gcc/libgo/go/regexp/onepass.go
Ian Lance Taylor f8d9fa9e80 libgo, compiler: Upgrade libgo to Go 1.4, except for runtime.
This upgrades all of libgo other than the runtime package to
the Go 1.4 release.  In Go 1.4 much of the runtime was
rewritten into Go.  Merging that code will take more time and
will not change the API, so I'm putting it off for now.

There are a few runtime changes anyhow, to accomodate other
packages that rely on minor modifications to the runtime
support.

The compiler changes slightly to add a one-bit flag to each
type descriptor kind that is stored directly in an interface,
which for gccgo is currently only pointer types.  Another
one-bit flag (gcprog) is reserved because it is used by the gc
compiler, but gccgo does not currently use it.

There is another error check in the compiler since I ran
across it during testing.

gotools/:
	* Makefile.am (go_cmd_go_files): Sort entries.  Add generate.go.
	* Makefile.in: Rebuild.

From-SVN: r219627
2015-01-15 00:27:56 +00:00

582 lines
16 KiB
Go

// Copyright 2014 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 regexp
import (
"bytes"
"regexp/syntax"
"sort"
"unicode"
)
// "One-pass" regexp execution.
// Some regexps can be analyzed to determine that they never need
// backtracking: they are guaranteed to run in one pass over the string
// without bothering to save all the usual NFA state.
// Detect those and execute them more quickly.
// A onePassProg is a compiled one-pass regular expression program.
// It is the same as syntax.Prog except for the use of onePassInst.
type onePassProg struct {
Inst []onePassInst
Start int // index of start instruction
NumCap int // number of InstCapture insts in re
}
// A onePassInst is a single instruction in a one-pass regular expression program.
// It is the same as syntax.Inst except for the new 'Next' field.
type onePassInst struct {
syntax.Inst
Next []uint32
}
// OnePassPrefix returns a literal string that all matches for the
// regexp must start with. Complete is true if the prefix
// is the entire match. Pc is the index of the last rune instruction
// in the string. The OnePassPrefix skips over the mandatory
// EmptyBeginText
func onePassPrefix(p *syntax.Prog) (prefix string, complete bool, pc uint32) {
i := &p.Inst[p.Start]
if i.Op != syntax.InstEmptyWidth || (syntax.EmptyOp(i.Arg))&syntax.EmptyBeginText == 0 {
return "", i.Op == syntax.InstMatch, uint32(p.Start)
}
pc = i.Out
i = &p.Inst[pc]
for i.Op == syntax.InstNop {
pc = i.Out
i = &p.Inst[pc]
}
// Avoid allocation of buffer if prefix is empty.
if iop(i) != syntax.InstRune || len(i.Rune) != 1 {
return "", i.Op == syntax.InstMatch, uint32(p.Start)
}
// Have prefix; gather characters.
var buf bytes.Buffer
for iop(i) == syntax.InstRune && len(i.Rune) == 1 && syntax.Flags(i.Arg)&syntax.FoldCase == 0 {
buf.WriteRune(i.Rune[0])
pc, i = i.Out, &p.Inst[i.Out]
}
return buf.String(), i.Op == syntax.InstEmptyWidth && (syntax.EmptyOp(i.Arg))&syntax.EmptyBeginText != 0, pc
}
// OnePassNext selects the next actionable state of the prog, based on the input character.
// It should only be called when i.Op == InstAlt or InstAltMatch, and from the one-pass machine.
