The implementation follows the basic pattern of an indirect
function call (genDynamicCall).
We use the same trick as SetFinalizer so that direct calls to
(r.V).Call, which are overwhelmingly the norm, are inlined.
Bug fix (and simplification): calling untag() to unbox a
reflect.Value is wrong for reflect.Values containing interfaces
(rare). Now, we call untag for concrete types and typeFilter
for interface types, and we can use this pattern in all cases.
It corresponds to the ssa.TypeAssert operator, so we call
it typeAssert. Added tests to cover this.
We also specialize reflect.{In,Out} when the operand is an int
literal.
+ Tests.
Also:
- make taggedValue() panic, not return nil, eliminating many checks.
We call isTaggedValue for the one place that cares.
- pointer_test: recover from panics in Analyze() and dump the log.
R=crawshaw
CC=golang-dev
https://golang.org/cl/14426050
reflect.Values may point to tagged objects with
interface type, e.g. x := reflect.ValueOf(new(interface{})).Elem().
We failed to consider this when implementing Elem.
Also, (reflect.Value).Interface() must do one "unboxing"
when it encounters such tagged objects.
i.e., x.Elem().Interface() and x.Interface() are equivalent
in that case.
Also:
- add example of tagged object with interface type.
- untabify (Label).String docstring.
- added tests.
R=crawshaw
CC=golang-dev
https://golang.org/cl/18020044
Support for:
(*reflect.rtype).Field
(*reflect.rtype).FieldByName
reflect.MakeSlice
runtime.SetFinalizer
Details:
- analysis locates ssa.Functions for (reflect.Value).Call
and runtime.SetFinalizer during startup to that it can
special-case them during genCall. ('Call' is forthcoming.)
- The callsite.targets mechanism is only used for dynamic
calls now. For static calls we call callEdge during constraint
generation; this is a minor optimisation.
- Static calls to SetFinalizer are inlined so that the call
appears to go direct to the finalizer. (We'll use the same
trick for (reflect.Value).Call.)
- runtime.FuncForPC: treat as a no-op.
- Fixed pointer_test to properly deal with expectations
that are multi-sets.
- Inlined rtypeMethodByNameConstraint.addMethod.
- More tests.
R=crawshaw
CC=golang-dev
https://golang.org/cl/14682045
Various reflect operations permit assignability conversions,
i.e. their internals behave unlike y=x.(T) which unpacks only
those interface values in x that are identical to T.
We split typeAssertConstraint y=x.(T) into two constraints:
1) typeFilter, for when T is an interface type and no
representation change occurs.
2) unpack, for when T is a concrete type and the payload of the
tagged object is extracted. This constraint has an 'exact'
parameter indicating whether to use the predicate
IsIdentical (for type assertions) or
IsAssignable (for reflect operators).
+ Tests.
R=crawshaw
CC=golang-dev
https://golang.org/cl/14547043
(reflect.Value).Bytes
(reflect.Value).Elem
(reflect.Value).Index
(reflect.Value).SetBytes
(reflect.Value).Slice
reflect.PtrTo
reflect.SliceOf
+ Tests.
Also: comment out an 'info-'level print statement in the test; it was distracting.
R=crawshaw
CC=golang-dev
https://golang.org/cl/14454055
This information can be used to specialize such calls, e.g.
- report location of unsound calls (done for reflect.NewAt)
- exploit argument information (done for constant 'dir' parameter to reflect.ChanOf)
+ tests.
R=crawshaw
CC=golang-dev
https://golang.org/cl/14517046
Since the Go runtime treats it specially, so must the pointer analysis.
Details:
- Combine object.{val,typ} fields into 'data interface{}'.
It may now hold a string, describing an instrinsically
allocated object such as the command-line args.
- extend Label accordingly; add Label.ReflectType() accessor.
Also: document pointer analysis algorithm classification.
R=crawshaw
CC=golang-dev
https://golang.org/cl/14156043
Motivation: simple constraints---copy and addr---are more
amenable to pre-solver optimizations (forthcoming) than
complex constraints: load, store, and all others.
In code such as the following:
t0 = new struct { x, y int }
t1 = &t0.y
t2 = *t1
there's no need for the full generality of a (complex)
load constraint for t2=*t1 since t1 can only point to t0.y.
All we need is a (simple) copy constraint t2 = (t0.y)
where (t0.y) is the object node label for that field.
For all "addressable" SSA instructions, we tabulate
whether their points-to set is necessarily a singleton. For
some (e.g. Alloc, MakeSlice, etc) this is always true by
design. For others (e.g. FieldAddr) it depends on their
operands.
We exploit this information when generating constraints:
all load-form and store-form constraints are reduced to copy
constraints if the pointer's PTS is a singleton.
