--- /dev/null
+// 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.NewInterface(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, types.Default(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() {
+ emitDebugRef(fn, id, lhs, true)
+ }
+ }
+ }
+
+ default:
+ // e.g. var x, y = pos()
+ tuple := b.exprN(fn, spec.Values[0])
+ for i, id := range spec.Names {
+ if !isBlankIdent(id) {
+ fn.addLocalForIdent(id)
+ lhs := b.addr(fn, id, false) // non-escaping
+ lhs.store(fn, emitExtract(fn, tuple, i))
+ }
+ }
+ }
+}
+
+// assignStmt emits code to fn for a parallel assignment of rhss to lhss.
+// isDef is true if this is a short variable declaration (:=).
+//
+// Note the similarity with localValueSpec.
+//
+func (b *builder) assignStmt(fn *Function, lhss, rhss []ast.Expr, isDef bool) {
+ // Side effects of all LHSs and RHSs must occur in left-to-right order.
+ lvals := make([]lvalue, len(lhss))
+ isZero := make([]bool, len(lhss))
+ for i, lhs := range lhss {
+ var lval lvalue = blank{}
+ if !isBlankIdent(lhs) {
+ if isDef {
+ if obj := fn.Pkg.info.Defs[lhs.(*ast.Ident)]; obj != nil {
+ fn.addNamedLocal(obj)
+ isZero[i] = true
+ }
+ }
+ lval = b.addr(fn, lhs, false) // non-escaping
+ }
+ lvals[i] = lval
+ }
+ if len(lhss) == len(rhss) {
+ // Simple assignment: x = f() (!isDef)
+ // Parallel assignment: x, y = f(), g() (!isDef)
+ // or short var decl: x, y := f(), g() (isDef)
+ //
+ // In all cases, the RHSs may refer to the LHSs,
+ // so we need a storebuf.
+ var sb storebuf
+ for i := range rhss {
+ b.assign(fn, lvals[i], rhss[i], isZero[i], &sb)
+ }
+ sb.emit(fn)
+ } else {
+ // e.g. x, y = pos()
+ tuple := b.exprN(fn, rhss[0])
+ emitDebugRef(fn, rhss[0], tuple, false)
+ for i, lval := range lvals {
+ lval.store(fn, emitExtract(fn, tuple, i))
+ }
+ }
+}
+
+// arrayLen returns the length of the array whose composite literal elements are elts.
+func (b *builder) arrayLen(fn *Function, elts []ast.Expr) int64 {
+ var max int64 = -1
+ var i int64 = -1
+ for _, e := range elts {
+ if kv, ok := e.(*ast.KeyValueExpr); ok {
+ i = b.expr(fn, kv.Key).(*Const).Int64()
+ } else {
+ i++
+ }
+ if i > max {
+ max = i
+ }
+ }
+ return max + 1
+}
+
+// compLit emits to fn code to initialize a composite literal e at
+// address addr with type typ.
+//
+// Nested composite literals are recursively initialized in place
+// where possible. If isZero is true, compLit assumes that addr
+// holds the zero value for typ.
+//
+// Because the elements of a composite literal may refer to the
+// variables being updated, as in the second line below,
+// x := T{a: 1}
+// x = T{a: x.a}
+// all the reads must occur before all the writes. Thus all stores to
+// loc are emitted to the storebuf sb for later execution.
+//
+// A CompositeLit may have pointer type only in the recursive (nested)
+// case when the type name is implicit. e.g. in []*T{{}}, the inner
+// literal has type *T behaves like &T{}.
+// In that case, addr must hold a T, not a *T.
+//
+func (b *builder) compLit(fn *Function, addr Value, e *ast.CompositeLit, isZero bool, sb *storebuf) {
+ typ := deref(fn.Pkg.typeOf(e))
+ switch t := typ.Underlying().(type) {
+ case *types.Struct:
+ if !isZero && len(e.Elts) != t.NumFields() {
+ // memclear
+ sb.store(&address{addr, e.Lbrace, nil},
+ zeroValue(fn, deref(addr.Type())))
+ isZero = true
+ }
+ for i, e := range e.Elts {
+ fieldIndex := i
+ pos := e.Pos()
+ if kv, ok := e.(*ast.KeyValueExpr); ok {
+ fname := kv.Key.(*ast.Ident).Name
+ for i, n := 0, t.NumFields(); i < n; i++ {
+ sf := t.Field(i)
+ if sf.Name() == fname {
+ fieldIndex = i
+ pos = kv.Colon
+ e = kv.Value
+ break
+ }
+ }
+ }
+ sf := t.Field(fieldIndex)
+ faddr := &FieldAddr{
+ X: addr,
+ Field: fieldIndex,
+ }
+ faddr.setType(types.NewPointer(sf.Type()))
+ fn.emit(faddr)
+ b.assign(fn, &address{addr: faddr, pos: pos, expr: e}, e, isZero, sb)
+ }
+
+ case *types.Array, *types.Slice:
+ var at *types.Array
+ var array Value
+ switch t := t.(type) {
+ case *types.Slice:
+ at = types.NewArray(t.Elem(), b.arrayLen(fn, e.Elts))
+ alloc := emitNew(fn, at, e.Lbrace)
+ alloc.Comment = "slicelit"
+ array = alloc
+ case *types.Array:
+ at = t
+ array = addr
+
+ if !isZero && int64(len(e.Elts)) != at.Len() {
+ // memclear
+ sb.store(&address{array, e.Lbrace, nil},
+ zeroValue(fn, deref(array.Type())))
+ }
+ }
+
+ var idx *Const
+ for _, e := range e.Elts {
+ pos := e.Pos()
+ if kv, ok := e.(*ast.KeyValueExpr); ok {
+ idx = b.expr(fn, kv.Key).(*Const)
+ pos = kv.Colon
+ e = kv.Value
+ } else {
+ var idxval int64
+ if idx != nil {
+ idxval = idx.Int64() + 1
+ }
+ idx = intConst(idxval)
+ }
+ iaddr := &IndexAddr{
+ X: array,
+ Index: idx,
+ }
+ iaddr.setType(types.NewPointer(at.Elem()))
+ fn.emit(iaddr)
+ if t != at { // slice
+ // backing array is unaliased => storebuf not needed.
