Optimization Levels

Exactly how do you measure changes in code size?

As you experiment with builds for code size, please keep the optimization level high.  Use --opt_level=2 or --opt_level=3.  Then vary the setting for --opt_for_space.  You should see a difference.

Please consider measuring code size with this method.  Read this wiki article about finding functions which increase in code size the most.  You don't want to do that.  But it is worth knowing a method for collecting the code size of individual functions and loading that into a spreadsheet.  Even if overall size does not change that much, you should see individual functions changing size.

Thanks and regards,

-George

Hi George Mock,

thanks a lot for your answer.

As suggested by JohnS I used the Memory Allocation window, in particular the size of L2SRAM memory. 

Below the results for: Speed vs. size trade-offs = 4.

Changing Speed vs. size trade-offs = 0, no differences are visible.

Do you know why?

Thank you in advance.

Best regards

Geni 

Geni Butera said:

Do you know why?

I have a guess.  The size varies from 144 bytes to 150 bytes.  This must be one function.  Or maybe 2 or 3 really small functions.  Is that right?  It seems likely there is very little opportunity for code size improvements in these functions.

Instead of looking at how much L2SRAM you use ... What is the total size of the .text section?  That section contains all the code.  You can see the size of this section in the linker map file.  It usually has the same name as the executable .out file, but with the extension changed to .map.

Thanks and regards,

-George

Hi George,

yes, it is right, are just a few functions.

The length of the .text section is 74848 Byte (0x12460) as shown below:

==================================================================

SEGMENT ALLOCATION MAP

run origin  load origin   length   init length attrs members

----------  ----------- ---------- ----------- ----- -------

00800000    00800000    00012460   00012460    r-x

 00800000    00800000    00012460   00012460    r-x .text

00812460    00812460    00008e7c   00000000    rw-

 00812460    00812460    00008e7c   00000000    rw- .far

0081b2e0    0081b2e0    00004152   00004152    r--

 0081b2e0    0081b2e0    00004152   00004152    r-- .const

0081f438    0081f438    000035e4   00000000    rw-

 0081f438    0081f438    00002000   00000000    rw- .stack

 00821438    00821438    0000146c   00000000    rw- .fardata

 008228a8    008228a8    00000120   00000000    rw- .cio

 008229c8    008229c8    00000024   00000000    rw- .bss

 008229f0    008229f0    0000002c   00000000    rw- .neardata

00822c00    00822c00    00000a50   00000a50    r-x

 00822c00    00822c00    00000200   00000200    r-x .vecs

 00822e00    00822e00    00000850   00000850    r-- .cinit

==================================================================

below, instead, the memory configuration:

==================================================================

MEMORY CONFIGURATION

name                     origin     length      used      unused  attr      fill
----------------------  --------    ---------    --------    ----------   ----    -------
L2SRAM                       00800000   00080000    0002345e    0005cba2    RW          X
MSMCSRAM                0c000000   00400000    00200000    00200000    RW          X
DDR3                           80000000    20000000    00000000    20000000    RWI         X

==================================================================

Thanks

Regards

Geni