// One of the alternates may ultimately lead without input to end of line. If the instruction
// is InstAltMatch the path to the InstMatch is in i.Out, the normal node in i.Next.
func onePassNext(i *onePassInst, r rune) uint32 {
next := i.MatchRunePos(r)
if next >= 0 {
return i.Next[next]
}
if i.Op == syntax.InstAltMatch {
return i.Out
}
return 0
}
func iop(i *syntax.Inst) syntax.InstOp {
op := i.Op
switch op {
case syntax.InstRune1, syntax.InstRuneAny, syntax.InstRuneAnyNotNL:
op = syntax.InstRune
}
return op
}
// Sparse Array implementation is used as a queueOnePass.
type queueOnePass struct {
sparse []uint32
dense []uint32
size, nextIndex uint32
}
func (q *queueOnePass) empty() bool {
return q.nextIndex >= q.size
}
func (q *queueOnePass) next() (n uint32) {
n = q.dense[q.nextIndex]
q.nextIndex++
return
}
func (q *queueOnePass) clear() {
q.size = 0
q.nextIndex = 0
}
func (q *queueOnePass) reset() {
q.nextIndex = 0
}
func (q *queueOnePass) contains(u uint32) bool {
if u >= uint32(len(q.sparse)) {
return false
}
return q.sparse[u] < q.size && q.dense[q.sparse[u]] == u
}
func (q *queueOnePass) insert(u uint32) {
if !q.contains(u) {
q.insertNew(u)
}
}
func (q *queueOnePass) insertNew(u uint32) {
if u >= uint32(len(q.sparse)) {
return
}
q.sparse[u] = q.size
q.dense[q.size] = u
q.size++
}
func newQueue(size int) (q *queueOnePass) {
return &queueOnePass{
sparse: make([]uint32, size),
dense: make([]uint32, size),
}
}
// mergeRuneSets merges two non-intersecting runesets, and returns the merged result,
// and a NextIp array. The idea is that if a rune matches the OnePassRunes at index
// i, NextIp[i/2] is the target. If the input sets intersect, an empty runeset and a
// NextIp array with the single element mergeFailed is returned.
// The code assumes that both inputs contain ordered and non-intersecting rune pairs.
const mergeFailed = uint32(0xffffffff)
var (
noRune = []rune{}
noNext = []uint32{mergeFailed}
)
func mergeRuneSets(leftRunes, rightRunes *[]rune, leftPC, rightPC uint32) ([]rune, []uint32) {
leftLen := len(*leftRunes)
rightLen := len(*rightRunes)
if leftLen&0x1 != 0 || rightLen&0x1 != 0 {
panic("mergeRuneSets odd length []rune")
}
var (
lx, rx int
)
merged := make([]rune, 0)
next := make([]uint32, 0)
ok := true
defer func() {
if !ok {
merged = nil
next = nil
}
}()
ix := -1
extend := func(newLow *int, newArray *[]rune, pc uint32) bool {
if ix > 0 && (*newArray)[*newLow] <= merged[ix] {
return false
}
merged = append(merged, (*newArray)[*newLow], (*newArray)[*newLow+1])
*newLow += 2
ix += 2
next = append(next, pc)
return true
}
for lx < leftLen || rx < rightLen {
switch {
case rx >= rightLen:
ok = extend(&lx, leftRunes, leftPC)
case lx >= leftLen:
ok = extend(&rx, rightRunes, rightPC)
case (*rightRunes)[rx] < (*leftRunes)[lx]:
ok = extend(&rx, rightRunes, rightPC)
default:
ok = extend(&lx, leftRunes, leftPC)
}
if !ok {
return noRune, noNext
}
}
return merged, next
}
// cleanupOnePass drops working memory, and restores certain shortcut instructions.
func cleanupOnePass(prog *onePassProg, original *syntax.Prog) {
for ix, instOriginal := range original.Inst {
switch instOriginal.Op {
case syntax.InstAlt, syntax.InstAltMatch, syntax.InstRune:
case syntax.InstCapture, syntax.InstEmptyWidth, syntax.InstNop, syntax.InstMatch, syntax.InstFail:
prog.Inst[ix].Next = nil
case syntax.InstRune1, syntax.InstRuneAny, syntax.InstRuneAnyNotNL:
prog.Inst[ix].Next = nil
prog.Inst[ix] = onePassInst{Inst: instOriginal}
}
}
}
// onePassCopy creates a copy of the original Prog, as we'll be modifying it
func onePassCopy(prog *syntax.Prog) *onePassProg {
p := &onePassProg{
Start: prog.Start,
NumCap: prog.NumCap,
}
for _, inst := range prog.Inst {
p.Inst = append(p.Inst, onePassInst{Inst: inst})
}
// rewrites one or more common Prog constructs that enable some otherwise
// non-onepass Progs to be onepass. A:BD (for example) means an InstAlt at
// ip A, that points to ips B & C.
