Internals: Track some VAccess that can be ReadOnly. No functional change.

src/V3Ast.h

@@ -140,8 +140,9 @@ public:
         : m_e(static_cast<en>(_e)) {}  // Need () or GCC 4.8 false warning
     operator en() const { return m_e; }
     VAccess invert() const { return (m_e == WRITE) ? VAccess(READ) : VAccess(WRITE); }
-    bool isRead() const { return m_e == READ; }
+    bool isReadOnly() const { return m_e == READ; }  // False if/when support READWRITE
-    bool isWrite() const { return m_e == WRITE; }
+    bool isWrite() const { return m_e == WRITE; }  // Need audit if/when support READWRITE
+    bool isWriteOnly() const { return m_e == WRITE; }  // False if/when support READWRITE
 };
 inline bool operator==(const VAccess& lhs, const VAccess& rhs) { return lhs.m_e == rhs.m_e; }
 inline bool operator==(const VAccess& lhs, VAccess::en rhs) { return lhs.m_e == rhs; }

src/V3AstNodes.h

@@ -2360,7 +2360,7 @@ public:
         }
     }
     virtual int instrCount() const override {
-        return widthInstrs() * (access().isWrite() ? 1 : instrCountLd());
+        return widthInstrs() * (access().isWriteOnly() ? 1 : instrCountLd());
     }
     virtual string emitVerilog() override { V3ERROR_NA_RETURN(""); }
     virtual string emitC() override { V3ERROR_NA_RETURN(""); }

src/V3Cast.cpp

@@ -154,7 +154,7 @@ private:
         }
     }
     virtual void visit(AstVarRef* nodep) override {
-        if (nodep->access().isRead() && !VN_IS(nodep->backp(), CCast)
+        if (nodep->access().isReadOnly() && !VN_IS(nodep->backp(), CCast)
             && VN_IS(nodep->backp(), NodeMath) && !VN_IS(nodep->backp(), ArraySel)
             && nodep->backp()->width() && castSize(nodep) != castSize(nodep->varp())) {
             // Cast vars to IData first, else below has upper bits wrongly set

src/V3Const.cpp

@@ -1605,7 +1605,7 @@ private:
             // if (debug()) valuep->dumpTree(cout, "  visitvaref: ");
             iterateAndNextNull(nodep->varp()->valuep());  // May change nodep->varp()->valuep()
             AstNode* valuep = nodep->varp()->valuep();
-            if (!nodep->access().isWrite()
+            if (nodep->access().isReadOnly()
                 && ((!m_params  // Can reduce constant wires into equations
                      && m_doNConst
                      && v3Global.opt.oConst()

src/V3Gate.cpp

@@ -842,7 +842,7 @@ private:
             // It's possible we substitute into something that will be reduced more later,
             // however, as we never delete the top Always/initial statement, all should be well.
             m_didReplace = true;
-            UASSERT_OBJ(!nodep->access().isWrite(), nodep,
+            UASSERT_OBJ(nodep->access().isReadOnly(), nodep,
                         "Can't replace lvalue assignments with const var");
             AstNode* substp = m_replaceTreep->cloneTree(false);
             UASSERT_OBJ(

src/V3Simulate.h

@@ -433,7 +433,7 @@ private:
             }
         }
         if (!m_checkOnly && optimizable()) {  // simulating
-            UASSERT_OBJ(!nodep->access().isWrite(), nodep,
+            UASSERT_OBJ(nodep->access().isReadOnly(), nodep,
                         "LHS varref should be handled in AstAssign visitor.");
             {
                 // Return simulation value - copy by reference instead of value for speed

src/V3Subst.cpp

@@ -306,7 +306,7 @@ private:
         iterate(nodep->rhsp());
         AstVarRef* varrefp = VN_CAST(nodep->lhsp(), VarRef);
         AstConst* constp = VN_CAST(nodep->rhsp(), Const);
-        if (varrefp && isSubstVar(varrefp->varp()) && !varrefp->access().isWrite() && constp) {
+        if (varrefp && isSubstVar(varrefp->varp()) && varrefp->access().isReadOnly() && constp) {
             // Nicely formed lvalues handled in NodeAssign
             // Other lvalues handled as unknown mess in AstVarRef
             int word = constp->toUInt();

src/V3Trace.cpp

@@ -845,7 +845,7 @@ private:
     virtual void visit(AstVarRef* nodep) override {
         if (m_tracep) {
             UASSERT_OBJ(nodep->varScopep(), nodep, "No var scope?");
-            UASSERT_OBJ(!nodep->access().isWrite(), nodep, "Lvalue in trace?  Should be const.");
+            UASSERT_OBJ(nodep->access().isReadOnly(), nodep, "Lvalue in trace?  Should be const.");
             V3GraphVertex* varVtxp = nodep->varScopep()->user1u().toGraphVertex();
             if (!varVtxp) {
                 varVtxp = new TraceVarVertex(&m_graph, nodep->varScopep());

src/V3WidthSel.cpp

@@ -280,10 +280,10 @@ private:
                               "Unsupported: String array operation on non-variable");
             }
             AstNode* newp;
-            if (varrefp && varrefp->access().isWrite()) {
+            if (varrefp && varrefp->access().isReadOnly()) {
-                newp = new AstGetcRefN(nodep->fileline(), fromp, rhsp);
-            } else {
                 newp = new AstGetcN(nodep->fileline(), fromp, rhsp);
+            } else {
+                newp = new AstGetcRefN(nodep->fileline(), fromp, rhsp);
             }
             UINFO(6, "   new " << newp << endl);
             nodep->replaceWith(newp);