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verilator/src/V3GraphDfa.cpp
Wilson Snyder 5811ec07e6 Update URLs to https://verilator.org
2019-11-07 22:33:59 -05:00

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// -*- mode: C++; c-file-style: "cc-mode" -*-
//*************************************************************************
// DESCRIPTION: Verilator: Graph optimizations
//
// Code available from: https://verilator.org
//
//*************************************************************************
//
// Copyright 2005-2019 by Wilson Snyder. This program is free software; you can
// redistribute it and/or modify it under the terms of either the GNU
// Lesser General Public License Version 3 or the Perl Artistic License
// Version 2.0.
//
// Verilator is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
//*************************************************************************
#include "config_build.h"
#include "verilatedos.h"
#include "V3Global.h"
#include "V3GraphDfa.h"
#include "V3GraphAlg.h"
#include <cstdarg>
#include <map>
#include <set>
#include <stack>
//######################################################################
//######################################################################
// Algorithms - find starting node
DfaVertex* DfaGraph::findStart() {
DfaVertex* startp = NULL;
for (V3GraphVertex* vertexp = this->verticesBeginp();
vertexp; vertexp=vertexp->verticesNextp()) {
if (DfaVertex* vvertexp = dynamic_cast<DfaVertex*>(vertexp)) {
if (vvertexp->start()) {
UASSERT_OBJ(!startp, vertexp, "Multiple start points in NFA graph");
startp = vvertexp;
}
} else {
vertexp->v3fatalSrc("Non DfaVertex in DfaGraph");
}
}
if (!startp) v3fatalSrc("No start point in NFA graph");
return startp;
}
//######################################################################
//######################################################################
// Algorithms - convert NFA to a DFA
// Uses the Subset Construction Algorithm
class GraphNfaToDfa : GraphAlg<> {
// We have two types of nodes in one graph, NFA and DFA nodes.
// Edges from NFA to NFA come from the user, and indicate input or epsilon transitions
// Edges from DFA to NFA indicate the NFA from which that DFA was formed.
// Edges from DFA to DFA indicate a completed input transition
private:
// TYPES
typedef std::deque<DfaVertex*> DfaStates;
typedef std::multimap<vluint64_t,DfaVertex*> HashMap;
// MEMBERS
uint32_t m_step; // Processing step, so we can avoid clearUser all the time
HashMap m_hashMap; // Dfa Vertex for each set of NFA vertexes
#ifdef VL_CPPCHECK
static int debug() { return 9; }
#else
static int debug() { return 0; }
#endif
// METHODS
DfaGraph* graphp() { return static_cast<DfaGraph*>(m_graphp); }
bool nfaState(V3GraphVertex* vertexp) { return vertexp->color()==0; }
//bool dfaState(V3GraphVertex* vertexp) { return vertexp->color()==1; }
void nextStep() { m_step++; }
bool unseenNfaThisStep(V3GraphVertex* vertexp) {
// A nfa node not already seen this processing step
return (nfaState(vertexp) && !(vertexp->user()==m_step));
}
DfaVertex* newDfaVertex(DfaVertex* nfaTemplatep=NULL) {
DfaVertex* vertexp = new DfaVertex(graphp());
vertexp->color(1); // Mark as dfa
if (nfaTemplatep && nfaTemplatep->start()) vertexp->start(true);
if (nfaTemplatep && nfaTemplatep->accepting()) vertexp->accepting(true);
UINFO(9, " New "<<vertexp<<endl);
return vertexp;
}
// Hashing
static uint32_t hashVertex(V3GraphVertex* vertexp) {
union { void* up; struct {uint32_t upper; uint32_t lower;} l;} u;
u.l.upper = 0; u.l.lower = 0; u.up = vertexp;
return u.l.upper ^ u.l.lower;
}
uint32_t hashDfaOrigins(DfaVertex* dfaStatep) {
// Find the NFA states this dfa came from,
// Record a checksum, so we can search for it later by the list of nfa nodes.
