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Copy pathbuilder.go
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2379 lines (2176 loc) · 62.3 KB
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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 implements the BUILD phase of SSA construction.
//
// 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 wrapper methods are synthesized.
// ssa.Packages are created in arbitrary order.
//
// In the BUILD phase (builder.go), the builder traverses the AST of
// each Go source function and generates SSA instructions for the
// function body. Initializer expressions for package-level variables
// are emitted to the package's init() function in the order specified
// by go/types.Info.InitOrder, then code for each function in the
// package is generated in lexical order.
// The BUILD phases for distinct packages are independent and are
// executed in parallel.
//
// TODO(adonovan): indeed, building functions is now embarrassingly parallel.
// Audit for concurrency then benchmark using more goroutines.
//
// The builder's and Program's indices (maps) are populated and
// mutated during the CREATE phase, but during the BUILD phase they
// remain constant. The sole exception is Prog.methodSets and its
// related maps, which are protected by a dedicated mutex.
import (
"fmt"
"go/ast"
"go/constant"
"go/token"
"go/types"
"os"
"sync"
)
type opaqueType struct {
types.Type
name string
}
func (t *opaqueType) String() string { return t.name }
var (
varOk = newVar("ok", tBool)
varIndex = newVar("index", tInt)
// Type constants.
tBool = types.Typ[types.Bool]
tByte = types.Typ[types.Byte]
tInt = types.Typ[types.Int]
tInvalid = types.Typ[types.Invalid]
tString = types.Typ[types.String]
tUntypedNil = types.Typ[types.UntypedNil]
tRangeIter = &opaqueType{nil, "iter"} // the type of all "range" iterators
tEface = types.NewInterfaceType(nil, nil).Complete()
// SSA Value constants.
vZero = intConst(0)
vOne = intConst(1)
vTrue = NewConst(constant.MakeBool(true), tBool)
)
// builder holds state associated with the package currently being built.
// Its methods contain all the logic for AST-to-SSA conversion.
type builder struct{}
// cond emits to fn code to evaluate boolean condition e and jump
// to t or f depending on its value, performing various simplifications.
//
// Postcondition: fn.currentBlock is nil.
//
func (b *builder) cond(fn *Function, e ast.Expr, t, f *BasicBlock) {
switch e := e.(type) {
case *ast.ParenExpr:
b.cond(fn, e.X, t, f)
return
case *ast.BinaryExpr:
switch e.Op {
case token.LAND:
ltrue := fn.newBasicBlock("cond.true")
b.cond(fn, e.X, ltrue, f)
fn.currentBlock = ltrue
b.cond(fn, e.Y, t, f)
return
case token.LOR:
lfalse := fn.newBasicBlock("cond.false")
b.cond(fn, e.X, t, lfalse)
fn.currentBlock = lfalse
b.cond(fn, e.Y, t, f)
return
}
case *ast.UnaryExpr:
if e.Op == token.NOT {
b.cond(fn, e.X, f, t)
return
}
}
// A traditional compiler would simplify "if false" (etc) here
// but we do not, for better fidelity to the source code.
//
// The value of a constant condition may be platform-specific,
// and may cause blocks that are reachable in some configuration
// to be hidden from subsequent analyses such as bug-finding tools.
emitIf(fn, b.expr(fn, e), t, f)
}
// logicalBinop emits code to fn to evaluate e, a &&- or
// ||-expression whose reified boolean value is wanted.
// The value is returned.
//
func (b *builder) logicalBinop(fn *Function, e *ast.BinaryExpr) Value {
rhs := fn.newBasicBlock("binop.rhs")
done := fn.newBasicBlock("binop.done")
// T(e) = T(e.X) = T(e.Y) after untyped constants have been
// eliminated.