// A:BC + B:DA => A:BC + B:CD
// A:BC + B:DC => A:DC + B:DC
for pc := range p.Inst {
switch p.Inst[pc].Op {
default:
continue
case syntax.InstAlt, syntax.InstAltMatch:
// A:Bx + B:Ay
p_A_Other := &p.Inst[pc].Out
p_A_Alt := &p.Inst[pc].Arg
// make sure a target is another Alt
instAlt := p.Inst[*p_A_Alt]
if !(instAlt.Op == syntax.InstAlt || instAlt.Op == syntax.InstAltMatch) {
p_A_Alt, p_A_Other = p_A_Other, p_A_Alt
instAlt = p.Inst[*p_A_Alt]
if !(instAlt.Op == syntax.InstAlt || instAlt.Op == syntax.InstAltMatch) {
continue
}
}
instOther := p.Inst[*p_A_Other]
// Analyzing both legs pointing to Alts is for another day
if instOther.Op == syntax.InstAlt || instOther.Op == syntax.InstAltMatch {
// too complicated
continue
}
// simple empty transition loop
// A:BC + B:DA => A:BC + B:DC
p_B_Alt := &p.Inst[*p_A_Alt].Out
p_B_Other := &p.Inst[*p_A_Alt].Arg
patch := false
if instAlt.Out == uint32(pc) {
patch = true
} else if instAlt.Arg == uint32(pc) {
patch = true
p_B_Alt, p_B_Other = p_B_Other, p_B_Alt
}
if patch {
*p_B_Alt = *p_A_Other
}
// empty transition to common target
// A:BC + B:DC => A:DC + B:DC
if *p_A_Other == *p_B_Alt {
*p_A_Alt = *p_B_Other
}
}
}
return p
}
// runeSlice exists to permit sorting the case-folded rune sets.
type runeSlice []rune
func (p runeSlice) Len() int { return len(p) }
func (p runeSlice) Less(i, j int) bool { return p[i] < p[j] }
func (p runeSlice) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
// Sort is a convenience method.
func (p runeSlice) Sort() {
sort.Sort(p)
}
var anyRuneNotNL = []rune{0, '\n' - 1, '\n' + 1, unicode.MaxRune}
var anyRune = []rune{0, unicode.MaxRune}
// makeOnePass creates a onepass Prog, if possible. It is possible if at any alt,
// the match engine can always tell which branch to take. The routine may modify
// p if it is turned into a onepass Prog. If it isn't possible for this to be a
// onepass Prog, the Prog notOnePass is returned. makeOnePass is recursive
// to the size of the Prog.
func makeOnePass(p *onePassProg) *onePassProg {
// If the machine is very long, it's not worth the time to check if we can use one pass.
if len(p.Inst) >= 1000 {
return notOnePass
}
var (
instQueue = newQueue(len(p.Inst))
visitQueue = newQueue(len(p.Inst))
build func(uint32, *queueOnePass)
check func(uint32, map[uint32]bool) bool
onePassRunes = make([][]rune, len(p.Inst))
)
build = func(pc uint32, q *queueOnePass) {
if q.contains(pc) {
return
}
inst := p.Inst[pc]
switch inst.Op {
case syntax.InstAlt, syntax.InstAltMatch:
q.insert(inst.Out)
build(inst.Out, q)
q.insert(inst.Arg)
case syntax.InstMatch, syntax.InstFail:
default:
q.insert(inst.Out)
}
}
// check that paths from Alt instructions are unambiguous, and rebuild the new
// program as a onepass program
check = func(pc uint32, m map[uint32]bool) (ok bool) {
ok = true
inst := &p.Inst[pc]
if visitQueue.contains(pc) {
return
}
visitQueue.insert(pc)
switch inst.Op {
case syntax.InstAlt, syntax.InstAltMatch:
ok = check(inst.Out, m) && check(inst.Arg, m)
// check no-input paths to InstMatch
matchOut := m[inst.Out]
matchArg := m[inst.Arg]
if matchOut && matchArg {
ok = false
break
}
// Match on empty goes in inst.Out
if matchArg {
inst.Out, inst.Arg = inst.Arg, inst.Out
matchOut, matchArg = matchArg, matchOut
}
if matchOut {
m[pc] = true
inst.Op = syntax.InstAltMatch
}
// build a dispatch operator from the two legs of the alt.
