src/cmd/compile/internal/ssa/value.go - go - Git at Google

 // Copyright 2015 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

 import (
 	"cmd/compile/internal/types"
 	"cmd/internal/src"
 	"fmt"
 	"math"
 	"sort"
 	"strings"
 )

 // A Value represents a value in the SSA representation of the program.
 // The ID and Type fields must not be modified. The remainder may be modified
 // if they preserve the value of the Value (e.g. changing a (mul 2 x) to an (add x x)).
 type Value struct {
 	// A unique identifier for the value. For performance we allocate these IDs
 	// densely starting at 1.  There is no guarantee that there won't be occasional holes, though.
 	ID ID

 	// The operation that computes this value. See op.go.
 	Op Op

 	// The type of this value. Normally this will be a Go type, but there
 	// are a few other pseudo-types, see ../types/type.go.
 	Type *types.Type

 	// Auxiliary info for this value. The type of this information depends on the opcode and type.
 	// AuxInt is used for integer values, Aux is used for other values.
 	// Floats are stored in AuxInt using math.Float64bits(f).
 	// Unused portions of AuxInt are filled by sign-extending the used portion,
 	// even if the represented value is unsigned.
 	// Users of AuxInt which interpret AuxInt as unsigned (e.g. shifts) must be careful.
 	// Use Value.AuxUnsigned to get the zero-extended value of AuxInt.
 	AuxInt int64
 	Aux    interface{}

 	// Arguments of this value
 	Args []*Value

 	// Containing basic block
 	Block *Block

 	// Source position
 	Pos src.XPos

 	// Use count. Each appearance in Value.Args and Block.Control counts once.
 	Uses int32

 	// wasm: Value stays on the WebAssembly stack. This value will not get a "register" (WebAssembly variable)
 	// nor a slot on Go stack, and the generation of this value is delayed to its use time.
 	OnWasmStack bool

 	// Storage for the first three args
 	argstorage [3]*Value
 }

 // Examples:
 // Opcode          aux   args
 //  OpAdd          nil      2
 //  OpConst     string      0    string constant
 //  OpConst      int64      0    int64 constant
 //  OpAddcq      int64      1    amd64 op: v = arg[0] + constant

 // short form print. Just v#.
 func (v *Value) String() string {
 	if v == nil {
 		return "nil" // should never happen, but not panicking helps with debugging
 	}
 	return fmt.Sprintf("v%d", v.ID)
 }

 func (v *Value) AuxInt8() int8 {
 	if opcodeTable[v.Op].auxType != auxInt8 {
 		v.Fatalf("op %s doesn't have an int8 aux field", v.Op)
 	}
 	return int8(v.AuxInt)
 }

 func (v *Value) AuxInt16() int16 {
 	if opcodeTable[v.Op].auxType != auxInt16 {
 		v.Fatalf("op %s doesn't have an int16 aux field", v.Op)
 	}
 	return int16(v.AuxInt)
 }

 func (v *Value) AuxInt32() int32 {
 	if opcodeTable[v.Op].auxType != auxInt32 {
 		v.Fatalf("op %s doesn't have an int32 aux field", v.Op)
 	}
 	return int32(v.AuxInt)
 }

 // AuxUnsigned returns v.AuxInt as an unsigned value for OpConst*.
 // v.AuxInt is always sign-extended to 64 bits, even if the
 // represented value is unsigned. This undoes that sign extension.
 func (v *Value) AuxUnsigned() uint64 {
 	c := v.AuxInt
 	switch v.Op {
 	case OpConst64:
 		return uint64(c)
 	case OpConst32:
 		return uint64(uint32(c))
 	case OpConst16:
 		return uint64(uint16(c))
 	case OpConst8:
 		return uint64(uint8(c))
 	}
 	v.Fatalf("op %s isn't OpConst*", v.Op)
 	return 0
 }

 func (v *Value) AuxFloat() float64 {
 	if opcodeTable[v.Op].auxType != auxFloat32 && opcodeTable[v.Op].auxType != auxFloat64 {
 		v.Fatalf("op %s doesn't have a float aux field", v.Op)
 	}
 	return math.Float64frombits(uint64(v.AuxInt))
 }
 func (v *Value) AuxValAndOff() ValAndOff {
 	if opcodeTable[v.Op].auxType != auxSymValAndOff {
 		v.Fatalf("op %s doesn't have a ValAndOff aux field", v.Op)
 	}
 	return ValAndOff(v.AuxInt)
 }

