The inputs to a function are marked live at all times in the
liveness bitmaps, so that the garbage collector will not free
the things they point at and reuse the pointers, so that the
pointers shown in stack traces are guaranteed not to have
been recycled.
Unfortunately, no one told the register optimizer that the
inputs need to be preserved at all call sites. If a function
is done with a particular input value, the optimizer will stop
preserving it across calls. For single-word values this just
means that the value recorded might be stale. For multi-word
values like slices, the value recorded could be only partially stale:
it can happen that, say, the cap was updated but not the len,
or that the len was updated but not the base pointer.
Either of these possibilities (and others) would make the
garbage collector misinterpret memory, leading to memory
corruption.
This came up in a real program, in which the garbage collector's
'slice len ≤ slice cap' check caught the inconsistency.
Fixes#7944.
LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews, khr
https://golang.org/cl/100370045
This is joint work with Daniel Morsing.
In order for the register allocator to alias two variables, they must have the same width, stack offset, and etype. Code generation was altering a variable's etype in a few places. This prevented the variable from being moved to a register, which in turn prevented peephole optimization. This failure to alias was very common, with almost 23,000 instances just running make.bash.
This phenomenon was not visible in the register allocation debug output because the variables that failed to alias had the same name. The debugging-only change to bits.c fixes this by printing the variable number with its name.
This CL fixes the source of all etype mismatches for 6g, all but one case for 8g, and depressingly few cases for 5g. (I believe that extending CL 6819083 to 5g is a prerequisite.) Fixing the remaining cases in 8g and 5g is work for the future.
The etype mismatch fixes are:
* [gc] Slicing changed the type of the base pointer into a uintptr in order to perform arithmetic on it. Instead, support addition directly on pointers.
* [*g] OSPTR was giving type uintptr to slice base pointers; undo that. This arose, for example, while compiling copy(dst, src).
* [8g] 64 bit float conversion was assigning int64 type during codegen, overwriting the existing uint64 type.
Note that some etype mismatches are appropriate, such as a struct with a single field or an array with a single element.
With these fixes, the number of registerizations that occur while running make.bash for 6g increases ~10%. Hello world binary size shrinks ~1.5%. Running all benchmarks in the standard library show performance improvements ranging from nominal to substantive (>10%); a full comparison using 6g on my laptop is available at https://gist.github.com/josharian/8f9b5beb46667c272064. The microbenchmarks must be taken with a grain of salt; see issue 7920. The few benchmarks that show real regressions are likely due to issue 7920. I manually examined the generated code for the top few regressions and none had any assembly output changes. The few benchmarks that show extraordinary improvements are likely also due to issue 7920.
Performance results from 8g appear similar to 6g.
5g shows no performance improvements. This is not surprising, given the discussion above.
Update #7316
LGTM=rsc
R=rsc, daniel.morsing, bradfitz
CC=dave, golang-codereviews
https://golang.org/cl/91850043
The runtime was detecting the cycle already,
but we can give a better error without even
building the binary.
Fixes#7789.
LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/96290043
This change requires using SWIG version 3.0 or later. Earlier
versions of SWIG do not generate the pragmas required to use
the external linker.
Fixes#7155.
Fixes#7156.
LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/97120046
Before we used line 1 of the first source file.
This should be clearer.
Fixes#4388.
LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/92250044
<enter reason for undo>
««« original CL description
net: make use of SO_LINGER_SEC on darwin
Fixes#7971.
LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/92210044
»»»
TBR=iant
R=golang-codereviews
CC=golang-codereviews
https://golang.org/cl/96220049
If it's not used (such as on other systems or if softfloat
is disabled) the linker will discard it.
The alternative is to teach cmd/go that every binary
depends on math implicitly on arm. I started down that
path but it's too scary. If we're going to get dependencies
right we should get dependencies right.
Fixes#6994.
LGTM=bradfitz, dave
R=golang-codereviews, bradfitz, dave
CC=golang-codereviews
https://golang.org/cl/95290043
This is a trivial change to make use of an existing `nl` byte slice
containing a single '\n' character. It's already declared and
used in another place in this file, so it might as well be used
in the other location instead of
a new slice literal. There should be no change in behavior,
aside from potentially less allocations.
This is my first CL, so I wanted to use a simple, hopefully non-controversial,
minor improvement to get more comfortable with golang contribution process.
LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/97280043
<enter reason for undo>
««« original CL description
runtime/race: fix the link for the race detector.
LGTM=bradfitz
R=golang-dev, bradfitz
CC=golang-codereviews
https://golang.org/cl/100330043
»»»
TBR=minux
R=minux.ma
CC=golang-codereviews
https://golang.org/cl/96200044
list has been adding them one at a time haphazardly
(race and tags were there and documented; compiler
was there and undocumented).
clean -i needs -compiler in order to clean the
installed targets for alternate compilers.
