// Copyright 2007 The RE2 Authors. All Rights Reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Compiled regular expression representation.
// Tested by compile_test.cc
#include "re2/prog.h"
#if defined(__AVX2__)
#include <immintrin.h>
#ifdef _MSC_VER
#include <intrin.h>
#endif
#endif
#include <stdint.h>
#include <string.h>
#include <algorithm>
#include <memory>
#include <utility>
#include "util/util.h"
#include "util/logging.h"
#include "util/strutil.h"
#include "re2/bitmap256.h"
#include "re2/stringpiece.h"
namespace re2 {
// Constructors per Inst opcode
void Prog::Inst::InitAlt(uint32_t out, uint32_t out1) {
DCHECK_EQ(out_opcode_, 0);
set_out_opcode(out, kInstAlt);
out1_ = out1;
}
void Prog::Inst::InitByteRange(int lo, int hi, int foldcase, uint32_t out) {
DCHECK_EQ(out_opcode_, 0);
set_out_opcode(out, kInstByteRange);
lo_ = lo & 0xFF;
hi_ = hi & 0xFF;
hint_foldcase_ = foldcase&1;
}
void Prog::Inst::InitCapture(int cap, uint32_t out) {
DCHECK_EQ(out_opcode_, 0);
set_out_opcode(out, kInstCapture);
cap_ = cap;
}
void Prog::Inst::InitEmptyWidth(EmptyOp empty, uint32_t out) {
DCHECK_EQ(out_opcode_, 0);
set_out_opcode(out, kInstEmptyWidth);
empty_ = empty;
}
void Prog::Inst::InitMatch(int32_t id) {
DCHECK_EQ(out_opcode_, 0);
set_opcode(kInstMatch);
match_id_ = id;
}
void Prog::Inst::InitNop(uint32_t out) {
DCHECK_EQ(out_opcode_, 0);
set_opcode(kInstNop);
}
void Prog::Inst::InitFail() {
DCHECK_EQ(out_opcode_, 0);
set_opcode(kInstFail);
}
std::string Prog::Inst::Dump() {
switch (opcode()) {
default:
return StringPrintf("opcode %d", static_cast<int>(opcode()));
case kInstAlt:
return StringPrintf("alt -> %d | %d", out(), out1_);
case kInstAltMatch:
return StringPrintf("altmatch -> %d | %d", out(), out1_);
case kInstByteRange:
return StringPrintf("byte%s [%02x-%02x] %d -> %d",
foldcase() ? "/i" : "",
lo_, hi_, hint(), out());
case kInstCapture:
return StringPrintf("capture %d -> %d", cap_, out());
case kInstEmptyWidth:
return StringPrintf("emptywidth %#x -> %d",
static_cast<int>(empty_), out());
case kInstMatch:
return StringPrintf("match! %d", match_id());
case kInstNop:
return StringPrintf("nop -> %d", out());
case kInstFail:
return StringPrintf("fail");
}
}
Prog::Prog()
: anchor_start_(false),
anchor_end_(false),
reversed_(false),
did_flatten_(false),
did_onepass_(false),
start_(0),
start_unanchored_(0),
size_(0),
bytemap_range_(0),
prefix_foldcase_(false),
prefix_size_(0),
list_count_(0),
bit_state_text_max_size_(0),
dfa_mem_(0),
dfa_first_(NULL),
dfa_longest_(NULL) {
}
Prog::~Prog() {
DeleteDFA(dfa_longest_);
DeleteDFA(dfa_first_);
if (prefix_foldcase_)
delete[] prefix_dfa_;
}
typedef SparseSet Workq;
static inline void AddToQueue(Workq* q, int id) {
if (id != 0)
q->insert(id);
}
static std::string ProgToString(Prog* prog, Workq* q) {
std::string s;
for (Workq::iterator i = q->begin(); i != q->end(); ++i) {
int id = *i;
Prog::Inst* ip = prog->inst(id);
s += StringPrintf("%d. %s\n", id, ip->Dump().c_str());
AddToQueue(q, ip->out());
if (ip->opcode() == kInstAlt || ip->opcode() == kInstAltMatch)
AddToQueue(q, ip->out1());
}
return s;
}
static std::string FlattenedProgToString(Prog* prog, int start) {
std::string s;
for (int id = start; id < prog->size(); id++) {
Prog::Inst* ip = prog->inst(id);
if (ip->last())
s += StringPrintf("%d. %s\n", id, ip->Dump().c_str());
else
s += StringPrintf("%d+ %s\n", id, ip->Dump().c_str());
}
return s;
}
std::string Prog::Dump() {
if (did_flatten_)
return FlattenedProgToString(this, start_);
Workq q(size_);
AddToQueue(&q, start_);
return ProgToString(this, &q);
}
std::string Prog::DumpUnanchored() {
if (did_flatten_)
return FlattenedProgToString(this, start_unanchored_);
Workq q(size_);
AddToQueue(&q, start_unanchored_);
return ProgToString(this, &q);
}
std::string Prog::DumpByteMap() {
std::string map;
for (int c = 0; c < 256; c++) {
int b = bytemap_[c];
int lo = c;
while (c < 256-1 && bytemap_[c+1] == b)
c++;
int hi = c;
map += StringPrintf("[%02x-%02x] -> %d\n", lo, hi, b);
}
return map;
}
// Is ip a guaranteed match at end of text, perhaps after some capturing?
