Tried to convert some SSE4.1 code to SSE2 by adjusting rounding modes and discovered some sadness:https://github.com/rust-lang/rust/issues/72252 …
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Replying to @stephentyrone @pcwalton
I was surprised to discover this in some C++ code in clang recently. Is no one setting the rounding mode? I had assumed this was a somewhat common thing to do.
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It’s an extremely niche operation in practice. Rounding should never have been implemented via thread-local mode; it should be per-operation static (I say this with the benefit of 35 years of hindsight, mind you).
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Replying to @stephentyrone @rbrown46
In my case it was only needed for SSE2 compatibility. I ended up just using the SSE4.1 rounding instruction, which compiled to a dynamic function call. Not great but it’s like 2% in profiles so whatever.
10:00 AM - 16 May 2020
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