Also:
- make representation more flexible (no need to store trailing 0 digits to match precision)
- simplify rounding as a consequence
- minor related fixes

TBR adonovan

Change-Id: Ie91075990688b506d28371ec3b633b8267397ebb
Reviewed-on: https://go-review.googlesource.com/4841Reviewed-by: Rob Pike <r@golang.org>

TBR adonovan

Change-Id: If77afa6474af6cad6512f6866725e3ae5acf2e3f
Reviewed-on: https://go-review.googlesource.com/4840Reviewed-by: Robert Griesemer <gri@golang.org>

Per the comment at top, this test is about whether the GC runs during
init, but it was testing more than that, and testing how much the GC
collected in a certain amount of time.

Instead, loosen this test to just see whether it ran at all and not
how well it did.

Fixes #9848

Change-Id: I31da7dd769140d7b49aa6c149a543fae6076aa5e
Reviewed-on: https://go-review.googlesource.com/4820Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

In CL 4050, NULL was used instead of nil.
However, Plan 9 doesn't declare NULL.

Change-Id: I8295a3102509a1ce417278f23a37cbf65938cce1
Reviewed-on: https://go-review.googlesource.com/4814Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

Android apps build again.

Defining TLSG in runtime/tls_arm.s gives it the type SNOPTRBSS, so its
type was never being set when GOOS=android. I considered modifying the
if statement, but I no longer understand the intention of the original
change (in d738c6b0). We were always setting it before, what
platform is this not valid for?

Fixes #9829

Change-Id: I3eaa4a9590893eff67695797eb22547a170cdbcd
Reviewed-on: https://go-review.googlesource.com/4834Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Run-TryBot: David Crawshaw <crawshaw@golang.org>

--preserve flag is not a valid flag for some versions of cp.

Change-Id: I57f5bf21cbe726057fdadcd55b040ef7ff5d7479
Reviewed-on: https://go-review.googlesource.com/4835Reviewed-by: David Crawshaw <crawshaw@golang.org>

Fixes #9802.

Change-Id: I22c52a37bdb23a14cc4615c9519431bb14ca81ca
Reviewed-on: https://go-review.googlesource.com/4170Reviewed-by: Ian Lance Taylor <iant@golang.org>

Make cmd/ld a real library invoked by the individual linkers.
There are no reverse symbol references anymore
(symbols referred to in cmd/ld but defined in cmd/5l etc).

This means that in principle we could do an automatic
conversion of these to Go, as a stopgap until cmd/link is done
or as a replacement for cmd/link.

Change-Id: I4a94570257a3a7acc31601bfe0fad9dea0aea054
Reviewed-on: https://go-review.googlesource.com/4649Reviewed-by: Rob Pike <r@golang.org>

Change-Id: I2db4db852492eaddaf09dd7bae2fbd49f916e78a
Reviewed-on: https://go-review.googlesource.com/4648Reviewed-by: Rob Pike <r@golang.org>

- remove a few uses of ? :
- rename variables named len
- rewrite a few gotos as nested switches
- move goto targets to scope allowed by Go
- use consistent return type of anyregalloc
  (was int or int32 in different places)
- remove unused nr variable in agen
- include proper headers in generated builtin1.c
- avoid strange sized %E formats (%-6E, %2E)
- change gengcmask argument from uint8[16] to uint8*
  (diagnosed by c2go; not an array in any real sense).
- replace #ifdef XXX with comment block in 5g/peep.c
- expand and remove FAIL macro from 5g
- expand and remove noimpl macro from 9g
- print regalloc errors to stdout in 8g
  (only use of fprint(2, ...) in all compilers)

Still producing bit-for-bit identical output.

Change-Id: Id46efcd2a89241082b234f63f375b66f2754d695
Reviewed-on: https://go-review.googlesource.com/4646Reviewed-by: Austin Clements <austin@google.com>

In mparith, all the a1-- are problematic. Rewrite it all without pointers.
It's clearer anyway.

In popt, v is problematic because it is used both as a fixed pointer
(v = byvar[i]) and as a moving pointer (v = var; v++) aka slice.
Eliminate pointer movement.

Tested that this still produces bit-for-bit output for 'go build -a std'
compared to d260756 (current master).

Change-Id: I1a1bed0f98b594c3864fe95075dd95f9b52113e0
Reviewed-on: https://go-review.googlesource.com/4645Reviewed-by: Austin Clements <austin@google.com>

Otherwise the exported variable collides with the type Arch.

While we're here, remove arch.dumpit (now in portable code)
and add arch.defframe (forgotten originally, somehow).

