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Internals: Factor out inlining predicate in V3Gate 

No functional change.
This commit is contained in:
Geza Lore 2026-06-04 09:33:22 +01:00
parent 81282c3d57
commit 14cf611c72
1 changed files with 54 additions and 33 deletions
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87
src/V3Gate.cpp
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@ -582,6 +582,52 @@ class GateInline final {
return false;
}
bool shouldInline(GateVarVertex* vVtxp, GateLogicVertex* lVtxp, size_t nReads,
AstNodeExpr* substp, bool allowMultiIn) {
AstVarScope* const vscp = vVtxp->varScp();
// Always inline constants
if (VN_IS(substp, Const)) return true;
// Don't inline non-constant static initializers
if (lVtxp->staticInit()) return false;
// Inline simple variable references
if (VN_IS(substp, VarRef)) return true;
// Only inline arrays if a simple variable or constant
if (VN_IS(vscp->dtypep()->skipRefp(), UnpackArrayDType)) return false;
// Inline constant array selects
if (VN_IS(substp, ArraySel) && nReads <= 1) return true;
// Don't inline expensive wide operations
if (excludedWide(vVtxp, substp)) {
++m_statExcluded;
UINFO(9, "Gate inline exclude '" << vVtxp->name() << "'");
vVtxp->clearReducible("Excluded wide"); // Check once.
return false;
}
if (nReads == 0) {
// Reads no variables, likely unfolded constant expression
return true;
} else if (nReads == 1) {
// Reads one variable
return true;
} else {
// Reads more two or more variables
if (!allowMultiIn) return false;
// Do it if not used, or used only once, ignoring slow code
int n = 0;
for (V3GraphEdge& edge : vVtxp->outEdges()) {
const GateLogicVertex* const dstVtxp = edge.top()->as<GateLogicVertex>();
// Ignore slow code, or if the destination is not used
if (dstVtxp->slow()) continue;
if (dstVtxp->outEmpty() && !dstVtxp->consumed()) continue;
n += edge.weight();
if (n > 1) return false;
}
return true;
}
}
void recordSubstitution(AstVarScope* vscp, AstNodeExpr* substp, AstNode* logicp) {
m_hasPending.emplace(logicp, ++m_ord); // It's OK if already present
const auto pair = m_substitutions(logicp).emplace(vscp, nullptr);
@ -676,46 +722,21 @@ class GateInline final {
if (!okVisitor.isSimple()) continue;
// If the varScope is already removed from logicp, no need to try substitution.
if (!okVisitor.varAssigned(vVtxp->varScp())) continue;
if (excludedWide(vVtxp, okVisitor.substitutionp())) {
++m_statExcluded;
UINFO(9, "Gate inline exclude '" << vVtxp->name() << "'");
vVtxp->clearReducible("Excluded wide"); // Check once.
continue;
}
// Does it read multiple source variables?
if (okVisitor.readVscps().size() > 1) {
if (!allowMultiIn) {
continue;
} else {
// Do it if not used, or used only once, ignoring slow code
int n = 0;
for (V3GraphEdge& edge : vVtxp->outEdges()) {
const GateLogicVertex* const dstVtxp = edge.top()->as<GateLogicVertex>();
// Ignore slow code, or if the destination is not used
if (dstVtxp->slow()) continue;
if (dstVtxp->outEmpty() && !dstVtxp->consumed()) continue;
n += edge.weight();
if (n > 1) break;
}
if (n > 1) continue;
}
}
AstVarScope* const vscp = vVtxp->varScp();
// Expression we are considering to substitute with
AstNodeExpr* const substp = okVisitor.substitutionp();
// Number of variables read by the substitution
const size_t nReads = okVisitor.readVscps().size();
// Only inline arrays if a simple variable
if (VN_IS(vscp->dtypep()->skipRefp(), UnpackArrayDType)) {
if (!VN_IS(substp, NodeVarRef)) continue;
}
// Only inline static initializer if constant known at compile time
if (lVtxp->staticInit() && !VN_IS(substp, Const)) continue;
// Check if it should be inlined
if (!shouldInline(vVtxp, lVtxp, nReads, substp, allowMultiIn)) continue;
// Process it
++m_statInlined;
// Variable we are considering to substitute
AstVarScope* const vscp = vVtxp->varScp();
if (debug() >= 9) {
vscp->dumpTree("substituting: ");
substp->dumpTree(" with: ");