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MSP430FR5739 text size and strange optimization behavior.

Silver Diamond
Genius 4010 points
Other Parts Discussed in Thread: MSP430FR5739

I use CCS5.4, and did test shown below.  I do not understand why optimization level 4 produces larger file then 3.  Also, would you have recommendations to minimize program size?  I am tight on memory, but have plenty of speed and power to run.

1) =========================================================================================================
Optimization Level: 4
Speed vs Size: 5

Error: "../lnk_msp430fr5739.cmd", line 127: error #10099-D: program will not fit into available memory. placement with alignment fails for section "ALL_FRAM" size 0x7737. Available memory ranges: FRAM size: 0x3d80 unused: 0x37de max hole: 0x37de GROUP(ALL_FRAM) error #10010: errors encountered during linking; "C1202.out" not built

From C1202.map file from debug folder:

.text 0 00000800 00006cc8
00000800 00003634 debug.obj (.text:_Z10debug_scanv)
00003e34 00000728 debug.obj (.text:_ZN12StateMachine12stateF_derefEPKj)
0000455c 000005d8 modem.obj (.text:_Z15Modem_read_smsFPj)

The debug.obj function called debug_scan is 13876 bytes long, its huge. Makes sense, probably in-lining everything.
2) =========================================================================================================

Optimization Level: 4
Speed vs Size: 0
Error: "../lnk_msp430fr5739.cmd", line 127: error #10099-D: program will not fit into available memory. placement with alignment fails for section "ALL_FRAM" size 0x4fbf . Available memory ranges:
FRAM size: 0x3d80 unused: 0x37de max hole: 0x37de
GROUP(ALL_FRAM)
error #10010: errors encountered during linking; "C1202.out" not built

From C1202.map file from debug folder:
.text 0 00000800 00004550
00000800 00001a34 debug.obj (.text:_Z10debug_scanv)
00002234 00000448 debug.obj (.text:_ZN12StateMachine12stateF_derefEPKj)
0000267c 000003c2 modem.obj (.text:_Z15Modem_read_smsFPj)

The debug.obj function called debug_scan is 6708 bytes long, its still large. Does not make sense the function is only 1 page long, cannot be that big, it is optimizing for size.

3) =========================================================================================================
Optimization Level: off

Error: "../lnk_msp430fr5739.cmd", line 127: error #10099-D: program will not fit into available memory. placement with alignment fails for section "ALL_FRAM" size 0x3c8b . Available memory ranges:

>> Compilation failure
FRAM size: 0x3d80 unused: 0x37de max hole: 0x37de

From C1202.map file from debug folder:
.text 0 00000800 0000320a FAILED TO ALLOCATE

So it looks like the program size is 0x3c8b, which is smallest with optimization off so far. This does not make sense

4) =========================================================================================================
Optimization Level: 0
Speed vs Size: 0

"../lnk_msp430fr5739.cmd", line 127: error #10099-D: program will not fit into available memory. placement with alignment fails for section "ALL_FRAM" size 0x3e97 . Available memory ranges:

>> Compilation failure
FRAM size: 0x3d80 unused: 0x37de max hole: 0x37de
GROUP(ALL_FRAM)

From C1202.map file from debug folder:
.text 0 00000800 00003416
00000800 000005d4 sensor.obj (.text:_Z14Sensor_uploadFPj)
00000dd4 000002ec modem.obj (.text:_Z18Modem_upload_dataFPj)
000010c0 00000286 main.obj (.text:main)
000017fe 00000218 debug.obj (.text:_Z10debug_scanv)

Wow What a change, size of debug.obj function debug_scan is down to 536 from 6708 bytes (more then 90% reduction). What is going on?

5) =========================================================================================================
Optimization Level: 2
Speed vs Size: 0

No Error, works fine

From C1202.map file from debug folder:
.text 0 0000d000 00002e1c
0000d000 000003a6 sensor.obj (.text:_Z14Sensor_uploadFPj)
0000d3a6 0000027c modem.obj (.text:_Z18Modem_upload_dataFPj)
0000d622 00000208 modem.obj (.text:_Z20Modem_get_at_promptFPj)
0000d82a 00000206 modem.obj (.text:_Z15Modem_read_smsFPj)
0000da30 000001e6 debug.obj (.text:_Z10debug_scanv)

When I upload the program, console outputs the following:
MSP430: Loading complete. Code Size - Text: 11804 bytes Data: 1182 bytes.

 Thanks...

 

  • TI__Guru**** 249900 points

    Across many files and functions, I would expect optimization level 4 and speed vs size level 0 to have the smallest code size.  For a single function, though, it is not surprising to see a result like yours.  That is the nature of how compilers work.  This wiki article gets into some of the details.

    Thanks and regards,

    -George

  • in reply to George Mock
    Genius 4010 points

    OK, I will buy that as an answer to first part of the question.  Any pointers on making compiled code smallest possible besides using efficient coding techniques such as avoid modulo, division, multiplication and other emulated operations?  How would you go about it?

    For for the rest of us, through this tests, the following are my conclusions:

    • Optimization level 4 can be so over zealous that it can have an adverse effect.
    • Optimization Level 2 and 3 Produced the best result to reduce the code size in this case but while optimizing, I would test different optimization levels and monitor program size.

    Silver D