Daniel Martí [Sat, 23 Sep 2017 20:44:18 +0000 (21:44 +0100)]
cmd/compile: add runtime GC funcs to inlining test
This is based on a list that Austin Clements provided in mid-2016. It is
mostly untouched, except for the fact that the wbufptr funcs were
removed from the runtime thus removed from the lits here too.
Add a section for these GC funcs, since there are quite a lot of them
and the runtime has tons of funcs that we want to inline. As before,
sort this section too.
Also place some of these funcs out of the GC section, as they are not
directly related to the GC.
By refactoring job.arg from int with 0/1 as the only valid values into bool
and simplifying (*bitState).push, we reduce the number of nodes below the inlining threshold.
This improves backtracking regexp performance by 5-10% and go1 geomean by 1.7%
Full performance data below:
Keith Randall [Mon, 25 Sep 2017 17:28:20 +0000 (10:28 -0700)]
cmd/compile: improve static map initialization
When static maps are large, we try to initialize them
by iterating over an array of key/value pairs.
Currently this optimization only works if the keys and values
are of primitive type. This CL improves this optimization
by allowing any static composite literals as well.
Fixes #22010
Change-Id: Ie493e02ab8b8a228a3472b5c6025a33f7b92daf3
Reviewed-on: https://go-review.googlesource.com/66050
Run-TryBot: Keith Randall <khr@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
path/filepath: ensure Walk report unreadable directories once
Before this change, if Walk encounters an unreadable directory,
it will call walkFn with this directory twice. Argument err in
the first call is nil, and the second is the permission error.
This change removes the former call and makes Walk call walkFn
with permission error.
Fixes #21758
Change-Id: I21e57c67f3c5a8370fc80a43db3c8009fbce6439
Reviewed-on: https://go-review.googlesource.com/63994
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Gabriel Aszalos [Mon, 25 Sep 2017 11:01:36 +0000 (13:01 +0200)]
bytes: improve readability of IndexAny and LastIndexAny functions
This change removes the check of len(chars) > 0 inside the Index and
IndexAny functions which was redundant.
Change-Id: Ic4bf8b8a37d7f040d3ebd81b4fc45fcb386b639a
Reviewed-on: https://go-review.googlesource.com/65851
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
strings.IndexByte was introduced in go1.2 and it can be used
effectively wherever the second argument to strings.Index is
exactly one byte long.
This avoids generating unnecessary string symbols and saves
a few calls to strings.Index.
Change-Id: I1ab5edb7c4ee9058084cfa57cbcc267c2597e793
Reviewed-on: https://go-review.googlesource.com/65930
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Under certain circumstances involving shifts, go/types didn't verify
that untyped constant values were representable by the relevant type,
leading to the acceptance of incorrect programs (see the issue).
Fixing this code exposed another problem with int-to-string conversions
which suddenly failed because now the type-checker complained that a
(constant) integer argument wasn't representable as a string. Fixed that
as well.
Added many additional tests covering the various scenarious.
Found two cmd/compile bugs in the process (#21979, #21981) and filed
a go/types TODO (#21982).
Fixes #21727.
Change-Id: If443ee0230979cd7d45d2fc669e623648caa70da
Reviewed-on: https://go-review.googlesource.com/65370 Reviewed-by: Alan Donovan <adonovan@google.com>
Daniel Martí [Sun, 24 Sep 2017 16:55:19 +0000 (17:55 +0100)]
cmd/compile: merge bytes inline test with the rest
In golang.org/cl/42813, a test was added in the bytes package to check
if a Buffer method was being inlined, using 'go tool nm'.
Now that we have a compiler test that verifies that certain funcs are
inlineable, merge it there. Knowing whether the funcs are inlineable is
also more reliable than whether or not their symbol appears in the
binary, too. For example, under some circumstances, inlineable funcs
can't be inlined, such as if closures are used.
While at it, add a few more bytes.Buffer methods that are currently
inlined and should clearly stay that way.
Updates #21851.
Change-Id: I62066e32ef5542d37908bd64f90bda51276da4de
Reviewed-on: https://go-review.googlesource.com/65658
Run-TryBot: Daniel Martí <mvdan@mvdan.cc> Reviewed-by: Marvin Stenger <marvin.stenger94@gmail.com> Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Minaev Mike [Mon, 7 Aug 2017 08:22:21 +0000 (08:22 +0000)]
net/mail: skip trailing comment while parsing email
The existing implementation doesn't handle
comment constructions in email address.
So addresses that are consistent with RFC 5322
don't parse at all.
Fixes #21257
Change-Id: Iae3ba951dfb26b7cf0e1885a680bbceb9123d6d5
Reviewed-on: https://go-review.googlesource.com/53550
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
sort: update main example to use Slice along with Sort
This is to let sort.Slice get more prominence since
it's the most common use case.
Fixes #21989
Change-Id: I0b180cc20256f5f09065b722e191c508c872f4f7
Reviewed-on: https://go-review.googlesource.com/65710 Reviewed-by: Rob Pike <r@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Daniel Martí [Sun, 24 Sep 2017 10:16:52 +0000 (11:16 +0100)]
cmd/go: move GOOS/GOARCH and tags checks to Init
They were in Do, which is the method that actually starts the build.
However, we can already run these checks in Init, since we already have
all the information necessary to do the checks.
More importantly, some work happens between Init and Do, namely package
loading. That may exit with an error, meaning that in some cases the
user gets a confusing error instead of the correct one.
