Review fixes

docs/guide/exe_verilator.rst

@@ -749,8 +749,8 @@ Summary:
    externally between evaluations. The optimization is automatically disabled
    for top level input signals that are written within the design. Accesses via
    the VPI cannot be analyzed at compile time, therefore :vlopt:`--vpi`
-   disables this optimization. It can be turned back on by explicitly passing
+   disables this optimization for all inputs; it may be turned back on by
-   :vlopt:`-fico-change-detect`.
+   explicitly passing :vlopt:`-fico-change-detect`.
 
 .. option:: -fno-inline
 

src/V3AstNodeOther.h

@@ -2138,6 +2138,7 @@ class AstVar final : public AstNode {
     bool m_attrFsmArcInclCond : 1;  // declared with fsm_arc_include_cond metacomment
     bool m_fileDescr : 1;  // File descriptor
     bool m_gotNansiType : 1;  // Linker saw Non-ANSI type declaration
+    bool m_icoMaybeWritten : 1;  // Design might write this input signal - for ico change detect
     bool m_isConst : 1;  // Table contains constant data
     bool m_isContinuously : 1;  // Ever assigned continuously (for force/release)
     bool m_hasStrengthAssignment : 1;  // Is on LHS of assignment with strength specifier
@@ -2151,7 +2152,6 @@ class AstVar final : public AstNode {
     bool m_isDpiOpenArray : 1;  // DPI import open array
     bool m_isHideLocal : 1;  // Verilog local
     bool m_isHideProtected : 1;  // Verilog protected
-    bool m_maybeWritten : 1;  // Design might write to this signal (not very accurate)
     bool m_noCReset : 1;  // Do not do automated CReset creation
     bool m_noReset : 1;  // Do not do automated reset/randomization
     bool m_noSubst : 1;  // Do not substitute out references
@@ -2201,6 +2201,7 @@ class AstVar final : public AstNode {
         m_attrFsmArcInclCond = false;
         m_fileDescr = false;
         m_gotNansiType = false;
+        m_icoMaybeWritten = false;
         m_isConst = false;
         m_isContinuously = false;
         m_hasStrengthAssignment = false;
@@ -2214,7 +2215,6 @@ class AstVar final : public AstNode {
         m_isDpiOpenArray = false;
         m_isHideLocal = false;
         m_isHideProtected = false;
-        m_maybeWritten = false;
         m_noCReset = false;
         m_noReset = false;
         m_noSubst = false;
@@ -2381,14 +2381,14 @@ public:
     void hasStrengthAssignment(bool flag) { m_hasStrengthAssignment = flag; }
     bool hasUserInit() const { return m_hasUserInit; }
     void hasUserInit(bool flag) { m_hasUserInit = flag; }
+    void icoMaybeWritten(bool flag) { m_icoMaybeWritten = flag; }
+    bool icoMaybeWritten() const { return m_icoMaybeWritten; }
     bool isDpiOpenArray() const VL_MT_SAFE { return m_isDpiOpenArray; }
     void isDpiOpenArray(bool flag) { m_isDpiOpenArray = flag; }
     bool isHideLocal() const { return m_isHideLocal; }
     void isHideLocal(bool flag) { m_isHideLocal = flag; }
     bool isHideProtected() const { return m_isHideProtected; }
     void isHideProtected(bool flag) { m_isHideProtected = flag; }
-    void maybeWritten(bool flag) { m_maybeWritten = flag; }
-    bool maybeWritten() const { return m_maybeWritten; }
     bool noCReset() const { return m_noCReset; }
     void noCReset(bool flag) { m_noCReset = flag; }
     bool noReset() const { return m_noReset; }

src/V3AstNodes.cpp

@@ -630,6 +630,7 @@ void AstVar::combineType(const AstVar* otherp) {
         varType(otherp->varType());
         direction(otherp->direction());
     }
+    if (otherp->icoMaybeWritten()) icoMaybeWritten(true);
 }
 void AstVar::combineType(VVarType type) {
     // These flags get combined with the existing settings of the flags.
@@ -3215,6 +3216,7 @@ void AstVar::dump(std::ostream& str) const {
         str << " [FUNC]";
     }
     if (hasUserInit()) str << " [UINIT]";
+    if (icoMaybeWritten()) str << " [ICOMAYBEWRITTEN]";
     if (isDpiOpenArray()) str << " [DPIOPENA]";
     if (ignorePostWrite()) str << " [IGNPWR]";
     if (ignoreSchedWrite()) str << " [IGNWR]";
@@ -3243,6 +3245,7 @@ void AstVar::dumpJson(std::ostream& str) const {
     dumpJsonBoolFuncIf(str, attrFsmResetArc);
     dumpJsonBoolFuncIf(str, attrFsmArcInclCond);
     dumpJsonBoolFuncIf(str, attrFileDescr);
+    dumpJsonBoolFuncIf(str, icoMaybeWritten);
     dumpJsonBoolFuncIf(str, isDpiOpenArray);
     dumpJsonBoolFuncIf(str, isFuncReturn);
     dumpJsonBoolFuncIf(str, isFuncLocal);

src/V3LinkLevel.cpp

@@ -291,7 +291,7 @@ void V3LinkLevel::wrapTopCell(AstNetlist* rootp) {
                     varp->sigPublic(true);  // User needs to be able to get to it...
                     oldvarp->primaryIO(false);
                     varp->primaryIO(true);
-                    varp->maybeWritten(oldvarp->maybeWritten());
+                    varp->icoMaybeWritten(oldvarp->icoMaybeWritten());
                     if (varp->isRef() || varp->isConstRef()) {
                         varp->v3warn(E_UNSUPPORTED,
                                      "Unsupported: ref/const ref as primary input/output: "

src/V3Sched.cpp

@@ -548,7 +548,7 @@ AstNode* createInputCombLoop(AstNetlist* netlistp, AstCFunc* const initFuncp,
             // Only for top level ports, assume outputs don't change externally
             if (!vscp->varp()->isPrimaryInish()) continue;
             // Don't do if written by the design - wouldn't update the change detect 'prev' value
-            if (vscp->varp()->maybeWritten()) continue;
+            if (vscp->varp()->icoMaybeWritten()) continue;
             // Don't do if forceable, as we can't see the actual value - this is belt and braces
             if (vscp->varp()->isForced()) continue;
             // Can't handle unpacked arrays (they have special types when primary input)

src/V3Width.cpp

@@ -3073,7 +3073,7 @@ class WidthVisitor final : public VNVisitor {
             UASSERT_OBJ(nodep->dtypep(), nodep, "LHS var should be dtype completed");
         }
         // UINFOTREE(9, nodep, "", "VRout");
-        if (nodep->access().isWriteOrRW()) nodep->varp()->maybeWritten(true);
+        if (nodep->access().isWriteOrRW()) nodep->varp()->icoMaybeWritten(true);
         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()->isInput()