static bool IsMatch(Prog* prog, Prog::Inst* ip) {
for (;;) {
switch (ip->opcode()) {
default:
LOG(DFATAL) << "Unexpected opcode in IsMatch: " << ip->opcode();
return false;
case kInstAlt:
case kInstAltMatch:
case kInstByteRange:
case kInstFail:
case kInstEmptyWidth:
return false;
case kInstCapture:
case kInstNop:
ip = prog->inst(ip->out());
break;
case kInstMatch:
return true;
}
}
}
// Peep-hole optimizer.
void Prog::Optimize() {
Workq q(size_);
// Eliminate nops. Most are taken out during compilation
// but a few are hard to avoid.
q.clear();
AddToQueue(&q, start_);
for (Workq::iterator i = q.begin(); i != q.end(); ++i) {
int id = *i;
Inst* ip = inst(id);
int j = ip->out();
Inst* jp;
while (j != 0 && (jp=inst(j))->opcode() == kInstNop) {
j = jp->out();
}
ip->set_out(j);
AddToQueue(&q, ip->out());
if (ip->opcode() == kInstAlt) {
j = ip->out1();
while (j != 0 && (jp=inst(j))->opcode() == kInstNop) {
j = jp->out();
}
ip->out1_ = j;
AddToQueue(&q, ip->out1());
}
}
// Insert kInstAltMatch instructions
// Look for
// ip: Alt -> j | k
// j: ByteRange [00-FF] -> ip
// k: Match
// or the reverse (the above is the greedy one).
// Rewrite Alt to AltMatch.
q.clear();
AddToQueue(&q, start_);
for (Workq::iterator i = q.begin(); i != q.end(); ++i) {
int id = *i;
Inst* ip = inst(id);
AddToQueue(&q, ip->out());
if (ip->opcode() == kInstAlt)
AddToQueue(&q, ip->out1());
if (ip->opcode() == kInstAlt) {
Inst* j = inst(ip->out());
Inst* k = inst(ip->out1());
if (j->opcode() == kInstByteRange && j->out() == id &&
j->lo() == 0x00 && j->hi() == 0xFF &&
IsMatch(this, k)) {
ip->set_opcode(kInstAltMatch);
continue;
}
if (IsMatch(this, j) &&
k->opcode() == kInstByteRange && k->out() == id &&
k->lo() == 0x00 && k->hi() == 0xFF) {
ip->set_opcode(kInstAltMatch);
}
}
}
}
uint32_t Prog::EmptyFlags(const StringPiece& text, const char* p) {
int flags = 0;
// ^ and \A
if (p == text.data())
flags |= kEmptyBeginText | kEmptyBeginLine;
else if (p[-1] == '\n')
flags |= kEmptyBeginLine;
// $ and \z
if (p == text.data() + text.size())
flags |= kEmptyEndText | kEmptyEndLine;
else if (p < text.data() + text.size() && p[0] == '\n')
flags |= kEmptyEndLine;
// \b and \B
if (p == text.data() && p == text.data() + text.size()) {
// no word boundary here
} else if (p == text.data()) {
if (IsWordChar(p[0]))
flags |= kEmptyWordBoundary;
} else if (p == text.data() + text.size()) {
if (IsWordChar(p[-1]))
flags |= kEmptyWordBoundary;
} else {
if (IsWordChar(p[-1]) != IsWordChar(p[0]))
flags |= kEmptyWordBoundary;
}
if (!(flags & kEmptyWordBoundary))
flags |= kEmptyNonWordBoundary;
return flags;
}
// ByteMapBuilder implements a coloring algorithm.
//
// The first phase is a series of "mark and merge" batches: we mark one or more
// [lo-hi] ranges, then merge them into our internal state. Batching is not for
// performance; rather, it means that the ranges are treated indistinguishably.
//
// Internally, the ranges are represented using a bitmap that stores the splits
// and a vector that stores the colors; both of them are indexed by the ranges'
// last bytes. Thus, in order to merge a [lo-hi] range, we split at lo-1 and at
// hi (if not already split), then recolor each range in between. The color map
// (i.e. from the old color to the new color) is maintained for the lifetime of
// the batch and so underpins this somewhat obscure approach to set operations.
//
// The second phase builds the bytemap from our internal state: we recolor each
// range, then store the new color (which is now the byte class) in each of the
// corresponding array elements. Finally, we output the number of byte classes.
class ByteMapBuilder {
public:
ByteMapBuilder() {
// Initial state: the [0-255] range has color 256.
