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
Until now, the name of the captured ssa.Value, not
types.Var was used, leading to confusing disassembly
when it was a numbered register. See:
https://code.google.com/p/go/issues/detail?id=6337
Now the output is:
# Free variables:
# 0: a *int
# 1: b *int
func func@6.9() int:
.0.entry:
t0 = *b
t1 = *a
t2 = *b
etc...
BUG=6337
R=crawshaw
CC=golang-dev
https://golang.org/cl/13249049
Fix bug: the Signature for an interface method wrapper
erroneously had a non-nil receiver.
Function:
- Set Pkg field non-nil even for wrappers.
It is equal to that of the wrapped function.
Only wrappers of error.Error
(and its embeddings in other interfaces) may have nil.
Sanity checker now asserts this.
- FullName() now uses .Synthetic field to discriminate
synthetic methods, not Pkg==nil.
- Fullname() uses new relType() utility to print receiver type
name unqualified if it belongs to the same package.
(Alloc.String also uses relType utility.)
CallCommon:
- Description(): fix switch logic broken when we
eliminated the Recv field.
- better docs.
R=david.crawshaw, crawshaw, gri
CC=golang-dev
https://golang.org/cl/13057043
Remove its 'name' field and treat it just like any other
ssa.Register: it gets a temp name like "t1".
Instead, give it a comment field holding its purpose, e.g, "x"
for a source-level vare, or "new", "slicelit", "complit" or
"varargs".
This improves usability of tools whose UI needs to refer to a
particular allocation site.
R=gri
CC=golang-dev
https://golang.org/cl/12273043
CanonicalPos was inadequate since many pairs of instruction share the same pos (e.g. Allocs and Phis). Instead, we generalize the DebugRef instruction to associate not just Idents but Exprs with ssa.Values.
We no longer store any DebugRefs for constant expressions, to save space. (The type and value of such expressions can be obtained by other means, at a cost in complexity.)
Function.ValueForExpr queries the DebugRef info to return the ssa.Value of a given Expr.
Added tests.
Also:
- the DebugInfo flag is now per package, not global.
It must be set between Create and Build phases if desired.
- {Value,Instruction}.Pos() documentation updated: we still maintain
this information in the instruction stream even in non-debug mode,
but we make fewer claims about its invariants.
- Go and Defer instructions can now use their respective go/defer
token positions (not the call's lparen), so they do.
- SelectState:
Posn token.Pos indicates the <- position
DebugNode ast.Expr is the send stmt or receive expr.
- In building SelectStmt, we introduce extra temporaries in debug
mode to hold the result of the receive in 'case <-ch' even though
this value isn't ordinarily needed.
- Use *SelectState (indirectly) since the struct is getting bigger.
- Document some missing instructions in doc.go.
R=gri
CC=golang-dev
https://golang.org/cl/12147043
We now use LookupFieldOrMethod for all SelectorExprs, and
simplify the logic to discriminate the various cases.
We inline static calls to promoted/indirected functions,
dramatically reducing the number of functions created.
More tests are needed, but I'd like to submit this as-is.
In this CL, we:
- rely less on Id strings. Internally we now use
*types.Method (and its components) almost everywhere.
- stop thinking of types.Methods as objects. They don't
have stable identities. (Hopefully they will become
plain-old structs soon.)
- eliminate receiver indirection wrappers:
indirection and promotion are handled together by makeWrapper.
- Handle the interactions of promotion, indirection and
abstract methods much more cleanly.
- support receiver-bound interface method closures.
- break up builder.selectField so we can re-use parts
(emitFieldSelection).
- add importer.PackageInfo.classifySelector utility.
- delete interfaceMethodIndex()
- delete namedTypeMethodIndex()
- delete isSuperInterface() (replaced by types.IsAssignable)
- call memberFromObject on each declared concrete method's
*types.Func, not on every Method frem each method set, in the
CREATE phase for packages loaded by gcimporter.
go/types:
- document Func, Signature.Recv() better.
- use fmt in {Package,Label}.String
- reimplement Func.String to be prettier and to include method
receivers.
API changes:
- Function.method now holds the types.Method (soon to be
not-an-object) for synthetic wrappers.
- CallCommon.Method now contains an abstract (interface)
method object; was an abstract method index.
- CallCommon.MethodId() gone.
- Program.LookupMethod now takes a *Method not an Id string.
R=gri
CC=golang-dev
https://golang.org/cl/11674043
- removed a number of obsolete TODO(gri) comments.
- bring ssa.DefaultType back into sync with types.defaultType.
- re-enable types.Package.Path()!="" assertion.
- use Path() (not reflect pointer) in sort routine.
- make interp.checkInterface use types.MissingMethod.
- un-export ssa.MakeId function.
- inline pointer() into all callers, and delete.
- enable two more interp_tests: $GOROOT/test/{method3,cmp}.go
- add links to bugs to other interp_tests.
- add runtime.NumCPU to ssa/interp/externals.go
R=gri
CC=golang-dev
https://golang.org/cl/11353043
This CL adds three new functions to determine the SSA Value
for a given syntactic var, func or const object:
Program.{Const,Func,Var}Value.
Since constants and functions are immutable, the first
two only need a types.Object; but each distinct
reference to a var may return a distinct Value, so the third
requires an ast.Ident parameter too.
Debug information for local vars is encoded in the
instruction stream in the form of DebugRef instructions,
which are a no-op but relate their operand to a particular
ident in the AST. The beauty of this approach is that it
naturally stays consistent during optimisation passes
(e.g. lifting) without additional bookkeeping.
