From 11248295008f1199a3cdd8b8a0180e3cf8f2adcf Mon Sep 17 00:00:00 2001
From: Nandu Raj <nndurj@gmail.com>
Date: Tue, 22 Dec 2020 18:22:38 +0530
Subject: [PATCH] Fix $urandom_range maximum value (#2723)

---
 docs/CONTRIBUTORS          |  1 +
 include/verilated.h        |  4 ++--
 test_regress/t/t_urandom.v | 11 +++++++----
 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/docs/CONTRIBUTORS b/docs/CONTRIBUTORS
index a64dce238..363676c91 100644
--- a/docs/CONTRIBUTORS
+++ b/docs/CONTRIBUTORS
@@ -49,6 +49,7 @@ Marshal Qiao
 Matthew Ballance
 Michael Killough
 Mike Popoloski
+Nandu Raj
 Nathan Kohagen
 Nathan Myers
 Patrick Stewart
diff --git a/include/verilated.h b/include/verilated.h
index e30cdad53..e8872c333 100644
--- a/include/verilated.h
+++ b/include/verilated.h
@@ -661,9 +661,9 @@ inline IData VL_URANDOM_RANGE_I(IData hi, IData lo) {
     vluint64_t rnd = vl_rand64();
     if (VL_LIKELY(hi > lo)) {
         // Modulus isn't very fast but it's common that hi-low is power-of-two
-        return (rnd % (hi - lo)) + lo;
+        return (rnd % (hi - lo + 1)) + lo;
     } else {
-        return (rnd % (lo - hi)) + hi;
+        return (rnd % (lo - hi + 1)) + hi;
     }
 }
 
diff --git a/test_regress/t/t_urandom.v b/test_regress/t/t_urandom.v
index 885118ab7..fcb6b7b9d 100644
--- a/test_regress/t/t_urandom.v
+++ b/test_regress/t/t_urandom.v
@@ -34,14 +34,17 @@ module t(/*AUTOARG*/);
       if (v1 == v2 && v1 == v3) $stop;  // Possible, but 2^-64
 
       // Range
+      v2 = $urandom_range(v1, v1);
+      if (v1 != v2) $stop;
+
       for (int test = 0; test < 20; ++test) begin
          v1 = 2;
          v1 = $urandom_range(0, v1);
-         if (v1 != 0 && v1 != 1) $stop;
-         v1 = $urandom_range(2, 0);
-         if (v1 != 0 && v1 != 1) $stop;
-         v1 = $urandom_range(3);
          if (v1 != 0 && v1 != 1 && v1 != 2) $stop;
+         v1 = $urandom_range(2, 0);
+         if (v1 != 0 && v1 != 1 && v1 !=2) $stop;
+         v1 = $urandom_range(3);
+         if (v1 != 0 && v1 != 1 && v1 != 2 && v1 != 3) $stop;
       end
 
       // Seed stability