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305 points todsacerdoti | 1 comments | 22 May 25 11:59 UTC | HN request time: 0.202s | source

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robertknight ◴[22 May 25 12:12 UTC] No.44061261[source]▶

Good post! The inefficient code for comparing pairs of 16-bit integers was an interesting find.

ohr ◴[22 May 25 12:22 UTC] No.44061353[source]▶

Thanks! Would be interesting to see if Rust/LLVM folks can get the compiler to apply this optimization whenever possible, as Rust can be much more accurate w.r.t memory initialization.

replies(3): >>44061438 #>>44061766 #>>44062908 #

1. adgjlsfhk1 ◴[22 May 25 13:17 UTC] No.44061766[source]▶

>>44061353 #

I think rust may be able to get it by adding a `freeze` intrinsic to the codegen here. that would force LLVM to pick a deterministic value if there was poison, and should thus unblock the optimization (which is fine here because we know the value isn't poison)

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Improving performance of rav1d video decoder