The critical phase did not correctly maintain the use count
when two predecessors of a new critical block transmit the
same value.
Change-Id: Iba802c98ebb84e36a410721ec32c867140efb6d4
Reviewed-on: https://go-review.googlesource.com/20822
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Todd Neal <todd@tneal.org>
* This the simplest solution I could came up with
that doesn't required changing the compiler.
* The bound checks become constants now
so they are removed during opt phase.
Updates #14808
Change-Id: If32c33d7ec08bb400321b465015d152f0a5d3001
Reviewed-on: https://go-review.googlesource.com/20654
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Make sure we don't generate write barriers in runtime
code that is marked to forbid write barriers.
Implement the optimization that if we're writing a sliced
slice back to the location it came from, we don't need a
write barrier.
Fixes#14784
Change-Id: I04b6a3b2ac303c19817e932a36a3b006de103aaa
Reviewed-on: https://go-review.googlesource.com/20791
Reviewed-by: Austin Clements <austin@google.com>
Reduces size of archives in pkg/linux_amd64 by 1.4MB (3.2%),
slightly improving link time.
name old s/op new s/op delta
LinkCmdGo 0.52 ± 3% 0.51 ± 2% -0.65% (p=0.000 n=98+99)
Change-Id: I7e265f4d4dd08967c5c5d55c1045e533466bbbec
Reviewed-on: https://go-review.googlesource.com/20802
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Boolean expressions involving t.Thistuple were converted to use
t.Recv(), because it's a bit clearer and will hopefully reveal cases
where we could remove redundant calls to t.Recv() (in followup CLs).
The other cases were all converted to use t.Recvs().NumFields(),
t.Params().NumFields(), or t.Results().NumFields().
Change-Id: I4df91762e7dc4b2ddae35995f8dd604a52c09b09
Reviewed-on: https://go-review.googlesource.com/20796
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
We never need a type hash for a method type, so skip trying to
overwrite Thistuple.
Change-Id: I8de6480ba5fd321dfa134facf7661461d298840e
Reviewed-on: https://go-review.googlesource.com/20795
Reviewed-by: Russ Cox <rsc@golang.org>
This is an automated rewrite of all the calls of the form:
for f, it := IterFields(t); f != nil; f = it.Next() { ... }
Followup CLs will work on cleaning up the remaining cases.
Change-Id: Ic1005ad45ae0b50c63e815e34e507e2d2644ba1a
Reviewed-on: https://go-review.googlesource.com/20794
Reviewed-by: David Crawshaw <crawshaw@golang.org>
Analogous to the Nodes type used as a more space efficient []*Node
representation.
Passes toolstash -cmp.
Change-Id: I8341e45304777d6e4200bd36dadc935b07ccf3ff
Reviewed-on: https://go-review.googlesource.com/20793
Reviewed-by: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
For every string constant the compiler was creating 2 Sym's and 2
Node's. It would never refer to them again, but would keep them alive
in gostringpkg. This changes the code to just use obj.LSym's instead.
When compiling x/tools/go/types, this yields about a 15% reduction in
the number of calls to newname and a 3% reduction in the total number of
Node objects. Unfortunately I couldn't see any change in compile time,
but reducing memory usage is desirable anyhow.
Passes toolstash -cmp.
Change-Id: I24f1cb1e6cff0a3afba4ca66f7166874917a036b
Reviewed-on: https://go-review.googlesource.com/20792
Reviewed-by: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This should probably be considered "experimental" at this stage, but
what it needs is feedback from adventurous adopters. I think the data
structure used for describing escape reasons might be extendable to
allow a cleanup of the underlying algorithms, which suffers from
insufficiently separated concerns (the graph does not deal well with
escape level adjustments, so it is augmented by a second custom-walk
portion of the "flood" phase. It would be better to put it all,
including level adjustments, in a single graph structure, and then
simply flood the graph.
Tweaked to avoid allocations in the no-logging case.
Modified run.go to ignore lines with leading "#" in the output (since
it can never match a line), and in -update_errors to ignore leading
tabs in output lines and to normalize embedded filenames.
Currently requires -m -m because otherwise the noise/update
burden for the other escape tests is considerable.
There is a partial test. Existing escape analysis tests seem to
cover all except the panic case and what looks like it might be
unreachable code in escape analysis.
Fixes#10526.
