No functionality change is intended with this commit, it just consolidates
the separate implementations of GC helper code to the lib/utils/ directory
as a general set of helper functions useful for any port. This reduces
duplication of code, and makes it easier for future ports or embedders to
get the GC implementation correct.
Ports should now link against gchelper_native.c and either gchelper_m0.s or
gchelper_m3.s (currently only Cortex-M is supported but other architectures
can follow), or use the fallback gchelper_generic.c which will work on
x86/x64/ARM.
The gc_helper_get_sp function from gchelper_m3.s is not really GC related
and was only used by cc3200, so it has been moved to that port and renamed
to cortex_m3_get_sp.
Based on eg 1e6fd9f2b4, it's understood that
the intention for unix builds is that regular builds disable assert, but
the coverage build should set -O0 and enable asserts.
It looks like this didn't work (even before variants were introduced, eg at
v1.11) -- coverage always built with -Os and -DNDEBUG.
This commit makes it possible for variants to have finer-grained control
over COPT flags, and enables assert() and -O0 on coverage builds.
Other variants already match the defaults so they have been updated.
Invoking "make" will still build the standard "micropython" executable, but
other variants are now build using, eg, "make VARIANT=minimal". This
follows how bare-metal ports specify a particular board, and allows running
any make target (eg clean, test) with any variant.
Convenience targets (eg "make coverage") are provided to retain the old
behaviour, at least for now.
See issue #3043.
