Code for debugging the dep-graph.
This module defines the
DepNode type which the compiler uses to represent
nodes in the dependency graph. A
DepNode consists of a
specifies the kind of thing it represents, like a piece of HIR, MIR, etc)
Fingerprint, a 128 bit hash value the exact meaning of which
depends on the node’s
DepKind. Together, the kind and the fingerprint
fully identify a dependency node, even across multiple compilation sessions.
In other words, the value of the fingerprint does not depend on anything
that is specific to a given compilation session, like an unpredictable
interning key (e.g., NodeId, DefId, Symbol) or the numeric value of a
pointer. The concept behind this could be compared to how git commit hashes
uniquely identify a given commit and has a few advantages:
The data that we will serialize and deserialize.
Data for use when recompiling the current crate.
A “work product” is an intermediate result that we save into the incremental directory for later re-use. The primary example are the object files that we save for each partition at code generation time.
A “work product” corresponds to a
.o (or other) file that we
save in between runs. These IDs do not have a
DefId but rather
some independent path or string that persists between runs without
the need to be mapped or unmapped. (This ensures we can serialize
them even in the absence of a tcx.)