No functional changes.
The intent is just to make this
easier to read and maintain.

Change-Id: Iec207546482cd62bcb22eaae8efe5be6c4f15378
Reviewed-on: https://go-review.googlesource.com/13284Reviewed-by: Keith Randall <khr@golang.org>

Change-Id: I402841743fcdc287631646039eb149f5cfdf886c
Reviewed-on: https://go-review.googlesource.com/13269Reviewed-by: Keith Randall <khr@golang.org>

regalloc expects to find all OpSP and OpSB values
in the entry block.

There is no value to moving them; don't.

Change-Id: I775198f03ce7420348721ffc5e7d2bab065465b1
Reviewed-on: https://go-review.googlesource.com/13266Reviewed-by: Keith Randall <khr@golang.org>

Change-Id: I2667b0923e17df7cbf08e34ebec1b69a0f2f02b2
Reviewed-on: https://go-review.googlesource.com/13265Reviewed-by: Keith Randall <khr@golang.org>

Given (say)

b1: <- b2 b3
  v1 = Phi <t> v2 v3
b2:
  v2 = ...
b3:
  ...

tighten will move v2 to b1, since it is only used in b1.

This is wrong; v2 needs to be evaluated before entering b1.
Fix it.

Change-Id: I2cc3b30e3ffd221cf594e36cec534dfd9cf3c6a7
Reviewed-on: https://go-review.googlesource.com/13264Reviewed-by: Keith Randall <khr@golang.org>

Even this very simple, restricted initial implementation helps.

While running make.bash, it moves 84437 values
to new, closer homes.

As a concrete example:

func f_ssa(i, j int, b bool) int {
	if !b {
		return 0
	}
	return i + j
}

It cuts off one stack slot and two instructions:

Before:

"".f_ssa t=1 size=96 value=0 args=0x20 locals=0x18
	0x0000 00000 (x.go:3)	TEXT	"".f_ssa(SB), $24-32
	0x0000 00000 (x.go:3)	SUBQ	$24, SP
	0x0004 00004 (x.go:3)	FUNCDATA	$0, "".gcargs·0(SB)
	0x0004 00004 (x.go:3)	FUNCDATA	$1, "".gclocals·1(SB)
	0x0004 00004 (x.go:5)	MOVQ	$0, AX
	0x0006 00006 (x.go:3)	MOVQ	32(SP), CX
	0x000b 00011 (x.go:3)	MOVQ	40(SP), DX
	0x0010 00016 (x.go:3)	LEAQ	48(SP), BX
	0x0015 00021 (x.go:3)	MOVB	(BX), BPB
	0x0018 00024 (x.go:3)	MOVQ	$0, SI
	0x001a 00026 (x.go:3)	MOVQ	SI, 56(SP)
	0x001f 00031 (x.go:3)	TESTB	BPB, BPB
	0x0022 00034 (x.go:5)	MOVQ	AX, (SP)
	0x0026 00038 (x.go:3)	MOVQ	CX, 8(SP)
	0x002b 00043 (x.go:3)	MOVQ	DX, 16(SP)
	0x0030 00048 (x.go:4)	JEQ	74
	0x0032 00050 (x.go:3)	MOVQ	8(SP), AX
	0x0037 00055 (x.go:3)	MOVQ	16(SP), CX
	0x003c 00060 (x.go:7)	LEAQ	(AX)(CX*1), DX
	0x0040 00064 (x.go:7)	MOVQ	DX, 56(SP)
	0x0045 00069 (x.go:3)	ADDQ	$24, SP
	0x0049 00073 (x.go:3)	RET
	0x004a 00074 (x.go:5)	MOVQ	(SP), AX
	0x004e 00078 (x.go:5)	MOVQ	AX, 56(SP)
	0x0053 00083 (x.go:3)	JMP	69

After:

