go.tools/ssa: memoize synthesis of all wrapper methods.

methodIndex() utility was split and specialized to its two
cases, *Interface vs *Named, which are logically quite
different.

We can't memoize promotion wrappers yet; we need typemap.

Terminology:
- "thunks" are now "wrappers"
- "bridge methods" are now "promotion wrappers"

Where the diff is messy it's just because of indentation.

R=gri
CC=golang-dev
https://golang.org/cl/10282043

go/types/types.go

@@ -365,7 +365,7 @@ func NewNamed(obj *TypeName, underlying Type, methods []*Func) *Named {
 // TypeName returns the type name for the named type t.
 func (t *Named) Obj() *TypeName { return t.obj }
 
-// NumMethods returns the number of methods directly associated with named type t.
+// NumMethods returns the number of explicit methods whose receiver is named type t.
 func (t *Named) NumMethods() int { return len(t.methods) }
 
 // Method returns the i'th method of named type t for 0 <= i < t.NumMethods().

ssa/builder.go

@@ -5,7 +5,7 @@ package ssa
 // SSA construction has two phases, CREATE and BUILD.  In the CREATE phase
 // (create.go), all packages are constructed and type-checked and
 // definitions of all package members are created, method-sets are
-// computed, and bridge methods are synthesized.  The create phase
+// computed, and wrapper methods are synthesized.  The create phase
 // proceeds in topological order over the import dependency graph,
 // initiated by client calls to CreatePackages.
 //
@@ -345,7 +345,7 @@ func (b *builder) selector(fn *Function, e *ast.SelectorExpr, wantAddr, escaping
 	if !wantAddr {
 		if m, recv := b.findMethod(fn, e.X, id); m != nil {
 			c := &MakeClosure{
-				Fn:       makeBoundMethodThunk(fn.Prog, m, recv.Type()),
+				Fn:       boundMethodWrapper(m),
 				Bindings: []Value{recv},
 			}
 			c.setPos(e.Sel.Pos())
@@ -743,8 +743,8 @@ func (b *builder) expr(fn *Function, e ast.Expr) Value {
 				return m
 			}
 
-			// T must be an interface; return method thunk.
+			// T must be an interface; return wrapper.
-			return makeImethodThunk(fn.Prog, typ, id)
+			return interfaceMethodWrapper(fn.Prog, typ, id)
 		}
 
 		// e.f where e is an expression.  f may be a method.
@@ -905,7 +905,7 @@ func (b *builder) setCallFunc(fn *Function, e *ast.CallExpr, c *CallCommon) {
 		// Case 4: x.f() where a dynamically dispatched call
 		// to an interface method f.  f is a 'func' object in
 		// the Methods of types.Interface X
-		c.Method, _ = methodIndex(t, id)
+		c.Method, _ = interfaceMethodIndex(t, id)
 		c.Recv = b.expr(fn, sel.X)
 
 	default:

ssa/create.go

@@ -42,6 +42,8 @@ func NewProgram(fset *token.FileSet, mode BuilderMode) *Program {
 		methodSets:          make(map[types.Type]MethodSet),
 		concreteMethods:     make(map[*types.Func]*Function),
 		indirectionWrappers: make(map[*Function]*Function),
+		boundMethodWrappers: make(map[*Function]*Function),
+		ifaceMethodWrappers: make(map[*types.Func]*Function),
 		mode:                mode,
 	}
 
@@ -130,8 +132,9 @@ func memberFromObject(pkg *Package, obj types.Object, syntax ast.Node) {
 			pkg.Members[name] = fn
 		} else {
 			// Method declaration.
-			nt := recv.Type().Deref().(*types.Named)
+			_, method := namedTypeMethodIndex(
-			_, method := methodIndex(nt, MakeId(name, pkg.Types))
+				recv.Type().Deref().(*types.Named),
+				MakeId(name, pkg.Types))
 			pkg.Prog.concreteMethods[method] = fn
 		}
 

ssa/emit.go

@@ -286,7 +286,7 @@ func emitTypeTest(f *Function, x Value, t types.Type, pos token.Pos) Value {
 
