core/portable-simd/crates/core_simd/src/
masks.rs

1//! Types and traits associated with masking elements of vectors.
2//! Types representing
3#![allow(non_camel_case_types)]
4
5#[cfg_attr(
6    not(all(target_arch = "x86_64", target_feature = "avx512f")),
7    path = "masks/full_masks.rs"
8)]
9#[cfg_attr(
10    all(target_arch = "x86_64", target_feature = "avx512f"),
11    path = "masks/bitmask.rs"
12)]
13mod mask_impl;
14
15use crate::simd::{LaneCount, Simd, SimdCast, SimdElement, SupportedLaneCount};
16use core::cmp::Ordering;
17use core::{fmt, mem};
18
19mod sealed {
20    use super::*;
21
22    /// Not only does this seal the `MaskElement` trait, but these functions prevent other traits
23    /// from bleeding into the parent bounds.
24    ///
25    /// For example, `eq` could be provided by requiring `MaskElement: PartialEq`, but that would
26    /// prevent us from ever removing that bound, or from implementing `MaskElement` on
27    /// non-`PartialEq` types in the future.
28    pub trait Sealed {
29        fn valid<const N: usize>(values: Simd<Self, N>) -> bool
30        where
31            LaneCount<N>: SupportedLaneCount,
32            Self: SimdElement;
33
34        fn eq(self, other: Self) -> bool;
35
36        fn to_usize(self) -> usize;
37        fn max_unsigned() -> u64;
38
39        type Unsigned: SimdElement;
40
41        const TRUE: Self;
42
43        const FALSE: Self;
44    }
45}
46use sealed::Sealed;
47
48/// Marker trait for types that may be used as SIMD mask elements.
49///
50/// # Safety
51/// Type must be a signed integer.
52pub unsafe trait MaskElement: SimdElement<Mask = Self> + SimdCast + Sealed {}
53
54macro_rules! impl_element {
55    { $ty:ty, $unsigned:ty } => {
56        impl Sealed for $ty {
57            #[inline]
58            fn valid<const N: usize>(value: Simd<Self, N>) -> bool
59            where
60                LaneCount<N>: SupportedLaneCount,
61            {
62                // We can't use `Simd` directly, because `Simd`'s functions call this function and
63                // we will end up with an infinite loop.
64                // Safety: `value` is an integer vector
65                unsafe {
66                    use core::intrinsics::simd;
67                    let falses: Simd<Self, N> = simd::simd_eq(value, Simd::splat(0 as _));
68                    let trues: Simd<Self, N> = simd::simd_eq(value, Simd::splat(-1 as _));
69                    let valid: Simd<Self, N> = simd::simd_or(falses, trues);
70                    simd::simd_reduce_all(valid)
71                }
72            }
73
74            #[inline]
75            fn eq(self, other: Self) -> bool { self == other }
76
77            #[inline]
78            fn to_usize(self) -> usize {
79                self as usize
80            }
81
82            #[inline]
83            fn max_unsigned() -> u64 {
84                <$unsigned>::MAX as u64
85            }
86
87            type Unsigned = $unsigned;
88
89            const TRUE: Self = -1;
90            const FALSE: Self = 0;
91        }
92
93        // Safety: this is a valid mask element type
94        unsafe impl MaskElement for $ty {}
95    }
96}
97
98impl_element! { i8, u8 }
99impl_element! { i16, u16 }
100impl_element! { i32, u32 }
101impl_element! { i64, u64 }
102impl_element! { isize, usize }
103
104/// A SIMD vector mask for `N` elements of width specified by `Element`.
105///
106/// Masks represent boolean inclusion/exclusion on a per-element basis.
107///
108/// The layout of this type is unspecified, and may change between platforms
109/// and/or Rust versions, and code should not assume that it is equivalent to
110/// `[T; N]`.
111#[repr(transparent)]
112pub struct Mask<T, const N: usize>(mask_impl::Mask<T, N>)
113where
114    T: MaskElement,
115    LaneCount<N>: SupportedLaneCount;
116
117impl<T, const N: usize> Copy for Mask<T, N>
118where
119    T: MaskElement,
120    LaneCount<N>: SupportedLaneCount,
121{
122}
123
124impl<T, const N: usize> Clone for Mask<T, N>
125where
126    T: MaskElement,
127    LaneCount<N>: SupportedLaneCount,
128{
129    #[inline]
130    fn clone(&self) -> Self {
131        *self
132    }
133}
134
135impl<T, const N: usize> Mask<T, N>
136where
137    T: MaskElement,
138    LaneCount<N>: SupportedLaneCount,
139{
140    /// Constructs a mask by setting all elements to the given value.
