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close #11330 sets uses optimized countSetBits #17334

Merged
merged 18 commits into from
Mar 21, 2021
88 changes: 8 additions & 80 deletions lib/pure/bitops.nim
Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,9 @@

import macros
import std/private/since
from std/private/vmutils import forwardImpl, toUnsigned



func bitnot*[T: SomeInteger](x: T): T {.magic: "BitnotI".}
## Computes the `bitwise complement` of the integer `x`.
Expand Down Expand Up @@ -58,34 +61,6 @@ macro bitxor*[T: SomeInteger](x, y: T; z: varargs[T]): T =
for extra in z:
result = newCall(fn, result, extra)

const useBuiltins = not defined(noIntrinsicsBitOpts)
const noUndefined = defined(noUndefinedBitOpts)
const useGCC_builtins = (defined(gcc) or defined(llvm_gcc) or
defined(clang)) and useBuiltins
const useICC_builtins = defined(icc) and useBuiltins
const useVCC_builtins = defined(vcc) and useBuiltins
const arch64 = sizeof(int) == 8
const useBuiltinsRotate = (defined(amd64) or defined(i386)) and
(defined(gcc) or defined(clang) or defined(vcc) or
(defined(icl) and not defined(cpp))) and useBuiltins

template toUnsigned(x: int8): uint8 = cast[uint8](x)
template toUnsigned(x: int16): uint16 = cast[uint16](x)
template toUnsigned(x: int32): uint32 = cast[uint32](x)
template toUnsigned(x: int64): uint64 = cast[uint64](x)
template toUnsigned(x: int): uint = cast[uint](x)

template forwardImpl(impl, arg) {.dirty.} =
when sizeof(x) <= 4:
when x is SomeSignedInt:
impl(cast[uint32](x.int32))
else:
impl(x.uint32)
else:
when x is SomeSignedInt:
impl(cast[uint64](x.int64))
else:
impl(x.uint64)

type BitsRange*[T] = range[0..sizeof(T)*8-1]
## A range with all bit positions for type `T`.
Expand Down Expand Up @@ -436,13 +411,12 @@ func fastlog2Nim(x: uint64): int {.inline.} =
v = v or v shr 32
result = lookup[(v * 0x03F6EAF2CD271461'u64) shr 58].int

# sets.nim cannot import bitops, but bitops can use include
# system/sets to eliminate code duplication. sets.nim defines
# countBits32 and countBits64.
import system/countbits_impl

template countSetBitsNim(n: uint32): int = countBits32(n)
template countSetBitsNim(n: uint64): int = countBits64(n)
const arch64 = sizeof(int) == 8
const useBuiltinsRotate = (defined(amd64) or defined(i386)) and
(defined(gcc) or defined(clang) or defined(vcc) or
(defined(icl) and not defined(cpp))) and useBuiltins

template parityImpl[T](value: T): int =
# formula id from: https://graphics.stanford.edu/%7Eseander/bithacks.html#ParityParallel
Expand All @@ -459,11 +433,6 @@ template parityImpl[T](value: T): int =


when useGCC_builtins:
# Returns the number of set 1-bits in value.
proc builtin_popcount(x: cuint): cint {.importc: "__builtin_popcount", cdecl.}
proc builtin_popcountll(x: culonglong): cint {.
importc: "__builtin_popcountll", cdecl.}

# Returns the bit parity in value
proc builtin_parity(x: cuint): cint {.importc: "__builtin_parity", cdecl.}
proc builtin_parityll(x: culonglong): cint {.importc: "__builtin_parityll", cdecl.}
Expand All @@ -481,14 +450,6 @@ when useGCC_builtins:
proc builtin_ctzll(x: culonglong): cint {.importc: "__builtin_ctzll", cdecl.}

elif useVCC_builtins:
# Counts the number of one bits (population count) in a 16-, 32-, or 64-byte unsigned integer.
func builtin_popcnt16(a2: uint16): uint16 {.
importc: "__popcnt16", header: "<intrin.h>".}
func builtin_popcnt32(a2: uint32): uint32 {.
importc: "__popcnt", header: "<intrin.h>".}
func builtin_popcnt64(a2: uint64): uint64 {.
importc: "__popcnt64", header: "<intrin.h>".}

# Search the mask data from most significant bit (MSB) to least significant bit (LSB) for a set bit (1).
func bitScanReverse(index: ptr culong, mask: culong): cuchar {.
importc: "_BitScanReverse", header: "<intrin.h>".}
Expand All @@ -507,15 +468,6 @@ elif useVCC_builtins:
index.int

elif useICC_builtins:

