In order for recent gcov versions to read the coverage data, you have to use UseCfgChecksum=true and FunctionNamesInData=false options for coverage profiling pass. This is because gcov is expecting the function section in .gcda to be exactly 3 words in size, containing ident and two checksums.
While llvm-cov is compatible with UseCfgChecksum=true, it always expects a function name in .gcda function sections (it's not compatible with FunctionNamesInData=false). Thus it's currently impossible to generate one set of coverage files that works with both gcov and llvm-cov.
This change fixes the reading of coverage information to only read the function name if it's present.