Sign extension issue #4
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jethrogb
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Jun 8, 2020
jethrogb
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Jun 8, 2020
jethrogb
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Jun 8, 2020
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Please add some tests that cover the changes you made |
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https://doc.rust-lang.org/beta/src/core/up/stdarch/crates/core_arch/src/x86/sse2.rs.html#1377-1379 pub unsafe fn _mm_extract_epi16(a: __m128i, imm8: i32) -> i32 { simd_extract::<_, i16>(a.as_i16x8(), (imm8 & 7) as u32) as i32 } It extracts as i16 and then converts i16 to i32... which does sign extension. Which means we cannot use the function directly - we need to cast to u16 first then to u32 - otherwise we get 0xffffffff instead of 0xffff
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Function from: https://doc.rust-lang.org/beta/src/core/up/stdarch/crates/core_arch/src/x86/sse2.rs.html#1377-1379
Extracts as i16 and then converts i16 to i32... which does sign extension - instead of getting 0xffff we get 0xffffffff
This is contrary to intel documentation:
https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_mm_extract_epi16&expand=2426