141    #[inline]
142    pub fn splat(value: bool) -> Self {
143        Self(mask_impl::Mask::splat(value))
144    }
145
146    /// Converts an array of bools to a SIMD mask.
147    #[inline]
148    pub fn from_array(array: [bool; N]) -> Self {
149        // SAFETY: Rust's bool has a layout of 1 byte (u8) with a value of
150        //     true:    0b_0000_0001
151        //     false:   0b_0000_0000
152        // Thus, an array of bools is also a valid array of bytes: [u8; N]
153        // This would be hypothetically valid as an "in-place" transmute,
154        // but these are "dependently-sized" types, so copy elision it is!
155        unsafe {
156            let bytes: [u8; N] = mem::transmute_copy(&array);
157            let bools: Simd<i8, N> =
158                core::intrinsics::simd::simd_ne(Simd::from_array(bytes), Simd::splat(0u8));
159            Mask::from_int_unchecked(core::intrinsics::simd::simd_cast(bools))
160        }
161    }
162
163    /// Converts a SIMD mask to an array of bools.
164    #[inline]
165    pub fn to_array(self) -> [bool; N] {
166        // This follows mostly the same logic as from_array.
167        // SAFETY: Rust's bool has a layout of 1 byte (u8) with a value of
168        //     true:    0b_0000_0001
169        //     false:   0b_0000_0000
170        // Thus, an array of bools is also a valid array of bytes: [u8; N]
171        // Since our masks are equal to integers where all bits are set,
172        // we can simply convert them to i8s, and then bitand them by the
173        // bitpattern for Rust's "true" bool.
174        // This would be hypothetically valid as an "in-place" transmute,
175        // but these are "dependently-sized" types, so copy elision it is!
176        unsafe {
177            let mut bytes: Simd<i8, N> = core::intrinsics::simd::simd_cast(self.to_int());
178            bytes &= Simd::splat(1i8);
179            mem::transmute_copy(&bytes)
180        }
181    }
182
183    /// Converts a vector of integers to a mask, where 0 represents `false` and -1
184    /// represents `true`.
185    ///
186    /// # Safety
187    /// All elements must be either 0 or -1.
188    #[inline]
189    #[must_use = "method returns a new mask and does not mutate the original value"]
190    pub unsafe fn from_int_unchecked(value: Simd<T, N>) -> Self {
191        // Safety: the caller must confirm this invariant
192        unsafe {
193            core::intrinsics::assume(<T as Sealed>::valid(value));
194            Self(mask_impl::Mask::from_int_unchecked(value))
195        }
196    }
197
198    /// Converts a vector of integers to a mask, where 0 represents `false` and -1
199    /// represents `true`.
200    ///
201    /// # Panics
202    /// Panics if any element is not 0 or -1.
203    #[inline]
204    #[must_use = "method returns a new mask and does not mutate the original value"]
205    #[track_caller]
206    pub fn from_int(value: Simd<T, N>) -> Self {
207        assert!(T::valid(value), "all values must be either 0 or -1",);
208        // Safety: the validity has been checked
209        unsafe { Self::from_int_unchecked(value) }
210    }
211
212    /// Converts the mask to a vector of integers, where 0 represents `false` and -1
213    /// represents `true`.
214    #[inline]
215    #[must_use = "method returns a new vector and does not mutate the original value"]
216    pub fn to_int(self) -> Simd<T, N> {
217        self.0.to_int()
218    }
219
220    /// Converts the mask to a mask of any other element size.
221    #[inline]
222    #[must_use = "method returns a new mask and does not mutate the original value"]
223    pub fn cast<U: MaskElement>(self) -> Mask<U, N> {
224        Mask(self.0.convert())
225    }
226
227    /// Tests the value of the specified element.
228    ///
229    /// # Safety
230    /// `index` must be less than `self.len()`.
231    #[inline]
232    #[must_use = "method returns a new bool and does not mutate the original value"]
233    pub unsafe fn test_unchecked(&self, index: usize) -> bool {
234        // Safety: the caller must confirm this invariant
235        unsafe { self.0.test_unchecked(index) }
236    }
237
238    /// Tests the value of the specified element.
