How-To: Huge improvement in firmware size!

[bootsector]

Create the following text file inside the specified folder below from the unzipped release package:

Arduino IDE\hardware\arduino\avr\platform.local.txt

Add the following contents to it then save it:

compiler.c.extra_flags=-mcall-prologues
compiler.cpp.extra_flags=-mcall-prologues
compiler.S.extra_flags=
compiler.ar.extra_flags=
compiler.objcopy.eep.extra_flags=
compiler.elf2hex.extra_flags=
compiler.c.elf.extra_flags=-Wl,--relax

Next time the Arduino IDE is opened, it will optmize the code generation even further.

These are the results for the same Config.h, before and after the code optimization.

Before:

After:

That's saving almost 12KB from flash, which is huge! Added to that I'm plagued with the bootloader bug that prevents me to use the last 8KB usable page from flash, so this is came in handy! 😅

Hope this is useful to anyone else!

Suggestion: bundle this additional configuration file with the next release packages! 🙏

[Ancyker]

Note: This will increase function call times and may affect the timing of some cores. (This flag effectively turns 1 function call into 3 - 1 for the prologue, 1 for the function itself, and 1 for the epilogue.)

[sanni]

I added it to the build script and oscr_tool.ps1 so we can test it until the next release.

[bootsector]

I added it to the build script and oscr_tool.ps1 so we can test it until the next release.

Awesome! Tried with lots of cartridges here and everything seems to be working great!

[Ancyker]

Here's the impact on the firmware rework (assumes HW5):

Defaults (Minimal)
Before

Sketch uses 175108 bytes (67%) of program storage space. Maximum is 260096 bytes.
Global variables use 4710 bytes (57%) of dynamic memory, leaving 3482 bytes for local variables. Maximum is 8192 bytes.

After

Sketch uses 165836 bytes (63%) of program storage space. Maximum is 260096 bytes.
Global variables use 4710 bytes (57%) of dynamic memory, leaving 3482 bytes for local variables. Maximum is 8192 bytes.

Defaults (OBM) + All Hardware Features Enabled
Before

Sketch uses 182608 bytes (70%) of program storage space. Maximum is 258048 bytes.
Global variables use 4750 bytes (57%) of dynamic memory, leaving 3442 bytes for local variables. Maximum is 8192 bytes.

After

Sketch uses 172958 bytes (67%) of program storage space. Maximum is 258048 bytes.
Global variables use 4750 bytes (57%) of dynamic memory, leaving 3442 bytes for local variables. Maximum is 8192 bytes.