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cmd/compile: adjust top-level documentation of poset

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Change-Id: I29e24c734e5e0041008771c805a0285aac3e02e5
Reviewed-on: https://go-review.googlesource.com/c/go/+/196598
Reviewed-by: David Chase <drchase@google.com>
This commit is contained in:
Giovanni Bajo 2019-09-19 22:34:06 +02:00
parent 1658263bbf
commit 740d2c8c22
1 changed files with 7 additions and 7 deletions
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14
src/cmd/compile/internal/ssa/poset.go
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@ -106,17 +106,17 @@ type posetNode struct {
// order so that if we know that A<B<C and later learn that A==D, Ordered will return
// true for D<C.
//
// It is also possible to record inequality relations between nodes with SetNonEqual;
// non-equality relations are not transitive, but they can still be useful: for instance
// if we know that A<=B and later we learn that A!=B, we can deduce that A<B.
// NonEqual can be used to check whether it is known that the nodes are different, either
// because SetNonEqual was called before, or because we know that they are strictly ordered.
//
// poset will refuse to record new relations that contradict existing relations:
// for instance if A<B<C, calling SetOrder for C<A will fail returning false; also
// calling SetEqual for C==A will fail.
//
// It is also possible to record inequality relations between nodes with SetNonEqual;
// given that non-equality is not transitive, the only effect is that a later call
// to SetEqual for the same values will fail. NonEqual checks whether it is known that
// the nodes are different, either because SetNonEqual was called before, or because
// we know that they are strictly ordered.
//
// It is implemented as a forest of DAGs; in each DAG, if there is a path (directed)
// poset is implemented as a forest of DAGs; in each DAG, if there is a path (directed)
// from node A to B, it means that A<B (or A<=B). Equality is represented by mapping
// two SSA values to the same DAG node; when a new equality relation is recorded
// between two existing nodes,the nodes are merged, adjusting incoming and outgoing edges.