mirror of
https://github.com/verilator/verilator.git
synced 2025-01-22 14:24:18 +00:00
232 lines
7.5 KiB
C++
232 lines
7.5 KiB
C++
//*************************************************************************
|
||
// DESCRIPTION: Verilator: Dead code elimination
|
||
//
|
||
// Code available from: http://www.veripool.org/verilator
|
||
//
|
||
// AUTHORS: Wilson Snyder with Paul Wasson, Duane Gabli
|
||
//
|
||
//*************************************************************************
|
||
//
|
||
// Copyright 2003-2011 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.
|
||
//
|
||
//*************************************************************************
|
||
// DEAD TRANSFORMATIONS:
|
||
// Remove any unreferenced modules
|
||
// Remove any unreferenced variables
|
||
//
|
||
// NOTE: If redo this, consider using maybePointedTo()/broken() ish scheme
|
||
// instead of needing as many visitors.
|
||
//*************************************************************************
|
||
|
||
#include "config_build.h"
|
||
#include "verilatedos.h"
|
||
#include <cstdio>
|
||
#include <cstdarg>
|
||
#include <unistd.h>
|
||
#include <vector>
|
||
#include <map>
|
||
|
||
#include "V3Global.h"
|
||
#include "V3Dead.h"
|
||
#include "V3Ast.h"
|
||
|
||
//######################################################################
|
||
|
||
class DeadModVisitor : public AstNVisitor {
|
||
// In a module that is dead, cleanup the in-use counts of the modules
|
||
private:
|
||
// NODE STATE
|
||
// ** Shared with DeadVisitor **
|
||
// VISITORS
|
||
virtual void visit(AstCell* nodep, AstNUser*) {
|
||
nodep->iterateChildren(*this);
|
||
nodep->modp()->user1(nodep->modp()->user1() - 1);
|
||
}
|
||
//-----
|
||
virtual void visit(AstNodeMath* nodep, AstNUser*) {} // Accelerate
|
||
virtual void visit(AstNode* nodep, AstNUser*) {
|
||
nodep->iterateChildren(*this);
|
||
}
|
||
public:
|
||
// CONSTRUCTORS
|
||
DeadModVisitor(AstNodeModule* nodep) {
|
||
nodep->accept(*this);
|
||
}
|
||
virtual ~DeadModVisitor() {}
|
||
};
|
||
|
||
//######################################################################
|
||
// Dead state, as a visitor of each AstNode
|
||
|
||
class DeadVisitor : public AstNVisitor {
|
||
private:
|
||
// NODE STATE
|
||
// Entire Netlist:
|
||
// AstNodeModule::user() -> int. Count of number of cells referencing this module.
|
||
// AstVar::user() -> int. Count of number of references
|
||
// AstVarScope::user() -> int. Count of number of references
|
||
AstUser1InUse m_inuser1;
|
||
|
||
// TYPES
|
||
typedef multimap<AstVarScope*,AstNodeAssign*> AssignMap;
|
||
|
||
// STATE
|
||
vector<AstVar*> m_varsp; // List of all encountered to avoid another loop through tree
|
||
vector<AstVarScope*> m_vscsp; // List of all encountered to avoid another loop through tree
|
||
AssignMap m_assignMap; // List of all simple assignments for each variable
|
||
bool m_elimUserVars; // Allow removal of user's vars
|
||
bool m_sideEffect; // Side effects discovered in assign RHS
|
||
|
||
// METHODS
|
||
static int debug() {
|
||
static int level = -1;
|
||
if (VL_UNLIKELY(level < 0)) level = v3Global.opt.debugSrcLevel(__FILE__);
|
||
return level;
|
||
}
|
||
|
||
// VISITORS
|
||
virtual void visit(AstCell* nodep, AstNUser*) {
|
||
nodep->iterateChildren(*this);
|
||
nodep->modp()->user1Inc();
|
||
}
|
||
virtual void visit(AstNodeVarRef* nodep, AstNUser*) {
|
||
nodep->iterateChildren(*this);
|
||
if (nodep->varScopep()) {
|
||
nodep->varScopep()->user1Inc();
|
||
nodep->varScopep()->varp()->user1Inc();
|
||
}
|
||
if (nodep->varp()) {
|
||
nodep->varp()->user1Inc();
|
||
}
|
||
if (nodep->packagep()) {
|
||
nodep->packagep()->user1Inc();
|
||
}
|
||
}
|
||
virtual void visit(AstNodeFTaskRef* nodep, AstNUser*) {
|
||
nodep->iterateChildren(*this);
|
||
if (nodep->packagep()) {
|
||
nodep->packagep()->user1Inc();
|
||
}
|
||
}
|
||
virtual void visit(AstRefDType* nodep, AstNUser*) {
|
||
nodep->iterateChildren(*this);
|
||
if (nodep->packagep()) {
|
||
nodep->packagep()->user1Inc();
|
||
}
|
||
}
|
||
virtual void visit(AstEnumItemRef* nodep, AstNUser*) {
|
||
nodep->iterateChildren(*this);
|
||
if (nodep->packagep()) {
|
||
nodep->packagep()->user1Inc();
|
||
}
|
||
}
|
||
virtual void visit(AstVarScope* nodep, AstNUser*) {
|
||
nodep->iterateChildren(*this);
|
||
m_vscsp.push_back(nodep);
|
||
}
|
||
virtual void visit(AstVar* nodep, AstNUser*) {
|
||
nodep->iterateChildren(*this);
|
||
m_varsp.push_back(nodep);
|
||
}
|
||
|
||
virtual void visit(AstNodeAssign* nodep, AstNUser*) {
|
||
// See if simple assignments to variables may be eliminated because that variable is never used.
