The name linkwriteobj is misleading because it implies that
the function has something to do with the linker, which it
does not. The name is historical: the function performs an
operation that was previously performed by the linker, but no
longer is.
LGTM=rsc
R=rsc, minux.ma
CC=golang-codereviews
https://golang.org/cl/88210045
If we compile a generated file stored in a temporary
directory - let's say /tmp/12345/work/x.c - then by default
6c stores the full path and then the pcln table in the
final binary includes the full path. This makes repeated builds
(using different temporary directories) produce different
binaries, even if the inputs are the same.
In the old 'go tool pack', the P flag specified a prefix to remove
from all stored paths (if present), and cmd/go invoked
'go tool pack grcP $WORK' to remove references to the
temporary work directory.
We've changed the build to avoid pack as much as possible,
under the theory that instead of making pack convert from
.6 to .a, the tools should just write the .a directly and save a
round of I/O.
Instead of going back to invoking pack always, define a common
flag -trimpath in the assemblers, C compilers, and Go compilers,
implemented in liblink, and arrange for cmd/go to use the flag.
Then the object files being written out have the shortened paths
from the start.
While we are here, reimplement pcln support for GOROOT_FINAL.
A build in /tmp/go uses GOROOT=/tmp/go, but if GOROOT_FINAL=/usr/local/go
is set, then a source file named /tmp/go/x.go is recorded instead as
/usr/local/go/x.go. We use this so that we can prepare distributions
to be installed in /usr/local/go without actually working in that
directory. The conversion to liblink deleted all the old file name
handling code, including the GOROOT_FINAL translation.
Bring the GOROOT_FINAL translation back.
Before this CL, using GOROOT_FINAL=/goroot make.bash:
g% strings $(which go) | grep -c $TMPDIR
6
g% strings $(which go) | grep -c $GOROOT
793
g%
After this CL:
g% strings $(which go) | grep -c $TMPDIR
0
g% strings $(which go) | grep -c $GOROOT
0
g%
(The references to $TMPDIR tend to be cgo-generated source files.)
Adding the -trimpath flag to the assemblers required converting
them to the new Go-semantics flag parser. The text in go1.3.html
is copied and adjusted from go1.1.html, which is when we applied
that conversion to the compilers and linkers.
Fixes#6989.
LGTM=iant
R=r, iant
CC=golang-codereviews
https://golang.org/cl/88300045
When I did the original 386 ports on Linux and OS X, I chose to
define GS-relative expressions like 4(GS) as relative to the actual
thread-local storage base, which was usually GS but might not be
(it might be FS, or it might be a different constant offset from GS or FS).
The original scope was limited but since then the rewrites have
gotten out of control. Sometimes GS is rewritten, sometimes FS.
Some ports do other rewrites to enable shared libraries and
other linking. At no point in the code is it clear whether you are
looking at the real GS/FS or some synthesized thing that will be
rewritten. The code manipulating all these is duplicated in many
places.
The first step to fixing issue 7719 is to make the code intelligible
again.
This CL adds an explicit TLS pseudo-register to the 386 and amd64.
As a register, TLS refers to the thread-local storage base, and it
can only be loaded into another register:
MOVQ TLS, AX
An offset from the thread-local storage base is written off(reg)(TLS*1).
Semantically it is off(reg), but the (TLS*1) annotation marks this as
indexing from the loaded TLS base. This emits a relocation so that
if the linker needs to adjust the offset, it can. For example:
MOVQ TLS, AX
MOVQ 8(AX)(TLS*1), CX // load m into CX
On systems that support direct access to the TLS memory, this
pair of instructions can be reduced to a direct TLS memory reference:
MOVQ 8(TLS), CX // load m into CX
The 2-instruction and 1-instruction forms correspond roughly to
ELF TLS initial exec mode and ELF TLS local exec mode, respectively.
Liblink applies this rewrite on systems that support the 1-instruction form.
The decision is made using only the operating system (and probably
the -shared flag, eventually), not the link mode. If some link modes
on a particular operating system require the 2-instruction form,
then all builds for that operating system will use the 2-instruction
form, so that the link mode decision can be delayed to link time.
Obviously it is late to be making changes like this, but I despair
of correcting issue 7719 and issue 7164 without it. To make sure
I am not changing existing behavior, I built a "hello world" program
for every GOOS/GOARCH combination we have and then worked
to make sure that the rewrite generates exactly the same binaries,
byte for byte. There are a handful of TODOs in the code marking
kludges to get the byte-for-byte property, but at least now I can
explain exactly how each binary is handled.