 // emitTailCall emits to f a function call in tail position.  The
 // caller is responsible for all fields of 'call' except its type.
-// Intended for delegating bridge methods.
+// Intended for wrapper methods.
 // Precondition: f does/will not use deferred procedure calls.
 // Postcondition: f.currentBlock is nil.
 //

ssa/func.go

@@ -443,10 +443,10 @@ func (f *Function) emit(instr Instruction) Value {
 //      "math.IsNaN"                // a package-level function
 //      "IsNaN"                     // intra-package reference to same
 //      "(*sync.WaitGroup).Add"     // a declared method
-//      "(*exp/ssa.Ret).Block"      // a bridge method
+//      "(*exp/ssa.Ret).Block"      // a promotion wrapper method
-//      "(ssa.Instruction).Block"   // an interface method thunk
+//      "(ssa.Instruction).Block"   // an interface method wrapper
 //      "func@5.32"                 // an anonymous function
-//      "bound$(*T).f"              // a bound method thunk
+//      "bound$(*T).f"              // a bound method wrapper
 //
 func (f *Function) FullName() string {
 	return f.fullName(nil)
@@ -467,11 +467,11 @@ func (f *Function) fullName(from *Package) string {
 	if f.Pkg == nil {
 		var recvType types.Type
 		if recv != nil {
-			recvType = recv.Type() // bridge method
+			recvType = recv.Type() // promotion wrapper
 		} else if strings.HasPrefix(f.name, "bound$") {
-			return f.name // bound method thunk
+			return f.name // bound method wrapper
 		} else {
-			recvType = f.Params[0].Type() // interface method thunk
+			recvType = f.Params[0].Type() // interface method wrapper
 		}
 		return fmt.Sprintf("(%s).%s", recvType, f.name)
 	}

ssa/print.go

@@ -385,7 +385,7 @@ func (p *Package) DumpTo(w io.Writer) {
 			// We display only mset(*T) since its keys
 			// are a superset of mset(T)'s keys, though the
 			// methods themselves may differ,
-			// e.g. different bridge methods.
+			// e.g. promotion wrappers.
 			// NB: if mem.Type() is a pointer, mset is empty.
 			mset := p.Prog.MethodSet(pointer(mem.Type()))
 			var keys ids

ssa/promote.go

@@ -1,9 +1,15 @@
 package ssa
 
-// This file defines algorithms related to "promotion" of field and
+// This file defines utilities for method-set computation, synthesis
-// method selector expressions e.x, such as desugaring implicit field
+// of wrapper methods, and desugaring of implicit field selections.
-// and method selections, method-set computation, and construction of
+//
-// synthetic "bridge" methods.
+// Wrappers include:
+// - promotion wrappers for methods of embedded fields.
+// - interface method wrappers for closures of I.f.
+// - bound method wrappers, for uncalled obj.Method closures.
+// - indirection wrappers, for calls to T-methods on a *T receiver.
+
+// TODO(adonovan): rename to methods.go.
 
 import (
 	"code.google.com/p/go.tools/go/types"
@@ -90,9 +96,9 @@ func (c candidate) ptrRecv() bool {
 	return c.concrete != nil && isPointer(c.concrete.Signature.Recv().Type())
 }
 
-// MethodSet returns the method set for type typ,
+// MethodSet returns the method set for type typ, building wrapper
-// building bridge methods as needed for promoted methods
+// methods as needed for embedded field promotion, and indirection for
-// and indirection wrappers for *T receiver types.
+// *T receiver types, etc.
 // A nil result indicates an empty set.
 //
 // Thread-safe.
@@ -101,8 +107,8 @@ func (p *Program) MethodSet(typ types.Type) MethodSet {
 		return nil
 	}
 
-	p.methodSetsMu.Lock()
+	p.methodsMu.Lock()
-	defer p.methodSetsMu.Unlock()
+	defer p.methodsMu.Unlock()
 
 	// TODO(adonovan): Using Types as map keys doesn't properly
 	// de-dup.  e.g. *Named are canonical but *Struct and
@@ -200,7 +206,7 @@ func buildMethodSet(prog *Program, typ types.Type) MethodSet {
 		list, next = next, list[:0] // reuse array
 	}
 
