When the new regression test gte/pr24851.c is enabled in cases/Makefile.in, it triggers an assertion in code generation - I tested with both stm8 and z80, and for both an assertion is triggered. Maybe the two backends contain a similar bug, or an earlier stage passes broken iCode to the backends.
I can no longer reproduce this issue; looks like the recent fix for [bugs:#3503] covered it.
Related
Bugs:
#3503