// valueOffsetNode ascertains the node for tuple/struct value v,
// then returns the node for its subfield #index.
//
func (a *analysis) valueOffsetNode(v ssa.Value, index int) nodeid {
id := a.valueNode(v)
if id == 0 {
panic(fmt.Sprintf("cannot offset within n0: %s = %s", v.Name(), v))
}
return id + nodeid(a.offsetOf(v.Type(), index))
}
// genOffsetAddr generates constraints for a 'v=ptr.field' (FieldAddr)
// or 'v=ptr[*]' (IndexAddr) instruction v.
func (a *analysis) genOffsetAddr(cgn *cgnode, v ssa.Value, ptr nodeid, offset uint32) {
dst := a.valueNode(v)
if obj := a.objectNode(cgn, v); obj != 0 {
// Pre-apply offsetAddrConstraint.solve().
a.addressOf(v.Type(), dst, obj)
} else {
a.offsetAddr(v.Type(), dst, ptr, offset)
}
}
// AddQuery adds v to Config.IndirectQueries.
// Precondition: CanPoint(v.Type().Underlying().(*types.Pointer).Elem()).
func (c *Config) AddIndirectQuery(v ssa.Value) {
if c.IndirectQueries == nil {
c.IndirectQueries = make(map[ssa.Value]struct{})
}
if !CanPoint(mustDeref(v.Type())) {
panic(fmt.Sprintf("%s is not the address of a pointer-like value: %s", v, v.Type()))
}
c.IndirectQueries[v] = struct{}{}
}
// AddQuery adds v to Config.Queries.
// Precondition: CanPoint(v.Type()).
// TODO(adonovan): consider returning a new Pointer for this query,
// which will be initialized during analysis. That avoids the needs
// for the corresponding ssa.Value-keyed maps in Config and Result.
func (c *Config) AddQuery(v ssa.Value) {
if !CanPoint(v.Type()) {
panic(fmt.Sprintf("%s is not a pointer-like value: %s", v, v.Type()))
}
if c.Queries == nil {
c.Queries = make(map[ssa.Value]struct{})
}
c.Queries[v] = struct{}{}
}
func (fr *frame) canAvoidElementLoad(ptr ssa.Value) bool {
for _, ref := range *ptr.Referrers() {
switch ref := ref.(type) {
case *ssa.Field:
case *ssa.Index:
if ref.X != ptr {
return false
}
// ok
default:
return false
}
}
return true
}
func (fr *frame) get(key ssa.Value) value {
switch key := key.(type) {
case nil:
// Hack; simplifies handling of optional attributes
// such as ssa.Slice.{Low,High}.
return nil
case *ssa.Function, *ssa.Builtin:
return key
case *ssa.Const:
return constValue(key)
case *ssa.Global:
if r, ok := fr.i.globals[key]; ok {
return r
}
}
if r, ok := fr.env[key]; ok {
return r
}
panic(fmt.Sprintf("get: no value for %T: %v", key, key.Name()))
}
// setValueNode associates node id with the value v.
// cgn identifies the context iff v is a local variable.
//
func (a *analysis) setValueNode(v ssa.Value, id nodeid, cgn *cgnode) {
if cgn != nil {
a.localval[v] = id
} else {
a.globalval[v] = id
}
if a.log != nil {
fmt.Fprintf(a.log, "\tval[%s] = n%d (%T)\n", v.Name(), id, v)
}
// Due to context-sensitivity, we may encounter the same Value
// in many contexts. We merge them to a canonical node, since
// that's what all clients want.
// Record the (v, id) relation if the client has queried pts(v).
if _, ok := a.config.Queries[v]; ok {
t := v.Type()
ptr, ok := a.result.Queries[v]
if !ok {
// First time? Create the canonical query node.
ptr = Pointer{a, a.addNodes(t, "query")}
a.result.Queries[v] = ptr
}
a.result.Queries[v] = ptr
a.copy(ptr.n, id, a.sizeof(t))
}
// Record the (*v, id) relation if the client has queried pts(*v).
if _, ok := a.config.IndirectQueries[v]; ok {
t := v.Type()
ptr, ok := a.result.IndirectQueries[v]
if !ok {
// First time? Create the canonical indirect query node.
ptr = Pointer{a, a.addNodes(v.Type(), "query.indirect")}
a.result.IndirectQueries[v] = ptr
}
a.genLoad(cgn, ptr.n, v, 0, a.sizeof(t))
}
}
// valueNode returns the id of the value node for v, creating it (and
// the association) as needed. It may return zero for uninteresting
// values containing no pointers.
