Current File : //usr/local/go/src/cmd/compile/internal/walk/complit.go
// Copyright 2009 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 walk
import (
"cmd/compile/internal/base"
"cmd/compile/internal/ir"
"cmd/compile/internal/ssagen"
"cmd/compile/internal/staticdata"
"cmd/compile/internal/staticinit"
"cmd/compile/internal/typecheck"
"cmd/compile/internal/types"
"cmd/internal/obj"
)
// walkCompLit walks a composite literal node:
// OARRAYLIT, OSLICELIT, OMAPLIT, OSTRUCTLIT (all CompLitExpr), or OPTRLIT (AddrExpr).
func walkCompLit(n ir.Node, init *ir.Nodes) ir.Node {
if isStaticCompositeLiteral(n) && !ssagen.TypeOK(n.Type()) {
n := n.(*ir.CompLitExpr) // not OPTRLIT
// n can be directly represented in the read-only data section.
// Make direct reference to the static data. See issue 12841.
vstat := readonlystaticname(n.Type())
fixedlit(inInitFunction, initKindStatic, n, vstat, init)
return typecheck.Expr(vstat)
}
var_ := typecheck.Temp(n.Type())
anylit(n, var_, init)
return var_
}
// initContext is the context in which static data is populated.
// It is either in an init function or in any other function.
// Static data populated in an init function will be written either
// zero times (as a readonly, static data symbol) or
// one time (during init function execution).
// Either way, there is no opportunity for races or further modification,
// so the data can be written to a (possibly readonly) data symbol.
// Static data populated in any other function needs to be local to
// that function to allow multiple instances of that function
// to execute concurrently without clobbering each others' data.
type initContext uint8
const (
inInitFunction initContext = iota
inNonInitFunction
)
func (c initContext) String() string {
if c == inInitFunction {
return "inInitFunction"
}
return "inNonInitFunction"
}
// readonlystaticname returns a name backed by a read-only static data symbol.
func readonlystaticname(t *types.Type) *ir.Name {
n := staticinit.StaticName(t)
n.MarkReadonly()
n.Linksym().Set(obj.AttrContentAddressable, true)
n.Linksym().Set(obj.AttrLocal, true)
return n
}
func isSimpleName(nn ir.Node) bool {
if nn.Op() != ir.ONAME || ir.IsBlank(nn) {
return false
}
n := nn.(*ir.Name)
return n.OnStack()
}
func litas(l ir.Node, r ir.Node, init *ir.Nodes) {
appendWalkStmt(init, ir.NewAssignStmt(base.Pos, l, r))
}
// initGenType is a bitmap indicating the types of generation that will occur for a static value.
type initGenType uint8
const (
initDynamic initGenType = 1 << iota // contains some dynamic values, for which init code will be generated
initConst // contains some constant values, which may be written into data symbols
)
// getdyn calculates the initGenType for n.
// If top is false, getdyn is recursing.
func getdyn(n ir.Node, top bool) initGenType {
switch n.Op() {
default:
if ir.IsConstNode(n) {
return initConst
}
return initDynamic
case ir.OSLICELIT:
n := n.(*ir.CompLitExpr)
if !top {
return initDynamic
}
if n.Len/4 > int64(len(n.List)) {
// <25% of entries have explicit values.
// Very rough estimation, it takes 4 bytes of instructions
// to initialize 1 byte of result. So don't use a static
// initializer if the dynamic initialization code would be
// smaller than the static value.
// See issue 23780.
return initDynamic
}
case ir.OARRAYLIT, ir.OSTRUCTLIT:
}
lit := n.(*ir.CompLitExpr)
var mode initGenType
for _, n1 := range lit.List {
switch n1.Op() {
case ir.OKEY:
n1 = n1.(*ir.KeyExpr).Value
case ir.OSTRUCTKEY:
n1 = n1.(*ir.StructKeyExpr).Value
}
mode |= getdyn(n1, false)
if mode == initDynamic|initConst {
break
}
}
return mode
}
// isStaticCompositeLiteral reports whether n is a compile-time constant.
func isStaticCompositeLiteral(n ir.Node) bool {
switch n.Op() {
case ir.OSLICELIT:
return false
case ir.OARRAYLIT:
n := n.(*ir.CompLitExpr)
for _, r := range n.List {
if r.Op() == ir.OKEY {
r = r.(*ir.KeyExpr).Value
}
if !isStaticCompositeLiteral(r) {
return false
}
}
return true
case ir.OSTRUCTLIT:
n := n.(*ir.CompLitExpr)
for _, r := range n.List {
r := r.(*ir.StructKeyExpr)
if !isStaticCompositeLiteral(r.Value) {
return false
}
}
return true
case ir.OLITERAL, ir.ONIL:
return true
case ir.OCONVIFACE:
// See staticassign's OCONVIFACE case for comments.