// This will avoid problems during the second phase,
// in which we assign byte classes numbered from 0.
splits_.Set(255);
colors_[255] = 256;
nextcolor_ = 257;
}
void Mark(int lo, int hi);
void Merge();
void Build(uint8_t* bytemap, int* bytemap_range);
private:
int Recolor(int oldcolor);
Bitmap256 splits_;
int colors_[256];
int nextcolor_;
std::vector<std::pair<int, int>> colormap_;
std::vector<std::pair<int, int>> ranges_;
ByteMapBuilder(const ByteMapBuilder&) = delete;
ByteMapBuilder& operator=(const ByteMapBuilder&) = delete;
};
void ByteMapBuilder::Mark(int lo, int hi) {
DCHECK_GE(lo, 0);
DCHECK_GE(hi, 0);
DCHECK_LE(lo, 255);
DCHECK_LE(hi, 255);
DCHECK_LE(lo, hi);
// Ignore any [0-255] ranges. They cause us to recolor every range, which
// has no effect on the eventual result and is therefore a waste of time.
if (lo == 0 && hi == 255)
return;
ranges_.emplace_back(lo, hi);
}
void ByteMapBuilder::Merge() {
for (std::vector<std::pair<int, int>>::const_iterator it = ranges_.begin();
it != ranges_.end();
++it) {
int lo = it->first-1;
int hi = it->second;
if (0 <= lo && !splits_.Test(lo)) {
splits_.Set(lo);
int next = splits_.FindNextSetBit(lo+1);
colors_[lo] = colors_[next];
}
if (!splits_.Test(hi)) {
splits_.Set(hi);
int next = splits_.FindNextSetBit(hi+1);
colors_[hi] = colors_[next];
}
int c = lo+1;
while (c < 256) {
int next = splits_.FindNextSetBit(c);
colors_[next] = Recolor(colors_[next]);
if (next == hi)
break;
c = next+1;
}
}
colormap_.clear();
ranges_.clear();
}
void ByteMapBuilder::Build(uint8_t* bytemap, int* bytemap_range) {
// Assign byte classes numbered from 0.
nextcolor_ = 0;
int c = 0;
while (c < 256) {
int next = splits_.FindNextSetBit(c);
uint8_t b = static_cast<uint8_t>(Recolor(colors_[next]));
while (c <= next) {
bytemap[c] = b;
c++;
}
}
*bytemap_range = nextcolor_;
}
int ByteMapBuilder::Recolor(int oldcolor) {
// Yes, this is a linear search. There can be at most 256
// colors and there will typically be far fewer than that.
// Also, we need to consider keys *and* values in order to
// avoid recoloring a given range more than once per batch.
std::vector<std::pair<int, int>>::const_iterator it =
std::find_if(colormap_.begin(), colormap_.end(),
[=](const std::pair<int, int>& kv) -> bool {
return kv.first == oldcolor || kv.second == oldcolor;
});
if (it != colormap_.end())
return it->second;
int newcolor = nextcolor_;
nextcolor_++;
colormap_.emplace_back(oldcolor, newcolor);
return newcolor;
}
void Prog::ComputeByteMap() {
// Fill in bytemap with byte classes for the program.
// Ranges of bytes that are treated indistinguishably
// will be mapped to a single byte class.
ByteMapBuilder builder;
// Don't repeat the work for ^ and $.
bool marked_line_boundaries = false;
// Don't repeat the work for \b and \B.
bool marked_word_boundaries = false;
for (int id = 0; id < size(); id++) {
Inst* ip = inst(id);
if (ip->opcode() == kInstByteRange) {
int lo = ip->lo();
int hi = ip->hi();
builder.Mark(lo, hi);
if (ip->foldcase() && lo <= 'z' && hi >= 'a') {
int foldlo = lo;
int foldhi = hi;
if (foldlo < 'a')
foldlo = 'a';
if (foldhi > 'z')
foldhi = 'z';
if (foldlo <= foldhi) {
foldlo += 'A' - 'a';
foldhi += 'A' - 'a';
builder.Mark(foldlo, foldhi);
}
}
// If this Inst is not the last Inst in its list AND the next Inst is
// also a ByteRange AND the Insts have the same out, defer the merge.
if (!ip->last() &&
inst(id+1)->opcode() == kInstByteRange &&
ip->out() == inst(id+1)->out())
continue;
builder.Merge();
} else if (ip->opcode() == kInstEmptyWidth) {
if (ip->empty() & (kEmptyBeginLine|kEmptyEndLine) &&
!marked_line_boundaries) {
builder.Mark('\n', '\n');
builder.Merge();
marked_line_boundaries = true;
}
if (ip->empty() & (kEmptyWordBoundary|kEmptyNonWordBoundary) &&
!marked_word_boundaries) {
// We require two batches here: the first for ranges that are word
// characters, the second for ranges that are not word characters.
for (bool isword : {true, false}) {
int j;
for (int i = 0; i < 256; i = j) {
for (j = i + 1; j < 256 &&
Prog::IsWordChar(static_cast<uint8_t>(i)) ==
Prog::IsWordChar(static_cast<uint8_t>(j));
j++)
;
if (Prog::IsWordChar(static_cast<uint8_t>(i)) == isword)
builder.Mark(i, j - 1);
}
builder.Merge();
}
marked_word_boundaries = true;
}
}
}
builder.Build(bytemap_, &bytemap_range_);
if ((0)) { // For debugging, use trivial bytemap.