//
func (a *analysis) valueNode(v ssa.Value) nodeid {
// Value nodes for locals are created en masse by genFunc.
if id, ok := a.localval[v]; ok {
return id
}
// Value nodes for globals are created on demand.
id, ok := a.globalval[v]
if !ok {
var comment string
if a.log != nil {
comment = v.String()
}
id = a.addNodes(v.Type(), comment)
if obj := a.objectNode(nil, v); obj != 0 {
a.addressOf(v.Type(), id, obj)
}
a.setValueNode(v, id, nil)
}
return id
}
// Declare creates an llvm.dbg.declare call for the specified function
// parameter or local variable.
func (d *DIBuilder) Declare(b llvm.Builder, v ssa.Value, llv llvm.Value, paramIndex int) {
tag := tagAutoVariable
if paramIndex >= 0 {
tag = tagArgVariable
}
var diFile llvm.Metadata
var line int
if file := d.fset.File(v.Pos()); file != nil {
line = file.Line(v.Pos())
diFile = d.getFile(file)
}
localVar := d.builder.CreateLocalVariable(d.scope(), llvm.DILocalVariable{
Tag: tag,
Name: llv.Name(),
File: diFile,
Line: line,
ArgNo: paramIndex + 1,
Type: d.DIType(v.Type()),
})
expr := d.builder.CreateExpression(nil)
d.builder.InsertDeclareAtEnd(llv, localVar, expr, b.GetInsertBlock())
}
// objectNode returns the object to which v points, if known.
// In other words, if the points-to set of v is a singleton, it
// returns the sole label, zero otherwise.
//
// We exploit this information to make the generated constraints less
// dynamic. For example, a complex load constraint can be replaced by
// a simple copy constraint when the sole destination is known a priori.
//
// Some SSA instructions always have singletons points-to sets:
// Alloc, Function, Global, MakeChan, MakeClosure, MakeInterface, MakeMap, MakeSlice.
// Others may be singletons depending on their operands:
// FreeVar, Const, Convert, FieldAddr, IndexAddr, Slice.
//
// Idempotent. Objects are created as needed, possibly via recursion
// down the SSA value graph, e.g IndexAddr(FieldAddr(Alloc))).
//
func (a *analysis) objectNode(cgn *cgnode, v ssa.Value) nodeid {
switch v.(type) {
case *ssa.Global, *ssa.Function, *ssa.Const, *ssa.FreeVar:
// Global object.
obj, ok := a.globalobj[v]
if !ok {
switch v := v.(type) {
case *ssa.Global:
obj = a.nextNode()
a.addNodes(mustDeref(v.Type()), "global")
a.endObject(obj, nil, v)
case *ssa.Function:
obj = a.makeFunctionObject(v, nil)
case *ssa.Const:
// not addressable
case *ssa.FreeVar:
// not addressable
}
if a.log != nil {
fmt.Fprintf(a.log, "\tglobalobj[%s] = n%d\n", v, obj)
}
a.globalobj[v] = obj
}
return obj
}
// Local object.
obj, ok := a.localobj[v]
if !ok {
switch v := v.(type) {
case *ssa.Alloc:
obj = a.nextNode()
a.addNodes(mustDeref(v.Type()), "alloc")
a.endObject(obj, cgn, v)
case *ssa.MakeSlice:
obj = a.nextNode()
a.addNodes(sliceToArray(v.Type()), "makeslice")
a.endObject(obj, cgn, v)
case *ssa.MakeChan:
obj = a.nextNode()
a.addNodes(v.Type().Underlying().(*types.Chan).Elem(), "makechan")
a.endObject(obj, cgn, v)
case *ssa.MakeMap:
obj = a.nextNode()
tmap := v.Type().Underlying().(*types.Map)
a.addNodes(tmap.Key(), "makemap.key")
elem := a.addNodes(tmap.Elem(), "makemap.value")
// To update the value field, MapUpdate
// generates store-with-offset constraints which
// the presolver can't model, so we must mark
// those nodes indirect.
