Fix inlining static initializer in V3Gate (#7503)

V3Gate could incorrectly inline a non-constant static initializer of
a variable into the use site if there are no other drivers. Disabling.

Fixes #5381

src/V3AstInlines.h

@@ -146,6 +146,7 @@ bool AstBasicDType::ascending() const {
 
 bool AstActive::hasClocked() const { return m_sentreep->hasClocked(); }
 bool AstActive::hasCombo() const { return m_sentreep->hasCombo(); }
+bool AstActive::hasStatic() const { return m_sentreep->hasStatic(); }
 
 AstAlways::AstAlways(AstAssignW* assignp)
     : ASTGEN_SUPER_Always(assignp->fileline(), assignp)

src/V3AstNodeOther.h

@@ -432,6 +432,7 @@ public:
     // METHODS
     inline bool hasClocked() const;
     inline bool hasCombo() const;
+    inline bool hasStatic() const;
 };
 class AstAlias final : public AstNode {
     // Alias construct - Used for source level net alias, and also for variable aliases internally

src/V3Gate.cpp

@@ -47,6 +47,7 @@ class GateEitherVertex VL_NOT_FINAL : public V3GraphVertex {
     bool m_reducible = true;  // True if this node should be able to be eliminated
     bool m_dedupable = true;  // True if this node should be able to be deduped
     bool m_consumed = false;  // Output goes to something meaningful
+    bool m_staticInit = false;  // True if this node is a static initializer
 public:
     explicit GateEitherVertex(V3Graph* graphp)
         : V3GraphVertex{graphp} {}
@@ -56,10 +57,12 @@ public:
     bool reducible() const { return m_reducible; }
     bool dedupable() const { return m_dedupable; }
     bool consumed() const { return m_consumed; }
+    bool staticInit() const { return m_staticInit; }
     void setConsumed(const char* /*consumedReason*/) {
         // if (!m_consumed) UINFO(0, "\t\tSetConsumed " << consumedReason << " " << this);
         m_consumed = true;
     }
+    void setStaticInit() { m_staticInit = true; }
     void clearReducible(const char* /*nonReducibleReason*/) {
         // UINFO(0, "     NR: " << nonReducibleReason << "  " << name());
         m_reducible = false;
@@ -196,6 +199,7 @@ class GateBuildVisitor final : public VNVisitorConst {
     const AstScope* m_scopep = nullptr;  // Current scope being processed
     AstActive* m_activep = nullptr;  // Current active
     bool m_inClockedActive = false;  // Underneath clocked active
+    bool m_inStaticActive = false;  // Underneath static active
     bool m_inSenItem = false;  // Underneath AstSenItem; any varrefs are clocks
 
     // METHODS
@@ -219,6 +223,8 @@ class GateBuildVisitor final : public VNVisitorConst {
             m_logicVertexp->clearReducibleAndDedupable(nonReducibleReason);
         } else if (m_inClockedActive) {
             m_logicVertexp->clearReducible("Clocked logic");  // but dedupable
+        } else if (m_inStaticActive) {
+            m_logicVertexp->setStaticInit();
         }
         if (consumeReason) m_logicVertexp->setConsumed(consumeReason);
         checkNode(nodep);
@@ -242,8 +248,10 @@ class GateBuildVisitor final : public VNVisitorConst {
         UASSERT_OBJ(!m_activep, nodep, "Should not nest");
         VL_RESTORER(m_activep);
         VL_RESTORER(m_inClockedActive);
+        VL_RESTORER(m_inStaticActive);
         m_activep = nodep;
         m_inClockedActive = nodep->hasClocked();
+        m_inStaticActive = nodep->hasStatic();
 
         // AstVarScope::user2 -> bool: Signal used in SenItem in *this* active block
         const VNUser2InUse user2InUse;
@@ -700,6 +708,9 @@ class GateInline final {
                 if (!VN_IS(substp, NodeVarRef)) continue;
             }
 
+            // Only inline static initializer if constant known at compile time
+            if (lVtxp->staticInit() && !VN_IS(substp, Const)) continue;
+
             // Process it
             ++m_statInlined;
 

test_regress/t/t_struct_initial_assign.py

@@ -13,6 +13,6 @@ test.scenarios('simulator')
 
 test.compile(verilator_flags2=["--timing"])
 
-test.execute(fails=test.vlt_all)  # Issue #5381
+test.execute()
 
 test.passes()

test_regress/t/t_struct_initial_assign.v

@@ -15,7 +15,7 @@ module t (
     input clk
 );
 
-  str_t bar_in;
+  str_t bar_in = '0;  // Set bar_in to 0 initially
   str_t bar_out;
 
   Sub sub (
@@ -28,8 +28,6 @@ module t (
     integer i;
     str_t initOut;
 
-    bar_in = '0;  // Set bar_in to 0 initially
-
     // Wait for the first falling edge of the clock
     @(negedge clk);