cmd/compile: rename poset method dominates to reaches
The partially ordered set uses a method named 'dominates' to determine whether
two nodes are partially ordered. Dominates does a depth-first search of the
DAG, beginning at the source node, and returns true as soon as it finds a path
to the target node. In the context of the forest-of-DAGs that makes up the
poset, dominates is not necessarily checking dominance, but is checking
reachability. See the issue tracker for a more detailed discussion of the
difference.
Fortunately, reachability is logically correct everywhere dominates is currently
used in poset.go. Reachability within a DAG is sufficient to establish the
partial ordering (source < target).
This CL changes the name of the method (dominates -> reaches) and updates
all the comments in the file accordingly.
Fixes #33971.
Change-Id: Ia3a34f7b14b363801d75b05099cfc686035f7d96
Reviewed-on: https://go-review.googlesource.com/c/go/+/192617 Reviewed-by: Giovanni Bajo <rasky@develer.com>
Run-TryBot: Giovanni Bajo <rasky@develer.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>