Merge branch 'PHP-7.4'

* PHP-7.4:
  Fix pi node removal when removing predecessor

Author: nikic

Zend/tests/remove_predecessor_of_pi_node.phpt

@@ -0,0 +1,14 @@
+--TEST--
+Regression test for incorrect update of pi node users when removing a predecessor block
+--FILE--
+<?php
+
+function test() {
+    for (; $n--; )
+        C;
+}
+test();
+
+?>
+--EXPECTF--
+Warning: Undefined variable $n in %s on line %d

ext/opcache/Optimizer/zend_ssa.c

@@ -1409,7 +1409,7 @@ void zend_ssa_remove_predecessor(zend_ssa *ssa, int from, int to) /* {{{ */
 	for (phi = next_ssa_block->phis; phi; phi = phi->next) {
 		if (phi->pi >= 0) {
 			if (phi->pi == from) {
-				zend_ssa_remove_uses_of_var(ssa, phi->ssa_var);
+				zend_ssa_rename_var_uses(ssa, phi->ssa_var, phi->sources[0], /* update_types */ 0);
 				zend_ssa_remove_phi(ssa, phi);
 			}
 		} else {