// The order of the nodes is not deterministic; the hash thus must
// not depend on order of edges
uint32_t hash = 0;
// Foreach NFA state (this DFA state was formed from)
if (debug()) nextStep();
for (V3GraphEdge* dfaEdgep = dfaStatep->outBeginp();
dfaEdgep; dfaEdgep=dfaEdgep->outNextp()) {
if (nfaState(dfaEdgep->top())) {
DfaVertex* nfaStatep = static_cast<DfaVertex*>(dfaEdgep->top());
hash ^= hashVertex(nfaStatep);
if (debug()) {
UASSERT_OBJ(nfaStatep->user() != m_step, nfaStatep,
"DFA state points to duplicate NFA state.");
nfaStatep->user(m_step);
}
}
}
return hash;
}
uint32_t hashDfaOrigins(const DfaStates& nfasWithInput) {
// Find the NFA states this dfa came from,
uint32_t hash = 0;
for (DfaStates::const_iterator nfaIt=nfasWithInput.begin();
nfaIt!=nfasWithInput.end(); ++nfaIt) {
DfaVertex* nfaStatep = *nfaIt;
hash ^= hashVertex(nfaStatep);
}
return hash;
}
bool compareDfaOrigins(const DfaStates& nfasWithInput, DfaVertex* dfa2p) {
// Return true if the NFA nodes both DFAs came from are the same list
// Assume there are no duplicates in either input list or NFAs under dfa2
nextStep();
// Mark all input vertexes
int num1s = 0;
for (DfaStates::const_iterator nfaIt=nfasWithInput.begin();
nfaIt!=nfasWithInput.end(); ++nfaIt) {
DfaVertex* nfaStatep = *nfaIt;
nfaStatep->user(m_step);
num1s++;
}
if (!num1s) v3fatalSrc("DFA node construction that contains no NFA states");
// Check comparison; must all be marked
// (Check all in dfa2p were in dfa1p)
int num2s = 0;
for (V3GraphEdge* dfaEdgep = dfa2p->outBeginp(); dfaEdgep; dfaEdgep=dfaEdgep->outNextp()) {
if (nfaState(dfaEdgep->top())) {
if (dfaEdgep->top()->user() != m_step) return false;
num2s++;
}
}
// If we saw all of the nodes, then they have the same number of hits
// (Else something in dfa1p that wasn't in dfa2p)
return (num1s == num2s);
}
void insertDfaOrigins(DfaVertex* dfaStatep) {
// Record the NFA states this dfa came from
uint32_t hash = hashDfaOrigins(dfaStatep);
m_hashMap.insert(make_pair(hash, dfaStatep));
}
DfaVertex* findDfaOrigins(const DfaStates& nfasWithInput) {
// Find another DFA state which comes from the identical set of NFA states
// The order of the nodes is not deterministic; the hash thus must
// not depend on order of edges
uint32_t hash = hashDfaOrigins(nfasWithInput);
std::pair<HashMap::iterator,HashMap::iterator> eqrange = m_hashMap.equal_range(hash);
for (HashMap::iterator it = eqrange.first; it != eqrange.second; ++it) {
DfaVertex* testp = it->second;
if (compareDfaOrigins(nfasWithInput, testp)) {
UINFO(9," DFA match for set: "<<testp<<endl);
return testp; // Identical
}
}
return NULL; // No match
}
void findNfasWithInput(DfaVertex* dfaStatep, DfaInput input,
DfaStates& nfasWithInput) {
// Return all NFA states, with the given input transition from
// the nfa states a given dfa state was constructed from.
nextStep();
nfasWithInput.clear(); // NFAs with given input
// Foreach NFA state (this DFA state was formed from)
for (V3GraphEdge* dfaEdgep = dfaStatep->outBeginp();
dfaEdgep; dfaEdgep=dfaEdgep->outNextp()) {
if (nfaState(dfaEdgep->top())) {
DfaVertex* nfaStatep = static_cast<DfaVertex*>(dfaEdgep->top());
// Foreach input transition (on this nfaStatep)
for (V3GraphEdge* nfaEdgep = nfaStatep->outBeginp();
nfaEdgep; nfaEdgep=nfaEdgep->outNextp()) {
DfaEdge* cNfaEdgep = static_cast<DfaEdge*>(nfaEdgep);
if (cNfaEdgep->input().toNodep() == input.toNodep()) {
DfaVertex* nextStatep = static_cast<DfaVertex*>(cNfaEdgep->top());
if (unseenNfaThisStep(nextStatep)) { // Not processed?
