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
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
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
these guys really really want long to be 32-bits,
so ,s/long/int32/ (and then manual fixup).
still passes all tests.
(i started out looking for just those longs that
needed to be int32 instead, and it was just too hard
to track them down one by one.)
the longs were rare enough that i don't think
it will cause integration problems.
R=ken
OCL=13787
CL=13789
