A function such as this:
func one() (x int) {
defer func() { recover() }()
x = 1
panic("return")
}
that combines named return parameters (NRPs) with deferred calls
that call recover, may return non-zero values despite the
fact it doesn't even contain a return statement. (!)
This requires a change to the SSA API: all functions'
control-flow graphs now have a second entry point, called
Recover, which is the block at which control flow resumes
after a recovered panic. The Recover block simply loads the
NRPs and returns them.
As an optimization, most functions don't need a Recover block,
so it is omitted. In fact it is only needed for functions that
have NRPs and defer a call to another function that _may_ call
recover.
Dataflow analysis of SSA now requires extra work, since every
may-panic instruction has an implicit control-flow edge to
the Recover block. The only dataflow analysis so far implemented
is SSA renaming, for which we make the following simplifying
assumption: the Recover block only loads the NRPs and returns.
This means we don't really need to analyze it, we can just
skip the "lifting" of such NRPs. We also special-case the Recover
block in the dominance computation.
Rejected alternative approaches:
- Specifying a Recover block for every defer instruction (like a
traditional exception handler).
This seemed like excessive generality, since Go programs
only need the same degenerate form of Recover block.
- Adding an instruction to set the Recover block immediately
after the named return values are set up, so that dominance
can be computed without special-casing.
This didn't seem worth the effort.
Interpreter:
- This CL completely reimplements the panic/recover/
defer logic in the interpreter. It's clearer and simpler
and closer to the model in the spec.
- Some runtime panic messages have been changed to be closer
to gc's, since tests depend on it.
- The interpreter now requires that the runtime.runtimeError
type be part of the SSA program. This requires that clients
import this package prior to invoking the interpreter.
This in turn requires (Importer).ImportPackage(path string),
which this CL adds.
- All $GOROOT/test/recover{,1,2,3}.go tests are now passing.
NB, the bug described in coverage.go (defer/recover in a concatenated
init function) remains. Will be fixed in a follow-up.
Fixesgolang/go#6381
R=gri
CC=crawshaw, golang-dev
https://golang.org/cl/13844043
Revision 8f2c714c6d97 made the 'imports' map per-typechecker,
not per package, breaking an assumption of doImport0. This
API needs a rethink for a number of reasons, some of which are
noted in this CL.
R=gri
CC=golang-dev
https://golang.org/cl/14606044
This requires us to make a copy of (not clobber) the supplied
config, and retain their Import hook separately so that it can
be wrapped by Importer.doImport.
Fixes bug 6562.
R=gri
CC=golang-dev
https://golang.org/cl/14523054
The new method is functionally identical to typeCheck, and
obviates the LoadMainPackage method.
Updated all clients.
Fixes bug 6561.
R=gri
CC=golang-dev
https://golang.org/cl/14494051
+ test.
Also:
- provide non-nil map to Importer.doImport0() to avoid a crash.
- reorganize oracle "needs" bits.
- reduce "needs" of 'freevars' and 'implements' queries by avoiding
ssa.Packages when types.Package suffices.
R=crawshaw
CC=golang-dev
https://golang.org/cl/13421046
Motivation: pointer analysis tools (like the oracle) want the
user to specify a set of initial packages, like 'go test'.
This change enables the user to specify a set of packages on
the command line using importer.LoadInitialPackages(args).
Each argument is interpreted as either:
- a comma-separated list of *.go source files together
comprising one non-importable ad-hoc package.
e.g. "src/pkg/net/http/triv.go" gives us [main].
- an import path, denoting both the imported package
and its non-importable external test package, if any.
e.g. "fmt" gives us [fmt, fmt_test].
Current type-checker limitations mean that only the first
import path may contribute tests: multiple packages augmented
by *_test.go files could create import cycles, which 'go test'
avoids by building a separate executable for each one.
That approach is less attractive for static analysis.
Details: (many files touched, but importer.go is the crux)
importer:
- PackageInfo.Importable boolean indicates whether
package is importable.
- un-expose Importer.Packages; expose AllPackages() instead.
- CreatePackageFromArgs has become LoadInitialPackages.
- imports() moved to util.go, renamed importsOf().
- InitialPackagesUsage usage message exported to clients.
- the package name for ad-hoc packages now comes from the
'package' decl, not "main".
ssa.Program:
- added CreatePackages() method
- PackagesByPath un-exposed, renamed 'imported'.
