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[DAGCombiner] fold insert_subvector of insert_subvector
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Authored by spatel on Fri, Jan 11, 8:46 AM.

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Summary

This pattern:

  t33: v8i32 = insert_subvector undef:v8i32, t35, Constant:i64<0>
t21: v16i32 = insert_subvector undef:v16i32, t33, Constant:i64<0>

...shows up in PR33758:
https://bugs.llvm.org/show_bug.cgi?id=33758
...although it doesn't make any difference to the final result.

In the affected tests here, it looks like it just makes RA wiggle. But we might as well squash this to prevent it interfering with other pattern-matching. I think there's a similar opportunity for extract-of-extract.

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rL LLVM

Event Timeline

spatel created this revision.Fri, Jan 11, 8:46 AM
RKSimon accepted this revision.Fri, Jan 11, 8:58 AM

LGTM

This revision is now accepted and ready to land.Fri, Jan 11, 8:58 AM
This revision was automatically updated to reflect the committed changes.