go decompose 源码
golang decompose 代码
文件路径：/src/cmd/compile/internal/ssa/decompose.go
// 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"
"sort"
)
// decompose converts phi ops on compound builtin types into phi
// ops on simple types, then invokes rewrite rules to decompose
// other ops on those types.
func decomposeBuiltIn(f *Func) {
// Decompose phis
for _, b := range f.Blocks {
for _, v := range b.Values {
if v.Op != OpPhi {
continue
}
decomposeBuiltInPhi(v)
}
}
// Decompose other values
// Note: Leave dead values because we need to keep the original
// values around so the name component resolution below can still work.
applyRewrite(f, rewriteBlockdec, rewriteValuedec, leaveDeadValues)
if f.Config.RegSize == 4 {
applyRewrite(f, rewriteBlockdec64, rewriteValuedec64, leaveDeadValues)
}
// Split up named values into their components.
// accumulate old names for aggregates (that are decomposed) in toDelete for efficient bulk deletion,
// accumulate new LocalSlots in newNames for addition after the iteration. This decomposition is for
// builtin types with leaf components, and thus there is no need to reprocess the newly create LocalSlots.
var toDelete []namedVal
var newNames []*LocalSlot
for i, name := range f.Names {
t := name.Type
switch {
case t.IsInteger() && t.Size() > f.Config.RegSize:
hiName, loName := f.SplitInt64(name)
newNames = maybeAppend2(f, newNames, hiName, loName)
for j, v := range f.NamedValues[*name] {
if v.Op != OpInt64Make {
continue
}
f.NamedValues[*hiName] = append(f.NamedValues[*hiName], v.Args[0])
f.NamedValues[*loName] = append(f.NamedValues[*loName], v.Args[1])
toDelete = append(toDelete, namedVal{i, j})
}
case t.IsComplex():
rName, iName := f.SplitComplex(name)
newNames = maybeAppend2(f, newNames, rName, iName)
for j, v := range f.NamedValues[*name] {
if v.Op != OpComplexMake {
continue
}
f.NamedValues[*rName] = append(f.NamedValues[*rName], v.Args[0])
f.NamedValues[*iName] = append(f.NamedValues[*iName], v.Args[1])
toDelete = append(toDelete, namedVal{i, j})
}
case t.IsString():
ptrName, lenName := f.SplitString(name)
newNames = maybeAppend2(f, newNames, ptrName, lenName)
for j, v := range f.NamedValues[*name] {
if v.Op != OpStringMake {
continue
}
f.NamedValues[*ptrName] = append(f.NamedValues[*ptrName], v.Args[0])
f.NamedValues[*lenName] = append(f.NamedValues[*lenName], v.Args[1])
toDelete = append(toDelete, namedVal{i, j})
}
case t.IsSlice():
ptrName, lenName, capName := f.SplitSlice(name)
newNames = maybeAppend2(f, newNames, ptrName, lenName)
newNames = maybeAppend(f, newNames, capName)
for j, v := range f.NamedValues[*name] {
if v.Op != OpSliceMake {
continue
}
f.NamedValues[*ptrName] = append(f.NamedValues[*ptrName], v.Args[0])
f.NamedValues[*lenName] = append(f.NamedValues[*lenName], v.Args[1])
f.NamedValues[*capName] = append(f.NamedValues[*capName], v.Args[2])
toDelete = append(toDelete, namedVal{i, j})
}
case t.IsInterface():
typeName, dataName := f.SplitInterface(name)
newNames = maybeAppend2(f, newNames, typeName, dataName)
for j, v := range f.NamedValues[*name] {
if v.Op != OpIMake {
continue
}
f.NamedValues[*typeName] = append(f.NamedValues[*typeName], v.Args[0])
f.NamedValues[*dataName] = append(f.NamedValues[*dataName], v.Args[1])
toDelete = append(toDelete, namedVal{i, j})
}
case t.IsFloat():
// floats are never decomposed, even ones bigger than RegSize
case t.Size() > f.Config.RegSize:
f.Fatalf("undecomposed named type %s %v", name, t)
}
}
deleteNamedVals(f, toDelete)
f.Names = append(f.Names, newNames...)