n := n.(*ir.ConvExpr)
val := ir.Node(n)
for val.Op() == ir.OCONVIFACE {
val = val.(*ir.ConvExpr).X
}
if val.Type().IsInterface() {
return val.Op() == ir.ONIL
}
if types.IsDirectIface(val.Type()) && val.Op() == ir.ONIL {
return true
}
return isStaticCompositeLiteral(val)
}
return false
}
// initKind is a kind of static initialization: static, dynamic, or local.
// Static initialization represents literals and
// literal components of composite literals.
// Dynamic initialization represents non-literals and
// non-literal components of composite literals.
// LocalCode initialization represents initialization
// that occurs purely in generated code local to the function of use.
// Initialization code is sometimes generated in passes,
// first static then dynamic.
type initKind uint8
const (
initKindStatic initKind = iota + 1
initKindDynamic
initKindLocalCode
)
// fixedlit handles struct, array, and slice literals.
// TODO: expand documentation.
func fixedlit(ctxt initContext, kind initKind, n *ir.CompLitExpr, var_ ir.Node, init *ir.Nodes) {
isBlank := var_ == ir.BlankNode
var splitnode func(ir.Node) (a ir.Node, value ir.Node)
switch n.Op() {
case ir.OARRAYLIT, ir.OSLICELIT:
var k int64
splitnode = func(r ir.Node) (ir.Node, ir.Node) {
if r.Op() == ir.OKEY {
kv := r.(*ir.KeyExpr)
k = typecheck.IndexConst(kv.Key)
if k < 0 {
base.Fatalf("fixedlit: invalid index %v", kv.Key)
}
r = kv.Value
}
a := ir.NewIndexExpr(base.Pos, var_, ir.NewInt(k))
k++
if isBlank {
return ir.BlankNode, r
}
return a, r
}
case ir.OSTRUCTLIT:
splitnode = func(rn ir.Node) (ir.Node, ir.Node) {
r := rn.(*ir.StructKeyExpr)
if r.Field.IsBlank() || isBlank {
return ir.BlankNode, r.Value
}
ir.SetPos(r)
return ir.NewSelectorExpr(base.Pos, ir.ODOT, var_, r.Field), r.Value
}
default:
base.Fatalf("fixedlit bad op: %v", n.Op())
}
for _, r := range n.List {
a, value := splitnode(r)
if a == ir.BlankNode && !staticinit.AnySideEffects(value) {
// Discard.
continue
}
switch value.Op() {
case ir.OSLICELIT:
value := value.(*ir.CompLitExpr)
if (kind == initKindStatic && ctxt == inNonInitFunction) || (kind == initKindDynamic && ctxt == inInitFunction) {
slicelit(ctxt, value, a, init)
continue
}
case ir.OARRAYLIT, ir.OSTRUCTLIT:
value := value.(*ir.CompLitExpr)
fixedlit(ctxt, kind, value, a, init)
continue
}
islit := ir.IsConstNode(value)
if (kind == initKindStatic && !islit) || (kind == initKindDynamic && islit) {
continue
}
// build list of assignments: var[index] = expr
ir.SetPos(a)
as := ir.NewAssignStmt(base.Pos, a, value)
as = typecheck.Stmt(as).(*ir.AssignStmt)
switch kind {
case initKindStatic:
genAsStatic(as)
case initKindDynamic, initKindLocalCode:
a = orderStmtInPlace(as, map[string][]*ir.Name{})
a = walkStmt(a)
init.Append(a)
default:
base.Fatalf("fixedlit: bad kind %d", kind)
}
}
}
func isSmallSliceLit(n *ir.CompLitExpr) bool {
if n.Op() != ir.OSLICELIT {
return false
}
return n.Type().Elem().Width == 0 || n.Len <= ir.MaxSmallArraySize/n.Type().Elem().Width
}
func slicelit(ctxt initContext, n *ir.CompLitExpr, var_ ir.Node, init *ir.Nodes) {
// make an array type corresponding the number of elements we have
t := types.NewArray(n.Type().Elem(), n.Len)
types.CalcSize(t)
if ctxt == inNonInitFunction {
// put everything into static array
vstat := staticinit.StaticName(t)
fixedlit(ctxt, initKindStatic, n, vstat, init)
fixedlit(ctxt, initKindDynamic, n, vstat, init)
// copy static to slice
var_ = typecheck.AssignExpr(var_)
name, offset, ok := staticinit.StaticLoc(var_)