-	// Build method sets and bridge methods.
+	// Build method sets and wrapper methods.
 	mset := make(MethodSet)
 	for id, cand := range cands {
 		if cand == nil {
@@ -223,7 +229,7 @@ func buildMethodSet(prog *Program, typ types.Type) MethodSet {
 				method = indirectionWrapper(method)
 			}
 		} else {
-			method = makeBridgeMethod(prog, typ, cand)
+			method = promotionWrapper(prog, typ, cand)
 		}
 		if method == nil {
 			panic("unexpected nil method in method set")
@@ -251,7 +257,7 @@ func addCandidate(m map[Id]*candidate, id Id, method *types.Func, concrete *Func
 	}
 }
 
-// makeBridgeMethod creates a synthetic Function that delegates to a
+// promotionWrapper returns a synthetic Function that delegates to a
 // "promoted" method.  For example, given these decls:
 //
 //    type A struct {B}
@@ -259,24 +265,25 @@ func addCandidate(m map[Id]*candidate, id Id, method *types.Func, concrete *Func
 //    type C ...
 //    func (*C) f()
 //
-// then makeBridgeMethod(typ=A, cand={method:(*C).f, path:[B,*C]}) will
+// then promotionWrapper(typ=A, cand={method:(*C).f, path:[B,*C]}) will
-// synthesize this bridge method:
+// synthesize this wrapper method:
 //
 //    func (a A) f() { return a.B.C->f() }
 //
 // prog is the program to which the synthesized method will belong.
-// typ is the receiver type of the bridge method.  cand is the
+// typ is the receiver type of the wrapper method.  cand is the
 // candidate method to be promoted; it may be concrete or an interface
 // method.
 //
-func makeBridgeMethod(prog *Program, typ types.Type, cand *candidate) *Function {
+func promotionWrapper(prog *Program, typ types.Type, cand *candidate) *Function {
 	old := cand.method.Type().(*types.Signature)
 	sig := types.NewSignature(types.NewVar(token.NoPos, nil, "recv", typ), old.Params(), old.Results(), old.IsVariadic())
 
+	// TODO(adonovan): consult memoization cache keyed by (typ, cand).
+	// Needs typemap.  Also needs hash/eq functions for 'candidate'.
 	if prog.mode&LogSource != 0 {
-		defer logStack("makeBridgeMethod %s, %s, type %s", typ, cand, sig)()
+		defer logStack("promotionWrapper %s, %s, type %s", typ, cand, sig)()
 	}
-
 	fn := &Function{
 		name:      cand.method.Name(),
 		Signature: sig,
@@ -286,7 +293,7 @@ func makeBridgeMethod(prog *Program, typ types.Type, cand *candidate) *Function
 	fn.addSpilledParam(sig.Recv())
 	createParams(fn)
 
-	// Each bridge method performs a sequence of selections,
+	// Each promotion wrapper performs a sequence of selections,
 	// then tailcalls the promoted method.
 	// We use pointer arithmetic (FieldAddr possibly followed by
 	// Load) in preference to value extraction (Field possibly
@@ -320,14 +327,9 @@ func makeBridgeMethod(prog *Program, typ types.Type, cand *candidate) *Function
 		c.Call.Func = cand.concrete
 		c.Call.Args = append(c.Call.Args, v)
 	} else {
-		c.Call.Method = -1
 		iface := v.Type().Underlying().(*types.Interface)
-		for i, n := 0, iface.NumMethods(); i < n; i++ {
+		id := MakeId(cand.method.Name(), cand.method.Pkg())
-			if iface.Method(i) == cand.method {
+		c.Call.Method, _ = interfaceMethodIndex(iface, id)
-				c.Call.Method = i
-				break
-			}
-		}
 		c.Call.Recv = v
 	}
 	for _, arg := range fn.Params[1:] {
@@ -338,7 +340,7 @@ func makeBridgeMethod(prog *Program, typ types.Type, cand *candidate) *Function
 	return fn
 }
 
-// createParams creates parameters for bridge method fn based on its
+// createParams creates parameters for wrapper method fn based on its
 // Signature.Params, which do not include the receiver.
 //
 func createParams(fn *Function) {
@@ -352,18 +354,18 @@ func createParams(fn *Function) {
 	}
 }
 
