1// Copyright 2015 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package ssa
6
7import "cmd/internal/src"
8
9// from https://research.swtch.com/sparse
10// in turn, from Briggs and Torczon
11
12type sparseEntry struct {
13	key ID
14	val int32
15	aux src.XPos
16}
17
18type sparseMap struct {
19	dense  []sparseEntry
20	sparse []int32
21}
22
23// newSparseMap returns a sparseMap that can map
24// integers between 0 and n-1 to int32s.
25func newSparseMap(n int) *sparseMap {
26	return &sparseMap{dense: nil, sparse: make([]int32, n)}
27}
28
29func (s *sparseMap) cap() int {
30	return len(s.sparse)
31}
32
33func (s *sparseMap) size() int {
34	return len(s.dense)
35}
36
37func (s *sparseMap) contains(k ID) bool {
38	i := s.sparse[k]
39	return i < int32(len(s.dense)) && s.dense[i].key == k
40}
41
42// get returns the value for key k, or -1 if k does
43// not appear in the map.
44func (s *sparseMap) get(k ID) int32 {
45	i := s.sparse[k]
46	if i < int32(len(s.dense)) && s.dense[i].key == k {
47		return s.dense[i].val
48	}
49	return -1
50}
51
52func (s *sparseMap) set(k ID, v int32, a src.XPos) {
53	i := s.sparse[k]
54	if i < int32(len(s.dense)) && s.dense[i].key == k {
55		s.dense[i].val = v
56		s.dense[i].aux = a
57		return
58	}
59	s.dense = append(s.dense, sparseEntry{k, v, a})
60	s.sparse[k] = int32(len(s.dense)) - 1
61}
62
63// setBit sets the v'th bit of k's value, where 0 <= v < 32
64func (s *sparseMap) setBit(k ID, v uint) {
65	if v >= 32 {
66		panic("bit index too large.")
67	}
68	i := s.sparse[k]
69	if i < int32(len(s.dense)) && s.dense[i].key == k {
70		s.dense[i].val |= 1 << v
71		return
72	}
73	s.dense = append(s.dense, sparseEntry{k, 1 << v, src.NoXPos})
74	s.sparse[k] = int32(len(s.dense)) - 1
75}
76
77func (s *sparseMap) remove(k ID) {
78	i := s.sparse[k]
79	if i < int32(len(s.dense)) && s.dense[i].key == k {
80		y := s.dense[len(s.dense)-1]
81		s.dense[i] = y
82		s.sparse[y.key] = i
83		s.dense = s.dense[:len(s.dense)-1]
84	}
85}
86
87func (s *sparseMap) clear() {
88	s.dense = s.dense[:0]
89}
90
91func (s *sparseMap) contents() []sparseEntry {
92	return s.dense
93}
94