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compiler/math.bits: use max u64 consts

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This commit is contained in:
joe-conigliaro
2020-02-09 19:25:27 +11:00
committed by GitHub
parent 1eeee40278
commit 7583c350b8
4 changed files with 94 additions and 87 deletions
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164
vlib/math/bits/bits.v
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@ -24,53 +24,60 @@ const (
m3 = 0x00ff00ff00ff00ff // etc.
m4 = 0x0000ffff0000ffff
)
const (
// save importing math mod just for these
max_u32 = 4294967295
max_u64 = 18446744073709551615
)
// --- LeadingZeros ---
// leading_zeros8 returns the number of leading zero bits in x; the result is 8 for x == 0.
pub fn leading_zeros8(x byte) int {
return 8 - len8(x)
// leading_zeros_8 returns the number of leading zero bits in x; the result is 8 for x == 0.
pub fn leading_zeros_8(x byte) int {
return 8 - len_8(x)
}
// leading_zeros16 returns the number of leading zero bits in x; the result is 16 for x == 0.
pub fn leading_zeros16(x u16) int {
return 16 - len16(x)
// leading_zeros_16 returns the number of leading zero bits in x; the result is 16 for x == 0.
pub fn leading_zeros_16(x u16) int {
return 16 - len_16(x)
}
// leading_zeros32 returns the number of leading zero bits in x; the result is 32 for x == 0.
pub fn leading_zeros32(x u32) int {
return 32 - len32(x)
// leading_zeros_32 returns the number of leading zero bits in x; the result is 32 for x == 0.
pub fn leading_zeros_32(x u32) int {
return 32 - len_32(x)
}
// leading_zeros64 returns the number of leading zero bits in x; the result is 64 for x == 0.
pub fn leading_zeros64(x u64) int {
return 64 - len64(x)
// leading_zeros_64 returns the number of leading zero bits in x; the result is 64 for x == 0.
pub fn leading_zeros_64(x u64) int {
return 64 - len_64(x)
}
// --- TrailingZeros ---
// trailing_zeros8 returns the number of trailing zero bits in x; the result is 8 for x == 0.
pub fn trailing_zeros8(x byte) int {
return int(ntz8_tab[x])
// trailing_zeros_8 returns the number of trailing zero bits in x; the result is 8 for x == 0.
pub fn trailing_zeros_8(x byte) int {
return int(ntz_8_tab[x])
}
// trailing_zeros16 returns the number of trailing zero bits in x; the result is 16 for x == 0.
pub fn trailing_zeros16(x u16) int {
// trailing_zeros_16 returns the number of trailing zero bits in x; the result is 16 for x == 0.
pub fn trailing_zeros_16(x u16) int {
if x == 0 {
return 16
}
// see comment in trailing_zeros64
// see comment in trailing_zeros_64
return int(de_bruijn32tab[u32(x & -x) * de_bruijn32>>(32 - 5)])
}
// trailing_zeros32 returns the number of trailing zero bits in x; the result is 32 for x == 0.
pub fn trailing_zeros32(x u32) int {
// trailing_zeros_32 returns the number of trailing zero bits in x; the result is 32 for x == 0.
pub fn trailing_zeros_32(x u32) int {
if x == 0 {
return 32
}
// see comment in trailing_zeros64
// see comment in trailing_zeros_64
return int(de_bruijn32tab[(x & -x) * de_bruijn32>>(32 - 5)])
}
// trailing_zeros64 returns the number of trailing zero bits in x; the result is 64 for x == 0.
pub fn trailing_zeros64(x u64) int {
// trailing_zeros_64 returns the number of trailing zero bits in x; the result is 64 for x == 0.
pub fn trailing_zeros_64(x u64) int {
if x == 0 {
return 64
}
@ -89,23 +96,23 @@ pub fn trailing_zeros64(x u64) int {
}
// --- OnesCount ---
// ones_count8 returns the number of one bits ("population count") in x.
pub fn ones_count8(x byte) int {
return int(pop8_tab[x])
// ones_count_8 returns the number of one bits ("population count") in x.
