github.com/mh-cbon/go@v0.0.0-20160603070303-9e112a3fe4c0/src/cmd/compile/internal/gc/bv.go (about)

     1  // Copyright 2013 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 gc
     6  
     7  import "fmt"
     8  
     9  const (
    10  	WORDBITS  = 32
    11  	WORDMASK  = WORDBITS - 1
    12  	WORDSHIFT = 5
    13  )
    14  
    15  // A bvec is a bit vector.
    16  type bvec struct {
    17  	n int32    // number of bits in vector
    18  	b []uint32 // words holding bits
    19  }
    20  
    21  func bvalloc(n int32) bvec {
    22  	nword := (n + WORDBITS - 1) / WORDBITS
    23  	return bvec{n, make([]uint32, nword)}
    24  }
    25  
    26  type bulkBvec struct {
    27  	words []uint32
    28  	nbit  int32
    29  	nword int32
    30  }
    31  
    32  func bvbulkalloc(nbit int32, count int32) bulkBvec {
    33  	nword := (nbit + WORDBITS - 1) / WORDBITS
    34  	return bulkBvec{
    35  		words: make([]uint32, nword*count),
    36  		nbit:  nbit,
    37  		nword: nword,
    38  	}
    39  }
    40  
    41  func (b *bulkBvec) next() bvec {
    42  	out := bvec{b.nbit, b.words[:b.nword]}
    43  	b.words = b.words[b.nword:]
    44  	return out
    45  }
    46  
    47  // difference
    48  func bvandnot(dst bvec, src1 bvec, src2 bvec) {
    49  	for i, x := range src1.b {
    50  		dst.b[i] = x &^ src2.b[i]
    51  	}
    52  }
    53  
    54  func bveq(bv1 bvec, bv2 bvec) bool {
    55  	if bv1.n != bv2.n {
    56  		Fatalf("bvequal: lengths %d and %d are not equal", bv1.n, bv2.n)
    57  	}
    58  	for i, x := range bv1.b {
    59  		if x != bv2.b[i] {
    60  			return false
    61  		}
    62  	}
    63  	return true
    64  }
    65  
    66  func bvcopy(dst bvec, src bvec) {
    67  	for i, x := range src.b {
    68  		dst.b[i] = x
    69  	}
    70  }
    71  
    72  func bvget(bv bvec, i int32) int {
    73  	if i < 0 || i >= bv.n {
    74  		Fatalf("bvget: index %d is out of bounds with length %d\n", i, bv.n)
    75  	}
    76  	return int((bv.b[i>>WORDSHIFT] >> uint(i&WORDMASK)) & 1)
    77  }
    78  
    79  // bvnext returns the smallest index >= i for which bvget(bv, i) == 1.
    80  // If there is no such index, bvnext returns -1.
    81  func bvnext(bv bvec, i int32) int32 {
    82  	if i >= bv.n {
    83  		return -1
    84  	}
    85  
    86  	// Jump i ahead to next word with bits.
    87  	if bv.b[i>>WORDSHIFT]>>uint(i&WORDMASK) == 0 {
    88  		i &^= WORDMASK
    89  		i += WORDBITS
    90  		for i < bv.n && bv.b[i>>WORDSHIFT] == 0 {
    91  			i += WORDBITS
    92  		}
    93  	}
    94  
    95  	if i >= bv.n {
    96  		return -1
    97  	}
    98  
    99  	// Find 1 bit.
   100  	w := bv.b[i>>WORDSHIFT] >> uint(i&WORDMASK)
   101  
   102  	for w&1 == 0 {
   103  		w >>= 1
   104  		i++
   105  	}
   106  
   107  	return i
   108  }
   109  
   110  func bvisempty(bv bvec) bool {
   111  	for i := int32(0); i < bv.n; i += WORDBITS {
   112  		if bv.b[i>>WORDSHIFT] != 0 {
   113  			return false
   114  		}
   115  	}
   116  	return true
   117  }
   118  
   119  func bvnot(bv bvec) {
   120  	i := int32(0)
   121  	w := int32(0)
   122  	for ; i < bv.n; i, w = i+WORDBITS, w+1 {
   123  		bv.b[w] = ^bv.b[w]
   124  	}
   125  }
   126  
   127  // union
   128  func bvor(dst bvec, src1 bvec, src2 bvec) {
   129  	for i, x := range src1.b {
   130  		dst.b[i] = x | src2.b[i]
   131  	}
   132  }
   133  
   134  // intersection
   135  func bvand(dst bvec, src1 bvec, src2 bvec) {
   136  	for i, x := range src1.b {
   137  		dst.b[i] = x & src2.b[i]
   138  	}
   139  }
   140  
   141  func bvprint(bv bvec) {
   142  	fmt.Printf("#*")
   143  	for i := int32(0); i < bv.n; i++ {
   144  		fmt.Printf("%d", bvget(bv, i))
   145  	}
   146  }
   147  
   148  func bvresetall(bv bvec) {
   149  	for i := range bv.b {
   150  		bv.b[i] = 0
   151  	}
   152  }
   153  
   154  func bvset(bv bvec, i int32) {
   155  	if i < 0 || i >= bv.n {
   156  		Fatalf("bvset: index %d is out of bounds with length %d\n", i, bv.n)
   157  	}
   158  	mask := uint32(1 << uint(i%WORDBITS))
   159  	bv.b[i/WORDBITS] |= mask
   160  }