if !ok || name.Class != ir.PEXTERN {
base.Fatalf("slicelit: %v", var_)
}
staticdata.InitSlice(name, offset, vstat.Linksym(), t.NumElem())
return
}
// recipe for var = []t{...}
// 1. make a static array
// var vstat [...]t
// 2. assign (data statements) the constant part
// vstat = constpart{}
// 3. make an auto pointer to array and allocate heap to it
// var vauto *[...]t = new([...]t)
// 4. copy the static array to the auto array
// *vauto = vstat
// 5. for each dynamic part assign to the array
// vauto[i] = dynamic part
// 6. assign slice of allocated heap to var
// var = vauto[:]
//
// an optimization is done if there is no constant part
// 3. var vauto *[...]t = new([...]t)
// 5. vauto[i] = dynamic part
// 6. var = vauto[:]
// if the literal contains constants,
// make static initialized array (1),(2)
var vstat ir.Node
mode := getdyn(n, true)
if mode&initConst != 0 && !isSmallSliceLit(n) {
if ctxt == inInitFunction {
vstat = readonlystaticname(t)
} else {
vstat = staticinit.StaticName(t)
}
fixedlit(ctxt, initKindStatic, n, vstat, init)
}
// make new auto *array (3 declare)
vauto := typecheck.Temp(types.NewPtr(t))
// set auto to point at new temp or heap (3 assign)
var a ir.Node
if x := n.Prealloc; x != nil {
// temp allocated during order.go for dddarg
if !types.Identical(t, x.Type()) {
panic("dotdotdot base type does not match order's assigned type")
}
a = initStackTemp(init, x, vstat)
} else if n.Esc() == ir.EscNone {
a = initStackTemp(init, typecheck.Temp(t), vstat)
} else {
a = ir.NewUnaryExpr(base.Pos, ir.ONEW, ir.TypeNode(t))
}
appendWalkStmt(init, ir.NewAssignStmt(base.Pos, vauto, a))
if vstat != nil && n.Prealloc == nil && n.Esc() != ir.EscNone {
// If we allocated on the heap with ONEW, copy the static to the
// heap (4). We skip this for stack temporaries, because
// initStackTemp already handled the copy.
a = ir.NewStarExpr(base.Pos, vauto)
appendWalkStmt(init, ir.NewAssignStmt(base.Pos, a, vstat))
}
// put dynamics into array (5)
var index int64
for _, value := range n.List {
if value.Op() == ir.OKEY {
kv := value.(*ir.KeyExpr)
index = typecheck.IndexConst(kv.Key)
if index < 0 {
base.Fatalf("slicelit: invalid index %v", kv.Key)
}
value = kv.Value
}
a := ir.NewIndexExpr(base.Pos, vauto, ir.NewInt(index))
a.SetBounded(true)
index++
// TODO need to check bounds?
switch value.Op() {
case ir.OSLICELIT:
break
case ir.OARRAYLIT, ir.OSTRUCTLIT:
value := value.(*ir.CompLitExpr)
k := initKindDynamic
if vstat == nil {
// Generate both static and dynamic initializations.
// See issue #31987.
k = initKindLocalCode
}
fixedlit(ctxt, k, value, a, init)
continue
}
if vstat != nil && ir.IsConstNode(value) { // already set by copy from static value
continue
}
// build list of vauto[c] = expr
ir.SetPos(value)
as := typecheck.Stmt(ir.NewAssignStmt(base.Pos, a, value))
as = orderStmtInPlace(as, map[string][]*ir.Name{})
as = walkStmt(as)
init.Append(as)
}
// make slice out of heap (6)
a = ir.NewAssignStmt(base.Pos, var_, ir.NewSliceExpr(base.Pos, ir.OSLICE, vauto, nil, nil, nil))
a = typecheck.Stmt(a)
a = orderStmtInPlace(a, map[string][]*ir.Name{})
a = walkStmt(a)
init.Append(a)
}
func maplit(n *ir.CompLitExpr, m ir.Node, init *ir.Nodes) {
// make the map var
a := ir.NewCallExpr(base.Pos, ir.OMAKE, nil, nil)
a.SetEsc(n.Esc())
a.Args = []ir.Node{ir.TypeNode(n.Type()), ir.NewInt(int64(len(n.List)))}
litas(m, a, init)
entries := n.List
// The order pass already removed any dynamic (runtime-computed) entries.
