Support structure initial values (#6130).

Fixes #6130.

Changes

@@ -18,6 +18,7 @@ Verilator 5.045 devel
 * Add parsing of solve-before inside foreach (#6934). [Pawel Kojma, Antmicro Ltd.]
 * Add error when accessing a non-static class field from a static function (#6948). [Artur Bieniek, Antmicro Ltd.]
 * Add VerilatedContext::useNumaAssign and set on threads() call (#6954). [Yangyu Chen]
+* Support structure initial values (#6130).
 * Support vpi_put/vpi_get forcing of signals (#5933) (#6704). [Christian Hecken]
 * Support detailed failure info for constraint violations (#6617) (#6883). [Yilou Wang]
 * Support `unique` constraints (on 1D static arrays) (#6810) (#6878). [Srinivasan Venkataramanan]

src/V3EmitCFunc.cpp

@@ -542,6 +542,8 @@ void EmitCFunc::emitVarReset(AstVar* varp, bool constructing) {
         // If an ARRAYINIT we initialize it using an initial block similar to a signal
         // puts("// parameter "+varp->nameProtect()+" = "+varp->valuep()->name()+"\n");
     } else if (const AstInitArray* const initarp = VN_CAST(varp->valuep(), InitArray)) {
+        // TODO this code probably better handled as initp argument to emitVarResetRecurse
+        // TODO merge this functionality with V3EmitCConstInit.h visitors
         if (VN_IS(dtypep, AssocArrayDType)) {
             if (initarp->defaultp()) {
                 emitSetVarConstant(varNameProtected + ".atDefault()",
@@ -583,13 +585,14 @@ void EmitCFunc::emitVarReset(AstVar* varp, bool constructing) {
             varp->v3fatalSrc("InitArray under non-arrayed var");
         }
     } else {
-        putns(varp, emitVarResetRecurse(varp, constructing, varNameProtected, dtypep, 0, ""));
+        putns(varp, emitVarResetRecurse(varp, constructing, varNameProtected, dtypep, 0, "",
+                                        varp->valuep()));
     }
 }
 
