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// 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 returns 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
}