// All remaining entries are static. Double-check that.
for _, r := range entries {
r := r.(*ir.KeyExpr)
if !isStaticCompositeLiteral(r.Key) || !isStaticCompositeLiteral(r.Value) {
base.Fatalf("maplit: entry is not a literal: %v", r)
}
}
if len(entries) > 25 {
// For a large number of entries, put them in an array and loop.
// build types [count]Tindex and [count]Tvalue
tk := types.NewArray(n.Type().Key(), int64(len(entries)))
te := types.NewArray(n.Type().Elem(), int64(len(entries)))
tk.SetNoalg(true)
te.SetNoalg(true)
types.CalcSize(tk)
types.CalcSize(te)
// make and initialize static arrays
vstatk := readonlystaticname(tk)
vstate := readonlystaticname(te)
datak := ir.NewCompLitExpr(base.Pos, ir.OARRAYLIT, nil, nil)
datae := ir.NewCompLitExpr(base.Pos, ir.OARRAYLIT, nil, nil)
for _, r := range entries {
r := r.(*ir.KeyExpr)
datak.List.Append(r.Key)
datae.List.Append(r.Value)
}
fixedlit(inInitFunction, initKindStatic, datak, vstatk, init)
fixedlit(inInitFunction, initKindStatic, datae, vstate, init)
// loop adding structure elements to map
// for i = 0; i < len(vstatk); i++ {
// map[vstatk[i]] = vstate[i]
// }
i := typecheck.Temp(types.Types[types.TINT])
rhs := ir.NewIndexExpr(base.Pos, vstate, i)
rhs.SetBounded(true)
kidx := ir.NewIndexExpr(base.Pos, vstatk, i)
kidx.SetBounded(true)
lhs := ir.NewIndexExpr(base.Pos, m, kidx)
zero := ir.NewAssignStmt(base.Pos, i, ir.NewInt(0))
cond := ir.NewBinaryExpr(base.Pos, ir.OLT, i, ir.NewInt(tk.NumElem()))
incr := ir.NewAssignStmt(base.Pos, i, ir.NewBinaryExpr(base.Pos, ir.OADD, i, ir.NewInt(1)))
var body ir.Node = ir.NewAssignStmt(base.Pos, lhs, rhs)
body = typecheck.Stmt(body) // typechecker rewrites OINDEX to OINDEXMAP
body = orderStmtInPlace(body, map[string][]*ir.Name{})
loop := ir.NewForStmt(base.Pos, nil, cond, incr, nil)
loop.Body = []ir.Node{body}
*loop.PtrInit() = []ir.Node{zero}
appendWalkStmt(init, loop)
return
}
// For a small number of entries, just add them directly.
// Build list of var[c] = expr.
// Use temporaries so that mapassign1 can have addressable key, elem.
// TODO(josharian): avoid map key temporaries for mapfast_* assignments with literal keys.
tmpkey := typecheck.Temp(m.Type().Key())
tmpelem := typecheck.Temp(m.Type().Elem())
for _, r := range entries {
r := r.(*ir.KeyExpr)
index, elem := r.Key, r.Value
ir.SetPos(index)
appendWalkStmt(init, ir.NewAssignStmt(base.Pos, tmpkey, index))
ir.SetPos(elem)
appendWalkStmt(init, ir.NewAssignStmt(base.Pos, tmpelem, elem))
ir.SetPos(tmpelem)
var a ir.Node = ir.NewAssignStmt(base.Pos, ir.NewIndexExpr(base.Pos, m, tmpkey), tmpelem)
a = typecheck.Stmt(a) // typechecker rewrites OINDEX to OINDEXMAP
a = orderStmtInPlace(a, map[string][]*ir.Name{})
appendWalkStmt(init, a)
}
appendWalkStmt(init, ir.NewUnaryExpr(base.Pos, ir.OVARKILL, tmpkey))
appendWalkStmt(init, ir.NewUnaryExpr(base.Pos, ir.OVARKILL, tmpelem))
}
func anylit(n ir.Node, var_ ir.Node, init *ir.Nodes) {
t := n.Type()
switch n.Op() {
default:
base.Fatalf("anylit: not lit, op=%v node=%v", n.Op(), n)
case ir.ONAME:
n := n.(*ir.Name)
appendWalkStmt(init, ir.NewAssignStmt(base.Pos, var_, n))
case ir.OMETHEXPR:
n := n.(*ir.SelectorExpr)
anylit(n.FuncName(), var_, init)
case ir.OPTRLIT:
n := n.(*ir.AddrExpr)
if !t.IsPtr() {
base.Fatalf("anylit: not ptr")
}
var r ir.Node
if n.Prealloc != nil {
// n.Prealloc is stack temporary used as backing store.