+ b.assign(fn, &address{addr: iaddr, pos: pos, expr: e}, e, true, nil)
+ } else {
+ b.assign(fn, &address{addr: iaddr, pos: pos, expr: e}, e, true, sb)
+ }
+ }
+
+ if t != at { // slice
+ s := &Slice{X: array}
+ s.setPos(e.Lbrace)
+ s.setType(typ)
+ sb.store(&address{addr: addr, pos: e.Lbrace, expr: e}, fn.emit(s))
+ }
+
+ case *types.Map:
+ m := &MakeMap{Reserve: intConst(int64(len(e.Elts)))}
+ m.setPos(e.Lbrace)
+ m.setType(typ)
+ fn.emit(m)
+ for _, e := range e.Elts {
+ e := e.(*ast.KeyValueExpr)
+
+ // If a key expression in a map literal is itself a
+ // composite literal, the type may be omitted.
+ // For example:
+ // map[*struct{}]bool{{}: true}
+ // An &-operation may be implied:
+ // map[*struct{}]bool{&struct{}{}: true}
+ var key Value
+ if _, ok := unparen(e.Key).(*ast.CompositeLit); ok && isPointer(t.Key()) {
+ // A CompositeLit never evaluates to a pointer,
+ // so if the type of the location is a pointer,
+ // an &-operation is implied.
+ key = b.addr(fn, e.Key, true).address(fn)
+ } else {
+ key = b.expr(fn, e.Key)
+ }
+
+ loc := element{
+ m: m,
+ k: emitConv(fn, key, t.Key()),
+ t: t.Elem(),
+ pos: e.Colon,
+ }
+
+ // We call assign() only because it takes care
+ // of any &-operation required in the recursive
+ // case, e.g.,
+ // map[int]*struct{}{0: {}} implies &struct{}{}.
+ // In-place update is of course impossible,
+ // and no storebuf is needed.
+ b.assign(fn, &loc, e.Value, true, nil)
+ }
+ sb.store(&address{addr: addr, pos: e.Lbrace, expr: e}, m)
+
+ default:
+ panic("unexpected CompositeLit type: " + t.String())
+ }
+}
+
+// switchStmt emits to fn code for the switch statement s, optionally
+// labelled by label.
+//
+func (b *builder) switchStmt(fn *Function, s *ast.SwitchStmt, label *lblock) {
+ // We treat SwitchStmt like a sequential if-else chain.
+ // Multiway dispatch can be recovered later by ssautil.Switches()
+ // to those cases that are free of side effects.
+ if s.Init != nil {
+ b.stmt(fn, s.Init)
+ }
+ var tag Value = vTrue
+ if s.Tag != nil {
+ tag = b.expr(fn, s.Tag)
+ }
+ done := fn.newBasicBlock("switch.done")
+ if label != nil {
+ label._break = done
+ }
+ // We pull the default case (if present) down to the end.
+ // But each fallthrough label must point to the next
+ // body block in source order, so we preallocate a
+ // body block (fallthru) for the next case.
+ // Unfortunately this makes for a confusing block order.
+ var dfltBody *[]ast.Stmt
+ var dfltFallthrough *BasicBlock
+ var fallthru, dfltBlock *BasicBlock
+ ncases := len(s.Body.List)
+ for i, clause := range s.Body.List {
+ body := fallthru
+ if body == nil {
+ body = fn.newBasicBlock("switch.body") // first case only
+ }
+
+ // Preallocate body block for the next case.
+ fallthru = done
+ if i+1 < ncases {
+ fallthru = fn.newBasicBlock("switch.body")
+ }
+
+ cc := clause.(*ast.CaseClause)
+ if cc.List == nil {
+ // Default case.
+ dfltBody = &cc.Body
+ dfltFallthrough = fallthru
+ dfltBlock = body
+ continue
+ }
+
+ var nextCond *BasicBlock
+ for _, cond := range cc.List {
+ nextCond = fn.newBasicBlock("switch.next")
+ // TODO(adonovan): opt: when tag==vTrue, we'd
+ // get better code if we use b.cond(cond)
+ // instead of BinOp(EQL, tag, b.expr(cond))
+ // followed by If. Don't forget conversions
+ // though.
+ cond := emitCompare(fn, token.EQL, tag, b.expr(fn, cond), token.NoPos)
+ emitIf(fn, cond, body, nextCond)
+ fn.currentBlock = nextCond
+ }
+ fn.currentBlock = body
+ fn.targets = &targets{
+ tail: fn.targets,
+ _break: done,
+ _fallthrough: fallthru,
+ }
+ b.stmtList(fn, cc.Body)
+ fn.targets = fn.targets.tail
+ emitJump(fn, done)
+ fn.currentBlock = nextCond
+ }
+ if dfltBlock != nil {
+ emitJump(fn, dfltBlock)
+ fn.currentBlock = dfltBlock
+ fn.targets = &targets{
+ tail: fn.targets,
+ _break: done,
+ _fallthrough: dfltFallthrough,
+ }
+ b.stmtList(fn, *dfltBody)
+ fn.targets = fn.targets.tail
+ }
+ emitJump(fn, done)
+ fn.currentBlock = done
+}
+
+// typeSwitchStmt emits to fn code for the type switch statement s, optionally
+// labelled by label.
+//
+func (b *builder) typeSwitchStmt(fn *Function, s *ast.TypeSwitchStmt, label *lblock) {
+ // We treat TypeSwitchStmt like a sequential if-else chain.
+ // Multiway dispatch can be recovered later by ssautil.Switches().
