From 55d78b225d4138b485018bf6a9d9bde0b0ef3c2d Mon Sep 17 00:00:00 2001
From: Geza Lore <glore@tenstorrent.com>
Date: Thu, 28 May 2026 18:34:36 +0100
Subject: [PATCH] Fix signing off new MULTIDRIVEN warnigns on variable (#7672)

---
 src/V3Undriven.cpp                            |  3 +-
 .../t/t_lint_always_ff_multidriven_bad.out    |  8 ++++++
 .../t/t_lint_always_ff_multidriven_bad.v      | 28 ++++++++++++++++++-
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/src/V3Undriven.cpp b/src/V3Undriven.cpp
index cca308d05..d4a2a1fd5 100644
--- a/src/V3Undriven.cpp
+++ b/src/V3Undriven.cpp
@@ -530,7 +530,8 @@ class UndrivenVisitor final : public VNVisitorConst {
                 if (entryp->isDrivenWhole() && !m_inBBox && !VN_IS(nodep, VarXRef)
                     && !VN_IS(nodep->dtypep()->skipRefp(), UnpackArrayDType) && !sameFileLine
                     && !entryp->isUnderGen() && otherWritep && !entryp->isFtaskDriven()
-                    && !ftaskDef) {
+                    && !ftaskDef
+                    && !nodep->varp()->fileline()->warnIsOff(V3ErrorCode::MULTIDRIVEN)) {
                     const bool otherWriteIsStaticInit
                         = nodep->varp()->hasUserInit() && otherWritep == entryp->initStaticp();
 
diff --git a/test_regress/t/t_lint_always_ff_multidriven_bad.out b/test_regress/t/t_lint_always_ff_multidriven_bad.out
index 7486d44ec..fa7b14b1d 100644
--- a/test_regress/t/t_lint_always_ff_multidriven_bad.out
+++ b/test_regress/t/t_lint_always_ff_multidriven_bad.out
@@ -16,4 +16,12 @@
                       t/t_lint_always_ff_multidriven_bad.v:20:5: ... Location of always_ff write
    20 |     b <= 1'b1;
       |     ^
+%Warning-MULTIDRIVEN: t/t_lint_always_ff_multidriven_bad.v:34:7: Variable written to in always_ff also written by other process (IEEE 1800-2023 9.2.2.4): 'q'
+                                                               : ... note: In instance 't'
+                      t/t_lint_always_ff_multidriven_bad.v:34:7: 
+   34 |       q[i][1] <= a;  
+      |       ^
+                      t/t_lint_always_ff_multidriven_bad.v:29:7: ... Location of other write
+   29 |       q[i][0] <= a;  
+      |       ^
 %Error: Exiting due to
diff --git a/test_regress/t/t_lint_always_ff_multidriven_bad.v b/test_regress/t/t_lint_always_ff_multidriven_bad.v
index ae435f716..ddc2f6034 100644
--- a/test_regress/t/t_lint_always_ff_multidriven_bad.v
+++ b/test_regress/t/t_lint_always_ff_multidriven_bad.v
@@ -4,7 +4,7 @@
 // SPDX-FileCopyrightText: 2026 Zhi QU
 // SPDX-License-Identifier: CC0-1.0
 
-module t;
+module t(input wire clk);
 
   logic a;
 
@@ -22,4 +22,30 @@ module t;
 
   initial b = 1'b0;  // <--- Warning
 
+  reg [1:0][1:0] q;
+
+  always_ff @(posedge clk) begin
+    for (int i = 0 ; i < 2 ; ++i)
+      q[i][0] <= a; // <--- Warning
+  end
+
+  always_ff @(posedge clk) begin
+    for (int i = 0 ; i < 2 ; ++i)
+      q[i][1] <= a; // <--- Warning
+  end
+
+  /* verilator lint_off MULTIDRIVEN */
+  reg [1:0][1:0] q2;
+  /* verilator lint_on MULTIDRIVEN */
+
+  always_ff @(posedge clk) begin
+    for (int i = 0 ; i < 2 ; ++i)
+      q2[i][0] <= a; // <--- NO Warning
+  end
+
+  always_ff @(posedge clk) begin
+    for (int i = 0 ; i < 2 ; ++i)
+      q2[i][1] <= a; // <--- NO Warning
+  end
+
 endmodule