mini.go

     1  // Copyright 2020 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:generate go run mknode.go
     6  
     7  package ir
     8  
     9  import (
    10  	"cmd/compile/internal/types"
    11  	"cmd/internal/src"
    12  	"fmt"
    13  	"go/constant"
    14  )
    15  
    16  // A miniNode is a minimal node implementation,
    17  // meant to be embedded as the first field in a larger node implementation,
    18  // at a cost of 12 bytes.
    19  //
    20  // A miniNode is NOT a valid Node by itself: the embedding struct
    21  // must at the least provide:
    22  //
    23  //	func (n *MyNode) String() string { return fmt.Sprint(n) }
    24  //	func (n *MyNode) rawCopy() Node { c := *n; return &c }
    25  //	func (n *MyNode) Format(s fmt.State, verb rune) { FmtNode(n, s, verb) }
    26  //
    27  // The embedding struct should also fill in n.op in its constructor,
    28  // for more useful panic messages when invalid methods are called,
    29  // instead of implementing Op itself.
    30  type miniNode struct {
    31  	pos  src.XPos
    32  	op   Op
    33  	bits bitset8
    34  	esc  uint16
    35  }
    36  
    37  // op can be read, but not written.
    38  // An embedding implementation can provide a SetOp if desired.
    39  // (The panicking SetOp is with the other panics below.)
    40  func (n *miniNode) Op() Op            { return n.op }
    41  func (n *miniNode) Pos() src.XPos     { return n.pos }
    42  func (n *miniNode) SetPos(x src.XPos) { n.pos = x }
    43  func (n *miniNode) Esc() uint16       { return n.esc }
    44  func (n *miniNode) SetEsc(x uint16)   { n.esc = x }
    45  
    46  const (
    47  	miniTypecheckShift = 0
    48  	miniWalked         = 1 << 2 // to prevent/catch re-walking
    49  )
    50  
    51  func (n *miniNode) Typecheck() uint8 { return n.bits.get2(miniTypecheckShift) }
    52  func (n *miniNode) SetTypecheck(x uint8) {
    53  	if x > 2 {
    54  		panic(fmt.Sprintf("cannot SetTypecheck %d", x))
    55  	}
    56  	n.bits.set2(miniTypecheckShift, x)
    57  }
    58  
    59  func (n *miniNode) Walked() bool     { return n.bits&miniWalked != 0 }
    60  func (n *miniNode) SetWalked(x bool) { n.bits.set(miniWalked, x) }
    61  
    62  // Empty, immutable graph structure.
    63  
    64  func (n *miniNode) Init() Nodes { return Nodes{} }
    65  
    66  // Additional functionality unavailable.
    67  
    68  func (n *miniNode) no(name string) string { return "cannot " + name + " on " + n.op.String() }
    69  
    70  func (n *miniNode) Type() *types.Type       { return nil }
    71  func (n *miniNode) SetType(*types.Type)     { panic(n.no("SetType")) }
    72  func (n *miniNode) Name() *Name             { return nil }
    73  func (n *miniNode) Sym() *types.Sym         { return nil }
    74  func (n *miniNode) Val() constant.Value     { panic(n.no("Val")) }
    75  func (n *miniNode) SetVal(v constant.Value) { panic(n.no("SetVal")) }
    76  func (n *miniNode) NonNil() bool            { return false }
    77  func (n *miniNode) MarkNonNil()             { panic(n.no("MarkNonNil")) }
    78
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