onePassRunes[pc], inst.Next = mergeRuneSets(
&onePassRunes[inst.Out], &onePassRunes[inst.Arg], inst.Out, inst.Arg)
if len(inst.Next) > 0 && inst.Next[0] == mergeFailed {
ok = false
break
}
case syntax.InstCapture, syntax.InstNop:
ok = check(inst.Out, m)
m[pc] = m[inst.Out]
// pass matching runes back through these no-ops.
onePassRunes[pc] = append([]rune{}, onePassRunes[inst.Out]...)
inst.Next = []uint32{}
for i := len(onePassRunes[pc]) / 2; i >= 0; i-- {
inst.Next = append(inst.Next, inst.Out)
}
case syntax.InstEmptyWidth:
ok = check(inst.Out, m)
m[pc] = m[inst.Out]
onePassRunes[pc] = append([]rune{}, onePassRunes[inst.Out]...)
inst.Next = []uint32{}
for i := len(onePassRunes[pc]) / 2; i >= 0; i-- {
inst.Next = append(inst.Next, inst.Out)
}
case syntax.InstMatch, syntax.InstFail:
m[pc] = inst.Op == syntax.InstMatch
break
case syntax.InstRune:
ok = check(inst.Out, m)
m[pc] = false
if len(inst.Next) > 0 {
break
}
if len(inst.Rune) == 0 {
onePassRunes[pc] = []rune{}
inst.Next = []uint32{inst.Out}
break
}
runes := make([]rune, 0)
if len(inst.Rune) == 1 && syntax.Flags(inst.Arg)&syntax.FoldCase != 0 {
r0 := inst.Rune[0]
runes = append(runes, r0, r0)
for r1 := unicode.SimpleFold(r0); r1 != r0; r1 = unicode.SimpleFold(r1) {
runes = append(runes, r1, r1)
}
sort.Sort(runeSlice(runes))
} else {
runes = append(runes, inst.Rune...)
}
onePassRunes[pc] = runes
inst.Next = []uint32{}
for i := len(onePassRunes[pc]) / 2; i >= 0; i-- {
inst.Next = append(inst.Next, inst.Out)
}
inst.Op = syntax.InstRune
case syntax.InstRune1:
ok = check(inst.Out, m)
m[pc] = false
if len(inst.Next) > 0 {
break
}
runes := []rune{}
// expand case-folded runes
if syntax.Flags(inst.Arg)&syntax.FoldCase != 0 {
r0 := inst.Rune[0]
runes = append(runes, r0, r0)
for r1 := unicode.SimpleFold(r0); r1 != r0; r1 = unicode.SimpleFold(r1) {
runes = append(runes, r1, r1)
}
sort.Sort(runeSlice(runes))
} else {
runes = append(runes, inst.Rune[0], inst.Rune[0])
}
onePassRunes[pc] = runes
inst.Next = []uint32{}
for i := len(onePassRunes[pc]) / 2; i >= 0; i-- {
inst.Next = append(inst.Next, inst.Out)
}
inst.Op = syntax.InstRune
case syntax.InstRuneAny:
ok = check(inst.Out, m)
m[pc] = false
if len(inst.Next) > 0 {
break
}
onePassRunes[pc] = append([]rune{}, anyRune...)
inst.Next = []uint32{inst.Out}
case syntax.InstRuneAnyNotNL:
ok = check(inst.Out, m)
m[pc] = false
if len(inst.Next) > 0 {
break
}
onePassRunes[pc] = append([]rune{}, anyRuneNotNL...)