+
+ // Typeswitch lowering:
+ //
+ // var x X
+ // switch y := x.(type) {
+ // case T1, T2: S1 // >1 (y := x)
+ // case nil: SN // nil (y := x)
+ // default: SD // 0 types (y := x)
+ // case T3: S3 // 1 type (y := x.(T3))
+ // }
+ //
+ // ...s.Init...
+ // x := eval x
+ // .caseT1:
+ // t1, ok1 := typeswitch,ok x <T1>
+ // if ok1 then goto S1 else goto .caseT2
+ // .caseT2:
+ // t2, ok2 := typeswitch,ok x <T2>
+ // if ok2 then goto S1 else goto .caseNil
+ // .S1:
+ // y := x
+ // ...S1...
+ // goto done
+ // .caseNil:
+ // if t2, ok2 := typeswitch,ok x <T2>
+ // if x == nil then goto SN else goto .caseT3
+ // .SN:
+ // y := x
+ // ...SN...
+ // goto done
+ // .caseT3:
+ // t3, ok3 := typeswitch,ok x <T3>
+ // if ok3 then goto S3 else goto default
+ // .S3:
+ // y := t3
+ // ...S3...
+ // goto done
+ // .default:
+ // y := x
+ // ...SD...
+ // goto done
+ // .done:
+
+ if s.Init != nil {
+ b.stmt(fn, s.Init)
+ }
+
+ var x Value
+ switch ass := s.Assign.(type) {
+ case *ast.ExprStmt: // x.(type)
+ x = b.expr(fn, unparen(ass.X).(*ast.TypeAssertExpr).X)
+ case *ast.AssignStmt: // y := x.(type)
+ x = b.expr(fn, unparen(ass.Rhs[0]).(*ast.TypeAssertExpr).X)
+ }
+
+ done := fn.newBasicBlock("typeswitch.done")
+ if label != nil {
+ label._break = done
+ }
+ var default_ *ast.CaseClause
+ for _, clause := range s.Body.List {
+ cc := clause.(*ast.CaseClause)
+ if cc.List == nil {
+ default_ = cc
+ continue
+ }
+ body := fn.newBasicBlock("typeswitch.body")
+ var next *BasicBlock
+ var casetype types.Type
+ var ti Value // ti, ok := typeassert,ok x <Ti>
+ for _, cond := range cc.List {
+ next = fn.newBasicBlock("typeswitch.next")
+ casetype = fn.Pkg.typeOf(cond)
+ var condv Value
+ if casetype == tUntypedNil {
+ condv = emitCompare(fn, token.EQL, x, nilConst(x.Type()), token.NoPos)
+ ti = x
+ } else {
+ yok := emitTypeTest(fn, x, casetype, cc.Case)
+ ti = emitExtract(fn, yok, 0)
+ condv = emitExtract(fn, yok, 1)
+ }
+ emitIf(fn, condv, body, next)
+ fn.currentBlock = next
+ }
+ if len(cc.List) != 1 {
+ ti = x
+ }
+ fn.currentBlock = body
+ b.typeCaseBody(fn, cc, ti, done)
+ fn.currentBlock = next
+ }
+ if default_ != nil {
+ b.typeCaseBody(fn, default_, x, done)
+ } else {
+ emitJump(fn, done)
+ }
+ fn.currentBlock = done
+}
+
+func (b *builder) typeCaseBody(fn *Function, cc *ast.CaseClause, x Value, done *BasicBlock) {
+ if obj := fn.Pkg.info.Implicits[cc]; obj != nil {
+ // In a switch y := x.(type), each case clause
+ // implicitly declares a distinct object y.
+ // In a single-type case, y has that type.
+ // In multi-type cases, 'case nil' and default,
+ // y has the same type as the interface operand.
+ emitStore(fn, fn.addNamedLocal(obj), x, obj.Pos())
+ }
+ fn.targets = &targets{
+ tail: fn.targets,
+ _break: done,
+ }
+ b.stmtList(fn, cc.Body)
+ fn.targets = fn.targets.tail
+ emitJump(fn, done)
+}
+
+// selectStmt emits to fn code for the select statement s, optionally
+// labelled by label.
+//
+func (b *builder) selectStmt(fn *Function, s *ast.SelectStmt, label *lblock) {
+ // A blocking select of a single case degenerates to a
+ // simple send or receive.
+ // TODO(adonovan): opt: is this optimization worth its weight?
+ if len(s.Body.List) == 1 {
+ clause := s.Body.List[0].(*ast.CommClause)
+ if clause.Comm != nil {
+ b.stmt(fn, clause.Comm)
+ done := fn.newBasicBlock("select.done")
+ if label != nil {
+ label._break = done
+ }
+ fn.targets = &targets{
+ tail: fn.targets,
+ _break: done,
+ }
+ b.stmtList(fn, clause.Body)
+ fn.targets = fn.targets.tail
+ emitJump(fn, done)
+ fn.currentBlock = done
+ return
+ }
+ }
+
+ // First evaluate all channels in all cases, and find
+ // the directions of each state.
+ var states []*SelectState
+ blocking := true
+ debugInfo := fn.debugInfo()
+ for _, clause := range s.Body.List {
+ var st *SelectState
+ switch comm := clause.(*ast.CommClause).Comm.(type) {
+ case nil: // default case
+ blocking = false
+ continue
+
+ case *ast.SendStmt: // ch<- i
+ ch := b.expr(fn, comm.Chan)
+ st = &SelectState{
+ Dir: types.SendOnly,
+ Chan: ch,
+ Send: emitConv(fn, b.expr(fn, comm.Value),
+ ch.Type().Underlying().(*types.Chan).Elem()),
+ Pos: comm.Arrow,
+ }
+ if debugInfo {
+ st.DebugNode = comm
+ }
+
+ case *ast.AssignStmt: // x := <-ch
+ recv := unparen(comm.Rhs[0]).(*ast.UnaryExpr)
+ st = &SelectState{
+ Dir: types.RecvOnly,
+ Chan: b.expr(fn, recv.X),
+ Pos: recv.OpPos,
+ }
+ if debugInfo {
+ st.DebugNode = recv
+ }
+
+ case *ast.ExprStmt: // <-ch
+ recv := unparen(comm.X).(*ast.UnaryExpr)
+ st = &SelectState{
+ Dir: types.RecvOnly,
+ Chan: b.expr(fn, recv.X),
+ Pos: recv.OpPos,
+ }
+ if debugInfo {
+ st.DebugNode = recv
+ }
+ }
+ states = append(states, st)
+ }
+
+ // We dispatch on the (fair) result of Select using a
+ // sequential if-else chain, in effect:
+ //
+ // idx, recvOk, r0...r_n-1 := select(...)