For example, using a GOOS typo, before showed:
$ GOOS=windwos go build
can't load package: package p: build constraints exclude all Go files in ...
And now:
$ GOOS=windwos go build
cmd/go: unsupported GOOS/GOARCH pair windwos/amd64
Also had to tweak TestGoEnv to modify GOOS as well as GOARCH. Otherwise,
on windows this would result in the invalid GOOS/GOARCH pair
windows/arm, which would error given that we now check that in non-build
commands such as "go env".
Fixes #21999.
Change-Id: Iff9890dea472bff0179a9d703d6f698a0e3187c1
Reviewed-on: https://go-review.googlesource.com/65656
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: David Crawshaw <crawshaw@golang.org>
Daniel Theophanes [Sun, 24 Sep 2017 00:04:51 +0000 (17:04 -0700)]
database/sql: update minor sql docs
Replace the work "session" with "connection" in docs. Fix
The ErrConnDone documentation. Clarify what the context is used
for in StmtContext.
Change-Id: I2f07e58d0cd6321b386a73b038cf6070cb8e2572
Reviewed-on: https://go-review.googlesource.com/65732 Reviewed-by: Ian Lance Taylor <iant@golang.org>
Daniel Martí [Sat, 23 Sep 2017 22:04:31 +0000 (23:04 +0100)]
cmd/compile: fix invalid switch case value panic
This is a regression introduced by myself in golang.org/cl/41852,
confirmed by the program that reproduces the crash that can be seen in
the added test.
Fixes #21988.
Change-Id: I18d5b2b3de63ced84db705b18490b00b16b59e02
Reviewed-on: https://go-review.googlesource.com/65655
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Keith Randall <khr@golang.org>
Alex Brainman [Thu, 21 Sep 2017 02:33:11 +0000 (12:33 +1000)]
cmd/go: ignore empty path elements in GOPATH
go command refuses to use GOPATH with empty path elements
(like %GOPATH%=C:\go;). But environment variable change dialog
on Windows 10 produces strings ending with ; (see issue #21928
for a picture). Just accept GOPATH with empty path elements,
and ignore all empty path elements.
Fixes #21928
Change-Id: I1d3c3a19274ed69204d29ae06c3e8ff8c57c1ca0
Reviewed-on: https://go-review.googlesource.com/65151
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
James Lawrence [Sat, 5 Aug 2017 10:04:19 +0000 (06:04 -0400)]
database/sql: add OpenDB to directly create a *DB without a DSN.
The current Open method limits the ability for driver maintainers
to expose options for their drivers by forcing all the configuration
to pass through the DSN in order to create a *DB.
This CL allows driver maintainers to write their own initialization
functions that return a *DB making configuration of the underlying
drivers easier.
Fixes #20268
Change-Id: Ib10b794f36a201bbb92c23999c8351815d38eedb
Reviewed-on: https://go-review.googlesource.com/53430 Reviewed-by: Daniel Theophanes <kardianos@gmail.com>
Run-TryBot: Daniel Theophanes <kardianos@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Daniel Martí [Sat, 23 Sep 2017 11:22:10 +0000 (12:22 +0100)]
cmd/compile: clarify adjustctxt inlining comment
The reason why adjustctxt wasn't being inlined was reported as:
function too complex: cost 92 exceeds budget 80
However, after tweaking the code to be under the budget limit, we see
the real blocker:
non-leaf function
There is little we can do about this one in particular at the moment.
Create a section with funcs that will need mid-stack inlining to be
inlineable, since this will likely come up again in other cases.
Change-Id: I3a8eb1546b289a060ac896506a007b0496946e84
Reviewed-on: https://go-review.googlesource.com/65650
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Joe Tsai [Fri, 22 Sep 2017 22:44:09 +0000 (15:44 -0700)]
encoding/json: cleanup detection of unexported embedded fields
CL 60410 fixes the compiler such that reflect.StructField.PkgPath
is non-empty if and only if the field is unexported.
Given that property, we can cleanup the logic in the json encoder
to avoid parsing the field name to detect export properties.
Updates #21122
Change-Id: Ic01b9c4ca76386774846b742b0c1b9b948f53e7c
Reviewed-on: https://go-review.googlesource.com/65550
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Austin Clements [Mon, 12 Jun 2017 15:12:12 +0000 (11:12 -0400)]
runtime: hide <autogenerated> methods from call stack
The compiler generates wrapper methods to forward interface method
calls (which are always pointer-based) to value methods. These
wrappers appear in the call stack even though they are an
implementation detail. This leaves ugly "<autogenerated>" functions in
stack traces and can throw off skip counts for stack traces.
Fix this by considering these runtime frames in printed stack traces
so they will only be printed if runtime frames are being printed, and
by eliding them from the call stack expansion used by CallersFrames
and Caller.
This removes the test for issue 4388 since that was checking that
"<autogenerated>" appeared in the stack trace instead of something
even weirder. We replace it with various runtime package tests.
Fixes #16723.
Change-Id: Ice3f118c66f254bb71478a664d62ab3fc7125819
Reviewed-on: https://go-review.googlesource.com/45412
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Austin Clements [Mon, 12 Jun 2017 18:24:16 +0000 (14:24 -0400)]
runtime: simplify stack walk in panicwrap
panicwrap currently uses runtime.Callers and runtime.CallersFrames to
find the name of its caller. Simplify this by using getcallerpc.