- expose AllPackages and ImportedPackage accessors.
oracle:
- describe: explain and workaround a go/types bug.
Misc:
- Removed various unnecessary error.Error() calls in Printf args.
R=crawshaw
CC=golang-dev
https://golang.org/cl/13579043
Now we actually prefetch all n packages, instead of
prefetching the last one n times. This yields a further 22%
improvement, which is more like what I was hoping for.
It makes me so sad that Go reproduced one of the best-known
mistakes of JavaScript. D'oh!
R=crawshaw
CC=golang-dev
https://golang.org/cl/13379046
1. ParseFiles (in util.go) parses each file in its own goroutine.
2. (*Importer).LoadPackage asynchronously prefetches the
import graph by scanning the imports of each loaded package
and calling LoadPackage on each one.
LoadPackage is now thread-safe and idempotent: it uses a
condition variable per package; the first goroutine to
request a package becomes responsible for loading it and
broadcasts to the others (waiting) when it becomes ready.
ssadump runs 34% faster when loading the oracle.
Also, refactorings:
- delete SourceLoader mechanism; just expose go/build.Context directly.
- CreateSourcePackage now also returns an error directly,
rather than via PackageInfo.Err, since every client wants that.
R=crawshaw
CC=golang-dev
https://golang.org/cl/13509045
stdlib_test runs the builder (in sanity-checking mode) over
the Go standard library. It also prints some stats about
the time and memory usage.
Also:
- importer.LoadPackage too (not just doImport) must consult
the cache to avoid creating duplicate Package instances for
the same import path when called serially from a test.
- importer: skip empty directories without an error.
- importer: print all errors, not just the first.
- visit.go: added AllFunctions utility for enumerating all
Functions in a Program.
- ssa.MethodSet is not safe to expose from the package since
it must be accessed under an (inaccessible) lock. (!!!)
This CL makes it unexported and restricts its use to the
single function Program.LookupMethod().
- Program.MethodSet() has gone.
Clients should instead iterate over the types.MethodSet
and call LookupMethod.
- Package.DumpTo(): improved efficiency of methodset printing
(by not creating wrappers) and accuracy (by showing * on
receiver type only when necessary).
- Program.CreatePackage: documented precondition and added
assertion.
R=gri
CC=golang-dev
https://golang.org/cl/12058048
ssa:
- Prog.CreatePackages inlined into all callers.
- Prog.CreatePackage is now exposed; idempotent; and checks for errors.
- '*address' not 'address' now implements lvalue (since it's 6 words).
- removed types.Method case from createMemberFromObject.
importer:
- added importer.PackageInfo.String method.
- simplifed importer.PackageInfo by putting types.Info in it.
- removed obsolete precondition from IsType.
R=gri
CC=golang-dev
https://golang.org/cl/11408045
Allmost all uses of go/types that wanted the type
information computed, installed callback functions
that stored the information in maps. Most of the
time this is the only thing that could be done because
there is no guarantee that types are completely set
up before the end of type-checking.
This CL removes the respective Context callbacks in favor
of corresponding maps that collect the desired information
on demand, grouped together in an optional Info struct.
R=adonovan
CC=golang-dev
https://golang.org/cl/11530044
PLEASE NOTE: the APIs for both "importer" and "ssa" packages
will continue to evolve and both need some polishing; the key
thing is that this CL splits them.
The go.types/importer package contains contains the Importer,
which takes care of the mechanics of loading a set of packages
and type-checking them. It exposes for each package a
PackageInfo containing:
- the package's ASTs (i.e. the input to the typechecker)
- the types.Package object
- the memoization of the typechecker callbacks for identifier
resolution, constant folding and expression type inference.
Method-set computation (and hence bridge-method creation) is
now moved to after creation of all packages: since they are no
longer created in topological order, we can't guarantee the
needed delegate methods exist yet.
ssa.Package no longer has public TypeOf, ObjectOf, ValueOf methods.
The private counterparts are valid only during the build phase.
Also:
- added to go/types an informative error (not crash) for an
importer() returning nil without error.
- removed Package.Name(), barely needed.
- changed Package.String() slightly.
- flag what looks like a bug in makeBridgeMethod. Will follow up.
R=golang-dev, gri
CC=golang-dev
https://golang.org/cl/9898043