+ // if idx == 0 { // receive on channel 0 (first receive => r0)
+ // x, ok := r0, recvOk
+ // ...state0...
+ // } else if v == 1 { // send on channel 1
+ // ...state1...
+ // } else {
+ // ...default...
+ // }
+ sel := &Select{
+ States: states,
+ Blocking: blocking,
+ }
+ sel.setPos(s.Select)
+ var vars []*types.Var
+ vars = append(vars, varIndex, varOk)
+ for _, st := range states {
+ if st.Dir == types.RecvOnly {
+ tElem := st.Chan.Type().Underlying().(*types.Chan).Elem()
+ vars = append(vars, anonVar(tElem))
+ }
+ }
+ sel.setType(types.NewTuple(vars...))
+
+ fn.emit(sel)
+ idx := emitExtract(fn, sel, 0)
+
+ done := fn.newBasicBlock("select.done")
+ if label != nil {
+ label._break = done
+ }
+
+ var defaultBody *[]ast.Stmt
+ state := 0
+ r := 2 // index in 'sel' tuple of value; increments if st.Dir==RECV
+ for _, cc := range s.Body.List {
+ clause := cc.(*ast.CommClause)
+ if clause.Comm == nil {
+ defaultBody = &clause.Body
+ continue
+ }
+ body := fn.newBasicBlock("select.body")
+ next := fn.newBasicBlock("select.next")
+ emitIf(fn, emitCompare(fn, token.EQL, idx, intConst(int64(state)), token.NoPos), body, next)
+ fn.currentBlock = body
+ fn.targets = &targets{
+ tail: fn.targets,
+ _break: done,
+ }
+ switch comm := clause.Comm.(type) {
+ case *ast.ExprStmt: // <-ch
+ if debugInfo {
+ v := emitExtract(fn, sel, r)
+ emitDebugRef(fn, states[state].DebugNode.(ast.Expr), v, false)
+ }
+ r++
+
+ case *ast.AssignStmt: // x := <-states[state].Chan
+ if comm.Tok == token.DEFINE {
+ fn.addLocalForIdent(comm.Lhs[0].(*ast.Ident))
+ }
+ x := b.addr(fn, comm.Lhs[0], false) // non-escaping
+ v := emitExtract(fn, sel, r)
+ if debugInfo {
+ emitDebugRef(fn, states[state].DebugNode.(ast.Expr), v, false)
+ }
+ x.store(fn, v)
+
+ if len(comm.Lhs) == 2 { // x, ok := ...
+ if comm.Tok == token.DEFINE {
+ fn.addLocalForIdent(comm.Lhs[1].(*ast.Ident))
+ }
+ ok := b.addr(fn, comm.Lhs[1], false) // non-escaping
+ ok.store(fn, emitExtract(fn, sel, 1))
+ }
+ r++
+ }
+ b.stmtList(fn, clause.Body)
+ fn.targets = fn.targets.tail
+ emitJump(fn, done)
+ fn.currentBlock = next
+ state++
+ }
+ if defaultBody != nil {
+ fn.targets = &targets{
+ tail: fn.targets,
+ _break: done,
+ }
+ b.stmtList(fn, *defaultBody)
+ fn.targets = fn.targets.tail
+ } else {
+ // A blocking select must match some case.
+ // (This should really be a runtime.errorString, not a string.)
+ fn.emit(&Panic{
+ X: emitConv(fn, stringConst("blocking select matched no case"), tEface),
+ })
+ fn.currentBlock = fn.newBasicBlock("unreachable")
+ }
+ emitJump(fn, done)
+ fn.currentBlock = done
+}
+
+// forStmt emits to fn code for the for statement s, optionally
+// labelled by label.
+//
+func (b *builder) forStmt(fn *Function, s *ast.ForStmt, label *lblock) {
+ // ...init...
+ // jump loop
+ // loop:
+ // if cond goto body else done
+ // body:
+ // ...body...
+ // jump post
+ // post: (target of continue)
+ // ...post...
+ // jump loop
+ // done: (target of break)
+ if s.Init != nil {
+ b.stmt(fn, s.Init)
+ }
+ body := fn.newBasicBlock("for.body")
+ done := fn.newBasicBlock("for.done") // target of 'break'
+ loop := body // target of back-edge
+ if s.Cond != nil {
+ loop = fn.newBasicBlock("for.loop")
+ }
+ cont := loop // target of 'continue'
+ if s.Post != nil {
+ cont = fn.newBasicBlock("for.post")
+ }
+ if label != nil {
+ label._break = done
+ label._continue = cont
+ }
+ emitJump(fn, loop)
+ fn.currentBlock = loop
+ if loop != body {
+ b.cond(fn, s.Cond, body, done)
+ fn.currentBlock = body
+ }
+ fn.targets = &targets{
+ tail: fn.targets,
+ _break: done,
+ _continue: cont,
+ }
+ b.stmt(fn, s.Body)
+ fn.targets = fn.targets.tail
+ emitJump(fn, cont)
+
+ if s.Post != nil {
+ fn.currentBlock = cont
+ b.stmt(fn, s.Post)
+ emitJump(fn, loop) // back-edge
+ }
+ fn.currentBlock = done
+}
+
+// rangeIndexed emits to fn the header for an integer-indexed loop
+// over array, *array or slice value x.
