JIT: Fix crash during compilation of function with incompletely constructed SSA

Fixes oss-fuzz #42200

Author: dstogov

ext/opcache/jit/zend_jit.c

@@ -2311,7 +2311,7 @@ static int zend_jit(const zend_op_array *op_array, zend_ssa *ssa, const zend_op
 		}
 		end = ssa->cfg.blocks[b].start + ssa->cfg.blocks[b].len - 1;
 		for (i = ssa->cfg.blocks[b].start; i <= end; i++) {
-			zend_ssa_op *ssa_op = &ssa->ops[i];
+			zend_ssa_op *ssa_op = ssa->ops ? &ssa->ops[i] : NULL;
 			opline = op_array->opcodes + i;
 			switch (opline->opcode) {
 				case ZEND_INIT_FCALL:
@@ -2342,6 +2342,7 @@ static int zend_jit(const zend_op_array *op_array, zend_ssa *ssa, const zend_op
 							res_use_info = -1;
 
 							if (opline->result_type == IS_CV
+							 && ssa->vars
 							 && ssa_op->result_use >= 0
 							 && !ssa->vars[ssa_op->result_use].no_val) {
 								zend_jit_addr res_use_addr = RES_USE_REG_ADDR();
@@ -2406,6 +2407,7 @@ static int zend_jit(const zend_op_array *op_array, zend_ssa *ssa, const zend_op
 							res_use_info = -1;
 
 							if (opline->result_type == IS_CV
+							 && ssa->vars
 							 && ssa_op->result_use >= 0
 							 && !ssa->vars[ssa_op->result_use].no_val) {
 								zend_jit_addr res_use_addr = RES_USE_REG_ADDR();
@@ -2463,6 +2465,7 @@ static int zend_jit(const zend_op_array *op_array, zend_ssa *ssa, const zend_op
 							res_use_info = -1;
 
 							if (opline->result_type == IS_CV
+							 && ssa->vars
 							 && ssa_op->result_use >= 0
 							 && !ssa->vars[ssa_op->result_use].no_val) {
 								zend_jit_addr res_use_addr = RES_USE_REG_ADDR();

ext/opcache/tests/jit/mod_006.phpt

@@ -0,0 +1,19 @@
+--TEST--
+JIT MOD: 005
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.file_update_protection=0
+opcache.jit_buffer_size=1M
+opcache.protect_memory=1
+--FILE--
+<?php
+function foo(){
+    $a = 1;
+    $b = $a % 0;
+    yield $b;
+}
+?>
+DONE
+--EXPECT--
+DONE