text: // Package static computes the call graph of a Go program containing
  // only static call edges.
  package static // import "golang.org/x/tools/go/callgraph/static"
  
  import (
  	"golang.org/x/tools/go/callgraph"
  	"golang.org/x/tools/go/ssa"
  	"golang.org/x/tools/go/ssa/ssautil"
  )
  
  // 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
  }
  