mod.rs.html -- source
Description: Source to the Rust file `src/libstd/../stdsimd/stdsimd/mod.rs`.
Keywords: rust, rustlang, rust-lang

      1
      2
      3
      4
      5
      6
      7
      8
      9
     10
     11
     12
     13
     14
     15
     16
     17
     18
     19
     20
     21
     22
     23
     24
     25
     26
     27
     28
     29
     30
     31
     32
     33
     34
     35
     36
     37
     38
     39
     40
     41
     42
     43
     44
     45
     46
     47
     48
     49
     50
     51
     52
     53
     54
     55
     56
     57
     58
     59
     60
     61
     62
     63
     64
     65
     66
     67
     68
     69
     70
     71
     72
     73
     74
     75
     76
     77
     78
     79
     80
     81
     82
     83
     84
     85
     86
     87
     88
     89
     90
     91
     92
     93
     94
     95
     96
     97
     98
     99
    100
    101
    102
    103
    104
    105
    106
    107
    108
    109
    110
    111
    112
    113
    114
    115
    116
    117
    118
    119
    120
    121
    122
    123
    124
    125
    126
    127
    128
    129
    130
    131
    132
    133
    134
    135
    136
    137
    138
    139
    140
    141
    142
    143
    144
    145
    146
    147
    148
    149
    150
    151
    152
    153
    154
    155
    156
    157
    158
    159
    160
    161
    162
    163
    164
    165
    166
    167
    168
    169
    170
    171
    172
    173
    174
    175
    176
    177
    178
    179
    180
    181
    182
    183
    184
    185
    186
    187
    188
    189
    190
    191
    192
    193
    194
    195
    196
    197
    198
    199
    200
    201
    202
    203
    204
    205
    206
    207
    208
    209
    210
    211
    212
    213
    214
    215
    216
    217
    218
    219
    220
    221
    222
    223
    224
    225
    226
    227
    228
    229
    230
    231
    232
    233
    234
    235
    236
    237
    238
    239
    240
    241
    242
    243
    244
    245
    246
    247
    248
    249
    250
    251
    252
    253
    254
    255
    256
    257
    258
    259
    260
    261
    262
    263
    264
    265
    266
    267
    268
    269
    270
    271
    272
    273
    274
    275
    276
    277
    278
    279
    280
    281
    282
    283
    284
    285
    286
    287
    288
    289
    290
    291
    292
    293
    294
    295
    296
    297
    298
    299
    300
    301
    302
    303
    304
    305
    306
    307
    308
    309
    310
    311
    312
    313
    314
    315
    316
    317
    318
    319
    320
    321
    322
    323
    324
    325
    326
    327
    328
    329
    330
    331
    332
    333
    334
    335
    336
    337
    338
    339
    340
    341
    342
    343
    344
    345
    346
    347
    348
    349
    350
    351
    352
    353
    354
    355
    356
    357
    358
    359
    360
    361
    362
    363
    364
    365
    366
    367
    368
    369
    370
    371
    372
    373
    374
    375
    376
    377
    378
    379
    380
    381
    382
    383
    384
    385
    386
    387
    388
    389
    390
    391
    392
    393
    394
    395
    396
    397
    398
    399
    400
    401
    402
    403
    404
    405
    406
    407
    408
    409
    410
    411
    412
    413
    414
    415
    416
    417
    418
    419
    420
    421
    422
    423
    424
    425
    426
    427
    428
    429
    430
    431
    432
    433
    434
    435
    436
    437
    438
    439
    440
    441
    442
    443
    444
    445
    446
    447
    448
    449
    450
    451
    452
    453
    454
    455
    456
    457
    458
    459
    460
    461
    462
    463
    464
    465
    466
    467
    468
    469
    470
    471
    472
    473
    474
    475
    476
    477
    478
    479
    480
    481
    482
    483
    484
    485
    486
    487
    488
    489
    490
    491
    492
    493
    494
    495
    496
    497
    498
    499
    500
    501
    502
    503
    504
    505
    506
    507
    508
    509
    510
    511
    512
    513
    514
    515
    516
    517
    518
    519
    520
    521