Change-Id: I2524fdec54facae48b00b2548e25d9e46fcaf832
Reviewed-on: https://go-review.googlesource.com/18041
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
If a phi has duplicate arguments, then the new block that is constructed
to remove the critical edge can be used for all of the duplicate
arguments.
read-only data = -904 bytes (-0.058308%)
global text (code) = -2240 bytes (-0.060056%)
Total difference -3144 bytes (-0.056218%)
Change-Id: Iee3762744d6a8c9d26cdfa880bb23feb62b03c9c
Reviewed-on: https://go-review.googlesource.com/20746
Run-TryBot: Todd Neal <todd@tneal.org>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Between the enumeration of fdsToClose in the parent and the
closing of fds in the child, it's possible for a file to be
closed in another thread. If that file descriptor is reused
when opening the child-parent status pipe, it will be closed
prematurely in the child and the forkExec gets out of sync.
This has been observed to cause failures in builder tests
when the link step of a build is started before the compile
step has run, with "file does not exist" messages as the
visible symptom.
The simple workaround is to check against closing the pipe.
A more comprehensive solution would be to rewrite the fd
closing code to avoid races, along the lines of the long
ago proposed https://golang.org/cl/57890043 - but meanwhile
this correction will prevent some builder failures.
Change-Id: I4ef5eaea70c21d00f4df0e0847a1c5b2966de7da
Reviewed-on: https://go-review.googlesource.com/20800
Run-TryBot: David du Colombier <0intro@gmail.com>
Reviewed-by: David du Colombier <0intro@gmail.com>
Separate unicode formatting into its own fmt_unicode function.
Remove the fmtUnicode wrapper and the f.unicode and f.uniQuote
flags that are not needed anymore. Remove mangling and restoring
of the precision and sharp flags.
Removes the buffer copy needed for %#U by moving
the character encoding before the number encoding.
Changes the behavior of plus and space flag to have
no effect instead of printing a plus or space before "U+".
Always print at least four digits after "U+"
even if precision is set to less than 4.
Change-Id: If9a0ee79e9eca2c76f06a4e0fdd75d98393899ac
Reviewed-on: https://go-review.googlesource.com/20574
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Keep track of how many uses each Value has. Each appearance in
Value.Args and in Block.Control counts once.
The number of uses of a value is generically useful to
constrain rewrite rules. For instance, we might want to
prevent merging index operations into loads if the same
index expression is used lots of times.
But I have one use in particular for which the use count is required.
We must make sure we don't combine ops with loads if the load has
more than one use. Otherwise, we may split a single load
into multiple loads and that breaks perceived behavior in
the presence of races. In particular, the load of m.state
in sync/mutex.go:Lock can't be done twice. (I have a separate
CL which triggers the mutex failure. This CL has a test which
demonstrates a similar failure.)
Change-Id: Icaafa479239f48632a069d0c3f624e6ebc6b1f0e
Reviewed-on: https://go-review.googlesource.com/20790
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Todd Neal <todd@tneal.org>
When building shared libraries, all symbols on Allsym are marked reachable.
What I didn't realize was that this includes the ".dup" symbols created when
"dupok" symbols are read from multiple package files. This breaks now because
deadcode makes some assumptions that fail for these ".dup" symbols, but in any
case was a bad idea -- I suspect this change makes libstd.so a bunch smaller,
but creating it was broken before this CL so I can't be sure.
This change simply stops adding these symbols to Allsym, which might make some
of the many iterations over Allsym the linker does a touch quicker, although
that's not the motivation here.
Add a test that no symbols called ".dup" makes it into the runtime shared
library.
Fixes#14841
Change-Id: I65dd6e88d150a770db2d01b75cfe5db5fd4f8d25
Reviewed-on: https://go-review.googlesource.com/20780
Run-TryBot: Michael Hudson-Doyle <michael.hudson@canonical.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Receiver parameters generally aren't relevant to the function
signature type. In particular:
1. When checking whether a type's method implements an interface's
method, we specifically want to ignore the receiver parameters,
because they'll be different.
2. When checking interface type equality, interface methods always
use the same "fakethis" *struct{} type as their receiver.
3. Finally, method expressions and method values degenerate into
receiver-less function types.
The only case where we care about receiver types matching is in
addmethod, which is easily handled by adding an extra Eqtype check of
the receiver parameters. Also, added a test for this, since
(surprisingly) there weren't any.
As precedence, go/types.Identical ignores receiver parameters when
comparing go/types.Signature values.
Notably, this allows us to slightly simplify the "implements"
function, which is used for checking whether type/interface t
implements interface iface. Currently, cmd/compile actually works
around Eqtype's receiver parameter checking by creating new throwaway
TFUNC Types without the receiver parameter.
(Worse, the compiler currently only provides APIs to build TFUNC Types
from Nod syntax trees, so building those throwaway types also involves
first building throwaway syntax trees.)
Passes toolstash -cmp.
