go expr 源码
golang expr 代码
文件路径：/src/cmd/compile/internal/ir/expr.go
// Copyright 2020 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 ir
import (
"bytes"
"cmd/compile/internal/base"
"cmd/compile/internal/types"
"cmd/internal/obj"
"cmd/internal/src"
"fmt"
"go/constant"
"go/token"
)
// An Expr is a Node that can appear as an expression.
type Expr interface {
Node
isExpr()
}
// A miniExpr is a miniNode with extra fields common to expressions.
// TODO(rsc): Once we are sure about the contents, compact the bools
// into a bit field and leave extra bits available for implementations
// embedding miniExpr. Right now there are ~60 unused bits sitting here.
type miniExpr struct {
miniNode
typ *types.Type
init Nodes // TODO(rsc): Don't require every Node to have an init
flags bitset8
}
const (
miniExprNonNil = 1 << iota
miniExprTransient
miniExprBounded
miniExprImplicit // for use by implementations; not supported by every Expr
miniExprCheckPtr
)
func (*miniExpr) isExpr() {}
func (n *miniExpr) Type() *types.Type { return n.typ }
func (n *miniExpr) SetType(x *types.Type) { n.typ = x }
func (n *miniExpr) NonNil() bool { return n.flags&miniExprNonNil != 0 }
func (n *miniExpr) MarkNonNil() { n.flags |= miniExprNonNil }
func (n *miniExpr) Transient() bool { return n.flags&miniExprTransient != 0 }
func (n *miniExpr) SetTransient(b bool) { n.flags.set(miniExprTransient, b) }
func (n *miniExpr) Bounded() bool { return n.flags&miniExprBounded != 0 }
func (n *miniExpr) SetBounded(b bool) { n.flags.set(miniExprBounded, b) }
func (n *miniExpr) Init() Nodes { return n.init }
func (n *miniExpr) PtrInit() *Nodes { return &n.init }
func (n *miniExpr) SetInit(x Nodes) { n.init = x }
// An AddStringExpr is a string concatenation Expr[0] + Exprs[1] + ... + Expr[len(Expr)-1].
type AddStringExpr struct {
miniExpr
List Nodes
Prealloc *Name
}
func NewAddStringExpr(pos src.XPos, list []Node) *AddStringExpr {
n := &AddStringExpr{}
n.pos = pos
n.op = OADDSTR
n.List = list
return n
}
// An AddrExpr is an address-of expression &X.
// It may end up being a normal address-of or an allocation of a composite literal.
type AddrExpr struct {
miniExpr
X Node
Prealloc *Name // preallocated storage if any
}
func NewAddrExpr(pos src.XPos, x Node) *AddrExpr {
n := &AddrExpr{X: x}
n.op = OADDR
n.pos = pos
return n
}
func (n *AddrExpr) Implicit() bool { return n.flags&miniExprImplicit != 0 }
func (n *AddrExpr) SetImplicit(b bool) { n.flags.set(miniExprImplicit, b) }
func (n *AddrExpr) SetOp(op Op) {
switch op {
default:
panic(n.no("SetOp " + op.String()))
case OADDR, OPTRLIT:
n.op = op
}
}
// A BasicLit is a literal of basic type.
type BasicLit struct {
miniExpr
val constant.Value
}
func NewBasicLit(pos src.XPos, val constant.Value) Node {
n := &BasicLit{val: val}
n.op = OLITERAL
n.pos = pos
if k := val.Kind(); k != constant.Unknown {
n.SetType(idealType(k))
}
return n
}
func (n *BasicLit) Val() constant.Value { return n.val }
func (n *BasicLit) SetVal(val constant.Value) { n.val = val }
// A BinaryExpr is a binary expression X Op Y,
// or Op(X, Y) for builtin functions that do not become calls.
type BinaryExpr struct {
miniExpr
X Node
Y Node
}
func NewBinaryExpr(pos src.XPos, op Op, x, y Node) *BinaryExpr {
n := &BinaryExpr{X: x, Y: y}
n.pos = pos
n.SetOp(op)
return n
}
func (n *BinaryExpr) SetOp(op Op) {
switch op {
default:
panic(n.no("SetOp " + op.String()))
case OADD, OADDSTR, OAND, OANDNOT, ODIV, OEQ, OGE, OGT, OLE,
OLSH, OLT, OMOD, OMUL, ONE, OOR, ORSH, OSUB, OXOR,
OCOPY, OCOMPLEX, OUNSAFEADD, OUNSAFESLICE,
OEFACE:
n.op = op
}
}
// A CallExpr is a function call X(Args).
