The compiler-rt library support for gcov is currently only working correctly on little-endian systems.
Two separate fixes are required to handle big-endian systems as well:
- 64-bit counter values are stored in a mixed-endian format in the gcov files: a 32-bit low-part followed by a 32-bit high part. Note that this is already implemented correctly on the LLVM side, see GCOVBuffer::readInt64.
- The tag values (e.g. arcs tag, object summary tag, ...) are aways written as the same sequence of bytes independent of byte order. But when *reading* them back in, the code reads them as 32-bit values in host byte order. For the comparisons to work correctly, this should instead always read them as little-endian values.