Source file src/pkg/cmd/compile/internal/ssa/sparsemap.go

     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	
     5	package ssa
     6	
     7	import "cmd/internal/src"
     8	
     9	// from https://research.swtch.com/sparse
    10	// in turn, from Briggs and Torczon
    11	
    12	type sparseEntry struct {
    13		key ID
    14		val int32
    15		aux src.XPos
    16	}
    17	
    18	type 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.
    25	func newSparseMap(n int) *sparseMap {
    26		return &sparseMap{dense: nil, sparse: make([]int32, n)}
    27	}
    28	
    29	func (s *sparseMap) cap() int {
    30		return len(s.sparse)
    31	}
    32	
    33	func (s *sparseMap) size() int {
    34		return len(s.dense)
    35	}
    36	
    37	func (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.
    44	func (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	
    52	func (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
    64	func (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	
    77	func (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	
    87	func (s *sparseMap) clear() {
    88		s.dense = s.dense[:0]
    89	}
    90	
    91	func (s *sparseMap) contents() []sparseEntry {
    92		return s.dense
    93	}
    94	

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