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[GlobalISel]: Fix lowering of G_Shuffle_vector where we pick up the wrong source index
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Authored by aditya_nandakumar on Tue, Aug 13, 3:44 PM.

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Summary

<3 x s32> a = {1, 2, 3}
<3 x s32> b = {4, 5,6}
<2 x s32> c = G_SHUFFLE_VECTOR a, b, shufflemask(2,1)
produces
BUILD_VECTOR {4, 2}
but should produce
BUILD_VECTOR {3, 2}

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Repository
rL LLVM

Event Timeline

arsenm accepted this revision.Tue, Aug 13, 4:35 PM

LGTM, although I copied this from the DAG lowering, which does seem to use the result number of elements?

This revision is now accepted and ready to land.Tue, Aug 13, 4:35 PM

Committed in 368781.
I haven't had a chance to look into the DAG's implementation yet but our out of tree bots caught this.