LOG(ERROR) << "Using trivial bytemap.";
for (int i = 0; i < 256; i++)
bytemap_[i] = static_cast<uint8_t>(i);
bytemap_range_ = 256;
}
}
// Prog::Flatten() implements a graph rewriting algorithm.
//
// The overall process is similar to epsilon removal, but retains some epsilon
// transitions: those from Capture and EmptyWidth instructions; and those from
// nullable subexpressions. (The latter avoids quadratic blowup in transitions
// in the worst case.) It might be best thought of as Alt instruction elision.
//
// In conceptual terms, it divides the Prog into "trees" of instructions, then
// traverses the "trees" in order to produce "lists" of instructions. A "tree"
// is one or more instructions that grow from one "root" instruction to one or
// more "leaf" instructions; if a "tree" has exactly one instruction, then the
// "root" is also the "leaf". In most cases, a "root" is the successor of some
// "leaf" (i.e. the "leaf" instruction's out() returns the "root" instruction)
// and is considered a "successor root". A "leaf" can be a ByteRange, Capture,
// EmptyWidth or Match instruction. However, this is insufficient for handling
// nested nullable subexpressions correctly, so in some cases, a "root" is the
// dominator of the instructions reachable from some "successor root" (i.e. it
// has an unreachable predecessor) and is considered a "dominator root". Since
// only Alt instructions can be "dominator roots" (other instructions would be
// "leaves"), only Alt instructions are required to be marked as predecessors.
//
// Dividing the Prog into "trees" comprises two passes: marking the "successor
// roots" and the predecessors; and marking the "dominator roots". Sorting the
// "successor roots" by their bytecode offsets enables iteration in order from
// greatest to least during the second pass; by working backwards in this case
// and flooding the graph no further than "leaves" and already marked "roots",
// it becomes possible to mark "dominator roots" without doing excessive work.
//
// Traversing the "trees" is just iterating over the "roots" in order of their
// marking and flooding the graph no further than "leaves" and "roots". When a
// "leaf" is reached, the instruction is copied with its successor remapped to
// its "root" number. When a "root" is reached, a Nop instruction is generated
// with its successor remapped similarly. As each "list" is produced, its last
// instruction is marked as such. After all of the "lists" have been produced,
// a pass over their instructions remaps their successors to bytecode offsets.
void Prog::Flatten() {
if (did_flatten_)
return;
did_flatten_ = true;
// Scratch structures. It's important that these are reused by functions
// that we call in loops because they would thrash the heap otherwise.
SparseSet reachable(size());
std::vector<int> stk;
stk.reserve(size());
// First pass: Marks "successor roots" and predecessors.
// Builds the mapping from inst-ids to root-ids.
SparseArray<int> rootmap(size());
SparseArray<int> predmap(size());
std::vector<std::vector<int>> predvec;
MarkSuccessors(&rootmap, &predmap, &predvec, &reachable, &stk);
// Second pass: Marks "dominator roots".
SparseArray<int> sorted(rootmap);
std::sort(sorted.begin(), sorted.end(), sorted.less);
for (SparseArray<int>::const_iterator i = sorted.end() - 1;
i != sorted.begin();
--i) {
if (i->index() != start_unanchored() && i->index() != start())
MarkDominator(i->index(), &rootmap, &predmap, &predvec, &reachable, &stk);
}
// Third pass: Emits "lists". Remaps outs to root-ids.
// Builds the mapping from root-ids to flat-ids.
std::vector<int> flatmap(rootmap.size());
std::vector<Inst> flat;
flat.reserve(size());
for (SparseArray<int>::const_iterator i = rootmap.begin();
i != rootmap.end();
++i) {
flatmap[i->value()] = static_cast<int>(flat.size());
EmitList(i->index(), &rootmap, &flat, &reachable, &stk);
flat.back().set_last();
// We have the bounds of the "list", so this is the
// most convenient point at which to compute hints.
ComputeHints(&flat, flatmap[i->value()], static_cast<int>(flat.size()));
}
list_count_ = static_cast<int>(flatmap.size());
for (int i = 0; i < kNumInst; i++)
inst_count_[i] = 0;
// Fourth pass: Remaps outs to flat-ids.