Change-Id: I1b3a7dd7e96c5f632dba7cd6c1217b42a2004d72
Reviewed-on: https://go-review.googlesource.com/4644Reviewed-by: Austin Clements <austin@google.com>

If the Go source says x.y, and x is undefined, today we get

	undefined: x

Change to:

	undefined: x in x.y

Change-Id: I8ea95503bd469ea933c6bcbd675b7122a5d454f3
Reviewed-on: https://go-review.googlesource.com/4643Reviewed-by: Austin Clements <austin@google.com>

Even with debugmerge = 1, the debugging output only happens
with the -v command-line flag. This is useful because it gets added
in automatically when debugging things like registerization with -R -v.

Change-Id: I9a5c7f562507b72e8e2fe2686fd07d069721345a
Reviewed-on: https://go-review.googlesource.com/4641Reviewed-by: Austin Clements <austin@google.com>

Change-Id: I36f77e7ac7f727d8f3b51133f4b3ef93c35b09f6
Reviewed-on: https://go-review.googlesource.com/4640Reviewed-by: Austin Clements <austin@google.com>

Noticed last week.
Just saw a strange build failure in the revised rcmp (called by qsort on region)
and this fixed it.

Submitting first to avoid finding out which of my pending CLs tickled the
problem.

Change-Id: I4cafd611e2bf8e813e57ad0025e48bde5ae54359
Reviewed-on: https://go-review.googlesource.com/4830Reviewed-by: Russ Cox <rsc@golang.org>

When the compiler echoes back an expression, it shows the
generated yacc expression. Change the generated code to
use a slice so that $3 shows up as yyDollar[3] in such messages.

Consider changing testdata/expr/expr.y to say:

	$$.Sub(float64($1), $3)

(The float64 conversion is incorrect.)

Before:
expr.y:70[expr.go:486]: cannot convert exprS[exprpt - 2].num (type *big.Rat) to type float64

After:
expr.y:70[expr.go:492]: cannot convert exprDollar[1].num (type *big.Rat) to type float64

Change-Id: I74e494069df588e62299d1fccb282f3658d8f8f4
Reviewed-on: https://go-review.googlesource.com/4630Reviewed-by: Rob Pike <r@golang.org>

The current XML printer does not understand the xmlns
attribute. This change changes it so that it interprets the
xmlns attributes in the tokens being printed, and uses
appropriate prefixes.

Fixes #7535.

Change-Id: I20fae291d20602d37deb41ed42fab4c9a50ec85d
Reviewed-on: https://go-review.googlesource.com/2660Reviewed-by: Nigel Tao <nigeltao@golang.org>

MOVQ RARG0, 0(SP) smashes exactly what was saved by PUSHQ R15.
This code managed to work somehow with the current race runtime,
but corrupts caller arguments with new race runtime that I am testing.

Change-Id: I9ffe8b5eee86451db36e99dbf4d11f320192e576
Reviewed-on: https://go-review.googlesource.com/4810Reviewed-by: Keith Randall <khr@golang.org>

New race runtime is more scrupulous about env flags format.

Change-Id: I2828bc737a8be3feae5288ccf034c52883f224d8
Reviewed-on: https://go-review.googlesource.com/4811Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

drainworkbuf is now gcDrain, since it drains until there's
nothing left to drain.  drainobjects is now gcDrainN because it's
the bounded equivalent to gcDrain.

The new names use the Go camel case convention because we have to
start somewhere.  The "gc" prefix is because we don't have runtime
packages yet and just "drain" is too ambiguous.

Change-Id: I88dbdf32e8ce4ce6c3b7e1f234664be9b76cb8fd
Reviewed-on: https://go-review.googlesource.com/4785Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>

All calls to drainworkbuf now pass true for this argument, so remove
the argument and update the documentation to reflect the simplified
interface.

At a higher level, there are no longer any situations where we drain
"one wbuf" (though drainworkbuf didn't guarantee this anyway).  We
either drain everything, or we drain a specific number of objects.

Change-Id: Ib7ee0fde56577eff64232ee1e711ec57c4361335
Reviewed-on: https://go-review.googlesource.com/4784Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>

scanblock is only called during _GCscan and _GCmarktermination.
During _GCscan, scanblock didn't call drainworkbufs anyway.  During
_GCmarktermination, there's really no point in draining some (largely
arbitrary) amount of work during the scanblock, since the GC is about
to drain everything anyway, so simply eliminate this case.

Change-Id: I7f3c59ce9186a83037c6f9e9b143181acd04c597
Reviewed-on: https://go-review.googlesource.com/4783Reviewed-by: Russ Cox <rsc@golang.org>

We no longer ever call scanblock with b == 0.