-// Thunks for standalone interface methods ----------------------------------------
+// Wrappers for standalone interface methods ----------------------------------
 
-// makeImethodThunk returns a synthetic thunk function permitting a
+// interfaceMethodWrapper returns a synthetic wrapper function permitting a
 // method id of interface typ to be called like a standalone function,
 // e.g.:
 //
 //   type I interface { f(x int) R }
-//   m := I.f  // thunk
+//   m := I.f  // wrapper
 //   var i I
 //   m(i, 0)
 //
-// The thunk is defined as if by:
+// The wrapper is defined as if by:
 //
 //   func I.f(i I, x int, ...) R {
 //     return i.f(x, ...)
@@ -372,18 +374,25 @@ func createParams(fn *Function) {
 // TODO(adonovan): opt: currently the stub is created even when used
 // in call position: I.f(i, 0).  Clearly this is suboptimal.
 //
-// TODO(adonovan): memoize creation of these functions in the Program.
+// EXCLUSIVE_LOCKS_ACQUIRED(meth.Prog.methodsMu)
 //
-func makeImethodThunk(prog *Program, typ types.Type, id Id) *Function {
+func interfaceMethodWrapper(prog *Program, typ types.Type, id Id) *Function {
+	index, meth := interfaceMethodIndex(typ.Underlying().(*types.Interface), id)
+	prog.methodsMu.Lock()
+	defer prog.methodsMu.Unlock()
+	// If one interface embeds another they'll share the same
+	// wrappers for common methods.  This is safe, but it might
+	// confuse some tools because of the implicit interface
+	// conversion applied to the first argument.  If this becomes
+	// a problem, we should include 'typ' in the memoization key.
+	fn, ok := prog.ifaceMethodWrappers[meth]
+	if !ok {
 		if prog.mode&LogSource != 0 {
-		defer logStack("makeImethodThunk %s.%s", typ, id)()
+			defer logStack("interfaceMethodWrapper %s.%s", typ, id)()
 		}
-	itf := typ.Underlying().(*types.Interface)
+		fn = &Function{
-	index, meth := methodIndex(itf, id)
-	sig := *meth.Type().(*types.Signature) // copy; shared Values
-	fn := &Function{
 			name:      meth.Name(),
-		Signature: &sig,
+			Signature: meth.Type().(*types.Signature),
 			Prog:      prog,
 		}
 		fn.startBody()
@@ -397,14 +406,17 @@ func makeImethodThunk(prog *Program, typ types.Type, id Id) *Function {
 		}
 		emitTailCall(fn, &c)
 		fn.finishBody()
+
+		prog.ifaceMethodWrappers[meth] = fn
+	}
 	return fn
 }
 
-// Thunks for bound methods ----------------------------------------
+// Wrappers for bound methods -------------------------------------------------
 
-// makeBoundMethodThunk returns a synthetic thunk function that
+// boundMethodWrapper returns a synthetic wrapper function that
-// delegates to a concrete method.  The thunk has one free variable,
+// delegates to a concrete method.  The wrapper has one free variable,
-// the method's receiver.  Use MakeClosure with such a thunk to
+// the method's receiver.  Use MakeClosure with such a wrapper to
 // construct a bound-method closure.
 // e.g.:
 //
@@ -414,24 +426,29 @@ func makeImethodThunk(prog *Program, typ types.Type, id Id) *Function {
 //   f := t.meth
 //   f() // calls t.meth()
 //
-// f is a closure of a synthetic thunk defined as if by:
+// f is a closure of a synthetic wrapper defined as if by:
 //
 //   f := func() { return t.meth() }
 //
-// TODO(adonovan): memoize creation of these functions in the Program.
+// EXCLUSIVE_LOCKS_ACQUIRED(meth.Prog.methodsMu)
 //
-func makeBoundMethodThunk(prog *Program, meth *Function, recvType types.Type) *Function {
+func boundMethodWrapper(meth *Function) *Function {
+	prog := meth.Prog
+	prog.methodsMu.Lock()
+	defer prog.methodsMu.Unlock()
+	fn, ok := prog.boundMethodWrappers[meth]
+	if !ok {
 		if prog.mode&LogSource != 0 {
-		defer logStack("makeBoundMethodThunk %s", meth)()
+			defer logStack("boundMethodWrapper %s", meth)()
 		}
 		s := meth.Signature
-	fn := &Function{
+		fn = &Function{
 			name:      "bound$" + meth.FullName(),
 			Signature: types.NewSignature(nil, s.Params(), s.Results(), s.IsVariadic()), // drop recv
 			Prog:      prog,
 		}
 
