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>
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.
Change-Id: I6871f69b5b914d23fd0b43a24d7c6fc928f4b716
Reviewed-on: https://go-review.googlesource.com/63330
Run-TryBot: Ilya Tocar <ilya.tocar@intel.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
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.
Change-Id: Ia672784dd48ed3b1ab46e390132f1094fe453de5
Reviewed-on: https://go-review.googlesource.com/65030
Run-TryBot: Ilya Tocar <ilya.tocar@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
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.
Change-Id: I13956f1f3ca258a7c8a7ff0a7570d2848adf7f68
Reviewed-on: https://go-review.googlesource.com/65011
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
No functional change; just making the code slightly more idiomatic.
Passes toolstash-check.
Change-Id: I66d14a8410bbecf260d0ea5683564aa413ce5747
Reviewed-on: https://go-review.googlesource.com/65070
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
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>
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>
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.
Fixes#21080.
Change-Id: Ia85c882afa2a820a309e93775354b3169ec6d034
Reviewed-on: https://go-review.googlesource.com/63030
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Ilya Tocar <ilya.tocar@intel.com>
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>
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>
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>
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.
name old time/op new time/op delta
Ceil 2.34ns ± 0% 0.85ns ± 0% -63.74% (p=0.000 n=5+4)
Floor 2.33ns ± 0% 0.85ns ± 1% -63.35% (p=0.008 n=5+5)
Round 4.23ns ± 0% 0.85ns ± 0% -79.89% (p=0.000 n=5+4)
Trunc 2.35ns ± 0% 0.85ns ± 0% -63.83% (p=0.029 n=4+4)
Change-Id: Idee7ba24a2899d12bf9afee4eedd6b4aaad3c510
Reviewed-on: https://go-review.googlesource.com/63890
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
This allows io.WriteString to make use of WriteString method
implemented by pp when writing a string to fmt.State.
Fixes#20786
Change-Id: Ice7a92bf303127ad87f05562217fa076f5c589ad
Reviewed-on: https://go-review.googlesource.com/61430
Reviewed-by: Rob Pike <r@golang.org>
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>
Also, rename some test cases, check (*os.File).Close
For #21706
Change-Id: Ie60c4d345b2259736c823dc6001c08affcdd86e7
Reviewed-on: https://go-review.googlesource.com/64510
Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
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>
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>
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>
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>
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).
Change-Id: I0dedf8f82f84bfee413d310342b777316bd1d478
Reviewed-on: https://go-review.googlesource.com/64452
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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.
Fixes#21717.
Change-Id: I5351cd86d898467170a888b4c3fc9392f0e7aa3b
Reviewed-on: https://go-review.googlesource.com/60811
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
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>
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>
We previously used bare strings, which made it difficult to see (and
to cross-reference) the set of allowed context values.
This change is purely cosmetic, but makes it easier for me to
understand how to address #21878.
updates #21878
Change-Id: I9027d94fd5997a0fe857c0055dea8719e1511f03
Reviewed-on: https://go-review.googlesource.com/63830
Run-TryBot: Bryan Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
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>
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>
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.
Fixes#21785.
Change-Id: Ia8ae133509eb5d738e6757b3442c9992355e3535
Reviewed-on: https://go-review.googlesource.com/64591
Reviewed-by: Russ Cox <rsc@golang.org>
This, in turn, to make it work with x/text’s
go generate.
Also eliminates need to manually update version
string in maketables.go.
Change-Id: Id5a8b8e27bdce5b1b5920eb9223a2d27b889149a
Reviewed-on: https://go-review.googlesource.com/63952
Run-TryBot: Marcel van Lohuizen <mpvl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Nigel Tao <nigeltao@golang.org>
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>
By setting both a valid size and alignment for broken recursive types,
we can appease some more safety checks and prevent compiler crashes.
Fixes#21882.
Change-Id: Ibaa137d8aa2c2a9d521462f144d7016c4abfd6e7
Reviewed-on: https://go-review.googlesource.com/64430
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
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>
The comment was a left-over from the long-past move
of these two packages from x/tools to the std lib.
Fixes#21791.
Change-Id: I65cbebf479e609be0204b58edb6506c6403aec9b
Reviewed-on: https://go-review.googlesource.com/64250
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>
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>
These are the last instructions missing to complete SSE3 support.
For reference what was missing was found by a tool [1]:
$ x86db-gogen list --extension SSE3 --not-known
ADDSUBPD xmmreg,xmmrm [rm: 66 0f d0 /r] PRESCOTT,SSE3,SO
ADDSUBPS xmmreg,xmmrm [rm: f2 0f d0 /r] PRESCOTT,SSE3,SO
[1] https://github.com/dlespiau/x86dbFixes#20293
Change-Id: Ib5a91bf64dcc5282cdb60eae740ae52b4db16ebd
Reviewed-on: https://go-review.googlesource.com/42990
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ilya Tocar <ilya.tocar@intel.com>
As per golint's suggestions.
Change-Id: Ie0c6ad9aa5dc69966a279562a341c7b095c47ede
Reviewed-on: https://go-review.googlesource.com/64192
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Change-Id: If7ecdc57f190f647bfc673bde8e66b4ef12aa906
Reviewed-on: https://go-review.googlesource.com/64190
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
The current generator is a simple LSFR, which showed strong
correlation in higher bits, as manifested by fastrandn().
Change it with xorshift64+, which is slightly more complex,
has a larger state, but has a period of 2^64-1 and is much better
at statistical tests. The version used here is capable of
passing Diehard and even SmallCrush.
Speed is slightly worse but is probably insignificant:
name old time/op new time/op delta
Fastrand-4 0.77ns ±12% 0.91ns ±21% +17.31% (p=0.048 n=5+5)
FastrandHashiter-4 13.6ns ±21% 15.2ns ±17% ~ (p=0.160 n=6+5)
Fastrandn/2-4 2.30ns ± 5% 2.45ns ±15% ~ (p=0.222 n=5+5)
Fastrandn/3-4 2.36ns ± 7% 2.45ns ± 6% ~ (p=0.222 n=5+5)
Fastrandn/4-4 2.33ns ± 8% 2.61ns ±30% ~ (p=0.126 n=6+5)
Fastrandn/5-4 2.33ns ± 5% 2.48ns ± 9% ~ (p=0.052 n=6+5)
Fixes#21806
Change-Id: I013bb37b463fdfc229a7f324df8fe2da8d286f33
Reviewed-on: https://go-review.googlesource.com/62530
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