"".f_ssa t=1 size=80 value=0 args=0x20 locals=0x10
	0x0000 00000 (x.go:3)	TEXT	"".f_ssa(SB), $16-32
	0x0000 00000 (x.go:3)	SUBQ	$16, SP
	0x0004 00004 (x.go:3)	FUNCDATA	$0, "".gcargs·0(SB)
	0x0004 00004 (x.go:3)	FUNCDATA	$1, "".gclocals·1(SB)
	0x0004 00004 (x.go:3)	MOVQ	32(SP), AX
	0x0009 00009 (x.go:3)	MOVQ	24(SP), CX
	0x000e 00014 (x.go:3)	LEAQ	40(SP), DX
	0x0013 00019 (x.go:3)	MOVB	(DX), BL
	0x0015 00021 (x.go:3)	MOVQ	$0, BP
	0x0017 00023 (x.go:3)	MOVQ	BP, 48(SP)
	0x001c 00028 (x.go:3)	TESTB	BL, BL
	0x001e 00030 (x.go:3)	MOVQ	AX, (SP)
	0x0022 00034 (x.go:3)	MOVQ	CX, 8(SP)
	0x0027 00039 (x.go:4)	JEQ	64
	0x0029 00041 (x.go:3)	MOVQ	8(SP), AX
	0x002e 00046 (x.go:3)	MOVQ	(SP), CX
	0x0032 00050 (x.go:7)	LEAQ	(AX)(CX*1), DX
	0x0036 00054 (x.go:7)	MOVQ	DX, 48(SP)
	0x003b 00059 (x.go:3)	ADDQ	$16, SP
	0x003f 00063 (x.go:3)	RET
	0x0040 00064 (x.go:5)	MOVQ	$0, AX
	0x0042 00066 (x.go:5)	MOVQ	AX, 48(SP)
	0x0047 00071 (x.go:3)	JMP	59

Of course, the old backend is still well ahead:

"".f_ssa t=1 size=48 value=0 args=0x20 locals=0x0
	0x0000 00000 (x.go:3)	TEXT	"".f_ssa(SB), $0-32
	0x0000 00000 (x.go:3)	NOP
	0x0000 00000 (x.go:3)	NOP
	0x0000 00000 (x.go:3)	FUNCDATA	$0, gclocals·a8eabfc4a4514ed6b3b0c61e9680e440(SB)
	0x0000 00000 (x.go:3)	FUNCDATA	$1, gclocals·33cdeccccebe80329f1fdbee7f5874cb(SB)
	0x0000 00000 (x.go:4)	CMPB	"".b+24(FP), $0
	0x0005 00005 (x.go:4)	JNE	17
	0x0007 00007 (x.go:5)	MOVQ	$0, "".~r3+32(FP)
	0x0010 00016 (x.go:5)	RET
	0x0011 00017 (x.go:7)	MOVQ	"".i+8(FP), BX
	0x0016 00022 (x.go:7)	MOVQ	"".j+16(FP), BP
	0x001b 00027 (x.go:7)	ADDQ	BP, BX
	0x001e 00030 (x.go:7)	MOVQ	BX, "".~r3+32(FP)
	0x0023 00035 (x.go:7)	RET

Some regalloc improvements should help considerably.

Change-Id: I95bb5dd83e56afd70ae4e983f1d32dffd0c3d46a
Reviewed-on: https://go-review.googlesource.com/13142Reviewed-by: Keith Randall <khr@golang.org>

Implement ITAB, selecting the itable field of an interface.

Soften the lowering check to allow lowerings that leave
generic but dead ops behind.  (The ITAB lowering does this.)

Change-Id: Icc84961dd4060d143602f001311aa1d8be0d7fc0
Reviewed-on: https://go-review.googlesource.com/13144Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

I find myself always adding this in temporarily.
Make it permanent.

Change-Id: I1646b3930a07d0ea01840736ccd449b7fd24f06e
Reviewed-on: https://go-review.googlesource.com/13141Reviewed-by: Keith Randall <khr@golang.org>

Failure to treat control ops as live can lead
to them being eliminated when they live in
other blocks.

Change-Id: I604a1977a3d3884b1f4516bea4e15885ce38272d
Reviewed-on: https://go-review.googlesource.com/13138Reviewed-by: Keith Randall <khr@golang.org>

They were being omitted after scheduling.

Change-Id: Ia20e2dcb61fde9ec854918b958c3897bafd282a6
Reviewed-on: https://go-review.googlesource.com/13140Reviewed-by: Keith Randall <khr@golang.org>

Don't put them in the control value's block.
That may be many blocks up the dominator tree.

Change-Id: Iab3ea36a890ffe0e355dadec7aeb676901c4f070
Reviewed-on: https://go-review.googlesource.com/13134Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

This is helpful when debugging generated code.

