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// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package ssa
// This file defines utilities for population of method sets.
import (
"fmt"
"go/types"
)
// MethodValue returns the Function implementing method sel, building
// wrapper methods on demand. It returns nil if sel denotes an
// abstract (interface) method.
//
// Precondition: sel.Kind() == MethodVal.
//
// Thread-safe.
//
// EXCLUSIVE_LOCKS_ACQUIRED(prog.methodsMu)
//
func (prog *Program) MethodValue(sel *types.Selection) *Function {
if sel.Kind() != types.MethodVal {
panic(fmt.Sprintf("Method(%s) kind != MethodVal", sel))
}
T := sel.Recv()
if isInterface(T) {
return nil // abstract method
}
if prog.mode&LogSource != 0 {
defer logStack("Method %s %v", T, sel)()
}
prog.methodsMu.Lock()
defer prog.methodsMu.Unlock()
return prog.addMethod(prog.createMethodSet(T), sel)
}
// LookupMethod returns the implementation of the method of type T
// identified by (pkg, name). It returns nil if the method exists but
// is abstract, and panics if T has no such method.
//
func (prog *Program) LookupMethod(T types.Type, pkg *types.Package, name string) *Function {
sel := prog.MethodSets.MethodSet(T).Lookup(pkg, name)
if sel == nil {
panic(fmt.Sprintf("%s has no method %s", T, types.Id(pkg, name)))
}
return prog.MethodValue(sel)
}
// methodSet contains the (concrete) methods of a non-interface type.
type methodSet struct {
mapping map[string]*Function // populated lazily
complete bool // mapping contains all methods
}
// Precondition: !isInterface(T).
// EXCLUSIVE_LOCKS_REQUIRED(prog.methodsMu)
func (prog *Program) createMethodSet(T types.Type) *methodSet {
mset, ok := prog.methodSets.At(T).(*methodSet)
if !ok {
mset = &methodSet{mapping: make(map[string]*Function)}
prog.methodSets.Set(T, mset)
}
return mset
}
// EXCLUSIVE_LOCKS_REQUIRED(prog.methodsMu)
func (prog *Program) addMethod(mset *methodSet, sel *types.Selection) *Function {
if sel.Kind() == types.MethodExpr {
panic(sel)
}
id := sel.Obj().Id()
fn := mset.mapping[id]
if fn == nil {
obj := sel.Obj().(*types.Func)
needsPromotion := len(sel.Index()) > 1
needsIndirection := !isPointer(recvType(obj)) && isPointer(sel.Recv())
if needsPromotion || needsIndirection {
fn = makeWrapper(prog, sel)
} else {
fn = prog.declaredFunc(obj)
}
if fn.Signature.Recv() == nil {
panic(fn) // missing receiver
}
mset.mapping[id] = fn
}
return fn
}
// RuntimeTypes returns a new unordered slice containing all
// concrete types in the program for which a complete (non-empty)
// method set is required at run-time.
//
// Thread-safe.
//
// EXCLUSIVE_LOCKS_ACQUIRED(prog.methodsMu)
//
func (prog *Program) RuntimeTypes() []types.Type {
prog.methodsMu.Lock()
defer prog.methodsMu.Unlock()
var res []types.Type
prog.methodSets.Iterate(func(T types.Type, v interface{}) {
if v.(*methodSet).complete {
res = append(res, T)
}
})
return res
}
// declaredFunc returns the concrete function/method denoted by obj.
// Panic ensues if there is none.
//
func (prog *Program) declaredFunc(obj *types.Func) *Function {
if v := prog.packageLevelValue(obj); v != nil {
return v.(*Function)
}
panic("no concrete method: " + obj.String())
}
// needMethodsOf ensures that runtime type information (including the
// complete method set) is available for the specified type T and all
// its subcomponents.
//
// needMethodsOf must be called for at least every type that is an
// operand of some MakeInterface instruction, and for the type of
// every exported package member.
//
// Precondition: T is not a method signature (*Signature with Recv()!=nil).
//
// Thread-safe. (Called via emitConv from multiple builder goroutines.)
//
// TODO(adonovan): make this faster. It accounts for 20% of SSA build time.
//
// EXCLUSIVE_LOCKS_ACQUIRED(prog.methodsMu)
//
func (prog *Program) needMethodsOf(T types.Type) {
prog.methodsMu.Lock()
prog.needMethods(T, false)
prog.methodsMu.Unlock()
}
// Precondition: T is not a method signature (*Signature with Recv()!=nil).
// Recursive case: skip => don't create methods for T.
//
// EXCLUSIVE_LOCKS_REQUIRED(prog.methodsMu)
//
func (prog *Program) needMethods(T types.Type, skip bool) {
// Each package maintains its own set of types it has visited.
if prevSkip, ok := prog.runtimeTypes.At(T).(bool); ok {
// needMethods(T) was previously called
if !prevSkip || skip {
return // already seen, with same or false 'skip' value
}
}
prog.runtimeTypes.Set(T, skip)
tmset := prog.MethodSets.MethodSet(T)
if !skip && !isInterface(T) && tmset.Len() > 0 {
// Create methods of T.
mset := prog.createMethodSet(T)
if !mset.complete {
mset.complete = true
n := tmset.Len()
for i := 0; i < n; i++ {
prog.addMethod(mset, tmset.At(i))
}
}
}
// Recursion over signatures of each method.
for i := 0; i < tmset.Len(); i++ {
sig := tmset.At(i).Type().(*types.Signature)
prog.needMethods(sig.Params(), false)
prog.needMethods(sig.Results(), false)
}
switch t := T.(type) {
case *types.Basic:
// nop
case *types.Interface:
// nop---handled by recursion over method set.
case *types.Pointer:
prog.needMethods(t.Elem(), false)
case *types.Slice:
prog.needMethods(t.Elem(), false)
case *types.Chan:
prog.needMethods(t.Elem(), false)
case *types.Map:
prog.needMethods(t.Key(), false)
prog.needMethods(t.Elem(), false)
case *types.Signature:
if t.Recv() != nil {
panic(fmt.Sprintf("Signature %s has Recv %s", t, t.Recv()))
}
prog.needMethods(t.Params(), false)
prog.needMethods(t.Results(), false)
case *types.Named:
// A pointer-to-named type can be derived from a named
// type via reflection. It may have methods too.
prog.needMethods(types.NewPointer(T), false)
// Consider 'type T struct{S}' where S has methods.
// Reflection provides no way to get from T to struct{S},
// only to S, so the method set of struct{S} is unwanted,
// so set 'skip' flag during recursion.
prog.needMethods(t.Underlying(), true)
case *types.Array:
prog.needMethods(t.Elem(), false)
case *types.Struct:
for i, n := 0, t.NumFields(); i < n; i++ {
prog.needMethods(t.Field(i).Type(), false)
}
case *types.Tuple:
for i, n := 0, t.Len(); i < n; i++ {
prog.needMethods(t.At(i).Type(), false)
}
default:
panic(T)
}
}