libgo/go/runtime/internal/sys/intrinsics.go

   1 // Copyright 2016 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 sys
   6
   7 //extern __builtin_ctz
   8 func builtinCtz32(uint32) int32
   9
  10 //extern __builtin_ctzll
  11 func builtinCtz64(uint64) int32
  12
  13 //go:nosplit
  14
  15 // Ctz64 counts trailing (low-order) zeroes,
  16 // and if all are zero, then 64.
  17 func Ctz64(x uint64) int {
  18         if x == 0 {
  19                 return 64
  20         }
  21         return int(builtinCtz64(x))
  22 }
  23
  24 //go:nosplit
  25
  26 // Ctz32 counts trailing (low-order) zeroes,
  27 // and if all are zero, then 32.
  28 func Ctz32(x uint32) int {
  29         if x == 0 {
  30                 return 32
  31         }
  32         return int(builtinCtz32(x))
  33 }
  34
  35 // Ctz8 returns the number of trailing zero bits in x; the result is 8 for x == 0.
  36 func Ctz8(x uint8) int {
  37         return int(ntz8tab[x])
  38 }
  39
  40 var ntz8tab = [256]uint8{
  41         0x08, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
  42         0x04, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
  43         0x05, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
  44         0x04, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
  45         0x06, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
  46         0x04, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
  47         0x05, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
  48         0x04, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
  49         0x07, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
  50         0x04, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
  51         0x05, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
  52         0x04, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
  53         0x06, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
  54         0x04, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
  55         0x05, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
  56         0x04, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00, 0x03, 0x00, 0x01, 0x00, 0x02, 0x00, 0x01, 0x00,
  57 }
  58
  59 //extern __builtin_bswap64
  60 func bswap64(uint64) uint64
  61
  62 //go:nosplit
  63
  64 // Bswap64 returns its input with byte order reversed
  65 // 0x0102030405060708 -> 0x0807060504030201
  66 func Bswap64(x uint64) uint64 {
  67         return bswap64(x)
  68 }
  69
  70 //extern __builtin_bswap32
  71 func bswap32(uint32) uint32
  72
  73 //go:nosplit
  74
  75 // Bswap32 returns its input with byte order reversed
  76 // 0x01020304 -> 0x04030201
  77 func Bswap32(x uint32) uint32 {
  78         return bswap32(x)
  79 }