From ec7d772b196387e41d59a8bba3f14cd831dda467 Mon Sep 17 00:00:00 2001
From: ndossche <7771979+ndossche@users.noreply.github.com>
Date: Fri, 9 Oct 2026 21:49:59 +0200
Subject: [PATCH] Add regression test for GH-16821

---
 ext/opcache/tests/jit/gh16821.phpt | 63 ++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 ext/opcache/tests/jit/gh16821.phpt

diff --git a/ext/opcache/tests/jit/gh16821.phpt b/ext/opcache/tests/jit/gh16821.phpt
new file mode 100644
index 000000000000..5aacaeee41a3
--- /dev/null
+++ b/ext/opcache/tests/jit/gh16821.phpt
@@ -0,0 +1,63 @@
+--TEST--
+GH-16821 (Spill conflict between ASSIGN.op1_def and ASSIGN.op2_use)
+--EXTENSIONS--
+opcache
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.jit=tracing
+opcache.jit_buffer_size=64M
+opcache.jit_hot_loop=1
+opcache.jit_hot_func=1
+opcache.jit_hot_return=1
+opcache.jit_hot_side_exit=1
+--FILE--
+<?php
+namespace Foo; // Needed so ord() and strlen() don't compile to opcodes
+
+// This code is heavily derived from phpseclib
+// License:
+// Copyright (c) 2011-2019 TerraFrost and other contributors
+// 
+// Permission is hereby granted, free of charge, to any person obtaining
+// a copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to
+// permit persons to whom the Software is furnished to do so, subject to
+// the following conditions:
+// 
+// The above copyright notice and this permission notice shall be
+// included in all copies or substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+function reduce(string $c, string $u): string {
+    $c = str_pad($c, 143, "\0", STR_PAD_LEFT);
+    for ($h = 5, $i = 1140; $i >= 571;) {
+        $g = $h >> 3;
+        for ($mask = 0x80; $mask > 0; $mask >>= 1, $i--, $h++) {
+            if (ord($c[$g]) & $mask) {
+                $temp = $i - 571;
+                $j = $temp >> 3;
+                $t1 = $j ? substr($c, 0, -$j) : $c;
+                $length = strlen($t1);
+                $temp = $t1 ^ str_pad($u, $length, "\0", STR_PAD_LEFT);
+                $c = substr_replace($c, $temp, 0, $length);
+            }
+        }
+    }
+    return $c;
+}
+
+var_dump(md5(reduce(str_repeat("\xff", 72), "\x04\x25")));
+?>
+--EXPECT--
+string(32) "dd12a5bb6e3d7b4abcdd92e135850169"
+