Updates #23574

Change-Id: I1b87390679e0817a2f6e4e5938994ea32df87bd7
Reviewed-on: https://go-review.googlesource.com/107596Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

CL 106735 changed to the new softfloat support on GOARM=5.

ARM assembly code that uses FP instructions not guarded on GOARM,
if any, will break. The easiest way to fix is probably to use Go
implementation on GOARM=5, like

	MOVB	runtime·goarm(SB), R11
	CMP	$5, R11
	BEQ	arm5
	... FP instructions ...
	RET
arm5:
	CALL or JMP to Go implementation

Change-Id: I52fc76fac9c854ebe7c6c856c365fba35d3f560a
Reviewed-on: https://go-review.googlesource.com/107475
Run-TryBot: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Say "offset too large" instead of "invalid instruction" when
assembling for AMD64. GOARCH=386 already reports error correctly.

Fixed #24871

Change-Id: Iab029307b5c5edbb45f9df4b64c60ecb5f101349
Reviewed-on: https://go-review.googlesource.com/107116
Run-TryBot: Iskander Sharipov <iskander.sharipov@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

cmd/link produces ELF executables on all these geese, so enable
TestNoSectionOverlaps for them as well. Also add a skip message.

Change-Id: I374651dde3679271ef8c0c375c9cabd1adbca310
Reviewed-on: https://go-review.googlesource.com/107535
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

This reverts commit 49e3e436.

Reason for revert: breaks iOS builders and Daniel can't fix for a week.

Change-Id: Ib6ff08de9540d46345dc31e1f820c8555e3de3ca
Reviewed-on: https://go-review.googlesource.com/107218Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>

In the Scan functions documentation, clarify that for float/complex
literals in scientific notation both decimal (e) and binary (p)
exponents are accepted.

Fixes #24453

Change-Id: Ic6dcdb0c36e088ffb65177038aff7a57ab56b805
Reviewed-on: https://go-review.googlesource.com/107416Reviewed-by: Rob Pike <r@golang.org>

The use of binary was incorrect as executable files can also be scripts.

The docs for Error are also reworded. The old docs implied that Error was
returned when attempting to start an executable, which is not correct: it
was returned by LookPath when the file was not found or did not have the
attributes of an executable.

Change-Id: I757a44b16612936df4498b43c45c12e4c14956d2
Reviewed-on: https://go-review.googlesource.com/90315Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

When a test calls t.Fatal()/t.Fatalf(), only deferred code will execute.
Increment the failure count as part of a deferred call.

Fixes #24412

Change-Id: Ibb154015fcd3d0fb7739718fdda8c9ad22f9e896
Reviewed-on: https://go-review.googlesource.com/101035
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

One might try to implement the Mod or Remainder function with the expression
x - TRUNC(x/y + 0.5)*y, but in fact this method is wrong, because the rounding
of (x/y + 0.5) to initialize the argument of TRUNC may lose too much precision.
However, the current test cases can not detect this error. This CL adds two
test cases to prevent people from continuing to do such attempts.

Change-Id: I6690f5cffb21bf8ae06a314b7a45cafff8bcee13
Reviewed-on: https://go-review.googlesource.com/84275Reviewed-by: Robert Griesemer <gri@golang.org>

Made constant names more idiomatic,
moved some constants to function seedrand,
and found better name for _M.

Change-Id: I192172f398378bef486a5bbceb6ba86af48ebcc9
Reviewed-on: https://go-review.googlesource.com/107135Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>

The previous CL, 107197, overclarified the need for short subject
lines. Tweak the wording to be a guideline (keep it short) rather
than a limit (76 characters), which is more the Go way.

Also be strict about avoiding markup language.

Change-Id: I0da1132db8d86052647d96f1caac60289f2209ce
Reviewed-on: https://go-review.googlesource.com/107378Reviewed-by: Mohit Bajoria <mohitbajo36@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Verified that on on Linux, with:

CGO_ENABLED=1 GOOS=solaris go install --tags=osusergo

... it builds now.

