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Internals: Tristate join AND/OR visitor pull setter. No functional change

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This commit is contained in:
Wilson Snyder 2012-05-05 15:04:33 -04:00
parent 86af244636
commit d55f065ce2
1 changed files with 46 additions and 57 deletions
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103
src/V3Tristate.cpp
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@ -506,68 +506,57 @@ class TristateVisitor : public TristateBaseVisitor {
pushDeletep(nodep); nodep = NULL;
}
virtual void visit(AstAnd* nodep, AstNUser*) {
void visitAndOr(AstNodeBiop* nodep, bool isAnd) {
nodep->iterateChildren(*this);
UINFO(9,(m_alhs?"alhs":"")<<" "<<nodep<<endl);
if (m_alhs && nodep->user1p()) { nodep->v3error("Unsupported LHS tristate construct: "<<nodep->prettyTypeName()); return; }
// ANDs and Z's have issues. Earlier optimizations convert
// expressions like "(COND) ? 1'bz : 1'b0" to "COND & 1'bz". So we
// have to define what is means to AND 1'bz with other
// expressions. I don't think this is spec, but here I take the
// approach that when one expression is 1, that the Z passes. This
// makes the COND's work. It is probably better to not perform the
// conditional optimization if the bits are Z.
AstNode* expr1p = nodep->lhsp();
AstNode* expr2p = nodep->rhsp();
if (!expr1p->user1p() && !expr2p->user1p()) {
return; // no tristates in either expression, so nothing to do
{
if (m_alhs && nodep->user1p()) { nodep->v3error("Unsupported LHS tristate construct: "<<nodep->prettyTypeName()); return; }
// ANDs and Z's have issues. Earlier optimizations convert
// expressions like "(COND) ? 1'bz : 1'b0" to "COND & 1'bz". So we
// have to define what is means to AND 1'bz with other
// expressions. I don't think this is spec, but here I take the
// approach that when one expression is 1, that the Z passes. This
// makes the COND's work. It is probably better to not perform the
// conditional optimization if the bits are Z.
//
// ORs have the same issues as ANDs. Earlier optimizations convert
// expressions like "(COND) ? 1'bz : 1'b1" to "COND | 1'bz". So we
// have to define what is means to OR 1'bz with other
// expressions. Here I take the approach that when one expression
// is 0, that is passes the other.
AstNode* expr1p = nodep->lhsp();
AstNode* expr2p = nodep->rhsp();
if (!expr1p->user1p() && !expr2p->user1p()) {
return; // no tristates in either expression, so nothing to do
}
AstNode* en1p = getEnp(expr1p);
AstNode* en2p = getEnp(expr2p);
AstNode* subexpr1p = expr1p->cloneTree(false);
AstNode* subexpr2p = expr2p->cloneTree(false);
if (isAnd) {
subexpr1p = new AstNot(nodep->fileline(), subexpr1p);
subexpr2p = new AstNot(nodep->fileline(), subexpr2p);
}
// calc new output enable
AstNode* enp = new AstOr(nodep->fileline(),
new AstAnd(nodep->fileline(), en1p, en2p),
new AstOr(nodep->fileline(),
new AstAnd(nodep->fileline(),
en1p->cloneTree(false),
subexpr1p),
new AstAnd(nodep->fileline(),
en2p->cloneTree(false),
subexpr2p)));
nodep->user1p(enp);
expr1p->user1p(NULL);
expr2p->user1p(NULL);
}
AstNode* en1p = getEnp(expr1p);
AstNode* en2p = getEnp(expr2p);
// calc new output enable.
AstNode* enp = new AstOr(nodep->fileline(),
new AstAnd(nodep->fileline(), en1p, en2p),
new AstOr(nodep->fileline(),
new AstAnd(nodep->fileline(),
en1p->cloneTree(false),
new AstNot(nodep->fileline(), expr1p->cloneTree(false))),
new AstAnd(nodep->fileline(),
en2p->cloneTree(false),
new AstNot(nodep->fileline(), expr2p->cloneTree(false)))));
nodep->user1p(enp);
expr1p->user1p(NULL);
expr2p->user1p(NULL);
}
virtual void visit(AstAnd* nodep, AstNUser*) {
visitAndOr(nodep,true);
}
virtual void visit(AstOr* nodep, AstNUser*) {
nodep->iterateChildren(*this);
UINFO(9,(m_alhs?"alhs":"")<<" "<<nodep<<endl);
if (m_alhs && nodep->user1p()) { nodep->v3error("Unsupported LHS tristate construct: "<<nodep->prettyTypeName()); return; }
// ORs have the same issues as ANDs. Earlier optimizations convert
// expressions like "(COND) ? 1'bz : 1'b1" to "COND | 1'bz". So we
// have to define what is means to OR 1'bz with other
// expressions. Here I take the approach that when one expression
// is 0, that is passes the other.
AstNode* expr1p = nodep->lhsp();
AstNode* expr2p = nodep->rhsp();
if (!expr1p->user1p() && !expr2p->user1p()) {
return; // no tristates in either expression, so nothing to do
}
AstNode* en1p = getEnp(expr1p);
AstNode* en2p = getEnp(expr2p);
// calc new output enable
AstNode* enp = new AstOr(nodep->fileline(),
new AstAnd(nodep->fileline(), en1p, en2p),
new AstOr(nodep->fileline(),
new AstAnd(nodep->fileline(),
en1p->cloneTree(false),
expr1p->cloneTree(false)),
new AstAnd(nodep->fileline(),
en2p->cloneTree(false),
expr2p->cloneTree(false))));
nodep->user1p(enp);
expr1p->user1p(NULL);
expr2p->user1p(NULL);
visitAndOr(nodep,false);
}
void visitAssign(AstNodeAssign* nodep) {