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DFG: Do not inline SystemC variables

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The emitted SystemC types (e.g. sc_bv) are not interchangeable with
Verilator internal C++ types (e.g.: VlWide), so the variables themselves
are not interchangeable (but can be assigned to/from each other). We can
preserve correctness simply be not inlining any SystemC variables (i.e.:
don't simplify any 'sc = nonSc' or 'nonSc = sc' assignments). SystemC
types only appear at top level ports so this should have no significant
impact.

Fixes #3688
This commit is contained in:
Geza Lore 2022-10-20 14:55:17 +01:00
parent 8c3ca30c91
commit 6a3ec17887
1 changed files with 16 additions and 2 deletions
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18
src/V3DfgPasses.cpp
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@ -134,9 +134,23 @@ void V3DfgPasses::inlineVars(DfgGraph& dfg) {
for (DfgVertexVar *vtxp = dfg.varVerticesBeginp(), *nextp; vtxp; vtxp = nextp) {
nextp = vtxp->verticesNext();
if (DfgVarPacked* const varp = vtxp->cast<DfgVarPacked>()) {
if (varp->hasSinks() && varp->isDrivenFullyByDfg()) {
// Don't inline SystemC variables, as SystemC types are not interchangeable with
// internal types, and hence the variables are not interchangeable either.
if (varp->hasSinks() && varp->isDrivenFullyByDfg() && !varp->varp()->isSc()) {
DfgVertex* const driverp = varp->source(0);
varp->forEachSinkEdge([=](DfgEdge& edge) { edge.relinkSource(driverp); });
// If driven from a SystemC variable, don't inline this variable
if (DfgVertexVar* const driverVarp = driverp->cast<DfgVarPacked>()) {
if (driverVarp->varp()->isSc()) continue;
}
varp->forEachSinkEdge([=](DfgEdge& edge) {
// If sink is a SystemC variable, don't inline that sink
if (DfgVertexVar* const sinkVarp = edge.sinkp()->cast<DfgVarPacked>()) {
if (sinkVarp->varp()->isSc()) return;
}
edge.relinkSource(driverp);
});
}
}
}