Add separate AstInitialStatic node for static initializers

Static variable initializers run before initial blocks, so use an
explicitly different procedure type for them. This also enables us to
now raise errors for assignments to const variables in initial blocks.

Changes

@@ -15,6 +15,7 @@ Verilator 4.221 devel
 
 * Split --prof-threads into --prof-exec and --prof-pgo (#3365). [Geza Lore, Shunyao CAD]
 * Deprecate 'vluint64_t' and similar types (#3255).
+* Raise error on assignment to const in initial blocks. [Geza Lore, Shunyao CAD]
 * Fix MSVC localtime_s (#3124).
 * Fix Bison 3.8.2 error (#3366). [elike-ypq]
 * Fix rare bug in -Oz (V3Localize) (#3286). [Geza Lore, Shunyao CAD]

src/V3Active.cpp

@@ -422,6 +422,14 @@ private:
     virtual void visit(AstActive* nodep) override {
         // Actives are being formed, so we can ignore any already made
     }
+    virtual void visit(AstInitialStatic* nodep) override {
+        // Relink to IACTIVE, unless already under it
+        UINFO(4, "    INITIAL " << nodep << endl);
+        const ActiveDlyVisitor dlyvisitor{nodep, ActiveDlyVisitor::CT_INITIAL};
+        AstActive* const wantactivep = m_namer.getIActive(nodep->fileline());
+        nodep->unlinkFrBack();
+        wantactivep->addStmtsp(nodep);
+    }
     virtual void visit(AstInitial* nodep) override {
         // Relink to IACTIVE, unless already under it
         UINFO(4, "    INITIAL " << nodep << endl);

src/V3AstNodes.h

@@ -3407,7 +3407,7 @@ public:
 };
 
 class AstInitialAutomatic final : public AstNodeProcedure {
-    // initial for automatic variables
+    // Automatic variable initialization
     // That is, it runs every function start, or class construction
 public:
     AstInitialAutomatic(FileLine* fl, AstNode* bodysp)
@@ -3415,6 +3415,15 @@ public:
     ASTNODE_NODE_FUNCS(InitialAutomatic)
 };
 
+class AstInitialStatic final : public AstNodeProcedure {
+    // Static variable initialization
+    // That is, it runs at the beginning of simulation, before 'initial' blocks
+public:
+    AstInitialStatic(FileLine* fl, AstNode* bodysp)
+        : ASTGEN_SUPER_InitialStatic(fl, bodysp) {}
+    ASTNODE_NODE_FUNCS(InitialStatic)
+};
+
 class AstAlways final : public AstNodeProcedure {
     const VAlwaysKwd m_keyword;
 

src/V3Cdc.cpp

@@ -716,6 +716,7 @@ private:
     // Ignores
     virtual void visit(AstInitial*) override {}
     virtual void visit(AstInitialAutomatic*) override {}
+    virtual void visit(AstInitialStatic*) override {}
     virtual void visit(AstTraceDecl*) override {}
     virtual void visit(AstCoverToggle*) override {}
     virtual void visit(AstNodeDType*) override {}

src/V3Class.cpp

@@ -153,6 +153,11 @@ private:
         iterateChildren(nodep);
         if (m_packageScopep) { m_toScopeMoves.push_back(std::make_pair(nodep, m_packageScopep)); }
     }
+    virtual void visit(AstInitialStatic* nodep) override {
+        // But not AstInitialAutomatic, which remains under the class
+        iterateChildren(nodep);
+        if (m_packageScopep) { m_toScopeMoves.push_back(std::make_pair(nodep, m_packageScopep)); }
+    }
 
     virtual void visit(AstNodeMath* nodep) override {}  // Short circuit
     virtual void visit(AstNodeStmt* nodep) override {}  // Short circuit
@@ -173,7 +178,7 @@ public:
                 vscp->scopep(scopep);
                 vscp->unlinkFrBack();
                 scopep->addVarp(vscp);
-            } else if (VN_IS(nodep, Initial)) {
+            } else if (VN_IS(nodep, Initial) || VN_IS(nodep, InitialStatic)) {
                 nodep->unlinkFrBack();
                 scopep->addActivep(nodep);
             } else {

src/V3EmitV.cpp

@@ -99,6 +99,7 @@ class EmitVBaseVisitor VL_NOT_FINAL : public EmitCBaseVisitor {
         putqs(nodep, "end\n");
     }
     virtual void visit(AstInitialAutomatic* nodep) override { iterateChildrenConst(nodep); }
+    virtual void visit(AstInitialStatic* nodep) override { iterateChildrenConst(nodep); }
     virtual void visit(AstAlways* nodep) override {
         putfs(nodep, "always ");
         if (m_sensesp) {

src/V3LinkParse.cpp

@@ -275,7 +275,7 @@ private:
                 if (nodep->lifetime().isAutomatic()) {
                     nodep->addNextHere(new AstInitialAutomatic{newfl, assp});
                 } else {
-                    nodep->addNextHere(new AstInitial{newfl, assp});
+                    nodep->addNextHere(new AstInitialStatic{newfl, assp});
                 }
             }  // 4. Under blocks, it's an initial value to be under an assign
             else {

src/V3Order.cpp

@@ -662,6 +662,9 @@ class OrderBuildVisitor final : public VNVisitor {
     virtual void visit(AstInitialAutomatic* nodep) override {  //
         iterateLogic(nodep);
     }
+    virtual void visit(AstInitialStatic* nodep) override {  //
+        iterateLogic(nodep);
+    }
     virtual void visit(AstAlways* nodep) override {  //
         iterateLogic(nodep);
     }

src/V3Width.cpp

@@ -2041,7 +2041,8 @@ private:
         if (nodep->access().isWriteOrRW() && nodep->varp()->direction() == VDirection::CONSTREF) {
             nodep->v3error("Assigning to const ref variable: " << nodep->prettyNameQ());
         } else if (nodep->access().isWriteOrRW() && nodep->varp()->isConst() && !m_paramsOnly
-                   && (!m_ftaskp || !m_ftaskp->isConstructor()) && !VN_IS(m_procedurep, Initial)) {
+                   && (!m_ftaskp || !m_ftaskp->isConstructor())
+                   && !VN_IS(m_procedurep, InitialStatic)) {
             // Too loose, but need to allow our generated first assignment
             // Move this to a property of the AstInitial block
             nodep->v3error("Assigning to const variable: " << nodep->prettyNameQ());