DebugRef instructions are only generated if the DebugMode
builder flag is set; I plan to make the policy more fine-
grained (per function).
DebugRef instructions are inserted for:
- expr(Ident) for rvalue idents
- address.store() for idents that update an lvalue
- address.address() for idents that take address of lvalue
(this new method replaces all uses of lval.(address).addr)
- expr() for all constant expressions
- local ValueSpecs with implicit zero initialization (no RHS)
(this case doesn't call store() or address())
To ensure we don't forget to emit debug info for uses of Idents,
we must use the lvalue mechanism consistently. (Previously,
many simple cases had effectively inlined these functions.)
Similarly setCallFunc no longer inlines expr(Ident).
Also:
- Program.Value() has been inlined & specialized.
- Program.Package() has moved nearer the new lookup functions.
- refactoring: funcSyntax has lost paramFields, resultFields;
gained funcType, which provides access to both.
- add package-level constants to Package.values map.
- opt: don't call localValueSpec for constants.
(The resulting code is always optimised away.)
There are a number of comments asking whether Literals
should have positions. Will address in a follow-up.
Added tests of all interesting cases.
R=gri
CC=golang-dev
https://golang.org/cl/11259044
Objects:
- provide IsExported, SameName, uniqueName methods
- clean up a lot of dependent code
Scopes:
- don't add children to Universe scope (!)
- document Node, WriteTo
Types:
- remove Deref in favor of internal function deref
ssa, ssa/interp:
- introduced local deref, adjusted code
- fixed some "Underlying" bugs (pun intended)
R=adonovan
CC=golang-dev
https://golang.org/cl/11232043
We use the new field to determine whether or not a function is
synthetic, not Pos() == 0, so synthetic functions can have
positions too.
R=gri
CC=golang-dev
https://golang.org/cl/10916044
methodIndex() utility was split and specialized to its two
cases, *Interface vs *Named, which are logically quite
different.
We can't memoize promotion wrappers yet; we need typemap.
Terminology:
- "thunks" are now "wrappers"
- "bridge methods" are now "promotion wrappers"
Where the diff is messy it's just because of indentation.
R=gri
CC=golang-dev
https://golang.org/cl/10282043
Method sets:
- Simplify CallCommon.
Avoid the implicit copy when calling a T method on a *T
receiver. This simplifies clients. Instead we generate
"indirection wrapper" functions that do this (like gc does).
New invariant:
m's receiver type is exactly T for all m in MethodSet(T)
- MakeInterface no longer holds the concrete type's MethodSet.
We can defer its computation this way.
- ssa.Type now just wraps a types.TypeName object.
MethodSets are computed as needed, not eagerly.
Position info:
- new CanonicalPos utility maps ast.Expr to canonical
token.Pos, as returned by {Instruction,Value}.Pos() methods.
- Don't set posn for implicit operations (e.g. varargs array alloc)
- Set position info for ChangeInterface and Slice instructions.
Cosmetic:
- add Member.Token() method
- simplify isPointer
- Omit words "interface", "slice" when printing MakeInterface,
MakeSlice; the type is enough.
- Comments on PathEnclosingInterval.
- Remove Function.FullName() where implicit String() suffices.
Also:
- Exposed NewLiteral to clients.
- Added ssa.Instruction.Parent() *Function
Added ssa.BasicBlock.Parent() *Function.
Added Sanity checks for above.
R=golang-dev, gri
CC=golang-dev
https://golang.org/cl/10166045
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
Implement Pos() method for
Values: Parameter, Capture, Phi. (Not Literal, Builtin.)
Instructions: UnOp, BinOp, Store.
'address' (an lvalue) now needs position of '*' in "*addr".
Also:
- Un-export fields Pos_ Type_ Name_ Block_ from various values/instructions.
Define NewFunction() as a temporary measure.
Will try to eliminate calls from clients...
- Remove Implements{Value,Member,Interface} marker methods.
I've decided I don't like them.
- Func.addParamObj helper.
- Various comment fixes.
R=gri
CC=golang-dev
https://golang.org/cl/9740046
Extracted Builder.findMethod function to handle
methodset/receiver logic common to
function calls (Builder.setCall) and
bound method closure creation (Builder.selector).
Capture: added explicit Name, Type fields to Capture instead
of relying on Outer field, which is now un-exported since its
only purpose is to let Builder.expr(case *ast.FuncLit) know
which values to put in the closure; it is nilled immediately
after.
Simplified Function.lookup() logic: there's no need to walk
the Outer chain each time to set Alloc.Heap=true, as it's
already set during creation of the outermost
Capture{outer:*Alloc}.
Added interp/testdata/boundmeth.go test.
Cosmetic changes:
- add support for bound method thunks to Function.FullName().
- Simplified {Literal,Global,Builtin,Function}.String()
- doc: Captures are no longer necessarily addresses.
- added yet another missing pair of "()" (go/types accessors).
- print "Synthetic" not "Declared at -" for synthetic functions.
- use '$' not center-dot in synthetic identifiers (easier to type).
R=gri
CC=golang-dev
https://golang.org/cl/9654043
Also:
- remove redundant text in doc.go.
- fix (yet more) cases of missing parens in Printf, fallout from
go/types accessors refactoring.
- don't mix spaces and tabs within lines printed by ssa.Function.DumpTo:
it makes it too hard to constructed expected outputs for tests.
(Tabs may appear at line start though.)
Sadly godoc -play won't run this program; it complains it
can't import "code.google.com/p/go.exp/ssa". Any idea why?
R=gri
CC=golang-dev
https://golang.org/cl/9481044
