Nick Patavalis [Sun, 11 Mar 2018 17:11:33 +0000 (19:11 +0200)]
os: use poller when NewFile is called with a blocking descriptor.
If NewFile is called with a file descriptor that is already set to
non-blocking mode, it tries to return a pollable file (one for which
SetDeadline methods work) by adding the filedes to the poll/netpoll
mechanism. If called with a filedes in blocking mode, it returns a
non-pollable file, as it always did.
Fixes #22939
Updates #24331
Change-Id: Id54c8be1b83e6d35e14e76d7df0e57a9fd64e176
Reviewed-on: https://go-review.googlesource.com/100077
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
David Chase [Thu, 5 Apr 2018 20:14:42 +0000 (16:14 -0400)]
cmd/compile: use Block.Likely to put likely branch first
When a neither of a conditional block's successors follows,
the block must end with a conditional branch followed by a
an unconditional branch. If the (conditional) branch is
"unlikely", invert it and swap successors to make it
likely instead.
This doesn't matter to most benchmarks on amd64, but in one
instance on amd64 it caused a 30% improvement, and it is
otherwise harmless. The problematic loop is
for i := 0; i < w; i++ {
if pw[i] != 0 {
return true
}
}
compiled under GOEXPERIMENT=preemptibleloops
This the very worst-case benchmark for that experiment.
Also in this CL is a commoning up of heavily-repeated
boilerplate, which made it much easier to see that the
changes were applied correctly. In the future this should
allow un-exporting of SSAGenState.Branches once the
boilerplate-replacement is done everywhere.
TestServerDuplicateBackgroundRead has been causing crashes on the
netbsd-arm-bsiegert builder, with the system becoming completely
unresponsive (probably deadlocked). Skip this test while the crash
is under investigation.
Upstream bug report is http://gnats.netbsd.org/53173.
Ben Shi [Tue, 20 Mar 2018 08:25:08 +0000 (08:25 +0000)]
cmd/internal/obj/arm64: support SWPD/SWPW/SWPH/SWPB
SWPD/SWPW/SWPH/SWPB were introduced in ARMv8.1. They swap content
of register and memory atomically. And their difference is
SWPD: 64-bit double word data
SWPW: 32-bit word data (zero extended to 64-bit)
SWPH: 16-bit half word data (zero extended to 64-bit)
SWPB: 8-bit byte data (zero extended to 64-bit)
In #17528 it was discussed (off-topic to the actual issue) to reserve
GOARCH names for the RISC-V architecture. With the first RISC-V
Linux-capable development boards released (e.g. HiFive Unleashed),
Linux distributions being ported to RISC-V (e.g. Debian, Fedora) and
RISC-V support being added to gccgo (CL 96377), it becomes more likely
that Go software (and maybe Go itself) will be ported as well.
Add riscv and riscv64 (which is already used by gccgo), so Go 1.11 will
already recognize "*_riscv{,64}.go" as reserved files.
Change-Id: I042aab19c68751d82ea513e40f7b1d7e1ad924ea
Reviewed-on: https://go-review.googlesource.com/106256
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>
fanzha02 [Tue, 20 Mar 2018 03:53:21 +0000 (03:53 +0000)]
internal/bytealg: add optimized Compare for arm64
Use LDP instructions to load 16 bytes per loop when the source length is long. Specially
process the 8 bytes length, 4 bytes length and 2 bytes length to get a better performance.
Alberto Donizetti [Wed, 11 Apr 2018 08:50:09 +0000 (10:50 +0200)]
cmd/go: document GOTOOLDIR environment variable
Also, make the variables list sorted.
Fixes #24794
Change-Id: I55f77004b00391875d26df8e55e54d79cef168dc
Reviewed-on: https://go-review.googlesource.com/106255 Reviewed-by: Ian Lance Taylor <iant@golang.org>
Rob Pike [Tue, 10 Apr 2018 23:49:32 +0000 (09:49 +1000)]
doc/install.html: address comments from review of previous edit
Point out that one can just run the commands now; it's not necessary
to log out first.