 // long form print.  v# = opcode <type> [aux] args [: reg] (names)
 func (v *Value) LongString() string {
 	s := fmt.Sprintf("v%d = %s", v.ID, v.Op)
 	s += " <" + v.Type.String() + ">"
 	s += v.auxString()
 	for _, a := range v.Args {
 		s += fmt.Sprintf(" %v", a)
 	}
 	var r []Location
 	if v.Block != nil {
 		r = v.Block.Func.RegAlloc
 	}
 	if int(v.ID) < len(r) && r[v.ID] != nil {
 		s += " : " + r[v.ID].String()
 	}
 	var names []string
 	if v.Block != nil {
 		for name, values := range v.Block.Func.NamedValues {
 			for _, value := range values {
 				if value == v {
 					names = append(names, name.String())
 					break // drop duplicates.
 				}
 			}
 		}
 	}
 	if len(names) != 0 {
 		sort.Strings(names) // Otherwise a source of variation in debugging output.
 		s += " (" + strings.Join(names, ", ") + ")"
 	}
 	return s
 }

 func (v *Value) auxString() string {
 	switch opcodeTable[v.Op].auxType {
 	case auxBool:
 		if v.AuxInt == 0 {
 			return " [false]"
 		} else {
 			return " [true]"
 		}
 	case auxInt8:
 		return fmt.Sprintf(" [%d]", v.AuxInt8())
 	case auxInt16:
 		return fmt.Sprintf(" [%d]", v.AuxInt16())
 	case auxInt32:
 		return fmt.Sprintf(" [%d]", v.AuxInt32())
 	case auxInt64, auxInt128:
 		return fmt.Sprintf(" [%d]", v.AuxInt)
 	case auxFloat32, auxFloat64:
 		return fmt.Sprintf(" [%g]", v.AuxFloat())
 	case auxString:
 		return fmt.Sprintf(" {%q}", v.Aux)
 	case auxSym, auxTyp:
 		if v.Aux != nil {
 			return fmt.Sprintf(" {%v}", v.Aux)
 		}
 	case auxSymOff, auxSymInt32, auxTypSize:
 		s := ""
 		if v.Aux != nil {
 			s = fmt.Sprintf(" {%v}", v.Aux)
 		}
 		if v.AuxInt != 0 {
 			s += fmt.Sprintf(" [%v]", v.AuxInt)
 		}
 		return s
 	case auxSymValAndOff:
 		s := ""
 		if v.Aux != nil {
 			s = fmt.Sprintf(" {%v}", v.Aux)
 		}
 		return s + fmt.Sprintf(" [%s]", v.AuxValAndOff())
 	case auxCCop:
 		return fmt.Sprintf(" {%s}", v.Aux.(Op))
 	}
 	return ""
 }

 // If/when midstack inlining is enabled (-l=4), the compiler gets both larger and slower.
 // Not-inlining this method is a help (*Value.reset and *Block.NewValue0 are similar).
 //go:noinline
 func (v *Value) AddArg(w *Value) {
 	if v.Args == nil {
 		v.resetArgs() // use argstorage
 	}
 	v.Args = append(v.Args, w)
 	w.Uses++
 }
 func (v *Value) AddArgs(a ...*Value) {
 	if v.Args == nil {
 		v.resetArgs() // use argstorage
 	}
 	v.Args = append(v.Args, a...)
 	for _, x := range a {
 		x.Uses++
 	}
 }
 func (v *Value) SetArg(i int, w *Value) {
 	v.Args[i].Uses--
 	v.Args[i] = w
 	w.Uses++
 }
 func (v *Value) RemoveArg(i int) {
 	v.Args[i].Uses--
 	copy(v.Args[i:], v.Args[i+1:])
 	v.Args[len(v.Args)-1] = nil // aid GC
 	v.Args = v.Args[:len(v.Args)-1]
 }
 func (v *Value) SetArgs1(a *Value) {
 	v.resetArgs()
 	v.AddArg(a)
 }
 func (v *Value) SetArgs2(a *Value, b *Value) {
 	v.resetArgs()
 	v.AddArg(a)
 	v.AddArg(b)
 }

 func (v *Value) resetArgs() {
 	for _, a := range v.Args {
 		a.Uses--
 	}
 	v.argstorage[0] = nil
 	v.argstorage[1] = nil
 	v.argstorage[2] = nil
 	v.Args = v.argstorage[:0]
 }

 func (v *Value) reset(op Op) {
 	v.Op = op
 	if op != OpCopy && notStmtBoundary(op) {
 		// Special case for OpCopy because of how it is used in rewrite
 		v.Pos = v.Pos.WithNotStmt()
 	}
 	v.resetArgs()
 	v.AuxInt = 0
 	v.Aux = nil
 }

