Fix GH-15834: Segfault with hook "simple get" cache slot and minimal JIT

The FETCH_OBJ_R VM handler has an optimization that directly enters into
a hook if it is a simpler getter hook. This is not compatible with the
minimal JIT because the minimal JIT will try to continue executing the
opcodes after the FETCH_OBJ_R.
To solve this, we check whether the opcode is still the expected one
after the execution of the VM handler. If it is not, we know that we are
going to execute a simple hook. In that case, exit to the VM.

Author: nielsdos

ext/opcache/jit/zend_jit.c

@@ -2709,6 +2709,23 @@ static int zend_jit(const zend_op_array *op_array, zend_ssa *ssa, const zend_op
 						/* We skip over the DO_FCALL, so decrement call_level ourselves. */
 						call_level--;
 					}
+					break;
+				case ZEND_FETCH_OBJ_R:
+					if (!zend_jit_handler(&ctx, opline,
+						zend_may_throw(opline, ssa_op, op_array, ssa))) {
+						goto jit_failure;
+					}
+
+					/* If a simple hook is called, exit to the VM. */
+					ir_ref if_hook_enter = ir_IF(jit_CMP_IP(jit, IR_EQ, opline + 1));
+					ir_IF_FALSE(if_hook_enter);
+					if (GCC_GLOBAL_REGS || zend_jit_vm_kind == ZEND_VM_KIND_HYBRID) {
+						ir_TAILCALL(IR_VOID, ir_LOAD_A(jit_IP(jit)));
+					} else {
+						ir_RETURN(ir_CONST_I32(1)); /* ZEND_VM_ENTER */
+					}
+					ir_IF_TRUE(if_hook_enter);
+
 					break;
 				default:
 					if (!zend_jit_handler(&ctx, opline,

ext/opcache/tests/jit/gh15834.phpt

@@ -0,0 +1,23 @@
+--TEST--
+GH-15834 (Segfault with hook "simple get" cache slot and minimal JIT)
+--EXTENSIONS--
+opcache
+--INI--
+opcache.jit=1111
+--FILE--
+<?php
+class A {
+    public $_prop = 1;
+    public $prop {
+        get => $this->_prop;
+    }
+}
+
+$a = new A;
+for ($i=0;$i<5;$i++) {
+    echo $a->prop;
+    $a->_prop++;
+}
+?>
+--EXPECT--
+12345