Change-Id: I48d0cc0273d97ba54ce59b3a3bbcae0b5af9aaef
Reviewed-on: https://go-review.googlesource.com/106195 Reviewed-by: Ian Lance Taylor <iant@golang.org>
We'll always generate method expression wrappers for declared
interface types in their own package, so no need to generate them in
downstream packages.
Noticed by gri@ while looking into #21282.
Change-Id: I4fb7051b4e15297933da05fdd2b111d6b8f4178e
Reviewed-on: https://go-review.googlesource.com/106175
Run-TryBot: Matthew Dempsky <mdempsky@google.com> Reviewed-by: Robert Griesemer <gri@golang.org>
go/doc: tune association of a function with a type
Previously, we used to associate a function with its first returned type
assuming that it is a factory function for that type.
However, a function may return multiple types in which case it is usually
doing something else. Check for multiple return types, and treat it as
a normal function in that case. Maintain same behavior if the function
returns just one type.
Fixes #12839
Change-Id: Ic4ac11d322996f216f593b71f4e61ad4270d5213
Reviewed-on: https://go-review.googlesource.com/105575 Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Hana Kim [Wed, 4 Apr 2018 18:24:02 +0000 (14:24 -0400)]
cmd/trace: pprof computation for span types
/spanio, /spanblock, /spansched, /spansyscall provide
the pprof-style summary of span execution's
io, block, scheduling, syscall latency distributions
respectively.
The computation logic for /io, /block, /sched, /syscall
analysis was refactored and extended for reuse in these
new types of analysis. Upon the analysis query, we create
a map of goroutine id to time intervals based on the query
parameter, that represents the interesting time intervals
of matching goroutines. Only the events from the matching
goroutines that fall into the intervals are considered
in the pprof computation.
The new endpoints are not yet hooked into other span
analysis page (e.g. /userspan) yet.
Vlad Krasnov [Fri, 9 Mar 2018 00:07:42 +0000 (16:07 -0800)]
crypto/elliptic: improve P256 implementation on amd64 a bit
Minor modifications to the optimized amd64 implememntation.
* Reduce window size: reduces size of the lookup tables by 40%
* Revised scalar inversion formula, with less operations
* Field square function now uses intental loop, saving call overhead
This change will serve as a basis for an arm64 implementation.
Mike Samuel [Tue, 23 Jan 2018 19:27:47 +0000 (14:27 -0500)]
net/http: don't sniff Content-type in Server when X-Content-Type-Options:nosniff
The docs for ResponseWriter.Write say
// If the Header
// does not contain a Content-Type line, Write adds a Content-Type set
// to the result of passing the initial 512 bytes of written data to
// DetectContentType.
The header X-Content-Type-Options:nosniff is an explicit directive that
content-type should not be sniffed.
This changes the behavior of Response.WriteHeader so that, when
there is an X-Content-Type-Options:nosniff header, but there is
no Content-type header, the following happens:
1. A Content-type:application/octet-stream is added
2. A warning is logged via the server's logging mechanism.
Previously, a content-type would have been silently added based on
heuristic analysis of the first 512B which might allow a hosted
GIF like http://www.thinkfu.com/blog/gifjavascript-polyglots to be
categorized as JavaScript which might allow a CSP bypass, loading
as a script despite `Content-Security-Policy: script-src 'self' `.
----
https://fetch.spec.whatwg.org/#x-content-type-options-header
defines the X-Content-Type-Options header.
["Polyglots: Crossing Origins by Crossing Formats"](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.905.2946&rep=rep1&type=pdf)
explains Polyglot attacks in more detail.
Elias Naur [Sat, 7 Apr 2018 15:22:43 +0000 (17:22 +0200)]
misc/ios: make detect.go more robust
To enable the exec wrapper go_darwin_arm_exec.go to run binaries
on iOS devices, the GOIOS_DEV_ID variable needs to be set to a code
signing identity. The program detect.go attempts to detect suitable
values for GOIOS_DEV_ID (along with GOIOS_APP_ID and GOIOS_TEAM_ID).