nfasWithInput.push_back(nextStatep);
nextStatep->user(m_step);
UINFO(9," Reachable "<<nextStatep<<endl);
}
}
}
}
}
// Expand the nfasWithInput list to include epsilon states
// reachable by those on nfasWithInput
{
DfaStates nfasTodo = nfasWithInput;
nfasWithInput.clear(); // Now the completed list
while (!nfasTodo.empty()) {
DfaVertex* nfaStatep = nfasTodo.front(); nfasTodo.pop_front();
nfasWithInput.push_back(nfaStatep);
// Foreach epsilon-reachable (on this nfaStatep)
for (V3GraphEdge* nfaEdgep = nfaStatep->outBeginp();
nfaEdgep; nfaEdgep=nfaEdgep->outNextp()) {
DfaEdge* cNfaEdgep = static_cast<DfaEdge*>(nfaEdgep);
if (cNfaEdgep->epsilon()) {
DfaVertex* nextStatep = static_cast<DfaVertex*>(cNfaEdgep->top());
if (unseenNfaThisStep(nextStatep)) { // Not processed?
nfasTodo.push_back(nextStatep);
nextStatep->user(m_step);
UINFO(9," Epsilon Reachable "<<nextStatep<<endl);
}
}
}
}
}
}
void main() {
UINFO(5,"Dfa to Nfa conversion...\n");
// Vertex::color() begin: 1 indicates vertex on DFA graph, 0=NFA graph
m_graphp->clearColors();
// Vertex::m_user begin: # indicates processed this m_step number
m_graphp->userClearVertices();
if (debug()>=6) m_graphp->dumpDotFilePrefixed("dfa_nfa");
// Find NFA start
DfaVertex* nfaStartp = graphp()->findStart();
// Create new DFA State (start state) from the NFA states
DfaVertex* dfaStartp = newDfaVertex(nfaStartp);
DfaStates dfaUnprocps; // Unprocessed DFA nodes
dfaUnprocps.push_back(dfaStartp);
UINFO(5,"Starting state conversion...\n");
// Form DFA starting state from epsilon closure of NFA start
nextStep();
DfaStates workps; workps.push_back(nfaStartp);
while (!workps.empty()) { // While work
DfaVertex* nfaStatep = workps.back(); workps.pop_back();
//UINFO(9," Processing "<<nfaStatep<<endl);
nfaStatep->user(m_step); // Mark as processed
// Add a edge so we can find NFAs from a given DFA.
// The NFA will never see this edge, because we only look at TO edges.
new DfaEdge(graphp(), dfaStartp, nfaStatep, DfaEdge::NA());
// Find epsilon closure of this nfa node, and destinations to work list
for (V3GraphEdge* nfaEdgep = nfaStatep->outBeginp();
nfaEdgep; nfaEdgep=nfaEdgep->outNextp()) {
DfaEdge* cNfaEdgep = static_cast<DfaEdge*>(nfaEdgep);
DfaVertex* ecNfaStatep = static_cast<DfaVertex*>(nfaEdgep->top());
//UINFO(9," Consider "<<nfaEdgep->top()<<" EP "<<cNfaEdgep->epsilon()<<endl);
if (cNfaEdgep->epsilon()
&& unseenNfaThisStep(ecNfaStatep)) { // Not processed?
workps.push_back(ecNfaStatep);
}
}
}
if (debug()>=6) m_graphp->dumpDotFilePrefixed("dfa_start");
insertDfaOrigins(dfaStartp);
int i = 0;
UINFO(5,"Main state conversion...\n");
while (!dfaUnprocps.empty()) {
DfaVertex* dfaStatep = dfaUnprocps.back(); dfaUnprocps.pop_back();
UINFO(9," On dfaState "<<dfaStatep<<endl);
// From this dfaState, what corresponding nfaStates have what inputs?