}
func maybeAppend(f *Func, ss []*LocalSlot, s *LocalSlot) []*LocalSlot {
if _, ok := f.NamedValues[*s]; !ok {
f.NamedValues[*s] = nil
return append(ss, s)
}
return ss
}
func maybeAppend2(f *Func, ss []*LocalSlot, s1, s2 *LocalSlot) []*LocalSlot {
return maybeAppend(f, maybeAppend(f, ss, s1), s2)
}
func decomposeBuiltInPhi(v *Value) {
switch {
case v.Type.IsInteger() && v.Type.Size() > v.Block.Func.Config.RegSize:
decomposeInt64Phi(v)
case v.Type.IsComplex():
decomposeComplexPhi(v)
case v.Type.IsString():
decomposeStringPhi(v)
case v.Type.IsSlice():
decomposeSlicePhi(v)
case v.Type.IsInterface():
decomposeInterfacePhi(v)
case v.Type.IsFloat():
// floats are never decomposed, even ones bigger than RegSize
case v.Type.Size() > v.Block.Func.Config.RegSize:
v.Fatalf("undecomposed type %s", v.Type)
}
}
func decomposeStringPhi(v *Value) {
types := &v.Block.Func.Config.Types
ptrType := types.BytePtr
lenType := types.Int
ptr := v.Block.NewValue0(v.Pos, OpPhi, ptrType)
len := v.Block.NewValue0(v.Pos, OpPhi, lenType)
for _, a := range v.Args {
ptr.AddArg(a.Block.NewValue1(v.Pos, OpStringPtr, ptrType, a))
len.AddArg(a.Block.NewValue1(v.Pos, OpStringLen, lenType, a))
}
v.reset(OpStringMake)
v.AddArg(ptr)
v.AddArg(len)
}
func decomposeSlicePhi(v *Value) {
types := &v.Block.Func.Config.Types
ptrType := v.Type.Elem().PtrTo()
lenType := types.Int
ptr := v.Block.NewValue0(v.Pos, OpPhi, ptrType)
len := v.Block.NewValue0(v.Pos, OpPhi, lenType)
cap := v.Block.NewValue0(v.Pos, OpPhi, lenType)
for _, a := range v.Args {
ptr.AddArg(a.Block.NewValue1(v.Pos, OpSlicePtr, ptrType, a))
len.AddArg(a.Block.NewValue1(v.Pos, OpSliceLen, lenType, a))
cap.AddArg(a.Block.NewValue1(v.Pos, OpSliceCap, lenType, a))
}
v.reset(OpSliceMake)
v.AddArg(ptr)
v.AddArg(len)
v.AddArg(cap)
}
func decomposeInt64Phi(v *Value) {
cfgtypes := &v.Block.Func.Config.Types
var partType *types.Type
if v.Type.IsSigned() {
partType = cfgtypes.Int32
} else {
partType = cfgtypes.UInt32
}
hi := v.Block.NewValue0(v.Pos, OpPhi, partType)
lo := v.Block.NewValue0(v.Pos, OpPhi, cfgtypes.UInt32)
for _, a := range v.Args {
hi.AddArg(a.Block.NewValue1(v.Pos, OpInt64Hi, partType, a))
lo.AddArg(a.Block.NewValue1(v.Pos, OpInt64Lo, cfgtypes.UInt32, a))
}
v.reset(OpInt64Make)
v.AddArg(hi)
v.AddArg(lo)
}
func decomposeComplexPhi(v *Value) {
cfgtypes := &v.Block.Func.Config.Types
var partType *types.Type
switch z := v.Type.Size(); z {
case 8:
partType = cfgtypes.Float32
case 16:
partType = cfgtypes.Float64
default:
v.Fatalf("decomposeComplexPhi: bad complex size %d", z)
}
real := v.Block.NewValue0(v.Pos, OpPhi, partType)
imag := v.Block.NewValue0(v.Pos, OpPhi, partType)
for _, a := range v.Args {
real.AddArg(a.Block.NewValue1(v.Pos, OpComplexReal, partType, a))
imag.AddArg(a.Block.NewValue1(v.Pos, OpComplexImag, partType, a))
}
v.reset(OpComplexMake)
v.AddArg(real)
v.AddArg(imag)
}
func decomposeInterfacePhi(v *Value) {
uintptrType := v.Block.Func.Config.Types.Uintptr
ptrType := v.Block.Func.Config.Types.BytePtr
itab := v.Block.NewValue0(v.Pos, OpPhi, uintptrType)
data := v.Block.NewValue0(v.Pos, OpPhi, ptrType)
for _, a := range v.Args {
itab.AddArg(a.Block.NewValue1(v.Pos, OpITab, uintptrType, a))
data.AddArg(a.Block.NewValue1(v.Pos, OpIData, ptrType, a))
}
v.reset(OpIMake)
v.AddArg(itab)
v.AddArg(data)
}
func decomposeUser(f *Func) {
for _, b := range f.Blocks {
for _, v := range b.Values {
if v.Op != OpPhi {
continue
}
decomposeUserPhi(v)
}
}
// Split up named values into their components.
