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Optimize tristate structure OR(AND(x,y),AND(z,y)).

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This commit is contained in:
Wilson Snyder 2012-05-08 19:20:23 -04:00
parent f5ace0f72a
commit ac61548e6a
1 changed files with 29 additions and 9 deletions
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26
src/V3Const.cpp
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@ -174,13 +174,16 @@ private:
return rnodep->lhsp()->castConst();
}
static bool operandAndOrSame(AstNode* nodep) {
// OR( AND(VAL,x), AND(VAL,y)) -> AND(VAL,OR(x,y))
// OR( AND(x,VAL), AND(y,VAL)) -> AND(OR(x,y),VAL)
AstNodeBiop* np = nodep->castNodeBiop();
AstNodeBiop* lp = np->lhsp()->castNodeBiop();
AstNodeBiop* rp = np->rhsp()->castNodeBiop();
return (lp && rp
&& lp->width()==rp->width()
&& lp->type()==rp->type()
&& operandsSame(lp->lhsp(),rp->lhsp()));
&& (operandsSame(lp->lhsp(),rp->lhsp())
|| operandsSame(lp->rhsp(),rp->rhsp())));
}
static bool matchOrAndNot(AstNodeBiop* nodep) {
// AstOr{$a, AstAnd{AstNot{$b}, $c}} if $a.width1, $a==$b => AstOr{$a,$c}
@ -410,7 +413,11 @@ private:
return node1p->sameTree(node2p);
}
else if (node1p->castVarRef() && node2p->castVarRef()) {
return node1p->sameTree(node2p);
// Avoid comparing widthMin's, which results in lost optimization attempts
// If cleanup sameTree to be smarter, this can be restored.
//return node1p->sameTree(node2p);
return node1p->castVarRef()->varp() == node2p->castVarRef()->varp()
&& node1p->castVarRef()->lvalue() == node2p->castVarRef()->lvalue();
} else {
return false;
}
@ -604,7 +611,9 @@ private:
//nodep->dumpTree(cout, " repAsvRUp_new: ");
}
void replaceAndOr (AstNodeBiop* nodep) {
// Or(And(CONSTll,lr),And(CONSTrl==ll,rr)) -> And(CONSTll,Or(lr,rr))
// OR (AND (CONSTll,lr), AND(CONSTrl==ll,rr)) -> AND (CONSTll, OR(lr,rr))
// OR (AND (CONSTll,lr), AND(CONSTrl, rr=lr)) -> AND (OR(ll,rl), rr)
// nodep ^lp ^llp ^lrp ^rp ^rlp ^rrp
// (Or/And may also be reversed)
AstNodeBiop* lp = nodep->lhsp()->unlinkFrBack()->castNodeBiop();
AstNode* llp = lp->lhsp()->unlinkFrBack();
@ -613,12 +622,23 @@ private:
AstNode* rlp = rp->lhsp()->unlinkFrBack();
AstNode* rrp = rp->rhsp()->unlinkFrBack();
nodep->replaceWith(lp);
if (operandsSame(llp,rlp)) {
lp->lhsp(llp);
lp->rhsp(nodep);
nodep->lhsp(lrp);
nodep->rhsp(rrp);
rp->deleteTree();
rlp->deleteTree();
} else if (operandsSame(lrp, rrp)) {
lp->lhsp(nodep);
lp->rhsp(rrp);
nodep->lhsp(llp);
nodep->rhsp(rlp);
rp->deleteTree();
lrp->deleteTree();
} else {
nodep->v3fatalSrc("replaceAndOr on something operandAndOrSame shouldn't have matched");
}
//nodep->dumpTree(cout, " repAndOr_new: ");
}
void replaceShiftSame (AstNodeBiop* nodep) {