pub fn ones_count_8(x byte) int {
return int(pop_8_tab[x])
}
// ones_count16 returns the number of one bits ("population count") in x.
pub fn ones_count16(x u16) int {
return int(pop8_tab[x>>8] + pop8_tab[x & u16(0xff)])
// ones_count_16 returns the number of one bits ("population count") in x.
pub fn ones_count_16(x u16) int {
return int(pop_8_tab[x>>8] + pop_8_tab[x & u16(0xff)])
}
// ones_count32 returns the number of one bits ("population count") in x.
pub fn ones_count32(x u32) int {
return int(pop8_tab[x>>24] + pop8_tab[x>>16 & 0xff] + pop8_tab[x>>8 & 0xff] + pop8_tab[x & u32(0xff)])
// ones_count_32 returns the number of one bits ("population count") in x.
pub fn ones_count_32(x u32) int {
return int(pop_8_tab[x>>24] + pop_8_tab[x>>16 & 0xff] + pop_8_tab[x>>8 & 0xff] + pop_8_tab[x & u32(0xff)])
}
// ones_count64 returns the number of one bits ("population count") in x.
pub fn ones_count64(x u64) int {
// ones_count_64 returns the number of one bits ("population count") in x.
pub fn ones_count_64(x u64) int {
// Implementation: Parallel summing of adjacent bits.
// See "Hacker's Delight", Chap. 5: Counting Bits.
// The following pattern shows the general approach:
@ -125,10 +132,9 @@ pub fn ones_count64(x u64) int {
// Per "Hacker's Delight", the first line can be simplified
// more, but it saves at best one instruction, so we leave
// it alone for clarity.
m := u64(1<<64) - 1
mut y := (x>>u64(1) & (m0 & m)) + (x & (m0 & m))
y = (y>>u64(2) & (m1 & m)) + (y & (m1 & m))
y = ((y>>4) + y) & (m2 & m)
mut y := (x>>u64(1) & (m0 & max_u64)) + (x & (m0 & max_u64))
y = (y>>u64(2) & (m1 & max_u64)) + (y & (m1 & max_u64))
y = ((y>>4) + y) & (m2 & max_u64)
y += y>>8
y += y>>16
y += y>>32
@ -181,87 +187,83 @@ pub fn rotate_left_64(x u64, k int) u64 {
}
// --- Reverse ---
// reverse8 returns the value of x with its bits in reversed order.
// reverse_8 returns the value of x with its bits in reversed order.
[inline]
pub fn reverse8(x byte) byte {
return rev8_tab[x]
pub fn reverse_8(x byte) byte {
return rev_8_tab[x]
}
// reverse16 returns the value of x with its bits in reversed order.
// reverse_16 returns the value of x with its bits in reversed order.
[inline]
pub fn reverse16(x u16) u16 {
return u16(rev8_tab[x>>8]) | (u16(rev8_tab[x & u16(0xff)])<<8)
pub fn reverse_16(x u16) u16 {
return u16(rev_8_tab[x>>8]) | (u16(rev_8_tab[x & u16(0xff)])<<8)
}
// reverse32 returns the value of x with its bits in reversed order.
// reverse_32 returns the value of x with its bits in reversed order.
[inline]
pub fn reverse32(x u32) u32 {
m := u64(1<<32) - 1
mut y := (x>>u32(1) & (m0 & m) | ((x & (m0 & m))<<1))
y = (y>>u32(2) & (m1 & m) | ((y & (m1 & m))<<u32(2)))
y = (y>>u32(4) & (m2 & m) | ((y & (m2 & m))<<u32(4)))
return reverse_bytes32(y)
pub fn reverse_32(x u32) u32 {
mut y := (x>>u32(1) & (m0 & max_u32) | ((x & (m0 & max_u32))<<1))
y = (y>>u32(2) & (m1 & max_u32) | ((y & (m1 & max_u32))<<u32(2)))
y = (y>>u32(4) & (m2 & max_u32) | ((y & (m2 & max_u32))<<u32(4)))
return reverse_bytes_32(y)
}
// reverse64 returns the value of x with its bits in reversed order.