Before this change, detect.go would use "security find-identity
-p codesigning -v" to list all available identities for code signing
and pick the first one with "iPhone Developer" in its name. However,
that pick might be invalid since if it was replaced by an identity
issued later.
Instead of attempting to find an identity from the "security
find-identity" list, use the identity from the CommonName in the
embedded certificate in the provisioning file. The CommonName only
lists the identity name (iPhone Developer: xxx@xxx (2754T98W8E)),
not the fingerprint (FC6D96F24A3223C98BF7A2C2C5194D82E04CD23E), but
fortunately the codesign tool accepts both.
Identity names may not be unique, as demonstrated by the example,
but that will result in an ambiguity error at codesigning instead of
a more obscure error about an invalid identity when
go_darwin_arm_exec.go runs a binary.
The fix is then to delete the invalid identity from the system
keychain.
While here, find all connected devices instead of the first connected
and only consider provision files that covers them all. This matters
for the mobile builder where two devices are connected.
Change-Id: I6beb59ace3fc5e071ba76222a20a607765943989
Reviewed-on: https://go-review.googlesource.com/105436
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
After CL 104636 the feature flags in internal/cpu are initialized before
alginit and can now be used for aeshash feature detection. Also remove
now unused runtime variables:
x86:
support_ssse3
support_sse42
support_aes
arm64:
support_aes
Elias Naur [Tue, 10 Apr 2018 11:26:05 +0000 (13:26 +0200)]
misc/ios,runtime/cgo: remove SIGINT handshake for the iOS exec wrapper
Once upon a time, the iOS exec wrapper needed to change the current
working directory for the binary being tested. To allow that, the
runtime raised a SIGINT signal that the wrapper caught, changed the
working directory and resumed the process.
These days, the current working directory is passed from the wrapper
to the runtime through a special entry in the app metadata and the
SIGINT handshake is not necessary anymore.
Remove the signaling from the runtime and the exec harness.
Change-Id: Ia53bcc9e4724d2ca00207e22b91ce80a05271b55
Reviewed-on: https://go-review.googlesource.com/106096
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
internal/cpu,runtime: call cpu.initialize before alginit
runtime.alginit needs runtime/support_{aes,ssse3,sse41} feature flag
to init aeshash function but internal/cpu.init not be called yet.
This CL will call internal/cpu.initialize before runtime.alginit, so
that we can move all cpu features related code to internal/cpu.
Keith Randall [Mon, 9 Apr 2018 23:00:54 +0000 (16:00 -0700)]
runtime: use fixed TLS offsets on darwin/amd64 and darwin/386
Fixes #23617
Note that this CL does not affect darwin/arm and darwin/arm64,
still TBD what, if anything, needs to be done for those.
Change-Id: Ie1ee02a9f4d4d1fb9cd5dc432d900f926cc157db
Reviewed-on: https://go-review.googlesource.com/105975 Reviewed-by: Ian Lance Taylor <iant@golang.org>
Matthew Dempsky [Thu, 5 Apr 2018 19:48:28 +0000 (12:48 -0700)]
cmd/compile: sort method sets using package height
Also, when statically building itabs, compare *types.Sym instead of
name alone so that method sets with duplicate non-exported methods are
handled correctly.
Fixes #24693.
Change-Id: I2db8a3d6e80991a71fef5586a15134b6de116269
Reviewed-on: https://go-review.googlesource.com/105039
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
Previously, constant pointer-typed expressions could use either Mpint
or NilVal as their Val depending on their construction, but const.go
expects each type to have a single corresponding Val kind.
This CL changes pointer-typed expressions to exclusively use Mpint.
Fixes #21221.
Change-Id: I6ba36c9b11eb19a68306f0b296acb11a8c254c41
Reviewed-on: https://go-review.googlesource.com/105315
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
Matthew Dempsky [Mon, 9 Apr 2018 20:57:56 +0000 (13:57 -0700)]
cmd/compile: refactor symbol sorting logic
This used to be duplicated in methcmp and siglt, because Sig used its
own representation for Syms. Instead, just use Syms, and add a
(*Sym).Less method that both methcmp and siglt can use.
