[llvm-dev] [RFC] Vector Predication (original) (raw)

David Greene via llvm-dev llvm-dev at lists.llvm.org
Thu Feb 7 09:08:51 PST 2019

Jacob Lifshay <programmerjake at gmail.com> writes:

So it would be handy for the vector length on evl intrinsics to be in units of the mask length so we don't have to pattern match a division in the backend. We could have 2 variants of the vector length argument, one in terms of the data vector and one in terms of the mask vector. we could legalize the mask vector variant for those architectures that need it by pulling the multiplication out and switching to the data vector variants.

Would it make sense to have two different intrinsics?

"Normal" form, L is in terms of flat vector length.

<scalable 2 x float> evl.fsub(<scalable 2 x float> %x, <scalable 2 x float> %y, <scalable 2 x i1> %M, i32 %L)

"Sub-vector" form, L is in terms of sub-vectors elements.

<scalable 1 x <2 x float>> evl.fsub(<scalable 1 x <2 x float>> %x, <scalable 1 x <2 x float>> %y, <scalable 1 x <2 x i1>> %M, i32 %L

Overloading types to mean two very different things is confusing to me.

                       -David

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