Change-Id: I9b01da39595e0cc251668c24d58748d88f5f0792
Reviewed-on: https://go-review.googlesource.com/4782Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>

scanblock(0, 0, nil, nil) was just a confusing way of saying

  wbuf = getpartialorempty()
  drainworkbuf(wbuf, true)

Make drainworkbuf accept a nil workbuf and perform the
getpartialorempty itself and replace all uses of scanblock(0, 0, nil,
nil) with direct calls to drainworkbuf(nil, true).

Change-Id: I7002a2f8f3eaf6aa85bbf17ccc81d7288acfef1c
Reviewed-on: https://go-review.googlesource.com/4781Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>

Previously, scanblock called checknocurrentwbuf() after
drainworkbuf().  Move this call into drainworkbuf so that every return
path from drainworkbuf calls checknocurrentwbuf().  This is equivalent
to the previous code because scanblock was the only caller of
drainworkbuf.

Change-Id: I96ef2168c8aa169bfc4d368f296342fa0fbeafb4
Reviewed-on: https://go-review.googlesource.com/4780Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>

Currently we always create context objects for closures that capture variables.
However, it is completely unnecessary for direct calls of closures
(whether it is func()(), defer func()() or go func()()).
This change transforms any OCALLFUNC(OCLOSURE) to normal function call.
Closed variables become function arguments.
This transformation is especially beneficial for go func(),
because we do not need to allocate context object on heap.
But it makes direct closure calls a bit faster as well (see BenchmarkClosureCall).

On implementation level it required to introduce yet another compiler pass.
However, the pass iterates only over xtop, so it should not be an issue.
Transformation consists of two parts: closure transformation and call site
transformation. We can't run these parts on different sides of escape analysis,
because tree state is inconsistent. We can do both parts during typecheck,
we don't know how to capture variables and don't have call site.
We can't do both parts during walk of OCALLFUNC, because we can walk
OCLOSURE body earlier.
So now capturevars pass only decides how to capture variables
(this info is required for escape analysis). New transformclosure
pass, that runs just before order/walk, does all transformations
of a closure. And later walk of OCALLFUNC(OCLOSURE) transforms call site.

benchmark                            old ns/op     new ns/op     delta
BenchmarkClosureCall                 4.89          3.09          -36.81%
BenchmarkCreateGoroutinesCapture     1634          1294          -20.81%

benchmark                            old allocs     new allocs     delta
BenchmarkCreateGoroutinesCapture     6              2              -66.67%

benchmark                            old bytes     new bytes     delta
BenchmarkCreateGoroutinesCapture     176           48            -72.73%

Change-Id: Ic85e1706e18c3235cc45b3c0c031a9c1cdb7a40e
Reviewed-on: https://go-review.googlesource.com/4050Reviewed-by: Russ Cox <rsc@golang.org>

The only remaining uses of four spaces instead of a tab is
when the line is too long (e.g. type Package).

Fixes #9809

Change-Id: Ifffd3639aa9264e795686ef1879a7686f182d2e5
Reviewed-on: https://go-review.googlesource.com/4182Reviewed-by: Andrew Gerrand <adg@golang.org>

This was accidentially removed in:
https://go-review.googlesource.com/#/c/3508/8/src/cmd/gc/reflect.c

Change-Id: I06dd5bb0cb3e2811bd4ef605d7a5225cfa033fe0
Reviewed-on: https://go-review.googlesource.com/4731Reviewed-by: Keith Randall <khr@golang.org>

Change-Id: I7c41cc6a5ab9fb3b0cc3812cf7e9776884658778
Reviewed-on: https://go-review.googlesource.com/4671Reviewed-by: Ian Lance Taylor <iant@golang.org>

Using a zero register results in shorter, faster code.
5g already did this. Bring 6g, 8g, and 9g up to speed.
Reduces godoc binary size by 0.29% using 6g.

This CL includes cosmetic changes to 5g and 8g.
With those cosmetic changes included, componentgen is now
character-for-character equivalent across the four architectures.

Change-Id: I0e13dd48374bad830c725b117a1c86d4197d390c
Reviewed-on: https://go-review.googlesource.com/2606Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>

Fix a flipped nil check.
The flipped check prevented componentgen
from zeroing a non-cadable nl.
This fix reduces the number of non-SB LEAQs
in godoc from 35323 to 34920 (-1.1%).

Update #1914

Change-Id: I15ea303068835f606f883ddf4a2bb4cb2287e9ae
Reviewed-on: https://go-review.googlesource.com/2605Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>

Consider an interface value i of type I and concrete value c of type C.

Prior to this CL, i==c was evaluated as
	I(c) == i

Evaluating I(c) can allocate.

This CL changes the evaluation of i==c to
	x, ok := i.(C); ok && x == c

The new generated code is shorter and does not allocate directly.

If C is small, as it is in every instance in the stdlib,
the new code also uses less stack space
and makes one runtime call instead of two.