Also, prune some impossible cases purportedly related to blank
methods: the Go spec disallows blank methods in interface method sets,
and addmethod drops blank methods without actually recording them in
the type's method set.
Daniel Martí [Sat, 7 Apr 2018 15:24:52 +0000 (16:24 +0100)]
api: remove unnecessary lines from except.txt
When I added the text/template/parse lines, I thought that both removed
and added APIs should be listed here (i.e. both -pkg and +pkg lines).
However that was wrong, as one can see by reading cmd/api/goapi.go, or
seeing how removing the +pkg lines does not break the API test.
Michael Munday [Mon, 26 Mar 2018 20:18:27 +0000 (21:18 +0100)]
cmd/compile: optimize comparisons using load merging where available
Multi-byte comparison operations were used on amd64, arm64, i386
and s390x for comparisons with constant arrays, but only amd64 and
i386 for comparisons with string constants. This CL combines the
check for platform capability, since they have the same requirements,
and also enables both on ppc64le which also supports load merging.
Note that these optimizations currently use little endian byte order
which results in byte reversal instructions on s390x. This should
be fixed at some point.
Change-Id: Ie612d13359b50c77f4d7c6e73fea4a59fa11f322
Reviewed-on: https://go-review.googlesource.com/102558
Run-TryBot: Michael Munday <mike.munday@ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Keith Randall <khr@golang.org>
Daniel Martí [Sun, 8 Apr 2018 16:52:16 +0000 (17:52 +0100)]
doc: add a note about loading profile files
If one is somewhat new to the command line or shell, it might be
surprising that changes applied to a file like $HOME/.profile will
seemingly not take effect, even if new shells are started.
Add a note about how shells usually only load these when the user logs
into a machine, to minimize the amount of people stuck and confused by
this.
Fixes #24756.
Change-Id: Ic68d8c97933f3f080b151a107633ecad76a163a4
Reviewed-on: https://go-review.googlesource.com/105557 Reviewed-by: Agniva De Sarker <agniva.quicksilver@gmail.com> Reviewed-by: Bryan C. Mills <bcmills@google.com>
Matthew Dempsky [Tue, 27 Mar 2018 20:50:08 +0000 (13:50 -0700)]
cmd/compile: insert instrumentation during SSA building
Insert appropriate race/msan calls before each memory operation during
SSA construction.
This is conceptually simple, but subtle because we need to be careful
that inserted instrumentation calls don't clobber arguments that are
currently being prepared for a user function call.
reorder1 already handles introducing temporary variables for arguments
in some cases. This CL changes it to use them for all arguments when
instrumenting.
Also, we can't SSA struct types with more than one field while
instrumenting. Otherwise, concurrent uses of disjoint fields within an
SSA-able struct can introduce false races.
This is both somewhat better and somewhat worse than the old racewalk
instrumentation pass. We're now able to easily recognize cases like
constructing non-escaping closures on the stack or accessing closure
variables don't need instrumentation calls. On the other hand,
spilling escaping parameters to the heap now results in an
instrumentation call.
Overall, this CL results in a small net reduction in the number of
instrumentation calls, but a small net increase in binary size for
instrumented executables. cmd/go ends up with 5.6% fewer calls, but a
2.4% larger binary.
This change replaces the vendored socks client implementation with the
bundle of golang.org/x/net/internal/socks package which contains fixes
for 19354 and 11682.
Kir Kolyshkin [Tue, 6 Feb 2018 21:16:02 +0000 (13:16 -0800)]
os/user: add a way to enforce pure Go implementation
This provides a way to enforce pure Go implementation of os/user
lookup functions on UNIX platforms by means of "osusergo" build tag,
in a manner similar to netgo/netcgo tags in the net package.
If "osusergo" build tag is set, Go implementation is selected.
If "osusergo" build tag is NOT set, the old behavior is retained,
that is to use cgo (libc-backed) implementation if both cgo and such
and such implementation are available.
