Support clocking blocks in virtual interfaces (#5235)

src/V3Sampled.cpp

@@ -0,0 +1,105 @@
+// -*- mode: C++; c-file-style: "cc-mode" -*-
+//*************************************************************************
+// DESCRIPTION: Verilator: Removal of SAMPLED
+//
+// Code available from: https://verilator.org
+//
+//*************************************************************************
+//
+// Copyright 2003-2024 by Wilson Snyder. This program is free software; you
+// can redistribute it and/or modify it under the terms of either the GNU
+// Lesser General Public License Version 3 or the Perl Artistic License
+// Version 2.0.
+// SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+//
+//*************************************************************************
+// V3Sampled's Transformations:
+//
+// Top Scope:
+//   Replace each variable reference under SAMPLED with a new variable.
+//   Remove SAMPLED.
+//
+//*************************************************************************
+
+#include "V3PchAstNoMT.h"  // VL_MT_DISABLED_CODE_UNIT
+
+#include "V3Sampled.h"
+
+VL_DEFINE_DEBUG_FUNCTIONS;
+
+//######################################################################
+// Clock state, as a visitor of each AstNode
+
+class SampledVisitor final : public VNVisitor {
+    // NODE STATE
+    //  AstVarScope::user1()  -> AstVarScope*. The VarScope that stores sampled value
+    //  AstVarRef::user1()    -> bool. Whether already converted
+    const VNUser1InUse m_user1InUse;
+    // STATE
+    AstScope* m_scopep = nullptr;  // Current scope
+    bool m_inSampled = false;  // True inside a sampled expression
+
+    // METHODS
+
+    AstVarScope* createSampledVar(AstVarScope* vscp) {
+        if (vscp->user1p()) return VN_AS(vscp->user1p(), VarScope);
+        const AstVar* const varp = vscp->varp();
+        const string newvarname
+            = "__Vsampled_" + vscp->scopep()->nameDotless() + "__" + varp->name();
+        FileLine* const flp = vscp->fileline();
+        AstVar* const newvarp = new AstVar{flp, VVarType::MODULETEMP, newvarname, varp->dtypep()};
+        m_scopep->modp()->addStmtsp(newvarp);
+        AstVarScope* const newvscp = new AstVarScope{flp, m_scopep, newvarp};
+        newvarp->direction(VDirection::INPUT);  // Inform V3Sched that it will be driven later
+        newvarp->primaryIO(true);
+        vscp->user1p(newvscp);
+        m_scopep->addVarsp(newvscp);
+        // At the top of _eval, assign them (use valuep here as temporary storage during V3Sched)
+        newvarp->valuep(new AstVarRef{flp, vscp, VAccess::READ});
+        UINFO(4, "New Sampled: " << newvscp << endl);
+        return newvscp;
+    }
+
+    // VISITORS
+    void visit(AstScope* nodep) override {
+        VL_RESTORER(m_scopep);
+        m_scopep = nodep;
+        iterateChildren(nodep);
+    }
+    void visit(AstSampled* nodep) override {
+        VL_RESTORER(m_inSampled);
+        m_inSampled = true;
+        iterateChildren(nodep);
+        nodep->replaceWith(nodep->exprp()->unlinkFrBack());
+        VL_DO_DANGLING(pushDeletep(nodep), nodep);
+    }
+    void visit(AstVarRef* nodep) override {
+        iterateChildren(nodep);
+        if (m_inSampled && !nodep->user1SetOnce()) {
+            UASSERT_OBJ(nodep->access().isReadOnly(), nodep, "Should have failed in V3Access");
+            AstVarScope* const varscp = nodep->varScopep();
+            AstVarScope* const lastscp = createSampledVar(varscp);
+            AstNode* const newp = new AstVarRef{nodep->fileline(), lastscp, VAccess::READ};
+            newp->user1SetOnce();  // Don't sample this one
+            nodep->replaceWith(newp);
+            VL_DO_DANGLING(pushDeletep(nodep), nodep);
+        }
+    }
+
+    //--------------------
+    void visit(AstNode* nodep) override { iterateChildren(nodep); }
+
+public:
+    // CONSTRUCTORS
+    explicit SampledVisitor(AstNetlist* netlistp) { iterate(netlistp); }
+    ~SampledVisitor() override = default;
+};
+
+//######################################################################
+// Sampled class functions
+
+void V3Sampled::sampledAll(AstNetlist* nodep) {
+    UINFO(2, __FUNCTION__ << ": " << endl);
+    { SampledVisitor{nodep}; }  // Destruct before checking
+    V3Global::dumpCheckGlobalTree("sampled", 0, dumpTreeEitherLevel() >= 3);
+}