    //! `stdsimd`

    /// SIMD and vendor intrinsics module.
    ///
    /// This module is intended to be the gateway to architecture-specific
    /// intrinsic functions, typically related to SIMD (but not always!). Each
    /// architecture that Rust compiles to may contain a submodule here, which
    /// means that this is not a portable module! If you're writing a portable
    /// library take care when using these APIs!
    ///
    /// Under this module you'll find an architecture-named module, such as
    /// `x86_64`. Each `#[cfg(target_arch)]` that Rust can compile to may have a
    /// module entry here, only present on that particular target. For example the
    /// `i686-pc-windows-msvc` target will have an `x86` module here, whereas
    /// `x86_64-pc-windows-msvc` has `x86_64`.
    ///
    /// [rfc]: https://github.com/rust-lang/rfcs/pull/2325
    /// [tracked]: https://github.com/rust-lang/rust/issues/48556
    ///
    /// # Overview
    ///
    /// This module exposes vendor-specific intrinsics that typically correspond to
    /// a single machine instruction. These intrinsics are not portable: their
    /// availability is architecture-dependent, and not all machines of that
    /// architecture might provide the intrinsic.
    ///
    /// The `arch` module is intended to be a low-level implementation detail for
    /// higher-level APIs. Using it correctly can be quite tricky as you need to
    /// ensure at least a few guarantees are upheld:
    ///
    /// * The correct architecture's module is used. For example the `arm` module
    ///   isn't available on the `x86_64-unknown-linux-gnu` target. This is
    ///   typically done by ensuring that `#[cfg]` is used appropriately when using
    ///   this module.
    /// * The CPU the program is currently running on supports the function being
    ///   called. For example it is unsafe to call an AVX2 function on a CPU that
    ///   doesn't actually support AVX2.
    ///
    /// As a result of the latter of these guarantees all intrinsics in this module
    /// are `unsafe` and extra care needs to be taken when calling them!
    ///
    /// # CPU Feature Detection
    ///
    /// In order to call these APIs in a safe fashion there's a number of
    /// mechanisms available to ensure that the correct CPU feature is available
    /// to call an intrinsic. Let's consider, for example, the `_mm256_add_epi64`
    /// intrinsics on the `x86` and `x86_64` architectures. This function requires
    /// the AVX2 feature as [documented by Intel][intel-dox] so to correctly call
    /// this function we need to (a) guarantee we only call it on `x86`/`x86_64`
    /// and (b) ensure that the CPU feature is available
    ///
    /// [intel-dox]: https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_mm256_add_epi64&expand=100
    ///
    /// ## Static CPU Feature Detection
    ///
    /// The first option available to us is to conditionally compile code via the
    /// `#[cfg]` attribute. CPU features correspond to the `target_feature` cfg
    /// available, and can be used like so:
    ///
    /// ```ignore
    /// #[cfg(
    ///     all(
    ///         any(target_arch = "x86", target_arch = "x86_64"),
    ///         target_feature = "avx2"
    ///     )
    /// )]
    /// fn foo() {
    ///     #[cfg(target_arch = "x86")]
    ///     use std::arch::x86::_mm256_add_epi64;
    ///     #[cfg(target_arch = "x86_64")]
    ///     use std::arch::x86_64::_mm256_add_epi64;
    ///
    ///     unsafe {
    ///         _mm256_add_epi64(...);
    ///     }
    /// }
    /// ```
    ///
    /// Here we're using `#[cfg(target_feature = "avx2")]` to conditionally compile
    /// this function into our module. This means that if the `avx2` feature is
    /// *enabled statically* then we'll use the `_mm256_add_epi64` function at
    /// runtime. The `unsafe` block here can be justified through the usage of
    /// `#[cfg]` to only compile the code in situations where the safety guarantees
    /// are upheld.
    ///
    /// Statically enabling a feature is typically done with the `-C
    /// target-feature` or `-C target-cpu` flags to the compiler. For example if
    /// your local CPU supports AVX2 then you can compile the above function with:
    ///
    /// ```sh
    /// $ RUSTFLAGS='-C target-cpu=native' cargo build
    /// ```
    ///
    /// Or otherwise you can specifically enable just the AVX2 feature:
    ///
    /// ```sh
    /// $ RUSTFLAGS='-C target-feature=+avx2' cargo build
    /// ```
    ///
    /// Note that when you compile a binary with a particular feature enabled it's
    /// important to ensure that you only run the binary on systems which satisfy
    /// the required feature set.
    ///
    /// ## Dynamic CPU Feature Detection
    ///
    /// Sometimes statically dispatching isn't quite what you want. Instead you
    /// might want to build a portable binary that runs across a variety of CPUs,