// TODO(adonovan): not true; MyBool==MyBool yields UntypedBool.
t := fn.Pkg.typeOf(e)
var short Value // value of the short-circuit path
switch e.Op {
case token.LAND:
b.cond(fn, e.X, rhs, done)
short = NewConst(constant.MakeBool(false), t)
case token.LOR:
b.cond(fn, e.X, done, rhs)
short = NewConst(constant.MakeBool(true), t)
}
// Is rhs unreachable?
if rhs.Preds == nil {
// Simplify false&&y to false, true||y to true.
fn.currentBlock = done
return short
}
// Is done unreachable?
if done.Preds == nil {
// Simplify true&&y (or false||y) to y.
fn.currentBlock = rhs
return b.expr(fn, e.Y)
}
// All edges from e.X to done carry the short-circuit value.
var edges []Value
for range done.Preds {
edges = append(edges, short)
}
// The edge from e.Y to done carries the value of e.Y.
fn.currentBlock = rhs
edges = append(edges, b.expr(fn, e.Y))
emitJump(fn, done)
fn.currentBlock = done
phi := &Phi{Edges: edges, Comment: e.Op.String()}
phi.pos = e.OpPos
phi.typ = t
return done.emit(phi)
}
// exprN lowers a multi-result expression e to SSA form, emitting code
// to fn and returning a single Value whose type is a *types.Tuple.
// The caller must access the components via Extract.
//
// Multi-result expressions include CallExprs in a multi-value
// assignment or return statement, and "value,ok" uses of
// TypeAssertExpr, IndexExpr (when X is a map), and UnaryExpr (when Op
// is token.ARROW).
//
func (b *builder) exprN(fn *Function, e ast.Expr) Value {
typ := fn.Pkg.typeOf(e).(*types.Tuple)
switch e := e.(type) {
case *ast.ParenExpr:
return b.exprN(fn, e.X)
case *ast.CallExpr:
// Currently, no built-in function nor type conversion
// has multiple results, so we can avoid some of the
// cases for single-valued CallExpr.
var c Call
b.setCall(fn, e, &c.Call)
c.typ = typ
return fn.emit(&c)
case *ast.IndexExpr:
mapt := fn.Pkg.typeOf(e.X).Underlying().(*types.Map)
lookup := &Lookup{
X: b.expr(fn, e.X),
Index: emitConv(fn, b.expr(fn, e.Index), mapt.Key()),
CommaOk: true,
}
lookup.setType(typ)
lookup.setPos(e.Lbrack)
return fn.emit(lookup)
case *ast.TypeAssertExpr:
return emitTypeTest(fn, b.expr(fn, e.X), typ.At(0).Type(), e.Lparen)
case *ast.UnaryExpr: // must be receive <-
unop := &UnOp{
Op: token.ARROW,
X: b.expr(fn, e.X),
CommaOk: true,
}
unop.setType(typ)
unop.setPos(e.OpPos)
return fn.emit(unop)
}
panic(fmt.Sprintf("exprN(%T) in %s", e, fn))
}
// builtin emits to fn SSA instructions to implement a call to the
// built-in function obj with the specified arguments
// and return type. It returns the value defined by the result.
//
// The result is nil if no special handling was required; in this case
// the caller should treat this like an ordinary library function
// call.
