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SIMD comparison operators are always signed. #21719

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eddyb opened this issue Jan 28, 2015 · 0 comments · Fixed by #21720
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SIMD comparison operators are always signed. #21719

eddyb opened this issue Jan 28, 2015 · 0 comments · Fixed by #21720
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A-codegen Area: Code generation

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eddyb commented Jan 28, 2015

The compiler always emits signed SIMD comparison instructions, even for unsigned element types:

use std::simd::u32x4;
u32x4(1, 2, 3, 1 << 31) < u32x4(2, 3, 4, 0)
// => u32x4(4294967295, 4294967295, 4294967295, 4294967295)
// i.e. <true, true, true, true>. expected <true, true, true, false>
@eddyb eddyb added I-wrong A-codegen Area: Code generation labels Jan 28, 2015
@huonw huonw self-assigned this Jan 28, 2015
@huonw huonw mentioned this issue Jan 28, 2015
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huonw added a commit to huonw/rust that referenced this issue Jan 28, 2015
@huonw
Use unsigned comparison operators for unsigned SIMD types.
76d66ba 
Previously comparisons of SIMD types were always signed, even unsigned
comparisons, meaning 0xFFFF_FFFF_u32 < 0 inside a SIMD vector.

Fixes rust-lang#21719.
alexcrichton added a commit to alexcrichton/rust that referenced this issue Jan 30, 2015
@alexcrichton
rollup merge of rust-lang#21720: huonw/simd-cmp
c0705c1 
Previously comparisons of SIMD types were always signed, even unsigned
comparisons, meaning 0xFFFF_FFFF_u32 < 0 inside a SIMD vector.

Fixes rust-lang#21719.
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Use unsigned comparison operators for unsigned SIMD types. huonw/rust
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