Programs such as this cause the PtrTo solver to attempt to
enumerate an infinite set of types {T, *T, ..., *******T, etc}.
t := reflect.TypeOf(T{})
for {
t = reflect.PtrTo(t)
}
The fix is to bound the depth of reflectively created types at
about 4 map/chan/slice/pointer constructors.
+ test.
LGTM=gri
R=gri
CC=crawshaw, golang-codereviews
https://golang.org/cl/102030044
This change renumbers nodes so that addressable ones
(that may appear in a points-to set) all have lower
numbers than non-addressable ones----initially at least:
reflection, SetFinalizer, etc add new nodes during
solving.
This improves the efficiency of sparse PTS
representations (to be added later). The largest int in
a PTS is now about 20% of the previous max.
Overview:
- move constraint stuff into constraint.go.
- add two methods to constraint:
(1) renumber(): renumbers all nodeids. The
implementations are very repetitive but simple. I
thought hard about other ways (mixins, reflection)
but decided this one was fine.
(2) indirect(): report the set of nodeids whose
points-to relations depend on the solver, not just
the initial constraint graph.
(This method is currently unused and is logically
part of a forthcoming change to implement PE/LE
presolver optimizations. (Perhaps I should comment
it out/remove it for now.)
- split up the population of the intrinsics map by file.
- delete analysis.probes (unused field)
- remove state="..." from panic message; unnecessary.
LGTM=crawshaw
R=crawshaw
CC=golang-codereviews
https://golang.org/cl/73320043
Observation: not all alias facts are interesting.
- A channel-peers query also cares about pointers of kind chan.
- An oracle "points-to" query on an expression of kind map
only cares about maps.
- We always care about func, interface and reflect.Value,
since they're needed for sound analysis of dynamic dispatch.
We needn't bother collecting alias information for
uninteresting pointers, and this massively reduces the number
of labels flowing in to the constraint system.
The only constraints that create new labels are addressOf
and offsetAddr; both are now selectively emitted by type.
We compute the set of type kinds to track, based on the
{Indirect,}Query types. (We could enable tracking at an
even finer grain if we want.)
This requires that we can see all the {Indirect,}Query
value types a priori, which is not the case for the PrintCalls
mechanism used in the tests, so I have rewritten the latter
to use {Indirect,}Query instead.
This reduces the solver-phase time for the entire standard
library and tests from >8m to <2m. Similar speedups are
obtained on small and medium-sized programs.
Details:
- shouldTrack inspects the flattened form of a type to see if
it contains fields we must track. It memoizes the result.
- added precondition checks to (*Config).Add{,Indirect}Query.
- added (*ssa.Program).LookupMethod convenience method.
- added Example of how to use the Query mechanism.
- removed code made dead by a recent invariant:
the only pointerlike Const value is nil.
- don't generate constraints for any functions in "reflect".
(we had forgotten to skip synthetic wrappers too).
- write PTA warnings to the log.
- add annotations for more intrinsics.
LGTM=gri, crawshaw
R=crawshaw, gri
CC=golang-codereviews
https://golang.org/cl/62540043
Method-set caching is now performed externally using a MethodSetCache (if desired), not by the Types themselves.
This a minor deoptimization due to the extra maps, but avoids a situation in which method-sets are computed and frozen prematurely. (See b/7114)
LGTM=gri
R=gri
CC=golang-codereviews
https://golang.org/cl/61430045
Alan Donovan
Robert Griesemer