//
func (b *builder) builtin(fn *Function, obj *types.Builtin, args []ast.Expr, typ types.Type, pos token.Pos) Value {
switch obj.Name() {
case "make":
switch typ.Underlying().(type) {
case *types.Slice:
n := b.expr(fn, args[1])
m := n
if len(args) == 3 {
m = b.expr(fn, args[2])
}
if m, ok := m.(*Const); ok {
// treat make([]T, n, m) as new([m]T)[:n]
cap := m.Int64()
at := types.NewArray(typ.Underlying().(*types.Slice).Elem(), cap)
alloc := emitNew(fn, at, pos)
alloc.Comment = "makeslice"
v := &Slice{
X: alloc,
High: n,
}
v.setPos(pos)
v.setType(typ)
return fn.emit(v)
}
v := &MakeSlice{
Len: n,
Cap: m,
}
v.setPos(pos)
v.setType(typ)
return fn.emit(v)
case *types.Map:
var res Value
if len(args) == 2 {
res = b.expr(fn, args[1])
}
v := &MakeMap{Reserve: res}
v.setPos(pos)
v.setType(typ)
return fn.emit(v)
case *types.Chan:
var sz Value = vZero
if len(args) == 2 {
sz = b.expr(fn, args[1])
}
v := &MakeChan{Size: sz}
v.setPos(pos)
v.setType(typ)
return fn.emit(v)
}
case "new":
alloc := emitNew(fn, deref(typ), pos)
alloc.Comment = "new"
return alloc
case "len", "cap":
// Special case: len or cap of an array or *array is
// based on the type, not the value which may be nil.
// We must still evaluate the value, though. (If it
// was side-effect free, the whole call would have
// been constant-folded.)
t := deref(fn.Pkg.typeOf(args[0])).Underlying()
if at, ok := t.(*types.Array); ok {
b.expr(fn, args[0]) // for effects only
return intConst(at.Len())
}
// Otherwise treat as normal.
case "panic":
fn.emit(&Panic{
X: emitConv(fn, b.expr(fn, args[0]), tEface),
pos: pos,
})
fn.currentBlock = fn.newBasicBlock("unreachable")
return vTrue // any non-nil Value will do
}
return nil // treat all others as a regular function call
}
// addr lowers a single-result addressable expression e to SSA form,
// emitting code to fn and returning the location (an lvalue) defined
// by the expression.
//
// If escaping is true, addr marks the base variable of the
// addressable expression e as being a potentially escaping pointer
// value. For example, in this code:
//
// a := A{
// b: [1]B{B{c: 1}}
// }
// return &a.b[0].c
//
// the application of & causes a.b[0].c to have its address taken,
// which means that ultimately the local variable a must be
// heap-allocated. This is a simple but very conservative escape
// analysis.
//
// Operations forming potentially escaping pointers include:
// - &x, including when implicit in method call or composite literals.
// - a[:] iff a is an array (not *array)
// - references to variables in lexically enclosing functions.
//
func (b *builder) addr(fn *Function, e ast.Expr, escaping bool) lvalue {
switch e := e.(type) {
case *ast.Ident:
if isBlankIdent(e) {
return blank{}
}
obj := fn.Pkg.objectOf(e)
v := fn.Prog.packageLevelValue(obj) // var (address)
if v == nil {
v = fn.lookup(obj, escaping)
}
return &address{addr: v, pos: e.Pos(), expr: e}
case *ast.CompositeLit:
t := deref(fn.Pkg.typeOf(e))
var v *Alloc
if escaping {
v = emitNew(fn, t, e.Lbrace)
} else {
v = fn.addLocal(t, e.Lbrace)
}
v.Comment = "complit"
var sb storebuf
b.compLit(fn, v, e, true, &sb)
sb.emit(fn)
return &address{addr: v, pos: e.Lbrace, expr: e}
case *ast.ParenExpr:
return b.addr(fn, e.X, escaping)
case *ast.SelectorExpr:
sel, ok := fn.Pkg.info.Selections[e]
if !ok {
// qualified identifier
return b.addr(fn, e.Sel, escaping)
}
if sel.Kind() != types.FieldVal {
panic(sel)
}
