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// 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 (
"cmd/compile/internal/base"
"cmd/internal/src"
)
// A Node may implement the Orig and SetOrig method to
// maintain a pointer to the "unrewritten" form of a Node.
// If a Node does not implement OrigNode, it is its own Orig.
//
// Note that both SepCopy and Copy have definitions compatible
// with a Node that does not implement OrigNode: such a Node
// is its own Orig, and in that case, that's what both want to return
// anyway (SepCopy unconditionally, and Copy only when the input
// is its own Orig as well, but if the output does not implement
// OrigNode, then neither does the input, making the condition true).
type OrigNode interface {
Node
Orig() Node
SetOrig(Node)
}
// origNode may be embedded into a Node to make it implement OrigNode.
type origNode struct {
orig Node `mknode:"-"`
}
func (n *origNode) Orig() Node { return n.orig }
func (n *origNode) SetOrig(o Node) { n.orig = o }
// Orig returns the “original” node for n.
// If n implements OrigNode, Orig returns n.Orig().
// Otherwise Orig returns n itself.
func Orig(n Node) Node {
if n, ok := n.(OrigNode); ok {
o := n.Orig()
if o == nil {
Dump("Orig nil", n)
base.Fatalf("Orig returned nil")
}
return o
}
return n
}
// SepCopy returns a separate shallow copy of n,
// breaking any Orig link to any other nodes.
func SepCopy(n Node) Node {
n = n.copy()
if n, ok := n.(OrigNode); ok {
n.SetOrig(n)
}
return n
}
// Copy returns a shallow copy of n.
// If Orig(n) == n, then Orig(Copy(n)) == the copy.
// Otherwise the Orig link is preserved as well.
//
// The specific semantics surrounding Orig are subtle but right for most uses.
// See issues #26855 and #27765 for pitfalls.
func Copy(n Node) Node {
c := n.copy()
if n, ok := n.(OrigNode); ok && n.Orig() == n {
c.(OrigNode).SetOrig(c)
}
return c
}
// DeepCopy returns a “deep” copy of n, with its entire structure copied
// (except for shared nodes like ONAME, ONONAME, OLITERAL, and OTYPE).
// If pos.IsKnown(), it sets the source position of newly allocated Nodes to pos.
func DeepCopy(pos src.XPos, n Node) Node {
var edit func(Node) Node
edit = func(x Node) Node {
switch x.Op() {
case OPACK, ONAME, ONONAME, OLITERAL, ONIL, OTYPE:
return x
}
x = Copy(x)
if pos.IsKnown() {
x.SetPos(pos)
}
EditChildren(x, edit)
return x
}
return edit(n)
}
// DeepCopyList returns a list of deep copies (using DeepCopy) of the nodes in list.
func DeepCopyList(pos src.XPos, list []Node) []Node {
var out []Node
for _, n := range list {
out = append(out, DeepCopy(pos, n))
}
return out
}
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