Esempio n. 1
0
    virtual void visit(AstPin* nodep, AstNUser*) {
	// Check to see if any output pins have __en pins and create the __en pins to match
	AstVarRef* refp = findVarRef(nodep);

	if (refp && refp->lvalue() && nodep->modVarp()->user1p()) {
	    AstVar* enchildp = (AstVar*)nodep->modVarp()->user1p();
	    UINFO(9, "       Pulling __en var" << enchildp << endl);
	    AstVar* enp = new AstVar(enchildp->fileline(),
				     AstVarType::OUTPUT,
				     enchildp->name()+cvtToStr(m_unique++),
				     enchildp);
	    enp->user2(enchildp->user2());
	    m_modp->addStmtp(enp);
	    AstPin* pinp = new AstPin(nodep->fileline(),
				      nodep->pinNum(),
				      enp->name(),
				      new AstVarRef(nodep->fileline(), enp, true));
	    AstVarRef *rp = findVarRef(pinp);
	    rp->replaceWith(new AstVarRef(nodep->fileline(), enp, true));
	    rp->deleteTree(); rp=NULL;
	    pinp->width(enp->width(),enp->width());  // minwidth==width
	    pinp->modVarp(enchildp);
	    m_cellp->addPinsp(pinp);
	    refp->user1p(enp);
	    refp->varp()->user1p(enp);
	}
	// Simplify interconnect in preperation for V3Inst
	// (This could be a separate visitor, but we're in the neighborhood)
	V3Inst::pinReconnectSimple(nodep, m_cellp, m_modp);
    }
Esempio n. 2
0
    //*******************************************************************
    // The following visitor functions deal with detecting Z's in the
    // logic, stripping the Z's out and creating an __en signal and its
    // logic.
    //*******************************************************************
    virtual void visit(AstPull* nodep, AstNUser*) {
        // replace any pullup/pulldowns with assignw logic and an __en
        // signal just like it is any other tristate signal.  The only
        // difference is that the user2() variable on the __en signal
        // will be given a pull direction--i.e. pulldown=1, pullup=2.
        // This will signal the driver exansion logic to put a default
        // pullup or pulldown state on the tristate bus under the high-Z
        // condition when no one is driving the bus.  Given the complexity
        // of merging tristate drivers at any level, the current limitation
        // of this implementation is that a pullup/down gets applied
        // to all bits of a bus and a bus cannot have drivers in opposite
        // directions on indvidual pins.
        AstNode* outp = nodep->lhsp()->unlinkFrBack();;
        AstVarRef* outrefp = NULL;
	int width=-1;
	if (outp->castVarRef()) {
	    outrefp = outp->castVarRef();
	} else if (outp->castSel()) {
	    outrefp = outp->castSel()->fromp()->castVarRef();
	    width = outp->castSel()->widthConst();
	} else {
	    nodep->v3error("Can't find LHS varref");
	}
	outrefp->lvalue(true);
	AstVar* varp = outrefp->varp();
	if (width==-1) width=varp->width();

        V3Number num0 (nodep->fileline(), width);
	num0.setAllBits0();
	V3Number num1 (nodep->fileline(), width);
	num1.setAllBits1();

	AstConst* enrhsp = new AstConst(nodep->fileline(), num0);
	AstVar* enp = createEnableVar(outp, outrefp, enrhsp, width, "pull");
	enp->user2(nodep->direction()+1); // record the pull direction

	AstAssignW* newassp = new AstAssignW(nodep->fileline(), outp,
					     new AstConst(nodep->fileline(), nodep->direction() ? num1 : num0));
	nodep->replaceWith(newassp);
	nodep->deleteTree(); nodep=NULL;
	newassp->iterateChildren(*this);
    }
Esempio n. 3
0
    virtual void visit(AstNodeModule* nodep, AstNUser*) {
	UINFO(9," MOD   "<<nodep<<endl);
	m_unique = 0;
	VarMap* lhsmapp = new VarMap();

	// expand tristate nodes and detect multiple LHS drivers for this module
	TristateExpander(nodep, lhsmapp);

	// iterate the children to grab any  __en signals from subcells
	m_modp = nodep;
	nodep->iterateChildren(*this);
	m_modp = NULL;