Similarly all FieldAddr (y=&x.f) and IndexAddr (y=&x[0])
constraints are reduced to offset addition, for singleton
operands.
Here's the constraint mix when running on the oracle itself.
The total number of constraints is unchanged but the fraction
that are complex has gone down to 21% from 53%.
before after
--simple--
addr 20682 46949
copy 61454 91211
--complex--
offsetAddr 41621 15325
load 18769 12925
store 30758 6908
invoke 758 760
typeAssert 1688 1689
total 175832 175869
Also:
- Add Pointer.Context() for local variables,
since we now plumb cgnodes throughout. Nice.
- Refactor all load-form (load, receive, lookup) and
store-form (Store, send, MapUpdate) constraints to use
genLoad and genStore.
- Log counts of constraints by type.
- valNodes split into localval and globalval maps;
localval is purged after each function.
- analogous maps localobj[v] and globalobj[v] hold sole label
for pts(v), if singleton.
- fnObj map subsumed by globalobj.
- make{Function/Global/Constant} inlined into objectValue.
Much cleaner.
R=crawshaw
CC=golang-dev
https://golang.org/cl/13979043
(reflect.Value).Send
(reflect.Value).TrySend
(reflect.Value).Recv
(reflect.Value).TryRecv
(reflect.Type).ChanOf
(reflect.Type).In
(reflect.Type).Out
reflect.Indirect
reflect.MakeChan
Also:
- specialize genInvoke when the receiver is a reflect.Type under the
assumption that there's only one possible concrete type. This
makes all reflect.Type operations context-sensitive since the calls
are no longer dynamic.
- Rename all variables to match the actual parameter names used in
the reflect API.
- Add pointer.Config.Reflection flag
(exposed in oracle as --reflect, default false) to enable reflection.
It currently adds about 20% running time. I'll make it true after
the presolver is implemented.
- Simplified worklist datatype and solver main loop slightly
(~10% speed improvement).
- Use addLabel() utility to add a label to a PTS.
(Working on my 3 yr old 2x2GHz+4GB Mac vs 8x4GHz+24GB workstation,
one really notices the cost of pointer analysis.
Note to self: time to implement presolver.)
R=crawshaw
CC=golang-dev
https://golang.org/cl/13242062
Core:
reflect.TypeOf
reflect.ValueOf
reflect.Zero
reflect.Value.Interface
Maps:
(reflect.Value).MapIndex
(reflect.Value).MapKeys
(reflect.Value).SetMapIndex
(*reflect.rtype).Elem
(*reflect.rtype).Key
+ tests:
pointer/testdata/mapreflect.go.
oracle/testdata/src/main/reflection.go.
Interface objects (T, V...) have been renamed "tagged objects".
Abstraction: we model reflect.Value similar to
interface{}---as a pointer that points only to tagged
objects---but a reflect.Value may also point to an "indirect
tagged object", one in which the payload V is of type *T not T.
These are required because reflect.Values can hold lvalues,
e.g. when derived via Field() or Elem(), though we won't use
them till we get to structs and pointers.
Solving: each reflection intrinsic defines a new constraint
and resolution rule. Because of the nature of reflection,
generalizing across types, the resolution rules dynamically
create additional complex constraints during solving, where
previously only simple (copy) constraints were created.
This requires some solver changes:
The work done before the main solver loop (to attach new
constraints to the graph) is now done before each iteration,
in processNewConstraints.
Its loop over constraints is broken into two passes:
the first handles base (addr-of) constraints,
the second handles simple and complex constraints.
constraint.init() has been inlined. The only behaviour that
varies across constraints is ptr()
Sadly this will pessimize presolver optimisations, when we get
there; such is the price of reflection.
Objects: reflection intrinsics create objects (i.e. cause
memory allocations) with no SSA operation. We will represent
them as the cgnode of the instrinsic (e.g. reflect.New), so we
extend Labels and node.data to represent objects as a product
(not sum) of ssa.Value and cgnode and pull this out into its
own type, struct object. This simplifies a number of
invariants and saves space. The ntObject flag is now
represented by obj!=nil; the other flags are moved into
object.
cgnodes are now always recorded in objects/Labels for which it
is appropriate (all but those for globals, constants and the
shared contours for functions).
Also:
- Prepopulate the flattenMemo cache to consider reflect.Value
a fake pointer, not a struct.
- Improve accessors and documentation on type Label.
- @conctypes assertions renamed @types (since dyn. types needn't be concrete).
- add oracle 'describe' test on an interface (missing, an oversight).
R=crawshaw
CC=golang-dev
https://golang.org/cl/13418048