std::set<int> inputs;
// Foreach NFA state (this DFA state was formed from)
for (V3GraphEdge* dfaEdgep = dfaStatep->outBeginp();
dfaEdgep; dfaEdgep=dfaEdgep->outNextp()) {
if (nfaState(dfaEdgep->top())) {
DfaVertex* nfaStatep = static_cast<DfaVertex*>(dfaEdgep->top());
// Foreach input on this nfaStatep
for (V3GraphEdge* nfaEdgep = nfaStatep->outBeginp();
nfaEdgep; nfaEdgep=nfaEdgep->outNextp()) {
DfaEdge* cNfaEdgep = static_cast<DfaEdge*>(nfaEdgep);
if (!cNfaEdgep->epsilon()) {
if (inputs.find(cNfaEdgep->input().toInt()) == inputs.end()) {
inputs.insert(cNfaEdgep->input().toInt());
UINFO(9," Input to "<<dfaStatep<<" is "
<<(cNfaEdgep->input().toInt())<<" via "<<nfaStatep<<endl);
}
}
}
}
}
// Foreach input state (NFA inputs of this DFA state)
for (std::set<int>::const_iterator inIt=inputs.begin(); inIt!=inputs.end(); ++inIt) {
DfaInput input = *inIt;
UINFO(9," ==="<<++i<<"=======================\n");
UINFO(9," On input "<<cvtToHex(input.toNodep())<<endl);
// Find all states reachable for given input
DfaStates nfasWithInput;
findNfasWithInput(dfaStatep, input, nfasWithInput/*ref*/);
// nfasWithInput now maps to the DFA we want a transition to.
// Does a DFA already exist with this, and only this subset of NFA's?
DfaVertex* toDfaStatep = findDfaOrigins(nfasWithInput);
if (!toDfaStatep) {
// Doesn't exist, make new dfa state corresponding to this one,
toDfaStatep = newDfaVertex();
dfaUnprocps.push_back(toDfaStatep); // Add to process list
// Track what nfa's point to it.
for (DfaStates::const_iterator nfaIt=nfasWithInput.begin();
nfaIt!=nfasWithInput.end(); ++nfaIt) {
UINFO(9," NewContainsNfa "<<*nfaIt<<endl);
new DfaEdge(graphp(), toDfaStatep, *nfaIt, DfaEdge::NA());
if ((*nfaIt)->accepting()) toDfaStatep->accepting(true);
}
insertDfaOrigins(toDfaStatep);
}
// Add input transition
new DfaEdge(graphp(), dfaStatep, toDfaStatep, input);
if (debug()>=6) m_graphp->dumpDotFilePrefixed("step");
}
}
// Remove old NFA states
UINFO(5,"Removing NFA states...\n");
if (debug()>=6) m_graphp->dumpDotFilePrefixed("dfa_withnfa");
for (V3GraphVertex* nextp,*vertexp = m_graphp->verticesBeginp(); vertexp; vertexp=nextp) {
nextp = vertexp->verticesNextp();
if (nfaState(vertexp)) {
vertexp->unlinkDelete(m_graphp); VL_DANGLING(vertexp);
}
}
UINFO(5,"Done.\n");
if (debug()>=6) m_graphp->dumpDotFilePrefixed("dfa_done");
}
public:
GraphNfaToDfa(V3Graph* graphp, V3EdgeFuncP edgeFuncp)
: GraphAlg<>(graphp, edgeFuncp) {
m_step = 0;
main();
}
~GraphNfaToDfa() {}
};
void DfaGraph::nfaToDfa() {
GraphNfaToDfa(this, &V3GraphEdge::followAlwaysTrue);
}
//######################################################################
//######################################################################
// Algorithms - optimize a DFA structure
//
// Scan the DFA, cleaning up trailing states.
class DfaGraphReduce : GraphAlg<> {
private:
// METHODS
#ifdef VL_CPPCHECK
static int debug() { return 9; }
#else
static int debug() { return 0; }
#endif
DfaGraph* graphp() { return static_cast<DfaGraph*>(m_graphp); }
bool isDead(DfaVertex* vertexp) {
// A state is dead if not accepting, and goes nowhere
if (vertexp->accepting() || vertexp->start()) return false;
for (V3GraphEdge* edgep = vertexp->outBeginp(); edgep; edgep=edgep->outNextp()) {
if (edgep->top() != vertexp) return false;
}
return true;
}
void optimize_accepting_out() {
// Delete outbound edges from accepting states
// (As once we've accepted, we no longer care about anything else.)