// Counts instructions by opcode.
for (int id = 0; id < static_cast<int>(flat.size()); id++) {
Inst* ip = &flat[id];
if (ip->opcode() != kInstAltMatch) // handled in EmitList()
ip->set_out(flatmap[ip->out()]);
inst_count_[ip->opcode()]++;
}
#if !defined(NDEBUG)
// Address a `-Wunused-but-set-variable' warning from Clang 13.x.
size_t total = 0;
for (int i = 0; i < kNumInst; i++)
total += inst_count_[i];
CHECK_EQ(total, flat.size());
#endif
// Remap start_unanchored and start.
if (start_unanchored() == 0) {
DCHECK_EQ(start(), 0);
} else if (start_unanchored() == start()) {
set_start_unanchored(flatmap[1]);
set_start(flatmap[1]);
} else {
set_start_unanchored(flatmap[1]);
set_start(flatmap[2]);
}
// Finally, replace the old instructions with the new instructions.
size_ = static_cast<int>(flat.size());
inst_ = PODArray<Inst>(size_);
memmove(inst_.data(), flat.data(), size_*sizeof inst_[0]);
// Populate the list heads for BitState.
// 512 instructions limits the memory footprint to 1KiB.
if (size_ <= 512) {
list_heads_ = PODArray<uint16_t>(size_);
// 0xFF makes it more obvious if we try to look up a non-head.
memset(list_heads_.data(), 0xFF, size_*sizeof list_heads_[0]);
for (int i = 0; i < list_count_; ++i)
list_heads_[flatmap[i]] = i;
}
// BitState allocates a bitmap of size list_count_ * (text.size()+1)
// for tracking pairs of possibilities that it has already explored.
const size_t kBitStateBitmapMaxSize = 256*1024; // max size in bits
bit_state_text_max_size_ = kBitStateBitmapMaxSize / list_count_ - 1;
}
void Prog::MarkSuccessors(SparseArray<int>* rootmap,
SparseArray<int>* predmap,
std::vector<std::vector<int>>* predvec,
SparseSet* reachable, std::vector<int>* stk) {
// Mark the kInstFail instruction.
rootmap->set_new(0, rootmap->size());
// Mark the start_unanchored and start instructions.
if (!rootmap->has_index(start_unanchored()))
rootmap->set_new(start_unanchored(), rootmap->size());
if (!rootmap->has_index(start()))
rootmap->set_new(start(), rootmap->size());
reachable->clear();
stk->clear();
stk->push_back(start_unanchored());
while (!stk->empty()) {
int id = stk->back();
stk->pop_back();
Loop:
if (reachable->contains(id))
continue;
reachable->insert_new(id);
Inst* ip = inst(id);
switch (ip->opcode()) {
default:
LOG(DFATAL) << "unhandled opcode: " << ip->opcode();
break;
case kInstAltMatch:
case kInstAlt:
// Mark this instruction as a predecessor of each out.
for (int out : {ip->out(), ip->out1()}) {
if (!predmap->has_index(out)) {
predmap->set_new(out, static_cast<int>(predvec->size()));
predvec->emplace_back();
}
(*predvec)[predmap->get_existing(out)].emplace_back(id);
}
stk->push_back(ip->out1());
id = ip->out();
goto Loop;
case kInstByteRange:
case kInstCapture:
case kInstEmptyWidth:
// Mark the out of this instruction as a "root".
if (!rootmap->has_index(ip->out()))
rootmap->set_new(ip->out(), rootmap->size());
id = ip->out();
goto Loop;
case kInstNop:
id = ip->out();
goto Loop;
case kInstMatch:
case kInstFail:
break;
}
}
}
void Prog::MarkDominator(int root, SparseArray<int>* rootmap,
SparseArray<int>* predmap,
std::vector<std::vector<int>>* predvec,
SparseSet* reachable, std::vector<int>* stk) {
reachable->clear();
stk->clear();
stk->push_back(root);
while (!stk->empty()) {
int id = stk->back();
stk->pop_back();
Loop:
if (reachable->contains(id))
continue;
reachable->insert_new(id);
if (id != root && rootmap->has_index(id)) {
// We reached another "tree" via epsilon transition.
continue;
}
Inst* ip = inst(id);
switch (ip->opcode()) {
default:
LOG(DFATAL) << "unhandled opcode: " << ip->opcode();
break;
case kInstAltMatch:
case kInstAlt:
stk->push_back(ip->out1());
id = ip->out();
goto Loop;
case kInstByteRange:
case kInstCapture:
case kInstEmptyWidth:
break;
case kInstNop:
id = ip->out();
goto Loop;
case kInstMatch:
case kInstFail:
break;
}
}
for (SparseSet::const_iterator i = reachable->begin();
i != reachable->end();
++i) {
int id = *i;
if (predmap->has_index(id)) {
for (int pred : (*predvec)[predmap->get_existing(id)]) {
if (!reachable->contains(pred)) {
// id has a predecessor that cannot be reached from root!
