Use intrinsics for Mask::{to,from}_array #189
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This version should work except that I believe it requires |
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This significantly simplifies codegen and should improve mask perf. Co-authored-by: Jacob Lifshay <[email protected]>
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| // false: 0b_0000_0000 | ||
| // Thus, an array of bools is also a valid array of bytes: [u8; N] | ||
| // This would be hypothetically valid as an "in-place" transmute, | ||
| // but these are "dependently-sized" types, so copy elision it is! |
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transmute_copy doesn't check if the input and output types have the same size.
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yup, but we know they're the same size since the input type is [bool; LANES] and the output type is [u8; LANES] and Rust guarantees that bool is a single byte.
| let bools: Simd<i8, LANES> = | ||
| intrinsics::simd_ne(Simd::from_array(bytes), Simd::splat(0u8)); |
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Why is this necessary? Can't this be just Simd::from_array(bytes)?
Edit: is it because this needs -1 for true instead of 1?
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Exactly. It could also be simd_neg, come to think of it.
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simd_ne is best because llvm knows the result is supposed to be a mask, with neg llvm doesn't know that, so will likely optimize more poorly
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Now that rust-lang/rust#92425 is merged, that should allow this to land. Just have to wait for nightly to roll over. |
This significantly simplifies codegen and should improve mask perf.
Thanks to @programmerjake for the example for
from_array!This fixes #184.