for (V3GraphVertex* vertexp = m_graphp->verticesBeginp();
vertexp; vertexp=vertexp->verticesNextp()) {
if (DfaVertex* vvertexp = dynamic_cast<DfaVertex*>(vertexp)) {
if (vvertexp->accepting()) {
for (V3GraphEdge* nextp,*edgep = vertexp->outBeginp(); edgep; edgep=nextp) {
nextp = edgep->outNextp();
edgep->unlinkDelete(); VL_DANGLING(edgep);
}
}
}
}
}
void optimize_orphans() {
// Remove states that don't come from start
// Presumably the previous optimization orphaned them.
// Vertex::m_user begin: 1 indicates on the work list, 2 processed
// (Otherwise we might have nodes on the list twice, and reference after deleting them.)
m_graphp->userClearVertices();
DfaVertex* startp = graphp()->findStart();
std::stack<V3GraphVertex*> workps; workps.push(startp);
// Mark all nodes connected to start
while (!workps.empty()) {
V3GraphVertex* vertexp = workps.top(); workps.pop();
vertexp->user(2); // Processed
// Add nodes from here to the work list
for (V3GraphEdge* edgep = vertexp->outBeginp(); edgep; edgep=edgep->outNextp()) {
V3GraphVertex* tovertexp = edgep->top();
if (!tovertexp->user()) {
workps.push(tovertexp);
tovertexp->user(1);
}
}
}
// Delete all nodes not connected
for (V3GraphVertex* nextp,*vertexp = m_graphp->verticesBeginp(); vertexp; vertexp=nextp) {
nextp = vertexp->verticesNextp();
if (!vertexp->user()) {
vertexp->unlinkDelete(m_graphp); VL_DANGLING(vertexp);
}
}
}
void optimize_no_outbound() {
// Non-accepting states with no outbound transitions may be
// deleted. Then, any arcs feeding those states, and perhaps those
// states...
// Vertex::m_user begin: 1 indicates on the work list
// (Otherwise we might have nodes on the list twice, and reference after deleting them.)
m_graphp->userClearVertices();
// Find all dead vertexes
std::stack<DfaVertex*> workps;
for (V3GraphVertex* vertexp = m_graphp->verticesBeginp();
vertexp; vertexp=vertexp->verticesNextp()) {
if (DfaVertex* vvertexp = dynamic_cast<DfaVertex*>(vertexp)) {
workps.push(vvertexp);
vertexp->user(1);
} else {
// If ever remove this, need dyn cast below
vertexp->v3fatalSrc("Non DfaVertex in dfa graph");
}
}
// While deadness... Delete and find new dead nodes.
while (!workps.empty()) {
DfaVertex* vertexp = workps.top(); workps.pop();
vertexp->user(0);
if (isDead(vertexp)) {
// Add nodes that go here to the work list
for (V3GraphEdge* edgep = vertexp->inBeginp(); edgep; edgep=edgep->inNextp()) {
DfaVertex* fromvertexp = static_cast<DfaVertex*>(edgep->fromp());
if (fromvertexp != vertexp
&& !fromvertexp->user()) {
workps.push(fromvertexp);
fromvertexp->user(1);
}
}
// Transitions to this state removed by the unlink function
vertexp->unlinkDelete(m_graphp); VL_DANGLING(vertexp);
}
}
}
public:
DfaGraphReduce(V3Graph* graphp, V3EdgeFuncP edgeFuncp)
: GraphAlg<>(graphp, edgeFuncp) {
if (debug()>=6) m_graphp->dumpDotFilePrefixed("opt_in");
optimize_accepting_out();
if (debug()>=6) m_graphp->dumpDotFilePrefixed("opt_acc");
optimize_orphans();
if (debug()>=6) m_graphp->dumpDotFilePrefixed("opt_orph");
optimize_no_outbound();
if (debug()>=6) m_graphp->dumpDotFilePrefixed("opt_noout");
}
~DfaGraphReduce() {}
};
void DfaGraph::dfaReduce() {
DfaGraphReduce(this, &V3GraphEdge::followAlwaysTrue);
}
//######################################################################
//######################################################################
// Algorithms - complement a DFA
//
// The traditional algorithm is to make a rejecting state, add edges to
// reject from all missing values, then swap accept and reject. Rather
// than swap at the end, it's faster if we swap up front, then do the edge
// changes.