Updates #24841
Updates #24845

Change-Id: I49f40532bc2a13a9d282771592fc8d7f116b1902
Reviewed-on: https://go-review.googlesource.com/107304Reviewed-by: Mikio Hara <mikioh.mikioh@gmail.com>

Existing tests don't check overflow and underflow case for subtraction
monotonic time.

Updates #17858

Change-Id: I95311440134c92eadd7d5e409a0fc7c689e9bf41
Reviewed-on: https://go-review.googlesource.com/107056
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Updates #19435.

Change-Id: Ife4a31972b05094a86c60a48fcacdfe52d133ee4
Reviewed-on: https://go-review.googlesource.com/107395
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

If both inputs are constant offsets from the same pointer then we
can evaluate NeqPtr and EqPtr at compile time. Triggers a few times
during all.bash. Removes a conditional branch in the following
code:

copy(x[1:], x[:])

This branch was recently added as an optimization in CL 94596. We
now skip the memmove if the pointers are equal. However, in the
above code we know at compile time that they are never equal.

Also, when the offset is variable, check if the offset is zero
rather than if the pointers are equal. For example:

copy(x[a:], x[:])

This would now skip the copy if a == 0, rather than if x + a == x.

Finally I've also added a rule to make IsNonNil true for pointers
to values on the stack. The nil check elimination pass will catch
these anyway, but eliminating them here might eliminate branches
earlier.

Change-Id: If72f436fef0a96ad0f4e296d3a1f8b6c3e712085
Reviewed-on: https://go-review.googlesource.com/106635
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Fixes #24864

Change-Id: Iaffd23b368aff663bfc09a4e6277c01e7b5ea48d
GitHub-Last-Rev: 98e39b7bff6e646d48c0bf961aee0075a9034ab2
GitHub-Pull-Request: golang/go#24865
Reviewed-on: https://go-review.googlesource.com/106986Reviewed-by: Giovanni Bajo <rasky@develer.com>
Reviewed-by: Rob Pike <r@golang.org>

Would've caught two regressions so far, and found two more.

Updates #24841
Updates #24845 (package net remains)

Change-Id: I57ad06eb54e04b8c99b5d2e7f24c77ad865224e8
Reviewed-on: https://go-review.googlesource.com/107300Reviewed-by: Ian Lance Taylor <iant@golang.org>

Fixes #24841
Updates #24845

Change-Id: Ia7e2deefe64c12ee8a76ce6ed9f9e003e912b161
Reviewed-on: https://go-review.googlesource.com/107299Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Use the vendored ValidTrailerHeader function from x/net/http/httpguts to
check Trailer headers according to RFC 7230. The previous implementation
only omitted illegal Trailer headers defined in RFC 2616.

This CL adds x/net/http/httpguts from CL 104042 (git rev a35a21de97)

Fixes #23908

Change-Id: Ib2329a384040494093c18e209db9b62aaf86e921
Reviewed-on: https://go-review.googlesource.com/104075Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

As suggested by Ian on the issue, just use past releases to avoid any
confusion regarding current and future releases.

Fixes #23891

Change-Id: Ie513cd3e15aa04822898be57f71976e6fe6bd816
Reviewed-on: https://go-review.googlesource.com/107078Reviewed-by: Andrew Bonventre <andybons@golang.org>

Change-Id: I0e6b308333b84409bb0bb034c17fef9b63ad44c4
Reviewed-on: https://go-review.googlesource.com/107377Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Move the Issue16214 test in the fixedbugs_test.go file, and delete the
now empty asm_test.go file.

Change-Id: I2a0c72bd36f0359b7baf75b5d1ba647cc84feb46
Reviewed-on: https://go-review.googlesource.com/106836
Run-TryBot: Alberto Donizetti <alb.donizetti@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Giovanni Bajo <rasky@develer.com>

Fixes #24852

Change-Id: I71d0d7f75108bf4ad606733a45bb71baa66a4e91
Reviewed-on: https://go-review.googlesource.com/107197Reviewed-by: Alberto Donizetti <alb.donizetti@gmail.com>
Reviewed-by: Giovanni Bajo <rasky@develer.com>

Fixes comment style.
Added names to return parameters to clarify what they are.