wantAddr := true
v := b.receiver(fn, e.X, wantAddr, escaping, sel)
last := len(sel.Index()) - 1
return &address{
addr: emitFieldSelection(fn, v, sel.Index()[last], true, e.Sel),
pos: e.Sel.Pos(),
expr: e.Sel,
}
case *ast.IndexExpr:
var x Value
var et types.Type
switch t := fn.Pkg.typeOf(e.X).Underlying().(type) {
case *types.Array:
x = b.addr(fn, e.X, escaping).address(fn)
et = types.NewPointer(t.Elem())
case *types.Pointer: // *array
x = b.expr(fn, e.X)
et = types.NewPointer(t.Elem().Underlying().(*types.Array).Elem())
case *types.Slice:
x = b.expr(fn, e.X)
et = types.NewPointer(t.Elem())
case *types.Map:
return &element{
m: b.expr(fn, e.X),
k: emitConv(fn, b.expr(fn, e.Index), t.Key()),
t: t.Elem(),
pos: e.Lbrack,
}
default:
panic("unexpected container type in IndexExpr: " + t.String())
}
v := &IndexAddr{
X: x,
Index: emitConv(fn, b.expr(fn, e.Index), tInt),
}
v.setPos(e.Lbrack)
v.setType(et)
return &address{addr: fn.emit(v), pos: e.Lbrack, expr: e}
case *ast.StarExpr:
return &address{addr: b.expr(fn, e.X), pos: e.Star, expr: e}
}
panic(fmt.Sprintf("unexpected address expression: %T", e))
}
type store struct {
lhs lvalue
rhs Value
}
type storebuf struct{ stores []store }
func (sb *storebuf) store(lhs lvalue, rhs Value) {
sb.stores = append(sb.stores, store{lhs, rhs})
}
func (sb *storebuf) emit(fn *Function) {
for _, s := range sb.stores {
s.lhs.store(fn, s.rhs)
}
}
// assign emits to fn code to initialize the lvalue loc with the value
// of expression e. If isZero is true, assign assumes that loc holds
// the zero value for its type.
//
// This is equivalent to loc.store(fn, b.expr(fn, e)), but may generate
// better code in some cases, e.g., for composite literals in an
// addressable location.
//
// If sb is not nil, assign generates code to evaluate expression e, but
// not to update loc. Instead, the necessary stores are appended to the
// storebuf sb so that they can be executed later. This allows correct
// in-place update of existing variables when the RHS is a composite
// literal that may reference parts of the LHS.
//
func (b *builder) assign(fn *Function, loc lvalue, e ast.Expr, isZero bool, sb *storebuf) {
// Can we initialize it in place?
if e, ok := unparen(e).(*ast.CompositeLit); ok {
// A CompositeLit never evaluates to a pointer,
// so if the type of the location is a pointer,
// an &-operation is implied.
if _, ok := loc.(blank); !ok { // avoid calling blank.typ()
if isPointer(loc.typ()) {
ptr := b.addr(fn, e, true).address(fn)
// copy address
if sb != nil {
sb.store(loc, ptr)
} else {
loc.store(fn, ptr)
}
return
}
}
if _, ok := loc.(*address); ok {
if isInterface(loc.typ()) {
// e.g. var x interface{} = T{...}
// Can't in-place initialize an interface value.
// Fall back to copying.
} else {
// x = T{...} or x := T{...}
addr := loc.address(fn)
if sb != nil {
b.compLit(fn, addr, e, isZero, sb)
} else {
var sb storebuf
b.compLit(fn, addr, e, isZero, &sb)
sb.emit(fn)
}
// Subtle: emit debug ref for aggregate types only;
// slice and map are handled by store ops in compLit.
switch loc.typ().Underlying().(type) {
case *types.Struct, *types.Array:
emitDebugRef(fn, e, addr, true)
}
return
}
}
}
// simple case: just copy
rhs := b.expr(fn, e)
if sb != nil {
sb.store(loc, rhs)
} else {
loc.store(fn, rhs)
}
}
// expr lowers a single-result expression e to SSA form, emitting code
// to fn and returning the Value defined by the expression.
