Perhaps GC_push_regs was configured incorrectly (Cygwin/gcc-11)

[ivmai]

Source: master (cfb325f)
Host: Win64 (Cygwin64)
Compiler: gcc (GCC) 11.2.0
How to reproduce: gcc -O3 -I include -D GC_ASSERTIONS tests/gctest.c extra/gc.c && a.exe
Output:
Switched to incremental mode
Emulating dirty bits with mprotect/signals
Apparently failed to mark from some function arguments.
Perhaps GC_push_regs was configured incorrectly?
Test failed

Also reproduced with: -D GC_DISABLE_INCREMENTAL
Not reproduced with -O2 (or lower) or w/o -D GC_ASSERTIONS

[ivmai]

Reproduced also if added: -D HAVE_BUILTIN_UNWIND_INIT
Thus, commit ffb9f1e seems to be wrong (needs to be reverted).

[ivmai]

May also lead to "List reversal produced incorrect list - collector is broken" error in gctest (seems to be the same root cause).

[ivmai]

In the following config, it is reproduced in ~1/30 runs:
gcc -O3 -I include -Wall -Wextra -Wpedantic -D GC_THREADS -D THREAD_LOCAL_ALLOC -D PARALLEL_MARK -D GC_ASSERTIONS tests/gctest.c extra/gc.c

[ivmai]

Probably should be fixed by #566 (although I am not sure gcc-11 has the mentioned optimization)