Change-Id: Ib6f7f58b36981e08b63de1a4cd582ce99cfb4519
Reviewed-on: https://go-review.googlesource.com/107235Reviewed-by: Iskander Sharipov <iskander.sharipov@intel.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Iskander Sharipov <iskander.sharipov@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Change-Id: I2e58e20e26674175b3e35b6c8a05998a93db4646
Reviewed-on: https://go-review.googlesource.com/107215Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The SUBL instruction can take a memory operand, and this CL
implements this optimization.

The go1 benchmark shows a little improvement.

name                     old time/op    new time/op    delta
BinaryTree17-4              3.27s ± 2%     3.29s ± 3%    ~     (p=0.322 n=37+40)
Fannkuch11-4                3.49s ± 0%     3.53s ± 1%  +1.21%  (p=0.000 n=31+40)
FmtFprintfEmpty-4          46.2ns ± 3%    46.3ns ± 2%    ~     (p=0.351 n=40+28)
FmtFprintfString-4         82.0ns ± 3%    81.5ns ± 2%  -0.69%  (p=0.002 n=40+30)
FmtFprintfInt-4            94.6ns ± 3%    94.6ns ± 6%    ~     (p=0.913 n=39+37)
FmtFprintfIntInt-4          147ns ± 3%     150ns ± 2%  +1.72%  (p=0.000 n=40+25)
FmtFprintfPrefixedInt-4     186ns ± 3%     186ns ± 0%  -0.33%  (p=0.006 n=40+25)
FmtFprintfFloat-4           388ns ± 4%     388ns ± 4%    ~     (p=0.162 n=40+40)
FmtManyArgs-4               612ns ± 3%     616ns ± 4%    ~     (p=0.223 n=40+40)
GobDecode-4                7.35ms ± 5%    7.42ms ± 5%    ~     (p=0.095 n=40+40)
GobEncode-4                7.21ms ± 8%    7.23ms ± 4%    ~     (p=0.294 n=40+40)
Gzip-4                      360ms ± 4%     359ms ± 4%    ~     (p=0.097 n=40+40)
Gunzip-4                   46.1ms ± 3%    45.6ms ± 3%  -1.20%  (p=0.000 n=40+40)
HTTPClientServer-4         64.0µs ± 2%    64.1µs ± 2%    ~     (p=0.648 n=39+40)
JSONEncode-4               21.9ms ± 4%    22.1ms ± 5%    ~     (p=0.086 n=40+40)
JSONDecode-4               67.9ms ± 4%    66.7ms ± 4%  -1.63%  (p=0.000 n=40+40)
Mandelbrot200-4            5.19ms ± 3%    5.17ms ± 3%    ~     (p=0.881 n=40+40)
GoParse-4                  3.34ms ± 3%    3.28ms ± 2%  -1.78%  (p=0.000 n=40+40)
RegexpMatchEasy0_32-4       101ns ± 5%      99ns ± 3%  -2.40%  (p=0.000 n=40+40)
RegexpMatchEasy0_1K-4       851ns ± 1%     848ns ± 3%  -0.36%  (p=0.004 n=33+40)
RegexpMatchEasy1_32-4       109ns ± 5%     105ns ± 3%  -3.53%  (p=0.000 n=39+40)
RegexpMatchEasy1_1K-4      1.03µs ± 4%    1.03µs ± 3%    ~     (p=0.638 n=40+38)
RegexpMatchMedium_32-4      131ns ± 5%     127ns ± 4%  -3.36%  (p=0.000 n=38+40)
RegexpMatchMedium_1K-4     43.4µs ± 4%    43.2µs ± 3%  -0.46%  (p=0.008 n=40+40)
RegexpMatchHard_32-4       2.21µs ± 4%    2.23µs ± 1%  +0.77%  (p=0.014 n=40+28)
RegexpMatchHard_1K-4       67.6µs ± 4%    67.7µs ± 3%  +0.11%  (p=0.016 n=40+40)
Revcomp-4                   1.86s ± 3%     1.77s ± 2%  -4.81%  (p=0.000 n=40+40)
Template-4                 71.7ms ± 3%    71.6ms ± 4%    ~     (p=0.200 n=40+40)
TimeParse-4                 436ns ± 4%     433ns ± 3%    ~     (p=0.358 n=40+40)
TimeFormat-4                413ns ± 4%     412ns ± 3%    ~     (p=0.415 n=40+40)
[Geo mean]                 63.9µs         63.6µs       -0.49%