Change-Id: Ib07289c66feacee284e016bc312e8c5ff674714f
Reviewed-on: https://go-review.googlesource.com/20602
Reviewed-by: Robert Griesemer <gri@golang.org>
Add a C.CBytes function to copy a Go byte slice into C memory. This
returns an unsafe.Pointer, since that is what needs to be passed to
C.free, and the data is often opaque bytes anyway.
Fixes#14838
Change-Id: Ic7bc29637eb6f1f5ee409b3898c702a59833a85a
Reviewed-on: https://go-review.googlesource.com/20762
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Currently we generate write barriers when the right side of an
assignment is a global function. This doesn't fall into the existing
case of storing an address of a global because we haven't lowered the
function to a pointer yet.
This write barrier is unnecessary, so eliminate it.
Fixes#13901.
Change-Id: Ibc10e00a8803db0fd75224b66ab94c3737842a79
Reviewed-on: https://go-review.googlesource.com/20772
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
c2go translated writing and advancing a pointer using slices.
Switch to something more idiomatic.
It is also more efficient, but not enough to matter.
Change-Id: I67709632ac53253615a35365824ae97bbe5458d5
Reviewed-on: https://go-review.googlesource.com/20767
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
The parser code was not reachable ever since some of the lexer cleanups.
We could recognize '~' in the lexer, complain, and return a '^' instead,
but it's been a few years since Go was new and this may have been a use-
ful error. The lexer complains with "illegal character U+007E '~'" which
is good enough.
For #13244.
Change-Id: Ie3283738486eb6f8462d594f2728ac98333c0520
Reviewed-on: https://go-review.googlesource.com/20768
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Use a local variable instead.
Passes toolstash -cmp.
Change-Id: I9623a40ff0d568f11afd1279b6aaa1c33eda644c
Reviewed-on: https://go-review.googlesource.com/20730
Reviewed-by: Ian Lance Taylor <iant@golang.org>
We're about to add another root marking job that needs to happen only
during the first markroot pass (whether that's concurrent or STW),
just like finalizer scanning. Rather than introducing another flag
that has the same value as finalizersDone, just rename finalizersDone
to markrootDone.
Change-Id: I535356c6ea1f3734cb5b6add264cb7bf48de95e8
Reviewed-on: https://go-review.googlesource.com/20043
Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Currently shinkstack is only safe during STW because it adjusts
channel-related stack pointers and moves send/receive stack slots
without synchronizing with the channel code. Make it safe to use when
the world isn't stopped by:
1) Locking all channels the G is blocked on while adjusting the sudogs
and copying the area of the stack that may contain send/receive
slots.
2) For any stack frames that may contain send/receive slot, using an
atomic CAS to adjust pointers to prevent races between adjusting a
pointer in a receive slot and a concurrent send writing to that
receive slot.
In principle, the synchronization could be finer-grained. For example,
we considered synchronizing around the sudogs, which would allow
channel operations involving other Gs to continue if the G being
shrunk was far enough down the send/receive queue. However, using the
channel lock means no additional locks are necessary in the channel
code. Furthermore, the stack shrinking code holds the channel lock for
a very short time (much less than the time required to shrink the
stack).
This does not yet make stack shrinking concurrent; it merely makes
doing so safe.
This has negligible effect on the go1 and garbage benchmarks.
For #12967.
Change-Id: Ia49df3a8a7be4b36e365aac4155a2416b94b988c
Reviewed-on: https://go-review.googlesource.com/20042
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
Currently, locking a G's stack by setting its status to _Gcopystack or
_Gscan is unordered with respect to channel locks. However, when we
make stack shrinking concurrent, stack shrinking will need to lock the
G and then acquire channel locks, which imposes an order on these.
Document this lock ordering and fix closechan to respect it.
Everything else already happens to respect it.
For #12967.
Change-Id: I4dd02675efffb3e7daa5285cf75bf24f987d90d4
Reviewed-on: https://go-review.googlesource.com/20041
Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Currently sudog.elem is never accessed concurrently, so in several
cases we drop the channel lock just before reading/writing the
sent/received value from/to sudog.elem. However, concurrent stack
shrinking is going to have to adjust sudog.elem to point to the new
stack, which means it needs a way to synchronize with accesses to
sudog.elem. Hence, add sudog.elem to the fields protected by
hchan.lock and scoot the unlocks down past the uses of sudog.elem.
While we're here, better document the channel synchronization rules.
For #12967.
Change-Id: I3ad0ca71f0a74b0716c261aef21b2f7f13f74917
Reviewed-on: https://go-review.googlesource.com/20040
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
With concurrent stack shrinking, the stack can move the instant after
a G enters _Gwaiting. There are only two places that put a G into
_Gwaiting: gopark and newstack. We fixed uses of gopark. This commit
fixes newstack by simplifying its G transitions and, in particular,
eliminating or narrowing the transient _Gwaiting states it passes
through so it's clear nothing in the G is accessed while in _Gwaiting.
