sdccrm
What is sdccrm?
sdccrm is a dead code optimization tool for the stm8 port of sdcc that removes unused functions. By configuring an entry point, sdccrm creates a function call tree and determines which labels can be optimized away.
Usage
sdccrm [options] file1 file2 ...sdccrm will output .asmrm files unless the -r switch is used, which replaces the original .asm files:
sdccrm -r file1 file2 ...Symbols that are not called from the generated function call tree (e.g.: interrupt handlers only referrenced on the interrupt vector) can be explicitely defined by the user. For example:
sdccrm -x _do_not_exlude_this_label file1 file2 ..._main is defined as the default entry label. However, a user-defined entry label can be defined:
sdccrm -e _new_entry_point file1 file2 ...A verbose mode can be enabled by using the -v switch, which informs about what is being optimized away:
sdccrm -v file1 file2 ...Why this tool?
Unfortunately, as of sdcc-3.9.0, unused functions are not removed by the optimizer. After reading its source code thoroughly and being under time pressure, it seemed like a good idea to implement a separate tool for this.
How does it work?
sdccrm takes one or more .asm files, which are usually generated by sdcc when using the -S (assemble, no compile) switch. Then, it takes a user-defined entry point ("_main" is assumed by default unless indicated otherwise) and generates a function call tree. All unused labels are removed away from the .asm file so sdcc can now compile these optimized .asm files seamlessly, while optimizing MCU memory usage.
Why is this optimization not done by the compiler?
Sincerely, I have no idea - I guess sdcc being essentially an open-source, community-driven effort might lack some more development. However, I needed this optimization as I was partly using a third-part API which included many functions that I did not need. I just cannot find acceptable these unused functions are not optimzed away, as it took more than half of the microcontroller memory.
License
Similarly to sdcc, sdccrm is licensed under GPLv3.
Known issues
Removing unused declarations and definitions will surely give problems when --debug switch is used by sdcc, as debugging symbols need to point to those now-unexisting labels. Unused static variables are not being removed.