This will be important for #16723, since to fix that we're going to
make CallersFrames skip the wrapper method, which is exactly what
panicwrap needs to see.
Change-Id: Icb0776d399966e31595f3ee44f980290827e32a6
Reviewed-on: https://go-review.googlesource.com/45411
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Now that getcallerpc is a compiler intrinsic on x86 and non-x86
platforms don't need the argument, we can drop it.
Sadly, this doesn't let us remove any dummy arguments since all of
those cases also use getcallersp, which still takes the argument
pointer, but this is at least an improvement.
Ian Lance Taylor [Fri, 22 Sep 2017 19:03:52 +0000 (12:03 -0700)]
os/exec: remove protection against simultaneous Wait/Write
CL 31148 added code to protect again simultaneous calls to Close and
Wait when using the standard input pipe, to fix the race condition
described in issue #9307. That issue is a special case of the race
between Close and Write described by issue #7970. Since issue #7970
was not fixed, CL 31148 fixed the problem specific to os/exec.
Since then, issue #7970 has been fixed, so the specific fix in os/exec
is no longer necessary. Remove it, effectively reverting CL 31148 and
followup CL 33298.
Updates #7970
Updates #9307
Updates #17647
Change-Id: Ic0b62569cb0aba44b32153cf5f9632bd1f1b411a
Reviewed-on: https://go-review.googlesource.com/65490
Run-TryBot: Ian Lance Taylor <iant@golang.org> Reviewed-by: Daniel Martí <mvdan@mvdan.cc> Reviewed-by: Miguel Bernabeu <miguelbernadi@gmail.com> Reviewed-by: Russ Cox <rsc@golang.org> Reviewed-by: Joe Tsai <joetsai@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
David Chase [Mon, 24 Oct 2016 14:25:05 +0000 (10:25 -0400)]
cmd/compile: add intrinsic for reading caller's pc
First step towards removing the mandatory argument for
getcallerpc, which solves certain problems for the runtime.
This might also slightly improve performance.
Intrinsic enabled on 386, amd64, amd64p32,
runtime asm implementation removed on those architectures.
Now-superfluous argument remains in getcallerpc signature
(for a future CL; non-386/amd64 asm funcs ignore it).
Added getcallerpc to the "not a real function" test
in dcl.go, that story is a little odd with respect to
unexported functions but that is not this CL.
Ian Lance Taylor [Wed, 13 Sep 2017 22:53:47 +0000 (15:53 -0700)]
runtime: don't call lockOSThread for every cgo call
For a trivial benchmark with a do-nothing cgo call:
name old time/op new time/op delta
Call-4 64.5ns ± 7% 63.0ns ± 6% -2.25% (p=0.027 n=20+16)
Because Windows uses the cgocall mechanism to make system calls,
and passes arguments in a struct held in the m,
we need to do the lockOSThread/unlockOSThread in that code.
Because deferreturn was getting a nosplit stack overflow error,
change it to avoid calling typedmemmove.
Updates #21827.
Change-Id: I9b1d61434c44faeb29805b46b409c812c9acadc2
Reviewed-on: https://go-review.googlesource.com/64070
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Austin Clements <austin@google.com> Reviewed-by: David Crawshaw <crawshaw@golang.org>
Daniel Martí [Fri, 22 Sep 2017 11:21:36 +0000 (12:21 +0100)]
cmd/compile: add more runtime funcs to inline test
This is based from a list that Keith Randall provided in mid-2016. These
are all funcs that, at the time, were important and small enough that
they should be clearly inlined.
The runtime has changed a bit since then. Ctz16 and Ctz8 were removed,
so don't add them. stringtoslicebytetmp was moved to the backend, so
it's no longer a Go function. And itabhash was moved to itabHashFunc.
The only other outlier is adjustctxt, which is not inlineable at the
moment. I've added a TODO and will address it myself in a separate
commit.
While at it, error if any funcs in the input table are duplicated.
They're never useful and typos could lead to unintentionally thinking a
function is inlineable when it actually isn't.
And, since the lists are getting long, start sorting alphabetically.
Finally, rotl_31 is only defined on 64-bit architectures, and the added
runtime/internal/sys funcs are assembly on 386 and thus non-inlineable
in that case.
Updates #21851.
Change-Id: Ib99ab53d777860270e8fd4aefc41adb448f13662
Reviewed-on: https://go-review.googlesource.com/65351
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com> Reviewed-by: Keith Randall <khr@golang.org>
Daniel Martí [Fri, 22 Sep 2017 16:49:12 +0000 (17:49 +0100)]
cmd/compile: remove unused cases from switch
The first just falls through, and the default case does nothing. They
can be deleted.
Change-Id: I82ab1ce3acde0b8423334cfbf35f9e0c806cd494
Reviewed-on: https://go-review.googlesource.com/65410 Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
David du Colombier [Fri, 22 Sep 2017 13:50:03 +0000 (15:50 +0200)]
archive/tar: skip TestSparseFiles on Plan 9
CL 60871 added TestSparseFiles. This test is succeeding
on Plan 9 when executed on the ramfs file system, but
is failing when executed on the Fossil file system.
This may be due to an issue in the handling of sparse
files in the Fossil file system on Plan 9 that should
be investigated.
Updates #21977.