|
||
// Similar code in V3Life
|
||
m_sideEffect = false;
|
||
nodep->rhsp()->iterateAndNext(*this);
|
||
// Has to be direct assignment without any EXTRACTing.
|
||
AstVarRef* varrefp = nodep->lhsp()->castVarRef();
|
||
if (varrefp && !m_sideEffect
|
||
&& varrefp->varScopep()) { // For simplicity, we only remove post-scoping
|
||
m_assignMap.insert(make_pair(varrefp->varScopep(), nodep));
|
||
} else { // Track like any other statement
|
||
nodep->lhsp()->iterateAndNext(*this);
|
||
}
|
||
}
|
||
|
||
//-----
|
||
virtual void visit(AstNode* nodep, AstNUser*) {
|
||
if (nodep->isOutputter()) m_sideEffect=true;
|
||
nodep->iterateChildren(*this);
|
||
}
|
||
|
||
// METHODS
|
||
void deadCheckMod() {
|
||
// Kill any unused modules
|
||
// V3LinkCells has a graph that is capable of this too, but we need to do it
|
||
// after we've done all the generate blocks
|
||
for (bool retry=true; retry; ) {
|
||
retry=false;
|
||
AstNodeModule* nextmodp;
|
||
for (AstNodeModule* modp = v3Global.rootp()->modulesp(); modp; modp=nextmodp) {
|
||
nextmodp = modp->nextp()->castNodeModule();
|
||
if (modp->level()>2 && modp->user1()==0) {
|
||
// > 2 because L1 is the wrapper, L2 is the top user module
|
||
UINFO(4," Dead module "<<modp<<endl);
|
||
// And its children may now be killable too; correct counts
|
||
// Recurse, as cells may not be directly under the module but in a generate
|
||
DeadModVisitor visitor(modp);
|
||
modp->unlinkFrBack()->deleteTree(); modp=NULL;
|
||
retry = true;
|
||
}
|
||
}
|
||
}
|
||
}
|
||
bool canElim(AstVar* nodep) {
|
||
return (!nodep->isSigPublic() // Can't elim publics!
|
||
&& !nodep->isIO()
|
||
&& (nodep->isTemp() || nodep->isParam() || m_elimUserVars));
|
||
}
|
||
void deadCheckVar() {
|
||
// Delete any unused varscopes
|
||
for (vector<AstVarScope*>::iterator it = m_vscsp.begin(); it!=m_vscsp.end(); ++it) {
|
||
AstVarScope* vscp = *it;
|
||
if (vscp->user1() == 0 && canElim(vscp->varp())) {
|
||
UINFO(4," Dead "<<vscp<<endl);
|
||
pair <AssignMap::iterator,AssignMap::iterator> eqrange = m_assignMap.equal_range(vscp);
|
||
for (AssignMap::iterator it = eqrange.first; it != eqrange.second; ++it) {
|
||
AstNodeAssign* assp = it->second;
|
||
UINFO(4," Dead assign "<<assp<<endl);
|
||
assp->unlinkFrBack()->deleteTree(); assp=NULL;
|
||
}
|
||
vscp->unlinkFrBack()->deleteTree(); vscp=NULL;
|
||
}
|
||
}
|
||
for (vector<AstVar*>::iterator it = m_varsp.begin(); it!=m_varsp.end(); ++it) {
|
||
if ((*it)->user1() == 0 && canElim((*it))) {
|
||
UINFO(4," Dead "<<(*it)<<endl);
|
||
(*it)->unlinkFrBack()->deleteTree(); (*it)=NULL;
|
||
}
|
||
}
|
||
}
|
||
|
||
public:
|
||
// CONSTRUCTORS
|
||
DeadVisitor(AstNetlist* nodep, bool elimUserVars) {
|
||
m_elimUserVars = elimUserVars;
|
||
m_sideEffect = false;
|
||
// Operate on whole netlist
|
||
nodep->accept(*this);
|
||
deadCheckVar();
|
||
// Modules after vars, because might be vars we delete inside a mod we delete
|
||
deadCheckMod();
|
||
}
|
||
virtual ~DeadVisitor() {}
|
||
};
|
||
|
||
//######################################################################
|
||
// Dead class functions
|
||
|
||
void V3Dead::deadifyAll(AstNetlist* nodep, bool elimUserVars) {
|
||
UINFO(2,__FUNCTION__<<": "<<endl);
|
||
DeadVisitor visitor (nodep, elimUserVars);
|
||
}
|