 string EmitCFunc::emitVarResetRecurse(const AstVar* varp, bool constructing,
                                       const string& varNameProtected, AstNodeDType* dtypep,
-                                      int depth, const string& suffix) {
+                                      int depth, const string& suffix, const AstNode* valuep) {
     dtypep = dtypep->skipRefp();
     AstBasicDType* const basicp = dtypep->basicp();
     // Returns string to do resetting, empty to do nothing (which caller should handle)
@@ -599,14 +602,14 @@ string EmitCFunc::emitVarResetRecurse(const AstVar* varp, bool constructing,
         const string pre = constructing ? "" : varNameProtected + suffix + ".clear();\n";
         return pre
                + emitVarResetRecurse(varp, constructing, varNameProtected, adtypep->subDTypep(),
-                                     depth + 1, suffix + ".atDefault()" + cvtarray);
+                                     depth + 1, suffix + ".atDefault()" + cvtarray, nullptr);
     } else if (AstWildcardArrayDType* const adtypep = VN_CAST(dtypep, WildcardArrayDType)) {
         // Access std::array as C array
         const string cvtarray = (adtypep->subDTypep()->isWide() ? ".data()" : "");
         const string pre = constructing ? "" : varNameProtected + suffix + ".clear();\n";
         return pre
                + emitVarResetRecurse(varp, constructing, varNameProtected, adtypep->subDTypep(),
-                                     depth + 1, suffix + ".atDefault()" + cvtarray);
+                                     depth + 1, suffix + ".atDefault()" + cvtarray, nullptr);
     } else if (VN_IS(dtypep, CDType)) {
         return "";  // Constructor does it
     } else if (VN_IS(dtypep, ClassRefDType)) {
@@ -619,14 +622,14 @@ string EmitCFunc::emitVarResetRecurse(const AstVar* varp, bool constructing,
         const string pre = constructing ? "" : varNameProtected + suffix + ".clear();\n";
         return pre
                + emitVarResetRecurse(varp, constructing, varNameProtected, adtypep->subDTypep(),
-                                     depth + 1, suffix + ".atDefault()" + cvtarray);
+                                     depth + 1, suffix + ".atDefault()" + cvtarray, nullptr);
     } else if (const AstQueueDType* const adtypep = VN_CAST(dtypep, QueueDType)) {
         // Access std::array as C array
         const string cvtarray = (adtypep->subDTypep()->isWide() ? ".data()" : "");
         const string pre = constructing ? "" : varNameProtected + suffix + ".clear();\n";
         return pre
                + emitVarResetRecurse(varp, constructing, varNameProtected, adtypep->subDTypep(),
-                                     depth + 1, suffix + ".atDefault()" + cvtarray);
+                                     depth + 1, suffix + ".atDefault()" + cvtarray, nullptr);
     } else if (VN_IS(dtypep, SampleQueueDType)) {
         return "";
     } else if (const AstUnpackArrayDType* const adtypep = VN_CAST(dtypep, UnpackArrayDType)) {
@@ -637,17 +640,17 @@ string EmitCFunc::emitVarResetRecurse(const AstVar* varp, bool constructing,
                             + cvtToStr(adtypep->elementsConst()) + "; ++" + ivar + ") {\n");
         const string below
             = emitVarResetRecurse(varp, constructing, varNameProtected, adtypep->subDTypep(),
-                                  depth + 1, suffix + "[" + ivar + "]");
+                                  depth + 1, suffix + "[" + ivar + "]", nullptr);
         const string post = "}\n";
         return below.empty() ? "" : pre + below + post;
     } else if (VN_IS(dtypep, NodeUOrStructDType) && !VN_AS(dtypep, NodeUOrStructDType)->packed()) {
-        const auto* const sdtypep = VN_AS(dtypep, NodeUOrStructDType);
+        const AstNodeUOrStructDType* const sdtypep = VN_AS(dtypep, NodeUOrStructDType);
         string literal;
         for (const AstMemberDType* itemp = sdtypep->membersp(); itemp;
              itemp = VN_AS(itemp->nextp(), MemberDType)) {
             const std::string line = emitVarResetRecurse(
                 varp, constructing, varNameProtected + suffix + "." + itemp->nameProtect(),
-                itemp->dtypep(), depth + 1, "");
+                itemp->dtypep(), depth + 1, "", itemp->valuep());
             if (!line.empty()) literal += line;
         }
         return literal;
@@ -682,10 +685,10 @@ string EmitCFunc::emitVarResetRecurse(const AstVar* varp, bool constructing,
         splitSizeInc(1);
         if (dtypep->isWide()) {  // Handle unpacked; not basicp->isWide
             string out;
-            if (varp->valuep()) {
+            if (valuep) {
-                const AstConst* const constp = VN_AS(varp->valuep(), Const);
+                const AstConst* const constp = VN_AS(valuep, Const);
                 UASSERT_OBJ(constp, varp, "non-const initializer for variable");
-                for (int w = 0; w < varp->widthWords(); ++w) {
+                for (int w = 0; w < dtypep->widthWords(); ++w) {
                     out += varNameProtected + suffix + "[" + cvtToStr(w) + "] = ";
                     out += cvtToStr(constp->num().edataWord(w)) + "U;\n";
                 }
@@ -709,7 +712,15 @@ string EmitCFunc::emitVarResetRecurse(const AstVar* varp, bool constructing,
             return out;
         } else {
             string out = varNameProtected + suffix;
-            if (zeroit) {
+            if (valuep) {
+                out += " = ";
+                // TODO cleanup code shared between here, V3EmitCConstInit.h,
+                // EmitCFunc::emitVarReset, EmitCFunc::emitConstant
+                const AstConst* const constp = VN_AS(valuep, Const);
+                UASSERT_OBJ(constp, varp, "non-const initializer for variable");
+                out += cvtToStr(constp->num().edataWord(0)) + "U;\n";
+                out += ";\n";
+            } else if (zeroit) {
                 out += " = 0;\n";
             } else {
                 emitVarResetScopeHash();

src/V3EmitCFunc.h

@@ -215,7 +215,7 @@ public:
     void emitVarReset(AstVar* varp, bool constructing);
     string emitVarResetRecurse(const AstVar* varp, bool constructing,
                                const string& varNameProtected, AstNodeDType* dtypep, int depth,
-                               const string& suffix);
+                               const string& suffix, const AstNode* valuep);
     void emitVarResetScopeHash();
     void emitChangeDet();
     void emitConstInit(AstNode* initp) { iterateConst(initp); }

src/V3Width.cpp

@@ -3270,10 +3270,6 @@ class WidthVisitor final : public VNVisitor {
                 itemp->v3error("Initial values not allowed in packed struct/union"
                                " (IEEE 1800-2023 7.2.2)");
                 pushDeletep(itemp->valuep()->unlinkFrBack());
-            } else if (itemp->valuep()) {
-                itemp->valuep()->v3warn(E_UNSUPPORTED,
-                                        "Unsupported: Initial values in struct/union members");
-                pushDeletep(itemp->valuep()->unlinkFrBack());
             }
         }
         const bool isHardPackedUnion
@@ -5146,6 +5142,11 @@ class WidthVisitor final : public VNVisitor {
             // default_value for any unmatched member yet
             return defaultp->cloneTree(false);
         }
+        if (memp->valuep()) {
+            return new AstPatMember{nodep->fileline(),
+                                    VN_AS(memp->valuep()->cloneTree(false), NodeExpr),
+                                    new AstText{nodep->fileline(), memp->name()}, nullptr};
+        }
         if (!VN_IS(memp_vdtypep, UnionDType)) {
             nodep->v3error("Assignment pattern missed initializing elements: "
                            << memp->virtRefDTypep()->prettyDTypeNameQ() << " "