//
func (b *builder) expr(fn *Function, e ast.Expr) Value {
e = unparen(e)
tv := fn.Pkg.info.Types[e]
// Is expression a constant?
if tv.Value != nil {
return NewConst(tv.Value, tv.Type)
}
var v Value
if tv.Addressable() {
// Prefer pointer arithmetic ({Index,Field}Addr) followed
// by Load over subelement extraction (e.g. Index, Field),
// to avoid large copies.
v = b.addr(fn, e, false).load(fn)
} else {
v = b.expr0(fn, e, tv)
}
if fn.debugInfo() {
emitDebugRef(fn, e, v, false)
}
return v
}
func (b *builder) expr0(fn *Function, e ast.Expr, tv types.TypeAndValue) Value {
switch e := e.(type) {
case *ast.BasicLit:
panic("non-constant BasicLit") // unreachable
case *ast.FuncLit:
fn2 := &Function{
name: fmt.Sprintf("%s$%d", fn.Name(), 1+len(fn.AnonFuncs)),
Signature: fn.Pkg.typeOf(e.Type).Underlying().(*types.Signature),
pos: e.Type.Func,
parent: fn,
Pkg: fn.Pkg,
Prog: fn.Prog,
syntax: e,
}
fn.AnonFuncs = append(fn.AnonFuncs, fn2)
b.buildFunction(fn2)
if fn2.FreeVars == nil {
return fn2
}
v := &MakeClosure{Fn: fn2}
v.setType(tv.Type)
for _, fv := range fn2.FreeVars {
v.Bindings = append(v.Bindings, fv.outer)
fv.outer = nil
}
return fn.emit(v)
case *ast.TypeAssertExpr: // single-result form only
return emitTypeAssert(fn, b.expr(fn, e.X), tv.Type, e.Lparen)
case *ast.CallExpr:
if fn.Pkg.info.Types[e.Fun].IsType() {
// Explicit type conversion, e.g. string(x) or big.Int(x)
x := b.expr(fn, e.Args[0])
y := emitConv(fn, x, tv.Type)
if y != x {
switch y := y.(type) {
case *Convert:
y.pos = e.Lparen
case *ChangeType:
y.pos = e.Lparen
case *MakeInterface:
y.pos = e.Lparen
}
}
return y
}
// Call to "intrinsic" built-ins, e.g. new, make, panic.
if id, ok := unparen(e.Fun).(*ast.Ident); ok {
if obj, ok := fn.Pkg.info.Uses[id].(*types.Builtin); ok {
if v := b.builtin(fn, obj, e.Args, tv.Type, e.Lparen); v != nil {
return v
}
}
}
// Regular function call.
var v Call
b.setCall(fn, e, &v.Call)
v.setType(tv.Type)
return fn.emit(&v)
case *ast.UnaryExpr:
switch e.Op {
case token.AND: // &X --- potentially escaping.
addr := b.addr(fn, e.X, true)
if _, ok := unparen(e.X).(*ast.StarExpr); ok {
// &*p must panic if p is nil (http://golang.org/s/go12nil).
// For simplicity, we'll just (suboptimally) rely
// on the side effects of a load.
// TODO(adonovan): emit dedicated nilcheck.
addr.load(fn)
}
return addr.address(fn)
case token.ADD:
return b.expr(fn, e.X)
case token.NOT, token.ARROW, token.SUB, token.XOR: // ! <- - ^
v := &UnOp{
Op: e.Op,
X: b.expr(fn, e.X),
}
v.setPos(e.OpPos)
v.setType(tv.Type)
return fn.emit(v)
default:
panic(e.Op)
}
case *ast.BinaryExpr:
switch e.Op {
case token.LAND, token.LOR:
return b.logicalBinop(fn, e)
case token.SHL, token.SHR:
fallthrough
case token.ADD, token.SUB, token.MUL, token.QUO, token.REM, token.AND, token.OR, token.XOR, token.AND_NOT:
return emitArith(fn, e.Op, b.expr(fn, e.X), b.expr(fn, e.Y), tv.Type, e.OpPos)
case token.EQL, token.NEQ, token.GTR, token.LSS, token.LEQ, token.GEQ:
cmp := emitCompare(fn, e.Op, b.expr(fn, e.X), b.expr(fn, e.Y), e.OpPos)
// The type of x==y may be UntypedBool.
