Simplify lazy DefPathHash decoding by using an on-disk hash table.
This PR simplifies the logic around mapping `DefPathHash` values encountered during incremental compilation to valid `DefId`s in the current session. It is able to do so by using an on-disk hash table encoding that allows for looking up values directly, i.e. without deserializing the entire table.
The main simplification comes from not having to keep track of `DefPathHashes` being used during the compilation session.
Specify a log level in tracing instrument macro explicitly.
Additionally reduce the used log level from a default info level to a
debug level (all of those appear to be developer oriented logs, so there
should be no need to include them in release builds).
`with_taks_impl` is only called from `with_eval_always_task` and
`with_task` . The former is only used in query invocation, while the
latter is also used to start the `tcx` and to trigger codegen.
This move should not change significantly the number of calls to this
assertion.
Found with https://github.com/est31/warnalyzer.
Dubious changes:
- Is anyone else using rustc_apfloat? I feel weird completely deleting
x87 support.
- Maybe some of the dead code in rustc_data_structures, in case someone
wants to use it in the future?
- Don't change rustc_serialize
I plan to scrap most of the json module in the near future (see
https://github.com/rust-lang/compiler-team/issues/418) and fixing the
tests needed more work than I expected.
TODO: check if any of the comments on the deleted code should be kept.
Serialize dependency graph directly from DepGraph
Reduce memory usage by serializing dep graph directly from `DepGraph`,
rather than copying it into `SerializedDepGraph` and serializing that.
Reduce memory consumption by sharing the previous dependency graph's
edges with the current graph when it is known to be valid to do so. It
is known to be valid whenever we mark a node green because all of its
dependencies were green. It is *not* known to be valid when we mark a
node green because we re-executed its query and its result was the same
as in the previous compilation session. In that case, the dependency set
might have changed (we don't try to determine whether or not it changed
and whether or not we can share).
Reduce memory consumption by taking advantage of red/green algorithm
properties to share the previous dependency graph's node data with the
current graph instead of storing node data redundantly. Red nodes can
share the `DepNode`, and green nodes can share the `DepNode` and
`Fingerprint`. Edges will be shared when possible in a later change.