The reason behind this change is to make it possible to build proper
static binaries on Linux. The problem is, glibc implementation of
getpw*, getgrp* and getgrouplist functions relies on presense of
libnss*.so libraries during runtime, making it impossible to build
a self-contained static binary which uses both cgo and os/user.
In such case, linker warnings like this are shown:
> warning: Using 'getgrouplist' in statically linked applications
> requires at runtime the shared libraries from the glibc version
> used for linking
While this can be solved by recompiling glibc with --enable-static-nss
flag or using a different libc implementation (like musl on Alpine Linux),
it is not always practical or even possible.
Matthew Dempsky [Fri, 6 Apr 2018 05:42:16 +0000 (22:42 -0700)]
cmd/compile: fix method expressions with anonymous receivers
Method expressions with anonymous receiver types like "struct { T }.m"
require wrapper functions, which we weren't always creating. This in
turn resulted in linker errors.
This CL ensures that we generate wrapper functions for any anonymous
receiver types used in a method expression.
Brian Kessler [Thu, 30 Nov 2017 16:32:07 +0000 (09:32 -0700)]
math/big: clean up z.div(z, x, y) calls
Updates #22830
Due to not checking if the output slices alias in divLarge,
calls of the form z.div(z, x, y) caused the slice z
to attempt to be used to store both the quotient and the
remainder of the division. CL 78995 applies an alias
check to correct that error. This CL cleans up the
additional div calls that attempt to supply the same slice
to hold both the quotient and remainder.
Note that the call in expNN was responsible for the reported
error in r.Exp(x, 1, m) when r was initialized to a non-zero value.
The second instance in expNNMontgomery did not result in an error
due to the size of the arguments.
// RR = 2**(2*_W*len(m)) mod m
RR := nat(nil).setWord(1)
zz := nat(nil).shl(RR, uint(2*numWords*_W))
_, RR = RR.div(RR, zz, m)
Specifically,
cap(RR) == 5 after setWord(1) due to const e = 4 in z.make(1)
len(zz) == 2*len(m) + 1 after shifting left, numWords = len(m)
Reusing the backing array for z and z2 in div was only triggered if
cap(RR) >= len(zz) + 1 and len(m) > 1 so that divLarge was called.
But, 5 < 2*len(m) + 2 if len(m) > 1, so new arrays were allocated
and the error was never triggered in this case.
Change-Id: Iedac80dbbde13216c94659e84d28f6f4be3aaf24
Reviewed-on: https://go-review.googlesource.com/81055
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
Matthew Dempsky [Thu, 5 Apr 2018 01:42:39 +0000 (18:42 -0700)]
cmd/compile: cleanup method symbol creation
There were multiple ad hoc ways to create method symbols, with subtle
and confusing differences between them. This CL unifies them into a
single well-documented encoding and implementation.
This introduces some inconsequential changes to symbol format for the
sake of simplicity and consistency. Two notable changes:
1) Symbol construction is now insensitive to the package currently
being compiled. Previously, non-exported methods on anonymous types
received different method symbols depending on whether the method was
local or imported.
2) Symbols for method values parenthesized non-pointer receiver types
and non-exported method names, and also always package-qualified
non-exported method names. Now they use the same rules as normal
method symbols.
The methodSym function is also now stricter about rejecting
non-sensical method/receiver combinations. Notably, this means that
typecheckfunc needs to call addmethod to validate the method before
calling declare, which also means we no longer emit errors about
redeclaring bogus methods.
Change-Id: I9501c7a53dd70ef60e5c74603974e5ecc06e2003
Reviewed-on: https://go-review.googlesource.com/104876 Reviewed-by: Robert Griesemer <gri@golang.org>
adjustpointers loops over a bitmap.
If the length of that bitmap is zero,
we can skip making the call entirely.
This speeds up stack copying when there are
no pointers present in either args or locals.
Richard Musiol [Wed, 28 Mar 2018 22:53:26 +0000 (00:53 +0200)]
cmd/compile/internal/gc: factor out beginning of SSAGenState.Call
This commit does not change the semantics of the Call method. Its
purpose is to avoid duplication of code by making PrepareCall available
for separate use by the wasm backend.
