Granular dependency relation

[bartoszmodelski]

DPOR algorithms schedule race reversals based on depedency relation, which is a binary relation on transitions indicating whether two operations are racing or not. Currently, we treat any two accesses on the same variable (by two different domains) as a race but this is simplistic. In many cases such accesses do commute, e.g.: two reads, two incrs, two failed cases, two writes writing the same value.

This PR implements the first part: commutative reads (get, failed CAS). There are two main changes in this PR:

• Happens-before is made more abstract to dpor.
  • This includes a change to be more mindful about detecting reversible races. In particular, we don't want to recognize two transitively-dependent operations as a race.
• Happens-before is refined to exclude pairs of read-only operations.
  • This requires some extra processing as happens-before now forms a graph rather than list.
  • This includes a change to capture effect of CASes. I did a lot of testing with the test generator and some manually crafted cas tests vs nidhugg targeting this in particular.

Furthermore, I've slid in a 2-line optimization I've noticed in nidhugg. Currently, we schedule one of the initials is none of them is present in the backtrack (i.e. an initial is not scheduled). I've noticed an optimization in nidhugg, which goes one step further - also checks whether sleep set contains any of the initials (i.e. an initials is ignored, thus its been processed before).

Results

Lockfree

Lockfree tests ws_deque_dscheck, mpsc_queue_dscheck, michael_scott_queue_dscheck, Spsc_queue_dscheck, treiber_stack_dscheck vs source sets branch.

PR#18:
$ time dune test
dune test  4,10s user 0,07s system 114% cpu 3,630 total

granular-dependency-relation:
$ time dune test
dune test  0,19s user 0,03s system 124% cpu 0,179 total

Eio

Eio tests make dscheck vs optims branch.

PR#3: 
$ time make dscheck
make dscheck  1128,60s user 1,39s system 99% cpu 18:50,23 total

granular-dependency-relation
$ time make dscheck
make dscheck  228,93s user 0,45s system 99% cpu 3:49,43 total

[lyrm]

The merged conflicts should be resolved. It everything is green, this can be merged.