Change-Id: I268efa3593a03bb2c4e9f07d9034c004cd40df41
Reviewed-on: https://go-review.googlesource.com/13099Reviewed-by: Keith Randall <khr@golang.org>

Rewrite ^{n}x to be ^{n % 2}x.  This will eventually resolve a fuzz
issue that breaks v1.5.

Updates #11352

Change-Id: I1b3f93872d06222f9ff5f6fd5580178ebaf4c003
Reviewed-on: https://go-review.googlesource.com/13110Reviewed-by: Keith Randall <khr@golang.org>

Change-Id: Ibb5169aade15190773ff7dd11b303c1f1345a0c2
Reviewed-on: https://go-review.googlesource.com/13100Reviewed-by: Keith Randall <khr@golang.org>

The DFS scheduler doesn't do the right thing.  If a Value x is used by
more than one other Value, then x is put into the DFS queue when
its first user (call it y) is visited.  It is not removed and reinserted
when the second user of x (call it z) is visited, so the dependency
between x and z is not respected.  There is no easy way to fix this with
the DFS queue because we'd have to rip values out of the middle of the
DFS queue.

The new scheduler works from the end of the block backwards, scheduling
instructions which have had all of their uses already scheduled.
A simple priority scheme breaks ties between multiple instructions that
are ready to schedule simultaneously.

Keep track of whether we've scheduled or not, and make print() use
the scheduled order if we have.

Fix some shift tests that this change tickles.  Add unsigned right shift tests.

Change-Id: I44164c10bb92ae8ab8f76d7a5180cbafab826ea1
Reviewed-on: https://go-review.googlesource.com/13069Reviewed-by: Todd Neal <todd@tneal.org>

Reworks nilcheck to be performed by a depth first traversal of the
dominator tree, keeping an updated map of the values that have been
nil-checked during the traversal.

benchmark                           old ns/op     new ns/op     delta
BenchmarkNilCheckDeep1-8            1242          1825          +46.94%
BenchmarkNilCheckDeep10-8           2397          3942          +64.46%
BenchmarkNilCheckDeep100-8          29105         24873         -14.54%
BenchmarkNilCheckDeep1000-8         2742563       265760        -90.31%
BenchmarkNilCheckDeep10000-8        335690119     3157995       -99.06%

benchmark                           old MB/s     new MB/s     speedup
BenchmarkNilCheckDeep1-8            0.81         0.55         0.68x
BenchmarkNilCheckDeep10-8           4.17         2.54         0.61x
BenchmarkNilCheckDeep100-8          3.44         4.02         1.17x
BenchmarkNilCheckDeep1000-8         0.36         3.76         10.44x
BenchmarkNilCheckDeep10000-8        0.03         3.17         105.67x

benchmark                        old allocs     new allocs     delta
BenchmarkNilCheckDeep1-8         9              14             +55.56%
BenchmarkNilCheckDeep10-8        9              23             +155.56%
BenchmarkNilCheckDeep100-8       9              113            +1155.56%
BenchmarkNilCheckDeep1000-8      9              1015
+11177.78%
BenchmarkNilCheckDeep10000-8     9              10024
+111277.78%

benchmark                        old bytes     new bytes     delta
BenchmarkNilCheckDeep1-8         432           608           +40.74%
BenchmarkNilCheckDeep10-8        1008          1496          +48.41%
BenchmarkNilCheckDeep100-8       8064          11656         +44.54%
BenchmarkNilCheckDeep1000-8      73728         145240        +96.99%
BenchmarkNilCheckDeep10000-8     737280        2144411       +190.85%

Change-Id: I0f86010e9823aec04aac744fdb589b65ec8acefc
Reviewed-on: https://go-review.googlesource.com/12332Reviewed-by: David Chase <drchase@google.com>

Modify tests to use a known value instead of comparing the backends
directly.

Change-Id: I32e804e12515885bd94c4f83644cbca03b018fea
Reviewed-on: https://go-review.googlesource.com/13042Reviewed-by: Keith Randall <khr@golang.org>

This is a follow up on https://go-review.googlesource.com/#/c/12420/
with some rules moved to AMD64 closer to the existing rules.

Change-Id: Id346bb0fc4459b3c49b826a59cc74308a590310e
Reviewed-on: https://go-review.googlesource.com/12906Reviewed-by: Keith Randall <khr@golang.org>

This fixes the crypto/subtle tests.