Fixes#7302.
While we're here, tweak the language in the 'go get' docs
about build flags.
Fixes#7807.
LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/99130043
If you write:
var x = 3
then the compiler arranges for x to be initialized in the linker
with an actual 3 from the data segment, rather than putting
x in the bss and emitting init-time "x = 3" assignment code.
If you write:
var y = x
var x = 3
then the compiler is clever and treats this the same as if
the code said 'y = 3': they both end up in the data segment
with no init-time assignments.
If you write
var y = x
var x int
then the compiler was treating this the same as if the
code said 'x = 0', making both x and y zero and avoiding
any init-time assignment.
This copying optimization to avoid init-time assignment of y
is incorrect if 'var x int' doesn't mean 'x = 0' but instead means
'x is initialized in C or assembly code'. The program ends up
with 'y = 0' instead of 'y = the value specified for x in that other code'.
Disable the propagation if there is no initializer for x.
This comes up in some uses of cgo, because cgo generates
Go globals that are initialized in accompanying C files.
Fixes#7665.
LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/93200044
If the ... element type contained no pointers,
then the escape analysis did not track the ... itself.
This manifested in an escaping ...byte being treated
as non-escaping.
Fixes#7934.
LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/100310043
The register allocator decides which variables should be placed into registers by charging for each load/store and crediting for each use, and then selecting an allocation with minimal cost. NOPs will be eliminated, however, so using a variable in a NOP should not generate credit.
Issue 7867 arises from attempted registerization of multi-word variables because they are used in NOPs. By not crediting for that use, they will no longer be considered for registerization.
This fix could theoretically lead to better register allocation, but NOPs are rare relative to other instructions.
Fixes#7867.
LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/94810044
TestDialFailPDLeak was created for testing runtime-integrated netwrok
poller stuff and used during Go 1.2 development cycle. Unfortunately
it's still flakey because it depends on MemStats of runtime, not
pollcache directly, and MemStats accounts and revises its own stats
occasionally.
For now the codepaths related to runtime-intergrated network poller
are pretty stable, so removing this test case never suffers us.
Fixes#6553.
LGTM=josharian, iant
R=iant, josharian
CC=golang-codereviews
https://golang.org/cl/98080043
There was confusion in the behavior of json.Indent; This change
attempts to clarify the behavior by providing a bit more verbiage
to the documentation as well as provide an example function.
Fixes#7821.
LGTM=robert.hencke, adg
R=golang-codereviews, minux.ma, bradfitz, aram, robert.hencke, r, adg
CC=golang-codereviews
https://golang.org/cl/97840044
Existing test TestMaxOpenConns was failing occasionally, especially
with higher values of GOMAXPROCS.
Fixes#7532
LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/95130043
Number of lost samples was overcounted (never reset).
Also remove unused variable (it's trivial to restore it for debugging if needed).
LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews, rsc
https://golang.org/cl/96060043
The previous syscall constants regeneration on openbsd was conducted
with OpenBSD current 3 months ago and it missed updating openbsd/386.
This CL adds TIOCGSID for fixing the inconsistency between opensbd/amd64
and openbsd/386.
Update #7049
LGTM=iant
R=jsing, rsc, iant
CC=golang-codereviews
https://golang.org/cl/96960044
Where the spelling changed from British to
US norm (e.g., optimise -> optimize) it follows
the style in that file.
LGTM=adonovan
R=golang-codereviews, adonovan
CC=golang-codereviews
https://golang.org/cl/96980043
Because gotraceback is called early and often, its cache commits to the value of getenv("GOTRACEBACK") before getenv is even ready. So now we reset its cache once getenv becomes ready. Panicking programs now dump core again.
LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/97800045
If slice append is the only place where a program allocates,
then it will consume all available memory w/o triggering GC.
This was demonstrated in the issue.
Fixes#7922.
LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews, iant, khr
https://golang.org/cl/91010048
The monotonic clock patch changed all runtime times
to abstract monotonic time. As the result user-visible
MemStats.LastGC become monotonic time as well.
Restore Unix time for LastGC.
This is the simplest way to expose time.now to runtime that I found.
Another option would be to change time.now to C called
int64 runtime.unixnanotime() and then express time.now in terms of it.
But this would require to introduce 2 64-bit divisions into time.now.
Another option would be to change time.now to C called
void runtime.unixnanotime1(struct {int64 sec, int32 nsec} *now)
and then express both time.now and runtime.unixnanotime in terms of it.
Fixes#7852.
LGTM=minux.ma, iant
R=minux.ma, rsc, iant
CC=golang-codereviews
https://golang.org/cl/93720045
If systems actually read that much, using 2GB-1 will
result in misaligned subsequent reads. Use 1GB instead,
which will certainly keep reads aligned and which is
plenty large enough.