Change-Id: I177afff519b862a5c548e094203c219504852006
Reviewed-on: https://go-review.googlesource.com/65352 Reviewed-by: Ian Lance Taylor <iant@golang.org>
Carlos Eduardo Seo [Wed, 20 Sep 2017 20:33:26 +0000 (17:33 -0300)]
syscall: update syscall.Select to use newselect on ppc64x
Analog to the runtime package, syscall.Select should be using
newselect instead of select. This change addresses this problem and
regenerates zsyscall_linux_* for ppc64 and ppc64le.
Daniel Martí [Thu, 14 Sep 2017 14:51:18 +0000 (15:51 +0100)]
cmd/compile: collect reasons in inlining test
If we use -gcflags='-m -m', the compiler should give us a reason why a
func couldn't be inlined. Add the extra -m necessary for that extra info
and use it to give better test failures. For example, for the func in
the TODO:
--- FAIL: TestIntendedInlining (1.53s)
inl_test.go:104: runtime.nextFreeFast was not inlined: function too complex
We might increase the number of -m flags to get more information at some
later point, such as getting details on how close the func was to the
inlining budget.
Also started using regexes, as the output parsing is getting a bit too
complex for manual string handling.
While at it, also refactored the test to not buffer the entire output
into memory. This is fine in practice, but it won't scale well as we add
more packages or we depend more on the compiler's debugging output.
For example, "go build -a -gcflags='-m -m' std" prints nearly 40MB of
plaintext - and we only need to see the output line by line anyway.
Updates #21851.
Change-Id: I00986ff360eb56e4e9737b65a6be749ef8540643
Reviewed-on: https://go-review.googlesource.com/63810
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Joe Tsai [Thu, 21 Sep 2017 15:44:05 +0000 (08:44 -0700)]
archive/tar: perform test for hole-detection on specific builders
The test for hole-detection is heavily dependent on whether the
OS and underlying FS provides support for it.
Even on Linux, which has support for SEEK_HOLE and SEEK_DATA,
the underlying filesystem may not have support for it.
In order to avoid an ever-changing game of whack-a-mole,
we whitelist the specific builders that we expect the test to pass on.
Updates #21964
Change-Id: I7334e8532c96cc346ea83aabbb81b719685ad7e5
Reviewed-on: https://go-review.googlesource.com/65270
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com> Reviewed-by: Ian Lance Taylor <iant@golang.org>
cmd/nm: accept macho files which don't have symbol table in the archive
After https://golang.org/cl/64793, we started to include Mach-O object
files which don't have symbol table into cgo archive.
However, toolchains didn't handle those files yet.
Fixes #21959
Change-Id: Ibb2f6492f1fa59368f2dfd4cff19783997539875
Reviewed-on: https://go-review.googlesource.com/65170 Reviewed-by: Ian Lance Taylor <iant@golang.org>
Gabriel Aszalos [Thu, 21 Sep 2017 10:25:02 +0000 (12:25 +0200)]
bytes: add documentation to reader methods
Some methods that were used to implement various `io` interfaces in the
Reader were documented, whereas others were not. This change adds
documentation to all the missing methods used to implement these
interfaces.
Change-Id: I2dac6e328542de3cd87e89510651cd6ba74a7b7d
Reviewed-on: https://go-review.googlesource.com/65231 Reviewed-by: Ian Lance Taylor <iant@golang.org>
Joe Tsai [Thu, 21 Sep 2017 06:20:28 +0000 (23:20 -0700)]
archive/tar: make check for hole detection support more liberal
On most Unix OSes, lseek reports EINVAL when lacking SEEK_HOLE support.
However, there are reports that ENOTTY is reported instead.
Rather than tracking down every possible errno that may be used to
represent "not supported", just treat any non-nil error as meaning
that there is no support. This is the same strategy taken by the
GNU and BSD tar tools.
Fixes #21958
Change-Id: Iae68afdc934042f52fa914fca45f0ca89220c383
Reviewed-on: https://go-review.googlesource.com/65191
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Ben Shi [Wed, 20 Sep 2017 08:48:34 +0000 (08:48 +0000)]
cmd/compile: optimized ARM code with BFX/BFXU
BFX&BFXU were introduced in ARMv6T2. A single BFX or BFXU is
more efficiently than a pair of left-shift/right-shift in bit
field extraction.
This patch implements this optimization. And the benchmark tests
show big improvement in special cases and little change in total.
1. There is big improvement in a special test case.
name old time/op new time/op delta
BFX-4 665µs ± 1% 595µs ± 0% -10.61% (p=0.000 n=20+20)
(The test case: https://github.com/benshi001/ugo1/blob/master/bfx_test.go)
Michael Darakananda [Thu, 21 Sep 2017 00:25:35 +0000 (10:25 +1000)]
context: fix references to "d" in WithDeadline docs
Docs of WithDeadline refers to variable "d" which does not exist
in the docs.
This commit renames the time argument to "d" to make the doc work.
Change-Id: Ifd2c1be7d2e3f7dfb21cd9bb8ff7fc5039c8d3bd
Reviewed-on: https://go-review.googlesource.com/65130
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Change-Id: I4a528b7d53da1082e61523ebeba02c4c514a43a7
Reviewed-on: https://go-review.googlesource.com/64890
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
cmd/link: Grouping declaration of variables on ld/pe.go
Change-Id: I33284d3154db43b2b89418c5076df79407e7cf41
Reviewed-on: https://go-review.googlesource.com/60931
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Matthew Dempsky [Wed, 20 Sep 2017 22:22:21 +0000 (15:22 -0700)]
cmd/compile/internal/gc: update comment in plive.go
onebitwalktype1 no longer appears to be a bottleneck for the mentioned
test case. In fact, we appear to compile it significantly faster now
than Go 1.4 did (~1.8s vs ~3s).