+// The v result is defined only if tv is non-nil.
+// forPos is the position of the "for" token.
+//
+func (b *builder) rangeIndexed(fn *Function, x Value, tv types.Type, pos token.Pos) (k, v Value, loop, done *BasicBlock) {
+ //
+ // length = len(x)
+ // index = -1
+ // loop: (target of continue)
+ // index++
+ // if index < length goto body else done
+ // body:
+ // k = index
+ // v = x[index]
+ // ...body...
+ // jump loop
+ // done: (target of break)
+
+ // Determine number of iterations.
+ var length Value
+ if arr, ok := deref(x.Type()).Underlying().(*types.Array); ok {
+ // For array or *array, the number of iterations is
+ // known statically thanks to the type. We avoid a
+ // data dependence upon x, permitting later dead-code
+ // elimination if x is pure, static unrolling, etc.
+ // Ranging over a nil *array may have >0 iterations.
+ // We still generate code for x, in case it has effects.
+ length = intConst(arr.Len())
+ } else {
+ // length = len(x).
+ var c Call
+ c.Call.Value = makeLen(x.Type())
+ c.Call.Args = []Value{x}
+ c.setType(tInt)
+ length = fn.emit(&c)
+ }
+
+ index := fn.addLocal(tInt, token.NoPos)
+ emitStore(fn, index, intConst(-1), pos)
+
+ loop = fn.newBasicBlock("rangeindex.loop")
+ emitJump(fn, loop)
+ fn.currentBlock = loop
+
+ incr := &BinOp{
+ Op: token.ADD,
+ X: emitLoad(fn, index),
+ Y: vOne,
+ }
+ incr.setType(tInt)
+ emitStore(fn, index, fn.emit(incr), pos)
+
+ body := fn.newBasicBlock("rangeindex.body")
+ done = fn.newBasicBlock("rangeindex.done")
+ emitIf(fn, emitCompare(fn, token.LSS, incr, length, token.NoPos), body, done)
+ fn.currentBlock = body
+
+ k = emitLoad(fn, index)
+ if tv != nil {
+ switch t := x.Type().Underlying().(type) {
+ case *types.Array:
+ instr := &Index{
+ X: x,
+ Index: k,
+ }
+ instr.setType(t.Elem())
+ instr.setPos(x.Pos())
+ v = fn.emit(instr)
+
+ case *types.Pointer: // *array
+ instr := &IndexAddr{
+ X: x,
+ Index: k,
+ }
+ instr.setType(types.NewPointer(t.Elem().Underlying().(*types.Array).Elem()))
+ instr.setPos(x.Pos())
+ v = emitLoad(fn, fn.emit(instr))
+
+ case *types.Slice:
+ instr := &IndexAddr{
+ X: x,
+ Index: k,
+ }
+ instr.setType(types.NewPointer(t.Elem()))
+ instr.setPos(x.Pos())
+ v = emitLoad(fn, fn.emit(instr))
+
+ default:
+ panic("rangeIndexed x:" + t.String())
+ }
+ }
+ return
+}
+
+// rangeIter emits to fn the header for a loop using
+// Range/Next/Extract to iterate over map or string value x.
+// tk and tv are the types of the key/value results k and v, or nil
+// if the respective component is not wanted.
+//
+func (b *builder) rangeIter(fn *Function, x Value, tk, tv types.Type, pos token.Pos) (k, v Value, loop, done *BasicBlock) {
+ //
+ // it = range x
+ // loop: (target of continue)
+ // okv = next it (ok, key, value)
+ // ok = extract okv #0
+ // if ok goto body else done
+ // body:
+ // k = extract okv #1
+ // v = extract okv #2
+ // ...body...
+ // jump loop
+ // done: (target of break)
+ //
+
+ if tk == nil {
+ tk = tInvalid
+ }
+ if tv == nil {
+ tv = tInvalid
+ }
+
+ rng := &Range{X: x}
+ rng.setPos(pos)
+ rng.setType(tRangeIter)
+ it := fn.emit(rng)
+
+ loop = fn.newBasicBlock("rangeiter.loop")
+ emitJump(fn, loop)
+ fn.currentBlock = loop
+
+ _, isString := x.Type().Underlying().(*types.Basic)
+
+ okv := &Next{
+ Iter: it,
+ IsString: isString,
+ }
+ okv.setType(types.NewTuple(
+ varOk,
+ newVar("k", tk),
+ newVar("v", tv),
+ ))
+ fn.emit(okv)
+
+ body := fn.newBasicBlock("rangeiter.body")
+ done = fn.newBasicBlock("rangeiter.done")
+ emitIf(fn, emitExtract(fn, okv, 0), body, done)
+ fn.currentBlock = body
+
+ if tk != tInvalid {
+ k = emitExtract(fn, okv, 1)
+ }
+ if tv != tInvalid {
+ v = emitExtract(fn, okv, 2)
+ }
+ return
+}
+
+// rangeChan emits to fn the header for a loop that receives from
+// channel x until it fails.
+// tk is the channel's element type, or nil if the k result is
+// not wanted
+// pos is the position of the '=' or ':=' token.
+//
+func (b *builder) rangeChan(fn *Function, x Value, tk types.Type, pos token.Pos) (k Value, loop, done *BasicBlock) {
+ //
+ // loop: (target of continue)
+ // ko = <-x (key, ok)
+ // ok = extract ko #1
+ // if ok goto body else done
+ // body:
+ // k = extract ko #0
+ // ...