For #12967.
Change-Id: I2440ead411d2bc61beb1e2ab020ebe3cb3481af9
Reviewed-on: https://go-review.googlesource.com/20039
Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
gopark calls the unlock function after setting the G to _Gwaiting.
This means it's generally unsafe to access the G's stack from the
unlock function because the G may start running on another P. Once we
start shrinking stacks concurrently, a stack shrink could also move
the stack the moment after it enters _Gwaiting and before the unlock
function is called.
Document this restriction and fix the two places where we currently
violate it.
This is unlikely to be a problem in practice for these two places
right now, but they're already skating on thin ice. For example, the
following sequence could in principle cause corruption, deadlock, or a
panic in the select code:
On M1/P1:
1. G1 selects on channels A and B.
2. selectgoImpl calls gopark.
3. gopark puts G1 in _Gwaiting.
4. gopark calls selparkcommit.
5. selparkcommit releases the lock on channel A.
On M2/P2:
6. G2 sends to channel A.
7. The send puts G1 in _Grunnable and puts it on P2's run queue.
8. The scheduler runs, selects G1, puts it in _Grunning, and resumes G1.
9. On G1, the sellock immediately following the gopark gets called.
10. sellock grows and moves the stack.
On M1/P1:
11. selparkcommit continues to scan the lock order for the next
channel to unlock, but it's now reading from a freed (and possibly
reused) stack.
This shouldn't happen in practice because step 10 isn't the first call
to sellock, so the stack should already be big enough. However, once
we start shrinking stacks concurrently, this reasoning won't work any
more.
For #12967.
Change-Id: I3660c5be37e5be9f87433cb8141bdfdf37fadc4c
Reviewed-on: https://go-review.googlesource.com/20038
Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Currently the g.waiting list created by a select is in poll order.
However, nothing depends on this, and we're going to need access to
the channel lock order in other places shortly, so modify select to
put the waiting list in channel lock order.
For #12967.
Change-Id: If0d38816216ecbb37a36624d9b25dd96e0a775ec
Reviewed-on: https://go-review.googlesource.com/20037
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
Currently the select lock order is a []*hchan. We're going to need to
refer to things other than the channel itself in lock order shortly,
so switch this to a []uint16 of indexes into the select cases. This
parallels the existing representation for the poll order.
Change-Id: I89262223fe20b4ddf5321592655ba9eac489cda1
Reviewed-on: https://go-review.googlesource.com/20036
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Given a G, there's currently no way to find the channel it's blocking
on. We'll need this information to fix a (probably theoretical) bug in
select and to implement concurrent stack shrinking, so record the
channel in the sudog.
For #12967.
Change-Id: If8fb63a140f1d07175818824d08c0ebeec2bdf66
Reviewed-on: https://go-review.googlesource.com/20035
Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
gcMarkRootCheck is too expensive to do during mark termination.
However, since it's a useful check and it complements checkmark mode
nicely, enable it during mark termination is checkmark is enabled.
Change-Id: Icd9039e85e6e9d22747454441b50f1cdd1412202
Reviewed-on: https://go-review.googlesource.com/20663
Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
I was wondering why cmd/go includes the HTTP server implementations.
Dumping the linker's deadcode dependency graph into a file and doing
some graph analysis, I found that the only reason cmd/go included an
HTTP server was because the maxBytesReader type (used by both the HTTP
transport & HTTP server) did a static type assertion to an HTTP server
type.
Changing it to a interface type assertion reduces the size of cmd/go
by 533KB (5.2%)
On linux/amd64, cmd/go goes from 10549200 to 10002624 bytes.
Add a test too so this doesn't regress. The test uses cmd/go as the
binary to test (a binary which needs the HTTP client but not the HTTP
server), but this change and test are equally applicable to any such
program.
Change-Id: I93865f43ec03b06d09241fbd9ea381817c2909c5
Reviewed-on: https://go-review.googlesource.com/20763
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Step 2 of stream-lining parameter parsing
- do parameter validity checks in parser
- two passes instead of multiple (and theoretically quadratic) passes
when checking parameters
- removes the need for OKEY and some ONONAME nodes in those passes
This removes allocation of ~123K OKEY (incl. some ONONAME) nodes
out of a total of ~10M allocated nodes when running make.bash, or
a reduction of the number of alloacted nodes by ~1.2%.
Change-Id: I4a8ec578d0ee2a7b99892ac6b92e56f8e0415f03
Reviewed-on: https://go-review.googlesource.com/20748
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Robert Griesemer <gri@golang.org>
