Use AXXX instead of AGOK (neither is a valid instruction but AXXX is zero)
for the initial setting of Prog.as, and now there are no non-zero default
field settings.

Remove the arch-specific zprog/zprg in favor of a single global zprog.
Remove the arch-specific prg constructor in favor of emallocz(sizeof(Prog)).

Change-Id: Ia73078726768333d7cdba296f548170c1bea9498
Reviewed-on: https://go-review.googlesource.com/3575Reviewed-by: Aram Hăvărneanu <aram@mgk.ro>
Reviewed-by: Austin Clements <austin@google.com>

Originally, when this code was part of 6l/8l, every new
Prog was constructed starting with zprg, which set back=2,
and then this code walked over the list setting back=1 for
backward branches, back=0 otherwise. The initial back=2
setting was used to identify forward branches (the branched-to
instruction had back == 2 since it hadn't yet been set to 0 or 1).

When the code was extracted into liblink and linked directly
with 6a/6g/8a/8g, those programs created the Prog struct
and did not set back=2, breaking this backward branch detection.

No one noticed, because the next loop recomputes the information.
The only requirement for the next loop is that p->back == 0 or 1 for
each of the Progs in the list.

The initialization of the zprg with back=2 would cause problems
in this second loop, for the few liblink-internally-generated instructions
that are created by copying zprg, except that the first loop was
making sure that back == 0 or 1.

The first loop's manipulation of p->back can thus be deleted,
provided we also delete the zprg.back = 2 initializations.

This is awful and my fault. I apologize.

While we're here, remove the .scale = 1 from the zprg init too.
Anything that sets up a scaled index should set the scale itself.
(And mostly those come from outside liblink anyway.)

Tested by checking that all generated code is bit-for-bit
identical to before this CL.

Change-Id: I7f6e0b33ce9ccd5b7dc25e0f00429fedd0957c8c
Reviewed-on: https://go-review.googlesource.com/3574Reviewed-by: Austin Clements <austin@google.com>

A step toward making the zero Prog useful.

Change-Id: I427b98b1ce9bd8f093da825aa4bb83244fc01903
Reviewed-on: https://go-review.googlesource.com/3573Reviewed-by: Dave Cheney <dave@cheney.net>
Reviewed-by: Austin Clements <austin@google.com>

Before, amd64 and 386 stored the flags in p->from.scale
and arm and ppc64 stored the flags in p->reg.
Both caused special cases in printing and in handling of the
addresses.

To avoid possible conflicts with the real meaning of p->from
and to avoid storing a non-register value in a reg field,
use from3 to hold a TYPE_CONST value giving the flags.

There is still a special case for printing, because the flags
are specified without a $, and normally a TYPE_CONST prints
with a $. But that's much less special than what came before.

This allows us to remove the textflag and settextflag methods
from LinkArch. They are no longer architecture-specific.

Change-Id: I931da8e1ecd92e127cd9aa44ef5a73c42e730110
Reviewed-on: https://go-review.googlesource.com/3572Reviewed-by: Austin Clements <austin@google.com>

Change-Id: I3417a8c5ddd7f405939edc9fdef086e4741495a1
Reviewed-on: https://go-review.googlesource.com/3571Reviewed-by: Austin Clements <austin@google.com>

Because it was lumped in with the TEXT instruction,
the high 32 bits of the 64-bit constant holding the size
were always set to 0x80000000 (ArgsSizeUnknown).
This only worked because cmd/9l was reading the 64-bit
value into an int32.

While we're here, fix 5a.
It wasn't as much of a problem there because
the two values were being stored in two different fields.
But it was still wrong.

Change-Id: I69a2214c7be939530d499e29cfdc3b26720ac05a
Reviewed-on: https://go-review.googlesource.com/3570Reviewed-by: Austin Clements <austin@google.com>

Kindly detected by race builders by failing TestRaceRange.
ORANGE typecheck does not increment decldepth around body.

Change-Id: I0df5f310cb3370a904c94d9647a9cf0f15729075
Reviewed-on: https://go-review.googlesource.com/3507Reviewed-by: Russ Cox <rsc@golang.org>

Type switch variables was not typechecked.
Previously it lead only to a minor consequence:

switch unsafe.Sizeof = x.(type) {

generated an inconsistent error message.
But capturing by value functionality now requries typechecking of all ONAMEs.