+ // goto loop
+ // done: (target of break)
+
+ loop = fn.newBasicBlock("rangechan.loop")
+ emitJump(fn, loop)
+ fn.currentBlock = loop
+ recv := &UnOp{
+ Op: token.ARROW,
+ X: x,
+ CommaOk: true,
+ }
+ recv.setPos(pos)
+ recv.setType(types.NewTuple(
+ newVar("k", x.Type().Underlying().(*types.Chan).Elem()),
+ varOk,
+ ))
+ ko := fn.emit(recv)
+ body := fn.newBasicBlock("rangechan.body")
+ done = fn.newBasicBlock("rangechan.done")
+ emitIf(fn, emitExtract(fn, ko, 1), body, done)
+ fn.currentBlock = body
+ if tk != nil {
+ k = emitExtract(fn, ko, 0)
+ }
+ return
+}
+
+// rangeStmt emits to fn code for the range statement s, optionally
+// labelled by label.
+//
+func (b *builder) rangeStmt(fn *Function, s *ast.RangeStmt, label *lblock) {
+ var tk, tv types.Type
+ if s.Key != nil && !isBlankIdent(s.Key) {
+ tk = fn.Pkg.typeOf(s.Key)
+ }
+ if s.Value != nil && !isBlankIdent(s.Value) {
+ tv = fn.Pkg.typeOf(s.Value)
+ }
+
+ // If iteration variables are defined (:=), this
+ // occurs once outside the loop.
+ //
+ // Unlike a short variable declaration, a RangeStmt
+ // using := never redeclares an existing variable; it
+ // always creates a new one.
+ if s.Tok == token.DEFINE {
+ if tk != nil {
+ fn.addLocalForIdent(s.Key.(*ast.Ident))
+ }
+ if tv != nil {
+ fn.addLocalForIdent(s.Value.(*ast.Ident))
+ }
+ }
+
+ x := b.expr(fn, s.X)
+
+ var k, v Value
+ var loop, done *BasicBlock
+ switch rt := x.Type().Underlying().(type) {
+ case *types.Slice, *types.Array, *types.Pointer: // *array
+ k, v, loop, done = b.rangeIndexed(fn, x, tv, s.For)
+
+ case *types.Chan:
+ k, loop, done = b.rangeChan(fn, x, tk, s.For)
+
+ case *types.Map, *types.Basic: // string
+ k, v, loop, done = b.rangeIter(fn, x, tk, tv, s.For)
+
+ default:
+ panic("Cannot range over: " + rt.String())
+ }
+
+ // Evaluate both LHS expressions before we update either.
+ var kl, vl lvalue
+ if tk != nil {
+ kl = b.addr(fn, s.Key, false) // non-escaping
+ }
+ if tv != nil {
+ vl = b.addr(fn, s.Value, false) // non-escaping
+ }
+ if tk != nil {
+ kl.store(fn, k)
+ }
+ if tv != nil {
+ vl.store(fn, v)
+ }
+
+ if label != nil {
+ label._break = done
+ label._continue = loop
+ }
+
+ fn.targets = &targets{
+ tail: fn.targets,
+ _break: done,
+ _continue: loop,
+ }
+ b.stmt(fn, s.Body)
+ fn.targets = fn.targets.tail
+ emitJump(fn, loop) // back-edge
+ fn.currentBlock = done
+}
+
+// stmt lowers statement s to SSA form, emitting code to fn.
+func (b *builder) stmt(fn *Function, _s ast.Stmt) {
+ // The label of the current statement. If non-nil, its _goto
+ // target is always set; its _break and _continue are set only
+ // within the body of switch/typeswitch/select/for/range.
+ // It is effectively an additional default-nil parameter of stmt().
+ var label *lblock
+start:
+ switch s := _s.(type) {
+ case *ast.EmptyStmt:
+ // ignore. (Usually removed by gofmt.)
+
+ case *ast.DeclStmt: // Con, Var or Typ
+ d := s.Decl.(*ast.GenDecl)
+ if d.Tok == token.VAR {
+ for _, spec := range d.Specs {
+ if vs, ok := spec.(*ast.ValueSpec); ok {
+ b.localValueSpec(fn, vs)
+ }
+ }
+ }
+
+ case *ast.LabeledStmt:
+ label = fn.labelledBlock(s.Label)
+ emitJump(fn, label._goto)
+ fn.currentBlock = label._goto
+ _s = s.Stmt
+ goto start // effectively: tailcall stmt(fn, s.Stmt, label)
+
+ case *ast.ExprStmt:
+ b.expr(fn, s.X)
+
+ case *ast.SendStmt:
+ fn.emit(&Send{
+ Chan: b.expr(fn, s.Chan),
+ X: emitConv(fn, b.expr(fn, s.Value),
+ fn.Pkg.typeOf(s.Chan).Underlying().(*types.Chan).Elem()),
+ pos: s.Arrow,
+ })
+
+ case *ast.IncDecStmt:
+ op := token.ADD
+ if s.Tok == token.DEC {
+ op = token.SUB
+ }
+ loc := b.addr(fn, s.X, false)
+ b.assignOp(fn, loc, NewConst(constant.MakeInt64(1), loc.typ()), op, s.Pos())
+
+ case *ast.AssignStmt:
+ switch s.Tok {
+ case token.ASSIGN, token.DEFINE:
+ b.assignStmt(fn, s.Lhs, s.Rhs, s.Tok == token.DEFINE)
+
+ default: // +=, etc.
+ op := s.Tok + token.ADD - token.ADD_ASSIGN
+ b.assignOp(fn, b.addr(fn, s.Lhs[0], false), b.expr(fn, s.Rhs[0]), op, s.Pos())
+ }
+
+ case *ast.GoStmt:
+ // The "intrinsics" new/make/len/cap are forbidden here.
+ // panic is treated like an ordinary function call.
+ v := Go{pos: s.Go}
+ b.setCall(fn, s.Call, &v.Call)
+ fn.emit(&v)
+
+ case *ast.DeferStmt:
+ // The "intrinsics" new/make/len/cap are forbidden here.
+ // panic is treated like an ordinary function call.
+ v := Defer{pos: s.Defer}
+ b.setCall(fn, s.Call, &v.Call)
+ fn.emit(&v)
+
+ // A deferred call can cause recovery from panic,
+ // and control resumes at the Recover block.