type CallExpr struct {
miniExpr
origNode
X Node
Args Nodes
KeepAlive []*Name // vars to be kept alive until call returns
IsDDD bool
NoInline bool
}
func NewCallExpr(pos src.XPos, op Op, fun Node, args []Node) *CallExpr {
n := &CallExpr{X: fun}
n.pos = pos
n.orig = n
n.SetOp(op)
n.Args = args
return n
}
func (*CallExpr) isStmt() {}
func (n *CallExpr) SetOp(op Op) {
switch op {
default:
panic(n.no("SetOp " + op.String()))
case OAPPEND,
OCALL, OCALLFUNC, OCALLINTER, OCALLMETH,
ODELETE,
OGETG, OGETCALLERPC, OGETCALLERSP,
OMAKE, OPRINT, OPRINTN,
ORECOVER, ORECOVERFP:
n.op = op
}
}
// A ClosureExpr is a function literal expression.
type ClosureExpr struct {
miniExpr
Func *Func `mknode:"-"`
Prealloc *Name
IsGoWrap bool // whether this is wrapper closure of a go statement
}
// A CompLitExpr is a composite literal Type{Vals}.
// Before type-checking, the type is Ntype.
type CompLitExpr struct {
miniExpr
origNode
List Nodes // initialized values
Prealloc *Name
// For OSLICELIT, Len is the backing array length.
// For OMAPLIT, Len is the number of entries that we've removed from List and
// generated explicit mapassign calls for. This is used to inform the map alloc hint.
Len int64
}
func NewCompLitExpr(pos src.XPos, op Op, typ *types.Type, list []Node) *CompLitExpr {
n := &CompLitExpr{List: list}
n.pos = pos
n.SetOp(op)
if typ != nil {
n.SetType(typ)
}
n.orig = n
return n
}
func (n *CompLitExpr) Implicit() bool { return n.flags&miniExprImplicit != 0 }
func (n *CompLitExpr) SetImplicit(b bool) { n.flags.set(miniExprImplicit, b) }
func (n *CompLitExpr) SetOp(op Op) {
switch op {
default:
panic(n.no("SetOp " + op.String()))
case OARRAYLIT, OCOMPLIT, OMAPLIT, OSTRUCTLIT, OSLICELIT:
n.op = op
}
}
type ConstExpr struct {
miniExpr
origNode
val constant.Value
}
func NewConstExpr(val constant.Value, orig Node) Node {
n := &ConstExpr{val: val}
n.op = OLITERAL
n.pos = orig.Pos()
n.orig = orig
n.SetType(orig.Type())
n.SetTypecheck(orig.Typecheck())
return n
}
func (n *ConstExpr) Sym() *types.Sym { return n.orig.Sym() }
func (n *ConstExpr) Val() constant.Value { return n.val }
// A ConvExpr is a conversion Type(X).
// It may end up being a value or a type.
type ConvExpr struct {
miniExpr
X Node
}
func NewConvExpr(pos src.XPos, op Op, typ *types.Type, x Node) *ConvExpr {
n := &ConvExpr{X: x}
n.pos = pos
n.typ = typ
n.SetOp(op)
return n
}
func (n *ConvExpr) Implicit() bool { return n.flags&miniExprImplicit != 0 }
func (n *ConvExpr) SetImplicit(b bool) { n.flags.set(miniExprImplicit, b) }
func (n *ConvExpr) CheckPtr() bool { return n.flags&miniExprCheckPtr != 0 }
func (n *ConvExpr) SetCheckPtr(b bool) { n.flags.set(miniExprCheckPtr, b) }
func (n *ConvExpr) SetOp(op Op) {
switch op {
default:
panic(n.no("SetOp " + op.String()))
case OCONV, OCONVIFACE, OCONVIDATA, OCONVNOP, OBYTES2STR, OBYTES2STRTMP, ORUNES2STR, OSTR2BYTES, OSTR2BYTESTMP, OSTR2RUNES, ORUNESTR, OSLICE2ARRPTR:
n.op = op
}
}
// An IndexExpr is an index expression X[Index].
