From d896f1ff081af7653086e9806d90842441a441c1 Mon Sep 17 00:00:00 2001
From: Krzysztof Bieganski <kbieganski@antmicro.com>
Date: Wed, 28 Aug 2024 17:29:12 +0200
Subject: [PATCH] Fix queue `[$-i]` select as reference argument (#5411)

Signed-off-by: Krzysztof Bieganski <kbieganski@antmicro.com>
---
 src/V3Task.cpp                | 2 +-
 src/V3Width.cpp               | 5 +++--
 test_regress/t/t_queue_back.v | 7 ++++++-
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/V3Task.cpp b/src/V3Task.cpp
index ae8a6373b..a743b33b5 100644
--- a/src/V3Task.cpp
+++ b/src/V3Task.cpp
@@ -493,7 +493,7 @@ class TaskVisitor final : public VNVisitor {
                     || VN_IS(pinp, ArraySel)) {
                     refArgOk = true;
                 } else if (const AstCMethodHard* const cMethodp = VN_CAST(pinp, CMethodHard)) {
-                    refArgOk = cMethodp->name() == "at";
+                    refArgOk = cMethodp->name() == "at" || cMethodp->name() == "atBack";
                 }
                 if (refArgOk) {
                     if (AstVarRef* const varrefp = VN_CAST(pinp, VarRef)) {
diff --git a/src/V3Width.cpp b/src/V3Width.cpp
index a2b7b398d..3d5ec00a1 100644
--- a/src/V3Width.cpp
+++ b/src/V3Width.cpp
@@ -3677,10 +3677,11 @@ class WidthVisitor final : public VNVisitor {
     }
     void methodCallQueue(AstMethodCall* nodep, AstQueueDType* adtypep) {
         AstCMethodHard* newp = nullptr;
-        if (nodep->name() == "at") {  // Created internally for []
+        if (nodep->name() == "at" || nodep->name() == "atBack") {  // Created internally for []
             methodOkArguments(nodep, 1, 1);
             methodCallLValueRecurse(nodep, nodep->fromp(), VAccess::WRITE);
-            newp = new AstCMethodHard{nodep->fileline(), nodep->fromp()->unlinkFrBack(), "at"};
+            newp = new AstCMethodHard{nodep->fileline(), nodep->fromp()->unlinkFrBack(),
+                                      nodep->name()};
             newp->dtypeFrom(adtypep->subDTypep());
         } else if (nodep->name() == "num"  // function int num()
                    || nodep->name() == "size") {
diff --git a/test_regress/t/t_queue_back.v b/test_regress/t/t_queue_back.v
index 1d8d2bb90..1c33b73ec 100644
--- a/test_regress/t/t_queue_back.v
+++ b/test_regress/t/t_queue_back.v
@@ -9,8 +9,13 @@ module t(/*AUTOARG*/);
    int q[$];
    int r;
 
+   function void set_val(ref int lhs, input int rhs);
+      lhs = rhs;
+   endfunction
+
    initial begin
-      q = { 20, 30, 40 };
+      q = { 20, 50, 40 };
+      set_val(q[$-1], 30);
 
       r = q[$];
       if (r != 40) $stop;