// Therefore, id must be a "root" too - mark it as such.
if (!rootmap->has_index(id))
rootmap->set_new(id, rootmap->size());
}
}
}
}
}
void Prog::EmitList(int root, SparseArray<int>* rootmap,
std::vector<Inst>* flat,
SparseSet* reachable, std::vector<int>* stk) {
reachable->clear();
stk->clear();
stk->push_back(root);
while (!stk->empty()) {
int id = stk->back();
stk->pop_back();
Loop:
if (reachable->contains(id))
continue;
reachable->insert_new(id);
if (id != root && rootmap->has_index(id)) {
// We reached another "tree" via epsilon transition. Emit a kInstNop
// instruction so that the Prog does not become quadratically larger.
flat->emplace_back();
flat->back().set_opcode(kInstNop);
flat->back().set_out(rootmap->get_existing(id));
continue;
}
Inst* ip = inst(id);
switch (ip->opcode()) {
default:
LOG(DFATAL) << "unhandled opcode: " << ip->opcode();
break;
case kInstAltMatch:
flat->emplace_back();
flat->back().set_opcode(kInstAltMatch);
flat->back().set_out(static_cast<int>(flat->size()));
flat->back().out1_ = static_cast<uint32_t>(flat->size())+1;
FALLTHROUGH_INTENDED;
case kInstAlt:
stk->push_back(ip->out1());
id = ip->out();
goto Loop;
case kInstByteRange:
case kInstCapture:
case kInstEmptyWidth:
flat->emplace_back();
memmove(&flat->back(), ip, sizeof *ip);
flat->back().set_out(rootmap->get_existing(ip->out()));
break;
case kInstNop:
id = ip->out();
goto Loop;
case kInstMatch:
case kInstFail:
flat->emplace_back();
memmove(&flat->back(), ip, sizeof *ip);
break;
}
}
}
// For each ByteRange instruction in [begin, end), computes a hint to execution
// engines: the delta to the next instruction (in flat) worth exploring iff the
// current instruction matched.
//
// Implements a coloring algorithm related to ByteMapBuilder, but in this case,
// colors are instructions and recoloring ranges precisely identifies conflicts
// between instructions. Iterating backwards over [begin, end) is guaranteed to
// identify the nearest conflict (if any) with only linear complexity.
void Prog::ComputeHints(std::vector<Inst>* flat, int begin, int end) {
Bitmap256 splits;
int colors[256];
bool dirty = false;
for (int id = end; id >= begin; --id) {
if (id == end ||
(*flat)[id].opcode() != kInstByteRange) {
if (dirty) {
dirty = false;
splits.Clear();
}
splits.Set(255);
colors[255] = id;
// At this point, the [0-255] range is colored with id.
// Thus, hints cannot point beyond id; and if id == end,
// hints that would have pointed to id will be 0 instead.
continue;
}
dirty = true;
// We recolor the [lo-hi] range with id. Note that first ratchets backwards
// from end to the nearest conflict (if any) during recoloring.
int first = end;
auto Recolor = [&](int lo, int hi) {
// Like ByteMapBuilder, we split at lo-1 and at hi.
--lo;
if (0 <= lo && !splits.Test(lo)) {
splits.Set(lo);
int next = splits.FindNextSetBit(lo+1);
colors[lo] = colors[next];
}
if (!splits.Test(hi)) {
splits.Set(hi);
int next = splits.FindNextSetBit(hi+1);
colors[hi] = colors[next];
}
int c = lo+1;
while (c < 256) {
int next = splits.FindNextSetBit(c);
// Ratchet backwards...
first = std::min(first, colors[next]);
// Recolor with id - because it's the new nearest conflict!
colors[next] = id;
if (next == hi)
break;
c = next+1;
}
};
Inst* ip = &(*flat)[id];
int lo = ip->lo();
int hi = ip->hi();
Recolor(lo, hi);
if (ip->foldcase() && lo <= 'z' && hi >= 'a') {
int foldlo = lo;
int foldhi = hi;
if (foldlo < 'a')
foldlo = 'a';
if (foldhi > 'z')
foldhi = 'z';
if (foldlo <= foldhi) {
foldlo += 'A' - 'a';
foldhi += 'A' - 'a';
Recolor(foldlo, foldhi);
}
}
if (first != end) {
uint16_t hint = static_cast<uint16_t>(std::min(first - id, 32767));
ip->hint_foldcase_ |= hint<<1;
}
}
}
// The final state will always be this, which frees up a register for the hot
// loop and thus avoids the spilling that can occur when building with Clang.
static const size_t kShiftDFAFinal = 9;
// This function takes the prefix as std::string (i.e. not const std::string&
// as normal) because it's going to clobber it, so a temporary is convenient.
static uint64_t* BuildShiftDFA(std::string prefix) {
// This constant is for convenience now and also for correctness later when
// we clobber the prefix, but still need to know how long it was initially.
const size_t size = prefix.size();
// Construct the NFA.
// The table is indexed by input byte; each element is a bitfield of states
// reachable by the input byte. Given a bitfield of the current states, the
// bitfield of states reachable from those is - for this specific purpose -
// always ((ncurr << 1) | 1). Intersecting the reachability bitfields gives
// the bitfield of the next states reached by stepping over the input byte.