// reverse_64 returns the value of x with its bits in reversed order.
[inline]
pub fn reverse64(x u64) u64 {
m := u64(1<<64) - 1
mut y := (x>>u64(1) & (m0 & m) | ((x & (m0 & m))<<1))
y = (y>>u64(2) & (m1 & m) | ((y & (m1 & m))<<2))
y = (y>>u64(4) & (m2 & m) | ((y & (m2 & m))<<4))
return reverse_bytes64(y)
pub fn reverse_64(x u64) u64 {
mut y := (x>>u64(1) & (m0 & max_u64) | ((x & (m0 & max_u64))<<1))
y = (y>>u64(2) & (m1 & max_u64) | ((y & (m1 & max_u64))<<2))
y = (y>>u64(4) & (m2 & max_u64) | ((y & (m2 & max_u64))<<4))
return reverse_bytes_64(y)
}
// --- ReverseBytes ---
// reverse_bytes16 returns the value of x with its bytes in reversed order.
// reverse_bytes_16 returns the value of x with its bytes in reversed order.
//
// This function's execution time does not depend on the inputs.
[inline]
pub fn reverse_bytes16(x u16) u16 {
pub fn reverse_bytes_16(x u16) u16 {
return (x>>8) | (x<<8)
}
// reverse_bytes32 returns the value of x with its bytes in reversed order.
// reverse_bytes_32 returns the value of x with its bytes in reversed order.
//
// This function's execution time does not depend on the inputs.
[inline]
pub fn reverse_bytes32(x u32) u32 {
m := u64(1<<32) - 1
y := (x>>u32(8) & (m3 & m) | ((x & (m3 & m))<<u32(8)))
pub fn reverse_bytes_32(x u32) u32 {
y := (x>>u32(8) & (m3 & max_u32) | ((x & (m3 & max_u32))<<u32(8)))
return (y>>16) | (y<<16)
}
// reverse_bytes64 returns the value of x with its bytes in reversed order.
// reverse_bytes_64 returns the value of x with its bytes in reversed order.
//
// This function's execution time does not depend on the inputs.
[inline]
pub fn reverse_bytes64(x u64) u64 {
m := u64(1<<64) - 1
mut y := (x>>u64(8) & (m3 & m) | ((x & (m3 & m))<<u64(8)))
y = (y>>u64(16) & (m4 & m) | ((y & (m4 & m))<<u64(16)))
pub fn reverse_bytes_64(x u64) u64 {
mut y := (x>>u64(8) & (m3 & max_u64) | ((x & (m3 & max_u64))<<u64(8)))
y = (y>>u64(16) & (m4 & max_u64) | ((y & (m4 & max_u64))<<u64(16)))
return (y>>32) | (y<<32)
}
// --- Len ---
// len8 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
pub fn len8(x byte) int {
return int(len8_tab[x])
// len_8 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
pub fn len_8(x byte) int {
return int(len_8_tab[x])
}
// len16 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
pub fn len16(x u16) int {
// len_16 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
pub fn len_16(x u16) int {
mut y := x
mut n := 0
if y >= 1<<8 {
y >>= 8
n = 8
}
return n + int(len8_tab[y])
return n + int(len_8_tab[y])
}
// len32 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
pub fn len32(x u32) int {
// len_32 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
pub fn len_32(x u32) int {
mut y := x
mut n := 0
if y >= 1<<16 {
@ -272,11 +274,11 @@ pub fn len32(x u32) int {
y >>= 8
n += 8
}
return n + int(len8_tab[y])
return n + int(len_8_tab[y])
}
// len64 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
pub fn len64(x u64) int {
// len_64 returns the minimum number of bits required to represent x; the result is 0 for x == 0.
pub fn len_64(x u64) int {
mut y := x
mut n := 0
if y >= u64(1)<<u64(32) {
@ -291,6 +293,6 @@ pub fn len64(x u64) int {
y >>= 8
n += 8
}
return n + int(len8_tab[y])
return n + int(len_8_tab[y])
}