type IndexExpr struct {
miniExpr
X Node
Index Node
Assigned bool
}
func NewIndexExpr(pos src.XPos, x, index Node) *IndexExpr {
n := &IndexExpr{X: x, Index: index}
n.pos = pos
n.op = OINDEX
return n
}
func (n *IndexExpr) SetOp(op Op) {
switch op {
default:
panic(n.no("SetOp " + op.String()))
case OINDEX, OINDEXMAP:
n.op = op
}
}
// A KeyExpr is a Key: Value composite literal key.
type KeyExpr struct {
miniExpr
Key Node
Value Node
}
func NewKeyExpr(pos src.XPos, key, value Node) *KeyExpr {
n := &KeyExpr{Key: key, Value: value}
n.pos = pos
n.op = OKEY
return n
}
// A StructKeyExpr is an Field: Value composite literal key.
type StructKeyExpr struct {
miniExpr
Field *types.Field
Value Node
}
func NewStructKeyExpr(pos src.XPos, field *types.Field, value Node) *StructKeyExpr {
n := &StructKeyExpr{Field: field, Value: value}
n.pos = pos
n.op = OSTRUCTKEY
return n
}
func (n *StructKeyExpr) Sym() *types.Sym { return n.Field.Sym }
// An InlinedCallExpr is an inlined function call.
type InlinedCallExpr struct {
miniExpr
Body Nodes
ReturnVars Nodes // must be side-effect free
}
func NewInlinedCallExpr(pos src.XPos, body, retvars []Node) *InlinedCallExpr {
n := &InlinedCallExpr{}
n.pos = pos
n.op = OINLCALL
n.Body = body
n.ReturnVars = retvars
return n
}
func (n *InlinedCallExpr) SingleResult() Node {
if have := len(n.ReturnVars); have != 1 {
base.FatalfAt(n.Pos(), "inlined call has %v results, expected 1", have)
}
if !n.Type().HasShape() && n.ReturnVars[0].Type().HasShape() {
// If the type of the call is not a shape, but the type of the return value
// is a shape, we need to do an implicit conversion, so the real type
// of n is maintained.
r := NewConvExpr(n.Pos(), OCONVNOP, n.Type(), n.ReturnVars[0])
r.SetTypecheck(1)
return r
}
return n.ReturnVars[0]
}
// A LogicalExpr is a expression X Op Y where Op is && or ||.
// It is separate from BinaryExpr to make room for statements
// that must be executed before Y but after X.
type LogicalExpr struct {
miniExpr
X Node
Y Node
}
func NewLogicalExpr(pos src.XPos, op Op, x, y Node) *LogicalExpr {
n := &LogicalExpr{X: x, Y: y}
n.pos = pos
n.SetOp(op)
return n
}
func (n *LogicalExpr) SetOp(op Op) {
switch op {
default:
panic(n.no("SetOp " + op.String()))
case OANDAND, OOROR:
n.op = op
}
}
// A MakeExpr is a make expression: make(Type[, Len[, Cap]]).
// Op is OMAKECHAN, OMAKEMAP, OMAKESLICE, or OMAKESLICECOPY,
// but *not* OMAKE (that's a pre-typechecking CallExpr).
type MakeExpr struct {
miniExpr
Len Node
Cap Node
}
func NewMakeExpr(pos src.XPos, op Op, len, cap Node) *MakeExpr {
n := &MakeExpr{Len: len, Cap: cap}
n.pos = pos
n.SetOp(op)
return n
}
func (n *MakeExpr) SetOp(op Op) {
switch op {
default:
panic(n.no("SetOp " + op.String()))
case OMAKECHAN, OMAKEMAP, OMAKESLICE, OMAKESLICECOPY:
n.op = op
}
}
// A NilExpr represents the predefined untyped constant nil.
// (It may be copied and assigned a type, though.)
type NilExpr struct {
miniExpr
}
func NewNilExpr(pos src.XPos) *NilExpr {
n := &NilExpr{}
n.pos = pos
n.op = ONIL
return n
}
// A ParenExpr is a parenthesized expression (X).