return emitConv(fn, cmp, DefaultType(tv.Type))
default:
panic("illegal op in BinaryExpr: " + e.Op.String())
}
case *ast.SliceExpr:
var low, high, max Value
var x Value
switch fn.Pkg.typeOf(e.X).Underlying().(type) {
case *types.Array:
// Potentially escaping.
x = b.addr(fn, e.X, true).address(fn)
case *types.Basic, *types.Slice, *types.Pointer: // *array
x = b.expr(fn, e.X)
default:
panic("unreachable")
}
if e.High != nil {
high = b.expr(fn, e.High)
}
if e.Low != nil {
low = b.expr(fn, e.Low)
}
if e.Slice3 {
max = b.expr(fn, e.Max)
}
v := &Slice{
X: x,
Low: low,
High: high,
Max: max,
}
v.setPos(e.Lbrack)
v.setType(tv.Type)
return fn.emit(v)
case *ast.Ident:
obj := fn.Pkg.info.Uses[e]
// Universal built-in or nil?
switch obj := obj.(type) {
case *types.Builtin:
return &Builtin{name: obj.Name(), sig: tv.Type.(*types.Signature)}
case *types.Nil:
return nilConst(tv.Type)
}
// Package-level func or var?
if v := fn.Prog.packageLevelValue(obj); v != nil {
if _, ok := obj.(*types.Var); ok {
return emitLoad(fn, v) // var (address)
}
return v // (func)
}
// Local var.
return emitLoad(fn, fn.lookup(obj, false)) // var (address)
case *ast.SelectorExpr:
sel, ok := fn.Pkg.info.Selections[e]
if !ok {
// qualified identifier
return b.expr(fn, e.Sel)
}
switch sel.Kind() {
case types.MethodExpr:
// (*T).f or T.f, the method f from the method-set of type T.
// The result is a "thunk".
return emitConv(fn, makeThunk(fn.Prog, sel), tv.Type)
case types.MethodVal:
// e.f where e is an expression and f is a method.
// The result is a "bound".
obj := sel.Obj().(*types.Func)
rt := recvType(obj)
wantAddr := isPointer(rt)
escaping := true
v := b.receiver(fn, e.X, wantAddr, escaping, sel)
if isInterface(rt) {
// If v has interface type I,
// we must emit a check that v is non-nil.
// We use: typeassert v.(I).
emitTypeAssert(fn, v, rt, token.NoPos)
}
c := &MakeClosure{
Fn: makeBound(fn.Prog, obj),
Bindings: []Value{v},
}
c.setPos(e.Sel.Pos())
c.setType(tv.Type)
return fn.emit(c)
case types.FieldVal:
indices := sel.Index()
last := len(indices) - 1
v := b.expr(fn, e.X)
v = emitImplicitSelections(fn, v, indices[:last])
v = emitFieldSelection(fn, v, indices[last], false, e.Sel)
return v
}
panic("unexpected expression-relative selector")
case *ast.IndexExpr:
switch t := fn.Pkg.typeOf(e.X).Underlying().(type) {
case *types.Array:
// Non-addressable array (in a register).
v := &Index{
X: b.expr(fn, e.X),
Index: emitConv(fn, b.expr(fn, e.Index), tInt),
}
v.setPos(e.Lbrack)
v.setType(t.Elem())
return fn.emit(v)
case *types.Map:
// Maps are not addressable.
mapt := fn.Pkg.typeOf(e.X).Underlying().(*types.Map)
v := &Lookup{
X: b.expr(fn, e.X),
Index: emitConv(fn, b.expr(fn, e.Index), mapt.Key()),
}
v.setPos(e.Lbrack)
v.setType(mapt.Elem())
return fn.emit(v)
case *types.Basic: // => string
// Strings are not addressable.
