Code Warrior optimization efficiency

[admin]

I did not use CW in the past and getting now new experience with CW toolchain. We ported our application to CW recently and met resources problem taking ~85% of the flash memory available on MCF52259 MCU. At the first glance it shows that the hardware platform is not scaled properly to the application and should be respinned with more resources. A few days ago I decided to try another compiler (IAR CF) and to my big surprise the application size reduced by ~30%. I ported all application code  and the result was still there 30% less size.

Curios, I created a small project for both compilers and tried side by side comparison for function code sizes. The project is FreeRtos based demo with basic task switching. I took one module (tasks.c) and here is the result. CW v.7.1 and IAR CF v.1.22. 

No optimization:

                                     CW No optimization          IAR No optimization      

                                              HEX    DEC             HEX   DEC       %

xTaskGenericCreate                      162  354               176   374   106

vTaskStartScheduler                      60    96                52     82     85

vTaskSuspendAll                             E    14                  8      8     57

xTaskResumeAll                           11C   284              112   274     96

vTaskIncrementTick                       EC  236                C8   200     85

vTaskSwitchContext                     114  276               11A   282    102

prvIdleTask                                  10    16                   E    14     88

prvInitialiseTCBVariables                  7E  126                 6C   108    86

prvInitialiseTaskLists                       88  136                 82   130    96

prvCheckTasksWaitingTermination     8A  138                 7E   126    91

prvAllocateTCBAndStack                 7C  124                 8E    142   115

prvDeleteTCB                                26   38                  1E     30     79  

                                                         TOTAL 1838            TOTAL 1770 96%

Both compiles create almost similar results. I think for 2k code 4% difference is neglectable. 

Optimization L3 for code size:

                                    CW L3 optimization     IAR Medium optimization      

                                              HEX   DEC                HEX   DEC     %

xTaskGenericCreate                       15C 348                150   336     97

vTaskStartScheduler                       62   98                  46    70     71

vTaskSuspendAll                              E   14                    8     8     57

xTaskResumeAll                             118 280                  F0  240     86

vTaskIncrementTick                         FA 250                 CA  202     81

vTaskSwitchContext                       128 296                 DA  218     74

prvIdleTask                                       C 12                    8     8     67

prvInitialiseTCBVariables                     76 118                 56   86     73

prvInitialiseTaskLists                          7E 126                 6E  110    87

prvCheckTasksWaitingTermination        8C 140                 72  114    81

prvAllocateTCBAndStack                    74  116                 58   88    76

prvDeleteTCB                                   26   38                 1A   26    68  

                                                     TOTAL       1836        TOTAL 1506  82%

It looks likeas CW optimization doesn't work properly.   

I pushed it to level 4:

                                          CW L4 optimization     IAR High optimization      

                                                   HEX   DEC            HEX   DEC   %

xTaskGenericCreate                         15C   348             1E6   486   140

vTaskStartScheduler                         62     98               46    70     71

vTaskSuspendAll                                E     14                 8     8     57

xTaskResumeAll                               118    280              EA  234     84

vTaskIncrementTick                           FA    250             A4  164     66

vTaskSwitchContext                         128    296             DA  218     74

prvIdleTask                                        C     12             76    118    983

prvInitialiseTCBVariables                      76    118        

prvInitialiseTaskLists                           7E    126        

prvCheckTasksWaitingTermination         8C    140        

prvAllocateTCBAndStack                      74    116        

prvDeleteTCB                                     26    38          

                                                              TOTAL   1836       TOTAL 1298  71%

At that level IAR compiler starts inlining so some functions was eliminated but still the code size reduced even more.CW did not improve at all.

Am I doing something wrong? For me it looks like quite mediocre performance.

Regards,  Dmitri.

[toucan]

Could you share your project for further analysis? Or you can visit http://www.freescale.com/support and submit a service request with for this issue:
Category = Technical Request
Topic = CodeWarrior

Thanks,

Kevin

[bkatt]

Levels of optimization usually refer to code speed, not code size. If you want to optimize for code size, you have to inidicate that option to the compiler, and there are typically fewer choices of levels.

When using CodeWarrior for ColdFire, you will get smaller code by enabling the register paramater passing convention. IPA (inter-procedural analysis) and automatic inlining might also help.

[admin]

I tried you recipe, It improves but still loosing to IAR quite a lot:

                                         CW L4 optimization     IAR High optimization      

                                                   HEX   DEC            HEX   DEC     %

xTaskGenericCreate                         2A4   586            1E6   486     140

vTaskStartScheduler                         62     98              46    70      71

vTaskSuspendAll                                E     14                8     8      57

xTaskResumeAll                              118    280              EA  234      84

vTaskIncrementTick                         FA    250               A4  164      66

vTaskSwitchContext                       128    296               DA  218     74

prvIdleTask                                    96     150             76    118     983

                                                              TOTAL   1674       TOTAL 1298  78%

[admin]

I tried your suggestions. No magic happened.