 // copyInto makes a new value identical to v and adds it to the end of b.
 func (v *Value) copyInto(b *Block) *Value {
 	c := b.NewValue0(v.Pos.WithNotStmt(), v.Op, v.Type) // Lose the position, this causes line number churn otherwise.
 	c.Aux = v.Aux
 	c.AuxInt = v.AuxInt
 	c.AddArgs(v.Args...)
 	for _, a := range v.Args {
 		if a.Type.IsMemory() {
 			v.Fatalf("can't move a value with a memory arg %s", v.LongString())
 		}
 	}
 	return c
 }

 // copyIntoWithXPos makes a new value identical to v and adds it to the end of b.
 // The supplied position is used as the position of the new value.
 func (v *Value) copyIntoWithXPos(b *Block, pos src.XPos) *Value {
 	c := b.NewValue0(pos, v.Op, v.Type)
 	c.Aux = v.Aux
 	c.AuxInt = v.AuxInt
 	c.AddArgs(v.Args...)
 	for _, a := range v.Args {
 		if a.Type.IsMemory() {
 			v.Fatalf("can't move a value with a memory arg %s", v.LongString())
 		}
 	}
 	return c
 }

 func (v *Value) Logf(msg string, args ...interface{}) { v.Block.Logf(msg, args...) }
 func (v *Value) Log() bool                            { return v.Block.Log() }
 func (v *Value) Fatalf(msg string, args ...interface{}) {
 	v.Block.Func.fe.Fatalf(v.Pos, msg, args...)
 }

 // isGenericIntConst reports whether v is a generic integer constant.
 func (v *Value) isGenericIntConst() bool {
 	return v != nil && (v.Op == OpConst64 || v.Op == OpConst32 || v.Op == OpConst16 || v.Op == OpConst8)
 }

 // Reg returns the register assigned to v, in cmd/internal/obj/$ARCH numbering.
 func (v *Value) Reg() int16 {
 	reg := v.Block.Func.RegAlloc[v.ID]
 	if reg == nil {
 		v.Fatalf("nil register for value: %s\n%s\n", v.LongString(), v.Block.Func)
 	}
 	return reg.(*Register).objNum
 }

 // Reg0 returns the register assigned to the first output of v, in cmd/internal/obj/$ARCH numbering.
 func (v *Value) Reg0() int16 {
 	reg := v.Block.Func.RegAlloc[v.ID].(LocPair)[0]
 	if reg == nil {
 		v.Fatalf("nil first register for value: %s\n%s\n", v.LongString(), v.Block.Func)
 	}
 	return reg.(*Register).objNum
 }

 // Reg1 returns the register assigned to the second output of v, in cmd/internal/obj/$ARCH numbering.
 func (v *Value) Reg1() int16 {
 	reg := v.Block.Func.RegAlloc[v.ID].(LocPair)[1]
 	if reg == nil {
 		v.Fatalf("nil second register for value: %s\n%s\n", v.LongString(), v.Block.Func)
 	}
 	return reg.(*Register).objNum
 }

 func (v *Value) RegName() string {
 	reg := v.Block.Func.RegAlloc[v.ID]
 	if reg == nil {
 		v.Fatalf("nil register for value: %s\n%s\n", v.LongString(), v.Block.Func)
 	}
 	return reg.(*Register).name
 }

 // MemoryArg returns the memory argument for the Value.
 // The returned value, if non-nil, will be memory-typed (or a tuple with a memory-typed second part).
 // Otherwise, nil is returned.
 func (v *Value) MemoryArg() *Value {
 	if v.Op == OpPhi {
 		v.Fatalf("MemoryArg on Phi")
 	}
 	na := len(v.Args)
 	if na == 0 {
 		return nil
 	}
 	if m := v.Args[na-1]; m.Type.IsMemory() {
 		return m
 	}
 	return nil
 }

