Link to the compiled function to improve performance

When JIT is recording, backtrack the trace if encountering
a compiled inline function and link to this function later.
This reduces the runtime compilation overhead and duplicated
JITTed code. Smaller code size has better cache efficiency,
which brings 1.7% performance gain in our benchmark on x86.

Signed-off-by: Wang, Xue   <[email protected]>
Signed-off-by: Yang, Lin A <[email protected]>
Signed-off-by: Su, Tao     <[email protected]>

Author: wxue1

ext/opcache/jit/zend_jit_vm_helpers.c

@@ -562,10 +562,14 @@ zend_jit_trace_stop ZEND_FASTCALL zend_jit_trace_execute(zend_execute_data *ex,
 	uint8_t  trace_flags, op1_type, op2_type, op3_type;
 	zend_class_entry *ce1, *ce2;
 	const zend_op *link_to_enter_opline = NULL;
+	/* Remember the first opline of inline function*/
+	const zend_op *link_to_inline_func_opline = NULL;
 	int backtrack_link_to_enter = -1;
 	int backtrack_recursion = -1;
 	int backtrack_ret_recursion = -1;
 	int backtrack_ret_recursion_level = 0;
+	/* Remember the index of inline function opline in the trace buffer */
+	int backtrack_link_to_inline_func = -1;
 	int loop_unroll_limit = 0;
 	int last_loop = -1;
 	int last_loop_level = -1;
@@ -922,6 +926,12 @@ zend_jit_trace_stop ZEND_FASTCALL zend_jit_trace_execute(zend_execute_data *ex,
 				} else if (count >= JIT_G(max_recursive_calls)) {
 					stop = ZEND_JIT_TRACE_STOP_DEEP_RECURSION;
 					break;
+				/* If the inline function is JITTed, backtrack this trace. */
+				} else if ( backtrack_link_to_inline_func < 0 && \
+					(ZEND_OP_TRACE_INFO(opline, offset)->trace_flags & ZEND_JIT_TRACE_JITED)) {
+					backtrack_link_to_inline_func = idx;
+					link_to_inline_func_opline = opline;
+					break;
 				}
 
 				unrolled_calls[ret_level + level] = &EX(func)->op_array;
@@ -1156,6 +1166,11 @@ zend_jit_trace_stop ZEND_FASTCALL zend_jit_trace_execute(zend_execute_data *ex,
 			ret_level = backtrack_ret_recursion_level;
 			stop = ZEND_JIT_TRACE_STOP_RECURSIVE_RET;
 			end_opline = orig_opline;
+		} else if (backtrack_link_to_inline_func > 0) {
+			/* Reset the index and stop flag to link to the compiled inline function. */
+			idx = backtrack_link_to_inline_func;
+			stop = ZEND_JIT_TRACE_STOP_LINK;
+			end_opline = link_to_inline_func_opline;
 		} else if (backtrack_link_to_enter > 0) {
 			if (stop == ZEND_JIT_TRACE_STOP_DEEP_RECURSION
 			 && zend_jit_trace_bad_stop_event(orig_opline, JIT_G(blacklist_root_trace) / 2) ==