Change-Id: Ie6e721eec3481f67f13de1bfbd7988e227793148
Reviewed-on: https://go-review.googlesource.com/13000Reviewed-by: Keith Randall <khr@golang.org>

The only types that remain in the ssa package
are special compiler-only types.

Change-Id: If957abf128ec0778910d67666c297f97f183b7ee
Reviewed-on: https://go-review.googlesource.com/12933Reviewed-by: Keith Randall <khr@golang.org>

Change-Id: I9cbb6d53a8c2302222b13d2f33b081b704208b8a
Reviewed-on: https://go-review.googlesource.com/12932Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Todd Neal <todd@tneal.org>

From compiling go there were 260 functions where XOR was needed.

Much of the required changes for implementing XOR were already
done in 12813.

Change-Id: I5a68aa028f5ed597bc1d62cedbef3620753dfe82
Reviewed-on: https://go-review.googlesource.com/12901Reviewed-by: Keith Randall <khr@golang.org>

The existing backend simply elides OCONVNOP.
There's no reason for us to do any differently.
Rather than insert ConvNops and then rewrite them
away, stop creating them in the first place.

Change-Id: I4bcbe2229fcebd189ae18df24f2c612feb6e215e
Reviewed-on: https://go-review.googlesource.com/12810Reviewed-by: Keith Randall <khr@golang.org>

Fix code generation error that resulted in a multi-argument NEGQ

doasm: notfound ft=13 tt=13 00134 NEGQ	AX, AX 13 13

Change-Id: I8b712d21a5523eccbae1f33ccea417844c27073e
Reviewed-on: https://go-review.googlesource.com/12869Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

Semi-regular merge from tip into ssa branch

Change-Id: Ida553b5c504058347c0bdcb1a987727bdcea456b

Was not allocating space for the frame above sigpanic,
nor was it pushing the LR into the right place.
Because traceback past sigpanic only needs the
LR for faulting leaves, this was not noticed too much.
But it did break the sync/atomic nil deref tests.

Change-Id: Icba53fffa193423aab744c37f21ee893ce2ee3ac
Reviewed-on: https://go-review.googlesource.com/12926Reviewed-by: David Crawshaw <crawshaw@golang.org>

Convert shift ops to also encode the size of the shift amount.

Change signed right shift from using CMOV to using bit twiddles.
It is a little bit better (5 instructions instead of 4, but fewer
bytes and slightly faster code).  It's also a bit faster than
the 4-instruction branch version, even with a very predictable
branch.  As tested on my machine, YMMV.

Implement OCOM while we are here.

Change-Id: I8ca12dd62fae5d626dc0e6da5d4bbd34fd9640d2
Reviewed-on: https://go-review.googlesource.com/12867Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

ODOTTYPE should be treated a whole lot like ODOT,
but it was missing completely from the switch in
escwalk and thus escape status did not propagate
to fields.

Since interfaces are required to trigger this bug,
the test was added to escape_iface.go.

Fixes #11931.

Change-Id: Id0383981cc4b1a160f6ad447192a112eed084538
Reviewed-on: https://go-review.googlesource.com/12921
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>

Missed somehow in #12813

Change-Id: I28f2789e33822a4ff884d8a3f474522747f61c73
Reviewed-on: https://go-review.googlesource.com/12868Reviewed-by: Keith Randall <khr@golang.org>

There is absolutely no information about how this was failing.
If we reenable the test then at least we can get a build log from
darwin/arm.

There are not even freebsd/arm or netbsd/arm builders,
so not too worried about those. (That is another problem.)

Change-Id: I0e739a4dd2897adbe110aa400d720d8fa02ae65f
Reviewed-on: https://go-review.googlesource.com/12920Reviewed-by: Russ Cox <rsc@golang.org>

Instead of pushing the denominator argument on the stack,
the denominator is now passed in m.

This fixes a variety of bugs related to trying to take stack traces
backwards from the middle of the software div/mod routines.
Some of those bugs have been kludged around in the past,
but others have not. Instead of trying to patch up after breaking
the stack, this CL stops breaking the stack.

This is an update of https://golang.org/cl/19810043,
which was rolled back in https://golang.org/cl/20350043.

