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: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

diff --git a/drivers/acpi/dispatcher/dsopcode.c b/drivers/acpi/dispatcher/dsopcode.c
index 69fae5905bb8219af26b0e0684ae22cedc1b84dc..5cd406676c2ccdfa126806c936e34d600204bf8e 100644 (file)
--- a/drivers/acpi/dispatcher/dsopcode.c
+++ b/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;