+ createRecoverBlock(fn)
+
+ case *ast.ReturnStmt:
+ var results []Value
+ if len(s.Results) == 1 && fn.Signature.Results().Len() > 1 {
+ // Return of one expression in a multi-valued function.
+ tuple := b.exprN(fn, s.Results[0])
+ ttuple := tuple.Type().(*types.Tuple)
+ for i, n := 0, ttuple.Len(); i < n; i++ {
+ results = append(results,
+ emitConv(fn, emitExtract(fn, tuple, i),
+ fn.Signature.Results().At(i).Type()))
+ }
+ } else {
+ // 1:1 return, or no-arg return in non-void function.
+ for i, r := range s.Results {
+ v := emitConv(fn, b.expr(fn, r), fn.Signature.Results().At(i).Type())
+ results = append(results, v)
+ }
+ }
+ if fn.namedResults != nil {
+ // Function has named result parameters (NRPs).
+ // Perform parallel assignment of return operands to NRPs.
+ for i, r := range results {
+ emitStore(fn, fn.namedResults[i], r, s.Return)
+ }
+ }
+ // Run function calls deferred in this
+ // function when explicitly returning from it.
+ fn.emit(new(RunDefers))
+ if fn.namedResults != nil {
+ // Reload NRPs to form the result tuple.
+ results = results[:0]
+ for _, r := range fn.namedResults {
+ results = append(results, emitLoad(fn, r))
+ }
+ }
+ fn.emit(&Return{Results: results, pos: s.Return})
+ fn.currentBlock = fn.newBasicBlock("unreachable")
+
+ case *ast.BranchStmt:
+ var block *BasicBlock
+ switch s.Tok {
+ case token.BREAK:
+ if s.Label != nil {
+ block = fn.labelledBlock(s.Label)._break
+ } else {
+ for t := fn.targets; t != nil && block == nil; t = t.tail {
+ block = t._break
+ }
+ }
+
+ case token.CONTINUE:
+ if s.Label != nil {
+ block = fn.labelledBlock(s.Label)._continue
+ } else {
+ for t := fn.targets; t != nil && block == nil; t = t.tail {
+ block = t._continue
+ }
+ }
+
+ case token.FALLTHROUGH:
+ for t := fn.targets; t != nil && block == nil; t = t.tail {
+ block = t._fallthrough
+ }
+
+ case token.GOTO:
+ block = fn.labelledBlock(s.Label)._goto
+ }
+ emitJump(fn, block)
+ fn.currentBlock = fn.newBasicBlock("unreachable")
+
+ case *ast.BlockStmt:
+ b.stmtList(fn, s.List)
+
+ case *ast.IfStmt:
+ if s.Init != nil {
+ b.stmt(fn, s.Init)
+ }
+ then := fn.newBasicBlock("if.then")
+ done := fn.newBasicBlock("if.done")
+ els := done
+ if s.Else != nil {
+ els = fn.newBasicBlock("if.else")
+ }
+ b.cond(fn, s.Cond, then, els)
+ fn.currentBlock = then
+ b.stmt(fn, s.Body)
+ emitJump(fn, done)
+
+ if s.Else != nil {
+ fn.currentBlock = els
+ b.stmt(fn, s.Else)
+ emitJump(fn, done)
+ }
+
+ fn.currentBlock = done
+
+ case *ast.SwitchStmt:
+ b.switchStmt(fn, s, label)
+
+ case *ast.TypeSwitchStmt:
+ b.typeSwitchStmt(fn, s, label)
+
+ case *ast.SelectStmt:
+ b.selectStmt(fn, s, label)
+
+ case *ast.ForStmt:
+ b.forStmt(fn, s, label)
+
+ case *ast.RangeStmt:
+ b.rangeStmt(fn, s, label)
+
+ default:
+ panic(fmt.Sprintf("unexpected statement kind: %T", s))
+ }
+}
+
+// buildFunction builds SSA code for the body of function fn. Idempotent.
+func (b *builder) buildFunction(fn *Function) {
+ if fn.Blocks != nil {
+ return // building already started
+ }
+
+ var recvField *ast.FieldList
+ var body *ast.BlockStmt
+ var functype *ast.FuncType
+ switch n := fn.syntax.(type) {
+ case nil:
+ return // not a Go source function. (Synthetic, or from object file.)
+ case *ast.FuncDecl:
+ functype = n.Type
+ recvField = n.Recv
+ body = n.Body
+ case *ast.FuncLit:
+ functype = n.Type
+ body = n.Body
+ default:
+ panic(n)
+ }
+
+ if body == nil {
+ // External function.
+ if fn.Params == nil {
+ // This condition ensures we add a non-empty
+ // params list once only, but we may attempt
+ // the degenerate empty case repeatedly.
+ // TODO(adonovan): opt: don't do that.
+
+ // We set Function.Params even though there is no body
+ // code to reference them. This simplifies clients.
+ if recv := fn.Signature.Recv(); recv != nil {
+ fn.addParamObj(recv)
+ }
+ params := fn.Signature.Params()
+ for i, n := 0, params.Len(); i < n; i++ {
+ fn.addParamObj(params.At(i))
+ }
+ }
+ return
+ }
+ if fn.Prog.mode&LogSource != 0 {
+ defer logStack("build function %s @ %s", fn, fn.Prog.Fset.Position(fn.pos))()
+ }
+ fn.startBody()
+ fn.createSyntacticParams(recvField, functype)
+ b.stmt(fn, body)
+ if cb := fn.currentBlock; cb != nil && (cb == fn.Blocks[0] || cb == fn.Recover || cb.Preds != nil) {
+ // Control fell off the end of the function's body block.
+ //
+ // Block optimizations eliminate the current block, if
+ // unreachable. It is a builder invariant that
+ // if this no-arg return is ill-typed for
+ // fn.Signature.Results, this block must be
+ // unreachable. The sanity checker checks this.