Update #7812.
LGTM=bradfitz
R=bradfitz
CC=golang-codereviews
https://golang.org/cl/94070044
This change allows us to give an hg tag such as "go1.3beta1" to
revisions in the main branch without breaking the build.
This is helpful for community members who want to build the beta
from source.
LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/90190044
The backing memory for >1 word interfaces was being scanned
conservatively.
LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/94000043
go test may call builder.init() multiple times which will create a new work directory. The cleanup needs to hoist the current work directory.
Fixes#7904.
LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/95900044
Not only ChST but also MeST (America/Metlakatla) is a zone
name containing a lower case letter.
LGTM=robert.hencke, r
R=golang-codereviews, robert.hencke, bradfitz, r
CC=golang-codereviews
https://golang.org/cl/99910043
Some system doesn't have libc.a available.
While we're at here, also export GOROOT in run.bash, so that
one doesn't need to set GOROOT to run run.bash.
LGTM=iant
R=iant
CC=golang-codereviews
https://golang.org/cl/99870043
For gccgo we rename exported functions so that the compiler
will make them visible. This CL adds a #define so that C
functions that #include "cgo_export.h" can use the expected
names of the function.
The test for this is the existing issue6833 test in
misc/cgo/test. Without this CL it fails when using
-compiler=gccgo.
LGTM=minux.ma, rsc
R=golang-codereviews, gobot, rsc, minux.ma
CC=golang-codereviews
https://golang.org/cl/91830046
This should make Go build without setting CC and CXX on newer FreeBSDs.
LGTM=iant
R=golang-codereviews, dave, gobot, iant
CC=golang-codereviews
https://golang.org/cl/89230045
This CL tries to fill the gap between Linux and other Unix-like systems
in the same way UDPConn and UnixConn already did.
Fixes#7887.
LGTM=iant
R=iant
CC=golang-codereviews
https://golang.org/cl/97810043
Use a real type for Gs instead of scanning them conservatively.
Zero the schedlink pointer when it is dead.
Update #7820
LGTM=rsc
R=rsc, dvyukov
CC=golang-codereviews
https://golang.org/cl/89360043
Previously we used strndup(3) to implement C.CString for gccgo. This
is wrong because strndup assumes the string to be null terminated,
and stops at the first null terminator. Instead, use malloc
and memmove to create a copy of the string, as we do in the
gc implementation.
LGTM=iant
R=iant
CC=golang-codereviews
https://golang.org/cl/96790047
A very smart developer at Gophercon just asked me to help debug
a problem and I was horrified to learn that he was using httputil's
ClientConn. I forgot ClientConn and ServerConn were even included
in Go 1! They should've been deleted.
Scare people away from using them. The net/http package does
not use them and they're unused, unmaintained and untouched in
4+ years.
LGTM=r
R=r, adg
CC=golang-codereviews
https://golang.org/cl/92790043
Remove an RUnlock of syscall.ForkLock with no matching RLock.
Holding ForkLock in netFD.dup is unnecessary: dupCloseOnExecOld
locks and unlocks the lock on its own and dupCloseOnExec doesn't
need the ForkLock to be held.
LGTM=iant
R=golang-codereviews, bradfitz, iant
CC=golang-codereviews
https://golang.org/cl/99800044
Previously Read wouldn't return once its internal input buffer
is filled with non-data bytes.
Fixes#7875.
LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/90820043
I fixed this data race regression in two ways: in net/http itself, and also
partially reverting the change from https://golang.org/cl/77580046 .
Previously a Read from a strings.Reader or bytes.Reader returning 0 bytes
would not be a memory write. After 77580046 it was. This reverts that back
in case others depended on that. Also adds tests.
Fixes#7856
LGTM=ruiu, iant
R=iant, ruiu
CC=golang-codereviews, gri
https://golang.org/cl/94740044
Godoc makes it look better this way; before, it all ran together into nonsense.
LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/90400045
Previously it would panic because of out-of-bound access
if s1 is longer than s2.
LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/90110043
TestVariousDeadlines1Proc was flaky on my system,
failing on about 5% of runs.
LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/89830045
This should have been part of 36eb4a62fbb6,
but I later discovered that addresses are all wrong.
Appropriate test added now.
LGTM=r
R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/89470043
`GOARCH=arm go tool 6c` used to give "<prog>: cannot use 6c with GOARCH=arm"
LGTM=r
R=golang-codereviews, r
CC=golang-codereviews
https://golang.org/cl/89330043
CL 89050043 only allows -ccflags for 'go test', this
CL really handles the flag like the other -??flags.
Many thanks to Dobrosław Żybort for pointing this out.
Fixes#7810 (again).
LGTM=iant, matrixik
R=golang-codereviews, iant, matrixik
CC=golang-codereviews
https://golang.org/cl/89230044
