Tracing JIT: Fixed incorrect tracing type inference

There are some cases when IS_VAR/IS_TMP_VAR variables are set to IS_UNDEF.
TODO: It would be better to switch to IS_NULL in master.

Author: dstogov

ext/opcache/jit/zend_jit_trace.c

@@ -1436,6 +1436,12 @@ static zend_ssa *zend_jit_trace_build_tssa(zend_jit_trace_rec *trace_buffer, uin
 
 				if (op_type != IS_UNKNOWN) {
 					ssa_var_info[i].type &= zend_jit_trace_type_to_info(op_type);
+					if (!ssa_var_info[i].type
+					 && op_type == IS_UNDEF
+					 && i >= op_array->last_var) {
+						// TODO: It's better to use NULL instead of UNDEF for temporary variables
+						ssa_var_info[i].type |= MAY_BE_UNDEF;
+					}
 				}
 			}
 			i++;

ext/opcache/tests/jit/fe_reset_001.phpt

@@ -0,0 +1,37 @@
+--TEST--
+FE_RESET: 001 undef $$ operand
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.file_update_protection=0
+opcache.jit_buffer_size=1M
+--FILE--
+<?php
+for ($i = 0; $i < 5; $i++) {
+    for ($j = 0; $j < $i; $j++) {}
+    foreach ($$i as $x) {}
+}
+?>
+OK
+--EXPECTF--
+Warning: Undefined variable $0 in %sfe_reset_001.php on line 4
+
+Warning: foreach() argument must be of type array|object, null given in %sfe_reset_001.php on line 4
+
+Warning: Undefined variable $1 in %sfe_reset_001.php on line 4
+
+Warning: foreach() argument must be of type array|object, null given in %sfe_reset_001.php on line 4
+
+Warning: Undefined variable $2 in %sfe_reset_001.php on line 4
+
+Warning: foreach() argument must be of type array|object, null given in %sfe_reset_001.php on line 4
+
+Warning: Undefined variable $3 in %sfe_reset_001.php on line 4
+
+Warning: foreach() argument must be of type array|object, null given in %sfe_reset_001.php on line 4
+
+Warning: Undefined variable $4 in %sfe_reset_001.php on line 4
+
+Warning: foreach() argument must be of type array|object, null given in %sfe_reset_001.php on line 4
+OK
+