Fixes #21951.
Change-Id: I315313e906092a7d6ff4ff60a918d80a4cff7a7f
Reviewed-on: https://go-review.googlesource.com/65110 Reviewed-by: Keith Randall <khr@golang.org>
Joe Tsai [Fri, 1 Sep 2017 09:57:46 +0000 (02:57 -0700)]
archive/tar: add Header.DetectSparseHoles and Header.PunchSparseHoles
To support the detection and creation of sparse files,
add two new methods:
func Header.DetectSparseHoles(*os.File) error
func Header.PunchSparseHoles(*os.File) error
DetectSparseHoles is intended to be used after FileInfoHeader
prior to serializing the Header with WriteHeader.
For each OS, it uses specialized logic to detect
the location of sparse holes. On most Unix systems, it uses
SEEK_HOLE and SEEK_DATA to query for the holes.
On Windows, it uses a specialized the FSCTL_QUERY_ALLOCATED_RANGES
syscall to query for all the holes.
PunchSparseHoles is intended to be used after Reader.Next
prior to populating the file with Reader.WriteTo.
On Windows, this uses the FSCTL_SET_ZERO_DATA syscall.
On other operating systems it simply truncates the file
to the end-offset of SparseHoles.
DetectSparseHoles and PunchSparseHoles are added as methods on
Header because they are heavily tied to the operating system,
for which there is already an existing precedence for
(since FileInfoHeader makes uses of OS-specific details).
Fixes #13548
Change-Id: I98a321dd1ce0165f3d143d4edadfda5e7db67746
Reviewed-on: https://go-review.googlesource.com/60871
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
- using FMA and AVX instructions if available to speed-up
Exp calculation on amd64
- using a data table instead of #define'ed constants because
these instructions do not support loading floating point immediates.
One has to use a memory operand / register.
- Benchmark results on Intel(R) Core(TM) i5-5200U CPU @ 2.20GHz:
Original vs New (non-FMA path)
name old time/op new time/op delta
Exp 16.0ns ± 1% 16.1ns ± 3% ~ (p=0.308 n=9+10)
Original vs New (FMA path)
name old time/op new time/op delta
Exp 16.0ns ± 1% 13.7ns ± 2% -14.80% (p=0.000 n=9+10)
Change-Id: I3d8986925d82b39b95ee979ae06f59d7e591d02e
Reviewed-on: https://go-review.googlesource.com/62590 Reviewed-by: Ilya Tocar <ilya.tocar@intel.com> Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
When debugging inliner with -m -m print cost of complex functions,
instead of simple "function too complex". This helps to understand,
how close to inlining is this particular function.
Ian Lance Taylor [Tue, 19 Sep 2017 20:53:20 +0000 (13:53 -0700)]
cmd/go: stop linking cgo objects together with ld -r
https://golang.org/cl/5822049 introduced the idea of linking together
all the cgo objects with -r, while also linking against -lgcc. This
was to fix http://golang.org/issue/3261: cgo code that requires libgcc
would break when using internal linking.
This approach introduced https://golang.org/issue/9510: multiple
different cgo packages could include the same libgcc object, leading
to a multiple definition error during the final link. That problem was
fixed by https://golang.org/cl/16741, as modified by
https://golang.org/cl/16993, which did the link against libgcc only
during the final link.
After https://golang.org/cl/16741, and, on Windows, the later
https://golang.org/cl/26670, ld -r no longer does anything useful.
So, remove it.
Doing this revealed that running ld -r on Darwin simplifies some
relocs by making them specific to a symbol rather than a section.
Correct the handling of unsigned relocations in internal linking mode
by offsetting by the symbol value. This only really comes up when
using the internal linker with C code that initializes a variable to
the address of a local constant, such as a C string (as in const char
*s = "str";). This change does not affect the normal case of external
linking, where the Add field is ignored. The test case is
misc/cgo/test/issue6612.go in internal linking mode.
The cmd/internal/goobj test can now see an external object with no
symbol table; fix it to not crash in that case.
Change-Id: I15e5b7b5a8f48136bc14bf4e1c4c473d5eb58062
Reviewed-on: https://go-review.googlesource.com/64793
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>
https://golang.org/cl/22598 made nextFreeFast inlinable.
But during https://golang.org/cl/63611 it was discovered, that it is no longer inlinable.
Reduce number of statements below inlining threshold to make it inlinable again.
Also update tests, to prevent regressions.
Doesn't reduce readability.
Michael Munday [Wed, 20 Sep 2017 16:12:33 +0000 (12:12 -0400)]
cmd/compile: fix large global variables in -linkshared mode on s390x
When rewriting loads and stores accessing global variables to use the
GOT we were making use of REGTMP (R10). Unfortunately loads and stores
with large offsets (larger than 20-bits) were also using REGTMP,
causing it to be clobbered and subsequently a segmentation fault.
This can be fixed by using REGTMP2 (R11) for the rewrite. This is fine
because REGTMP2 only has a couple of uses in the assembler (division,
high multiplication and storage-to-storage instructions). We didn't
use REGTMP2 originally because it used to be used more frequently,
in particular for stores of constants to memory. However we have now
eliminated those uses.
