// callEdge is called for each edge in the callgraph.
// calleeid is the callee's object node (has otFunction flag).
//
func (a *analysis) callEdge(caller *cgnode, site *callsite, calleeid nodeid) {
obj := a.nodes[calleeid].obj
if obj.flags&otFunction == 0 {
panic(fmt.Sprintf("callEdge %s -> n%d: not a function object", site, calleeid))
}
callee := obj.cgn
if cg := a.result.CallGraph; cg != nil {
// TODO(adonovan): opt: I would expect duplicate edges
// (to wrappers) to arise due to the elimination of
// context information, but I haven't observed any.
// Understand this better.
callgraph.AddEdge(cg.CreateNode(caller.fn), site.instr, cg.CreateNode(callee.fn))
}
if a.log != nil {
fmt.Fprintf(a.log, "\tcall edge %s -> %s\n", site, callee)
}
// Warn about calls to non-intrinsic external functions.
// TODO(adonovan): de-dup these messages.
if fn := callee.fn; fn.Blocks == nil && a.findIntrinsic(fn) == nil {
a.warnf(site.pos(), "unsound call to unknown intrinsic: %s", fn)
a.warnf(fn.Pos(), " (declared here)")
}
}
// addEdge adds the specified call graph edge, and marks it reachable.
// addrTaken indicates whether to mark the callee as "address-taken".
func (r *rta) addEdge(site ssa.CallInstruction, callee *ssa.Function, addrTaken bool) {
r.addReachable(callee, addrTaken)
if g := r.result.CallGraph; g != nil {
if site.Parent() == nil {
panic(site)
}
from := g.CreateNode(site.Parent())
to := g.CreateNode(callee)
callgraph.AddEdge(from, site, to)
}
}
// CallGraph computes the call graph of the specified program
// considering only static calls.
//
func CallGraph(prog *ssa.Program) *callgraph.Graph {
cg := callgraph.New(nil) // TODO(adonovan) eliminate concept of rooted callgraph
// TODO(adonovan): opt: use only a single pass over the ssa.Program.
// TODO(adonovan): opt: this is slower than RTA (perhaps because
// the lower precision means so many edges are allocated)!
for f := range ssautil.AllFunctions(prog) {
fnode := cg.CreateNode(f)
for _, b := range f.Blocks {
for _, instr := range b.Instrs {
if site, ok := instr.(ssa.CallInstruction); ok {
if g := site.Common().StaticCallee(); g != nil {
gnode := cg.CreateNode(g)
callgraph.AddEdge(fnode, site, gnode)
}
}
}
}
}
return cg
}
// CallGraph computes the call graph of the specified program using the
// Class Hierarchy Analysis algorithm.
//
func CallGraph(prog *ssa.Program) *callgraph.Graph {
cg := callgraph.New(nil) // TODO(adonovan) eliminate concept of rooted callgraph
allFuncs := ssautil.AllFunctions(prog)
// funcsBySig contains all functions, keyed by signature. It is
// the effective set of address-taken functions used to resolve
// a dynamic call of a particular signature.
var funcsBySig typeutil.Map // value is []*ssa.Function
// methodsByName contains all methods,
// grouped by name for efficient lookup.
methodsByName := make(map[string][]*ssa.Function)
// methodsMemo records, for every abstract method call call I.f on
// interface type I, the set of concrete methods C.f of all
// types C that satisfy interface I.
methodsMemo := make(map[*types.Func][]*ssa.Function)
lookupMethods := func(m *types.Func) []*ssa.Function {
methods, ok := methodsMemo[m]
if !ok {
I := m.Type().(*types.Signature).Recv().Type().Underlying().(*types.Interface)
for _, f := range methodsByName[m.Name()] {
C := f.Signature.Recv().Type() // named or *named
if types.Implements(C, I) {
methods = append(methods, f)
}
}
methodsMemo[m] = methods
}
return methods
}
for f := range allFuncs {
if f.Signature.Recv() == nil {
// Package initializers can never be address-taken.
if f.Name() == "init" && f.Synthetic == "package initializer" {
continue
}
funcs, _ := funcsBySig.At(f.Signature).([]*ssa.Function)
funcs = append(funcs, f)
funcsBySig.Set(f.Signature, funcs)
} else {
methodsByName[f.Name()] = append(methodsByName[f.Name()], f)
}
}
addEdge := func(fnode *callgraph.Node, site ssa.CallInstruction, g *ssa.Function) {
gnode := cg.CreateNode(g)
callgraph.AddEdge(fnode, site, gnode)
}
addEdges := func(fnode *callgraph.Node, site ssa.CallInstruction, callees []*ssa.Function) {
// Because every call to a highly polymorphic and
// frequently used abstract method such as
// (io.Writer).Write is assumed to call every concrete
// Write method in the program, the call graph can
// contain a lot of duplication.
//
// TODO(adonovan): opt: consider factoring the callgraph
// API so that the Callers component of each edge is a
// slice of nodes, not a singleton.
for _, g := range callees {
addEdge(fnode, site, g)
}
}
for f := range allFuncs {
fnode := cg.CreateNode(f)
for _, b := range f.Blocks {
for _, instr := range b.Instrs {
if site, ok := instr.(ssa.CallInstruction); ok {
call := site.Common()
if call.IsInvoke() {
addEdges(fnode, site, lookupMethods(call.Method))
} else if g := call.StaticCallee(); g != nil {
addEdge(fnode, site, g)
} else if _, ok := call.Value.(*ssa.Builtin); !ok {
callees, _ := funcsBySig.At(call.Signature()).([]*ssa.Function)
addEdges(fnode, site, callees)
}
}
}
}
}
return cg
}