user0/rust
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

fix big-endian bitmasks smaller than a byte

Browse source
This commit is contained in:
Ralf Jung 2022-03-17 10:42:39 -04:00
parent 50fbfa4eba
commit 60555b57f1
2 changed files with 23 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

20
crates/core_simd/src/masks/full_masks.rs
View file

@ -68,14 +68,26 @@ where
// Used for bitmask bit order workaround
pub(crate) trait ReverseBits {
fn reverse_bits(self) -> Self;
// Reverse the least significant `n` bits of `self`.
// (Remaining bits must be 0.)
fn reverse_bits(self, n: usize) -> Self;
}
macro_rules! impl_reverse_bits {
{ $($int:ty),* } => {
$(
impl ReverseBits for $int {
fn reverse_bits(self) -> Self { <$int>::reverse_bits(self) }
#[inline(always)]
fn reverse_bits(self, n: usize) -> Self {
let rev = <$int>::reverse_bits(self);
let bitsize = core::mem::size_of::<$int>() * 8;
if n < bitsize {
// Shift things back to the right
rev >> (bitsize - n)
} else {
rev
}
}
}
)*
}
@ -137,7 +149,7 @@ where
// LLVM assumes bit order should match endianness
if cfg!(target_endian = "big") {
bitmask.reverse_bits()
bitmask.reverse_bits(LANES)
} else {
bitmask
}
@ -150,7 +162,7 @@ where
{
// LLVM assumes bit order should match endianness
let bitmask = if cfg!(target_endian = "big") {
bitmask.reverse_bits()
bitmask.reverse_bits(LANES)
} else {
bitmask
};

7
crates/core_simd/tests/masks.rs
View file

@ -84,6 +84,7 @@ macro_rules! test_mask_api {
#[test]
fn roundtrip_bitmask_conversion_short() {
use core_simd::ToBitMask;
let values = [
false, false, false, true,
];
@ -91,6 +92,12 @@ macro_rules! test_mask_api {
let bitmask = mask.to_bitmask();
assert_eq!(bitmask, 0b1000);
assert_eq!(core_simd::Mask::<$type, 4>::from_bitmask(bitmask), mask);
let values = [true, false];
let mask = core_simd::Mask::<$type, 2>::from_array(values);
let bitmask = mask.to_bitmask();
assert_eq!(bitmask, 0b01);
assert_eq!(core_simd::Mask::<$type, 2>::from_bitmask(bitmask), mask);
}
}
}