    /// but at runtime it selects the most optimized implementation available. This
    /// allows you to build a "least common denominator" binary which has certain
    /// sections more optimized for different CPUs.
    ///
    /// Taking our previous example from before, we're going to compile our binary
    /// *without* AVX2 support, but we'd like to enable it for just one function.
    /// We can do that in a manner like:
    ///
    /// ```ignore
    /// fn foo() {
    ///     #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
    ///     {
    ///         if is_x86_feature_detected!("avx2") {
    ///             return unsafe { foo_avx2() };
    ///         }
    ///     }
    ///
    ///     // fallback implementation without using AVX2
    /// }
    ///
    /// #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
    /// #[target_feature(enable = "avx2")]
    /// unsafe fn foo_avx2() {
    ///     #[cfg(target_arch = "x86")]
    ///     use std::arch::x86::_mm256_add_epi64;
    ///     #[cfg(target_arch = "x86_64")]
    ///     use std::arch::x86_64::_mm256_add_epi64;
    ///
    ///     _mm256_add_epi64(...);
    /// }
    /// ```
    ///
    /// There's a couple of components in play here, so let's go through them in
    /// detail!
    ///
    /// * First up we notice the `is_x86_feature_detected!` macro. Provided by
    ///   the standard library, this macro will perform necessary runtime detection
    ///   to determine whether the CPU the program is running on supports the
    ///   specified feature. In this case the macro will expand to a boolean
    /// expression evaluating to whether the local CPU has the AVX2 feature or
    /// not.
    ///
    ///   Note that this macro, like the `arch` module, is platform-specific. For
    ///   example calling `is_x86_feature_detected!("avx2")` on ARM will be a
    ///   compile time error. To ensure we don't hit this error a statement level
    ///   `#[cfg]` is used to only compile usage of the macro on `x86`/`x86_64`.
    ///
    /// * Next up we see our AVX2-enabled function, `foo_avx2`. This function is
    ///   decorated with the `#[target_feature]` attribute which enables a CPU
    ///   feature for just this one function. Using a compiler flag like `-C
    ///   target-feature=+avx2` will enable AVX2 for the entire program, but using
    ///   an attribute will only enable it for the one function. Usage of the
    ///   `#[target_feature]` attribute currently requires the function to also be
    ///   `unsafe`, as we see here. This is because the function can only be
    ///   correctly called on systems which have the AVX2 (like the intrinsics
    ///   themselves).
    ///
    /// And with all that we should have a working program! This program will run
    /// across all machines and it'll use the optimized AVX2 implementation on
    /// machines where support is detected.
    ///
    /// # Ergonomics
    ///
    /// It's important to note that using the `arch` module is not the easiest
    /// thing in the world, so if you're curious to try it out you may want to
    /// brace yourself for some wordiness!
    ///
    /// The primary purpose of this module is to enable stable crates on crates.io
    /// to build up much more ergonomic abstractions which end up using SIMD under
    /// the hood. Over time these abstractions may also move into the standard
    /// library itself, but for now this module is tasked with providing the bare
    /// minimum necessary to use vendor intrinsics on stable Rust.
    ///
    /// # Other architectures
    ///
    /// This documentation is only for one particular architecture, you can find
    /// others at:
    ///
    /// * [`x86`]
    /// * [`x86_64`]
    /// * [`arm`]
    /// * [`aarch64`]
    /// * [`mips`]
    /// * [`mips64`]
    /// * [`powerpc`]
    /// * [`powerpc64`]
    /// * [`nvptx`]
    /// * [`wasm32`]
    ///
    /// [`x86`]: x86/index.html
    /// [`x86_64`]: x86_64/index.html
    /// [`arm`]: arm/index.html
    /// [`aarch64`]: aarch64/index.html
    /// [`mips`]: mips/index.html
    /// [`mips64`]: mips64/index.html
    /// [`powerpc`]: powerpc/index.html
    /// [`powerpc64`]: powerpc64/index.html
    /// [`nvptx`]: nvptx/index.html
    /// [`wasm32`]: wasm32/index.html
    ///
    /// # Examples
    ///
    /// First let's take a look at not actually using any intrinsics but instead
    /// using LLVM's auto-vectorization to produce optimized vectorized code for
    /// AVX2 and also for the default platform.
    ///
    /// ```rust
    /// # #![cfg_attr(not(dox),feature(cfg_target_feature, target_feature, stdsimd))]
    /// # #[cfg(not(dox))]
    /// # #[macro_use]
    /// # extern crate stdsimd;
    ///
    /// fn main() {
    ///     let mut dst = [0];
    ///     add_quickly(&[1], &[2], &mut dst);
    ///     assert_eq!(dst[0], 3);
    /// }
    ///
    /// fn add_quickly(a: &[u8], b: &[u8], c: &mut [u8]) {
    ///     #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
    ///     {