This was found while writing a test case for CL 63030. That test case
is included in this CL.
Matthew Dempsky [Tue, 19 Sep 2017 06:29:46 +0000 (23:29 -0700)]
cmd/compile: refactor onebitwalktype1
The existing logic tried to advance the offset for each variable's
width, but then tried to undo this logic with the array and struct
handling code. It can all be much simpler by only worrying about
computing offsets within the array and struct code.
While here, include a short-circuit for zero-width arrays to fix a
pedantic compiler failure case.
Passes toolstash-check.
Fixes #20739.
Change-Id: I98af9bb512a33e3efe82b8bf1803199edb480640
Reviewed-on: https://go-review.googlesource.com/64471
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
The previous code seems to have an off-by-1 in it somewhere, the
consequence being that we didn't properly preserve all of the old
buffer contents that we intended to.
After spending a while looking at the existing window-shifting logic,
I wasn't able to understand exactly how it was supposed to work or
where the issue was, so I rewrote it to be (at least IMO) more
obviously correct.
Fixes #21938.
Change-Id: I1ed7bbc1e1751a52ab5f7cf0411ae289586dc345
Reviewed-on: https://go-review.googlesource.com/64830
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
Matthew Dempsky [Tue, 19 Sep 2017 19:45:17 +0000 (12:45 -0700)]
cmd/compile/internal/types: simplify dclstack
We used to backup symbol declarations using complete Syms, but this
was unnecessary: very few of Sym's fields were actually needed. Also,
to restore a symbol, we had to re-Lookup the Sym in its Pkg.
By introducing a new dedicated dsym type for this purpose, we can
address both of these deficiencies.
Passes toolstash-check.
Change-Id: I39f3d672b301f84a3a62b9b34b4b2770cb25df79
Reviewed-on: https://go-review.googlesource.com/64811
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
net/http: net/http: doc that prefer "must" over "should"
See https://go-review.googlesource.com/c/go/+/59850
Change-Id: I9f0b6bc009eae86cbbdb56562ee4eb8d5eef653e
Reviewed-on: https://go-review.googlesource.com/61230 Reviewed-by: Tom Bergan <tombergan@google.com>
Michael Munday [Mon, 11 Sep 2017 20:23:06 +0000 (21:23 +0100)]
cmd/compile: stop rematerializable ops from clobbering flags
Rematerializable ops can be inserted after the flagalloc phase,
they must therefore not clobber flags. This CL adds a check to
ensure this doesn't happen and fixes the instances where it
does currently.
amd64: ADDQconst and ADDLconst were recently changed to be
rematerializable in CL 54393 (only in tip, not 1.9). That change
has been reverted.
s390x: MOVDaddr could clobber flags when using dynamic linking due
to a ADD with immediate instruction. Change the code generation to
use LA/LAY instead.
Matthew Dempsky [Tue, 19 Sep 2017 18:45:58 +0000 (11:45 -0700)]
cmd/compile: remove {Mark,Pop}dcl calls in bimport
These were previously only relevant for recording scoping level so
that invalid 'fallthrough' statements could be rejected. However,
that's handled differently since CL 61130 (in particular, there's no
use of types.Block anymore), so these calls can be safely removed.
Passes toolstash-check.
Change-Id: I8631b156594df85b8d39f57acad3ebcf099d52f9
Reviewed-on: https://go-review.googlesource.com/64810
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
Albert Nigmatzianov [Wed, 20 Sep 2017 14:23:11 +0000 (19:23 +0500)]
io: Add benchmarks for CopyN
Copied from CL 60630
Current results:
name time/op
CopyNSmall-4 2.20µs ±90%
CopyNLarge-4 136µs ±56%
name alloc/op
CopyNSmall-4 1.84kB ±21%
CopyNLarge-4 128kB ±10%
name allocs/op
CopyNSmall-4 1.00 ± 0%
CopyNLarge-4 1.00 ± 0%
Change-Id: If08c0132a773e936c9f61bff96e0aabf58006d31
Reviewed-on: https://go-review.googlesource.com/64932
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
for i := 0; i < b.N; i++ {
io.CopyN(buf, rd, (32*1024)+1)
rd.Reset(bs)
}
}
Change-Id: Id8d29e55758452c870cf372db640f07baec05849
Reviewed-on: https://go-review.googlesource.com/60630
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Gabriel Aszalos [Wed, 20 Sep 2017 09:10:26 +0000 (11:10 +0200)]
bytes: improve test readability
This CL improves the readability of the tests in the bytes package by
naming the `data` test variable `testString`, using the same convention
as its counterpart, `testBytes`.
It additionally removes some type casting which was unnecessary.
Change-Id: If38b5606ce8bda0306bae24498f21cb8dbbb6377
Reviewed-on: https://go-review.googlesource.com/64931
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Marvin Stenger [Thu, 31 Aug 2017 10:52:04 +0000 (12:52 +0200)]
cmd/dist: rename variables + functions
This belongs to a series of clean-up changes (see below) for cmd/dist.
This is change (9).