+ fn.emit(new(RunDefers))
+ fn.emit(new(Return))
+ }
+ fn.finishBody()
+}
+
+// buildFuncDecl builds SSA code for the function or method declared
+// by decl in package pkg.
+//
+func (b *builder) buildFuncDecl(pkg *Package, decl *ast.FuncDecl) {
+ id := decl.Name
+ if isBlankIdent(id) {
+ return // discard
+ }
+ fn := pkg.values[pkg.info.Defs[id]].(*Function)
+ if decl.Recv == nil && id.Name == "init" {
+ var v Call
+ v.Call.Value = fn
+ v.setType(types.NewTuple())
+ pkg.init.emit(&v)
+ }
+ b.buildFunction(fn)
+}
+
+// Build calls Package.Build for each package in prog.
+// Building occurs in parallel unless the BuildSerially mode flag was set.
+//
+// Build is intended for whole-program analysis; a typical compiler
+// need only build a single package.
+//
+// Build is idempotent and thread-safe.
+//
+func (prog *Program) Build() {
+ var wg sync.WaitGroup
+ for _, p := range prog.packages {
+ if prog.mode&BuildSerially != 0 {
+ p.Build()
+ } else {
+ wg.Add(1)
+ go func(p *Package) {
+ p.Build()
+ wg.Done()
+ }(p)
+ }
+ }
+ wg.Wait()
+}
+
+// Build builds SSA code for all functions and vars in package p.
+//
+// Precondition: CreatePackage must have been called for all of p's
+// direct imports (and hence its direct imports must have been
+// error-free).
+//
+// Build is idempotent and thread-safe.
+//
+func (p *Package) Build() { p.buildOnce.Do(p.build) }
+
+func (p *Package) build() {
+ if p.info == nil {
+ return // synthetic package, e.g. "testmain"
+ }
+
+ // Ensure we have runtime type info for all exported members.
+ // TODO(adonovan): ideally belongs in memberFromObject, but
+ // that would require package creation in topological order.
+ for name, mem := range p.Members {
+ if ast.IsExported(name) {
+ p.Prog.needMethodsOf(mem.Type())
+ }
+ }
+ if p.Prog.mode&LogSource != 0 {
+ defer logStack("build %s", p)()
+ }
+ init := p.init
+ init.startBody()
+
+ var done *BasicBlock
+
+ if p.Prog.mode&BareInits == 0 {
+ // Make init() skip if package is already initialized.
+ initguard := p.Var("init$guard")
+ doinit := init.newBasicBlock("init.start")
+ done = init.newBasicBlock("init.done")
+ emitIf(init, emitLoad(init, initguard), done, doinit)
+ init.currentBlock = doinit
+ emitStore(init, initguard, vTrue, token.NoPos)
+
+ // Call the init() function of each package we import.
+ for _, pkg := range p.Pkg.Imports() {
+ prereq := p.Prog.packages[pkg]
+ if prereq == nil {
+ panic(fmt.Sprintf("Package(%q).Build(): unsatisfied import: Program.CreatePackage(%q) was not called", p.Pkg.Path(), pkg.Path()))
+ }
+ var v Call
+ v.Call.Value = prereq.init
+ v.Call.pos = init.pos
+ v.setType(types.NewTuple())
+ init.emit(&v)
+ }
+ }
+
+ var b builder
+
+ // Initialize package-level vars in correct order.
+ for _, varinit := range p.info.InitOrder {
+ if init.Prog.mode&LogSource != 0 {
+ fmt.Fprintf(os.Stderr, "build global initializer %v @ %s\n",
+ varinit.Lhs, p.Prog.Fset.Position(varinit.Rhs.Pos()))
+ }
+ if len(varinit.Lhs) == 1 {
+ // 1:1 initialization: var x, y = a(), b()
+ var lval lvalue
+ if v := varinit.Lhs[0]; v.Name() != "_" {
+ lval = &address{addr: p.values[v].(*Global), pos: v.Pos()}
+ } else {
+ lval = blank{}
+ }
+ b.assign(init, lval, varinit.Rhs, true, nil)
+ } else {
+ // n:1 initialization: var x, y := f()
+ tuple := b.exprN(init, varinit.Rhs)
+ for i, v := range varinit.Lhs {
+ if v.Name() == "_" {
+ continue
+ }
+ emitStore(init, p.values[v].(*Global), emitExtract(init, tuple, i), v.Pos())
+ }
+ }
+ }
+
+ // Build all package-level functions, init functions
+ // and methods, including unreachable/blank ones.
+ // We build them in source order, but it's not significant.
+ for _, file := range p.files {
+ for _, decl := range file.Decls {
+ if decl, ok := decl.(*ast.FuncDecl); ok {
+ b.buildFuncDecl(p, decl)
+ }
+ }
+ }
+
+ // Finish up init().
+ if p.Prog.mode&BareInits == 0 {
+ emitJump(init, done)
+ init.currentBlock = done
+ }
+ init.emit(new(Return))
+ init.finishBody()
+
+ p.info = nil // We no longer need ASTs or go/types deductions.
+
+ if p.Prog.mode&SanityCheckFunctions != 0 {
+ sanityCheckPackage(p)
+ }
+}
+
+// Like ObjectOf, but panics instead of returning nil.
+// Only valid during p's create and build phases.
+func (p *Package) objectOf(id *ast.Ident) types.Object {
+ if o := p.info.ObjectOf(id); o != nil {
+ return o
+ }
+ panic(fmt.Sprintf("no types.Object for ast.Ident %s @ %s",
+ id.Name, p.Prog.Fset.Position(id.Pos())))
+}
+
+// Like TypeOf, but panics instead of returning nil.
+// Only valid during p's create and build phases.
+func (p *Package) typeOf(e ast.Expr) types.Type {
+ if T := p.info.TypeOf(e); T != nil {
+ return T
+ }
+ panic(fmt.Sprintf("no type for %T @ %s",
+ e, p.Prog.Fset.Position(e.Pos())))
+}
projects / dotfiles / .git / blobdiff