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dotnet / runtime

.NET is a cross-platform runtime for cloud, mobile, desktop, and IoT apps.
https://docs.microsoft.com/dotnet/core/
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ARM64-SVE: Detect mask usage for Across functions #101973

Open a74nh opened 2 months ago

a74nh commented 2 months ago

ConditionalSelect is used to mask an API. For methods that reduce down to a scalar value (eg all the Across methods), this would be done via:

a = Sve.AddAcross(Sve.ConditionalSelect(mask, a, zero));

Currently this will produce an SEL instruction to select the correct entries. Then will feed this into an ADD that uses an all-true mask.

Instead, the SEL needs merging into the ADD to produce a single ADD instruction using the mask.

See https://github.com/dotnet/runtime/issues/101770 for history.

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kunalspathak commented 2 weeks ago

https://github.com/dotnet/runtime/pull/104640 falls in similar category.