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There has been some work on a change of the ABI in SDCC. It is not yet decided if the change will go ahead.

Basically, such a change would break existing asm code (as the way parameters and return values are passed)¹, but would give an improvement in code size and speed.

In particular, the new ABI would pass some parameters in registers, would pass the return values in different registers, and for some function the cleanup of stack parameters would be done by the callee instead of the caller.

More details can be found in the SDCC feature request:

https://sourceforge.net/p/sdcc/feature-requests/732/

And in discussion on the sdcc-user mailing list.

Work is happening the in the breaktheworld branch https://sourceforge.net/p/sdcc/code/HEAD/tree/branches/breaktheworld/, where the new ABI is the default, and mostly working (in particular, banked calls are not yet working there).

¹ There is a way to mark individual functions as using the old ABI via __sdcccall(0) to continue using existing asm functions from C code compiled for the new convention. And an option --sdcccall N to set the default ABI version.

Author	Message
PkK Joined: 07 Aug 2007 Posts: 220 Location: Yach, Germany	SDCC maybe changing the default ABI Posted: Sat Aug 14, 2021 6:41 am
	There has been some work on a change of the ABI in SDCC. It is not yet decided if the change will go ahead. Basically, such a change would break existing asm code (as the way parameters and return values are passed)¹, but would give an improvement in code size and speed. In particular, the new ABI would pass some parameters in registers, would pass the return values in different registers, and for some function the cleanup of stack parameters would be done by the callee instead of the caller. More details can be found in the SDCC feature request: https://sourceforge.net/p/sdcc/feature-requests/732/ And in discussion on the sdcc-user mailing list. Work is happening the in the breaktheworld branch https://sourceforge.net/p/sdcc/code/HEAD/tree/branches/breaktheworld/, where the new ABI is the default, and mostly working (in particular, banked calls are not yet working there). ¹ There is a way to mark individual functions as using the old ABI via __sdcccall(0) to continue using existing asm functions from C code compiled for the new convention. And an option --sdcccall N to set the default ABI version.

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