Joel Sing [Thu, 5 Apr 2018 19:00:25 +0000 (05:00 +1000)]
runtime: fix/improve exitThread on openbsd
OpenBSD's __threxit syscall takes a pointer to a 32-bit value that will be
zeroed immediately before the thread exits. Make use of this instead of
zeroing freeWait from the exitThread assembly and using hacks like switching
to a static stack, so this works on 386.
Matthew Dempsky [Thu, 5 Apr 2018 04:49:49 +0000 (21:49 -0700)]
cmd/compile: drop legacy code for generating iface wrappers
Originally, scalar values were directly stored within interface values
as long as they fit into a pointer-sized slot of memory. And since
interface method calls always pass the full pointer-sized value as the
receiver argument, value-narrowing wrappers were necessary to adapt to
the calling convention for methods with smaller receiver types.
However, for precise garbage collection, we now only store actual
pointers within interface values, so these wrappers are no longer
necessary.
VEX constants were used when instructions were added by hand.
Now all VEX-encoded instructions are auto-generated by x86avxgen,
so there is no need for those anymore.
Ben Shi [Thu, 22 Mar 2018 02:18:50 +0000 (02:18 +0000)]
cmd/compile: optimize 386 binary operations with a memory operand
Some integer/float binary operations of 386 can take a direct memory
operand, which is more efficient than loading to a register.
These CL does this optimization by copying the similar solution
of amd64. And the go1 benchmark shows some inprovements, especially
the test case Template. (excluding noise)
Alberto Donizetti [Wed, 4 Apr 2018 12:35:05 +0000 (14:35 +0200)]
cmd/compile: stack-allocate worklist in ReachableBlocks
Stack-allocate a local worklist in the deadcode pass. A size of 64 for
the pre-allocation is enough for >99% of the ReachableBlocks call in
a typical package.
Matthew Dempsky [Wed, 4 Apr 2018 22:53:27 +0000 (15:53 -0700)]
cmd/compile: extract inline related fields into separate Inline type
Inl, Inldcl, and InlCost are only applicable to functions with bodies
that can be inlined, so pull them out into a separate Inline type to
make understanding them easier.
A side benefit is that we can check if a function can be inlined by
just checking if n.Func.Inl is non-nil, which simplifies handling of
empty function bodies.
While here, remove some unnecessary Curfn twiddling, and make imported
functions use Inl.Dcl instead of Func.Dcl for consistency for local
functions.
Passes toolstash-check.
Change-Id: Ifd4a80349d85d9e8e4484952b38ec4a63182e81f
Reviewed-on: https://go-review.googlesource.com/104756
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
David Chase [Sat, 3 Mar 2018 01:33:15 +0000 (20:33 -0500)]
cmd/compile: adjust is-statement on Pos's to improve debugging
Stores to auto tmp variables can be hoisted to places
where the line numbers make debugging look "jumpy".
Turning those instructions into ones with is_stmt = 0 in
the DWARF (accomplished by marking ssa nodes with NotStmt)
makes debugging look better while still attributing the
instructions with the correct line number.
The same is true for certain register allocator spills and
reloads.
Change-Id: I97a394eb522d4911cc40b4bf5bf76d3d7221f6c0
Reviewed-on: https://go-review.googlesource.com/98415
Run-TryBot: David Chase <drchase@google.com> Reviewed-by: Cherry Zhang <cherryyz@google.com> Reviewed-by: Keith Randall <khr@golang.org>
David Chase [Tue, 13 Feb 2018 22:39:38 +0000 (17:39 -0500)]
cmd/link: process is_stmt data into dwarf line tables
To improve debugging, instructions should be annotated with
DWARF is_stmt. The DWARF default before was is_stmt=1, and
to remove "jumpy" stepping the optimizer was tagging
instructions with a no-position position, which interferes
with the accuracy of profiling information. This allows
that to be corrected, and also allows more "jumpy" positions
to be annotated with is_stmt=0 (these changes were not made
for 1.10 because of worries about further messing up
profiling).