inst.Next = []uint32{}
for i := len(onePassRunes[pc]) / 2; i >= 0; i-- {
inst.Next = append(inst.Next, inst.Out)
}
}
return
}
instQueue.clear()
instQueue.insert(uint32(p.Start))
m := make(map[uint32]bool, len(p.Inst))
for !instQueue.empty() {
pc := instQueue.next()
inst := p.Inst[pc]
visitQueue.clear()
if !check(uint32(pc), m) {
p = notOnePass
break
}
switch inst.Op {
case syntax.InstAlt, syntax.InstAltMatch:
instQueue.insert(inst.Out)
instQueue.insert(inst.Arg)
case syntax.InstCapture, syntax.InstEmptyWidth, syntax.InstNop:
instQueue.insert(inst.Out)
case syntax.InstMatch:
case syntax.InstFail:
case syntax.InstRune, syntax.InstRune1, syntax.InstRuneAny, syntax.InstRuneAnyNotNL:
default:
}
}
if p != notOnePass {
for i := range p.Inst {
p.Inst[i].Rune = onePassRunes[i]
}
}
return p
}
// walk visits each Inst in the prog once, and applies the argument
// function(ip, next), in pre-order.
func walk(prog *syntax.Prog, funcs ...func(ip, next uint32)) {
var walk1 func(uint32)
progQueue := newQueue(len(prog.Inst))
walk1 = func(ip uint32) {
if progQueue.contains(ip) {
return
}
progQueue.insert(ip)
inst := prog.Inst[ip]
switch inst.Op {
case syntax.InstAlt, syntax.InstAltMatch:
for _, f := range funcs {
f(ip, inst.Out)
f(ip, inst.Arg)
}
walk1(inst.Out)
walk1(inst.Arg)
default:
for _, f := range funcs {
f(ip, inst.Out)
}
walk1(inst.Out)
}
}
walk1(uint32(prog.Start))
}
// find returns the Insts that match the argument predicate function
func find(prog *syntax.Prog, f func(*syntax.Prog, int) bool) (matches []uint32) {
matches = []uint32{}
for ip := range prog.Inst {
if f(prog, ip) {
matches = append(matches, uint32(ip))
}
}
return
}
var notOnePass *onePassProg = nil
// compileOnePass returns a new *syntax.Prog suitable for onePass execution if the original Prog
// can be recharacterized as a one-pass regexp program, or syntax.notOnePass if the
// Prog cannot be converted. For a one pass prog, the fundamental condition that must
// be true is: at any InstAlt, there must be no ambiguity about what branch to take.
func compileOnePass(prog *syntax.Prog) (p *onePassProg) {
if prog.Start == 0 {
return notOnePass
}
// onepass regexp is anchored
if prog.Inst[prog.Start].Op != syntax.InstEmptyWidth ||
syntax.EmptyOp(prog.Inst[prog.Start].Arg)&syntax.EmptyBeginText != syntax.EmptyBeginText {
return notOnePass
}
// every instruction leading to InstMatch must be EmptyEndText
for _, inst := range prog.Inst {
opOut := prog.Inst[inst.Out].Op
switch inst.Op {
default:
if opOut == syntax.InstMatch {
return notOnePass
}
case syntax.InstAlt, syntax.InstAltMatch:
if opOut == syntax.InstMatch || prog.Inst[inst.Arg].Op == syntax.InstMatch {
return notOnePass
}
case syntax.InstEmptyWidth:
if opOut == syntax.InstMatch {
if syntax.EmptyOp(inst.Arg)&syntax.EmptyEndText == syntax.EmptyEndText {
continue
}
return notOnePass
}
}
}
// Creates a slightly optimized copy of the original Prog
// that cleans up some Prog idioms that block valid onepass programs
p = onePassCopy(prog)
// checkAmbiguity on InstAlts, build onepass Prog if possible
p = makeOnePass(p)
if p != notOnePass {
cleanupOnePass(p, prog)
}
return p
}