	// go through each multiple lhs driver & collapse it to a single driver
	for (VarMap::iterator nextit, it=lhsmapp->begin(); it != lhsmapp->end(); it=nextit) {
	    nextit = it; ++nextit;
	    m_unique = 0;
	    AstVar* lhsp = (*it).first;
	    RefVec* refs = (*it).second;
	    bool isOutput = (lhsp->varType() == AstVarType::OUTPUT) && (nodep->level() > 1); // force termination at top level

	    if (refs->size() < 2 && isOutput) {
		// if only one driver and this is an output, then exit and
		// let the driver propagate on its own.  If the signals
		// terminates at this level, then we need to let the
		// undriven state get generated.
		lhsmapp->erase(lhsp);
		delete refs;
		continue;
	    }


	    UINFO(9, "       Checking " << refs->size() << " drivers for tristates signals on net " << lhsp << endl);
	    int pull = 0;  // initially assume no pull direction

	    // Now remove and multple lhs signals that do not have __en for
	    // all possible drivers.
	    bool complete = true;
	    int found_one = 0;

	    for (RefVec::iterator ii=refs->begin(); ii != refs->end(); ++ii) {
		AstVarRef* refp = (*ii);
		if (!refp->user1p()) { // if no __en signal, then delete the entry
		    complete = false;
		} else {
		    found_one++;
		}
	    }
	    if (!complete) {
		if (found_one) {
		    UINFO(9, "       Problem mixing tristate and low-Z on " << lhsp << endl);
		    UINFO(9, "       Found " << found_one << " __en signals from of " << refs->size() << " possible drivers" << endl);
		    // not sure what I should do here other than error that they are mixing low-Z and tristate drivers.
		    // The other scenerio, and probably more likely, is that they are using a high-Z construct that
		    // is not supported.  Improving the high-Z detection logic will reduce the occurance of this failure.
		    nodep->v3error("Mixing tristate and low-Z drivers.  Perhaps you are using a high-Z construct not supported");
		} else  {
		    UINFO(9, "       No tristates found on " << lhsp <<endl);
		}
		lhsmapp->erase(lhsp);
		delete refs;
		continue;
	    }

	    UINFO(9, "       TRISTATE LHS DRIVER FOUND:" << lhsp << endl);

	    AstNode* orp = NULL,* andp = NULL,* undrivenp = NULL,* newenlogicp = NULL;

	    // loop through the lhs drivers to build the driver resolution logic
	    for (RefVec::iterator ii=refs->begin(); ii != refs->end(); ++ii) {
		AstVarRef* refp = (*ii);
		int w = lhsp->width();
		int wfill = 0; // width filler when necessary due to sels
		AstSel* selp = NULL;
		if (refp->user3p()) { // this varref has a sel
		    selp = (AstSel*) refp->user3p();
		    w = selp->widthConst();
		    wfill = lhsp->width() - w;
		}

		// create a new var for this assignment.
		AstVar* enp = (AstVar*)refp->user1p();
		AstVar* newlhsp = new AstVar(lhsp->fileline(),
					     AstVarType::MODULETEMP,
					     lhsp->name()+"__lhs"+cvtToStr(m_unique++),
					     AstLogicPacked(), w);
		nodep->addStmtp(newlhsp);

		// now append this driver to the driver logic.
		AstNode* ref1 = new AstVarRef(nodep->fileline(), newlhsp,false);
		AstNode* ref2 = new AstVarRef(nodep->fileline(), enp, false);
		andp = new AstAnd(nodep->fileline(), ref1, ref2);


		AstVar* bitselp = NULL;
		if (selp) { // this varref has a sel
		    int ws = V3Number::log2b(lhsp->width())+1;
		    bitselp = new AstVar(lhsp->fileline(),
					 AstVarType::MODULETEMP,
					 lhsp->name()+"__sel"+cvtToStr(m_unique-1),
					 AstLogicPacked(), ws);
		    //
		    nodep->addStmtp(bitselp);
		    nodep->addStmtp(new AstAssignW(lhsp->fileline(),
						   new AstVarRef(lhsp->fileline(), bitselp, true),
						   selp->lsbp()->cloneTree(false)));
		    andp = new AstShiftL(lhsp->fileline(),
					 new AstConcat(lhsp->fileline(), new AstConst(lhsp->fileline(), V3Number(lhsp->fileline(), wfill, 0)), andp),
					 new AstVarRef(lhsp->fileline(), bitselp, false),
					 lhsp->width()
			);

		    selp->replaceWith(new AstVarRef(refp->fileline(), newlhsp, true));
		    pushDeletep(selp);  // Setting selp here or deleting immediately
		    // breaks the t_tri_select test, this probably indicates a problem
		} else {
		    refp->varp(newlhsp); // assign the new var to the varref
		    refp->name(newlhsp->name());
		}

