Fix finding single DPI exports from other scopes

include/verilated.cpp

@@ -3464,11 +3464,10 @@ void Verilated::mkdir(const char* dirname) VL_MT_UNSAFE {
 
 void Verilated::quiesce() VL_MT_SAFE {
     // Wait until all threads under this evaluation are quiet
-    // THREADED-TODO
 }
 
 int Verilated::exportFuncNum(const char* namep) VL_MT_SAFE {
-    return VerilatedImp::exportFind(namep);
+    return VerilatedImp::exportFindNum(namep);
 }
 
 void Verilated::endOfThreadMTaskGuts(VerilatedEvalMsgQueue* evalMsgQp) VL_MT_SAFE {
@@ -3573,7 +3572,7 @@ VerilatedScope::~VerilatedScope() {
 void VerilatedScope::exportInsert(int finalize, const char* namep, void* cb) VL_MT_UNSAFE {
     // Slowpath - called once/scope*export at construction
     // Insert a exported function into scope table
-    const int funcnum = VerilatedImp::exportInsert(namep);
+    const int funcnum = VerilatedImp::exportInsert(namep, cb);
     if (!finalize) {
         // Need two passes so we know array size to create
         // Alternative is to dynamically stretch the array, which is more code, and slower.
@@ -3630,6 +3629,25 @@ VerilatedVar* VerilatedScope::varFind(const char* namep) const VL_MT_SAFE_POSTIN
     return nullptr;
 }
 
+void* VerilatedScope::exportFind(const VerilatedScope* scopep, int funcnum) VL_MT_SAFE {
+    if (VL_UNLIKELY(!scopep)) return exportFindNullError(funcnum);
+    // If function is registered only once across all scopes, fast path it.
+    // UVM for example expects to find uvm_polling_value_change_notify
+    // from a different scope than where decared.
+    VL_DEBUG_IFDEF(assert(funcnum < VerilatedImp::exportFlatCbs().size()););
+    {
+        void* const cbp = VerilatedImp::exportFlatCbs()[funcnum];
+        if (VL_LIKELY(cbp)) return cbp;
+    }
+    // Else specific scope-based export call
+    if (VL_LIKELY(funcnum < scopep->m_funcnumMax)) {
+        // m_callbacksp must be declared, as Max'es are > 0
+        void* const cbp = scopep->m_callbacksp[funcnum];
+        if (VL_LIKELY(cbp)) return cbp;
+    }
+    return scopep->exportFindError(funcnum);  // LCOV_EXCL_LINE
+}
+
 void* VerilatedScope::exportFindNullError(int funcnum) VL_MT_SAFE {
     // Slowpath - Called only when find has failed
     const std::string msg = ("Testbench C called '"s + VerilatedImp::exportName(funcnum)

include/verilated.h

@@ -744,15 +744,7 @@ public:  // But internals only - called from verilated modules, VerilatedSyms
     void scopeDump() const;
     void* exportFindError(int funcnum) const VL_MT_SAFE;
     static void* exportFindNullError(int funcnum) VL_MT_SAFE;
-    static void* exportFind(const VerilatedScope* scopep, int funcnum) VL_MT_SAFE {
-        if (VL_UNLIKELY(!scopep)) return exportFindNullError(funcnum);
-        if (VL_LIKELY(funcnum < scopep->m_funcnumMax)) {
-            // m_callbacksp must be declared, as Max'es are > 0
-            return scopep->m_callbacksp[funcnum];
-        } else {  // LCOV_EXCL_LINE
-            return scopep->exportFindError(funcnum);  // LCOV_EXCL_LINE
-        }
-    }
+    static void* exportFind(const VerilatedScope* scopep, int funcnum) VL_MT_SAFE;
     Type type() const { return m_type; }
 };
 

include/verilated_imp.h

@@ -433,6 +433,10 @@ protected:
     ExportNameMap m_exportMap VL_GUARDED_BY(m_exportMutex);
     int m_exportNext VL_GUARDED_BY(m_exportMutex) = 0;  // Next export funcnum
 