239    ///
240    /// # Panics
241    /// Panics if `index` is greater than or equal to the number of elements in the vector.
242    #[inline]
243    #[must_use = "method returns a new bool and does not mutate the original value"]
244    #[track_caller]
245    pub fn test(&self, index: usize) -> bool {
246        assert!(index < N, "element index out of range");
247        // Safety: the element index has been checked
248        unsafe { self.test_unchecked(index) }
249    }
250
251    /// Sets the value of the specified element.
252    ///
253    /// # Safety
254    /// `index` must be less than `self.len()`.
255    #[inline]
256    pub unsafe fn set_unchecked(&mut self, index: usize, value: bool) {
257        // Safety: the caller must confirm this invariant
258        unsafe {
259            self.0.set_unchecked(index, value);
260        }
261    }
262
263    /// Sets the value of the specified element.
264    ///
265    /// # Panics
266    /// Panics if `index` is greater than or equal to the number of elements in the vector.
267    #[inline]
268    #[track_caller]
269    pub fn set(&mut self, index: usize, value: bool) {
270        assert!(index < N, "element index out of range");
271        // Safety: the element index has been checked
272        unsafe {
273            self.set_unchecked(index, value);
274        }
275    }
276
277    /// Returns true if any element is set, or false otherwise.
278    #[inline]
279    #[must_use = "method returns a new bool and does not mutate the original value"]
280    pub fn any(self) -> bool {
281        self.0.any()
282    }
283
284    /// Returns true if all elements are set, or false otherwise.
285    #[inline]
286    #[must_use = "method returns a new bool and does not mutate the original value"]
287    pub fn all(self) -> bool {
288        self.0.all()
289    }
290
291    /// Creates a bitmask from a mask.
292    ///
293    /// Each bit is set if the corresponding element in the mask is `true`.
294    /// If the mask contains more than 64 elements, the bitmask is truncated to the first 64.
295    #[inline]
296    #[must_use = "method returns a new integer and does not mutate the original value"]
297    pub fn to_bitmask(self) -> u64 {
298        self.0.to_bitmask_integer()
299    }
300
301    /// Creates a mask from a bitmask.
302    ///
303    /// For each bit, if it is set, the corresponding element in the mask is set to `true`.
304    /// If the mask contains more than 64 elements, the remainder are set to `false`.
305    #[inline]
306    #[must_use = "method returns a new mask and does not mutate the original value"]
307    pub fn from_bitmask(bitmask: u64) -> Self {
308        Self(mask_impl::Mask::from_bitmask_integer(bitmask))
309    }
310
311    /// Finds the index of the first set element.
312    ///
313    /// ```
314    /// # #![feature(portable_simd)]
315    /// # #[cfg(feature = "as_crate")] use core_simd::simd;
316    /// # #[cfg(not(feature = "as_crate"))] use core::simd;
317    /// # use simd::mask32x8;
318    /// assert_eq!(mask32x8::splat(false).first_set(), None);
319    /// assert_eq!(mask32x8::splat(true).first_set(), Some(0));
320    ///
321    /// let mask = mask32x8::from_array([false, true, false, false, true, false, false, true]);
322    /// assert_eq!(mask.first_set(), Some(1));
323    /// ```
324    #[inline]
325    #[must_use = "method returns the index and does not mutate the original value"]
326    pub fn first_set(self) -> Option<usize> {
327        // If bitmasks are efficient, using them is better
328        if cfg!(target_feature = "sse") && N <= 64 {
329            let tz = self.to_bitmask().trailing_zeros();
330            return if tz == 64 { None } else { Some(tz as usize) };
331        }
332
333        // To find the first set index:
334        // * create a vector 0..N
335        // * replace unset mask elements in that vector with -1
336        // * perform _unsigned_ reduce-min
337        // * check if the result is -1 or an index