// Credits for this technique: the Hyperscan paper by Geoff Langdale et al.
uint16_t nfa[256]{};
for (size_t i = 0; i < size; ++i) {
uint8_t b = prefix[i];
nfa[b] |= 1 << (i+1);
}
// This is the `\C*?` for unanchored search.
for (int b = 0; b < 256; ++b)
nfa[b] |= 1;
// This maps from DFA state to NFA states; the reverse mapping is used when
// recording transitions and gets implemented with plain old linear search.
// The "Shift DFA" technique limits this to ten states when using uint64_t;
// to allow for the initial state, we use at most nine bytes of the prefix.
// That same limit is also why uint16_t is sufficient for the NFA bitfield.
uint16_t states[kShiftDFAFinal+1]{};
states[0] = 1;
for (size_t dcurr = 0; dcurr < size; ++dcurr) {
uint8_t b = prefix[dcurr];
uint16_t ncurr = states[dcurr];
uint16_t nnext = nfa[b] & ((ncurr << 1) | 1);
size_t dnext = dcurr+1;
if (dnext == size)
dnext = kShiftDFAFinal;
states[dnext] = nnext;
}
// Sort and unique the bytes of the prefix to avoid repeating work while we
// record transitions. This clobbers the prefix, but it's no longer needed.
std::sort(prefix.begin(), prefix.end());
prefix.erase(std::unique(prefix.begin(), prefix.end()), prefix.end());
// Construct the DFA.
// The table is indexed by input byte; each element is effectively a packed
// array of uint6_t; each array value will be multiplied by six in order to
// avoid having to do so later in the hot loop as well as masking/shifting.
// Credits for this technique: "Shift-based DFAs" on GitHub by Per Vognsen.
uint64_t* dfa = new uint64_t[256]{};
// Record a transition from each state for each of the bytes of the prefix.
// Note that all other input bytes go back to the initial state by default.
for (size_t dcurr = 0; dcurr < size; ++dcurr) {
for (uint8_t b : prefix) {
uint16_t ncurr = states[dcurr];
uint16_t nnext = nfa[b] & ((ncurr << 1) | 1);
size_t dnext = 0;
while (states[dnext] != nnext)
++dnext;
dfa[b] |= static_cast<uint64_t>(dnext * 6) << (dcurr * 6);
// Convert ASCII letters to uppercase and record the extra transitions.
// Note that ASCII letters are guaranteed to be lowercase at this point
// because that's how the parser normalises them. #FunFact: 'k' and 's'
// match U+212A and U+017F, respectively, so they won't occur here when
// using UTF-8 encoding because the parser will emit character classes.
if ('a' <= b && b <= 'z') {
b -= 'a' - 'A';
dfa[b] |= static_cast<uint64_t>(dnext * 6) << (dcurr * 6);
}
}
}
// This lets the final state "saturate", which will matter for performance:
// in the hot loop, we check for a match only at the end of each iteration,
// so we must keep signalling the match until we get around to checking it.
for (int b = 0; b < 256; ++b)
dfa[b] |= static_cast<uint64_t>(kShiftDFAFinal * 6) << (kShiftDFAFinal * 6);
return dfa;
}
void Prog::ConfigurePrefixAccel(const std::string& prefix,
bool prefix_foldcase) {
prefix_foldcase_ = prefix_foldcase;
prefix_size_ = prefix.size();
if (prefix_foldcase_) {
// Use PrefixAccel_ShiftDFA().
// ... and no more than nine bytes of the prefix. (See above for details.)
prefix_size_ = std::min(prefix_size_, kShiftDFAFinal);
prefix_dfa_ = BuildShiftDFA(prefix.substr(0, prefix_size_));
} else if (prefix_size_ != 1) {
// Use PrefixAccel_FrontAndBack().
prefix_front_ = prefix.front();
prefix_back_ = prefix.back();
} else {
// Use memchr(3).
prefix_front_ = prefix.front();
}
}
const void* Prog::PrefixAccel_ShiftDFA(const void* data, size_t size) {
if (size < prefix_size_)
return NULL;
uint64_t curr = 0;
// At the time of writing, rough benchmarks on a Broadwell machine showed
// that this unroll factor (i.e. eight) achieves a speedup factor of two.