for id, end := elem, elem+nodeid(a.sizeof(tmap.Elem())); id < end; id++ {
a.mapValues = append(a.mapValues, id)
}
a.endObject(obj, cgn, v)
case *ssa.MakeInterface:
tConc := v.X.Type()
obj = a.makeTagged(tConc, cgn, v)
// Copy the value into it, if nontrivial.
if x := a.valueNode(v.X); x != 0 {
a.copy(obj+1, x, a.sizeof(tConc))
}
case *ssa.FieldAddr:
if xobj := a.objectNode(cgn, v.X); xobj != 0 {
obj = xobj + nodeid(a.offsetOf(mustDeref(v.X.Type()), v.Field))
}
case *ssa.IndexAddr:
if xobj := a.objectNode(cgn, v.X); xobj != 0 {
obj = xobj + 1
}
case *ssa.Slice:
obj = a.objectNode(cgn, v.X)
case *ssa.Convert:
// TODO(adonovan): opt: handle these cases too:
// - unsafe.Pointer->*T conversion acts like Alloc
// - string->[]byte/[]rune conversion acts like MakeSlice
}
if a.log != nil {
fmt.Fprintf(a.log, "\tlocalobj[%s] = n%d\n", v.Name(), obj)
}
a.localobj[v] = obj
}
return obj
}
func escapes(val ssa.Value, bb *ssa.BasicBlock, pending []ssa.Value) bool {
for _, p := range pending {
if val == p {
return false
}
}
for _, ref := range *val.Referrers() {
switch ref := ref.(type) {
case *ssa.Phi:
// We must consider the variable to have escaped if it is
// possible for the program to see more than one "version"
// of the variable at once, as this requires the program
// to use heap allocation for the multiple versions.
//
// I (pcc) think that this is only possible (without stores)
// in the case where a phi node that (directly or indirectly)
// refers to the allocation dominates the allocation.
if ref.Block().Dominates(bb) {
return true
}
if escapes(ref, bb, append(pending, val)) {
return true
}
case *ssa.BinOp, *ssa.ChangeType, *ssa.Convert, *ssa.ChangeInterface, *ssa.MakeInterface, *ssa.Slice, *ssa.FieldAddr, *ssa.IndexAddr, *ssa.TypeAssert, *ssa.Extract:
if escapes(ref.(ssa.Value), bb, append(pending, val)) {
return true
}
case *ssa.Range, *ssa.DebugRef:
continue
case *ssa.UnOp:
if ref.Op == token.MUL || ref.Op == token.ARROW {
continue
}
if escapes(ref, bb, append(pending, val)) {
return true
}
case *ssa.Store:
if val == ref.Val {
return true
}
case *ssa.Call:
if builtin, ok := ref.Call.Value.(*ssa.Builtin); ok {
switch builtin.Name() {
case "cap", "len", "copy", "ssa:wrapnilchk":
continue
case "append":
if ref.Call.Args[0] == val && escapes(ref, bb, append(pending, val)) {
return true
}
default:
return true
}
} else {
return true
}
default:
return true
}
}
return false
}
func (fr *frame) value(v ssa.Value) (result *govalue) {
switch v := v.(type) {
case nil:
return nil
case *ssa.Function:
return fr.resolveFunctionDescriptor(v)
case *ssa.Const:
return fr.newValueFromConst(v.Value, v.Type())
case *ssa.Global:
if g, ok := fr.globals[v]; ok {
return newValue(g, v.Type())
}
// Create an external global. Globals for this package are defined
// on entry to translatePackage, and have initialisers.
llelemtyp := fr.llvmtypes.ToLLVM(deref(v.Type()))
vname := fr.types.mc.mangleGlobalName(v)
llglobal := llvm.AddGlobal(fr.module.Module, llelemtyp, vname)
llglobal = llvm.ConstBitCast(llglobal, fr.llvmtypes.ToLLVM(v.Type()))
fr.globals[v] = llglobal
return newValue(llglobal, v.Type())
}
if value, ok := fr.env[v]; ok {
return value
}
panic(fmt.Errorf("Instruction %q not visited yet", v.Name()))
}