v := &Lookup{
X: b.expr(fn, e.X),
Index: b.expr(fn, e.Index),
}
v.setPos(e.Lbrack)
v.setType(tByte)
return fn.emit(v)
case *types.Slice, *types.Pointer: // *array
// Addressable slice/array; use IndexAddr and Load.
return b.addr(fn, e, false).load(fn)
default:
panic("unexpected container type in IndexExpr: " + t.String())
}
case *ast.CompositeLit, *ast.StarExpr:
// Addressable types (lvalues)
return b.addr(fn, e, false).load(fn)
}
panic(fmt.Sprintf("unexpected expr: %T", e))
}
// stmtList emits to fn code for all statements in list.
func (b *builder) stmtList(fn *Function, list []ast.Stmt) {
for _, s := range list {
b.stmt(fn, s)
}
}
// receiver emits to fn code for expression e in the "receiver"
// position of selection e.f (where f may be a field or a method) and
// returns the effective receiver after applying the implicit field
// selections of sel.
//
// wantAddr requests that the result is an an address. If
// !sel.Indirect(), this may require that e be built in addr() mode; it
// must thus be addressable.
//
// escaping is defined as per builder.addr().
//
func (b *builder) receiver(fn *Function, e ast.Expr, wantAddr, escaping bool, sel *types.Selection) Value {
var v Value
if wantAddr && !sel.Indirect() && !isPointer(fn.Pkg.typeOf(e)) {
v = b.addr(fn, e, escaping).address(fn)
} else {
v = b.expr(fn, e)
}
last := len(sel.Index()) - 1
v = emitImplicitSelections(fn, v, sel.Index()[:last])
if !wantAddr && isPointer(v.Type()) {
v = emitLoad(fn, v)
}
return v
}
// setCallFunc populates the function parts of a CallCommon structure
// (Func, Method, Recv, Args[0]) based on the kind of invocation
// occurring in e.
//
func (b *builder) setCallFunc(fn *Function, e *ast.CallExpr, c *CallCommon) {
c.pos = e.Lparen
// Is this a method call?
if selector, ok := unparen(e.Fun).(*ast.SelectorExpr); ok {
sel, ok := fn.Pkg.info.Selections[selector]
if ok && sel.Kind() == types.MethodVal {
obj := sel.Obj().(*types.Func)
recv := recvType(obj)
wantAddr := isPointer(recv)
escaping := true
v := b.receiver(fn, selector.X, wantAddr, escaping, sel)
if isInterface(recv) {
// Invoke-mode call.
c.Value = v
c.Method = obj
} else {
// "Call"-mode call.
c.Value = fn.Prog.declaredFunc(obj)
c.Args = append(c.Args, v)
}
return
}
// sel.Kind()==MethodExpr indicates T.f() or (*T).f():
// a statically dispatched call to the method f in the
// method-set of T or *T. T may be an interface.
//
// e.Fun would evaluate to a concrete method, interface
// wrapper function, or promotion wrapper.
//
// For now, we evaluate it in the usual way.
//
// TODO(adonovan): opt: inline expr() here, to make the
// call static and to avoid generation of wrappers.
// It's somewhat tricky as it may consume the first
// actual parameter if the call is "invoke" mode.
//
// Examples:
// type T struct{}; func (T) f() {} // "call" mode
// type T interface { f() } // "invoke" mode
//
// type S struct{ T }
//
// var s S
// S.f(s)
// (*S).f(&s)
//
// Suggested approach:
// - consume the first actual parameter expression
// and build it with b.expr().
// - apply implicit field selections.
// - use MethodVal logic to populate fields of c.
}
// Evaluate the function operand in the usual way.
c.Value = b.expr(fn, e.Fun)
}
// emitCallArgs emits to f code for the actual parameters of call e to
// a (possibly built-in) function of effective type sig.
// The argument values are appended to args, which is then returned.
