7185d433a4c89096bc786ee5de8eeabac0
Reviewed-on: https://go-review.googlesource.com/27123
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

No functional changes, makes vet happy.

Updates #11041

Change-Id: I59f3aba46d19b86d605508978652d76a1fe7ac7b
Reviewed-on: https://go-review.googlesource.com/27125
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Makes vet happy.

Updates #11041

Change-Id: I23ca413c03ff387359440af8114786cd7880a048
Reviewed-on: https://go-review.googlesource.com/27124
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes (legit) vet warnings.
Fix some verb tenses while we're here.

Updates #11041

Change-Id: I27e995f55b38f4cf584e97a67b8545e8247e83d6
Reviewed-on: https://go-review.googlesource.com/27122
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

Give *recordingConn the correct WriteTo signature
to be an io.WriterTo. This makes vet happy.
It also means that it'll report errors,
which were previously being ignored.

Updates #11041

Change-Id: I13f171407d63f4b62427679bff362eb74faddca5
Reviewed-on: https://go-review.googlesource.com/27121
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Caught by vet.

Updates #11041

Change-Id: I4dbb2eeaf633eea5976074840064edc2349e01d8
Reviewed-on: https://go-review.googlesource.com/27120
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

container/list/list_test.go:274: self-assignment of e1 to e1
container/list/list_test.go:274: self-assignment of e4 to e4
container/list/list_test.go:282: self-assignment of e1 to e1
container/list/list_test.go:286: self-assignment of e1 to e1
container/list/list_test.go:286: self-assignment of e4 to e4

Updates #11041

Change-Id: Ibd90cf6a924e93497908f437b814c3fc82937f4a
Reviewed-on: https://go-review.googlesource.com/27114
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

CL 23393 introduces PAUTOHEAP, and access of PAUTOHEAP variable is
rewritten to indirection of a PAUTO variable. Mark this variable
non-nil, so this indirection does not introduce extra nil checks.

Change-Id: I31853eed5e60238b6c5bc0546e2e9ab340dcddd9
Reviewed-on: https://go-review.googlesource.com/26831
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

For tests, assign to _.
For benchmarks, assign to a sink.

Updates #11041

Change-Id: I87c5543245c7bc74dceb38902f4551768dd37948
Reviewed-on: https://go-review.googlesource.com/27116
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

We were generating format strings containing
a lone %. Vet legitimately complains:

cmd/compile/internal/gc/constFold_test.go:339: unrecognized printf verb ' '

The fix doesn't make for very readable code,
but it is simple and obviously correct.

Updates #11041

Change-Id: I90bd2d1d140887f5229752a279f7e46921472fbb
Reviewed-on: https://go-review.googlesource.com/27115
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Updates #11041

Change-Id: I77e5ca0b61ffc530ee46848721a177867c81d548
Reviewed-on: https://go-review.googlesource.com/25116
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>