338
339        let index = Simd::from_array(
340            const {
341                let mut index = [0; N];
342                let mut i = 0;
343                while i < N {
344                    index[i] = i;
345                    i += 1;
346                }
347                index
348            },
349        );
350
351        // Safety: the input and output are integer vectors
352        let index: Simd<T, N> = unsafe { core::intrinsics::simd::simd_cast(index) };
353
354        let masked_index = self.select(index, Self::splat(true).to_int());
355
356        // Safety: the input and output are integer vectors
357        let masked_index: Simd<T::Unsigned, N> =
358            unsafe { core::intrinsics::simd::simd_cast(masked_index) };
359
360        // Safety: the input is an integer vector
361        let min_index: T::Unsigned =
362            unsafe { core::intrinsics::simd::simd_reduce_min(masked_index) };
363
364        // Safety: the return value is the unsigned version of T
365        let min_index: T = unsafe { core::mem::transmute_copy(&min_index) };
366
367        if min_index.eq(T::TRUE) {
368            None
369        } else {
370            Some(min_index.to_usize())
371        }
372    }
373}
374
375// vector/array conversion
376impl<T, const N: usize> From<[bool; N]> for Mask<T, N>
377where
378    T: MaskElement,
379    LaneCount<N>: SupportedLaneCount,
380{
381    #[inline]
382    fn from(array: [bool; N]) -> Self {
383        Self::from_array(array)
384    }
385}
386
387impl<T, const N: usize> From<Mask<T, N>> for [bool; N]
388where
389    T: MaskElement,
390    LaneCount<N>: SupportedLaneCount,
391{
392    #[inline]
393    fn from(vector: Mask<T, N>) -> Self {
394        vector.to_array()
395    }
396}
397
398impl<T, const N: usize> Default for Mask<T, N>
399where
400    T: MaskElement,
401    LaneCount<N>: SupportedLaneCount,
402{
403    #[inline]
404    fn default() -> Self {
405        Self::splat(false)
406    }
407}
408
409impl<T, const N: usize> PartialEq for Mask<T, N>
410where
411    T: MaskElement + PartialEq,
412    LaneCount<N>: SupportedLaneCount,
413{
414    #[inline]
415    fn eq(&self, other: &Self) -> bool {
416        self.0 == other.0
417    }
418}
419
420impl<T, const N: usize> PartialOrd for Mask<T, N>
421where
422    T: MaskElement + PartialOrd,
423    LaneCount<N>: SupportedLaneCount,
424{
425    #[inline]
426    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
427        self.0.partial_cmp(&other.0)
428    }
429}
430
431impl<T, const N: usize> fmt::Debug for Mask<T, N>
432where
433    T: MaskElement + fmt::Debug,
434    LaneCount<N>: SupportedLaneCount,
435{
436    #[inline]
437    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
438        f.debug_list()
439            .entries((0..N).map(|i| self.test(i)))
440            .finish()
441    }
442}
443
444impl<T, const N: usize> core::ops::BitAnd for Mask<T, N>
445where
446    T: MaskElement,
447    LaneCount<N>: SupportedLaneCount,
448{
449    type Output = Self;
450    #[inline]
451    fn bitand(self, rhs: Self) -> Self {
452        Self(self.0 & rhs.0)
453    }
454}
455
456impl<T, const N: usize> core::ops::BitAnd<bool> for Mask<T, N>
457where
458    T: MaskElement,
459    LaneCount<N>: SupportedLaneCount,
460{
461    type Output = Self;
462    #[inline]
463    fn bitand(self, rhs: bool) -> Self {
464        self & Self::splat(rhs)
465    }
466}
467
468impl<T, const N: usize> core::ops::BitAnd<Mask<T, N>> for bool
469where
470    T: MaskElement,
471    LaneCount<N>: SupportedLaneCount,
472{
473    type Output = Mask<T, N>;
474    #[inline]
475    fn bitand(self, rhs: Mask<T, N>) -> Mask<T, N> {
476        Mask::splat(self) & rhs
477    }
478}
479
480impl<T, const N: usize> core::ops::BitOr for Mask<T, N>
481where
482    T: MaskElement,
483    LaneCount<N>: SupportedLaneCount,
484{
485    type Output = Self;
486    #[inline]
487    fn bitor(self, rhs: Self) -> Self {
488        Self(self.0 | rhs.0)
