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);
}
//*******************************************************************
// 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);
}
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);
}