name                     old speed      new speed      delta
GobDecode-4               105MB/s ± 5%   104MB/s ± 5%    ~     (p=0.096 n=40+40)
GobEncode-4               106MB/s ± 7%   106MB/s ± 3%    ~     (p=0.385 n=39+40)
Gzip-4                   54.0MB/s ± 4%  54.0MB/s ± 4%    ~     (p=0.100 n=40+40)
Gunzip-4                  421MB/s ± 3%   426MB/s ± 3%  +1.21%  (p=0.000 n=40+40)
JSONEncode-4             88.5MB/s ± 5%  88.0MB/s ± 5%    ~     (p=0.083 n=40+40)
JSONDecode-4             28.6MB/s ± 4%  29.1MB/s ± 4%  +1.65%  (p=0.000 n=40+40)
GoParse-4                17.3MB/s ± 3%  17.7MB/s ± 2%  +1.82%  (p=0.000 n=40+40)
RegexpMatchEasy0_32-4     316MB/s ± 5%   323MB/s ± 4%  +2.44%  (p=0.000 n=40+40)
RegexpMatchEasy0_1K-4    1.20GB/s ± 1%  1.21GB/s ± 3%  +0.40%  (p=0.004 n=33+40)
RegexpMatchEasy1_32-4     291MB/s ± 7%   302MB/s ± 4%  +3.82%  (p=0.000 n=40+40)
RegexpMatchEasy1_1K-4     993MB/s ± 4%   990MB/s ± 3%    ~     (p=0.623 n=40+38)
RegexpMatchMedium_32-4   7.61MB/s ± 5%  7.87MB/s ± 4%  +3.36%  (p=0.000 n=38+40)
RegexpMatchMedium_1K-4   23.6MB/s ± 4%  23.7MB/s ± 4%  +0.46%  (p=0.007 n=40+40)
RegexpMatchHard_32-4     14.5MB/s ± 4%  14.3MB/s ± 1%  -0.79%  (p=0.017 n=40+28)
RegexpMatchHard_1K-4     15.1MB/s ± 4%  15.1MB/s ± 3%  -0.11%  (p=0.015 n=40+40)
Revcomp-4                 137MB/s ± 3%   144MB/s ± 3%  +5.06%  (p=0.000 n=40+40)
Template-4               27.1MB/s ± 3%  27.1MB/s ± 4%    ~     (p=0.211 n=40+40)
[Geo mean]               78.9MB/s       79.7MB/s       +1.01%

Change-Id: I638fa4fef85833e8605919d693f9570cc3cf7334
Reviewed-on: https://go-review.googlesource.com/107275
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Focus on "isfoo" funcs that take a *Node, and conver them to isFoo
methods instead. This makes for more idiomatic Go code, and also more
readable func names.

Found candidates with grep, and applied most changes with sed. The funcs
chosen were isgoconst, isnil, and isblank. All had the same signature,
func(*Node) bool.

While at it, camelCase the isliteral and iszero function names. Don't
move these to methods, as they are only used in the backend part of gc,
which might one day be split into a separate package.

Passes toolstash -cmp on std cmd.

Change-Id: I4df081b12d36c46c253167c8841c5a841f1c5a16
Reviewed-on: https://go-review.googlesource.com/105555
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

This changes rawResponse to install a logger before
Serve()ing and makes the log output available to
tests.

Updates #24831
Updates CL 89275

Change-Id: I0fb636a35b05959ca9978d5d8552f38b7cf8e8b5
Reviewed-on: https://go-review.googlesource.com/106756Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

A switch statement without a tag requires case values to be bools, but
the parser does not enforce that, so AST-walking code needs to take
care.

