From 329834538e262318f5cf599d9e98a748b9f6a8b9 Mon Sep 17 00:00:00 2001
From: Tanner Gooding <tagoo@outlook.com>
Date: Fri, 27 May 2022 08:59:18 -0700
Subject: [PATCH] Ensure `JIT_Dbl2ULng` correctly handles NaN

---
 src/coreclr/vm/jithelpers.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/coreclr/vm/jithelpers.cpp b/src/coreclr/vm/jithelpers.cpp
index 2c2d3b9a3048e..49d07f1206e92 100644
--- a/src/coreclr/vm/jithelpers.cpp
+++ b/src/coreclr/vm/jithelpers.cpp
@@ -595,10 +595,14 @@ HCIMPL1_V(UINT64, JIT_Dbl2ULng, double val)
     if (val < two63) {
         ret = FastDbl2Lng(val);
     }
-    else {
+    else if (!_isnan(val)) {
         // subtract 0x8000000000000000, do the convert then add it back again
         ret = FastDbl2Lng(val - two63) + I64(0x8000000000000000);
     }
+    else {
+        // specially handle NaN otherwise we return (Int64.MaxValue + 1)
+        ret = 0;
+    }
     return ret;
 }
 HCIMPLEND