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Fix rand variable used as array index in constraint evaluated as constant (#7238) (#7247)

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This commit is contained in:
Yilou Wang
2026-03-12 10:12:53 -04:00
committed by GitHub
parent 08c6d5bde5
commit c74eee5123
3 changed files with 87 additions and 4 deletions
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src/V3Randomize.cpp
+25 -4
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@@ -1672,10 +1672,31 @@ class ConstraintExprVisitor final : public VNVisitor {
if (editFormat(nodep)) return;
FileLine* const fl = nodep->fileline();
VNRelinker handle;
AstNodeExpr* const indexp
= new AstSFormatF{fl, "#x%8x", false, nodep->bitp()->unlinkFrBack(&handle)};
handle.relink(indexp);
editSMT(nodep, nodep->fromp(), indexp);
// Check if index actually references a rand variable (not just user1,
// which can be over-marked in sum/with expansion contexts)
bool indexIsRand = false;
nodep->bitp()->foreach([&](const AstNodeVarRef* vrefp) {
if (vrefp->varp()->rand().isRandomizable()) indexIsRand = true;
});
if (indexIsRand) {
// Index depends on rand variable -- keep as SMT symbol.
// Array index sort is 32-bit, so zero-extend narrower indices.
AstNodeExpr* indexp = nodep->bitp()->unlinkFrBack(&handle);
if (indexp->width() < 32) {
AstExtend* const extendp = new AstExtend{fl, indexp, 32};
extendp->dtypeSetLogicSized(32, VSigning::UNSIGNED);
extendp->user1(true);
indexp = extendp;
}
handle.relink(indexp);
editSMT(nodep, nodep->fromp(), indexp);
} else {
// Index is constant or non-rand -- format as hex literal
AstNodeExpr* const indexp
= new AstSFormatF{fl, "#x%8x", false, nodep->bitp()->unlinkFrBack(&handle)};
handle.relink(indexp);
editSMT(nodep, nodep->fromp(), indexp);
}
}
void visit(AstMemberSel* nodep) override {
// Check if rootVar is globalConstrained