r = initStackTemp(init, n.Prealloc, nil)
} else {
r = ir.NewUnaryExpr(base.Pos, ir.ONEW, ir.TypeNode(n.X.Type()))
r.SetEsc(n.Esc())
}
appendWalkStmt(init, ir.NewAssignStmt(base.Pos, var_, r))
var_ = ir.NewStarExpr(base.Pos, var_)
var_ = typecheck.AssignExpr(var_)
anylit(n.X, var_, init)
case ir.OSTRUCTLIT, ir.OARRAYLIT:
n := n.(*ir.CompLitExpr)
if !t.IsStruct() && !t.IsArray() {
base.Fatalf("anylit: not struct/array")
}
if isSimpleName(var_) && len(n.List) > 4 {
// lay out static data
vstat := readonlystaticname(t)
ctxt := inInitFunction
if n.Op() == ir.OARRAYLIT {
ctxt = inNonInitFunction
}
fixedlit(ctxt, initKindStatic, n, vstat, init)
// copy static to var
appendWalkStmt(init, ir.NewAssignStmt(base.Pos, var_, vstat))
// add expressions to automatic
fixedlit(inInitFunction, initKindDynamic, n, var_, init)
break
}
var components int64
if n.Op() == ir.OARRAYLIT {
components = t.NumElem()
} else {
components = int64(t.NumFields())
}
// initialization of an array or struct with unspecified components (missing fields or arrays)
if isSimpleName(var_) || int64(len(n.List)) < components {
appendWalkStmt(init, ir.NewAssignStmt(base.Pos, var_, nil))
}
fixedlit(inInitFunction, initKindLocalCode, n, var_, init)
case ir.OSLICELIT:
n := n.(*ir.CompLitExpr)
slicelit(inInitFunction, n, var_, init)
case ir.OMAPLIT:
n := n.(*ir.CompLitExpr)
if !t.IsMap() {
base.Fatalf("anylit: not map")
}
maplit(n, var_, init)
}
}
// oaslit handles special composite literal assignments.
// It returns true if n's effects have been added to init,
// in which case n should be dropped from the program by the caller.
func oaslit(n *ir.AssignStmt, init *ir.Nodes) bool {
if n.X == nil || n.Y == nil {
// not a special composite literal assignment
return false
}
if n.X.Type() == nil || n.Y.Type() == nil {
// not a special composite literal assignment
return false
}
if !isSimpleName(n.X) {
// not a special composite literal assignment
return false
}
x := n.X.(*ir.Name)
if !types.Identical(n.X.Type(), n.Y.Type()) {
// not a special composite literal assignment
return false
}
switch n.Y.Op() {
default:
// not a special composite literal assignment
return false
case ir.OSTRUCTLIT, ir.OARRAYLIT, ir.OSLICELIT, ir.OMAPLIT:
if ir.Any(n.Y, func(y ir.Node) bool { return ir.Uses(y, x) }) {
// not a special composite literal assignment
return false
}
anylit(n.Y, n.X, init)
}
return true
}
func genAsStatic(as *ir.AssignStmt) {
if as.X.Type() == nil {
base.Fatalf("genAsStatic as.Left not typechecked")
}
name, offset, ok := staticinit.StaticLoc(as.X)
if !ok || (name.Class != ir.PEXTERN && as.X != ir.BlankNode) {
base.Fatalf("genAsStatic: lhs %v", as.X)
}
switch r := as.Y; r.Op() {
case ir.OLITERAL:
staticdata.InitConst(name, offset, r, int(r.Type().Width))
return
case ir.OMETHEXPR:
r := r.(*ir.SelectorExpr)
staticdata.InitAddr(name, offset, staticdata.FuncLinksym(r.FuncName()))
return
case ir.ONAME:
r := r.(*ir.Name)
if r.Offset_ != 0 {
base.Fatalf("genAsStatic %+v", as)
}
if r.Class == ir.PFUNC {
staticdata.InitAddr(name, offset, staticdata.FuncLinksym(r))
return
}
}
base.Fatalf("genAsStatic: rhs %v", as.Y)
}
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