Support vpiBitVar (#7107).

Fixes #7107.

include/verilated.h

@@ -157,7 +157,8 @@ enum VerilatedVarFlags {
     VLVF_DPI_CLAY = (1 << 10),  // DPI compatible C standard layout
     VLVF_CONTINUOUSLY = (1 << 11),  // Is continously assigned
     VLVF_FORCEABLE = (1 << 12),  // Forceable
-    VLVF_SIGNED = (1 << 13)  // Signed integer
+    VLVF_SIGNED = (1 << 13),  // Signed integer
+    VLVF_BITVAR = (1 << 14)  // Four state bit (vs two state logic)
 };
 
 // IEEE 1800-2023 Table 20-6

include/verilated_sym_props.h

@@ -161,6 +161,7 @@ public:
     // DPI compatible C standard layout
     bool isDpiCLayout() const { return ((m_vlflags & VLVF_DPI_CLAY) != 0); }
     bool isSigned() const { return ((m_vlflags & VLVF_SIGNED) != 0); }
+    bool isBitVar() const { return ((m_vlflags & VLVF_BITVAR) != 0); }
     int udims() const VL_MT_SAFE { return m_unpacked.size(); }
     int pdims() const VL_MT_SAFE { return m_packed.size(); }
     int dims() const VL_MT_SAFE { return pdims() + udims(); }

include/verilated_vpi.cpp

@@ -421,11 +421,12 @@ public:
         return ret;
     }
     uint32_t type() const override {
-        uint32_t type = vpiReg;
+        uint32_t type;
+        // TODO have V3EmitCSyms.cpp put vpiType directly into constant table
         switch (varp()->vltype()) {
         case VLVT_REAL: type = vpiRealVar; break;
         case VLVT_STRING: type = vpiStringVar; break;
-        default: break;
+        default: type = varp()->isBitVar() ? vpiBitVar : vpiReg; break;
         }
         if (isIndexedDimUnpacked())
             return vpiRegArray;

src/V3EmitCSyms.cpp

@@ -828,6 +828,8 @@ std::vector<std::string> EmitCSyms::getSymCtorStmts() {
             stmt += ", ";
             stmt += varp->vlEnumDir();  // VLVD_IN etc
             if (varp->dtypep()->skipRefp()->isSigned()) stmt += "|VLVF_SIGNED";
+            if (varp->dtypep()->skipRefp()->basicp()->keyword() == VBasicDTypeKwd::BIT)
+                stmt += "|VLVF_BITVAR";
             stmt += ", ";
             stmt += std::to_string(udim);
             stmt += ", ";

test_regress/t/t_vpi_var.cpp

@@ -419,6 +419,21 @@ int _mon_check_var() {
         CHECK_RESULT(d, vpiUndefined);
     }
 
+    // other unsigned types
+    constexpr struct {
+        const char* name;
+        PLI_INT32 exp_type;
+    } uint_vars[] = {
+        // uvm_hdl_polling.v requires single bits return vpiBitVar
+        {"bit1", vpiBitVar},
+    };
+    for (const auto& s : uint_vars) {
+        TestVpiHandle vh101 = VPI_HANDLE(s.name);
+        CHECK_RESULT_NZ(vh101);
+        d = vpi_get(vpiType, vh101);
+        CHECK_RESULT(d, s.exp_type);
+    }
+
     // other integer types
     tmpValue.format = vpiIntVal;
     constexpr struct {

test_regress/t/t_vpi_var.v

@@ -54,6 +54,7 @@ extern "C" int mon_check();
 
    integer        status;
 
+   bit            bit1           /*verilator public_flat_rw */;
    integer        integer1       /*verilator public_flat_rw */;
    byte           byte1          /*verilator public_flat_rw */;
    shortint       short1         /*verilator public_flat_rw */;
@@ -82,6 +83,7 @@ extern "C" int mon_check();
       text = "Verilog Test module";
       too_big = "some text";
 
+      bit1 = 1;
       integer1 = 123;
       byte1 = 123;
       short1 = 123;

test_regress/t/t_vpi_var2.v

@@ -73,6 +73,7 @@ extern "C" int mon_check();
    integer        status;
 
 /*verilator public_flat_rw_on*/
+   bit            bit1;
    integer        integer1;
    byte           byte1;
    shortint       short1;
@@ -99,6 +100,7 @@ extern "C" int mon_check();
       text = "Verilog Test module";
       too_big = "some text";
 
+      bit1 = 1;
       integer1 = 123;
       byte1 = 123;
       short1 = 123;

test_regress/t/t_vpi_var3.v

@@ -54,6 +54,7 @@ extern "C" int mon_check();
 
    integer        status;
 
+   bit            bit1;
    integer        integer1;
    byte           byte1;
    shortint       short1;
@@ -79,6 +80,7 @@ extern "C" int mon_check();
       text = "Verilog Test module";
       too_big = "some text";
 
+      bit1 = 1;
       integer1 = 123;
       byte1 = 123;
       short1 = 123;