    ///         // Note that this `unsafe` block is safe because we're testing
    ///         // that the `avx2` feature is indeed available on our CPU.
    ///         if is_x86_feature_detected!("avx2") {
    ///             return unsafe { add_quickly_avx2(a, b, c) };
    ///         }
    ///     }
    ///
    ///     add_quickly_fallback(a, b, c)
    /// }
    ///
    /// #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
    /// #[target_feature(enable = "avx2")]
    /// unsafe fn add_quickly_avx2(a: &[u8], b: &[u8], c: &mut [u8]) {
    ///     add_quickly_fallback(a, b, c) // the function below is inlined here
    /// }
    ///
    /// fn add_quickly_fallback(a: &[u8], b: &[u8], c: &mut [u8]) {
    ///     for ((a, b), c) in a.iter().zip(b).zip(c) {
    ///         *c = *a + *b;
    ///     }
    /// }
    /// ```
    ///
    /// Next up let's take a look at an example of manually using intrinsics. Here
    /// we'll be using SSE4.1 features to implement hex encoding.
    ///
    /// ```
    /// # #![cfg_attr(not(dox),feature(cfg_target_feature, target_feature, stdsimd))]
    /// # #![cfg_attr(not(dox), no_std)]
    /// # #[cfg(not(dox))]
    /// # extern crate std as real_std;
    /// # #[cfg(not(dox))]
    /// # #[macro_use]
    /// # extern crate stdsimd as std;
    ///
    /// fn main() {
    ///     let mut dst = [0; 32];
    ///     hex_encode(b"\x01\x02\x03", &mut dst);
    ///     assert_eq!(&dst[..6], b"010203");
    ///
    ///     let mut src = [0; 16];
    ///     for i in 0..16 {
    ///         src[i] = (i + 1) as u8;
    ///     }
    ///     hex_encode(&src, &mut dst);
    ///     assert_eq!(&dst, b"0102030405060708090a0b0c0d0e0f10");
    /// }
    ///
    /// pub fn hex_encode(src: &[u8], dst: &mut [u8]) {
    ///     let len = src.len().checked_mul(2).unwrap();
    ///     assert!(dst.len() >= len);
    ///
    ///     #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
    ///     {
    ///         if is_x86_feature_detected!("sse4.1") {
    ///             return unsafe { hex_encode_sse41(src, dst) };
    ///         }
    ///     }
    ///
    ///     hex_encode_fallback(src, dst)
    /// }
    ///
    /// // translated from
    /// // https://github.com/Matherunner/bin2hex-sse/blob/master/base16_sse4.cpp
    /// #[target_feature(enable = "sse4.1")]
    /// #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
    /// unsafe fn hex_encode_sse41(mut src: &[u8], dst: &mut [u8]) {
    ///     #[cfg(target_arch = "x86")]
    ///     use std::arch::x86::*;
    ///     #[cfg(target_arch = "x86_64")]
    ///     use std::arch::x86_64::*;
    ///
    ///     let ascii_zero = _mm_set1_epi8(b'0' as i8);
    ///     let nines = _mm_set1_epi8(9);
    ///     let ascii_a = _mm_set1_epi8((b'a' - 9 - 1) as i8);
    ///     let and4bits = _mm_set1_epi8(0xf);
    ///
    ///     let mut i = 0_isize;
    ///     while src.len() >= 16 {
    ///         let invec = _mm_loadu_si128(src.as_ptr() as *const _);
    ///
    ///         let masked1 = _mm_and_si128(invec, and4bits);
    ///         let masked2 = _mm_and_si128(_mm_srli_epi64(invec, 4), and4bits);
    ///
    ///         // return 0xff corresponding to the elements > 9, or 0x00 otherwise
    ///         let cmpmask1 = _mm_cmpgt_epi8(masked1, nines);
    ///         let cmpmask2 = _mm_cmpgt_epi8(masked2, nines);
    ///
    ///         // add '0' or the offset depending on the masks
    ///         let masked1 = _mm_add_epi8(
    ///             masked1,
    ///             _mm_blendv_epi8(ascii_zero, ascii_a, cmpmask1),
    ///         );
    ///         let masked2 = _mm_add_epi8(
    ///             masked2,
    ///             _mm_blendv_epi8(ascii_zero, ascii_a, cmpmask2),
    ///         );
    ///
    ///         // interleave masked1 and masked2 bytes
    ///         let res1 = _mm_unpacklo_epi8(masked2, masked1);
    ///         let res2 = _mm_unpackhi_epi8(masked2, masked1);
    ///
    ///         _mm_storeu_si128(dst.as_mut_ptr().offset(i * 2) as *mut _, res1);
    ///         _mm_storeu_si128(
    ///             dst.as_mut_ptr().offset(i * 2 + 16) as *mut _,
    ///             res2,
    ///         );
    ///         src = &src[16..];
    ///         i += 16;
    ///     }
    ///
    ///     let i = i as usize;
    ///     hex_encode_fallback(src, &mut dst[i * 2..]);
    /// }
    ///
    /// fn hex_encode_fallback(src: &[u8], dst: &mut [u8]) {
    ///     fn hex(byte: u8) -> u8 {
    ///         static TABLE: &[u8] = b"0123456789abcdef";
    ///         TABLE[byte as usize]
    ///     }
    ///
    ///     for (byte, slots) in src.iter().zip(dst.chunks_mut(2)) {
    ///         slots[0] = hex((*byte >> 4) & 0xf);
    ///         slots[1] = hex(*byte & 0xf);
    ///     }
    /// }
    /// ```
    #[stable(feature = "simd_arch", since = "1.27.0")]
    pub mod arch {
        #[cfg(all(not(dox), target_arch = "x86"))]
        #[stable(feature = "simd_x86", since = "1.27.0")]
        pub use coresimd::arch::x86;

