Fix "simd_support" feature #1056
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This is necessary, because support for `__m64` was removed from nighly Rust [1]. Fixes rust-random#1050. [1] rust-lang/stdarch#823
The specialized instructions are already available with `sse2`.
| #[cfg(not(target_feature = "sse4.2"))] | ||
| #[cfg(not(target_feature = "sse2"))] | ||
| wmul_impl! { (u16x8, u32x8),, 16 } |
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IIUC this is a 256-bit op and thus requires AVX?
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I think packed_simd provides a fallback implementation?
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Does it?
Can you at least clarify on what basis you decided to make this change?
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without 128-bit XMM multiplications, packed_simd falls back to a scalar implementation.
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In that case, why do we bother with these cfg selectors at all?
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I think it is to provide a specialized implementation that uses less instructions.
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So you're saying the use of a SSE4.2 target originally was a mistake?
Maybe it was, since the insrtuctions appear to be supported on SSE2: https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_mm_mullo_epi16&expand=3967,3990
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I appears to be a mistake. I guess that was my bad
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Assuming @dhardy is satisfied, I'm going ahead and merge this. |
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