Change-Id: I7d9abbb0324314e02a37813c2d2f6adb0d6af5e7
Reviewed-on: https://go-review.googlesource.com/107375Reviewed-by: Rob Pike <r@golang.org>

name                  old time/op  new time/op  delta
CheckCanceled/Err-4   53.5ns ± 2%  20.8ns ± 0%  -61.05%  (p=0.008 n=5+5)
CheckCanceled/Done-4  44.4ns ± 1%  44.5ns ± 0%     ~     (p=0.889 n=5+5)

Change-Id: I2c68700a2b33f8feb3d307ce7c966590a3e960af
Reviewed-on: https://go-review.googlesource.com/107137Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: Ia64535492515f725fe3c4b59ea300363a0c4ce10
Reviewed-on: https://go-review.googlesource.com/107136Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

While writing CL 107315, I went back and forth for the syntax used for
constraints of build environments in which the architecture did not
support varitants ("plan9/amd64" vs "plan9/amd64/"). I eventually
settled for the latter because the code required less heuristics
(think parsing "plan9/386" vs "386/sse2") but there were a few
leftovers in code and comments.

Change-Id: I9d9a008f3814f9a1642609650eb571e7f1a675cf
Reviewed-on: https://go-review.googlesource.com/107338
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Not used anymore, all tests have been migrated to
the top-level testsuite.

Change-Id: I536e6c14f62153c01e4966ad41e1501b38494c7f
Reviewed-on: https://go-review.googlesource.com/107336
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

After CL 104636 cpu.X86.HasAVX is set early enough that it can be used
in runtime·memclrNoHeapPointers. Add an offset to use in assembly and
replace the only occurence of support_avx2.

Change-Id: Icada62efeb3e24d71251d55623a8a8602364c9a8
Reviewed-on: https://go-review.googlesource.com/106595
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ilya Tocar <ilya.tocar@intel.com>

This CL makes the codegen testsuite automatically test all
architecture variants for architecture specified in tests. For
instance, if a test file specifies a "arm" test, it will be
automatically run on all GOARM variants (5,6,7), to increase
the coverage.

The CL also introduces a syntax to specify only a specific
variant (eg: "arm/7") in case the test makes sense only there.
The same syntax also allows to specify the operating system
in case it matters (eg: "plan9/386/sse2").

Fixes #24658

Change-Id: I2eba8b918f51bb6a77a8431a309f8b71af07ea22
Reviewed-on: https://go-review.googlesource.com/107315
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

And remove it from asmtest. Next CL will remove the whole
asmtest infrastructure.

Change-Id: I5851bf7c617456d62a3c6cffacf70252df7b056b
Reviewed-on: https://go-review.googlesource.com/107335
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

CL 106463 introduced what seems to trim the "go:" prefix in pramas
comments twice, so "//go:go:foo" would be handled, too.
So either the strings.TrimPrefix or the [3:]-slicing is not needed.

I opted to remove the [3:]-slicing.

Change-Id: I1325bbc08a9be9ae100c5a7775b0a23f9ed0a419
Reviewed-on: https://go-review.googlesource.com/107256Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes gosimple warning "if err != nil { return err };
return nil' can be simplified to 'return err"

Change-Id: Ibbc717fb066ff41ab35c481b6d44980ac809ae09
Reviewed-on: https://go-review.googlesource.com/107018
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

It was skipping dirs starting with ".", but it was missing the "_"
prefix and the "testdata" name. From "go help packages":

	Directory and file names that begin with "." or "_" are ignored
	by the go tool, as are directories named "testdata".

Before the change:

	$ go doc z # using src/cmd/go/testdata/testvendor/src/q/z
	package z // import "."

After the fix, it falls back to the current directory, as expected when
a single argument isn't found as a package in $GOPATH.

TestMain needs a small adjustment to keep the tests working, as now
their use of cmd/doc/testdata would normally not work.

Fixes #24462.

Change-Id: I1f5d6d1eba0fb59aff55db33b3b1147e300284ef
Reviewed-on: https://go-review.googlesource.com/106935
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

Change-Id: I67b8b501290f6e321030967a19e3cb3bb9d678c6
Reviewed-on: https://go-review.googlesource.com/107016Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>