// It may end up being a value or a type.
type ParenExpr struct {
miniExpr
X Node
}
func NewParenExpr(pos src.XPos, x Node) *ParenExpr {
n := &ParenExpr{X: x}
n.op = OPAREN
n.pos = pos
return n
}
func (n *ParenExpr) Implicit() bool { return n.flags&miniExprImplicit != 0 }
func (n *ParenExpr) SetImplicit(b bool) { n.flags.set(miniExprImplicit, b) }
// A RawOrigExpr represents an arbitrary Go expression as a string value.
// When printed in diagnostics, the string value is written out exactly as-is.
type RawOrigExpr struct {
miniExpr
Raw string
}
func NewRawOrigExpr(pos src.XPos, op Op, raw string) *RawOrigExpr {
n := &RawOrigExpr{Raw: raw}
n.pos = pos
n.op = op
return n
}
// A ResultExpr represents a direct access to a result.
type ResultExpr struct {
miniExpr
Index int64 // index of the result expr.
}
func NewResultExpr(pos src.XPos, typ *types.Type, index int64) *ResultExpr {
n := &ResultExpr{Index: index}
n.pos = pos
n.op = ORESULT
n.typ = typ
return n
}
// A LinksymOffsetExpr refers to an offset within a global variable.
// It is like a SelectorExpr but without the field name.
type LinksymOffsetExpr struct {
miniExpr
Linksym *obj.LSym
Offset_ int64
}
func NewLinksymOffsetExpr(pos src.XPos, lsym *obj.LSym, offset int64, typ *types.Type) *LinksymOffsetExpr {
n := &LinksymOffsetExpr{Linksym: lsym, Offset_: offset}
n.typ = typ
n.op = OLINKSYMOFFSET
return n
}
// NewLinksymExpr is NewLinksymOffsetExpr, but with offset fixed at 0.
func NewLinksymExpr(pos src.XPos, lsym *obj.LSym, typ *types.Type) *LinksymOffsetExpr {
return NewLinksymOffsetExpr(pos, lsym, 0, typ)
}
// NewNameOffsetExpr is NewLinksymOffsetExpr, but taking a *Name
// representing a global variable instead of an *obj.LSym directly.
func NewNameOffsetExpr(pos src.XPos, name *Name, offset int64, typ *types.Type) *LinksymOffsetExpr {
if name == nil || IsBlank(name) || !(name.Op() == ONAME && name.Class == PEXTERN) {
base.FatalfAt(pos, "cannot take offset of nil, blank name or non-global variable: %v", name)
}
return NewLinksymOffsetExpr(pos, name.Linksym(), offset, typ)
}
// A SelectorExpr is a selector expression X.Sel.
type SelectorExpr struct {
miniExpr
X Node
// Sel is the name of the field or method being selected, without (in the
// case of methods) any preceding type specifier. If the field/method is
// exported, than the Sym uses the local package regardless of the package
// of the containing type.
Sel *types.Sym
// The actual selected field - may not be filled in until typechecking.
Selection *types.Field
Prealloc *Name // preallocated storage for OMETHVALUE, if any
}
func NewSelectorExpr(pos src.XPos, op Op, x Node, sel *types.Sym) *SelectorExpr {
n := &SelectorExpr{X: x, Sel: sel}
n.pos = pos
n.SetOp(op)
return n
}
func (n *SelectorExpr) SetOp(op Op) {
switch op {
default:
panic(n.no("SetOp " + op.String()))
case OXDOT, ODOT, ODOTPTR, ODOTMETH, ODOTINTER, OMETHVALUE, OMETHEXPR:
n.op = op
}
}
func (n *SelectorExpr) Sym() *types.Sym { return n.Sel }
func (n *SelectorExpr) Implicit() bool { return n.flags&miniExprImplicit != 0 }
func (n *SelectorExpr) SetImplicit(b bool) { n.flags.set(miniExprImplicit, b) }
func (n *SelectorExpr) Offset() int64 { return n.Selection.Offset }
func (n *SelectorExpr) FuncName() *Name {
if n.Op() != OMETHEXPR {
panic(n.no("FuncName"))
}
fn := NewNameAt(n.Selection.Pos, MethodSym(n.X.Type(), n.Sel))
fn.Class = PFUNC
fn.SetType(n.Type())
if n.Selection.Nname != nil {
// TODO(austin): Nname is nil for interface method
// expressions (I.M), so we can't attach a Func to
// those here. reflectdata.methodWrapper generates the
// Func.