These changes include:
(1) apply minor fixes
(2) restore behavior of branchtag
(3) unleash bootstrap optimization for windows
(4) use standard generated code header
(5) remove trivial variables + functions
(6) move functions for the better
(7) simplify code segments
(8) use bytes.Buffer for code generation
(9) rename variables + functions
Change-Id: I9247433d7d07a2c99d15b0a4d23164bcbc042768
Reviewed-on: https://go-review.googlesource.com/61015
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Gabriel Aszalos [Wed, 20 Sep 2017 09:01:32 +0000 (11:01 +0200)]
bytes: correct message in test log
Change-Id: Ib731874b9a37ff141e4305d8ccfdf7c165155da6
Reviewed-on: https://go-review.googlesource.com/64930 Reviewed-by: Ian Lance Taylor <iant@golang.org>
Michael Munday [Thu, 14 Sep 2017 19:00:02 +0000 (20:00 +0100)]
cmd/compile: add s390x intrinsics for Ceil, Floor, Round and Trunc
Ceil, Floor and Trunc are pre-existing intrinsics. Round is a new
function and has been added as an intrinsic in this CL. All of the
functions can be implemented as a single 'LOAD FP INTEGER'
instruction, FIDBR, on s390x.
In general, there are no guarantee that `go` command exist on $PATH.
This CL tries to get `go` command from $GOROOT/bin instead.
There are three kinds of code we should handle:
For normal code, the CL implements goCmd() or goCmdName().
For unit tests, the CL uses testenv.GoTool() or testenv.GoToolPath().
For integration tests, the CL sets PATH=$GOROOT/bin:$PATH in cmd/dist.
Note that make.bash sets PATH=$GOROOT/bin:$PATH in the build process.
So this change is only useful when we use toolchain manually.
Updates #21875
Change-Id: I963b9f22ea732dd735363ececde4cf94a5db5ca2
Reviewed-on: https://go-review.googlesource.com/64650
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
This belongs to a series of clean-up changes (see below) for cmd/dist.
This is change (8).
These changes include:
(1) apply minor fixes
(2) restore behavior of branchtag
(3) unleash bootstrap optimization for windows
(4) use standard generated code header
(5) remove trivial variables + functions
(6) move functions for the better
(7) simplify code segments
(8) use bytes.Buffer for code generation
(9) rename variables + functions
(10) remove doc.go
Change-Id: I2d5a071eb8e14690325612271432fdc5f43b108b
Reviewed-on: https://go-review.googlesource.com/61014
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Samuel Tan [Tue, 19 Sep 2017 18:54:47 +0000 (11:54 -0700)]
html/template: prevent aliasing of parse Trees via AddParseTree
Check all associated templates in the set for an existing reference
to the given Tree in AddParseTree before assigning that reference
to a new or existing template. This prevents multiple html/template
Templates from referencing and modifying the same underlying Tree.
While there, fix a few existing unit tests so that they terminate
upon encountering unrecoverable failures.
Fixes #21844
Change-Id: I6b4f6996cf5467113ef94f7b91a6933dbbc21839
Reviewed-on: https://go-review.googlesource.com/64770
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Rob Pike <r@golang.org>
Marvin Stenger [Thu, 31 Aug 2017 10:50:57 +0000 (12:50 +0200)]
cmd/dist: simplify code segments
This belongs to a series of clean-up changes (see below) for cmd/dist.
This is change (7).
These changes include:
(1) apply minor fixes
(2) restore behavior of branchtag
(3) unleash bootstrap optimization for windows
(4) use standard generated code header
(5) remove trivial variables + functions
(6) move functions for the better
(7) simplify code segments
(8) use bytes.Buffer for code generation
(9) rename variables + functions
(10) remove doc.go
Change-Id: Ia3c33ef060b4baaef354b729ba82ed0b28e52857
Reviewed-on: https://go-review.googlesource.com/61013
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Sam Whited [Sat, 9 Sep 2017 15:49:04 +0000 (10:49 -0500)]
cmd/vet: don't warn on expected space in XML tag
The change in https://golang.org/cl/43295 added warning about spaces in
struct tags. However, in XML tags it is expected that there will be a
space between the namespace and the local name.
Change-Id: Ic31c3bdae30797f406f25c737b83bbe2de1ed1db
Reviewed-on: https://go-review.googlesource.com/62570
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Rob Pike <r@golang.org>
internal/testenv: take testing.TB instead of *testing.T in MustHave* and SkipFlaky*
Change-Id: I16475e9bb055b934302870ccb5136174dc3bc817
Reviewed-on: https://go-review.googlesource.com/64670
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Keith Randall [Mon, 18 Sep 2017 21:53:56 +0000 (14:53 -0700)]
cmd/compile: remove Symbol wrappers from Aux fields
We used to have {Arg,Auto,Extern}Symbol structs with which we wrapped
a *gc.Node or *obj.LSym before storing them in the Aux field
of an ssa.Value. This let the SSA part of the compiler distinguish
between autos and args, for example. We no longer need the wrappers
as we can query the underlying objects directly.
There was also some sloppy usage, where VarDef had a *gc.Node
directly in its Aux field, whereas the use of that variable had
that *gc.Node wrapped in an AutoSymbol. Thus the Aux fields didn't
match (using ==) when they probably should.
This sloppy usage cleanup is the only thing in the CL that changes the
generated code - we can get rid of some more unused auto variables if
the matching happens reliably.
Removing this wrapper also lets us get rid of the varsyms cache
(which was used to prevent wrapping the same *gc.Node twice).
reflect: fix pointer past-the-end in Call with zero-sized return value
If a function with nonzero frame but zero-sized return value is
Call'd, we may write a past-the-end pointer in preparing the
return Values. Fix by return the zero value for zero-sized
return value.
There was unprotected access to Logger.flag in log.Output which
could lead to data race in cases when log.SetFlags called simultaneously.