The targets I tested this way are:
darwin-386
darwin-amd64
dragonfly-386
dragonfly-amd64
freebsd-386
freebsd-amd64
freebsd-arm
linux-386
linux-amd64
linux-arm
nacl-386
nacl-amd64p32
netbsd-386
netbsd-amd64
openbsd-386
openbsd-amd64
plan9-386
plan9-amd64
solaris-amd64
windows-386
windows-amd64
There were four exceptions to the byte-for-byte goal:
windows-386 and windows-amd64 have a time stamp
at bytes 137 and 138 of the header.
darwin-386 and plan9-386 have five or six modified
bytes in the middle of the Go symbol table, caused by
editing comments in runtime/sys_{darwin,plan9}_386.s.
Fixes#7164.
LGTM=iant
R=iant, aram, minux.ma, dave
CC=golang-codereviews
https://golang.org/cl/87920043
Replaces CL 70000043.
Switch to the amd64p32 linker model if we are building under nacl/amd64p32.
No need to introduce linkarchinit() as 6a contains its own main() function.
LGTM=rsc
R=rsc, minux.ma
CC=golang-codereviews
https://golang.org/cl/72020043
From the original description in CL 15770043
The main change here is to consult $GOARCH.
In 6c, when GOOS=nacl, some of the more complex addressing modes must be disabled, and the BP and R15 registers must not be used.
See golang.org/s/go13nacl for design overview.
LGTM=rsc
R=golang-codereviews, gobot, rsc
CC=golang-codereviews
https://golang.org/cl/69020044
We now use the %A, %D, %P, and %R routines from liblink
across the board.
Fixes#7178.
Fixes#7055.
LGTM=iant
R=golang-codereviews, gobot, rsc, dave, iant, remyoudompheng
CC=golang-codereviews
https://golang.org/cl/49170043
- add buffered stdout to all tools and provide to link ctxt.
- avoid extra \n before ! in .6 files written by assemblers
(makes them match the C compilers).
- use linkwriteobj instead of linkouthist+linkwritefuncs.
- in assemblers and C compilers, record pc explicitly in Prog,
for use by liblink.
- in C compilers, preserve jump target links.
- in Go compilers (gsubr.c) attach gotype directly to
corresponding LSym* instead of rederiving from instruction stream.
- in Go compilers, emit just one definition for runtime.zerovalue
from each compilation.
This CL consists entirely of small adjustments.
The heavy lifting is in CL 39680043.
Each depends on the other.
R=golang-dev, dave, iant
CC=golang-dev
https://golang.org/cl/37030045
When I renamed LAddr back to Addr (before sending the
original linker CLs), I missed the .y files in my global substitute.
Since the .y files are only processed when running make in
one of those directories (not during all.bash), they were
behind the generated files.
R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/40770044
Preparation for golang.org/s/go13linker work.
This CL does not build by itself. It depends on 35740044
and 35790044 and will be submitted at the same time.
R=iant
CC=golang-dev
https://golang.org/cl/35830043
Also introduce BGET2/4, BPUT2/4 as they are widely used.
Slightly improve BGETC/BPUTC implementation.
This gives ~5% CPU time improvement on go install -a -p1 std.
Before:
real user sys
0m23.561s 0m16.625s 0m5.848s
0m23.766s 0m16.624s 0m5.846s
0m23.742s 0m16.621s 0m5.868s
after:
0m22.999s 0m15.841s 0m5.889s
0m22.845s 0m15.808s 0m5.850s
0m22.889s 0m15.832s 0m5.848s
R=golang-dev, r
CC=golang-dev
https://golang.org/cl/12745047
This CL is an aggregate of 10271047, 10499043, 9733044. Descriptions of each follow:
10499043
runtime,cmd/ld: Merge TLS symbols and teach 5l about ARM TLS
This CL prepares for external linking support to ARM.
The pseudo-symbols runtime.g and runtime.m are merged into a single
runtime.tlsgm symbol. When external linking, the offset of a thread local
variable is stored at a memory location instead of being embedded into a offset
of a ldr instruction. With a single runtime.tlsgm symbol for both g and m, only
one such offset is needed.
The larger part of this CL moves TLS code from gcc compiled to internally
compiled. The TLS code now uses the modern MRC instruction, and 5l is taught
about TLS fallbacks in case the instruction is not available or appropriate.
10271047
This CL adds support for -linkmode external to 5l.
For 5l itself, use addrel to allow for D_CALL relocations to be handled by the
host linker. Of the cases listed in rsc's comment in issue 4069, only case 5 and
63 needed an update. One of the TODO: addrel cases was since replaced, and the
rest of the cases are either covered by indirection through addpool (cases with
LTO or LFROM flags) or stubs (case 74). The addpool cases are covered because
addpool emits AWORD instructions, which in turn are handled by case 11.
