[PATCH] D34571: [DAGCombine] Improve handling of insert_subvector of bitcast values

[Nirav Dave via Phabricator via llvm-commits]

niravd added a comment.

It turns out generating the failing case for this nontrivial as it looks like we canot irectly build a insertsubvector /extract subvector node.

The peephole of note is along the lines of:

insertsubvector (insertsubvector undef (extractsubvector (bitcast x) 0) 0) (extract subvector (bitcast x) (subvectorsize)) subvectorsize

becoming :

(bitcast x)

Rather than push on this here, I'm going to flip the dependence with https://reviews.llvm.org/D34559 which will now have a small degradation that this patch will fix.


https://reviews.llvm.org/D34571