fn.Func = n.Selection.Nname.(*Name).Func
}
return fn
}
// A SliceExpr is a slice expression X[Low:High] or X[Low:High:Max].
type SliceExpr struct {
miniExpr
X Node
Low Node
High Node
Max Node
}
func NewSliceExpr(pos src.XPos, op Op, x, low, high, max Node) *SliceExpr {
n := &SliceExpr{X: x, Low: low, High: high, Max: max}
n.pos = pos
n.op = op
return n
}
func (n *SliceExpr) SetOp(op Op) {
switch op {
default:
panic(n.no("SetOp " + op.String()))
case OSLICE, OSLICEARR, OSLICESTR, OSLICE3, OSLICE3ARR:
n.op = op
}
}
// IsSlice3 reports whether o is a slice3 op (OSLICE3, OSLICE3ARR).
// o must be a slicing op.
func (o Op) IsSlice3() bool {
switch o {
case OSLICE, OSLICEARR, OSLICESTR:
return false
case OSLICE3, OSLICE3ARR:
return true
}
base.Fatalf("IsSlice3 op %v", o)
return false
}
// A SliceHeader expression constructs a slice header from its parts.
type SliceHeaderExpr struct {
miniExpr
Ptr Node
Len Node
Cap Node
}
func NewSliceHeaderExpr(pos src.XPos, typ *types.Type, ptr, len, cap Node) *SliceHeaderExpr {
n := &SliceHeaderExpr{Ptr: ptr, Len: len, Cap: cap}
n.pos = pos
n.op = OSLICEHEADER
n.typ = typ
return n
}
// A StarExpr is a dereference expression *X.
// It may end up being a value or a type.
type StarExpr struct {
miniExpr
X Node
}
func NewStarExpr(pos src.XPos, x Node) *StarExpr {
n := &StarExpr{X: x}
n.op = ODEREF
n.pos = pos
return n
}
func (n *StarExpr) Implicit() bool { return n.flags&miniExprImplicit != 0 }
func (n *StarExpr) SetImplicit(b bool) { n.flags.set(miniExprImplicit, b) }
// A TypeAssertionExpr is a selector expression X.(Type).
// Before type-checking, the type is Ntype.
type TypeAssertExpr struct {
miniExpr
X Node
// Runtime type information provided by walkDotType for
// assertions from non-empty interface to concrete type.
ITab *AddrExpr `mknode:"-"` // *runtime.itab for Type implementing X's type
}
func NewTypeAssertExpr(pos src.XPos, x Node, typ *types.Type) *TypeAssertExpr {
n := &TypeAssertExpr{X: x}
n.pos = pos
n.op = ODOTTYPE
if typ != nil {
n.SetType(typ)
}
return n
}
func (n *TypeAssertExpr) SetOp(op Op) {
switch op {
default:
panic(n.no("SetOp " + op.String()))
case ODOTTYPE, ODOTTYPE2:
n.op = op
}
}
// A DynamicTypeAssertExpr asserts that X is of dynamic type RType.
type DynamicTypeAssertExpr struct {
miniExpr
X Node
// RType is an expression that yields a *runtime._type value
// representing the asserted type.
//
// BUG(mdempsky): If ITab is non-nil, RType may be nil.
RType Node
// ITab is an expression that yields a *runtime.itab value
// representing the asserted type within the assertee expression's
// original interface type.
//
// ITab is only used for assertions from non-empty interface type to
// a concrete (i.e., non-interface) type. For all other assertions,
// ITab is nil.
