refactor to use reg.Set

reg/set.go

@@ -0,0 +1,71 @@
+package reg
+
+// Set is a set of registers.
+type Set map[ID]Register
+
+// NewEmptySet builds an empty register set.
+func NewEmptySet() Set {
+	return Set{}
+}
+
+// NewSetFromSlice forms a set from the given register list.
+func NewSetFromSlice(rs []Register) Set {
+	s := NewEmptySet()
+	for _, r := range rs {
+		s.Add(r)
+	}
+	return s
+}
+
+// Clone returns a copy of s.
+func (s Set) Clone() Set {
+	c := NewEmptySet()
+	for _, r := range s {
+		c.Add(r)
+	}
+	return c
+}
+
+// Add r to s.
+func (s Set) Add(r Register) {
+	s[r.ID()] = r
+}
+
+// Discard removes r from s, if present.
+func (s Set) Discard(r Register) {
+	delete(s, r.ID())
+}
+
+// Update adds every register in t to s.
+func (s Set) Update(t Set) {
+	for _, r := range t {
+		s.Add(r)
+	}
+}
+
+// Difference returns the set of registers in s but not t.
+func (s Set) Difference(t Set) Set {
+	d := s.Clone()
+	d.DifferenceUpdate(t)
+	return d
+}
+
+// DifferenceUpdate removes every element of t from s.
+func (s Set) DifferenceUpdate(t Set) {
+	for _, r := range t {
+		s.Discard(r)
+	}
+}
+
+// Equals returns true if s and t contain the same registers.
+func (s Set) Equals(t Set) bool {
+	if len(s) != len(t) {
+		return false
+	}
+	for _, r := range s {
+		if _, found := t[r.ID()]; !found {
+			return false
+		}
+	}
+	return true
+}