        #[cfg(all(not(dox), target_arch = "x86_64"))]
        #[stable(feature = "simd_x86", since = "1.27.0")]
        pub use coresimd::arch::x86_64;

        #[cfg(all(not(dox), target_arch = "arm"))]
        #[unstable(feature = "stdsimd", issue = "27731")]
        pub use coresimd::arch::arm;

        #[cfg(all(not(dox), target_arch = "aarch64"))]
        #[unstable(feature = "stdsimd", issue = "27731")]
        pub use coresimd::arch::aarch64;

        #[cfg(all(not(dox), target_arch = "mips"))]
        #[unstable(feature = "stdsimd", issue = "27731")]
        pub use coresimd::arch::mips;

        #[cfg(all(not(dox), target_arch = "mips64"))]
        #[unstable(feature = "stdsimd", issue = "27731")]
        pub use coresimd::arch::mips64;

        #[cfg(all(not(dox), target_arch = "powerpc"))]
        #[unstable(feature = "stdsimd", issue = "27731")]
        pub use coresimd::arch::powerpc;

        #[cfg(all(not(dox), target_arch = "powerpc64"))]
        #[unstable(feature = "stdsimd", issue = "27731")]
        pub use coresimd::arch::powerpc64;

        #[cfg(all(not(dox), any(target_arch = "nvptx", target_arch = "nvptx64")))]
        #[unstable(feature = "stdsimd", issue = "27731")]
        pub use coresimd::arch::nvptx;

        #[cfg(all(not(dox), target_arch = "wasm32"))]
        #[unstable(feature = "stdsimd", issue = "27731")]
        pub use coresimd::arch::wasm32;

        #[doc(hidden)] // unstable implementation detail
        #[unstable(feature = "stdsimd", issue = "27731")]
        pub mod detect;

        /// Platform-specific intrinsics for the `x86` platform.
        ///
        /// The documentation with the full listing of `x86` intrinsics is
        /// available in [libcore], but the module is re-exported here in std
        /// as well.
        ///
        /// [libcore]: ../../../core/arch/x86/index.html
        #[cfg(dox)]
        #[doc(cfg(target_arch = "x86"))]
        #[stable(feature = "simd_x86", since = "1.27.0")]
        pub mod x86 {}