For example, "hot" switching on/off debug-mode for Logger by log.SetFlags
while application still writing logs.
Fixes #21935
Change-Id: I36be25f23cad44cde62ed1af28a30d276400e1b8
Reviewed-on: https://go-review.googlesource.com/64710 Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Matthew Dempsky [Tue, 19 Sep 2017 06:02:02 +0000 (23:02 -0700)]
cmd/compile: fix stack frame info for calls in receiver slot
Previously, after inlining a call, we made a second pass to rewrite
the AST's position information to record the inlined stack frame. The
call arguments were part of this AST, but it would be incorrect to
rewrite them too, so extra effort was made to temporarily remove them
while the position rewriting was done.
However, this extra logic was only done for regular arguments: it was
not done for receiver arguments. Consequently if m was inlined in
"f().m(g(), h())", g and h would have correct call frames, but f would
appear to be called by m.
The fix taken by this CL is to merge setpos into inlsubst and only
rewrite position information for nodes that were actually copied from
the original function AST body. As a side benefit, this eliminates an
extra AST pass and some AST walking code.
Fixes #21879.
Change-Id: I22b25c208313fc25c358d3a2eebfc9b012400084
Reviewed-on: https://go-review.googlesource.com/64470
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
Matthew Dempsky [Fri, 1 Sep 2017 21:55:15 +0000 (14:55 -0700)]
cmd/compile: eliminate OXFALL
Previously, we used OXFALL vs OFALL to distinguish fallthrough
statements that had been validated. Because in the Node AST we flatten
statement blocks, OXCASE and OXFALL needed to keep track of their
block scopes for this purpose.
Now that we have an AST that keeps these separate, we can just perform
the validation earlier.
Passes toolstash-check.
Fixes #14540.
Change-Id: I8421eaba16c2b3b72c9c5483b5cf20b14261385e
Reviewed-on: https://go-review.googlesource.com/61130
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
cmd/dist: test: use existing globals rather than environment variables
Change-Id: Ief6bad2d15461d455e7230eadd9b42b27d04ec8b
Reviewed-on: https://go-review.googlesource.com/64630
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
spec: state which predeclared types are defined or alias types (clarification)
When we introduced the distinction between "defined" and "alias" types
we retained the notion of a "named" type (any type with a name). The
predeclared types (which all have names) simply remained named types.
This CL clarifies the spec by stating excplicitly which predeclared
types are defined types (or at least "act" like defined types), and
which ones are alias types.
Found by running gofmt -s on the file in question.
Change-Id: I84511bd2bc75dff196930a7a87ecf5a2aca2fbb8
Reviewed-on: https://go-review.googlesource.com/64310 Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Samuel Tan [Wed, 2 Aug 2017 20:45:43 +0000 (13:45 -0700)]
html/template: explain URL filtering
Expand documentation in of the internal urlFilter function
to explain why URLs with schemes other than "http", "https",
and "mailto" are filtered out.
Fixes #20586
Change-Id: I1f65ff6e15fc4cd325489327c40f8c141904bf5c
Reviewed-on: https://go-review.googlesource.com/52853 Reviewed-by: Mike Samuel <mikesamuel@gmail.com> Reviewed-by: Ian Lance Taylor <iant@golang.org>
Joe Tsai [Thu, 31 Aug 2017 21:52:20 +0000 (14:52 -0700)]
archive/tar: add Reader.WriteTo and Writer.ReadFrom
To support the efficient packing and extracting of sparse files,
add two new methods:
func Reader.WriteTo(io.Writer) (int64, error)
func Writer.ReadFrom(io.Reader) (int64, error)
If the current archive entry is sparse and the provided io.{Reader,Writer}
is also an io.Seeker, then use Seek to skip past the holes.
If the last region in a file entry is a hole, then we seek to 1 byte
before the EOF:
* for Reader.WriteTo to write a single byte
to ensure that the resulting filesize is correct.
* for Writer.ReadFrom to read a single byte
to verify that the input filesize is correct.
The downside of this approach is when the last region in the sparse file
is a hole. In the case of Reader.WriteTo, the 1-byte write will cause
the last fragment to have a single chunk allocated.
However, the goal of ReadFrom/WriteTo is *not* the ability to
exactly reproduce sparse files (in terms of the location of sparse holes),
but rather to provide an efficient way to create them.
File systems already impose their own restrictions on how the sparse file
will be created. Some filesystems (e.g., HFS+) don't support sparseness and
seeking forward simply causes the FS to write zeros. Other filesystems
have different chunk sizes, which will cause chunk allocations at boundaries
different from what was in the original sparse file. In either case,
it should not be a normal expectation of users that the location of holes
in sparse files exactly matches the source.
For users that really desire to have exact reproduction of sparse holes,
they can wrap os.File with their own io.WriteSeeker that discards the
final 1-byte write and uses File.Truncate to resize the file to the
correct size.
Other reasons we choose this approach over special-casing *os.File because:
* The Reader already has special-case logic for io.Seeker
* As much as possible, we want to decouple OS-specific logic from
Reader and Writer.
* This allows other abstractions over *os.File to also benefit from
the "skip past holes" logic.
* It is easier to test, since it is harder to mock an *os.File.
Updates #13548
Change-Id: I0a4f293bd53d13d154a946bc4a2ade28a6646f6a
Reviewed-on: https://go-review.googlesource.com/60872
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>