Merge branch 'PHP-8.0' into PHP-8.1

* PHP-8.0:
  Handle undefined dim in assign_dim_helper

Author: nikic

ext/opcache/jit/zend_jit_helpers.c

@@ -1042,6 +1042,12 @@ static void ZEND_FASTCALL zend_jit_fetch_dim_obj_rw_helper(zval *object_ptr, zva
 
 static void ZEND_FASTCALL zend_jit_assign_dim_helper(zval *object_ptr, zval *dim, zval *value, zval *result)
 {
+	if (dim && UNEXPECTED(Z_TYPE_P(dim) == IS_UNDEF)) {
+		const zend_op *opline = EG(current_execute_data)->opline;
+		zend_jit_undefined_op_helper(opline->op2.var);
+		dim = &EG(uninitialized_zval);
+	}
+
 	if (UNEXPECTED(Z_TYPE_P(value) == IS_UNDEF)) {
 		const zend_op *op_data = EG(current_execute_data)->opline + 1;
 		ZEND_ASSERT(op_data->opcode == ZEND_OP_DATA && op_data->op1_type == IS_CV);

ext/opcache/tests/jit/assign_dim_004.phpt

@@ -0,0 +1,26 @@
+--TEST--
+JIT ASSIGN_DIM: 004
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.file_update_protection=0
+opcache.jit_buffer_size=1M
+--FILE--
+<?php
+class Test implements ArrayAccess {
+    function offsetExists($x): bool {}
+    function offsetGet($x): mixed {}
+    function offsetSet($x, $y): void {
+        echo "offsetSet($x, $y)\n";
+    }
+    function offsetUnset($x): void {}
+}
+function test() {
+    $obj = new Test;
+    $obj[$undef] = 1;
+}
+test();
+?>
+--EXPECTF--
+Warning: Undefined variable $undef in %s on line %d
+offsetSet(, 1)