If C is very large, the original implementation is used.
The cutoff for "very large" is 1<<16,
following the stack vs heap cutoff used elsewhere.

This kind of comparison occurs in 38 places in the stdlib,
mostly in the net and os packages.

benchmark                     old ns/op     new ns/op     delta
BenchmarkEqEfaceConcrete      29.5          7.92          -73.15%
BenchmarkEqIfaceConcrete      32.1          7.90          -75.39%
BenchmarkNeEfaceConcrete      29.9          7.90          -73.58%
BenchmarkNeIfaceConcrete      35.9          7.90          -77.99%

Fixes #9370.

Change-Id: I7c4555950bcd6406ee5c613be1f2128da2c9a2b7
Reviewed-on: https://go-review.googlesource.com/2096Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>

When compiling the stdlib most of the calls
to sgen are for exactly 2 or 3 words:
85% for 6g and 70% for 8g.
Special case them for performance.
This optimization is not relevant to 5g and 9g.

6g

benchmark                old ns/op     new ns/op     delta
BenchmarkCopyFat16       3.25          0.82          -74.77%
BenchmarkCopyFat24       5.47          0.95          -82.63%

8g

benchmark               old ns/op     new ns/op     delta
BenchmarkCopyFat8       3.84          2.42          -36.98%
BenchmarkCopyFat12      4.94          2.15          -56.48%

Change-Id: I8bc60b453f12597dfd916df2d072a7d5fc33ab85
Reviewed-on: https://go-review.googlesource.com/2607Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>

When possible, generate nodl/nodr directly into DI/SI
rather than going through a temporary register.

CX has already been saved; use it during trailing bytes cleanup.

Change-Id: I4ec6209bcc5d3bfdc927c5c132009bd8d791ada3
Reviewed-on: https://go-review.googlesource.com/2608Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>

Change-Id: Ic270ffa7ec6f6dd4b0a951c64ad965447cce1417
Reviewed-on: https://go-review.googlesource.com/4571Reviewed-by: Alan Donovan <adonovan@google.com>

No code modifications.

This is in preparation for improving the wbuf abstraction.

Change-Id: I719543a345c34d079b7e39b251eccd5dd8a07826
Reviewed-on: https://go-review.googlesource.com/4710Reviewed-by: Rick Hudson <rlh@golang.org>

Plan 9's sysFree has an optimization where if the object being freed
is the last object allocated, it will roll back the brk to allow the
memory to be reused by sysAlloc.  However, it does not zero this
"returned" memory, so as a result, sysAlloc can return non-zeroed
memory after a sysFree.  This leads to corruption because the runtime
assumes sysAlloc returns zeroed memory.

Fix this by zeroing the memory returned by sysFree.

Fixes #9846.

Change-Id: Id328c58236eb7c464b31ac1da376a0b757a5dc6a
Reviewed-on: https://go-review.googlesource.com/4700Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: David du Colombier <0intro@gmail.com>

Change-Id: Id86994c8692e29f9d073b6322733ce9219887dc3
Reviewed-on: https://go-review.googlesource.com/4520
Run-TryBot: Andrew Gerrand <adg@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

Extend escape analysis to make(map[k]v).
If it does not escape, allocate temp buffer for hmap and one bucket on stack.

There are 75 cases of non-escaping maps in std lib.

benchmark                                    old allocs     new allocs     delta
BenchmarkConcurrentStmtQuery                 16161          15161          -6.19%
BenchmarkConcurrentTxQuery                   17658          16658          -5.66%
BenchmarkConcurrentTxStmtQuery               16157          15156          -6.20%
BenchmarkConcurrentRandom                    13637          13114          -3.84%
BenchmarkManyConcurrentQueries               22             20             -9.09%
BenchmarkDecodeComplex128Slice               250            188            -24.80%
BenchmarkDecodeFloat64Slice                  250            188            -24.80%
BenchmarkDecodeInt32Slice                    250            188            -24.80%
BenchmarkDecodeStringSlice                   2250           2188           -2.76%
BenchmarkNewEmptyMap                         1              0              -100.00%
BenchmarkNewSmallMap                         2              0              -100.00%

benchmark                old ns/op     new ns/op     delta
BenchmarkNewEmptyMap     124           55.7          -55.08%
BenchmarkNewSmallMap     317           148           -53.31%

benchmark                old allocs     new allocs     delta
BenchmarkNewEmptyMap     1              0              -100.00%
BenchmarkNewSmallMap     2              0              -100.00%

benchmark                old bytes     new bytes     delta
BenchmarkNewEmptyMap     48            0             -100.00%
BenchmarkNewSmallMap     192           0             -100.00%

Fixes #5449

Change-Id: I24fa66f949d2f138885d9e66a0d160240dc9e8fa
Reviewed-on: https://go-review.googlesource.com/3508Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>