		// or this to the others
		orp = (!orp) ? andp : new AstOr(nodep->fileline(), orp, andp);

		if (isOutput) {
		    AstNode *en1p = new AstVarRef(nodep->fileline(), enp, false);
		    if (selp) {
			en1p = new AstShiftL(enp->fileline(),
					     new AstConcat(lhsp->fileline(), new AstConst(lhsp->fileline(), V3Number(lhsp->fileline(), wfill, 0)), en1p),
					     new AstVarRef(lhsp->fileline(), bitselp, false),
					     lhsp->width()
			    );
		    }
		    if (!newenlogicp) {
			newenlogicp = en1p;
		    } else {
			newenlogicp = new AstOr(nodep->fileline(), newenlogicp, en1p);
		    }
		} else {
		    if (!undrivenp) {
			undrivenp = new AstNot(nodep->fileline(), new AstVarRef(nodep->fileline(), enp, false));
			if (selp)
			    undrivenp = new AstShiftL(enp->fileline(),
						      new AstConcat(lhsp->fileline(), new AstConst(lhsp->fileline(), V3Number(lhsp->fileline(), wfill, 0)), undrivenp),
						      new AstVarRef(lhsp->fileline(), bitselp, false),
						      lhsp->width());
		    } else {
			AstNode *tmp = new AstNot(nodep->fileline(), new AstVarRef(nodep->fileline(), enp, false));
			if (selp) {
			    tmp = new AstShiftL(enp->fileline(),
						new AstConcat(lhsp->fileline(), new AstConst(lhsp->fileline(), V3Number(lhsp->fileline(), wfill, 0)), tmp),
						new AstVarRef(lhsp->fileline(), bitselp, false),
						lhsp->width());
			}
			undrivenp = new AstAnd(nodep->fileline(), tmp, undrivenp);
		    }
		}

		refp->user1p(NULL); // clear the user1p() as we done with it in the VarRef at this point

		if (enp->user2()) { // if this net is pulled up/down
		    int newpull = enp->user2();
		    if (pull == 0) {
			pull = newpull;
		    } else if (newpull != pull) {
			pull = -1; // conflict over the pull direction
		    }
		}
	    }
	    if (isOutput) {
		AstVar* newenp = new AstVar(lhsp->fileline(),
					    AstVarType::OUTPUT,
					    lhsp->name()+"__enout"+cvtToStr(m_unique++),
					    lhsp);
		nodep->addStmtp(newenp);
		nodep->addStmtp(new AstAssignW(lhsp->fileline(),
					       new AstVarRef(lhsp->fileline(), newenp, true),
					       newenlogicp));
		newenp->user2(pull); // put the pull direction in the next __en signal to pass it up
		lhsp->user1p(newenp); // put the new __en signal in the var so it can be pushed up the hierarchy.

	    } else { // this is the level where the signal terminates, we do final conflict resolution here
		UINFO(9, "       Terminating tristate logic for " << lhsp->name() << endl);
		UINFO(9, "       Pull direction is " << pull << " where -1=X, 0=Z, 1=low, 2=high." << endl);
		// figure out what to drive when no one is driving the bus
		V3Number num(nodep->fileline(), lhsp->width());
		if (pull==0) {
		    num.setAllBitsZ();
		} else if (pull==1) {
		    num.setAllBits0();
		} else if (pull==2) {
		    num.setAllBits1();
		} else {
		    num.setAllBitsX();
		}
		undrivenp = new AstAnd(nodep->fileline(), undrivenp,
				       new AstConst(nodep->fileline(), num));
		orp = new AstOr(nodep->fileline(), orp, undrivenp);
	    }
	    nodep->addStmtp(new AstAssignW(lhsp->fileline(),
					   new AstVarRef(lhsp->fileline(), lhsp, true), orp));

	    // delete the map and vector list now that we have collapsed it.
	    lhsmapp->erase(lhsp);
	    delete refs;
	}
	delete lhsmapp; // delete the map now that we are done
	nodep->user1p(NULL);
    }