The is_stmt values are placed in a pc-encoded table and
passed through a symbol derived from the name of the
function and processed in the linker alongside its
processing of each function's pc/line tables.
The only change in binary size is in the .debug_line tables
measured with "objdump -h --section=.debug_line go1.test"
For go1.test, these are 2614 bytes larger,
or 0.72% of the size of .debug_line,
or 0.025% of the file size.
This will increase in proportion to how much the is_stmt
flag is used (toggled).
David Chase [Wed, 3 Jan 2018 22:14:55 +0000 (17:14 -0500)]
cmd/compile: add IsStmt breakpoint info to src.lico
Add IsStmt information to src.lico so that suitable lines
for breakpoints (or not) can be noted, eventually for
communication to the debugger via the linker and DWARF.
The expectation is that the front end will apply statement
boundary marks because it has best information about the
input, and the optimizer will attempt to preserve these.
The exact method for placing these marks is still TBD;
ideally stopping "at" line N in unoptimized code will occur
at a point where none of the side effects of N have occurred
and all of the inputs for line N can still be observed.
The optimizer will work with the same markings supplied
for unoptimized code.
It is a goal that non-optimizing compilation should conserve
statement marks.
The optimizer will also use the not-a-statement annotation
to indicate instructions that have a line number (for
profiling purposes) but should not be the target of
debugger step, next, or breakpoints. Because instructions
marked as statements are sometimes removed, a third value
indicating that a position (instruction) can serve as a
statement if the optimizer removes the current instruction
marked as a statement for the same line. The optimizer
should attempt to conserve statement marks, but it is not
a bug if some are lost.
Includes changes to html output for GOSSAFUNC to indicate
not-default is-a-statement with bold and not-a-statement
with strikethrough.
Robert Griesemer [Wed, 4 Apr 2018 00:05:47 +0000 (17:05 -0700)]
go/printer, gofmt: tuned table alignment for better results
The go/printer (and thus gofmt) uses a heuristic to determine
whether to break alignment between elements of an expression
list which is spread across multiple lines. The heuristic only
kicked in if the entry sizes (character length) was above a
certain threshold (20) and the ratio between the previous and
current entry size was above a certain value (4).
This heuristic worked reasonably most of the time, but also
led to unfortunate breaks in many cases where a single entry
was suddenly much smaller (or larger) then the previous one.
The behavior of gofmt was sufficiently mysterious in some of
these situations that many issues were filed against it.
The simplest solution to address this problem is to remove
the heuristic altogether and have a programmer introduce
empty lines to force different alignments if it improves
readability. The problem with that approach is that the
places where it really matters, very long tables with many
(hundreds, or more) entries, may be machine-generated and
not "post-processed" by a human (e.g., unicode/utf8/tables.go).
If a single one of those entries is overlong, the result
would be that the alignment would force all comments or
values in key:value pairs to be adjusted to that overlong
value, making the table hard to read (e.g., that entry may
not even be visible on screen and all other entries seem
spaced out too wide).
Instead, we opted for a slightly improved heuristic that
behaves much better for "normal", human-written code.
1) The threshold is increased from 20 to 40. This disables
the heuristic for many common cases yet even if the alignment
is not "ideal", 40 is not that many characters per line with
todays screens, making it very likely that the entire line
remains "visible" in an editor.
2) Changed the heuristic to not simply look at the size ratio
between current and previous line, but instead considering the
geometric mean of the sizes of the previous (aligned) lines.
This emphasizes the "overall picture" of the previous lines,
rather than a single one (which might be an outlier).
3) Changed the ratio from 4 to 2.5. Now that we ignore sizes
below 40, a ratio of 4 would mean that a new entry would have
to be 4 times bigger (160) or smaller (10) before alignment
would be broken. A ratio of 2.5 seems more sensible.
Applied updated gofmt to all of src and misc. Also tested
against several former issues that complained about this
and verified that the output for the given examples is
satisfactory (added respective test cases).
Some of the files changed because they were not gofmt-ed
in the first place.
For #644.
For #7335.
For #10392.
(and probably more related issues)