Fixes #9731

Change-Id: If037883cba53d85028fb97b1328696091b3b7ddd
Reviewed-on: https://go-review.googlesource.com/3600Reviewed-by: Russ Cox <rsc@golang.org>

The overflow happens only with -gcflags="-N -l"
and can be reproduced with:

$ go test -gcflags="-N -l" -a -run=none net

runtime.cgocall: nosplit stack overflow
	504	assumed on entry to runtime.cgocall
	480	after runtime.cgocall uses 24
	472	on entry to runtime.cgocall_errno
	408	after runtime.cgocall_errno uses 64
	400	on entry to runtime.exitsyscall
	288	after runtime.exitsyscall uses 112
	280	on entry to runtime.exitsyscallfast
	152	after runtime.exitsyscallfast uses 128
	144	on entry to runtime.writebarrierptr
	88	after runtime.writebarrierptr uses 56
	80	on entry to runtime.writebarrierptr_nostore1
	24	after runtime.writebarrierptr_nostore1 uses 56
	16	on entry to runtime.acquirem
	-24	after runtime.acquirem uses 40

Move closure creation into separate function so that
frames of writebarrierptr_shadow and writebarrierptr_nostore1
are overlapped.

Fixes #9721

Change-Id: I40851f0786763ee964af34814edbc3e3d73cf4e7
Reviewed-on: https://go-review.googlesource.com/3418Reviewed-by: Russ Cox <rsc@golang.org>

Currently race detector produces the following reports on pprof tests:

WARNING: DATA RACE
Read by goroutine 4:
  runtime/pprof_test.TestTraceStartStop()
      src/runtime/pprof/trace_test.go:38 +0x1da
  testing.tRunner()
      src/testing/testing.go:448 +0x13a

Previous write by goroutine 5:
  bytes.(*Buffer).grow()
      src/bytes/buffer.go:102 +0x190
  bytes.(*Buffer).Write()
      src/bytes/buffer.go:127 +0x75
  runtime/pprof.func·002()
      src/runtime/pprof/pprof.go:633 +0xae

Trace writer goroutine synchronizes with StopTrace
using trace.shutdownSema runtime semaphore.
But race detector does not see that synchronization
and so produces false reports.
Teach race detector about the synchronization.

Change-Id: I1219817325d4e16b423f29a0cbee94c929793881
Reviewed-on: https://go-review.googlesource.com/3746Reviewed-by: Russ Cox <rsc@golang.org>

The test for the framepointer experiment flag is cheaper and more
branch-predictable than the other parts of this conditional, so move
it first.  This is also more readable.

(Originally, the flag check required parsing the experiments string,
which is why it was done last.  Now that flag is cached.)

Change-Id: I84e00fa7e939e9064f0fa0a4a6fe00576dd61457
Reviewed-on: https://go-review.googlesource.com/3782Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Previously, we checked for a saved frame pointer by looking for a
2*ptrSize gap between the argument pointer and the locals pointer.
The intent of this check was to look for a two stack slot gap (caller
IP and saved frame pointer), but stack slots are regSize, not ptrSize.

Correct this by checking instead for a 2*regSize gap.

On most platforms, this made no difference because ptrSize==regSize.
However, on amd64p32 (nacl), the saved frame pointer check incorrectly
fired when there was no saved frame pointer because the one stack slot
for the caller IP left an 8 byte gap, which is 2*ptrSize (but not
2*regSize) on amd64p32.

Fixes #9760.

Change-Id: I6eedcf681fe5bf2bf924dde8a8f2d9860a4d758e
Reviewed-on: https://go-review.googlesource.com/3781Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: Ife7d30f4191e6a8aaf3a442340d277989f7a062d
Reviewed-on: https://go-review.googlesource.com/3780Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

This change adds support for case insensitivity of DNS labels to
built-in DNS stub resolver as described in RFC 4343.

Fixes #9215.

Change-Id: Ia752fe71866a3bfa3ea08371985b799d419ddea3
Reviewed-on: https://go-review.googlesource.com/3685Reviewed-by: Ian Lance Taylor <iant@golang.org>

We already checked for the prefix with strings.HasPrefix

Change-Id: I33852fd19ffa92aa33b75b94b4bb505f4043a54a
Reviewed-on: https://go-review.googlesource.com/3691Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fourth time's the charm.