In the runtime, change the argv argument in the rt0* functions slightly to be a
pointer to the argv list, instead of relying on a particular location of argv.
9733044
The -shared flag to 6l outputs a shared library, implemented in Go
and callable from non-Go programs such as C.
The main part of this CL change the thread local storage model.
Go uses the fastest and least general mode, local exec. TLS data in shared
libraries normally requires at least the local dynamic mode, however, this CL
instead opts for using the initial exec mode. Initial exec mode is faster than
local dynamic mode and can be used in linux since the linker has reserved a
limited amount of TLS space for performance sensitive TLS code.
Initial exec mode requires an extra load from the GOT table to determine the
TLS offset. This penalty will not be paid if ld is not in -shared mode, since
TLS accesses will be reduced to local exec.
The elf sections .init_array and .rela.init_array are added to register the Go
runtime entry with cgo at library load time.
The "hidden" attribute is added to Cgo functions called from Go, since Go
does not generate call through the GOT table, and adding non-GOT relocations for
a global function is not supported by gcc. Cgo symbols don't need to be global
and avoiding the GOT table is also faster.
The changes to 8l are only removes code relevant to the old -shared mode where
internal linking was used.
This CL only address the low level linker work. It can be submitted by itself,
but to be useful, the runtime changes in CL 9738047 is also needed.
Design discussion at
https://groups.google.com/forum/?fromgroups#!topic/golang-nuts/zmjXkGrEx6QFixes#5590.
R=rsc
CC=golang-dev
https://golang.org/cl/12871044
whose argument size is unknown (C vararg functions, and
assembly code without an explicit specification).
We used to use 0 to mean "unknown" and 1 to mean "zero".
Now we use ArgsSizeUnknown (0x80000000) to mean "unknown".
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/11590043
Also:
- faster code for example extraction
- simplify handling of command documentation:
all "main" packages are treated as commands
- various minor cleanups along the way
For commands written in Go, any doc.go file containing
documentation must now be part of package main (rather
then package documentation), otherwise the documentation
won't show up in godoc (it will still build, though).
For commands written in C, documentation may still be
in doc.go files defining package documentation, but the
recommended way is to explicitly ignore those files with
a +build ignore constraint to define package main.
Fixes#4806.
R=adg, rsc, dave, bradfitz
CC=golang-dev
https://golang.org/cl/7333046
Reference the 80386 compiler documentation now that the
documentation for the 68020 is offline.
R=golang-dev, minux.ma, rsc
CC=golang-dev
https://golang.org/cl/7127053
This is an experiment in static analysis of Go programs
to understand which struct fields a program might use.
It is not part of the Go language specification, it must
be enabled explicitly when building the toolchain,
and it may be removed at any time.
After building the toolchain with GOEXPERIMENT=fieldtrack,
a specific field can be marked for tracking by including
`go:"track"` in the field tag:
package pkg
type T struct {
F int `go:"track"`
G int // untracked
}
To simplify usage, only named struct types can have
tracked fields, and only exported fields can be tracked.
The implementation works by making each function begin
with a sequence of no-op USEFIELD instructions declaring
which tracked fields are accessed by a specific function.
After the linker's dead code elimination removes unused
functions, the fields referred to by the remaining
USEFIELD instructions are the ones reported as used by
the binary.
The -k option to the linker specifies the fully qualified
symbol name (such as my/pkg.list) of a string variable that
should be initialized with the field tracking information
for the program. The field tracking string is a sequence
of lines, each terminated by a \n and describing a single
tracked field referred to by the program. Each line is made
up of one or more tab-separated fields. The first field is
the name of the tracked field, fully qualified, as in
"my/pkg.T.F". Subsequent fields give a shortest path of
reverse references from that field to a global variable or
function, corresponding to one way in which the program
might reach that field.
A common source of false positives in field tracking is
types with large method sets, because a reference to the
type descriptor carries with it references to all methods.
To address this problem, the CL also introduces a comment
annotation
//go:nointerface
that marks an upcoming method declaration as unavailable
for use in satisfying interfaces, both statically and
dynamically. Such a method is also invisible to package
reflect.
Again, all of this is disabled by default. It only turns on
if you have GOEXPERIMENT=fieldtrack set during make.bash.
R=iant, ken
CC=golang-dev
https://golang.org/cl/6749064
This CL adds support for the these 7 new instructions to 6a/6l in
preparation of the upcoming CL for AES-NI accelerated crypto/aes:
AESENC, AESENCLAST, AESDEC, AESDECLAST, AESIMC, AESKEYGENASSIST,
and PSHUFD.
R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5970055
On 6l and 8l, this is a real instruction, guaranteed to
cause an 'undefined instruction' exception.
On 5l, we simulate it as BL to address 0.
