Support DPI imports and exports with double underscores.

Changes

@@ -27,6 +27,7 @@ Verilator 5.029 devel
 * Support named event locals (#5422). [Krzysztof Bieganski, Antmicro Ltd.]
 * Support basic dist constraints (#5431). [Arkadiusz Kozdra, Antmicro Ltd.]
 * Support inside array constraints (#5448). [Arkadiusz Kozdra, Antmicro Ltd.]
+* Support DPI imports and exports with double underscores.
 * Add error on instances without parenthesis.
 * Add partial coverage symbol and branch data in lcov info files (#5388). [Andrew Nolte]
 * Add method to check if there are VPI callbacks of the given type (#5399). [Kaleb Barrett]

src/V3Task.cpp

@@ -723,6 +723,14 @@ class TaskVisitor final : public VNVisitor {
         return dpiproto;
     }
 
+    static void checkLegalCIdentifier(AstNode* nodep, const string& name) {
+        if (name.end() != std::find_if(name.begin(), name.end(), [](char c) {
+                return !std::isalnum(c) && c != '_';
+            })) {
+            nodep->v3error("DPI function has illegal characters in C identifier name: " << name);
+        }
+    }
+
     static AstNode* createDpiTemp(AstVar* portp, const string& suffix) {
         const string stmt = portp->dpiTmpVarType(portp->name() + suffix) + ";\n";
         return new AstCStmt{portp->fileline(), stmt};
@@ -822,8 +830,11 @@ class TaskVisitor final : public VNVisitor {
     }
 
     AstCFunc* makeDpiExportDispatcher(AstNodeFTask* nodep, AstVar* rtnvarp) {
+        // Verilog name has __ conversion and other tricks, to match DPI C code, back that out
+        const string name = AstNode::prettyName(nodep->cname());
+        checkLegalCIdentifier(nodep, name);
         const char* const tmpSuffixp = V3Task::dpiTemporaryVarSuffix();
-        AstCFunc* const funcp = new AstCFunc{nodep->fileline(), nodep->cname(), m_scopep,
+        AstCFunc* const funcp = new AstCFunc{nodep->fileline(), name, m_scopep,
                                              (rtnvarp ? rtnvarp->dpiArgType(true, true) : "")};
         funcp->dpiExportDispatcher(true);
         funcp->dpiContext(nodep->dpiContext());
@@ -831,7 +842,7 @@ class TaskVisitor final : public VNVisitor {
         funcp->entryPoint(true);
         funcp->isStatic(true);
         funcp->protect(false);
-        funcp->cname(nodep->cname());
+        funcp->cname(name);
         // Add DPI Export to top, since it's a global function
         m_topScopep->scopep()->addBlocksp(funcp);
 
@@ -949,15 +960,14 @@ class TaskVisitor final : public VNVisitor {
     }
 
     AstCFunc* makeDpiImportPrototype(AstNodeFTask* nodep, AstVar* rtnvarp) {
-        if (nodep->cname() != AstNode::prettyName(nodep->cname())) {
-            nodep->v3error("DPI function has illegal characters in C identifier name: "
-                           << AstNode::prettyNameQ(nodep->cname()));
-        }
+        // Verilog name has __ conversion and other tricks, to match DPI C code, back that out
+        const string name = AstNode::prettyName(nodep->cname());
+        checkLegalCIdentifier(nodep, name);
         // Tasks (but not void functions) return a boolean 'int' indicating disabled
         const string rtnType = rtnvarp            ? rtnvarp->dpiArgType(true, true)
                                : nodep->dpiTask() ? "int"
                                                   : "";
-        AstCFunc* const funcp = new AstCFunc{nodep->fileline(), nodep->cname(), m_scopep, rtnType};
+        AstCFunc* const funcp = new AstCFunc{nodep->fileline(), name, m_scopep, rtnType};
         funcp->dpiContext(nodep->dpiContext());
         funcp->dpiImportPrototype(true);
         funcp->dontCombine(true);

test_regress/t/t_dpi_export.v

@@ -66,6 +66,9 @@ module t;
 `endif
    task dpix_t_time(input time i, output time o);  o = ~i; endtask
 
+   export "DPI-C" function dpix__under___score;
+   function int dpix__under___score(input int i);  return i + 1; endfunction
+
    int lineno;
 
    initial begin

test_regress/t/t_dpi_export_c.cpp

@@ -59,6 +59,8 @@ extern void dpix_t_reg15(const svLogicVecVal* i, svLogicVecVal* o);
 extern void dpix_t_reg95(const svLogicVecVal* i, svLogicVecVal* o);
 extern void dpix_t_integer(const svLogicVecVal* i, svLogicVecVal* o);
 extern void dpix_t_time(const svLogicVecVal* i, svLogicVecVal* o);
+
+extern int dpix__under___score(int i);
 }
 
 #endif
@@ -225,6 +227,8 @@ int dpix_run_tests() {
     }
 #endif
 
+    CHECK_RESULT(int, dpix__under___score(77), 78);
+
     if (int bad = check_sub("top.t.a", 1)) return bad;
     if (int bad = check_sub("top.t.b", 2)) return bad;
 

test_regress/t/t_dpi_import.v

@@ -99,6 +99,9 @@ module t (/*AUTOARG*/
    import "DPI-C" dpii_fa_bit =  function int oth_f_int1(input int i);
    import "DPI-C" dpii_fa_bit =  function int oth_f_int2(input int i);
 
+   // Check Verilator doesn't convert double underscores
+   import "DPI-C" pure function int dpii__under___score(input int i);
+
    bit          i_b,    o_b;
    bit [7:0]    i_b8;
    bit [8:0]    i_b9;
@@ -256,6 +259,8 @@ module t (/*AUTOARG*/
       if (oth_f_int1(32'd123) !== ~32'd123) $stop;
       if (oth_f_int2(32'd124) !== ~32'd124) $stop;
 
+      if (dpii__under___score(32'd60) != 32'd61) $stop;
+
       $write("*-* All Finished *-*\n");
       $finish;
    end

test_regress/t/t_dpi_import_c.cpp

@@ -183,6 +183,8 @@ void dpii_v_bit96(const svBitVecVal* i, svBitVecVal* o) {
 
 int dpii_f_strlen(const char* i) { return strlen(i); }
 
+int dpii__under___score(int i) { return i + 1; }
+
 //======================================================================
 
 void dpii_f_void() {}

test_regress/t/t_dpi_name_bad.out

@@ -1,4 +1,7 @@
-%Error: t/t_dpi_name_bad.v:12:32: DPI function has illegal characters in C identifier name: 'badly.named'
-   12 |    import "DPI-C" function int \badly.named (int i);
+%Error: t/t_dpi_name_bad.v:11:32: DPI function has illegal characters in C identifier name: badly.named
+   11 |    import "DPI-C" function int \badly.named (int i);
       |                                ^~~~~~~~~~~~
+%Error: t/t_dpi_name_bad.v:14:17: DPI function has illegal characters in C identifier name: badly.expt
+   14 |    function int \badly.expt ; return 0; endfunction
+      |                 ^~~~~~~~~~~
 %Error: Exiting due to

test_regress/t/t_dpi_name_bad.v

@@ -8,9 +8,11 @@
 
 module t ();
 
-   // Can't handle logic (yet?)
    import "DPI-C" function int \badly.named (int i);
 
+   export "DPI-C" function \badly.expt ;
+   function int \badly.expt ; return 0; endfunction
+
    initial begin
       $stop;
    end