489    }
490}
491
492impl<T, const N: usize> core::ops::BitOr<bool> for Mask<T, N>
493where
494    T: MaskElement,
495    LaneCount<N>: SupportedLaneCount,
496{
497    type Output = Self;
498    #[inline]
499    fn bitor(self, rhs: bool) -> Self {
500        self | Self::splat(rhs)
501    }
502}
503
504impl<T, const N: usize> core::ops::BitOr<Mask<T, N>> for bool
505where
506    T: MaskElement,
507    LaneCount<N>: SupportedLaneCount,
508{
509    type Output = Mask<T, N>;
510    #[inline]
511    fn bitor(self, rhs: Mask<T, N>) -> Mask<T, N> {
512        Mask::splat(self) | rhs
513    }
514}
515
516impl<T, const N: usize> core::ops::BitXor for Mask<T, N>
517where
518    T: MaskElement,
519    LaneCount<N>: SupportedLaneCount,
520{
521    type Output = Self;
522    #[inline]
523    fn bitxor(self, rhs: Self) -> Self::Output {
524        Self(self.0 ^ rhs.0)
525    }
526}
527
528impl<T, const N: usize> core::ops::BitXor<bool> for Mask<T, N>
529where
530    T: MaskElement,
531    LaneCount<N>: SupportedLaneCount,
532{
533    type Output = Self;
534    #[inline]
535    fn bitxor(self, rhs: bool) -> Self::Output {
536        self ^ Self::splat(rhs)
537    }
538}
539
540impl<T, const N: usize> core::ops::BitXor<Mask<T, N>> for bool
541where
542    T: MaskElement,
543    LaneCount<N>: SupportedLaneCount,
544{
545    type Output = Mask<T, N>;
546    #[inline]
547    fn bitxor(self, rhs: Mask<T, N>) -> Self::Output {
548        Mask::splat(self) ^ rhs
549    }
550}
551
552impl<T, const N: usize> core::ops::Not for Mask<T, N>
553where
554    T: MaskElement,
555    LaneCount<N>: SupportedLaneCount,
556{
557    type Output = Mask<T, N>;
558    #[inline]
559    fn not(self) -> Self::Output {
560        Self(!self.0)
561    }
562}
563
564impl<T, const N: usize> core::ops::BitAndAssign for Mask<T, N>
565where
566    T: MaskElement,
567    LaneCount<N>: SupportedLaneCount,
568{
569    #[inline]
570    fn bitand_assign(&mut self, rhs: Self) {
571        self.0 = self.0 & rhs.0;
572    }
573}
574
575impl<T, const N: usize> core::ops::BitAndAssign<bool> for Mask<T, N>
576where
577    T: MaskElement,
578    LaneCount<N>: SupportedLaneCount,
579{
580    #[inline]
581    fn bitand_assign(&mut self, rhs: bool) {
582        *self &= Self::splat(rhs);
583    }
584}
585
586impl<T, const N: usize> core::ops::BitOrAssign for Mask<T, N>
587where
588    T: MaskElement,
589    LaneCount<N>: SupportedLaneCount,
590{
591    #[inline]
592    fn bitor_assign(&mut self, rhs: Self) {
593        self.0 = self.0 | rhs.0;
594    }
595}
596
597impl<T, const N: usize> core::ops::BitOrAssign<bool> for Mask<T, N>
598where
599    T: MaskElement,
600    LaneCount<N>: SupportedLaneCount,
601{
602    #[inline]
603    fn bitor_assign(&mut self, rhs: bool) {
604        *self |= Self::splat(rhs);
605    }
606}
607
608impl<T, const N: usize> core::ops::BitXorAssign for Mask<T, N>
609where
610    T: MaskElement,
611    LaneCount<N>: SupportedLaneCount,
612{
613    #[inline]
614    fn bitxor_assign(&mut self, rhs: Self) {
615        self.0 = self.0 ^ rhs.0;
616    }
617}
618
619impl<T, const N: usize> core::ops::BitXorAssign<bool> for Mask<T, N>
620where
621    T: MaskElement,
622    LaneCount<N>: SupportedLaneCount,
623{
624    #[inline]
625    fn bitxor_assign(&mut self, rhs: bool) {
626        *self ^= Self::splat(rhs);
627    }
628}
629
630macro_rules! impl_from {
631    { $from:ty  => $($to:ty),* } => {
632        $(
633        impl<const N: usize> From<Mask<$from, N>> for Mask<$to, N>
634        where
635            LaneCount<N>: SupportedLaneCount,
636        {
637            #[inline]
638            fn from(value: Mask<$from, N>) -> Self {
639                value.cast()
640            }
641        }
642        )*
643    }
644}
645impl_from! { i8 => i16, i32, i64, isize }
646impl_from! { i16 => i32, i64, isize, i8 }
647impl_from! { i32 => i64, isize, i8, i16 }
648impl_from! { i64 => isize, i8, i16, i32 }
649impl_from! { isize => i8, i16, i32, i64 }