Actually this doesn't fix the build, there is a
crash after go_bootstrap is compiled which looks
like it is related to auxv parsing.

Change-Id: Id00e2dfbe7bae42856f996065d3fb90b820e29a8
Reviewed-on: https://go-review.googlesource.com/3610Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Add memprofrate as a value recognized in GODEBUG.  The
value provided is used as the new setting for
runtime.MemProfileRate, allowing the user to
adjust memory profiling.

Change-Id: If129a247683263b11e2dd42473cf9b31280543d5
Reviewed-on: https://go-review.googlesource.com/3450Reviewed-by: Ian Lance Taylor <iant@golang.org>

This adds a "framepointer" GOEXPERIMENT that that makes the amd64
toolchain maintain base pointer chains in the same way that gcc
-fno-omit-frame-pointer does.  Go doesn't use these saved base
pointers, but this does enable external tools like Linux perf and
VTune to unwind Go stacks when collecting system-wide profiles.

This requires support in the compilers to not clobber BP, support in
liblink for generating the BP-saving function prologue and unwinding
epilogue, and support in the runtime to save BPs across preemption, to
skip saved BPs during stack unwinding and, and to adjust saved BPs
during stack moving.

As with other GOEXPERIMENTs, everything from the toolchain to the
runtime must be compiled with this experiment enabled.  To do this,
run make.bash (or all.bash) with GOEXPERIMENT=framepointer.

Change-Id: I4024853beefb9539949e5ca381adfdd9cfada544
Reviewed-on: https://go-review.googlesource.com/2992Reviewed-by: Russ Cox <rsc@golang.org>

Any place that clobbers BP in the runtime can potentially interfere
with frame pointer unwinding with GOEXPERIMENT=framepointer.  This
change eliminates uses of BP in the runtime to address this problem.
We have spare registers everywhere this occurs, so there's no downside
to eliminating BP.  Where possible, this uses the same new register as
the amd64p32 runtime, which doesn't use BP due to restrictions placed
on it by NaCL.

One nice side effect of this is that it will let perf/VTune unwind the
call stack even through a call to systemstack, which will let us get
really good call graphs from the garbage collector.

Change-Id: I0ffa14cb4dd2b613a7049b8ec59df37c52286212
Reviewed-on: https://go-review.googlesource.com/3390Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

m.gcing has become overloaded to mean "don't preempt this g" in
general.  Once the garbage collector is preemptible, the one thing it
*won't* mean is that we're in the garbage collector.

So, rename gcing to "preemptoff" and make it a string giving a reason
that preemption is disabled.  gcing was never set to anything but 0 or
1, so we don't have to worry about there being a stack of reasons.

Change-Id: I4337c29e8e942e7aa4f106fc29597e1b5de4ef46
Reviewed-on: https://go-review.googlesource.com/3660Reviewed-by: Russ Cox <rsc@golang.org>

Commit 656be317 replaced onM with systemstack, but missed updating a
few comments that still referred to onM.  Update these.

Change-Id: I0efb017e9a66ea0adebb6e1da6e518ee11263f69
Reviewed-on: https://go-review.googlesource.com/3664Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

9g generates needlessly complex code for small copies.  There are a
few other things that need to be improved about the copy code, so for
now just note the problem.

Change-Id: I0f1de4b2f9197a2635e27cc4b91ecf7a6c11f457
Reviewed-on: https://go-review.googlesource.com/3665Reviewed-by: Russ Cox <rsc@golang.org>

Change-Id: I278ce47b38ec5732d981aec06b71f9ee5747c3bb
Reviewed-on: https://go-review.googlesource.com/3730Reviewed-by: Alan Donovan <adonovan@google.com>

In stripCommonPrefix, the prefix was correctly calculated in all cases,
except one. That unhandled case is when there are more than 2 lines,
but all lines are blank (other than the first and last lines,
which contain /* and */ respectively).
This change detects that case and correctly sets the prefix calculated
from the last line. This is consistent with the (correct) behavior
that happens when there's at least one non-blank line.
That fixes issue #9751 that occurs for problematic input,
where cmd/gofmt and go/source would insert extra indentation on
every format operation. It also allows go/printer itself to print
such parsed files in an expected way.

Fixes #9751.