 // LackingPos indicates whether v is a value that is unlikely to have a correct
 // position assigned to it.  Ignoring such values leads to more user-friendly positions
 // assigned to nearby values and the blocks containing them.
 func (v *Value) LackingPos() bool {
 	// The exact definition of LackingPos is somewhat heuristically defined and may change
 	// in the future, for example if some of these operations are generated more carefully
 	// with respect to their source position.
 	return v.Op == OpVarDef || v.Op == OpVarKill || v.Op == OpVarLive || v.Op == OpPhi ||
 		(v.Op == OpFwdRef || v.Op == OpCopy) && v.Type == types.TypeMem
 }
	// Copyright 2015 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

	import (
	"cmd/compile/internal/types"
	"cmd/internal/src"
	"fmt"
	"math"
	"sort"
	"strings"
	)

	// A Value represents a value in the SSA representation of the program.
	// The ID and Type fields must not be modified. The remainder may be modified
	// if they preserve the value of the Value (e.g. changing a (mul 2 x) to an (add x x)).
	type Value struct {
	// A unique identifier for the value. For performance we allocate these IDs
	// densely starting at 1. There is no guarantee that there won't be occasional holes, though.
	ID ID

	// The operation that computes this value. See op.go.
	Op Op

	// The type of this value. Normally this will be a Go type, but there
	// are a few other pseudo-types, see ../types/type.go.
	Type *types.Type

	// Auxiliary info for this value. The type of this information depends on the opcode and type.
	// AuxInt is used for integer values, Aux is used for other values.
	// Floats are stored in AuxInt using math.Float64bits(f).
	// Unused portions of AuxInt are filled by sign-extending the used portion,
	// even if the represented value is unsigned.
	// Users of AuxInt which interpret AuxInt as unsigned (e.g. shifts) must be careful.
	// Use Value.AuxUnsigned to get the zero-extended value of AuxInt.
	AuxInt int64
	Aux interface{}

	// Arguments of this value
	Args []*Value

	// Containing basic block
	Block *Block

	// Source position
	Pos src.XPos

	// Use count. Each appearance in Value.Args and Block.Control counts once.
	Uses int32

	// wasm: Value stays on the WebAssembly stack. This value will not get a "register" (WebAssembly variable)
	// nor a slot on Go stack, and the generation of this value is delayed to its use time.
	OnWasmStack bool

	// Storage for the first three args
	argstorage [3]*Value
	}

	// Examples:
	// Opcode aux args
	// OpAdd nil 2
	// OpConst string 0 string constant
	// OpConst int64 0 int64 constant
	// OpAddcq int64 1 amd64 op: v = arg[0] + constant

	// short form print. Just v#.
	func (v *Value) String() string {
	if v == nil {
	return "nil" // should never happen, but not panicking helps with debugging
	}
	return fmt.Sprintf("v%d", v.ID)
	}

	func (v *Value) AuxInt8() int8 {
	if opcodeTable[v.Op].auxType != auxInt8 {
	v.Fatalf("op %s doesn't have an int8 aux field", v.Op)
	}
	return int8(v.AuxInt)
	}

	func (v *Value) AuxInt16() int16 {
	if opcodeTable[v.Op].auxType != auxInt16 {
	v.Fatalf("op %s doesn't have an int16 aux field", v.Op)
	}
	return int16(v.AuxInt)
	}

	func (v *Value) AuxInt32() int32 {
	if opcodeTable[v.Op].auxType != auxInt32 {
	v.Fatalf("op %s doesn't have an int32 aux field", v.Op)
	}
	return int32(v.AuxInt)
	}

	// AuxUnsigned returns v.AuxInt as an unsigned value for OpConst*.
	// v.AuxInt is always sign-extended to 64 bits, even if the
	// represented value is unsigned. This undoes that sign extension.
	func (v *Value) AuxUnsigned() uint64 {
	c := v.AuxInt
	switch v.Op {
	case OpConst64:
	return uint64(c)
	case OpConst32:
	return uint64(uint32(c))
	case OpConst16:
	return uint64(uint16(c))
	case OpConst8:
	return uint64(uint8(c))
	}
	v.Fatalf("op %s isn't OpConst*", v.Op)
	return 0
	}

	func (v *Value) AuxFloat() float64 {
	if opcodeTable[v.Op].auxType != auxFloat32 && opcodeTable[v.Op].auxType != auxFloat64 {
	v.Fatalf("op %s doesn't have a float aux field", v.Op)
	}
	return math.Float64frombits(uint64(v.AuxInt))
	}
	func (v *Value) AuxValAndOff() ValAndOff {
	if opcodeTable[v.Op].auxType != auxSymValAndOff {
	v.Fatalf("op %s doesn't have a ValAndOff aux field", v.Op)
	}
	return ValAndOff(v.AuxInt)
	}