        /// Platform-specific intrinsics for the `x86_64` platform.
        ///
        /// The documentation with the full listing of `x86_64` intrinsics is
        /// available in [libcore], but the module is re-exported here in std
        /// as well.
        ///
        /// [libcore]: ../../../core/arch/x86_64/index.html
        #[cfg(dox)]
        #[doc(cfg(target_arch = "x86_64"))]
        #[stable(feature = "simd_x86", since = "1.27.0")]
        pub mod x86_64 {}

        /// Platform-specific intrinsics for the `arm` platform.
        ///
        /// The documentation with the full listing of `arm` intrinsics is
        /// available in [libcore], but the module is re-exported here in std
        /// as well.
        ///
        /// [libcore]: ../../../core/arch/arm/index.html
        #[cfg(dox)]
        #[doc(cfg(target_arch = "arm"))]
        #[unstable(feature = "stdsimd", issue = "27731")]
        pub mod arm {}

        /// Platform-specific intrinsics for the `aarch64` platform.
        ///
        /// The documentation with the full listing of `aarch64` intrinsics is
        /// available in [libcore], but the module is re-exported here in std
        /// as well.
        ///
        /// [libcore]: ../../../core/arch/aarch64/index.html
        #[cfg(dox)]
        #[doc(cfg(target_arch = "aarch64"))]
        #[unstable(feature = "stdsimd", issue = "27731")]
        pub mod aarch64 {}

        /// Platform-specific intrinsics for the `mips` platform.
        ///
        /// The documentation with the full listing of `mips` intrinsics is
        /// available in [libcore], but the module is re-exported here in std
        /// as well.
        ///
        /// [libcore]: ../../../core/arch/mips/index.html
        #[cfg(dox)]
        #[doc(cfg(target_arch = "mips"))]
        #[unstable(feature = "stdsimd", issue = "27731")]
        pub mod mips {}

        /// Platform-specific intrinsics for the `mips64` platform.
        ///
        /// The documentation with the full listing of `mips64` intrinsics is
        /// available in [libcore], but the module is re-exported here in std
        /// as well.
        ///
        /// [libcore]: ../../../core/arch/mips64/index.html
        #[cfg(dox)]
        #[doc(cfg(target_arch = "mips64"))]
        #[unstable(feature = "stdsimd", issue = "27731")]
        pub mod mips64 {}

        /// Platform-specific intrinsics for the `powerpc` platform.
        ///
        /// The documentation with the full listing of `powerpc` intrinsics is
        /// available in [libcore], but the module is re-exported here in std
        /// as well.
        ///
        /// [libcore]: ../../../core/arch/powerpc/index.html
        #[cfg(dox)]
        #[doc(cfg(target_arch = "powerpc"))]
        #[unstable(feature = "stdsimd", issue = "27731")]
        pub mod powerpc {}

        /// Platform-specific intrinsics for the `powerpc64` platform.
        ///
        /// The documentation with the full listing of `powerpc64` intrinsics is
        /// available in [libcore], but the module is re-exported here in std
        /// as well.
        ///
        /// [libcore]: ../../../core/arch/powerpc64/index.html
        #[cfg(dox)]
        #[doc(cfg(target_arch = "powerpc64"))]
        #[unstable(feature = "stdsimd", issue = "27731")]
        pub mod powerpc64 {}

        /// Platform-specific intrinsics for the `nvptx` platform.
        ///
        /// The documentation with the full listing of `nvptx` intrinsics is
        /// available in [libcore], but the module is re-exported here in std
        /// as well.
        ///
        /// [libcore]: ../../../core/arch/nvptx/index.html
        #[cfg(dox)]
        #[doc(cfg(any(target_arch = "nvptx", target_arch = "nvptx64")))]
        #[unstable(feature = "stdsimd", issue = "27731")]
        pub mod nvptx {}

        /// Platform-specific intrinsics for the `wasm32` platform.
        ///
        /// The documentation with the full listing of `wasm32` intrinsics is
        /// available in [libcore], but the module is re-exported here in std
        /// as well.
        ///
        /// [libcore]: ../../../core/arch/wasm32/index.html
        #[cfg(dox)]
        #[doc(cfg(target_arch = "wasm32"))]
        #[unstable(feature = "stdsimd", issue = "27731")]
        pub mod wasm32 {}
    }

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g., `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g., `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g., `str,u8` or `String,struct:Vec,test`)