ITab Node
}
func NewDynamicTypeAssertExpr(pos src.XPos, op Op, x, rtype Node) *DynamicTypeAssertExpr {
n := &DynamicTypeAssertExpr{X: x, RType: rtype}
n.pos = pos
n.op = op
return n
}
func (n *DynamicTypeAssertExpr) SetOp(op Op) {
switch op {
default:
panic(n.no("SetOp " + op.String()))
case ODYNAMICDOTTYPE, ODYNAMICDOTTYPE2:
n.op = op
}
}
// A UnaryExpr is a unary expression Op X,
// or Op(X) for a builtin function that does not end up being a call.
type UnaryExpr struct {
miniExpr
X Node
}
func NewUnaryExpr(pos src.XPos, op Op, x Node) *UnaryExpr {
n := &UnaryExpr{X: x}
n.pos = pos
n.SetOp(op)
return n
}
func (n *UnaryExpr) SetOp(op Op) {
switch op {
default:
panic(n.no("SetOp " + op.String()))
case OBITNOT, ONEG, ONOT, OPLUS, ORECV,
OALIGNOF, OCAP, OCLOSE, OIMAG, OLEN, ONEW,
OOFFSETOF, OPANIC, OREAL, OSIZEOF,
OCHECKNIL, OCFUNC, OIDATA, OITAB, OSPTR, OVARDEF, OVARKILL, OVARLIVE:
n.op = op
}
}
// Probably temporary: using Implicit() flag to mark generic function nodes that
// are called to make getGfInfo analysis easier in one pre-order pass.
func (n *InstExpr) Implicit() bool { return n.flags&miniExprImplicit != 0 }
func (n *InstExpr) SetImplicit(b bool) { n.flags.set(miniExprImplicit, b) }
// An InstExpr is a generic function or type instantiation.
type InstExpr struct {
miniExpr
X Node
Targs []Ntype
}
func NewInstExpr(pos src.XPos, op Op, x Node, targs []Ntype) *InstExpr {
n := &InstExpr{X: x, Targs: targs}
n.pos = pos
n.op = op
return n
}
func IsZero(n Node) bool {
switch n.Op() {
case ONIL:
return true
case OLITERAL:
switch u := n.Val(); u.Kind() {
case constant.String:
return constant.StringVal(u) == ""
case constant.Bool:
return !constant.BoolVal(u)
default:
return constant.Sign(u) == 0
}
case OARRAYLIT:
n := n.(*CompLitExpr)
for _, n1 := range n.List {
if n1.Op() == OKEY {
n1 = n1.(*KeyExpr).Value
}
if !IsZero(n1) {
return false
}
}
return true
case OSTRUCTLIT:
n := n.(*CompLitExpr)
for _, n1 := range n.List {
n1 := n1.(*StructKeyExpr)
if !IsZero(n1.Value) {
return false
}
}
return true
}
return false
}
// lvalue etc
func IsAddressable(n Node) bool {
switch n.Op() {
case OINDEX:
n := n.(*IndexExpr)
if n.X.Type() != nil && n.X.Type().IsArray() {
return IsAddressable(n.X)
}
if n.X.Type() != nil && n.X.Type().IsString() {
return false
}
fallthrough
case ODEREF, ODOTPTR:
return true
case ODOT:
n := n.(*SelectorExpr)
return IsAddressable(n.X)
case ONAME:
n := n.(*Name)
if n.Class == PFUNC {
return false
}
return true
case OLINKSYMOFFSET:
return true
}
return false
}
func StaticValue(n Node) Node {
for {
if n.Op() == OCONVNOP {
n = n.(*ConvExpr).X
continue
}
if n.Op() == OINLCALL {
n = n.(*InlinedCallExpr).SingleResult()
continue
}
n1 := staticValue1(n)
if n1 == nil {
return n
}
n = n1
}
}
// staticValue1 implements a simple SSA-like optimization. If n is a local variable
// that is initialized and never reassigned, staticValue1 returns the initializer
// expression. Otherwise, it returns nil.
func staticValue1(nn Node) Node {
if nn.Op() != ONAME {
return nil
}
n := nn.(*Name)
if n.Class != PAUTO {
return nil
}
defn := n.Defn
if defn == nil {
return nil
}
var rhs Node
FindRHS:
switch defn.Op() {
case OAS:
defn := defn.(*AssignStmt)
rhs = defn.Y
case OAS2:
defn := defn.(*AssignListStmt)
for i, lhs := range defn.Lhs {
if lhs == n {
rhs = defn.Rhs[i]
break FindRHS
}
}
base.Fatalf("%v missing from LHS of %v", n, defn)
default:
return nil
}
if rhs == nil {
base.Fatalf("RHS is nil: %v", defn)
}
if reassigned(n) {
return nil
}
return rhs
}
// reassigned takes an ONAME node, walks the function in which it is defined, and returns a boolean
// indicating whether the name has any assignments other than its declaration.