	// long form print. v# = opcode <type> [aux] args [: reg] (names)
	func (v *Value) LongString() string {
	s := fmt.Sprintf("v%d = %s", v.ID, v.Op)
	s += " <" + v.Type.String() + ">"
	s += v.auxString()
	for _, a := range v.Args {
	s += fmt.Sprintf(" %v", a)
	}
	var r []Location
	if v.Block != nil {
	r = v.Block.Func.RegAlloc
	}
	if int(v.ID) < len(r) && r[v.ID] != nil {
	s += " : " + r[v.ID].String()
	}
	var names []string
	if v.Block != nil {
	for name, values := range v.Block.Func.NamedValues {
	for _, value := range values {
	if value == v {
	names = append(names, name.String())
	break // drop duplicates.
	}
	}
	}
	}
	if len(names) != 0 {
	sort.Strings(names) // Otherwise a source of variation in debugging output.
	s += " (" + strings.Join(names, ", ") + ")"
	}
	return s
	}

	func (v *Value) auxString() string {
	switch opcodeTable[v.Op].auxType {
	case auxBool:
	if v.AuxInt == 0 {
	return " [false]"
	} else {
	return " [true]"
	}
	case auxInt8:
	return fmt.Sprintf(" [%d]", v.AuxInt8())
	case auxInt16:
	return fmt.Sprintf(" [%d]", v.AuxInt16())
	case auxInt32:
	return fmt.Sprintf(" [%d]", v.AuxInt32())
	case auxInt64, auxInt128:
	return fmt.Sprintf(" [%d]", v.AuxInt)
	case auxFloat32, auxFloat64:
	return fmt.Sprintf(" [%g]", v.AuxFloat())
	case auxString:
	return fmt.Sprintf(" {%q}", v.Aux)
	case auxSym, auxTyp:
	if v.Aux != nil {
	return fmt.Sprintf(" {%v}", v.Aux)
	}
	case auxSymOff, auxSymInt32, auxTypSize:
	s := ""
	if v.Aux != nil {
	s = fmt.Sprintf(" {%v}", v.Aux)
	}
	if v.AuxInt != 0 {
	s += fmt.Sprintf(" [%v]", v.AuxInt)
	}
	return s
	case auxSymValAndOff:
	s := ""
	if v.Aux != nil {
	s = fmt.Sprintf(" {%v}", v.Aux)
	}
	return s + fmt.Sprintf(" [%s]", v.AuxValAndOff())
	case auxCCop:
	return fmt.Sprintf(" {%s}", v.Aux.(Op))
	}
	return ""
	}

	// If/when midstack inlining is enabled (-l=4), the compiler gets both larger and slower.
	// Not-inlining this method is a help (Value.reset and Block.NewValue0 are similar).
	//go:noinline
	func (v Value) AddArg(w Value) {
	if v.Args == nil {
	v.resetArgs() // use argstorage
	}
	v.Args = append(v.Args, w)
	w.Uses++
	}
	func (v Value) AddArgs(a ...Value) {
	if v.Args == nil {
	v.resetArgs() // use argstorage
	}
	v.Args = append(v.Args, a...)
	for _, x := range a {
	x.Uses++
	}
	}
	func (v Value) SetArg(i int, w Value) {
	v.Args[i].Uses--
	v.Args[i] = w
	w.Uses++
	}
	func (v *Value) RemoveArg(i int) {
	v.Args[i].Uses--
	copy(v.Args[i:], v.Args[i+1:])
	v.Args[len(v.Args)-1] = nil // aid GC
	v.Args = v.Args[:len(v.Args)-1]
	}
	func (v Value) SetArgs1(a Value) {
	v.resetArgs()
	v.AddArg(a)
	}
	func (v Value) SetArgs2(a Value, b *Value) {
	v.resetArgs()
	v.AddArg(a)
	v.AddArg(b)
	}

	func (v *Value) resetArgs() {
	for _, a := range v.Args {
	a.Uses--
	}
	v.argstorage[0] = nil
	v.argstorage[1] = nil
	v.argstorage[2] = nil
	v.Args = v.argstorage[:0]
	}

	func (v *Value) reset(op Op) {
	v.Op = op
	if op != OpCopy && notStmtBoundary(op) {
	// Special case for OpCopy because of how it is used in rewrite
	v.Pos = v.Pos.WithNotStmt()
	}
	v.resetArgs()
	v.AuxInt = 0
	v.Aux = nil
	}