test_regress/t/t_struct_unpacked_init.out

@@ -1,6 +0,0 @@
-%Error-UNSUPPORTED: t/t_struct_unpacked_init.v:12:24: Unsupported: Initial values in struct/union members
-                                                    : ... note: In instance 't'
-   12 |       bit [3:0] m_lo = P;
-      |                        ^
-                    ... For error description see https://verilator.org/warn/UNSUPPORTED?v=latest
-%Error: Exiting due to

test_regress/t/t_struct_unpacked_init.py

@@ -4,13 +4,15 @@
 # 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-FileCopyrightText: 2026 Wilson Snyder
 # SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
 
 import vltest_bootstrap
 
-test.scenarios('linter')
+test.scenarios('simulator')
 
-test.lint(fails=True, expect_filename=test.golden_filename)
+test.compile()
+
+test.execute()
 
 test.passes()

test_regress/t/t_struct_unpacked_init.v

@@ -1,25 +1,40 @@
 // DESCRIPTION: Verilator: Verilog Test module
 //
 // This file ONLY is placed under the Creative Commons Public Domain.
-// SPDX-FileCopyrightText: 2023 Wilson Snyder
+// SPDX-FileCopyrightText: 2026 Wilson Snyder
 // SPDX-License-Identifier: CC0-1.0
 
+// verilog_format: off
+`define stop $stop
+`define checkh(gotv, expv) do if ((gotv) !== (expv)) begin $write("%%Error: %s:%0d:  got='h%x exp='h%x\n", `__FILE__,`__LINE__, (gotv), (expv)); `stop; end while(0);
+// verilog_format: on
+
 module t;
 
-   parameter P = 4'h5;
+  parameter P = 4'h5;
 
-   struct {  // Can't legally be packed
+  typedef struct {  // Must be unpacked -- existing error check
-      bit [3:0] m_lo = P;
+    // Update ctor_var_reset to check instead of making a constructor
-      bit [3:0] m_hi;
+    bit [3:0] m_lo = P;
-   } s;
+    bit [93:0] m_mid = '1;  // Wide
+    bit [3:0] m_hi;
+  } s_t;
+  s_t s;
 
-   initial begin
+  initial begin
-      s.m_hi = 4'ha;
+    $display("%p", s);
-      if (s.m_lo != 4'h5) $stop;
+    `checkh(s.m_lo, 4'h5);
-      if (s.m_hi != 4'ha) $stop;
+    `checkh(s.m_mid, ~94'h0);
+    `checkh(s.m_hi, 4'h0);
+    s.m_mid = 94'ha;
+    s.m_hi = 4'hb;
+    $display("%p", s);
+    `checkh(s.m_lo, 4'h5);
+    `checkh(s.m_mid, 94'ha);
+    `checkh(s.m_hi, 4'hb);
 
-      $write("*-* All Finished *-*\n");
+    $write("*-* All Finished *-*\n");
-      $finish;
+    $finish;
-   end
+  end
 
 endmodule

test_regress/t/t_struct_unpacked_init_param.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: 2026 Wilson Snyder
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+import vltest_bootstrap
+
+test.scenarios('simulator')
+
+test.compile()
+
+test.execute()
+
+test.passes()

test_regress/t/t_struct_unpacked_init_param.v

@@ -0,0 +1,38 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain.
+// SPDX-FileCopyrightText: 2026 Wilson Snyder
+// SPDX-License-Identifier: CC0-1.0
+
+// verilog_format: off
+`define stop $stop
+`define checkh(gotv, expv) do if ((gotv) !== (expv)) begin $write("%%Error: %s:%0d:  got='h%x exp='h%x\n", `__FILE__,`__LINE__, (gotv), (expv)); `stop; end while(0);
+// verilog_format: on
+
+module t;
+
+  parameter P = 4'h5;
+
+  typedef struct {  // Must be unpacked -- existing error check
+    bit [3:0] m_lo = P;
+    bit [93:0] m_mid = '1;  // Wide
+    bit [3:0] m_hi;
+  } s_t;
+
+  localparam s_t S = '{m_hi: 6};  // Not setting m_mid/m_hi
+
+  localparam S_LO = S.m_lo;
+  localparam S_HI = S.m_hi;
+
+  initial begin
+    `checkh(S.m_hi, 4'h6);
+    `checkh(S_HI, 4'h6);
+
+    `checkh(S.m_lo, 4'h5);
+    `checkh(S_LO, 4'h5);
+
+    $write("*-* All Finished *-*\n");
+    $finish;
+  end
+
+endmodule