The plan is to use it as a signal to the linker that this
point in the instruction stream cannot be reached
(hence the changes to nofollow). This will help the
compiler explain that panicindex and friends do not
return without having to put a list of these functions
in the linker.
R=ken2
CC=golang-dev
https://golang.org/cl/6255064
The old code generated for a bounds check was
CMP
JLT ok
CALL panicindex
ok:
...
The new code is (once the linker finishes with it):
CMP
JGE panic
...
panic:
CALL panicindex
which moves the calls out of line, putting more useful
code in each cache line. This matters especially in tight
loops, such as in Fannkuch. The benefit is more modest
elsewhere, but real.
From test/bench/go1, amd64:
benchmark old ns/op new ns/op delta
BenchmarkBinaryTree17 6096092000 6088808000 -0.12%
BenchmarkFannkuch11 6151404000 4020463000 -34.64%
BenchmarkGobDecode 28990050 28894630 -0.33%
BenchmarkGobEncode 12406310 12136730 -2.17%
BenchmarkGzip 179923 179903 -0.01%
BenchmarkGunzip 11219 11130 -0.79%
BenchmarkJSONEncode 86429350 86515900 +0.10%
BenchmarkJSONDecode 334593800 315728400 -5.64%
BenchmarkRevcomp25M 1219763000 1180767000 -3.20%
BenchmarkTemplate 492947600 483646800 -1.89%
And 386:
benchmark old ns/op new ns/op delta
BenchmarkBinaryTree17 6354902000 6243000000 -1.76%
BenchmarkFannkuch11 8043769000 7326965000 -8.91%
BenchmarkGobDecode 19010800 18941230 -0.37%
BenchmarkGobEncode 14077500 13792460 -2.02%
BenchmarkGzip 194087 193619 -0.24%
BenchmarkGunzip 12495 12457 -0.30%
BenchmarkJSONEncode 125636400 125451400 -0.15%
BenchmarkJSONDecode 696648600 685032800 -1.67%
BenchmarkRevcomp25M 2058088000 2052545000 -0.27%
BenchmarkTemplate 602140000 589876800 -2.04%
To implement this, two new instruction forms:
JLT target // same as always
JLT $0, target // branch expected not taken
JLT $1, target // branch expected taken
The linker could also emit the prediction prefixes, but it
does not: expected taken branches are reversed so that the
expected case is not taken (as in example above), and
the default expectaton for such a jump is not taken
already.
R=golang-dev, gri, r, dave
CC=golang-dev
https://golang.org/cl/6248049
Although Intel considers the three-argument form of IMUL to be a
variant of IMUL, I couldn't make 6l able to differentiate it without
huge changes, so I called it IMUL3.
R=rsc
CC=golang-dev
https://golang.org/cl/5686055
As a convenience to people working on the tools,
leave Makefiles that invoke the go dist tool appropriately.
They are not used during the build.
R=golang-dev, bradfitz, n13m3y3r, gustavo
CC=golang-dev
https://golang.org/cl/5636050
Also delete gotest, since it's messy to fix and slated for deletion anyway.
A couple of things outside src can't be tested any more. "go test" will be
fixed and these tests will be re-enabled. They're noisy for now.
Fixes#284.
R=rsc
CC=golang-dev
https://golang.org/cl/5598049
Uses of $INCLUDE and $NPROC are left over from Plan 9.
Remove them to avoid causing confusion.
R=golang-dev, r2
CC=golang-dev
https://golang.org/cl/4445079
The object files begin with a header that is
$GOARCH
on a line by itself. This CL changes that header to
go object $GOOS $GOARCH release.2011-01-01 4567+
where the final two fields are the most recent release
tag and the current hg version number.
All objects imported into a Go compilation or linked into an
executable must have the same header line, and that header
line must match the compiler and linker versions.
The effect of this will be that if you update and run all.bash
and then try to link in objects compiled with an earlier version
of the compiler (or invoke the wrong version of the compiler),
you will get an error showing the different headers instead
of perhaps silent incompatibility.
Normal usage with all.bash should be unaffected, because
all.bash deletes all the object files in $GOROOT/pkg/$GOOS_$GOARCH
and cleans all intermediate object files before starting.
This change is intended to diagnose stale objects arising when
users maintaining alternate installation directories forget to
rebuild some of their files after updating.
It should help make the adoption of $GOPATH (CL 3780043)
less error-prone.
R=ken2, r
CC=golang-dev
https://golang.org/cl/4023063
Returns R14 and R15 to the available register pool.
Plays more nicely with ELF ABI C code.
In particular, our signal handlers will no longer crash
when a signal arrives during execution of a cgo C call.
Fixes#720.
R=ken2, r
CC=golang-dev
https://golang.org/cl/1847051
