The basic idea to this is that a) having a single canonical type makes CSE easier, and b) many of our transforms are inconsistent about which types we end up with based on visit order.
I'm restricting this to constants as for non-constants, we'd have to decide whether the simplicity was worth extra instructions. For constants, there are no extra instructions.
We chose the canonical type as i64 arbitrarily. We might consider changing this to something else in the future if we have cause.
Differential Revision: https://reviews.llvm.org/D115387
If the vector is a splat of some scalar value, findScalarElement()
can simply return the scalar value if it knows the requested lane
is in the vector.
This is only needed for scalable vectors, because the InsertElement/ShuffleVector
case is already handled explicitly for the fixed-width case.
This helps to recognize an InstCombine fold like:
extractelt(bitcast(splat(%v))) -> bitcast(%v)
Reviewed By: spatel
Differential Revision: https://reviews.llvm.org/D107254
I have updated cheapToScalarize to also consider the case when
extracting lanes from a stepvector intrinsic. This required removing
the existing 'bool IsConstantExtractIndex' and passing in the actual
index as a Value instead. We do this because we need to know if the
index is <= known minimum number of elements returned by the stepvector
intrinsic. Effectively, when extracting lane X from a stepvector we
know the value returned is also X.
New tests added here:
Transforms/InstCombine/vscale_extractelement.ll
Differential Revision: https://reviews.llvm.org/D106358
This patch allows folding stepvector + extract to the lane when the lane is
lower than the minimum size of the scalable vector. This fold is possible
because lane X of a stepvector is also X!
For instance, extracting element 3 of a <vscale x 4 x i64>stepvector is 3.
Differential Revision: https://reviews.llvm.org/D103153
This patch allows that scalable vector can also use the fold that already
exists for fixed vector, only when the lane index is lower than the minimum
number of elements of the vector.
Differential Revision: https://reviews.llvm.org/D102404
Summary:
This patch fix the following issues with visitExtractElementInst:
1. Restrict VectorUtils::findScalarElement to fixed-length vector.
For scalable type, the number of elements in shuffle mask is
unknown at compile-time.
2. Fix out-of-range calculation for fixed-length vector.
3. Skip scalable type when analysis rely on fixed number of elements.
4. Add unit tests to check functionality of extractelement for scalable type.
Reviewers: sdesmalen, efriedma, spatel, nikic
Reviewed By: efriedma
Subscribers: tschuett, hiraditya, rkruppe, psnobl, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78267