The problem in the original CL was that there were divisions
at bad times, when m was not available. These were divisions
by constant denominators, either in C code or in assembly.
The Go compiler knows how to generate division by multiplication
for constant denominators, but the C compiler did not.
There is no longer any C code, so that's taken care of.
There was one problematic DIV in runtime.usleep (assembly)
but https://golang.org/cl/12898 took care of that one.
So now this approach is safe.

Reject DIV/MOD in NOSPLIT functions to keep them from
coming back.

Fixes #6681.
Fixes #6699.
Fixes #10486.

Change-Id: I09a13c76ad08ba75b3bd5d46a3eb78e66a84ab38
Reviewed-on: https://go-review.googlesource.com/12899Reviewed-by: Ian Lance Taylor <iant@golang.org>

In order to fix issue #9401 the compiler was changed to add a padding
byte to any non-empty Go struct that ends in a zero-sized field.  That
causes the Go version of such a C struct to have a different size than
the C struct, which can considerable confusion.  Change cgo so that it
discards any such zero-sized fields, so that the Go and C structs are
the same size.

This is a change from previous releases, in that it used to be
possible to refer to a zero-sized trailing field (by taking its
address), and with this change it no longer is.  That is unfortunate,
but something has to change.  It seems better to visibly break
programs that do this rather than to silently break programs that rely
on the struct sizes being the same.

Update #9401.
Fixes #11925.

Change-Id: I3fba3f02f11265b3c41d68616f79dedb05b81225
Reviewed-on: https://go-review.googlesource.com/12864Reviewed-by: Russ Cox <rsc@golang.org>

We want to adjust the DIV calling convention to use m,
and usleep can be called without an m, so switch to a
multiplication by the reciprocal (and test).

Step toward a fix for #6699 and #10486.

Change-Id: Iccf76a18432d835e48ec64a2fa34a0e4d6d4b955
Reviewed-on: https://go-review.googlesource.com/12898Reviewed-by: Ian Lance Taylor <iant@golang.org>

If a function is large enough to need to flush the constant pool
mid-function, the line number assignment code was forcing the
line numbers not just for the constant pool but for all the instructions
that follow it. This made the line number information completely
wrong for all but the beginning of large functions on arm.

Same problem in code copied into arm64.

This broke runtime/trace's TestTraceSymbolize.

Fixes arm build.

Change-Id: I84d9fb2c798c4085f69b68dc766ab4800c7a6ca4
Reviewed-on: https://go-review.googlesource.com/12894Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>

This allows running a cross-compile like
	GOOS=darwin GOARCH=arm go build std
to check that everything builds.

Otherwise there is a redefinition error because both
root_nocgo_darwin.go and root_darwin_armx.go
supply initSystemRoots.

Change-Id: Ic95976b2b698d28c629bfc93d8dac0048b023578
Reviewed-on: https://go-review.googlesource.com/12897Reviewed-by: Ian Lance Taylor <iant@golang.org>

The test expects the dial to take 1.0 seconds
on Windows and allows it to go to 1.095 seconds.
That's far too optimistic.
Recent failures are reporting roughly 1.2 seconds.
Let it have 1.5.

Change-Id: Id69811ccb65bf4b4c159301a2b4767deb6ee8d28
Reviewed-on: https://go-review.googlesource.com/12895Reviewed-by: Ian Lance Taylor <iant@golang.org>

Urge users of math/rand to consider using crypto/rand when doing
security-sensitive work.

Related to issue #11871. While we haven't reached consensus on how
to make the package inherently safer, everyone agrees that the docs
for math/rand can be improved.

Change-Id: I576a312e51b2a3445691da6b277c7b4717173197
Reviewed-on: https://go-review.googlesource.com/12900Reviewed-by: Rob Pike <r@golang.org>

For the android/arm builder.

Change-Id: Iad4881689223cd6479870da9541524a8cc458cce
Reviewed-on: https://go-review.googlesource.com/12859Reviewed-by: Andrew Gerrand <adg@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>

Fixes arm64 builder crash.

The bug is possible on all architectures; you just have to get lucky
and hit a preemption or a stack growth on entry to assertE2I2.
The test stacks the deck.

Change-Id: I8419da909b06249b1ad15830cbb64e386b6aa5f6
Reviewed-on: https://go-review.googlesource.com/12890Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

It says to disable until #7564 is fixed. It was fixed in April 2014.

Change-Id: I9bebfe96802bafdd2d1a0a47591df346d91b000c
Reviewed-on: https://go-review.googlesource.com/12858
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>