A DebugRef associates a source expression E with an ssa.Value
V, but until now did not record whether V was the value or the
address of E. So, we would guess from the "pointerness" of
the Value, leading to confusion in some cases, e.g.
type N *N
var n N
n = &n // lvalue and rvalue are both pointers
Now we explicitly record 'IsAddress bool' in DebugRef, and
plumb this everywhere: through (*Function).ValueForExpr and
(*Program).VarValue, all the way to forming the pointer
analysis query.
Also:
- VarValue now treats each reference to a global distinctly,
just like it does for other vars. So:
var g int
func f() {
g = 1 // VarValue(g) == Const(1:int), !isAddress
print(g) // VarValue(g) == Global(g), isAddress
}
- DebugRefs are not emitted for references to predeclared
identifiers (nil, built-in).
- DebugRefs no longer prevent lifting of an Alloc var into a
register; now we update or discard the debug info.
- TestValueForExpr: improve coverage of ssa.EnclosingFunction
by putting expectations in methods and init funcs, not just
normal funcs.
- oracle: fix golden file broken by recent
(*types.Var).IsField change.
R=gri
CC=golang-dev
https://golang.org/cl/16610045
This allows us to run/analyze multiple tests.
Also it causes the production code packages to be properly initialized.
Also:
- cmd/ssadump: improved usage message (add example;
incorporate LoadInitialPackages usage; explain how -run
finds main).
- pointer, oracle, ssa/interp: use CreateTestMainPackage.
- ssa/builder.go: remove 'rundefers' instruction from package init,
which no longer uses 'defer'.
R=gri
CC=golang-dev
https://golang.org/cl/15920047
Motivation:
Previously, we assumed that the set of types for which a
complete method set (containing all synthesized wrapper
functions) is required at runtime was the set of types
used as operands to some *ssa.MakeInterface instruction.
In fact, this is an underapproximation because types can
be derived from other ones via reflection, and some of
these may need methods. The reflect.Type API allows *T to
be derived from T, and these may have different method
sets. Reflection also allows almost any subcomponent of a
type to be accessed (with one exception: given T, defined
'type T struct{S}', you can reach S but not struct{S}).
As a result, the pointer analysis was unable to generate
all necessary constraints before running the solver,
causing a crash when reflection derives types whose
methods are unavailable. (A similar problem would afflict
an ahead-of-time compiler based on ssa. The ssa/interp
interpreter was immune only because it does not require
all wrapper methods to be created before execution
begins.)
Description:
This change causes the SSA builder to record, for each
package, the set of all types with non-empty method sets that
are referenced within that package. This set is accessed via
Packages.TypesWithMethodSets(). Program.TypesWithMethodSets()
returns its union across all packages.
The set of references that matter are:
- types of operands to some MakeInterface instruction (as before)
- types of all exported package members
- all subcomponents of the above, recursively.
This is a conservative approximation to the set of types
whose methods may be called dynamically.
We define the owning package of a type as follows:
- the owner of a named type is the package in which it is defined;
- the owner of a pointer-to-named type is the owner of that named type;
- the owner of all other types is nil.
A package must include the method sets for all types that it
owns, and all subcomponents of that type that are not owned by
another package, recursively. Types with an owner appear in
exactly one package; types with no owner (such as struct{T})
may appear within multiple packages.
(A typical Go compiler would emit multiple copies of these
methods as weak symbols; a typical linker would eliminate
duplicates.)
Also:
- go/types/typemap: implement hash function for *Tuple.
- pointer: generate nodes/constraints for all of
ssa.Program.TypesWithMethodSets().
Add rtti.go regression test.
- Add API test of Package.TypesWithMethodSets().
- Set Function.Pkg to nil (again) for wrapper functions,
since these may be shared by many packages.
- Remove a redundant logging statement.
- Document that ssa CREATE phase is in fact sequential.
Fixesgolang/go#6605
R=gri
CC=golang-dev
https://golang.org/cl/14920056
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
Before, we would concatenate all the init() blocks together,
resulting in incorrect treatment of a recovered panic in one
init block: the implicit return would cause the subsequent ones
to be skipped.
The result is simpler, and closer to what gc does.
The additional functions are visible in the call graph,
so some tests required updating.
R=gri
CC=crawshaw, golang-dev
https://golang.org/cl/14671044
Before: func(any, ...interface{}).
After: func(any, ...any)
They are no longer variadic, so you can't write print(x, y...).
(Recall that print(1) and print(interface{}(1)) behave
differently and that this is useful.)
Fixes bug 6560
R=gri
CC=golang-dev
https://golang.org/cl/14455054
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
- removed support for nil constants from go/exact
- instead define a singleton Nil Object (the nil _value_)
- in assignments, follow more closely spec wording
(pending spec CL 14415043)
- removed use of goto in checker.unary
- cleanup around handling of isRepresentable for
constants, with better error messages
- fix missing checks in checker.convertUntyped
- added isTyped (== !isUntyped) and isInterface predicates
- fixed hasNil predicate: unsafe.Pointer also has nil
- adjusted ssa per adonovan
- implememted types.Implements (wrapper arounfd types.MissingMethod)
- use types.Implements in vet (and fix a bug)
R=adonovan, r
CC=golang-dev
https://golang.org/cl/14438052
The $GOROOT/tests may print "BUG" on failure but do not
necessarily exit zero, so we must capture their output too.
Details:
- make plan9 use unix's valueToBytes function (now in externals.go)
- direct the target's syscall.Write and print/println built-ins to a new utility, write(). This may capture the output into a global variable.