// The second return value is the first such assignment encountered in the walk, if any. It is mostly
// useful for -m output documenting the reason for inhibited optimizations.
// NB: global variables are always considered to be re-assigned.
// TODO: handle initial declaration not including an assignment and followed by a single assignment?
func reassigned(name *Name) bool {
if name.Op() != ONAME {
base.Fatalf("reassigned %v", name)
}
// no way to reliably check for no-reassignment of globals, assume it can be
if name.Curfn == nil {
return true
}
// TODO(mdempsky): This is inefficient and becoming increasingly
// unwieldy. Figure out a way to generalize escape analysis's
// reassignment detection for use by inlining and devirtualization.
// isName reports whether n is a reference to name.
isName := func(x Node) bool {
n, ok := x.(*Name)
return ok && n.Canonical() == name
}
var do func(n Node) bool
do = func(n Node) bool {
switch n.Op() {
case OAS:
n := n.(*AssignStmt)
if isName(n.X) && n != name.Defn {
return true
}
case OAS2, OAS2FUNC, OAS2MAPR, OAS2DOTTYPE, OAS2RECV, OSELRECV2:
n := n.(*AssignListStmt)
for _, p := range n.Lhs {
if isName(p) && n != name.Defn {
return true
}
}
case OADDR:
n := n.(*AddrExpr)
if isName(OuterValue(n.X)) {
return true
}
case OCLOSURE:
n := n.(*ClosureExpr)
if Any(n.Func, do) {
return true
}
}
return false
}
return Any(name.Curfn, do)
}
// IsIntrinsicCall reports whether the compiler back end will treat the call as an intrinsic operation.
var IsIntrinsicCall = func(*CallExpr) bool { return false }
// SameSafeExpr checks whether it is safe to reuse one of l and r
// instead of computing both. SameSafeExpr assumes that l and r are
// used in the same statement or expression. In order for it to be
// safe to reuse l or r, they must:
// - be the same expression
// - not have side-effects (no function calls, no channel ops);
// however, panics are ok
// - not cause inappropriate aliasing; e.g. two string to []byte
// conversions, must result in two distinct slices
//
// The handling of OINDEXMAP is subtle. OINDEXMAP can occur both
// as an lvalue (map assignment) and an rvalue (map access). This is
// currently OK, since the only place SameSafeExpr gets used on an
// lvalue expression is for OSLICE and OAPPEND optimizations, and it
// is correct in those settings.
func SameSafeExpr(l Node, r Node) bool {
for l.Op() == OCONVNOP {
l = l.(*ConvExpr).X
}
for r.Op() == OCONVNOP {
r = r.(*ConvExpr).X
}
if l.Op() != r.Op() || !types.Identical(l.Type(), r.Type()) {
return false
}
switch l.Op() {
case ONAME:
return l == r
case ODOT, ODOTPTR:
l := l.(*SelectorExpr)
r := r.(*SelectorExpr)
return l.Sel != nil && r.Sel != nil && l.Sel == r.Sel && SameSafeExpr(l.X, r.X)
case ODEREF:
l := l.(*StarExpr)
r := r.(*StarExpr)
return SameSafeExpr(l.X, r.X)
case ONOT, OBITNOT, OPLUS, ONEG:
l := l.(*UnaryExpr)
r := r.(*UnaryExpr)
return SameSafeExpr(l.X, r.X)
case OCONV:
l := l.(*ConvExpr)
r := r.(*ConvExpr)
// Some conversions can't be reused, such as []byte(str).
