C++ AstConst::isZero方法代码示例

    bool forUnrollCheck(AstNode* nodep,
			AstNode* initp,	// Maybe under nodep (no nextp), or standalone (ignore nextp)
			AstNode* precondsp, AstNode* condp,
			AstNode* incp,		// Maybe under nodep or in bodysp
			AstNode* bodysp) {
	// To keep the IF levels low, we return as each test fails.
	UINFO(4, " FOR Check "<<nodep<<endl);
	if (initp)	UINFO(6, "    Init "<<initp<<endl);
	if (precondsp)	UINFO(6, "    Pcon "<<precondsp<<endl);
	if (condp)	UINFO(6, "    Cond "<<condp<<endl);
	if (incp)	UINFO(6, "    Inc  "<<incp<<endl);
	// Initial value check
	AstAssign* initAssp = initp->castAssign();
	if (!initAssp) return cantUnroll(nodep, "no initial assignment");
	if (initp->nextp() && initp->nextp()!=nodep) nodep->v3fatalSrc("initial assignment shouldn't be a list");
	if (!initAssp->lhsp()->castVarRef()) return cantUnroll(nodep, "no initial assignment to simple variable");
	m_forVarp = initAssp->lhsp()->castVarRef()->varp();
	m_forVscp = initAssp->lhsp()->castVarRef()->varScopep();
	if (nodep->castGenFor() && !m_forVarp->isGenVar()) {
	    nodep->v3error("Non-genvar used in generate for: "<<m_forVarp->name()<<endl);
	}
	if (m_generate) V3Const::constifyParamsEdit(initAssp->rhsp());  // rhsp may change
	AstConst* constInitp = initAssp->rhsp()->castConst();
	if (!constInitp) return cantUnroll(nodep, "non-constant initializer");
	//
	// Condition check
	if (condp->nextp()) nodep->v3fatalSrc("conditional shouldn't be a list");
	//
	// Assignment of next value check
	AstAssign* incAssp = incp->castAssign();
	if (!incAssp) return cantUnroll(nodep, "no increment assignment");
	if (incAssp->nextp()) nodep->v3fatalSrc("increment shouldn't be a list");
	AstNodeBiop* incInstrp = incAssp->rhsp()->castNodeBiop();
	//
	if (m_forVscp) { UINFO(8, "   Loop Variable: "<<m_forVscp<<endl); }
	else	       { UINFO(8, "   Loop Variable: "<<m_forVarp<<endl); }
	if (debug()>=9) nodep->dumpTree(cout,"-   for: ");
	//
	// Extract the constant loop bounds
	bool subtract = incInstrp->castSub();
	{
	    if (!subtract && !incInstrp->castAdd()) return cantUnroll(nodep, "missing add/sub for incrementer");
	    AstVarRef* incVarrp   = (subtract ? incInstrp->lhsp()->castVarRef()
				     : incInstrp->rhsp()->castVarRef());
	    if (!incVarrp) return cantUnroll(nodep, "missing variable in incrementer");
	    if (incVarrp->varp() != m_forVarp
		|| incVarrp->varScopep() != m_forVscp) {
		return cantUnroll(nodep, "different variables in incrementer");
	    }
	}
	//
	// Adds have the # on the lhsp because V3Const pushes rhs consts over to the lhs
	// Subtracts have it on the rhs, because you write i=i-1; i=1-i is non-sensible.
	AstConst* preconstIncp = (subtract ? incInstrp->rhsp()->castConst()
				  : incInstrp->lhsp()->castConst());
	if (m_generate) preconstIncp = V3Const::constifyParamsEdit(preconstIncp)->castConst();
	AstConst* constIncp = (subtract ? incInstrp->rhsp()->castConst()
			       : incInstrp->lhsp()->castConst());
	UINFO(8, "   Inc expr ok:  "<<constIncp<<endl);
	if (!constIncp) return cantUnroll(nodep, "non-constant increment");
	if (constIncp->isZero()) return cantUnroll(nodep, "zero increment");  // Or we could loop forever below...

        bool lt  = condp->castLt() || condp->castLtS();
        bool lte = condp->castLte() || condp->castLteS();
	bool gt  = condp->castGt() || condp->castGtS();
	bool gte = condp->castGte() || condp->castGteS();
	if (!lt && !lte && !gt && !gte)
	    return cantUnroll(nodep, "condition not <= or <");
	AstNodeBiop* condBip = condp->castNodeBiop();
	if (!condBip->lhsp()->castVarRef())
	    return cantUnroll(nodep, "no variable on lhs of condition");
	if (condBip->lhsp()->castVarRef()->varp() != m_forVarp
	    || condBip->lhsp()->castVarRef()->varScopep() != m_forVscp)
	    return cantUnroll(nodep, "different variable in condition");
	if (m_generate) V3Const::constifyParamsEdit(condBip->rhsp());  // rhsp may change
	AstConst* constStopp = condBip->rhsp()->castConst();
	if (!constStopp) return cantUnroll(nodep, "non-constant final value");
	UINFO(8, "   Stop expr ok: "<<constStopp<<endl);
	//
	if (constInitp->width()>32 || constInitp->num().isFourState()
	    || constStopp->width()>32 || constStopp->num().isFourState()
	    || constIncp->width()>32  || constIncp->num().isFourState())
	    return cantUnroll(nodep, "init/final/increment too large or four state");
	vlsint32_t valInit = constInitp->num().toSInt();
	vlsint32_t valStop = constStopp->num().toSInt();
	if (lte) valStop++;  if (gte) valStop--;
	vlsint32_t valInc  = constIncp->num().toSInt();
	if (subtract) valInc = -valInc;
	UINFO(8,"     In Numbers: for (v="<<valInit<<"; v<"<<valStop<<"; v=v+"<<valInc<<")\n");
	//
	if (!m_generate) {
	    int loops = ((valStop - valInit)/valInc);
	    if (loops < 0) { loops += (1ULL<<constStopp->width()); } // Will roll around
	    UINFO(8, "         ~Iters: "<<loops<<" c="<<unrollCount()<<endl);
	    if (loops > unrollCount())
		return cantUnroll(nodep, "too many iterations");

	    // Less than 10 statements in the body?
	    int bodySize = 0;
	    int bodyLimit = v3Global.opt.unrollStmts();
//.........这里部分代码省略.........