i := 0
var newNames []*LocalSlot
for _, name := range f.Names {
t := name.Type
switch {
case t.IsStruct():
newNames = decomposeUserStructInto(f, name, newNames)
case t.IsArray():
newNames = decomposeUserArrayInto(f, name, newNames)
default:
f.Names[i] = name
i++
}
}
f.Names = f.Names[:i]
f.Names = append(f.Names, newNames...)
}
// decomposeUserArrayInto creates names for the element(s) of arrays referenced
// by name where possible, and appends those new names to slots, which is then
// returned.
func decomposeUserArrayInto(f *Func, name *LocalSlot, slots []*LocalSlot) []*LocalSlot {
t := name.Type
if t.NumElem() == 0 {
// TODO(khr): Not sure what to do here. Probably nothing.
// Names for empty arrays aren't important.
return slots
}
if t.NumElem() != 1 {
// shouldn't get here due to CanSSA
f.Fatalf("array not of size 1")
}
elemName := f.SplitArray(name)
var keep []*Value
for _, v := range f.NamedValues[*name] {
if v.Op != OpArrayMake1 {
keep = append(keep, v)
continue
}
f.NamedValues[*elemName] = append(f.NamedValues[*elemName], v.Args[0])
}
if len(keep) == 0 {
// delete the name for the array as a whole
delete(f.NamedValues, *name)
} else {
f.NamedValues[*name] = keep
}
if t.Elem().IsArray() {
return decomposeUserArrayInto(f, elemName, slots)
} else if t.Elem().IsStruct() {
return decomposeUserStructInto(f, elemName, slots)
}
return append(slots, elemName)
}
// decomposeUserStructInto creates names for the fields(s) of structs referenced
// by name where possible, and appends those new names to slots, which is then
// returned.
func decomposeUserStructInto(f *Func, name *LocalSlot, slots []*LocalSlot) []*LocalSlot {
fnames := []*LocalSlot{} // slots for struct in name
t := name.Type
n := t.NumFields()
for i := 0; i < n; i++ {
fs := f.SplitStruct(name, i)
fnames = append(fnames, fs)
// arrays and structs will be decomposed further, so
// there's no need to record a name
if !fs.Type.IsArray() && !fs.Type.IsStruct() {
slots = maybeAppend(f, slots, fs)
}
}
makeOp := StructMakeOp(n)
var keep []*Value
// create named values for each struct field
for _, v := range f.NamedValues[*name] {
if v.Op != makeOp {
keep = append(keep, v)
continue
}
for i := 0; i < len(fnames); i++ {
f.NamedValues[*fnames[i]] = append(f.NamedValues[*fnames[i]], v.Args[i])
}
}
if len(keep) == 0 {
// delete the name for the struct as a whole
delete(f.NamedValues, *name)
} else {
f.NamedValues[*name] = keep
}
// now that this f.NamedValues contains values for the struct
// fields, recurse into nested structs
for i := 0; i < n; i++ {
if name.Type.FieldType(i).IsStruct() {
slots = decomposeUserStructInto(f, fnames[i], slots)
delete(f.NamedValues, *fnames[i])
} else if name.Type.FieldType(i).IsArray() {
slots = decomposeUserArrayInto(f, fnames[i], slots)
delete(f.NamedValues, *fnames[i])
}
}
return slots
}
func decomposeUserPhi(v *Value) {
switch {
case v.Type.IsStruct():
decomposeStructPhi(v)
case v.Type.IsArray():
decomposeArrayPhi(v)
}
}
// decomposeStructPhi replaces phi-of-struct with structmake(phi-for-each-field),
// and then recursively decomposes the phis for each field.