if (size >= 8) {
const uint8_t* p = reinterpret_cast<const uint8_t*>(data);
const uint8_t* endp = p + (size&~7);
do {
uint8_t b0 = p[0];
uint8_t b1 = p[1];
uint8_t b2 = p[2];
uint8_t b3 = p[3];
uint8_t b4 = p[4];
uint8_t b5 = p[5];
uint8_t b6 = p[6];
uint8_t b7 = p[7];
uint64_t next0 = prefix_dfa_[b0];
uint64_t next1 = prefix_dfa_[b1];
uint64_t next2 = prefix_dfa_[b2];
uint64_t next3 = prefix_dfa_[b3];
uint64_t next4 = prefix_dfa_[b4];
uint64_t next5 = prefix_dfa_[b5];
uint64_t next6 = prefix_dfa_[b6];
uint64_t next7 = prefix_dfa_[b7];
uint64_t curr0 = next0 >> (curr & 63);
uint64_t curr1 = next1 >> (curr0 & 63);
uint64_t curr2 = next2 >> (curr1 & 63);
uint64_t curr3 = next3 >> (curr2 & 63);
uint64_t curr4 = next4 >> (curr3 & 63);
uint64_t curr5 = next5 >> (curr4 & 63);
uint64_t curr6 = next6 >> (curr5 & 63);
uint64_t curr7 = next7 >> (curr6 & 63);
if ((curr7 & 63) == kShiftDFAFinal * 6) {
// At the time of writing, using the same masking subexpressions from
// the preceding lines caused Clang to clutter the hot loop computing
// them - even though they aren't actually needed for shifting! Hence
// these rewritten conditions, which achieve a speedup factor of two.
if (((curr7-curr0) & 63) == 0) return p+1-prefix_size_;
if (((curr7-curr1) & 63) == 0) return p+2-prefix_size_;
if (((curr7-curr2) & 63) == 0) return p+3-prefix_size_;
if (((curr7-curr3) & 63) == 0) return p+4-prefix_size_;
if (((curr7-curr4) & 63) == 0) return p+5-prefix_size_;
if (((curr7-curr5) & 63) == 0) return p+6-prefix_size_;
if (((curr7-curr6) & 63) == 0) return p+7-prefix_size_;
if (((curr7-curr7) & 63) == 0) return p+8-prefix_size_;
}
curr = curr7;
p += 8;
} while (p != endp);
data = p;
size = size&7;
}
const uint8_t* p = reinterpret_cast<const uint8_t*>(data);
const uint8_t* endp = p + size;
while (p != endp) {
uint8_t b = *p++;
uint64_t next = prefix_dfa_[b];
curr = next >> (curr & 63);
if ((curr & 63) == kShiftDFAFinal * 6)
return p-prefix_size_;
}
return NULL;
}
#if defined(__AVX2__)
// Finds the least significant non-zero bit in n.
static int FindLSBSet(uint32_t n) {
DCHECK_NE(n, 0);
#if defined(__GNUC__)
return __builtin_ctz(n);
#elif defined(_MSC_VER) && (defined(_M_X64) || defined(_M_IX86))
unsigned long c;
_BitScanForward(&c, n);
return static_cast<int>(c);
#else
int c = 31;
for (int shift = 1 << 4; shift != 0; shift >>= 1) {
uint32_t word = n << shift;
if (word != 0) {
n = word;
c -= shift;
}
}
return c;
#endif
}
#endif
const void* Prog::PrefixAccel_FrontAndBack(const void* data, size_t size) {
DCHECK_GE(prefix_size_, 2);
if (size < prefix_size_)
return NULL;
// Don't bother searching the last prefix_size_-1 bytes for prefix_front_.
// This also means that probing for prefix_back_ doesn't go out of bounds.
size -= prefix_size_-1;
#if defined(__AVX2__)
// Use AVX2 to look for prefix_front_ and prefix_back_ 32 bytes at a time.
if (size >= sizeof(__m256i)) {
const __m256i* fp = reinterpret_cast<const __m256i*>(
reinterpret_cast<const char*>(data));
const __m256i* bp = reinterpret_cast<const __m256i*>(
reinterpret_cast<const char*>(data) + prefix_size_-1);
const __m256i* endfp = fp + size/sizeof(__m256i);
const __m256i f_set1 = _mm256_set1_epi8(prefix_front_);
const __m256i b_set1 = _mm256_set1_epi8(prefix_back_);
do {
const __m256i f_loadu = _mm256_loadu_si256(fp++);
const __m256i b_loadu = _mm256_loadu_si256(bp++);
const __m256i f_cmpeq = _mm256_cmpeq_epi8(f_set1, f_loadu);
const __m256i b_cmpeq = _mm256_cmpeq_epi8(b_set1, b_loadu);
const int fb_testz = _mm256_testz_si256(f_cmpeq, b_cmpeq);
if (fb_testz == 0) { // ZF: 1 means zero, 0 means non-zero.
const __m256i fb_and = _mm256_and_si256(f_cmpeq, b_cmpeq);
const int fb_movemask = _mm256_movemask_epi8(fb_and);
const int fb_ctz = FindLSBSet(fb_movemask);
return reinterpret_cast<const char*>(fp-1) + fb_ctz;
}
} while (fp != endfp);
data = fp;
size = size%sizeof(__m256i);
}
#endif
const char* p0 = reinterpret_cast<const char*>(data);
for (const char* p = p0;; p++) {
DCHECK_GE(size, static_cast<size_t>(p-p0));
p = reinterpret_cast<const char*>(memchr(p, prefix_front_, size - (p-p0)));
if (p == NULL || p[prefix_size_-1] == prefix_back_)
return p;
}
}
} // namespace re2