// Allow only numeric-ish types. This is a bit conservative.
return types.IsSimple[l.Type().Kind()] && SameSafeExpr(l.X, r.X)
case OINDEX, OINDEXMAP:
l := l.(*IndexExpr)
r := r.(*IndexExpr)
return SameSafeExpr(l.X, r.X) && SameSafeExpr(l.Index, r.Index)
case OADD, OSUB, OOR, OXOR, OMUL, OLSH, ORSH, OAND, OANDNOT, ODIV, OMOD:
l := l.(*BinaryExpr)
r := r.(*BinaryExpr)
return SameSafeExpr(l.X, r.X) && SameSafeExpr(l.Y, r.Y)
case OLITERAL:
return constant.Compare(l.Val(), token.EQL, r.Val())
case ONIL:
return true
}
return false
}
// ShouldCheckPtr reports whether pointer checking should be enabled for
// function fn at a given level. See debugHelpFooter for defined
// levels.
func ShouldCheckPtr(fn *Func, level int) bool {
return base.Debug.Checkptr >= level && fn.Pragma&NoCheckPtr == 0
}
// ShouldAsanCheckPtr reports whether pointer checking should be enabled for
// function fn when -asan is enabled.
func ShouldAsanCheckPtr(fn *Func) bool {
return base.Flag.ASan && fn.Pragma&NoCheckPtr == 0
}
// IsReflectHeaderDataField reports whether l is an expression p.Data
// where p has type reflect.SliceHeader or reflect.StringHeader.
func IsReflectHeaderDataField(l Node) bool {
if l.Type() != types.Types[types.TUINTPTR] {
return false
}
var tsym *types.Sym
switch l.Op() {
case ODOT:
l := l.(*SelectorExpr)
tsym = l.X.Type().Sym()
case ODOTPTR:
l := l.(*SelectorExpr)
tsym = l.X.Type().Elem().Sym()
default:
return false
}
if tsym == nil || l.Sym().Name != "Data" || tsym.Pkg.Path != "reflect" {
return false
}
return tsym.Name == "SliceHeader" || tsym.Name == "StringHeader"
}
func ParamNames(ft *types.Type) []Node {
args := make([]Node, ft.NumParams())
for i, f := range ft.Params().FieldSlice() {
args[i] = AsNode(f.Nname)
}
return args
}
// MethodSym returns the method symbol representing a method name
// associated with a specific receiver type.
//
// Method symbols can be used to distinguish the same method appearing
// in different method sets. For example, T.M and (*T).M have distinct
// method symbols.
//
// The returned symbol will be marked as a function.
func MethodSym(recv *types.Type, msym *types.Sym) *types.Sym {
sym := MethodSymSuffix(recv, msym, "")
sym.SetFunc(true)
return sym
}
// MethodSymSuffix is like methodsym, but allows attaching a
// distinguisher suffix. To avoid collisions, the suffix must not
// start with a letter, number, or period.
func MethodSymSuffix(recv *types.Type, msym *types.Sym, suffix string) *types.Sym {
if msym.IsBlank() {
base.Fatalf("blank method name")
}
rsym := recv.Sym()
if recv.IsPtr() {
if rsym != nil {
base.Fatalf("declared pointer receiver type: %v", recv)
}
rsym = recv.Elem().Sym()
}
// Find the package the receiver type appeared in. For
// anonymous receiver types (i.e., anonymous structs with
// embedded fields), use the "go" pseudo-package instead.
rpkg := Pkgs.Go
if rsym != nil {
rpkg = rsym.Pkg
}
var b bytes.Buffer
if recv.IsPtr() {
// The parentheses aren't really necessary, but
// they're pretty traditional at this point.
fmt.Fprintf(&b, "(%-S)", recv)
} else {
fmt.Fprintf(&b, "%-S", recv)
}
// A particular receiver type may have multiple non-exported
// methods with the same name. To disambiguate them, include a
// package qualifier for names that came from a different
// package than the receiver type.
if !types.IsExported(msym.Name) && msym.Pkg != rpkg {
b.WriteString(".")
b.WriteString(msym.Pkg.Prefix)
}
b.WriteString(".")
b.WriteString(msym.Name)
b.WriteString(suffix)
return rpkg.LookupBytes(b.Bytes())
}
// MethodExprName returns the ONAME representing the method
// referenced by expression n, which must be a method selector,
// method expression, or method value.
func MethodExprName(n Node) *Name {
name, _ := MethodExprFunc(n).Nname.(*Name)
return name
}
// MethodExprFunc is like MethodExprName, but returns the types.Field instead.
func MethodExprFunc(n Node) *types.Field {
switch n.Op() {
case ODOTMETH, OMETHEXPR, OMETHVALUE:
return n.(*SelectorExpr).Selection
}
base.Fatalf("unexpected node: %v (%v)", n, n.Op())
panic("unreachable")
}
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