[SR-7994] Use libfuzzer on sil-opt (i.e. implement sil-opt-fuzzer).

[gottesmm]

Previous ID	SR-7994
Radar	None
Original Reporter	@gottesmm
Type	New Feature

Additional Detail from JIRA

| | | |------------------|-----------------| |Votes | 0 | |Component/s | Compiler | |Labels | New Feature | |Assignee | None | |Priority | Medium | md5: 83f66ba9a3d3c2ca53afd381f03f06ad

Issue Description:

We should create a sil-opt driver for libfuzzer. The way that it would work is that sil-opt would load a module into memory and then use the libfuzzer input as a state machine to determine what passes to run. E.g., consider a world where sil-opt had 4 passes only. In such a case, one would continually read 2 bits from the libfuzzer provided data stream and map the 2 bit values to a pass that is then added to a pass manager. Once we run out of bits to use we would then run the pass manager on an input module.

One thing to be aware of: As far as I can remember no one has done the work today to make it really easy to clone an entire module at a time (or at least I haven't seen it done without serializing/deserializing). So as a first version I think one would read the sil/sib file into memory and then continually reparse it it in memory. Then one would see if the SILCloner is able to be used to copy an entire SILModule into a new SILModule. But to me that would be a different piece of work.

[swift-ci]

Comment by Tapan Thaker (JIRA)

Thanks @gottesmm for the task. I will try to understand & parse this and get back with my understanding. 🙂