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Vector.ConditionalSelect and Vector128.ConditionalSelect don't emit vpblendvb on x64 #67039

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gfoidl opened this issue Mar 23, 2022 · 3 comments · Fixed by #69509
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Vector.ConditionalSelect and Vector128.ConditionalSelect don't emit vpblendvb on x64 #67039

gfoidl opened this issue Mar 23, 2022 · 3 comments · Fixed by #69509
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@dakersnar
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area-System.Runtime.Intrinsics
Milestone
7.0.0

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@gfoidl
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gfoidl commented Mar 23, 2022

Vector.ConditionalSelect emits on x64 with AVX2 supported a series of

vpand
vpandn
vpor

instead of emitting

vpblendvb

only.

The same is for Vector128.ConditionalSelect.

Is this by design or a missed oppurtunity to use available instructions?

See also sharplab and I see the same on .NET 7 Preview 2.
@dotnet-issue-labeler dotnet-issue-labeler bot added the untriaged New issue has not been triaged by the area owner label Mar 23, 2022
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ghost commented Mar 23, 2022

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Issue Details

Vector.ConditionalSelect emits on x64 with AVX2 supported a series of

vpand
vpandn
vpor

instead of emitting

vpblendvb

only.

The same is for Vector128.ConditionalSelect.

Is this by design or a missed oppurtunity to use available instructions?

See also sharplab and I see the same on .NET 7 Preview 2.

Author: gfoidl
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Labels:

area-System.Runtime.Intrinsics, untriaged
Milestone: -

@gfoidl gfoidl mentioned this issue Mar 23, 2022
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@tannergooding
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ConditionalSelect is "bitwise" and so optimizing it to be blend requires an additional JIT optimization that's not been implemented yet (it has to know the mask comes from something like a Compare).

That optimization is planned, its just not been done yet.

@tannergooding tannergooding removed the untriaged New issue has not been triaged by the area owner label Mar 23, 2022
@tannergooding tannergooding added this to the 7.0.0 milestone Mar 23, 2022
@rzikm rzikm mentioned this issue May 3, 2022
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@dakersnar dakersnar self-assigned this May 9, 2022
@dakersnar dakersnar mentioned this issue May 18, 2022
Merged
@ghost ghost added the in-pr There is an active PR which will close this issue when it is merged label May 18, 2022
@gfoidl gfoidl mentioned this issue May 22, 2022
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@ghost ghost removed the in-pr There is an active PR which will close this issue when it is merged label May 25, 2022
@ghost ghost locked as resolved and limited conversation to collaborators Jun 24, 2022
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@dakersnar dakersnar

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Implement vpblendvb optimization in the JIT dakersnar/runtime
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@vcsjones @gfoidl @tannergooding @dakersnar