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Add support for $countones in constraints (#6144) (#6235)

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This commit is contained in:
Ryszard Rozak
2025-07-28 16:14:03 +02:00
committed by GitHub
parent 0bd291e6cd
commit a5b0a0d9dd
7 changed files with 151 additions and 3 deletions
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src/V3Randomize.cpp
+36 -2
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@@ -532,8 +532,10 @@ class ConstraintExprVisitor final : public VNVisitor {
AstNodeExpr* thsp = nullptr) {
// Replace incomputable (result-dependent) expression with SMT expression
std::string smtExpr = nodep->emitSMT(); // Might need child width (AstExtend)
UASSERT_OBJ(smtExpr != "", nodep,
"Node needs randomization constraint, but no emitSMT: " << nodep);
if (smtExpr == "") {
nodep->v3warn(E_UNSUPPORTED, "Unsupported expression inside constraint");
return;
}
if (lhsp)
lhsp = VN_AS(iterateSubtreeReturnEdits(lhsp->backp() ? lhsp->unlinkFrBack() : lhsp),
@@ -718,6 +720,38 @@ class ConstraintExprVisitor final : public VNVisitor {
initTaskp->addStmtsp(methodp->makeStmt());
}
}
void visit(AstCountOnes* nodep) override {
// Convert it to (x & 1) + ((x & 2) >> 1) + ((x & 4) >> 2) + ...
FileLine* const fl = nodep->fileline();
AstNodeExpr* const argp = nodep->lhsp()->unlinkFrBack();
V3Number numOne{nodep, argp->width(), 1};
AstNodeExpr* sump = new AstAnd{fl, argp, new AstConst{fl, numOne}};
sump->user1(true);
for (int i = 1; i < argp->width(); i++) {
V3Number numBitMask{nodep, argp->width(), 0};
numBitMask.setBit(i, 1);
AstAnd* const andp
= new AstAnd{fl, argp->cloneTreePure(false), new AstConst{fl, numBitMask}};
andp->user1(true);
AstShiftR* const shiftp = new AstShiftR{
fl, andp, new AstConst{fl, AstConst::WidthedValue{}, argp->width(), (uint32_t)i}};
shiftp->user1(true);
shiftp->dtypeFrom(nodep);
sump = new AstAdd{nodep->fileline(), sump, shiftp};
sump->user1(true);
}
// Restore the original width
if (nodep->width() > sump->width()) {
sump = new AstExtend{fl, sump, nodep->width()};
sump->user1(true);
} else if (nodep->width() < sump->width()) {
sump = new AstSel{fl, sump, 0, nodep->width()};
sump->user1(true);
}
nodep->replaceWith(sump);
VL_DO_DANGLING(nodep->deleteTree(), nodep);
iterate(sump);
}
void visit(AstNodeBiop* nodep) override {
if (editFormat(nodep)) return;
editSMT(nodep, nodep->lhsp(), nodep->rhsp());