Change-Id: Id3dfb945beb59ffad3705085a3c285fca30a5f87
Reviewed-on: https://go-review.googlesource.com/3684Reviewed-by: Robert Griesemer <gri@golang.org>

Since CL 3676, the TestMkdirAllAtSlash test
depends on syscall.EROFS, which isn't defined
on Plan 9.

This change works around this issue by
defining a system dependent isReadonlyError
function.

Change-Id: If972fd2fe4828ee3bcb8537ea7f4ba29f7a87619
Reviewed-on: https://go-review.googlesource.com/3696Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Fixes #9738.

Change-Id: Iab75de2d78335d4e31c3dce6a0e1826d8cddf5f3
Reviewed-on: https://go-review.googlesource.com/3690Reviewed-by: Dmitry Vyukov <dvyukov@google.com>

Change-Id: Iea4221186325783db2029b07af1409015ddeda99
Reviewed-on: https://go-review.googlesource.com/3695Reviewed-by: Dave Cheney <dave@cheney.net>

This is a followup to CL 3676.

Rather than silently returning from the test, a pass,
use the Skip facility to mark the test as skipped.

Change-Id: I90d237e770150bf8d69f14fb09874e70894a7f86
Reviewed-on: https://go-review.googlesource.com/3682Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

On some systems (e.g. ChromeOS), / is mounted read-only.
This results in error code syscall.EROFS, which I guess
is just as valid as syscall.EACCES for this test.

Change-Id: I9188d5437a1b5ac1daa9c68b95b8dcb447666ca3
Reviewed-on: https://go-review.googlesource.com/3676Reviewed-by: Ian Lance Taylor <iant@golang.org>

No other functional changes.

Change-Id: I7e0bb7452c6a265535297ec7ce6a629f1aff695c
Reviewed-on: https://go-review.googlesource.com/3674Reviewed-by: Alan Donovan <adonovan@google.com>

No other functional changes.

Change-Id: I8be1fc488caa4f3d4c00afcb8c00475bfcd10709
Reviewed-on: https://go-review.googlesource.com/3673Reviewed-by: Alan Donovan <adonovan@google.com>

No other functional changes.

Change-Id: If0d9e6208d53478e70d991b6926ea196b2cccf2e
Reviewed-on: https://go-review.googlesource.com/3672Reviewed-by: Alan Donovan <adonovan@google.com>

No functional changes.

Change-Id: Ibbb705b167603d30467f3ebb83a3bb39845306a5
Reviewed-on: https://go-review.googlesource.com/3671Reviewed-by: Alan Donovan <adonovan@google.com>

Change-Id: I1eaebf956a69e0958201cc5e0a9beefa062c71e1
Reviewed-on: https://go-review.googlesource.com/3454Reviewed-by: Alan Donovan <adonovan@google.com>

Change-Id: I257211f10b334eb4828be96cd434d588bfb1a378
Reviewed-on: https://go-review.googlesource.com/3605Reviewed-by: Rob Pike <r@golang.org>

Fixes #9629

Change-Id: I66091003b97742ca6d857fe51d609833ab727216
Reviewed-on: https://go-review.googlesource.com/3023Reviewed-by: Rob Pike <r@golang.org>

Fixes #9656

Change-Id: I1158636683492ef12eeafb12e257d205026adc3f
Reviewed-on: https://go-review.googlesource.com/3175Reviewed-by: Minux Ma <minux@golang.org>

These are no longer used by anything.

Change-Id: I50c971418b07cafc983242833a196ba2028a2723
Reviewed-on: https://go-review.googlesource.com/3603Reviewed-by: Rob Pike <r@golang.org>

Another attempt to fix the arm build by moving the include of signal.h
to cmd/lex.c, unless we are building on plan9.

Obviously if we had a plan9/arm builder this would probably not work, but
this is only a temporary measure until the c2go transition is complete.

Change-Id: I7f8ae27349b2e7a09c55db03e02a01939159a268
Reviewed-on: https://go-review.googlesource.com/3566Reviewed-by: Russ Cox <rsc@golang.org>

The following line in sysFree:
n += (n + memRound) &^ memRound
doubles value of n (n += n).
Which is wrong and can lead to memory corruption.

Fixes #9712

Change-Id: I3c141b71da11e38837c09408cf4f1d22e8f7f36e
Reviewed-on: https://go-review.googlesource.com/3602Reviewed-by: David du Colombier <0intro@gmail.com>