ACPICA: Optimize execution of AML While loops

Previously, a control state object was allocated and freed for
each execution of the loop. The optimization is to simply reuse
the control state for each iteration. This speeds up the raw loop
execution time by about 5%.
Signed-off-by: NBob Moore <robert.moore@intel.com>
Signed-off-by: NLin Ming <ming.m.lin@intel.com>
Signed-off-by: NLen Brown <len.brown@intel.com>

drivers/acpi/dispatcher/dsopcode.c

@@ -1140,9 +1140,28 @@ acpi_ds_exec_begin_control_op(struct acpi_walk_state *walk_state,
 			  op->common.aml_opcode, walk_state));
 
 	switch (op->common.aml_opcode) {
-	case AML_IF_OP:
 	case AML_WHILE_OP:
 
+		/*
+		 * If this is an additional iteration of a while loop, continue.
+		 * There is no need to allocate a new control state.
+		 */
+		if (walk_state->control_state) {
+			if (walk_state->control_state->control.aml_predicate_start
+				== (walk_state->parser_state.aml - 1)) {
+
+				/* Reset the state to start-of-loop */
+
+				walk_state->control_state->common.state =
+				    ACPI_CONTROL_CONDITIONAL_EXECUTING;
+				break;
+			}
+		}
+
+		/*lint -fallthrough */
+
+	case AML_IF_OP:
+
 		/*
 		 * IF/WHILE: Create a new control state to manage these
 		 * constructs. We need to manage these as a stack, in order
@@ -1248,8 +1267,13 @@ acpi_ds_exec_end_control_op(struct acpi_walk_state * walk_state,
 			/* Predicate was true, go back and evaluate it again! */
 
 			status = AE_CTRL_PENDING;
+			walk_state->aml_last_while =
+			    walk_state->control_state->control.aml_predicate_start;
+			break;
 		}
 
+		/* Predicate was false, terminate this while loop */
+
 		ACPI_DEBUG_PRINT((ACPI_DB_DISPATCH,
 				  "[WHILE_OP] termination! Op=%p\n", op));
 
@@ -1257,9 +1281,6 @@ acpi_ds_exec_end_control_op(struct acpi_walk_state * walk_state,
 
 		control_state =
 		    acpi_ut_pop_generic_state(&walk_state->control_state);
-
-		walk_state->aml_last_while =
-		    control_state->control.aml_predicate_start;
 		acpi_ut_delete_generic_state(control_state);
 		break;