R=gri, r
CC=golang-dev
https://golang.org/cl/14550044
- This change implements the correct type-based equivalence
relation for aggregate types. e.g. comparison of struct
types no longer compares the anonymous fields. We do
analogous things for hash().
- equals() and eqnil() have been separated: the former panics
for uncomparable types, the latter permits comparisons of
slice/map/func types against a literal nil and is intended
for use only by "static" ssa.BinOp(EQL), not "dynamic" slice
comparisons encountered during (e.g.) interface comparisons,
which should panic regardless of operand nilness.
- we use a (global) typemap.Hasher to compute type hashes;
hashing the Type.String() value was not sound.
+ tests.
NB, this change unearthed a bug in defer/recover within
init(); it will be fixed in a followup change.
R=gri, crawshaw
CC=golang-dev
https://golang.org/cl/13719043
Running the interpreter on (most of) the tests package in
"encoding" unearthed a couple of ssa.builder bugs, already
fixed. This CL contains the interpreter fixes that were
required. (The "encoding" tests aren't added to the suite
since they're slow.)
Added intrinsics for:
math.Exp
math.Min
hash/crc32.haveSSE42
(reflect.Type).Field
(reflect.Type).NumField
(reflect.Type).NumMethod
reflect.New
(reflect.Value).NumMethod
syscall.RawSyscall (returns ENOSYS)
reflect.Set (a no-op)
Treat unsafe.Pointer -> *T conversions by returning new(T).
This is incorrect but at least preserves type-safety,
which is sufficient for these tests.
hashmap: treat nil *hashmap as an empty map.
R=gri
CC=golang-dev
https://golang.org/cl/12901046
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
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
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
(Its former location was based on a misunderstanding of 'go build'.)
Also: set GOMAXPROCS to NumCPU by default.
R=crawshaw
CC=golang-dev
https://golang.org/cl/13354043
Before, VarValue looked for the ssa.Value for the 'var' object
in the same package as the object was defined, but this is
(obviously) wrong for a cross-package FieldVal selection,
expr.f. The caller must provide the package containing the
reference.
+ test.
Also:
- add 2 TODOs.
- split builder.expr into two functions so we don't need
defer, which makes panic dumps harder to read.
R=golang-dev, crawshaw
CC=golang-dev
https://golang.org/cl/13257045
Previously, if the result was not wanted, the received
(value, ok) tuple had no type for 'value'.
Now it is always set to the channel's element type.
Also: set the position on such receive instructions to that of
the = or := token, and document it.
+ (indirect) test via pointer analysis.
R=crawshaw, gri
CC=golang-dev
https://golang.org/cl/12956052
Map literals should use the same recursion logic as
struct/array/slice literals to apply an implicit &-operator to
the nested literals when a pointer is wanted.
+ test.
Also:
- ensure we set the source location for all Lookup and
MapUpdate instructions.
- remove obsolete address.object field.
R=gri, crawshaw
CC=golang-dev
https://golang.org/cl/12787048
It is needed after all, as I discovered in the pointer analysis.
(ssa needs more API test coverage.)
Also:
- sanity: remove debugging cruft
- promote: don't redundantly include the function's
own name in its Synthetic string.
- print: IntuitiveMethodSet utility fixes a bug in the
printing logic (for interface types, mset(*T) is empty).
The function is also used by the Oracle.
R=crawshaw
CC=golang-dev
https://golang.org/cl/13116043
&x.f, &x[0], x[i:j], &*x all must panic if x==nil.
The first three are already addressed by the semantics of
FieldAddr, IndexAddr, Slice; updated docs to reflect this.
The final case requires generation of an additional dynamic check.
See golang.org/s/go12nil for details.
Tested on $GOROOT/test/nilptr2.go (with patch from CL 13108043)
Also: remove a TODO where a no-op will do.
R=gri, crawshaw
CC=golang-dev, rsc
https://golang.org/cl/13064044
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
Package.CreateTestMainFunction() creates a function called
main and adds it to the package. This function calls
testing.Main in the Go library with the appropriate arguments:
slices of test, benchmark and example functions from the
package.
Tested by running the interpreter on the following tests:
- unicode/script_test.go
- unicode/digit_test.go
- hash/crc32/crc32_test.go
- path/path_test.go
It's also covered indirectly via the pointer analysis.
R=crawshaw, gri
CC=golang-dev
https://golang.org/cl/12814046
Was broken by CL 12378043.
- factored out some error checking code
- adjusted error positions
R=adonovan
TBR=adonovan
CC=golang-dev
https://golang.org/cl/12401043
e.g.
type T int
func (T) f() {}
var t T
_ = t.f // method value: should have signature "func()", no receiver
Also:
- ssa: add sanity check that helped diagnose this.
R=gri
CC=golang-dev
https://golang.org/cl/12283043
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
The required changes were surprisingly minimal (I was hoping for a net
code deletion) because ssa is essentially doing its own type inference
for the three value,ok operators---and it continues to have to do so.
To see why, consider:
var i interface{}; var ok bool
i, ok := (map[string]string)(nil)[""]
Before, go/types inferred interface{} for the RHS of the assignment,
and now it infers (interface{}, bool), yet neither of these is what
ssa needs: it needs to know that the map values were strings so
that it can emit a lookup of the right type followed by a conversion
from string to interface{}.
TBR=gri
CC=golang-dev
https://golang.org/cl/11988044
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