# Intel compiler intrinsics: http://fulla.fnal.gov/intel/compiler_c/main_cls/intref_cls/common/intref_allia_misc.htm
# see also: https://software.intel.com/en-us/node/523362
# Count the number of bits set to 1 in an integer a, and return that count in dst.
func builtin_popcnt32(a: cint): cint {.
importc: "_popcnt", header: "<immintrin.h>".}
func builtin_popcnt64(a: uint64): cint {.
importc: "_popcnt64", header: "<immintrin.h>".}

# Returns the number of trailing 0-bits in x, starting at the least significant bit position. If x is 0, the result is undefined.
func bitScanForward(p: ptr uint32, b: uint32): cuchar {.
importc: "_BitScanForward", header: "<immintrin.h>".}
Expand All @@ -533,37 +485,13 @@ elif useICC_builtins:
discard fnc(index.addr, v)
index.int


func countSetBits*(x: SomeInteger): int {.inline.} =
## Counts the set bits in an integer (also called `Hamming weight`:idx:).
runnableExamples:
doAssert countSetBits(0b0000_0011'u8) == 2
doAssert countSetBits(0b1010_1010'u8) == 4

# TODO: figure out if ICC support _popcnt32/_popcnt64 on platform without POPCNT.
# like GCC and MSVC
when x is SomeSignedInt:
let x = x.toUnsigned
when nimvm:
result = forwardImpl(countSetBitsNim, x)
else:
when useGCC_builtins:
when sizeof(x) <= 4: result = builtin_popcount(x.cuint).int
else: result = builtin_popcountll(x.culonglong).int
elif useVCC_builtins:
when sizeof(x) <= 2: result = builtin_popcnt16(x.uint16).int
elif sizeof(x) <= 4: result = builtin_popcnt32(x.uint32).int
elif arch64: result = builtin_popcnt64(x.uint64).int
else: result = builtin_popcnt32((x.uint64 and 0xFFFFFFFF'u64).uint32).int +
builtin_popcnt32((x.uint64 shr 32'u64).uint32).int
elif useICC_builtins:
when sizeof(x) <= 4: result = builtin_popcnt32(x.cint).int
elif arch64: result = builtin_popcnt64(x.uint64).int
else: result = builtin_popcnt32((x.uint64 and 0xFFFFFFFF'u64).cint).int +
builtin_popcnt32((x.uint64 shr 32'u64).cint).int
else:
when sizeof(x) <= 4: result = countSetBitsNim(x.uint32)
else: result = countSetBitsNim(x.uint64)
result = countSetBitsImpl(x)

func popcount*(x: SomeInteger): int {.inline.} =
## Alias for `countSetBits <#countSetBits,SomeInteger>`_ (Hamming weight).
Expand Down
17 changes: 17 additions & 0 deletions lib/std/private/vmutils.nim
Original file line number Diff line number Diff line change
@@ -0,0 +1,17 @@
template forwardImpl*(impl, arg) {.dirty.} =
when sizeof(x) <= 4:
when x is SomeSignedInt:
impl(cast[uint32](x.int32))
else:
impl(x.uint32)
else:
when x is SomeSignedInt:
impl(cast[uint64](x.int64))
else:
impl(x.uint64)

template toUnsigned*(x: int8): uint8 = cast[uint8](x)
template toUnsigned*(x: int16): uint16 = cast[uint16](x)
template toUnsigned*(x: int32): uint32 = cast[uint32](x)
template toUnsigned*(x: int64): uint64 = cast[uint64](x)
template toUnsigned*(x: int): uint = cast[uint](x)
3 changes: 1 addition & 2 deletions lib/system.nim
Original file line number Diff line number Diff line change
Expand Up @@ -2339,8 +2339,7 @@ when notJSnotNims:
when hostOS != "standalone" and hostOS != "any":
include "system/dyncalls"

import system/countbits_impl
include "system/sets"
include system/sets
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when defined(gogc):
const GenericSeqSize = (3 * sizeof(int))
Expand Down
77 changes: 73 additions & 4 deletions lib/system/countbits_impl.nim
Original file line number Diff line number Diff line change
Expand Up @@ -9,17 +9,86 @@

