Unified builds of compiler-rt together with LLVM failed for the Android SDKs. It got too complicated to redirect the way LLVM would configure the nested build-trees. Standalone builds slightly increase build time, but they turned out much simpler and we end up with less duplication of definitions.
As is, you cannot set all default fuzzer options directly using -sanitize-coverage. Because of this you can use default fuzzer sanitize-coverage args, or a limited number coverage options.
This PR adds pc-table and inline-8bit-counter as valid args to be parsed for sanitize-coverage flag. These are default fuzzer options -- and will allow customizing sanitizer-coverage in variations of fuzzer defaults. (i.e. w/o pc-table enabled).
In upstream clang the option -fno-sanitize-coverage exists to disable various coverage options. Swift currently does not have a convention of using excluding args for sanitizer flags. This aims to limit the need for a new flag by inclusively setting desired coverage up to current fuzzer defaults.
rdar://127881891
"Sanitizer Coverage" with a new flag ``-sanitize-coverage=``. This
flag is analogous to Clang's ``-fsanitize-coverage=``.
This instrumentation currently requires ASan or TSan to be enabled
because the module pass created by ``createSanitizerCoverageModulePass()``
inserts calls into functions found in compiler-rt's "sanitizer_common".
"sanitizer_common" is not shipped as an individual library but instead
exists in several of the sanitizer runtime libraries so we have to
link with one of them to avoid linking errors.
The rationale between adding this feature is to allow experimentation
with libFuzzer which currently relies on "Sanitizer Coverage"
instrumentation.