//
func (b *builder) emitCallArgs(fn *Function, sig *types.Signature, e *ast.CallExpr, args []Value) []Value {
// f(x, y, z...): pass slice z straight through.
if e.Ellipsis != 0 {
for i, arg := range e.Args {
v := emitConv(fn, b.expr(fn, arg), sig.Params().At(i).Type())
args = append(args, v)
}
return args
}
offset := len(args) // 1 if call has receiver, 0 otherwise
// Evaluate actual parameter expressions.
//
// If this is a chained call of the form f(g()) where g has
// multiple return values (MRV), they are flattened out into
// args; a suffix of them may end up in a varargs slice.
for _, arg := range e.Args {
v := b.expr(fn, arg)
if ttuple, ok := v.Type().(*types.Tuple); ok { // MRV chain
for i, n := 0, ttuple.Len(); i < n; i++ {
args = append(args, emitExtract(fn, v, i))
}
} else {
args = append(args, v)
}
}
// Actual->formal assignability conversions for normal parameters.
np := sig.Params().Len() // number of normal parameters
if sig.Variadic() {
np--
}
for i := 0; i < np; i++ {
args[offset+i] = emitConv(fn, args[offset+i], sig.Params().At(i).Type())
}
// Actual->formal assignability conversions for variadic parameter,
// and construction of slice.
if sig.Variadic() {
varargs := args[offset+np:]
st := sig.Params().At(np).Type().(*types.Slice)
vt := st.Elem()
if len(varargs) == 0 {
args = append(args, nilConst(st))
} else {
// Replace a suffix of args with a slice containing it.
at := types.NewArray(vt, int64(len(varargs)))
a := emitNew(fn, at, token.NoPos)
a.setPos(e.Rparen)
a.Comment = "varargs"
for i, arg := range varargs {
iaddr := &IndexAddr{
X: a,
Index: intConst(int64(i)),
}
iaddr.setType(types.NewPointer(vt))
fn.emit(iaddr)
emitStore(fn, iaddr, arg, arg.Pos())
}
s := &Slice{X: a}
s.setType(st)
args[offset+np] = fn.emit(s)
args = args[:offset+np+1]
}
}
return args
}
// setCall emits to fn code to evaluate all the parameters of a function
// call e, and populates *c with those values.
//
func (b *builder) setCall(fn *Function, e *ast.CallExpr, c *CallCommon) {
// First deal with the f(...) part and optional receiver.
b.setCallFunc(fn, e, c)
// Then append the other actual parameters.
sig, _ := fn.Pkg.typeOf(e.Fun).Underlying().(*types.Signature)
if sig == nil {
panic(fmt.Sprintf("no signature for call of %s", e.Fun))
}
c.Args = b.emitCallArgs(fn, sig, e, c.Args)
}
// assignOp emits to fn code to perform loc <op>= val.
func (b *builder) assignOp(fn *Function, loc lvalue, val Value, op token.Token, pos token.Pos) {
oldv := loc.load(fn)
loc.store(fn, emitArith(fn, op, oldv, emitConv(fn, val, oldv.Type()), loc.typ(), pos))
}
// localValueSpec emits to fn code to define all of the vars in the
// function-local ValueSpec, spec.
//
func (b *builder) localValueSpec(fn *Function, spec *ast.ValueSpec) {
switch {
case len(spec.Values) == len(spec.Names):
// e.g. var x, y = 0, 1
// 1:1 assignment
for i, id := range spec.Names {
if !isBlankIdent(id) {
fn.addLocalForIdent(id)
}
lval := b.addr(fn, id, false) // non-escaping
b.assign(fn, lval, spec.Values[i], true, nil)
}
case len(spec.Values) == 0:
// e.g. var x, y int
// Locals are implicitly zero-initialized.
for _, id := range spec.Names {
if !isBlankIdent(id) {
lhs := fn.addLocalForIdent(id)
if fn.debugInfo() {