+    // No guard, as init-time loaded
+    std::vector<void*> m_exportFlatCbs;  // Exports when only single scope registered
+    std::vector<bool> m_exportFlatMulti;  // Multiple scopes registerd; cannot use m_exportScopes
+
     // CONSTRUCTORS
     VerilatedImpData() = default;
 };
@@ -542,8 +546,8 @@ public:
     // in the design that also happen to have our same callback function.
     // Rather than a 2D map, the integer scheme saves 500ish ns on a likely
     // miss at the cost of a multiply, and all lookups move to slowpath.
-    static int exportInsert(const char* namep) VL_MT_SAFE {
-        // Slow ok - called once/function at creation
+private:
+    static int exportInsertName(const char* namep) VL_MT_SAFE {
         const VerilatedLockGuard lock{s().m_exportMutex};
         const auto it = s().m_exportMap.find(namep);
         if (it == s().m_exportMap.end()) {
@@ -553,15 +557,37 @@ public:
             return it->second;
         }
     }
-    static int exportFind(const char* namep) VL_MT_SAFE {
+
+public:
+    static int exportInsert(const char* namep, void* cb) VL_MT_SAFE {
+        const int funcnum = VerilatedImp::exportInsertName(namep);
+        const VerilatedLockGuard lock{s().m_exportMutex};
+        // Slow ok - called once/function at creation
+        if (funcnum >= s().m_exportFlatCbs.size()) {
+            s().m_exportFlatCbs.resize(funcnum + 1);
+            s().m_exportFlatMulti.resize(funcnum + 1);
+        }
+        if (!s().m_exportFlatMulti[funcnum]) {
+            if (s().m_exportFlatCbs[funcnum] == cb) {  // Duplicate
+            } else if (!s().m_exportFlatCbs[funcnum]) {  // First
+                s().m_exportFlatCbs[funcnum] = cb;
+            } else {  // Multiple registrants
+                s().m_exportFlatCbs[funcnum] = nullptr;
+                s().m_exportFlatMulti[funcnum] = true;
+            }
+        }
+        return funcnum;
+    }
+    static int exportFindNum(const char* namep) VL_MT_SAFE {
         const VerilatedLockGuard lock{s().m_exportMutex};
         const auto& it = s().m_exportMap.find(namep);
         if (VL_LIKELY(it != s().m_exportMap.end())) return it->second;
-        const std::string msg = ("%Error: Testbench C called "s + namep
-                                 + " but no such DPI export function name exists in ANY model");
+        const std::string msg = "%Error: Testbench C called "s + namep
+                                + " but no such DPI export function name exists in ANY model";
         VL_FATAL_MT("unknown", 0, "", msg.c_str());
         return -1;
     }
+    static const std::vector<void*>& exportFlatCbs() VL_MT_SAFE { return s().m_exportFlatCbs; }
     static const char* exportName(int funcnum) VL_MT_SAFE {
         // Slowpath; find name for given export; errors only so no map to reverse-map it
         const VerilatedLockGuard lock{s().m_exportMutex};

test_regress/t/t_dpi_export_scope_bad.v

@@ -7,15 +7,23 @@
 // SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
 
 module t;
-   s s();
+  s s ();
+  other other ();
 
-   import "DPI-C" context function void dpix_run_tests();
-   initial dpix_run_tests();
+  import "DPI-C" context function void dpix_run_tests();
+  initial dpix_run_tests();
 endmodule
 
 module s;
-   export "DPI-C" task dpix_task;
-   task dpix_task();
-      $write("Hello in %m\n");
-   endtask
+  export "DPI-C" task dpix_task;
+  task dpix_task();
+    $write("Hello in %m\n");
+  endtask
+endmodule
+
+module other;
+  export "DPI-C" task dpix_task;
+  task dpix_task();
+    $write("Hello in %m\n");
+  endtask
 endmodule

test_regress/t/t_dpi_export_scope_flat.cpp

@@ -0,0 +1,25 @@
+// -*- mode: C++; c-file-style: "cc-mode" -*-
+//
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain.
+// SPDX-FileCopyrightText: 2010 Wilson Snyder
+// SPDX-License-Identifier: CC0-1.0
+
+#include <verilated.h>
+
+//======================================================================
+
+#include "Vt_dpi_export_scope_flat__Dpi.h"
+
+#ifdef NEED_EXTERNS
+extern "C" {
+extern void dpix_task();
+}
+#endif
+
+//======================================================================
+
+void dpix_run_tests() {
+    dpix_task();  // Wrong scope
+}

test_regress/t/t_dpi_export_scope_flat.py

@@ -0,0 +1,18 @@
+#!/usr/bin/env python3
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# This program is free software; you can redistribute it and/or modify it
+# under the terms of either the GNU Lesser General Public License Version 3
+# or the Perl Artistic License Version 2.0.
+# SPDX-FileCopyrightText: 2024 Wilson Snyder
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('simulator')
+
+test.compile(v_flags2=["--binary", test.pli_filename])
+
+test.execute()
+
+test.passes()

test_regress/t/t_dpi_export_scope_flat.v

@@ -0,0 +1,21 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This program is free software; you can redistribute it and/or modify it
+// under the terms of either the GNU Lesser General Public License Version 3
+// or the Perl Artistic License Version 2.0.
+// SPDX-FileCopyrightText: 2020 Wilson Snyder
+// SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+module t;
+  s s ();
+
+  import "DPI-C" context function void dpix_run_tests();
+  initial dpix_run_tests();
+endmodule
+
+module s;
+  export "DPI-C" task dpix_task;
+  task dpix_task();
+    $write("Hello in %m\n");
+  endtask
+endmodule