Tracinf JIT: Prevnt generation code for instruction that with cyclic dependency

e.g. $a[] += $a is compiled into ASSIGN_DIM_OP+OP_DATA, where OP_DATA.op1_use depends on ASSIGN_DIM_OP.op1_def

Author: dstogov

ext/opcache/jit/zend_jit_trace.c

@@ -1520,6 +1520,11 @@ static zend_ssa *zend_jit_trace_build_tssa(zend_jit_trace_rec *trace_buffer, uin
 					/* break missing intentionally */
 				case ZEND_ASSIGN_DIM:
 					if (opline->op1_type == IS_CV) {
+						if ((opline+1)->op1_type == IS_CV
+						 && (opline+1)->op1.var == opline->op1.var) {
+							/* skip $a[x] = $a; */
+							break;
+						}
 						ADD_OP1_DATA_TRACE_GUARD();
 						ADD_OP2_TRACE_GUARD();
 						ADD_OP1_TRACE_GUARD();
@@ -1553,6 +1558,12 @@ static zend_ssa *zend_jit_trace_build_tssa(zend_jit_trace_rec *trace_buffer, uin
 						break;
 					}
 					if (opline->opcode == ZEND_ASSIGN_OBJ_OP) {
+						if (opline->op1_type == IS_CV
+						 && (opline+1)->op1_type == IS_CV
+						 && (opline+1)->op1.var == opline->op1.var) {
+							/* skip $a->prop += $a; */
+							break;
+						}
 						ADD_OP1_DATA_TRACE_GUARD();
 					}
 					ADD_OP1_TRACE_GUARD();
@@ -4219,6 +4230,12 @@ static const void *zend_jit_trace(zend_jit_trace_rec *trace_buffer, uint32_t par
 								opline->extended_value, MAY_BE_ANY, OP1_DATA_INFO())) {
 							break;
 						}
+						if (opline->op1_type == IS_CV
+						 && (opline+1)->op1_type == IS_CV
+						 && (opline+1)->op1.var == opline->op1.var) {
+							/* skip $a[x] += $a; */
+							break;
+						}
 						op1_info = OP1_INFO();
 						op1_addr = OP1_REG_ADDR();
 						if (opline->op1_type == IS_VAR) {
@@ -4336,6 +4353,12 @@ static const void *zend_jit_trace(zend_jit_trace_rec *trace_buffer, uint32_t par
 						 || Z_STRVAL_P(RT_CONSTANT(opline, opline->op2))[0] == '\0') {
 							break;
 						}
+						if (opline->op1_type == IS_CV
+						 && (opline+1)->op1_type == IS_CV
+						 && (opline+1)->op1.var == opline->op1.var) {
+							/* skip $a->prop += $a; */
+							break;
+						}
 						if (!zend_jit_supported_binary_op(
 								opline->extended_value, MAY_BE_ANY, OP1_DATA_INFO())) {
 							break;
@@ -4480,6 +4503,12 @@ static const void *zend_jit_trace(zend_jit_trace_rec *trace_buffer, uint32_t par
 					case ZEND_ASSIGN_DIM:
 						op1_info = OP1_INFO();
 						op1_addr = OP1_REG_ADDR();
+						if (opline->op1_type == IS_CV
+						 && (opline+1)->op1_type == IS_CV
+						 && (opline+1)->op1.var == opline->op1.var) {
+							/* skip $a[x] = $a; */
+							break;
+						}
 						if (opline->op1_type == IS_VAR) {
 							if (orig_op1_type != IS_UNKNOWN
 							 && (orig_op1_type & IS_TRACE_INDIRECT)

ext/opcache/tests/jit/assign_dim_op_004.phpt

@@ -0,0 +1,20 @@
+--TEST--
+JIT ASSIGN_DIM_OP: Cyclic dependency
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.file_update_protection=0
+opcache.jit_buffer_size=1M
+--FILE--
+<?php
+$a = null; 
+$a[] .= $a;
+var_dump($a);
+?>
+--EXPECTF--
+Warning: Array to string conversion in %sassign_dim_op_004.php on line 3
+array(1) {
+  [0]=>
+  string(5) "Array"
+}
+