## Contains the used algorithms for counting bits.

proc countBits32*(n: uint32): int {.compilerproc.} =
from std/private/vmutils import forwardImpl, toUnsigned


const useBuiltins* = not defined(noIntrinsicsBitOpts)
const noUndefined* = defined(noUndefinedBitOpts)
const useGCC_builtins* = (defined(gcc) or defined(llvm_gcc) or
defined(clang)) and useBuiltins
const useICC_builtins* = defined(icc) and useBuiltins
const useVCC_builtins* = defined(vcc) and useBuiltins

template countBitsImpl(n: uint32): int =
# generic formula is from: https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
var v = uint32(n)
v = v - ((v shr 1'u32) and 0x55555555'u32)
v = (v and 0x33333333'u32) + ((v shr 2'u32) and 0x33333333'u32)
result = (((v + (v shr 4'u32) and 0xF0F0F0F'u32) * 0x1010101'u32) shr 24'u32).int
(((v + (v shr 4'u32) and 0xF0F0F0F'u32) * 0x1010101'u32) shr 24'u32).int

proc countBits64*(n: uint64): int {.compilerproc, inline.} =
template countBitsImpl(n: uint64): int =
# generic formula is from: https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
var v = uint64(n)
v = v - ((v shr 1'u64) and 0x5555555555555555'u64)
v = (v and 0x3333333333333333'u64) + ((v shr 2'u64) and 0x3333333333333333'u64)
v = (v + (v shr 4'u64) and 0x0F0F0F0F0F0F0F0F'u64)
result = ((v * 0x0101010101010101'u64) shr 56'u64).int
((v * 0x0101010101010101'u64) shr 56'u64).int


when useGCC_builtins:
# Returns the number of set 1-bits in value.
proc builtin_popcount(x: cuint): cint {.importc: "__builtin_popcount", cdecl.}
proc builtin_popcountll(x: culonglong): cint {.
importc: "__builtin_popcountll", cdecl.}

elif useVCC_builtins:
# Counts the number of one bits (population count) in a 16-, 32-, or 64-byte unsigned integer.
func builtin_popcnt16(a2: uint16): uint16 {.
importc: "__popcnt16", header: "<intrin.h>".}
func builtin_popcnt32(a2: uint32): uint32 {.
importc: "__popcnt", header: "<intrin.h>".}
func builtin_popcnt64(a2: uint64): uint64 {.
importc: "__popcnt64", header: "<intrin.h>".}

elif useICC_builtins:
# Intel compiler intrinsics: http://fulla.fnal.gov/intel/compiler_c/main_cls/intref_cls/common/intref_allia_misc.htm
# see also: https://software.intel.com/en-us/node/523362
# Count the number of bits set to 1 in an integer a, and return that count in dst.
func builtin_popcnt32(a: cint): cint {.
importc: "_popcnt", header: "<immintrin.h>".}
func builtin_popcnt64(a: uint64): cint {.
importc: "_popcnt64", header: "<immintrin.h>".}


func countSetBitsImpl*(x: SomeInteger): int {.inline.} =
## Counts the set bits in an integer (also called `Hamming weight`:idx:).
# TODO: figure out if ICC support _popcnt32/_popcnt64 on platform without POPCNT.
# like GCC and MSVC
when x is SomeSignedInt:
let x = x.toUnsigned
when nimvm:
result = forwardImpl(countBitsImpl, x)
else:
when useGCC_builtins:
when sizeof(x) <= 4: result = builtin_popcount(x.cuint).int
else: result = builtin_popcountll(x.culonglong).int
elif useVCC_builtins:
when sizeof(x) <= 2: result = builtin_popcnt16(x.uint16).int
elif sizeof(x) <= 4: result = builtin_popcnt32(x.uint32).int
elif arch64: result = builtin_popcnt64(x.uint64).int
else: result = builtin_popcnt32((x.uint64 and 0xFFFFFFFF'u64).uint32).int +
builtin_popcnt32((x.uint64 shr 32'u64).uint32).int
elif useICC_builtins:
when sizeof(x) <= 4: result = builtin_popcnt32(x.cint).int
elif arch64: result = builtin_popcnt64(x.uint64).int
else: result = builtin_popcnt32((x.uint64 and 0xFFFFFFFF'u64).cint).int +
builtin_popcnt32((x.uint64 shr 32'u64).cint).int
else:
when sizeof(x) <= 4: result = countBitsImpl(x.uint32)
else: result = countBitsImpl(x.uint64)

proc countBits32*(n: uint32): int {.compilerproc, inline.} =
result = countSetBitsImpl(n)

proc countBits64*(n: uint64): int {.compilerproc, inline.} =
result = countSetBitsImpl(n)
2 changes: 1 addition & 1 deletion lib/system/sets.nim
Original file line number Diff line number Diff line change
Expand Up @@ -8,11 +8,11 @@
#

# set handling
import system/countbits_impl
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type
NimSet = array[0..4*2048-1, uint8]

# bitops can't be imported here, therefore the code duplication.

proc cardSet(s: NimSet, len: int): int {.compilerproc, inline.} =
var i = 0
Expand Down