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Optimize associative constant patterns to fixed point (#8147)

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Re-associating constants can enable further simplification e.g. when
those constant become all zero/all ones. Run these patterns to fixed
point to capture the simplification, by revisiting the node.
This commit is contained in:
Geza Lore
2026-08-18 19:41:24 +02:00
committed by GitHub
parent 8a29360ade
commit 86b7cfb05c
1 changed files with 4 additions and 5 deletions
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src/V3Const.cpp
+4 -5
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@@ -1709,8 +1709,7 @@ class ConstVisitor final : public VNVisitor {
const V3Number num{constp, subsize, constp->num()};
nodep->lhsp(new AstConst{constp->fileline(), num});
VL_DO_DANGLING(pushDeletep(constp), constp);
UINFOTREE(9, nodep, "", "BI(EXTEND)-ou");
return true;
return false; // input node is still valid, keep going
}
bool operandBiExtendConstOver(const AstNodeBiop* nodep) {
// EQ(const{width32}, EXTEND(xx{width3})) -> constant
@@ -2070,7 +2069,7 @@ class ConstVisitor final : public VNVisitor {
rp->rhsp(bp);
rp->dtypeFrom(nodep); // Upper widthMin more likely correct
if (VN_IS(rp->lhsp(), Const) && VN_IS(rp->rhsp(), Const)) replaceConst(rp);
// UINFOTREE(1, nodep, "", "repAsvConst_new");
iterate(nodep); // Proceed to fixed point
}
void replaceAsvLUp(AstNodeBiop* nodep) {
// BIASV(BIASV(CONSTll,lr),r) -> BIASV(CONSTll,BIASV(lr,r))
@@ -2083,7 +2082,7 @@ class ConstVisitor final : public VNVisitor {
lp->lhsp(lrp);
lp->rhsp(rp);
lp->dtypeFrom(nodep); // Upper widthMin more likely correct
// UINFOTREE(1, nodep, "", "repAsvLUp_new");
iterate(nodep); // Proceed to fixed point
}
void replaceAsvRUp(AstNodeBiop* nodep) {
// BIASV(l,BIASV(CONSTrl,rr)) -> BIASV(CONSTrl,BIASV(l,rr))
@@ -2096,7 +2095,7 @@ class ConstVisitor final : public VNVisitor {
rp->lhsp(lp);
rp->rhsp(rrp);
rp->dtypeFrom(nodep); // Upper widthMin more likely correct
// UINFOTREE(1, nodep, "", "repAsvRUp_new");
iterate(nodep); // Proceed to fixed point
}
void replaceAndOr(AstNodeBiop* nodep) {
// OR (AND (CONSTll,lr), AND(CONSTrl==ll,rr)) -> AND (CONSTll, OR(lr,rr))