//
// 1. Since we didn't log rejecting states, make a temp state (this will be
// the old accept, and new reject).
//
// 2. All vertexes except start/accept get edges to NEW accept for any
// non-existing case. Weedely we don't have a nice way of representing
// this so we just create a edge for each case and mark it "complemented."
//
// 3. Delete temp vertex (old accept/new reject) and related edges.
// The user's old accept is now the new accept. This is important as
// we want the virtual type of it to be intact.
class DfaGraphComplement : GraphAlg<> {
private:
// MEMBERS
DfaVertex* m_tempNewerReject;
// METHODS
static int debug() { return 9; }
DfaGraph* graphp() { return static_cast<DfaGraph*>(m_graphp); }
void add_complement_edges() {
// Find accepting vertex
DfaVertex* acceptp = NULL;
for (V3GraphVertex* vertexp = m_graphp->verticesBeginp();
vertexp; vertexp=vertexp->verticesNextp()) {
if (DfaVertex* vvertexp = dynamic_cast<DfaVertex*>(vertexp)) {
if (vvertexp->accepting()) {
acceptp = vvertexp;
break;
}
}
}
if (!acceptp) v3fatalSrc("No accepting vertex in DFA");
// Remap edges
for (V3GraphVertex* vertexp = m_graphp->verticesBeginp();
vertexp; vertexp=vertexp->verticesNextp()) {
if (DfaVertex* vvertexp = dynamic_cast<DfaVertex*>(vertexp)) {
//UINFO(9, " on vertex "<<vvertexp->name()<<endl);
if (!vvertexp->accepting() && vvertexp != m_tempNewerReject) {
for (V3GraphEdge* nextp, *edgep = vertexp->outBeginp(); edgep; edgep=nextp) {
nextp = edgep->outNextp();
if (!edgep->user()) { // Not processed
// Old edges to accept now go to new reject
DfaEdge* vedgep = static_cast<DfaEdge*>(edgep);
DfaVertex* tovertexp = static_cast<DfaVertex*>(edgep->top());
if (tovertexp->accepting()) {
new DfaEdge(graphp(), vvertexp, m_tempNewerReject, vedgep);
edgep->unlinkDelete(); VL_DANGLING(edgep);
}
// NOT of all values goes to accept
// We make a edge for each value to OR, IE
// edge(complemented,a) edge(complemented,b) means !(a | b)
if (!tovertexp->accepting()) { // Note we must include edges moved above to reject
DfaEdge* newp = new DfaEdge(graphp(), vvertexp, acceptp, vedgep);
newp->complement(!newp->complement());
newp->user(1);
}
}
}
}
}
}
}
public:
DfaGraphComplement(V3Graph* dfagraphp, V3EdgeFuncP edgeFuncp)
: GraphAlg<>(dfagraphp, edgeFuncp) {
if (debug()>=6) m_graphp->dumpDotFilePrefixed("comp_in");
// Vertex::m_user begin: 1 indicates new edge, no more processing
m_graphp->userClearEdges();
m_tempNewerReject = new DfaVertex(graphp());
add_complement_edges();
if (debug()>=6) m_graphp->dumpDotFilePrefixed("comp_preswap");
m_tempNewerReject->unlinkDelete(graphp()); m_tempNewerReject = NULL;
if (debug()>=6) m_graphp->dumpDotFilePrefixed("comp_out");
}
~DfaGraphComplement() {}
};
void DfaGraph::dfaComplement() {
DfaGraphComplement(this, &V3GraphEdge::followAlwaysTrue);
}
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