func decomposeStructPhi(v *Value) {
t := v.Type
n := t.NumFields()
var fields [MaxStruct]*Value
for i := 0; i < n; i++ {
fields[i] = v.Block.NewValue0(v.Pos, OpPhi, t.FieldType(i))
}
for _, a := range v.Args {
for i := 0; i < n; i++ {
fields[i].AddArg(a.Block.NewValue1I(v.Pos, OpStructSelect, t.FieldType(i), int64(i), a))
}
}
v.reset(StructMakeOp(n))
v.AddArgs(fields[:n]...)
// Recursively decompose phis for each field.
for _, f := range fields[:n] {
decomposeUserPhi(f)
}
}
// decomposeArrayPhi replaces phi-of-array with arraymake(phi-of-array-element),
// and then recursively decomposes the element phi.
func decomposeArrayPhi(v *Value) {
t := v.Type
if t.NumElem() == 0 {
v.reset(OpArrayMake0)
return
}
if t.NumElem() != 1 {
v.Fatalf("SSAable array must have no more than 1 element")
}
elem := v.Block.NewValue0(v.Pos, OpPhi, t.Elem())
for _, a := range v.Args {
elem.AddArg(a.Block.NewValue1I(v.Pos, OpArraySelect, t.Elem(), 0, a))
}
v.reset(OpArrayMake1)
v.AddArg(elem)
// Recursively decompose elem phi.
decomposeUserPhi(elem)
}
// MaxStruct is the maximum number of fields a struct
// can have and still be SSAable.
const MaxStruct = 4
// StructMakeOp returns the opcode to construct a struct with the
// given number of fields.
func StructMakeOp(nf int) Op {
switch nf {
case 0:
return OpStructMake0
case 1:
return OpStructMake1
case 2:
return OpStructMake2
case 3:
return OpStructMake3
case 4:
return OpStructMake4
}
panic("too many fields in an SSAable struct")
}
type namedVal struct {
locIndex, valIndex int // f.NamedValues[f.Names[locIndex]][valIndex] = key
}
// deleteNamedVals removes particular values with debugger names from f's naming data structures,
// removes all values with OpInvalid, and re-sorts the list of Names.
func deleteNamedVals(f *Func, toDelete []namedVal) {
// Arrange to delete from larger indices to smaller, to ensure swap-with-end deletion does not invalidate pending indices.
sort.Slice(toDelete, func(i, j int) bool {
if toDelete[i].locIndex != toDelete[j].locIndex {
return toDelete[i].locIndex > toDelete[j].locIndex
}
return toDelete[i].valIndex > toDelete[j].valIndex
})
// Get rid of obsolete names
for _, d := range toDelete {
loc := f.Names[d.locIndex]
vals := f.NamedValues[*loc]
l := len(vals) - 1
if l > 0 {
vals[d.valIndex] = vals[l]
}
vals[l] = nil
f.NamedValues[*loc] = vals[:l]
}
// Delete locations with no values attached.
end := len(f.Names)
for i := len(f.Names) - 1; i >= 0; i-- {
loc := f.Names[i]
vals := f.NamedValues[*loc]
last := len(vals)
for j := len(vals) - 1; j >= 0; j-- {
if vals[j].Op == OpInvalid {
last--
vals[j] = vals[last]
vals[last] = nil
}
}
if last < len(vals) {
f.NamedValues[*loc] = vals[:last]
}
if len(vals) == 0 {
delete(f.NamedValues, *loc)
end--
f.Names[i] = f.Names[end]
f.Names[end] = nil
}
}
f.Names = f.Names[:end]
}
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