	// copyInto makes a new value identical to v and adds it to the end of b.
	func (v Value) copyInto(b Block) *Value {
	c := b.NewValue0(v.Pos.WithNotStmt(), v.Op, v.Type) // Lose the position, this causes line number churn otherwise.
	c.Aux = v.Aux
	c.AuxInt = v.AuxInt
	c.AddArgs(v.Args...)
	for _, a := range v.Args {
	if a.Type.IsMemory() {
	v.Fatalf("can't move a value with a memory arg %s", v.LongString())
	}
	}
	return c
	}

	// copyIntoWithXPos makes a new value identical to v and adds it to the end of b.
	// The supplied position is used as the position of the new value.
	func (v Value) copyIntoWithXPos(b Block, pos src.XPos) *Value {
	c := b.NewValue0(pos, v.Op, v.Type)
	c.Aux = v.Aux
	c.AuxInt = v.AuxInt
	c.AddArgs(v.Args...)
	for _, a := range v.Args {
	if a.Type.IsMemory() {
	v.Fatalf("can't move a value with a memory arg %s", v.LongString())
	}
	}
	return c
	}

	func (v *Value) Logf(msg string, args ...interface{}) { v.Block.Logf(msg, args...) }
	func (v *Value) Log() bool { return v.Block.Log() }
	func (v *Value) Fatalf(msg string, args ...interface{}) {
	v.Block.Func.fe.Fatalf(v.Pos, msg, args...)
	}

	// isGenericIntConst reports whether v is a generic integer constant.
	func (v *Value) isGenericIntConst() bool {
	return v != nil && (v.Op == OpConst64 \|\| v.Op == OpConst32 \|\| v.Op == OpConst16 \|\| v.Op == OpConst8)
	}

	// Reg returns the register assigned to v, in cmd/internal/obj/$ARCH numbering.
	func (v *Value) Reg() int16 {
	reg := v.Block.Func.RegAlloc[v.ID]
	if reg == nil {
	v.Fatalf("nil register for value: %s\n%s\n", v.LongString(), v.Block.Func)
	}
	return reg.(*Register).objNum
	}

	// Reg0 returns the register assigned to the first output of v, in cmd/internal/obj/$ARCH numbering.
	func (v *Value) Reg0() int16 {
	reg := v.Block.Func.RegAlloc[v.ID].(LocPair)[0]
	if reg == nil {
	v.Fatalf("nil first register for value: %s\n%s\n", v.LongString(), v.Block.Func)
	}
	return reg.(*Register).objNum
	}

	// Reg1 returns the register assigned to the second output of v, in cmd/internal/obj/$ARCH numbering.
	func (v *Value) Reg1() int16 {
	reg := v.Block.Func.RegAlloc[v.ID].(LocPair)[1]
	if reg == nil {
	v.Fatalf("nil second register for value: %s\n%s\n", v.LongString(), v.Block.Func)
	}
	return reg.(*Register).objNum
	}

	func (v *Value) RegName() string {
	reg := v.Block.Func.RegAlloc[v.ID]
	if reg == nil {
	v.Fatalf("nil register for value: %s\n%s\n", v.LongString(), v.Block.Func)
	}
	return reg.(*Register).name
	}

	// MemoryArg returns the memory argument for the Value.
	// The returned value, if non-nil, will be memory-typed (or a tuple with a memory-typed second part).
	// Otherwise, nil is returned.
	func (v Value) MemoryArg() Value {
	if v.Op == OpPhi {
	v.Fatalf("MemoryArg on Phi")
	}
	na := len(v.Args)
	if na == 0 {
	return nil
	}
	if m := v.Args[na-1]; m.Type.IsMemory() {
	return m
	}
	return nil
	}

	// LackingPos indicates whether v is a value that is unlikely to have a correct
	// position assigned to it. Ignoring such values leads to more user-friendly positions
	// assigned to nearby values and the blocks containing them.
	func (v *Value) LackingPos() bool {
	// The exact definition of LackingPos is somewhat heuristically defined and may change
	// in the future, for example if some of these operations are generated more carefully
	// with respect to their source position.
	return v.Op == OpVarDef \|\| v.Op == OpVarKill \|\| v.Op == OpVarLive \|\| v.Op == OpPhi \|\|
	(v.Op == OpFwdRef \|\| v.Op == OpCopy) && v.Type == types.TypeMem
	}