-	cap := &Capture{name: "recv", typ: recvType, parent: fn}
+		cap := &Capture{name: "recv", typ: s.Recv().Type(), parent: fn}
 		fn.FreeVars = []*Capture{cap}
 		fn.startBody()
 		createParams(fn)
@@ -443,6 +460,9 @@ func makeBoundMethodThunk(prog *Program, meth *Function, recvType types.Type) *F
 		}
 		emitTailCall(fn, &c)
 		fn.finishBody()
+
+		prog.boundMethodWrappers[meth] = fn
+	}
 	return fn
 }
 
@@ -455,7 +475,7 @@ func makeBoundMethodThunk(prog *Program, meth *Function, recvType types.Type) *F
 //              return (*recv).f(...)
 //      }
 //
-// EXCLUSIVE_LOCKS_REQUIRED(meth.Prog.methodSetsMu)
+// EXCLUSIVE_LOCKS_REQUIRED(meth.Prog.methodsMu)
 //
 func indirectionWrapper(meth *Function) *Function {
 	prog := meth.Prog

ssa/ssa.go

@@ -24,9 +24,11 @@ type Program struct {
 	concreteMethods map[*types.Func]*Function   // maps named concrete methods to their code
 	mode            BuilderMode                 // set of mode bits for SSA construction
 
-	methodSetsMu        sync.Mutex               // guards methodSets, indirectionWrappers
+	methodsMu           sync.Mutex                // guards the following maps:
-	methodSets          map[types.Type]MethodSet // concrete method sets for all needed types  [TODO(adonovan): de-dup]
+	methodSets          map[types.Type]MethodSet  // concrete method set each type [TODO(adonovan): de-dup]
 	indirectionWrappers map[*Function]*Function   // func(*T) wrappers for T-methods
+	boundMethodWrappers map[*Function]*Function   // wrappers for curried x.Method closures
+	ifaceMethodWrappers map[*types.Func]*Function // wrappers for curried I.Method functions
 }
 
 // A Package is a single analyzed Go package containing Members for

ssa/util.go

@@ -55,17 +55,31 @@ func pointer(typ types.Type) *types.Pointer {
 	return types.NewPointer(typ)
 }
 
-// methodIndex returns the method (and its index) named id within the
+// namedTypeMethodIndex returns the method (and its index) named id
-// method table of named or interface type typ.  If not found,
+// within the set of explicitly declared concrete methods of named
-// panic ensues.
+// type typ.  If not found, panic ensues.
 //
-func methodIndex(typ types.Type, id Id) (int, *types.Func) {
+// TODO(gri): move this functionality into the go/types API?
-	t := typ.(interface {
+//
-		NumMethods() int
+func namedTypeMethodIndex(typ *types.Named, id Id) (int, *types.Func) {
-		Method(i int) *types.Func
+	for i, n := 0, typ.NumMethods(); i < n; i++ {
-	})
+		m := typ.Method(i)
-	for i, n := 0, t.NumMethods(); i < n; i++ {
+		if MakeId(m.Name(), m.Pkg()) == id {
-		m := t.Method(i)
+			return i, m
+		}
+	}
+	panic(fmt.Sprint("method not found: ", id, " in named type ", typ))
+}
+
+// interfaceMethodIndex returns the method (and its index) named id
+// within the method-set of interface type typ.  If not found, panic
+// ensues.
+//
+// TODO(gri): move this functionality into the go/types API.
+//
+func interfaceMethodIndex(typ *types.Interface, id Id) (int, *types.Func) {
+	for i, n := 0, typ.NumMethods(); i < n; i++ {
+		m := typ.Method(i)
 		if MakeId(m.Name(), m.Pkg()) == id {
 			return i, m
 		}