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
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
